energies
Article
Study of the Relationship between the Level of Lubricating Oil
Contamination with Distillation Fuel and the Risk of Explosion
in the Crankcase of a Marine Trunk Type Engine
Leszek Chybowski
Department of Machine Construction and Materials, Faculty of Marine Engineering, Maritime University of
Szczecin, ul. Willowa 2, 71-650 Szczecin, Poland; l.chybowski@pm.szczecin.pl; Tel.: +48-91-48-09-412
Citation: Chybowski, L. Study of the
Abstract: Fuel contamination of engine lubricating oil has been previously determined to arise from
two independent phenomena: the effect on oil flash point, and the effect of changing lubrication
conditions on tribological pairs. This paper combines these effects and holistically analyzes the
consequences of fuel in the lubricating oil of a trunk piston engine on the risk of crankcase explosion.
The author hypothesized that diesel fuel as an oil contaminant increases the risk of an explosion
in the crankcase of an engine due to the independent interaction of two factors: (1) changes in
the oil’s combustible properties, and (2) deterioration of the lubrication conditions of the engine’s
tribological nodes, such as main bearings, piston pins, or crank bearings. An experiment was
performed to evaluate the rheological, ignition, and lubrication properties of two oils (SAE 30 and
SAE 40) commonly used for the recirculation lubrication of marine trunk piston engines for different
levels of diesel contamination. The hypothesis was partially confirmed, and the results show that
contamination of the lubricating oil with diesel fuel in an amount of no more than 10% does not
significantly affect the risk of explosion in the crankcase. However, diesel concentrations above
10% call for corrective action because the viscosity index, lubricity, coefficient of friction and oil film
resistance change significantly. Deterioration of the tribological conditions of the engine bearings, as
seen in the change in viscosity, viscosity index, and lubricity of the oil, causes an increase in bearing
temperature and the possibility of hot spots leading to crankcase explosion.
Relationship between the Level of
Lubricating Oil Contamination with
Distillation Fuel and the Risk of
Keywords: trunk type engine; crankcase explosion; lubricating oil properties; oil dilution with
distillation fuel; lubricity; flash point temperature
Explosion in the Crankcase of a
Marine Trunk Type Engine. Energies
2023, 16, 683. https://doi.org/
10.3390/en16020683
Academic Editors: Haifeng Liu and
Zongyu Yue
Received: 25 November 2022
Revised: 27 December 2022
Accepted: 4 January 2023
Published: 6 January 2023
Copyright:
© 2023 by the author.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
1. Introduction
1.1. Genesis of Undertaking the Research Topic
There have been many research papers report analyses on the mechanism of detonation in vapor cloud explosions [1–3]. Crankcase explosions still occur across many
marine internal combustion engine types (two- and four-stroke; slow, medium, and fast
speed; single and dual fuel) [4–6]. Such explosions damage the engine and its immediate
surroundings [7,8], and often cause serious injury and death to crew members [4,6,9].
By virtue of their design, trunk piston engines are prone to hot gas and fuel blowthroughs from the combustion chamber into the crankcase when piston rings, pistons, and
cylinder liners malfunction or are damaged [10]. The pistons and sealing rings separate the
crankcase from the combustion chamber [11,12]. Hot gas blow-through into the crankcase
can cause increased oil evaporation or ignition [13–15].
An explosion can also be caused by diesel oil entering the crankcase through a cracked
piston bottom (crown). The risk is exacerbated by the possibility of fuel entering the
crankcase, e.g., from a malfunctioning injection apparatus [16–18]. Explosion in the
crankcase of trunk piston engines is also associated with increased temperatures outside the engine [19], i.e., due to a nearby fire or maintenance work performed in violation
Energies 2023, 16, 683. https://doi.org/10.3390/en16020683
https://www.mdpi.com/journal/energies
Energies
Energies2023,
2023,16,
16,xxFOR
FORPEER
PEERREVIEW
REVIEW
Energies 2023, 16, 683
22 of
of 41
41
2 of 38
the
theengine
engine[19],
[19],i.e.,
i.e.,due
dueto
toaanearby
nearbyfire
fireor
ormaintenance
maintenancework
workperformed
performedin
inviolation
violationof
of
of
health
and
safety
regulations
(e.g.,
welding
or
grinding)
[4].
Figures
1
and
summarize
health
and
safety
regulations
(e.g.,
welding
or
grinding)
[4].
Figures
1
and
2
health and safety regulations (e.g., welding or grinding) [4]. Figures 1 and 2 summarize
the
the
most
important
locations
responsible
for
crankcase
explosions
for
in-line
cylinder
and
themost
mostimportant
importantlocations
locationsresponsible
responsiblefor
forcrankcase
crankcaseexplosions
explosionsfor
forin-line
in-linecylinder
cylinderand
and
V-shaped
cylinder
arrangement
engines,
respectively
[11].
V-shaped
V-shapedcylinder
cylinderarrangement
arrangementengines,
engines,respectively
respectively[11].
[11].
1.1.Components
Components
of
an
inline
trunk
type
engine
and
surroundings
that
cause
an
Figure
trunk
type
engine
and
itsits
surroundings
that
cancan
cause
an explosion
Figure1.
Componentsof
ofan
aninline
inline
trunk
type
engine
and
its
surroundings
that
can
cause
anexploexplosion
the
piston,
piston
rings;
2—gudgeon
pin
3—crank
in
thein
crankcase
[11]: [11]:
1—cylinder
liner,liner,
piston,
piston
rings;
2—gudgeon
pin bearing;
3—crank
pin
sion
in
thecrankcase
crankcase
[11]:1—cylinder
1—cylinder
liner,
piston,
piston
rings;
2—gudgeon
pinbearing;
bearing;
3—crank
pin
4—main
bearing;
5—engine
environment.
bearing;
4—main
bearing;
5—engine
environment.
pinbearing;
bearing;
4—main
bearing;
5—engine
environment.
Figure
Components of
a V-shape trunk
type
engine
and
its
that
cause an
Figure2.
trunk
type
engine
andand
itssurroundings
surroundings
thatcan
can
anexploexploFigure
2.2. Components
Componentsofofa aV-shape
V-shape
trunk
type
engine
its surroundings
thatcause
can cause
an
sion
in
the
crankcase
[11]:
1—cylinder
liner,
piston,
piston
rings;
2—gudgeon
pin
bearing;
3—crank
sion
in
the
crankcase
[11]:
1—cylinder
liner,
piston,
piston
rings;
2—gudgeon
pin
bearing;
3—crank
explosion
in the crankcase
[11]: 1—cylinder
liner, piston, piston rings; 2—gudgeon pin bearing;
pin
pinbearing;
bearing;4—main
4—mainbearing;
bearing;5—engine
5—engineenvironment.
environment.
3—crank pin bearing; 4—main bearing; 5—engine environment.
Energies 2023, 16, 683
3 of 38
Regulations require that marine engines be equipped with appropriate instrumentation to monitor crankcase conditions (e.g., oil mist detectors and/or crank-piston cartridge
bearing thermometers) and/or gas sensors and explosion valves [20–23]. The conditions
for the formation of crankcase explosion (CCE) have been discussed in detail in a number
of publications [24–26].
Fuel has a lower flash point than lubricating oil (minimum 60 ◦ C), and its presence
could theoretically contribute to a crankcase explosion that would not have occurred
otherwise. Other authors have pointed out that fuel in oil is among the factors increasing
the risk of crankcase explosion [27], or indicating that volatility or flash point (FP) of
lubricating oil differentiates the category of liquid-fuels two-phase explosions [28]. For
safety, the circulation oil is subjected to periodic laboratory measurement of its viscosity
and flash point [11]. In practice, a 2–5% fuel dilution is considered excessive and calls for
immediate maintenance [29]. The causes of lubricating oil contamination with fuel and
recommended corrective actions are shown in Appendix A Table A1 [30].
The present article is a critical response to the publication “Guideline on the relevance of lubrication flash point in connection with crankcase explosions” published by
CIMAC (the International Council on Combustion Engines) Working Group 8 “Marine
Lubricants” [31]. Among its conclusions is the statement: “Flash point testing of lubricating
oils as an accurate or early indicator of the potential risk of a crankcase explosion has not
been proven and so it is no longer recommended for this purpose”. Since CIMAC is a
generally recognized organization with a high opinion-forming influence, the author of
this article undertook to verify the publication’s statements. The purpose of this investigation was to settle the dispute among experts regarding the effect of fuel contamination of
engine-circulating oil on the risk of crankcase explosion.
The CIMAC publication [31] presents the following information in a concise way:
•
•
•
•
•
•
main conditions required for crankcase explosion;
methods of crankcase explosion risk detection;
methods of crankcase explosion prevention and minimizing the effects;
list of rules, standards, and regulations;
description of secondary explosion phenomena;
analysis of lubricant flash point as a reliable indicator for the risk of crankcase explosion.
The CIMAC publication’s conclusions [31] were drawn based on investigations conducted by its authors, but no source documents were identified. It states that “fuel contamination of lubricating oil has not been detected or reported in any of the reported cases of
crankcase explosions occurring in recent years”. This observation is debatable. That the
authors did not record such a situation in their reports does not invalidate the possibility.
Often, the detailed and exact causes of explosions are not fully known or are not always
disseminated to the public.
The publication [31] further states: “the latest research results also demonstrate that
fuel-contaminated oil does not increase the risk of a crankcase explosion” and “as such
flash point measurement of a lubricating oil is not a reliable or an early indicator for
detecting the risk of a crankcase explosion, neither is it deemed to be a suitable test
whose results can be depended on for this purpose”. These conclusions were presented
in a declarative manner without citing sources. Such statements are debatable because
contamination of the circulating lubricating oil with fuel can change its ignition temperature
and ignition index [31–33]. Contamination also can change the oil’s rheological properties,
thus contributing to a deterioration of lubrication conditions for engine bearings, their
accelerated wear, and subsequent seizure (formation of hot spots).
1.2. Dilution of Lubricating Oil with Fuel and Explosion Hazard
Experience shows that dilution of lubricating oil with fuel is detrimental to the engine,
and its effects include deterioration of engine efficiency, shortening of oil life, and reduction
in engine reliability and safety [29,30,34]. Diesel fuel has a much lower viscosity than
oil; therefore, distillate fuel contamination reduces oil viscosity [35,36]. This viscosity
Energies 2023, 16, 683
4 of 38
reduction reduces both the oil’s lubricating effectiveness and the strength of the oil film,
which increases the wear on the cylinder liner and bearings [30,34,37]. Progressive dilution
of oil with fuel can lead to significant wear and tear and ultimately to engine failure.
The literature describes other problems that result from lower oil viscosity (or degraded oil in general), including reducing the effectiveness of oil additives, increasing oil
volatility, and increasing the rate of oil oxidation [28,30,38,39]. Deterioration of lubricating
oil properties in turn forces more frequent oil changes and increases engine-operating
costs [40,41].
The main cause of fuel leakage from the combustion chambers into the crankcase is
blow-through, which is related to the deterioration of piston rings, pistons, and cylinder
liners [34]. Fuel that penetrates the cylinder liner into the crankcase intensifies wear of
the piston–ring–liner tribological node, which can lead to piston seizure. The temperature
increase resulting from this process can be sufficient to initiate an explosion (hot spot) [37].
Seizure between two components, e.g., piston and cylinder liner, is the result of insufficient
lubrication (oil contamination, lack of oil, inadequate oil lubricity) or exceeding permissible
loads (deformation of cooperating components, excessive pressure force) [42–44].
The subject of the effect of oil ignition temperature on the formation of crankcase
explosions was taken up as early as the middle of the last century, by Ferguson, in a publication summarizing his paper at the Oil and Gas Power Conference (held in Dallas, TX,
USA in 1951) [45]. The study was prompted by a preliminary analysis of 104 crankcase explosions in various engine types occurring in the 10 years preceding publication. Ferguson
summarized prior studies of the mechanism of explosion formation and investigated the
inflammation properties of various oils employed for diesel engine lubrication. Ferguson
stated that “no significant differences were found in the minimum ignition temperature of a
wide variety of lubricating oils, even where diluted with up to 20 per cent diesel fuel”. The
ignition temperature was determined using a test bench, the crankcase explosion apparatus
(CEA), which simulated oil mist conditions in the crankcase. These temperatures were significantly higher than the autogenous ignition temperature determined according to ASTM
guidelines and the flash point temperature. The flash point ranged from 1400–1600 ◦ F
(760–871 ◦ C), depending on the measurement conditions. Ferguson compared the CEA
results obtained with autoignition temperature and flash point temperature and found
the latter to be significantly lower. Figure 3 shows the autoignition temperatures as a
function of flash point temperature for oil diluted with diesel fuel. It shows that the Celsius
autoignition temperature determined under laboratory conditions is about half that of the
CEA ignition temperature. Ferguson explained this fact through the influence of ignitor
size, inflammable mixture inlet temperature, and air flow during the test. According to his
observations, the ignition temperature in the CEA decreased with:
•
•
•
decreasing air velocity;
increasing the temperature of the flammable mixture;
increasing the size of the ignitor.
Ferguson argued that by intensifying these factors, the ignition temperature in CEA
would tend toward the value established under laboratory conditions. It is not clear how
the above statement provided him with the basis for his conclusion that “normal fuel
dilution will have no significant effect on crankcase explosions” [31]. Nevertheless, he
also pointed out that a detailed analysis of the effect of lubricating oil dilution with fuel
and details of the mechanism of explosion formation in the crankcase required further
research. The large difference between the resulting CEA and ASTM autogenous ignition
temperatures depends largely on the specifics of how the test was conducted, including a
realistic atomization of the oil (Ferguson used large droplets).
The inadequacy of Ferguson’s physical model can be demonstrated by analyzing
crankcase oil flammability results presented in Freestone et al. [46], which were published
five years later. They showed the occurrence of two areas of flammability in the range of
270–350 ◦ C and above 400 ◦ C. The authors of the paper [46] write: “It is significant that
with all surfaces ignition was possible at a temperature as low as 270 deg. C (518 deg. F)
Energies 2023, 16, 683
5 of 38
and in one instance at 265 deg. C (509 deg. F). Therefore, to ensure complete safety, a
5 of 41
detecting system should give warning before a temperature of 265 deg. C (509 deg. F) is
reached by an overheated part.”
Energies 2023, 16, x FOR PEER REVIEW
Figure
Dependenceof
ofautoignition
autoignition temperature
onon
flash
point
temperature
for engine
lubricating
Figure
3. 3.
Dependence
temperature
flash
point
temperature
for engine
lubricating
oils diluted with diesel fuel in the Ferguson experiment (own work prepared on the basis of [45]);
oilsblue
diluted
with
diesel
fuel
in
the
Ferguson
experiment
(own
work
prepared
on
the
basis
of [45]);
dotted line is the trend line described by the function y = f(x).
blue dotted line is the trend line described by the function y = f(x).
Ferguson argued that by intensifying these factors, the ignition temperature in CEA
Further
into
the established
possible causes
consequences
ofItcrankcase
would
tendinsights
toward the
value
under and
laboratory
conditions.
is not clearexplosions
how
arethe
pointed
out
in
guides
for
marine
engine
operators,
such
as
“Diesel
Engine Maintenance
above statement provided him with the basis for his conclusion that “normal
fuel diTraining
Manual”
issued
by theeffect
German
Bureau explosions”
of Ships, which
states that one
the root
lution will
have no
significant
on crankcase
[31]. Nevertheless,
heof
also
pointed
out that a detailed
analysis
effect of lubricating
oil dilution
causes
of crankcase
explosions
may of
bethe
“overheating
or dilution
of lubewith
oil” fuel
[47].and
details
the mechanism
explosion formation
the crankcase
required
reIn theoflight
of modern of
knowledge,
crankcase in
explosions
are the
result further
of a multi-stage
search.
The
large
difference
between
the
resulting
CEA
and
ASTM
autogenous
ignition
process, which consists of the following steps [11]:
temperatures depends largely on the specifics of how the test was conducted, including a
•
evaporation of oil in contact with a hot spot inside the crankcase;
realistic atomization of the oil (Ferguson used large droplets).
•
condensation
of oilofvapors
in contact
with
cooler
in the crankcase,
resulting in a
The inadequacy
Ferguson’s
physical
model
canareas
be demonstrated
by analyzing
white
oil
mist
with
a
droplet
diameter
of
5–10
µm;
crankcase oil flammability results presented in Freestone et al. [46], which were published
• five
gradual
increase
in the concentration
oftwo
oil areas
mist,ofwhich
increases
until
the
years later.
They showed
the occurrence of
flammability
in the
range
of lower
explosive
limit
is
reached
(47
mg
of
oil
per
1
L
of
air,
though
some
studies
say this
270–350 °C and above 400 °C. The authors of the paper [46] write: “It is significant that
value
50 mg/L
[11,28,48]),
which at
corresponds
to aasweight
concentration
oilF)mist in
with
all surfaces
ignition
was possible
a temperature
low as 270
deg. C (518 of
deg.
and
one
instance
at 265 deg. C (509 deg. F). Therefore, to ensure complete safety, a
theinair
equal
to 13%;
give warning
temperature
of 265 deg. C (509
deg. F) is◦ C and
• detecting
ignitionsystem
of the should
flammable
mixture,before
whichacan
occur at temperatures
of 270–330
◦
◦
reached
by
an
overheated
part.”
above 400 C (according to other sources, 280–400 C [49], and even 200–400 ◦ C [50]).
Further insights into the possible causes and consequences of crankcase explosions
Ferguson used much lower fuel/air ratios of 1.3–5.8%, and the process itself was
are pointed out in guides for marine engine operators, such as “Diesel Engine Maintesimplified
relative
to the issued
sequence
of German
events indicated
above.which
In addition,
heone
noted
nance Training
Manual”
by the
Bureau of Ships,
states that
of that
ignition
did
not
occur
in
an
atmosphere
of
milky
haze,
indicating
significant
differences
the root causes of crankcase explosions may be “overheating or dilution of lube oil” [47].
between
conditions
of his
experiment
and actual
crankcase
Inthe
the light
of modern
knowledge,
crankcase
explosions
are theexplosions.
result of a multi-stage
Further
evidence
can
be
found
by
studying
the
occurrence
of secondary explosions,
process, which consists of the following steps [11]:
which are the result of air from outside entering the crankcase after the primary explosion.
The vacuum created after the primary explosion causes a fresh load of air to be sucked
•
Energies 2023, 16, 683
equal to 13%;
ignition of the flammable mixture, which can occur at temperatures of 270–330 °C
and above 400 °C (according to other sources, 280–400 °C [49], and even 200–400 °C
[50]).
Ferguson used much lower fuel/air ratios of 1.3–5.8%, and the process itself was simplified relative to the sequence of events indicated above. In addition, he noted that igni6 of 38
tion did not occur in an atmosphere of milky haze, indicating significant differences between the conditions of his experiment and actual crankcase explosions.
Further evidence can be found by studying the occurrence of secondary explosions,
which are the result of air from outside entering the crankcase after the primary explosion.
in from
triggering
secondary
explosion,
which
moreinserious in its
Theoutside,
vacuum created
after thea primary
explosion
causes a fresh
loadisofusually
air to be sucked
from outside,
triggering
a secondary
explosion,
which
usually more
serious
in its con-crankshaft of
consequences
than
the primary.
Figure
4 shows
theis failure
of the
high-speed
sequences
than
the2,
primary.
4 shows theby
failure
of the high-speed
the
the main
engine
No.
whichFigure
was followed
an explosion
that crankshaft
injured aofmechanic
officer
main engine No. 2, which was followed by an explosion that injured a mechanic officer
who was at the engine. This observation confirms the fact that explosions can occur in the
who was at the engine. This observation confirms the fact that explosions can occur in the
crankcase
when
oiloilmist
components
at a much
lower temperature
crankcase
when
mistcontacts
contacts components
at a much
lower temperature
than found than found
usingusing
CEA.CEA.
(a)
(b)
Figure 4. CCTV footage showing the explosion of a high-speed trunk piston engine: (a) just before
Figurethe
4. accident;
CCTV footage
showing
the explosion
a high-speed
trunk piston engine: (a) just before
(b) at the time
of the accident
(adapted of
from
[51]).
the accident; (b) at the time of the accident (adapted from [51]).
According to an analysis of the actuality of the topic of explosions in crankcases of
marine
main to
propulsion
engines
in the publication
[4], as
as 61% (60inout
According
an analysis
ofpresented
the actuality
of the topic
ofmany
explosions
crankcases of
of 98 explosions analyzed) of the exploded crankcases were observed in trunk piston enmarine main propulsion engines presented in the publication [4], as many as 61% (60 out of
gines out of all engines. The aforementioned analysis did not capture auxiliary engines
98 explosions
analyzed)
of now
the exploded
were
observed
piston engines
(virtually all
of them are
trunk pistoncrankcases
engines), and
many
explosionsinoftrunk
the main
out ofsinuses
all engines.
did not
capture
auxiliary engines
(virtually
may notThe
haveaforementioned
been reported. On analysis
the other hand,
according
to Rattenbury,
in the
causes
of crankcase
explosions
in four-stroke
enginesofwere
all of years
them1990–2001,
are nowthe
trunk
piston
engines),
and many
explosions
thedamage
main sinuses may
to main
or reported.
crank bearings
damage
to pistons
(47%), and
reasons (14%)
[52].years
Ex- 1990–2001,
not have
been
On(39%),
the other
hand,
according
to other
Rattenbury,
in the
amples of crankcase explosion-related damage to unshielded engines are shown in Figure 5.
the causes of crankcase explosions in four-stroke engines were damage to main or crank
7 of 41
bearings (39%), damage to pistons (47%), and other reasons (14%) [52]. Examples of crankcase
explosion-related damage to unshielded engines are shown in Figure 5.
Energies 2023, 16, x FOR PEER REVIEW
(a)
(b)
Figure
of trunk
pistonpiston
engineengine
after explosion
in crankcases
of trunk piston
engines:
(a) engines:
Figure5.5.Damage
Damage
of trunk
after explosion
in crankcases
of trunk
piston
burned oil mist detector after failure of the engine lubrication system [53]; (b) conrod as found after
(a) burned oil mist detector after failure of the engine lubrication system [53]; (b) conrod as found
explosion caused by failure of piston guide part of Wärtsilä Vasa 32 engine [54].
after explosion caused by failure of piston guide part of Wärtsilä Vasa 32 engine [54].
Each of these cases could potentially be linked to fuel dilution of lubrication oil. Thus,
a quick diagnosis of oil contamination with fuel makes it possible to avoid damage, particularly in the cylinder/ring area, thereby preventing serious and costly engine failures,
and avoiding crankcase explosion [55]. The above fact is pointed out by ship mechanics’
handbooks as one measure to prevent crankcase explosions: “routine test on used L.O. for
viscosity, flash point and contamination” [49].
Energies 2023, 16, 683
7 of 38
Each of these cases could potentially be linked to fuel dilution of lubrication oil.
Thus, a quick diagnosis of oil contamination with fuel makes it possible to avoid damage,
particularly in the cylinder/ring area, thereby preventing serious and costly engine failures,
and avoiding crankcase explosion [55]. The above fact is pointed out by ship mechanics’
handbooks as one measure to prevent crankcase explosions: “routine test on used L.O. for
viscosity, flash point and contamination” [49].
1.3. Methods for Detecting Lubricating Oil Contamination with Fuel
In addition to evaluating lubricating oil contamination with fuel using analysis of oil
properties such as viscosity and flash point, advanced diagnostic methods can be used.
A summary of the main research methods and their advantages and disadvantages is
presented in Appendix A Table A2.
There is a number of methods for analysis of fuel dilution in lubricants, e.g., gas
chromatography (GC) based on ASTM methods D3524, D3525, and D7593 [56], flame
ionization detector (FID), Fourier-transform infrared (FTIR), spectroscopy, and Spectro
Q6000 fuel dilution meter (FDM) using surface acoustic wave (SAW) sensor [14,56].
In the present study, the flash point and viscosity measurements of the lubricating oil
were used. These tests are the simplest and cheapest. Thus, they are most commonly used
in operational practice for marine engine lubricating oils.
2. Materials and Methods
The research procedure related to the implementation of the study in question consisted of a series of stages according to the scheme shown in Figure 6.
Based on the background provided in the introduction, and stemming from the
recommendations presented in the CIMAC publication [31], a hypothesis was established:
Diesel Fuel (DO) contamination of oil increases the risk of crankcase explosion for a
trunk piston engine due to independent influence of two factors:
(1)
(2)
change in the flammable properties of the oil;
deterioration of lubrication conditions of the engine’s tribological nodes.
To test the hypothesis, a detailed literature search was conducted and a set of parameters were selected that may provide information about the change in ignition and
lubricity properties of the lubricating oil. Then, detailed tests were carried out on lubricating oil samples (SAE 30 and SAE 40 grades) diluted with diesel oil at selected present
mass concentrations (0, 1, 2, 5, 10, 20, 50 and 100%). Oils and oil blends of the SAE 30 and
SAE 40 classes were used in the experiment because these oils are used in the circulating
lubrication systems of marine trunk combustion engines of almost all engine manufacturers.
The oils were tested to determine their properties:
•
•
•
rheological properties (kinematic viscosity ν, density ρ, temperature coefficient of
density change ε, dynamic viscosity η, and viscosity index VI were determined);
ignition properties (flash point FP temperature, derived cetane number DCN, calculated cetane index CCI, calculated carbon aromaticity index CCAI, and calculated
ignition index CII were determined);
lubricant properties (the average wear scar diameter WSD during the tribometer test,
the coefficient of friction µ under test conditions, and the parameter describing the
thickness of the oil film under test conditions FILM were determined).
The characteristics of the lubricating oils and diesel fuel used in the experiment, along
with the various measurements methods, are described in the following subsections.
Energies 2023, 16, 683
Energies 2023, 16, x FOR PEER REVIEW
8 of 38
8 of 41
Figure 6. Research
methodology
adoptedin(description
in text).
Figure 6. Research methodology
adopted
(description
text).
Based on the
background provided in the introduction, and stemming from the rec2.1. Tested Diesel and Lubricating
Oils
ommendations presented in the CIMAC publication [31], a hypothesis was established:
The dataset in [57]Diesel
outlines
the key
requirements
of ISOthe
8217:2017
[58] distillation
Fuel (DO)
contamination
of oil increases
risk of crankcase
explosion for a
diesel for marine engines.
The
dataset
shows
the
requirements
for
engine
trunk piston engine due to independent influence of two factors: lubricating oils
according to the viscosity
classification
of oils
as described
(1) change
in the flammable
properties
of the oil; in SAE J300–2021 [59]. The
experiment used diesel fuel that met the requirements of fuels belonging to the DMX
category, as well as some of the most commonly used industrial marine engine lubricating
oils of the SAE 30 and SAE 40 viscosity classes. Orlen Efecta Diesel Bio (designation
CN27102011D) was used in the study [60], whose nominal parameters are shown in
Appendix A Table A3 and in the dataset [57]. Meanwhile, the lubricating oils used in
the study were Agip Cladium 120 SAE 30 CD and Agip Cladium 120 SAE 40 CD [61–63],
the characteristics of which are shown in Appendix A Table A4 and in the dataset [57].
Agip Cladium SAE 30 CD and Agip Cladium SAE 40 CD oils are AGIP-ENI’s high
quality API CD (Series III) grade engine oils for the lubrication of naturally aspirated and
highly charged marine, traction and industrial compression–ignition engines. The additive
Energies 2023, 16, 683
9 of 38
package allows engines to run on inferior fuels (marine and higher sulphur fuels) while
maintaining high engine performance [61,62].
2.2. Density, Viscosity and Viscosity Index of Lubricating Oil
Changing density and viscosity affects both the anti-seize and ignition properties of
lubricating oil. These features will be discussed later in the article.
Density ρ is the ratio of the mass m of a particular substance to the volume V occupied
by that substance under vacuum conditions:
ρ=
m
.
V
(1)
Under operating conditions, oil/fuel is lighter than the same oil/fuel due to the air
displacement acting on it under atmospheric conditions. Such a difference is assumed to be
0.0011 tons/m3 for fuels with a density of 0.800–1.010 tons/m3 .
The reference temperature for conventional lubricating oils and liquid fuels is 15 ◦ C.
The relationship between the density under operating conditions ρt and the density under
reference conditions ρ15 (the information about the value of this density comes from the
laboratory analysis performed) is described by the formula:
ρt ≈ ρ15 − ε · (t − 15),
(2)
where t is the measured temperature of the substance under operating conditions, and ε is
the coefficient of change of density of a substance when it is heated by 1 ◦ C (1 K).
Viscosity is a property of liquids and plastic solids that characterizes their internal
friction resulting from the movement of fluid layers relative to each other during flow.
.
Dynamic viscosity η expresses the ratio of shear stress τF to shear rate γ:
η=
τF
. .
γ
(3)
Kinematic viscosity ν is defined as the ratio of dynamic viscosity η to fluid density ρ:
ν=
η
.
ρ
(4)
Viscosity index is a unitless measure of a fluid’s change in viscosity relative to temperature change. The viscosity index can be calculated using the following formula:

−U ·100,
 LL−
if V I ≤ 100
H
log H −log U
VI =
,
(5)
(
)
log Y

100 + e 0.00715 −1 , if V I > 100
where U is the oil’s kinematic viscosity at 40 ◦ C, Y is the oil’s kinematic viscosity at 100 ◦ C,
and L and H are the viscosities at 40 ◦ C for two hypothetical oils of viscosity indices equal
to 0 and 100, respectively, with the same viscosity at 100 ◦ C as the oil whose viscosity index
is determined. These L and H values are provided in tables in ASTM D2270 standard.
In this experiment, in order to generally evaluate the properties of lubricating oils
contaminated with diesel fuel, density and viscosity tests of lubricating oils with different
diesel content (0%, 1%, 2%, 5%, 10%, 20%, 50% and 100%) were conducted at selected
temperatures (15, 20, 30, 40, 50, 60, 70, 80, 90, 100 ◦ C).
The density of individual samples in this experiment was determined using a DMA
4500 density analyzer (Anton Paar GmbH, Graz, Austria) with an oscillating U-tube
(Figure 7) performing measurements in accordance with PN-EN ISO 12185:2002. The
accuracy of the measurement temperature setting is 0.02 ◦ C, while the accuracy of density
measurement is 5·10−5 g/cm3 .
Energies 2023, 16, 683
diesel content (0%, 1%, 2%, 5%, 10%, 20%, 50% and 100%) were conducted at selected
temperatures (15, 20, 30, 40, 50, 60, 70, 80, 90, 100 °C).
The density of individual samples in this experiment was determined using a DMA
4500 density analyzer (Anton Paar GmbH, Graz, Austria) with an oscillating U-tube (Figure 7) performing measurements in accordance with PN-EN ISO 12185:2002. The accuracy
10 of 38
of the measurement temperature setting is 0.02 °C, while the accuracy of density measurement is 5∙10−5 g/cm3.
Figure7.7.The
TheAnton
AntonPaar
PaarDMA
DMA4500
4500used
usedin
inthe
thestudy
study(photo.
(photo.M.
M.Szmukała).
Szmukała).
Figure
The
kinematic
viscosityof
ofthe
theindividual
individualsamples
samplesin
inthis
thisexperiment
experimentwas
wasdetermined
determined
The
kinematic
Energies
2023,
16, x FOR PEERviscosity
REVIEW
11 of 41
using
a
Cannon-Fenske
Opaque
glass
capillary
viscometer
(Paradise
Scientific
Company
using a Cannon-Fenske Opaque glass capillary viscometer (Paradise Scientific Company
Ltd., Dhaka, Bangladesh) and a TV 2000 viscometric bath (Labovisco bv, Zoetermeer, the
Ltd., Dhaka, Bangladesh) and a TV 2000 viscometric bath (Labovisco bv, Zoetermeer, the
Nederlands); see FigureNederlands);
8.
see Figure 8.
Figure 8. TV 2000 viscometric bath used in the study (Photo. M. Szmukała).
Figure 8. TV 2000 viscometric bath used in the study (Photo. M. Szmukała).
The viscosity measurement kit allows measurements to be taken in accordance with
PN-EN ISO 3104:2004. The accuracy of the measurement temperature setting is 0.01 °C,
while the accuracy of the viscosity measurement is 0.1 mm2/s (data verified based on the
calibration reports of the device).
2.3. Anti-Seizure Properties of Lubricating Oil
Energies 2023, 16, 683
11 of 38
The viscosity measurement kit allows measurements to be taken in accordance with
PN-EN ISO 3104:2004. The accuracy of the measurement temperature setting is 0.01 ◦ C,
while the accuracy of the viscosity measurement is 0.1 mm2 /s (data verified based on
Energies 2023, 16, x FOR PEER REVIEW
12 the
of 41
calibration reports of the device).
2.3. Anti-Seizure Properties of Lubricating Oil
Lubricity is the ability of oil to form a boundary layer through chemical and physical
Lubricity is the ability of oil to form a boundary layer through chemical and physical
adsorptiononon
solids.
The
function
of the
boundary
layer
to reduce
friction
resistance
adsorption
solids.
The
function
of the
boundary
layer
is toisreduce
friction
resistance
and
and
protect
the
cooperating
surfaces
of
the
tribological
pair
from
excessive
wear
gallprotect the cooperating surfaces of the tribological pair from excessive wear and and
galling.
ing.
Lubricity
characterizes
the
behavior
of
a
lubricant
during
boundary
friction;
thereLubricity characterizes the behavior of a lubricant during boundary friction; therefore, it
it is an ensemble
characteristic,
the lubricating
properties
do not depend
isfore,
an ensemble
characteristic,
since thesince
lubricating
properties
do not depend
only on only
the
on
the
characteristics
of
the
oil,
but
also
on
the
cooperating
components
(properties
characteristics of the oil, but also on the cooperating components (properties of structuralof
structuralcontact
materials,
contact
geometry
and
the type performed)
of movement
and The
their
materials,
geometry
and
the type of
movement
andperformed)
their load [64].
load
[64].
The
lubricating
and
anti-wear
properties
of
oils
and
lubricants
are
determined
lubricating and anti-wear properties of oils and lubricants are determined using tribometers,
using tribometers,
selected
kinds of which
characterized
Appendix A Table A5.
selected
kinds of which
are characterized
in are
Appendix
A TableinA5.
In
this
experiment,
in
order
to
evaluate
the
lubricating
and
anti-wearproperties
propertiesofof
In this experiment, in order to evaluate the lubricating and anti-wear
lubricating
oils
contaminated
with
diesel,
lubricating
oils
with
different
diesel
contents
lubricating oils contaminated with diesel, lubricating oils with different diesel contents
(0%,1%,
1%,2%,
2%,5%,
5%,10%,
10%,20%,
20%,50%
50%and
and100%)
100%)were
weretested
testedfor
forlubricity.
lubricity.Measurements
Measurementswere
were
(0%,
madewith
withaahigh
highfrequency
frequencyreciprocating
reciprocatingrig
rig(HFFR)
(HFFR)tribometer
tribometermodel
modelHFFR
HFFRV1.0.3
V1.0.3(PCS
(PCS
made
Instruments,London,
London,
UK)
performing
measurements
in accordance
ASTM
Instruments,
UK)
performing
measurements
in accordance
with with
ASTM
D6079D6079
and
and PN-EN
ISO 12156-1—Figure
The construction
the device
is shown
PN-EN
ISO 12156-1—Figure
9. The9.construction
of theof
device
is shown
in [65].in [65].
Figure9.9.The
ThePCS
PCSHFFR
HFFRV1.0.3
V1.0.3instrument
instrumentused
usedininthe
thestudy
study(photo.
(photo.M.
M.Szmukała).
Szmukała).
Figure
sample
liquid
is placed
intest
thereservoir
test reservoir
°C, according
to ISO
AAsample
of of
thethe
testtest
liquid
is placed
in the
at 60 ◦at
C, 60
according
to ISO [65],
a
[65], a temperature
determined
bath.
fixed
steel
is heldmounted
in a vertically
temperature
determined
by the bath.byA the
fixed
steelA
ball
is held
in aball
vertically
chuck
mounted
and against
forced with
mass against
a horizontally
stationary
plate
and
forced chuck
with mass
a horizontally
installed
stationaryinstalled
steel plate
4 with ansteel
applied
load.
The
ball oscillates
a constant
speed with
a constant
pitch,
while
the interface
4 with
antest
applied
load. Theattest
ball oscillates
at a constant
speed
with
a constant
pitch,
with
thethe
plate
is fullywith
immersed
in is
thefully
fluid.
Oscillation
is provided
by an electromagnetic
while
interface
the plate
immersed
in the
fluid. Oscillation
is provided by
vibrator
along
with
a
counterweight
providing
a
fixed
motion
of
the
ball
determined
an electromagnetic vibrator along with a counterweight providing a fixed motionusing
of the
appropriate
elements.
Theappropriate
sample loadelements.
is monitored
an inverter.
conditions
such
ball determined
using
Thewith
sample
load is Test
monitored
with
an as
inmetallurgical
properties such
of theasplate
and ball, fluid
temperature,
load,and
oscillation
frequency,
verter. Test conditions
metallurgical
properties
of the plate
ball, fluid
temperand
stroke
length
and external
conditions
are specified
the external
norm [65].
The diameter
of wear
ature,
load,
oscillation
frequency,
and stroke
lengthinand
conditions
are specified
scar
WSD-generated
ondiameter
the test ball
is taken
asWSD-generated
a measure of anti-wear
fluid
in the
norm [65]. The
of wear
scar
on the properties
test ball is and
taken
as a
lubricity.
Wear
assessment
is
carried
out
either
visually
or
with
a
digital
camera.
In
addition,
measure of anti-wear properties and fluid lubricity. Wear assessment is carried out either
the
deviceor
used
provides
on the averaged
value
of the
frictioninformation
coefficient µon
and
visually
with
a digitalinformation
camera. In addition,
the device
used
provides
the
the
percentage
reduction
in
oil
film
resistance
(FILM
parameter).
averaged value of the friction coefficient μ and the percentage reduction in oil film reThe FILM
provides a rough assessment of oil film thickness and quality by
sistance
(FILMparameter
parameter).
measuring
the electrical
contact
potential
(ECP),
which is of
a measure
of contactand
resistance
The FILM
parameter
provides
a rough
assessment
oil film thickness
quality
by measuring the electrical contact potential (ECP), which is a measure of contact resistance (oil film resistance). The contact resistance circuit applies a potential of 15 mV to
the sample contact resistor and a series stabilizing resistor. The stabilizing resistance set
by the control software, together with the contact resistor, forms a potential divider circuit.
Energies 2023, 16, 683
12 of 38
(oil film resistance). The contact resistance circuit applies a potential of 15 mV to the sample
and a series stabilizing resistor. The stabilizing resistance set by the control
Energies 2023,contact
16, x FORresistor
PEER REVIEW
13 of 41
software, together with the contact resistor, forms a potential divider circuit. The default
value of the stabilizing resistor is 10 Ω. After the test, the HFFR apparatus provides the
value of the percentage
reduction
film resistance
value.
values
of the
FILMLarge valprovides
the valuein
ofthe
the oil
percentage
reduction
in theLarge
oil film
resistance
value.
parameter indicate
separation
of
the
cooperating
metal
surfaces,
while
values
close
to or while
ues of the FILM parameter indicate separation of the cooperating metal surfaces,
equal to zero indicate
contact
(oil filmofbreakage)
between
thebreakage)
values the
closeexistence
to or equalof
tometallic
zero indicate
the existence
metallic contact
(oil film
mating surfaces. between the mating surfaces.
2.4. Ignition
PropertiesOil
of Lubricating Oil
2.4. Ignition Properties
of Lubricating
The essential
indicators forthe
determining
the ignition characteristics
of liquid
The essential indicators
for determining
ignition characteristics
of liquid fuels
are fuels are
flash point,
autoignition
temperature,
and(ignition)
autoignition
(ignition)
delay. The of
flashpoint
of
flash point, autoignition
temperature,
and
autoignition
delay.
The flashpoint
a
a material
the lowest liquid
temperature
which,standardized
under certain conditions,
standardized condimaterial is the lowest
liquidistemperature
at which,
underatcertain
a liquid gives off vapors in a quantity capable of forming an ignitable vapor/air
a liquid gives offtions,
vapors
in a quantity capable of forming an ignitable vapor/air mixture
mixture (standard EN IEC 60079-10-1). The autoignition temperature or kindling point of
(standard EN IEC 60079-10-1). The autoignition temperature or kindling point of a substance
a substance is the lowest temperature at which it spontaneously ignites in a normal atis the lowest temperature at which it spontaneously ignites in a normal atmosphere without
mosphere without an external source of ignition, such as a flame or spark. The flash point
an external sourceinofthis
ignition,
such as
a flame
or spark.
The flash
pointusing
in this
was method
experiment
was
determined
in a closed
crucible
theexperiment
Pensky–Martens
determined in a closed
crucible
using
the
Pensky–Martens
method
in
accordance
with
EN
in accordance with EN ISO 2719. To carry out the test, the flashpoint Pensky–Martens
ISO 2719. To carrysemi-automatic
out the test, theapparatus
flashpoint
Pensky–Martens
semi-automatic
apparatus
was
was used (Walter Herzog GmbH, Lauda-Königshofen, Gerused (Walter Herzog
GmbH,
Lauda-Königshofen,
Germany); see Figure 10.
many);
see Figure
10.
Figure 10. Flashpoint Pensky–Martens semi-automatic apparatus from Walter Herzog GmbH used
Figure 10. Flashpoint Pensky–Martens semi-automatic apparatus from Walter Herzog GmbH used
in the study (photo. M. Szmukała).
in the study (photo. M. Szmukała).
Energies 2023, 16, 683
13 of 38
The autoignition delay is defined as the time between the atomization of a flammable
substance and the start of the combustion process after autoignition has occurred. This
indicator is usually used for evaluating the diesel engine fuels. There are several methods
for measuring the autoignition properties of fuel [66–68]. Table A6 in Appendix A shows
a comparison of several selected methods for measuring the autoignition properties of
fuel. An indicator of the combustion speed of diesel fuel and compression needed for
ignition is the cetane number (CN; alias cetane rating). For marine fuels, CN values above
45 correspond to very good ignition properties, 40–45 from good to very good, 35–40 from
good to acceptable, 28–35 from bad to acceptable, 25–28 from very bad to bad, while below
25 very bad or unfit for use.
Cetane numbers are difficult to measure accurately, as the method requires a special
diesel engine called a cooperative fuel research (CFR) engine. The test is conducted
in accordance with the guidelines of ASTM D613 (ISO 5165). In order to facilitate the
measurements, substitute methods were introduced:
•
•
constant volume combustion chamber instrument (CVCC) analyzers such as the
ignition quality tester (IQT) according to ASTM D6890, cetane ignition delay (CID)
according to ASTM D7668, or fuel ignition tester (FIT) according to ASTM D7170 for
measuring the derived cetane number (DCN);
laboratory methods for determining flammability indices, cetane indices (CI and CCI),
and others based on the physical and chemical properties of a substance, e.g., “four
variable equations” (ASTM D4737) based on density, 10% 50% and 90% recovery
temperatures or “two variable methods” (ASTM D976), which use just density and
the 50% recovery temperature.
Apart from the indicators determined experimentally, calculated indicators are used
in operational practice. This applies to situations where the measurement of autoignition
delay is hampered by technical capabilities. This situation includes residual fuels such as
heavy fuel oils. Among such indices are the calculated carbon aromaticity index (CCAI)
and the calculated ignition index (CII).
CCAI is Shell’s calculation of the autoignition capability of residual fuels (heavy
fuel oils, HFO). It is calculated based on the measured viscosity ν (mm2 /s) for a given
fuel determined at t (◦ C) and the density at 15 ◦ C ρ15 (kg/m3 ). For residual fuels, CCAI
falling within the range of 790–830 corresponds to excellent to good combustion quality,
830–850 corresponds to good to average combustion quality, 850–870 corresponds to average combustion quality, and 870–950 corresponds to poor or very poor combustion quality.
CCAI can be determined from one of the equivalent formulas:
t + 273
CCAI = ρ15 − 140.7· log[log(ν + 0.85)] − 80.6 − 210· ln
,
(6)
323
t + 273
CCAI = ρ15 − 140.7· log[log(ν + 0.85)] − 80.6 − 483.5· log
.
(7)
323
CII is BP’s calculation of the autoignition capacity of residual fuels (HFO). It is calculated based on the measured viscosity ν (mm2 /s) for a given fuel determined at t (◦ C)
and the density at 15 ◦ C ρ15 (kg/m3 ). The values obtained from the calculation of CII for
residual fuels are interpreted analogously as CN for distillate fuels. CII is determined from
the formula:
CI I = (270.795 + 0.1038·t) − 0.254565·ρ15 + 23.708· log[log(ν + 0.7)].
(8)
In this experiment, to evaluate the ignition properties of lubricating oils contaminated
with diesel fuel, flash point temperature and cetane indices of lubricating oils with different
diesel content (0%, 1%, 2%, 5%, 10%, 20%, 50% and 100%) were tested. Determination of
the derived cetane number (DCN) was not possible for lubricating oil–diesel blends; thus,
only the diesel DCN value was determined. This was done using the Herzog cetane ID
Energies 2023, 16, x FOR PEER REVIEW
Energies 2023, 16, 683
15 of 41
14 of 38
for
of (PAC
fuel and
oilUSA).
is dueThe
to the
specifics
of the measuring
device.
510 mixtures
instrument
L.P.,lubricating
Houston, TX,
inability
to measure
DON for mixtures
Calculation
of
the
cetane
index
was
possible
only
for
mixtures
with
diesel
fuel
content
of fuel and lubricating oil is due to the specifics of the measuring device. Calculation in
of
lubricating
oil equal
or greater
50% m/m.with
Thisdiesel
limitation
was dueinto
the complex
the cetane index
wasto
possible
onlythan
for mixtures
fuel content
lubricating
oil
composition
of lubricating
which
not a pure
of hydrocarbons
(they conequal to or greater
than 50%oils,
m/m.
Thisare
limitation
wasmixture
due to the
complex composition
of
tain
a number
ofwhich
additives).
Since
the mixture
rheological
properties of lubricating
oilsa are
similar
lubricating
oils,
are not
a pure
of hydrocarbons
(they contain
number
of
to
residual Since
fuels, the
the rheological
values of CCAI
and CII
wereoils
determined
measured
additives).
properties
of indices
lubricating
are similarfor
to the
residual
fuels,
values
of
density
and
kinematic
viscosity
of
mixtures
of
the
lubricating
oils
tested
the values of CCAI and CII indices were determined for the measured values of densitywith
and
diesel
fuel.viscosity
The calculated
values
of CII
and CCAI
were
determined
forfuel.
all concentrations
kinematic
of mixtures
of the
lubricating
oils
tested
with diesel
The calculated
planned
the
experiment.
values ofin
CII
and
CCAI were determined for all concentrations planned in the experiment.
3. Results
Results and
and Discussion
3.1. Rheological
Rheological Properties
Properties
3.1.
Figures 11
11 and
and 12
12 show
show the
the measured
measured density
density values
values of
of the
the tested
tested lubricating
lubricating oils
oils of
of
Figures
the
SAE
30
and
SAE
40
grades,
respectively,
with
different
degrees
of
contamination
with
the SAE 30 and SAE 40 grades, respectively, with different degrees of contamination with
diesel fuel:
fuel: 0,
0, 1,
1, 2,
2, 5,
5, 10,
10, 20,
20, and
and 50%
50% m/m;
m/m;compared
comparedwith
withpure
purediesel
diesel(i.e.,
(i.e.,100%).
100%).
diesel
◦ C at
Figure 11. Measured
Measured values
values of
of SAE
SAE 30 class oil density in the temperature range of 15–100 °C
different
levels of
of lubricating
lubricating oil
oil dilution
dilution with
with diesel
diesel fuel.
fuel.
different levels
The density values at a given temperature are similar for oils of both classes. Increased
concentration of diesel in the lubricating oil results in a significant reduction in density.
From these data, the temperature coefficients of change of substance density, ε, were
calculated using Equation (2). The coefficient values were determined for a temperature of
100 ◦ C. Figure 13 shows a summary of the values for different levels of dilution.
The ε values for SAE 30 oil are higher than those for SAE 40 oil. Moreover, the value
of the ε coefficient increases with an increase in the content of diesel fuel in the lubricating
oil. This trend is due to the higher value of this index for diesel fuel than for lubricating oil.
For the oils tested, the difference between diesel and lubricating oil ε values for SAE 30 oil
was 0.084, while for SAE 40 oil, it was 0.089.
Energies 2023, 16, 683
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15 of 38
16 of 41
Energies 2023, 16, x FOR PEER REVIEW
17 of
Figure 12. Measured values of SAE 40 class oil density in the temperature range of 15–100
°C 41
◦at
Figure 12. Measured values of SAE 40 class oil density in the temperature range of 15–100 C at
different levels of lubricating oil dilution with diesel fuel.
different levels of lubricating oil dilution with diesel fuel.
The density values at a given temperature are similar for oils of both classes. Increased concentration of diesel in the lubricating oil results in a significant reduction in
density. From these data, the temperature coefficients of change of substance density, ε,
were calculated using Equation (2). The coefficient values were determined for a temperature of 100 °C. Figure 13 shows a summary of the values for different levels of dilution.
The ε values for SAE 30 oil are higher than those for SAE 40 oil. Moreover, the value
of the ε coefficient increases with an increase in the content of diesel fuel in the lubricating
oil. This trend is due to the higher value of this index for diesel fuel than for lubricating
oil. For the oils tested, the difference between diesel and lubricating oil ε values for SAE
30 oil was 0.084, while for SAE 40 oil, it was 0.089.
Figure13.
13.Calculated
Calculatedvalues
valuesof
ofthe
thecoefficient
coefficientof
oftemperature
temperature change
change in
in density
density of
of the
the lubricating
lubricating oils
Figure
oils
tested
at
different
levels
of
lubricating
oil
dilution
with
diesel
fuel.
tested at different levels of lubricating oil dilution with diesel fuel.
Themeasured
measured kinematic
kinematic viscosity
oil–diesel
blends
for for
different
The
viscosityvalues
valuesofoflubricating
lubricating
oil–diesel
blends
different
concentrations
in
the
temperature
range
of
40–100
°C
for
SAE
30
and
SAE
40
grade
oilsoils
◦
concentrations in the temperature range of 40–100 C for SAE 30 and SAE 40 grade
are shown in Figures 14 and 15, respectively. Their viscosity decreases with increasing
temperature. Increasing the diesel content in the lubricating oil mixture results in a decrease in kinematic viscosity at a given temperature.
Energies 2023, 16, 683
16 of 38
are shown in Figures 14 and 15, respectively. Their viscosity decreases with increasing
temperature. Increasing the diesel content in the lubricating oil mixture results in
aofdecrease
Energies
18
41
Energies 2023,
2023, 16,
16, xx FOR
FOR PEER
PEER REVIEW
REVIEW
18 of
41
in kinematic viscosity at a given temperature.
Figure
Measured
kinematic
values
of
30
oil
range
Figure
14.Measured
Measured kinematic
kinematic viscosity
viscosity
values
of SAE
SAE
30 grade
grade
oil in
in the
the
temperature
range of
of 40–
40–
Figure
14.14.
viscosity
values
of SAE
30 grade
oiltemperature
in the temperature
range of
100
°C
at
different
levels
of
lubricating
oil
dilution
with
diesel
fuel.
◦
100
°C
at
different
levels
of
lubricating
oil
dilution
with
diesel
fuel.
40–100 C at different levels of lubricating oil dilution with diesel fuel.
Figure 15. Measured kinematic viscosity values of SAE 40 grade oil in the temperature range of 40–
Figure
15.Measured
Measured kinematic
kinematic viscosity
values
of SAE
40 grade
oil in the
range of 40–
Figure
15.at
viscosity
values
of SAE
40 grade
oiltemperature
in the temperature
range of
100
100 °C
°C
at different
different levels
levels of
of lubricating
lubricating oil
oil dilution
dilution with
with diesel
diesel fuel.
fuel.
◦
40–100 C at different levels of lubricating oil dilution with diesel fuel.
Energies 2023, 16, 683
Energies
Energies 2023,
2023, 16,
16, xx FOR
FOR PEER
PEER REVIEW
REVIEW
17 of 38
19
19 of
of 41
41
Viscosity of oils belonging to each SAE class must fall within an allowed range at
Viscosity of
of oils
oils belonging
belonging to
to each
each SAE
SAE class
class must
must fall
fall within
within an
an allowed
allowed range
range at
at 100
100
100 ◦ Viscosity
C. Experimental
results show
that
contamination
of the lubricating
oil with
diesel
°C.
Experimental
results
show
that
contamination
of
the
lubricating
oil
with
diesel
fuel
°C. Experimental results show that contamination of the lubricating oil with diesel fuel in
in
fuel in an amount within the range of 5–10% m/m results in the oil not meeting SAE
an
an amount
amount within
within the
the range
range of
of 5–10%
5–10% m/m
m/m results
results in
in the
the oil
oil not
not meeting
meeting SAE
SAE viscosity
viscosity
viscosity
requirements.
requirements.
requirements.
Based
on themeasured
measured valuesofof
kinematic viscosity
and density
of the blends,
dyBased
Based on
on the
the measured values
values of kinematic
kinematic viscosity
viscosity and
and density
density of
of the
the blends,
blends, dydynamic
viscosity
values
were
calculated
for
the
various
lubricating
oil–diesel
blends.
The
namic
namic viscosity
viscosity values
values were
were calculated
calculated for
for the
the various
various lubricating
lubricating oil–diesel
oil–diesel blends.
blends. The
The
results
ofcalculations
calculationsforfor
lubricating
oils
of SAE
30SAE
and40
SAE
40 grades
are shown
in
results
of
lubricating
oils
of
SAE
30
and
grades
are
shown
results of calculations for lubricating oils of SAE 30 and SAE 40 grades are shown in
in FigFigFigures
16
and
17,
respectively.
ures
ures 16
16 and
and 17,
17, respectively.
respectively.
Figure
of
dynamic
viscosity
of
30
range
40–
Figure
16. Measured
Measuredvalues
values
dynamic
viscosity
of SAE
30 oil
class
oil temperature
in
the temperature
Figure 16.
Measured
values
of of
dynamic
viscosity
of SAE
SAE
30 class
class
oil in
in the
the
temperature
range of
ofrange
40– of
◦ Cdifferent
100
levels
of
oil
with
fuel.
100 °C
°C at
at
different
levels
of lubricating
lubricating
oil dilution
dilution
with diesel
diesel
fuel. fuel.
40–100
at different
levels
of lubricating
oil dilution
with diesel
Figure
of
dynamic
viscosity
of
40
range
40–
Figure 17.
Measured
values
of of
dynamic
viscosity
of SAE
SAE
40 class
class
oil in
in the
the
temperature
range of
ofrange
40– of
Figure
17. Measured
Measuredvalues
values
dynamic
viscosity
of SAE
40 oil
class
oil temperature
in
the temperature
100
°C
at
different
levels
of
lubricating
oil
dilution
with
diesel
fuel.
◦
100
°C
at
different
levels
of
lubricating
oil
dilution
with
diesel
fuel.
40–100 C at different levels of lubricating oil dilution with diesel fuel.
Energies 2023, 16, x FOR PEER REVIEW
20 of 41
Energies 2023, 16, 683
18 of 38
Since both density and viscosity decrease with increasing oil temperature, the dy
namic viscosity
value resulting from their product will also decrease with increasing tem
Since both density and viscosity decrease with increasing oil temperature, the dynamic
perature.
Atvalue
the same
time,
the
value
of dynamic
viscositywith
at aincreasing
given temperature
viscosity
resulting
from
their
product
will also decrease
temperature. and the
temperature
viscosity
in a at
given
temperature
range
when the
At the samedrop
time, in
thedynamic
value of dynamic
viscosity
a given
temperature and
thedecrease
temperature
drop
in dynamic
viscosity
in a given
range decrease when the diesel content
diesel
content
of the
lubricating
oils temperature
tested increases.
ofBased
the lubricating
oils testedof
increases.
on the viscosity
the tested oils at 40 °C and 100 °C, viscosity index VI values
Based on the viscosity of the tested oils at 40 ◦ C and 100 ◦ C, viscosity index VI
were calculated. Calculators available on the websites of Olezol [69] and Anton Paar [70
values were calculated. Calculators available on the websites of Olezol [69] and Anton
were
used
the
calculations.
The change
in VI in
values
for different
lubricating
Paar
[70]for
were
used
for the calculations.
The change
VI values
for different
lubricating oil con
taminants
is shownisin
Figure
18. 18.
oil contaminants
shown
in Figure
Figure
18. Calculated
viscosity
index
oilsatatdifferent
different
levels
Figure
18. Calculated
viscosity
indexvalues
valuesof
ofthe
thetested
tested lubricating
lubricating oils
levels
of of lubri
cating
oil dilution
with diesel
fuel.fuel.
lubricating
oil dilution
with diesel
Changes
forSAE
SAE 30
30 and
oiloil
areare
similar.
VI inVI
theindiesel
concentration
Changes
ininVIVIfor
andSAE
SAE4040
similar.
the diesel
concentration
range of 0–10% m/m remains at a similar level in the range of 100–110, gradually increasing
range of 0–10% m/m remains at a similar level in the range of 100–110, gradually increas
the value of the increment as the diesel oil content in the mixture increases. This trend
ing shows
the value
theincreasing
increment
as the
diesel
in the
mixturethe
increases.
that of
with
diesel
content
in oil
thecontent
lubricating
oil mixture,
viscosityThis
of trend
shows
that with
increasing
content
in temperature
the lubricating
oil mixture,
the viscosity
o
the mixture
shows
less and diesel
less variation
with
(the higher
the VI value,
the
decrease
in and
viscosity
a given temperature
increment).
the smaller
mixturetheshows
less
less atvariation
with temperature
(the higher the VI value, the
smaller the decrease in viscosity at a given temperature increment).
3.2. Anti-Seizure Properties of Oil
Figure 19 shows the results of oil lubricity measurements. Here, lubricity is defined
as the wear scar diameter WSD (the average of the major and minor axis of the wear scar)
Figure 19
the as
results
ofofoil
measurements.
Here,diesel
lubricity
is defined
measured
on shows
the test ball
a result
thelubricity
HFFR apparatus
test for different
contents
in the
lubricating
oils tested.
Microscopic
images
of the
wearand
marks
for each
as the
wear
scar diameter
WSD
(the average
of the
major
minor
axisofofthe
thetests
wear scar
performed
measured
on are
thesummarized
test ball asinaAppendix
result of B.
the HFFR apparatus test for different diesel con
3.2. Anti-Seizure Properties of Oil
tents in the lubricating oils tested. Microscopic images of the wear marks for each of the
tests performed are summarized in Appendix B.
Energies
2023,
16,16,
x FOR
Energies
2023,
683 PEER REVIEW
2138of 41
19 of
Figure19.
19.Lubricity
Lubricity of
oilsoils
at different
levelslevels
of lubricating
oil dilution
with diesel
fuel.
Figure
of tested
testedlubricating
lubricating
at different
of lubricating
oil dilution
with
diesel
fuel.
Lubricity values measured for pure oils are in the range of 180–190 µm. The results
show slight fluctuations in the lubricity values in the low diesel concentration range
Lubricity values measured for pure oils are in the range of 180–190 μm. The results
(contamination of the lubricating oil with diesel up to approx. 10% m/m diesel in the
show
slight fluctuations in the lubricity values in the low diesel concentration range (conlubricating oil). For this range, the maximum lubricity variations for the two oils tested are
tamination
ofµm
the(SAE
lubricating
with
diesel
approx.
10%
dieseldiesel
in the
lubricatbetween 141
40, 10% oil
m/m
diesel
oil)up
andto205
µm (SAE
30,m/m
5% m/m
oil).
At
ing
oil).
For
this
range,
the
maximum
lubricity
variations
for
the
two
oils
tested
are bea diesel concentration of ~20% m/m, the greatest decrease in lubricity values is observed
tween
141 μm
40, 10%
m/m
diesel
and 205
μmabout
(SAE50%
30,m/m
5% m/m
diesel
oil).toAt a
(~100–107
µm),(SAE
followed
by an
increase
in oil)
lubricity.
From
diesel
content
diesel
concentration
~20%
m/m,
the greatest
in lubricity
observed
a value
of 100% (pureof
diesel
oil),
the lubricity
value decrease
varies in the
range of ~values
±20 µmisrelative
(~100–107
μm), value
followed
by an
increase
lubricity.
From about 50% m/m diesel content
to the lubricity
for pure
diesel
oil ofin
170
µm.
The
HFFR
used
in
the
experiment
also
provides
information
onthe
oil range
film continuity
to a value of 100% (pure diesel oil), the lubricity value
varies in
of ~±20 μm
(definedtoasthe
thelubricity
percentage
loss of
film diesel
resistance
during
the test, so that 100% corresponds
relative
value
foroilpure
oil of
170 μm.
to full
oilHFFR
film separation
of mating
components),
along with
averagedon
friction
coefficient
The
used in the
experiment
also provides
information
oil film
continuity
values.
These
are
only
auxiliary
indicators
that
can
supplement
the
analysis
(defined as the percentage loss of oil film resistance during the test, so that based
100% on
corremeasured oil lubricity. Figures 20 and 21 show the measurements for these two indicators.
sponds
to full oil film separation of mating components), along with averaged friction
The conducted tests show that in the range of lubricating oil contamination with diesel
coefficient values. These are only auxiliary indicators that can supplement the analysis
fuel in the concentration range of 0–10% m/m, the resistance of the oil film does not change.
based on measured oil lubricity. Figures 20 and 21 show the measurements for these two
Thus, the mating elements in the HFFR apparatus are separated by a layer of lubricant, and
indicators.
there is no metallic contact between elements.
The averaged friction coefficient of mating elements in the HFFR apparatus changed
little for diesel fuel concentration 0–10%. An increase in the friction coefficient was observed
above 10% m/m, followed by a decrease in its value above 50% m/m.
Energies 2023,
2023, 16, x683
Energies
Energies 2023,16,
16, xFOR
FORPEER
PEER REVIEW
REVIEW
20 of 41
38
22
22 of
of 41
Figure
Figure 20.
20. Percentage
resistance of
of the
the lubricating
lubricating oils
oils tested
tested at
at different
different levels
levels of
of
Percentage loss
loss of
of oil
oil film
film resistance
lubricating
oil
dilution
with
diesel
fuel.
diesel fuel.
fuel.
lubricating oil dilution with diesel
Figure
of
friction
of
mating
elements
in
the
HFFR
apparatus
separated
by
Figure 21.
21. Averaged
Averaged coefficient
coefficientof
offriction
frictionof
ofmating
matingelements
elementsin
inthe
theHFFR
HFFRapparatus
apparatusseparated
separated
Figure
21.
Averaged
coefficient
byby
a
aa layer
from
the
tested
lubricating
oils
at
different
levels
of
lubricating
oil
dilution
with
diesel
fuel.
layer
from
the
tested
lubricating
oils
different
levels
lubricating
dilution
with
diesel
fuel.
layer
from
the
tested
lubricating
oils
at at
different
levels
of of
lubricating
oiloil
dilution
with
diesel
fuel.
Energies 2023, 16, 683
The conducted tests show that in the range of lubricating oil contamination with diesel fuel in the concentration range of 0–10% m/m, the resistance of the oil film does not
change. Thus, the mating elements in the HFFR apparatus are separated by a layer of lubricant, and there is no metallic contact between elements.
21 of 38
The averaged friction coefficient of mating elements in the HFFR apparatus changed
little for diesel fuel concentration 0–10%. An increase in the friction coefficient was observed above 10% m/m, followed by a decrease in its value above 50% m/m.
The
coefficient of
of friction,
friction, and
The observed
observed changes
changes in
in lubricity,
lubricity, coefficient
and percentage
percentage loss
loss of
of oil
oil
film resistance with diesel testify to the complexity of the wear process and the difficulty
of objectively
ofof
oils.
TheThe
lubricity
information
obobjectivelydetermining
determiningthe
thelubricating
lubricatingproperties
properties
oils.
lubricity
information
tained
cancan
bebe
used
asas
a coarse
obtained
used
a coarseindicator
indicatorshowing
showingthe
theeffect
effectofoflubricating
lubricatingoil
oilcontaminacontamination. Simultaneous
Simultaneous consideration
consideration of
of the
the aforementioned
aforementioned indices
indices along
along with the viscosity
values of the tested oils shows that their
their lubricating
lubricating (anti-wear) properties deteriorate
with increasing fuel contamination. A detailed determination of the relationship between
these properties and the lubricity value obtained by the HFFR method requires further
detailed research.
3.3. Ignition
Ignition Properties
Properties of
of Oil
Oil
3.3.
Flash point
point temperature
temperatureisisthe
theprimary
primaryindicator
indicatordescribing
describing
the
ignition
properties
Flash
the
ignition
properties
of
of
oils
and
fuels.
Figure
22
shows
the
results
of
measuring
the
flash
point
of
the tested
oils and fuels. Figure 22 shows the results of measuring the flash point of the tested
mixmixtures
oil with
As expected,
the ignition
temperature
the mixture
decreases
tures
of oilofwith
DO. DO.
As expected,
the ignition
temperature
of theofmixture
decreases
with
with
an
increase
in
the
diesel
content
of
the
lubricating
oil.
an increase in the diesel content of the lubricating oil.
Figure
Figure 22.
22. Flash
Flash point
point temperature
temperature determined
determined in
in aa closed
closed crucible
crucible for
for the
the lubricating
lubricating oils
oils tested
tested at
at
different
levels of
of lubricating
lubricating oil
oil dilution
dilution with
with diesel
diesel fuel.
fuel.
different levels
Measured ignition
significantly
lower
than
those
obtained
by Ferignitiontemperatures
temperatureswere
were
significantly
lower
than
those
obtained
by
guson.
This
difference
is due
to to
both
the
Ferguson.
This
difference
is due
both
thedifferent
differentcomposition
compositionofofthe
theoil
oil (lubricating
(lubricating oil
and diesel
dieseloil)
oil)asaswell
well
different
conditions
under
which
the experiments
were conasas
different
conditions
under
which
the experiments
were conducted.
◦ C,103
ducted.
In the Ferguson
experiment,
the ignition
temperature
of the oil
diesel
was
°C,
In the Ferguson
experiment,
the ignition
temperature
of the diesel
wasoil
103
while
while
the present
experiment,
thediesel
pure fuel
diesel
fuel had
tested
an ignition
temperature
in the in
present
experiment,
the pure
tested
an had
ignition
temperature
of only
65 ◦ C. The observations show that the literature results are not authoritative for modern
distillate fuels and lubricating oils. Importantly, a significant reduction in the ignition
temperature of the oil as a result of its contamination with diesel was confirmed.
Note that for a 5% m/m contamination of the engine’s circulating oil with diesel
fuel, which can occur in operating practice, the flash point decreased by as much as 46 ◦ C
compared to that of pure lubricating oil. Such a large decrease indicates a significant
Energies 2023, 16, 683
of only 65 °C. The observations show that the literature results are not authoritative for
modern distillate fuels and lubricating oils. Importantly, a significant reduction in the ignition temperature of the oil as a result of its contamination with diesel was confirmed.
Note that for a 5% m/m contamination of the engine’s circulating oil with diesel fuel,
which can occur in operating practice, the flash point decreased by as much as 4622°C
comof 38
pared to that of pure lubricating oil. Such a large decrease indicates a significant relationship between fuel contamination and the ignition properties of the oil, and thus the risk
of ignition in the crankcase.
relationship between fuel contamination and the ignition properties of the oil, and thus the
autoignition
delay described by the cetane number and other indicators indiriskThe
of ignition
in the crankcase.
cated in
the
materials
and methods
characterizes
an oil
in indicators
terms of its
ability to
The autoignition delay
describedsection
by the cetane
number and
other
indicated
ignite
(the
shorter
the
ignition
delay,
the
better
the
autoignition
properties).
In
the
case in
in Section 2 characterizes an oil in terms of its ability to ignite (the shorter the ignition
question
ofbetter
the analysis
of the autoignition
capability
ofquestion
lubricating
oils,
the lower
delay, the
the autoignition
properties). In
the case in
of the
analysis
of the the
cetane
number,
the better
the oil is. Figure
shows
of the self-ignition
capability
autoignition
capability
of lubricating
oils, the23lower
theresults
cetane number,
the better the
oil is.
Figure 23 shows results of the self-ignition capability tests.
tests.
Figure23.
23.Ignition
Ignitionand
andcetane
cetane indices
indices of
different
levels
of lubricating
oil oil
Figure
of tested
testedlubricating
lubricatingoils
oilsatat
different
levels
of lubricating
dilution
with
diesel
fuel.
dilution with diesel fuel.
Figure 24 shows ignition indices analogous to the cetane number: derived cetane
Figure 24 shows ignition indices analogous to the cetane number: derived cetane
number, DCN, calculated cetane index, CCI, and calculated ignition index, CII. The DCN
number, DCN, calculated cetane index, CCI, and calculated ignition index, CII. The DCN
value was found to be 52 for pure diesel fuel. The CCI values were determined due to
value
was feasibility
found to (difficulty
be 52 for in
pure
dieselthe
fuel.
The CCI
technical
distilling
fractions)
for values
the 50%were
m/mdetermined
concentrationdue
of to
technical
feasibility
(difficulty
intested
distilling
fractions)
theIn50%
m/m concentration
diesel fuel
in the lubricating
oils
and the
for pure
dieselfor
fuel.
the concentration
range of
diesel
fuel
in
the
lubricating
oils
tested
and
for
pure
diesel
fuel.
In
the
concentration
range
of 50–100% m/m, the CCI value ranges from 52.1 to 53.2 for the tested oils. In contrast,
ofthe
50–100%
m/m,
the
CCI
value
ranges
from
52.1
to
53.2
for
the
tested
oils.
In
contrast,
calculated average CII values for the entire concentration range are between 60.2 and the
calculated
average
for61.1
theand
entire
between
and 46.6
46.6 for SAE
30 oil CII
andvalues
between
46.6concentration
for SAE 40 oil.range
With are
an increase
in60.2
the diesel
of the
mixture
in both61.1
cases,
the
CCIfor
value
decreases,
which
indicate
slight
forcontent
SAE 30
oil and
between
and
46.6
SAE
40 oil. With
anmay
increase
in athe
diesel
increase
in
the
ignition
delay
and
a
deterioration
in
the
mixture’s
self-ignition
capability.
content of the mixture in both cases, the CCI value decreases, which may indicate a slight
Nevertheless,
these values
areand
high
throughout theinmeasurement
(>45), which,
by
increase
in the ignition
delay
a deterioration
the mixture’srange
self-ignition
capability.
analogy with these
fuels, values
can be interpreted
as a very low
delay,
and therefore
very by
Nevertheless,
are high throughout
theautoignition
measurement
range
(>45), which,
good ignition properties.
Energies 2023, 16, x FOR PEER REVIEW
Energies 2023, 16, 683
25 of 41
of 38
analogy with fuels, can be interpreted as a very low autoignition delay, and therefore23very
good ignition properties.
Figure
Figure 24.
24. Calculated
Calculated carbon
carbon aromaticity
aromaticity index
index of
of the
the tested
tested lubricating
lubricating oils
oils at
at different
different levels
levels of
of
lubricating
lubricating oil
oil dilution
dilution with
with diesel
diesel fuel.
fuel.
Analogous
the
calculated
carbon
aromaticity
index
CCAI
waswas
deAnalogous to
toCII,
CII,the
thevalue
valueofof
the
calculated
carbon
aromaticity
index
CCAI
termined
for for
the tested
mixtures.
CCAI CCAI
valuesvalues
increase
with increasing
diesel fuel
contamdetermined
the tested
mixtures.
increase
with increasing
diesel
fuel
ination.
CCAI values
between
781.4 and781.4
795.5and
for 795.5
SAE 30
blends
between
contamination.
CCAIvary
values
vary between
foroil
SAE
30 oiland
blends
and
775.6
and775.6
795.5 and
for SAE
40for
oil SAE
blends.
these
values these
to thevalues
standards
provided
for
between
795.5
40 Relating
oil blends.
Relating
to the
standards
residual
lubricating
contamination
with dieselwith
fuel diesel
has nofuel
significant
effect on
providedfuels,
for residual
fuels,oil
lubricating
oil contamination
has no significant
the
autoignition
delay, which
corresponds
to very good
autoignition
properties.
effect
on the autoignition
delay,
which corresponds
to very
good autoignition
properties.
4. Final
Final Conclusions
Conclusions
4.
There is
is no
no doubt
doubt that
that measuring
measuring the
the ignition
ignition temperature
temperature of
of the
the oil
oil makes
makes it
it possible
possible
There
to
quickly
diagnose
a
situation
where
fuel
contamination
has
occurred
in
the
oil.
Because
to quickly diagnose a situation where fuel contamination has occurred in the oil. Because
laboratory
tests
of
lubricating
oil
are
carried
out
periodically
at
fixed
intervals
between
laboratory tests of lubricating oil are carried out periodically at fixed intervals between
tests, they
they will
and
rapidly
developing
tests,
will not
not be
be aavaluable
valuablemeasure
measureininthe
thesituation
situationofofsudden
sudden
and
rapidly
developdamage
to
piston
rings,
pistons,
cylinder
liners,
and
injectors.
However,
it
cannot
be ruled
ing damage to piston rings, pistons, cylinder liners, and injectors. However, it cannot
be
out
that
in
situations
of
long-developing
engine
deterioration,
testing
the
oil
for
potential
ruled out that in situations of long-developing engine deterioration, testing the oil for pofuel contamination
may bemay
a key
in increasing
the safety
engine
[71].
tential
fuel contamination
beelement
a key element
in increasing
theofsafety
of operation
engine operaFor
the
same
reason,
the
flash
point
test
has
been
adopted
by
all
major
used
oil
laboratories
tion [71]. For the same reason, the flash point test has been adopted by all major used oil
as a service standard
to vessel
operators.
laboratories
as a service
standard
to vessel operators.
It should be emphasized that the authors of the CIMAC publication [31] do not rule
It should be emphasized that the authors of the CIMAC publication [31] do not rule
out the possibility of using an indicator such as flash point to diagnose whether or not
out the possibility of using an indicator such as flash point to diagnose whether or not oil
oil contamination with fuel (residual or distillate) has occurred. The publication states
contamination with fuel (residual or distillate) has occurred. The publication states that
that “For engines which alternate between heavy fuel and distillate fuel usage, flash
“For engines which alternate between heavy fuel and distillate fuel usage, flash point
point measurements can be used to monitor the origin of possible fuel contamination
measurements can be used to monitor the origin of possible fuel contamination (the
(the contamination of heavy fuel and distillate fuel can compensate the resulting changes
in viscosity)”.
The main observations from the author’s own experiment are as follows:
1.
A decrease in the lubricating oil flash point is an indicator of oil contamination with fuel.
Energies 2023, 16, 683
24 of 38
2.
A change in viscosity does not necessarily indicate contamination (among other
contaminations), since, depending on the type of fuel, oil viscosity can:
•
not change (engines powered by different fuels);
•
decrease (engines powered by distillation fuel);
•
increase (engines fueled by residual fuel).
A change in viscosity itself is not necessarily caused by contamination of the oil with
fuel, but could be due to contamination with other oil (such as cylinder oil), contamination
of the oil with water, bacteria, fungi, and protozoa; oxidation of the oil, etc. [72–74].
3.
4.
5.
Changing the oil composition can change its viscosity, which alters the distribution of
the number and size of droplets in the oil mist. Occurrence of this mist, once set limits
are exceeded, promotes the initiation of explosions.
A reduction in the ignition temperature of a mixture may be indirectly associated
with a reduction in the autoignition temperature (although not necessarily) [14,75]. If
this situation occurs, the risk of explosion increases in view of the higher volatility
of diesel fuel than lubricating oil. Contamination of lubricating oil with distillation
fuel does not significantly affect the autoignition delay, which, for clean and contaminated oil, corresponds to conditions that can be classified as very good autoignition
properties [76].
Deterioration of the tribological conditions of the bearings, as seen in the change
in viscosity, viscosity index, and lubricity of the oil, causes an increase in bearing
temperature and the possibility of hot spots. Viscosity index, lubricity, coefficient of
friction and reduction in oil film resistance change significantly when the concentration of diesel fuel in the lubricating oil exceeds 10%. The observation is in line with
some previous works [36]. At such concentrations, increased friction in tribological
pairs lubricated with lubricating oil contaminated with diesel fuel can intensify the
wear of mating components, increase their temperature, and ultimately intensify the
formation of white oil mist in the crankcase.
Summing up, there are two extreme approaches in the literature to the subject of diesel
lubricating oil contamination and the effects of this contamination on engine operation. The
first, which was the inspiration for the article, is the approach presented by Ferguson and in
the paper published by CIMAC. This approach states that the effects of diesel contamination
in lubricating oil are negligible even at high diesel concentrations in the lubricating oil. The
second approach points to an increased risk of engine seizure and cites 2–5% diesel content
in lubricating oil as alarming levels. However, neither approach is well-argued, and a
holistic approach to the subject has not been presented. In this article, results show that
when the diesel oil content in the lubricating oil exceeds 10%, oil–film rupture occurs, and
this can result in increased wear of tribological couples, such as bearings in the crank–piston
system. At the same time, given the decrease in viscosity and thus the deterioration of
lubrication conditions, and the decrease in evaporation and ignition temperatures, one
can conclude that the synergistic interaction of these factors increases the risk of explosion
in the engine crankcase. Further conclusions could be provided as a result of an oil mist
morphology analysis, which is planned to be the next step in the future research.
Funding: This research was funded by the Ministry of Science and Higher Education (MEiN) of
Poland, grant number 1/S/KPBMiM/22. The APC was funded by MDPI.
Data Availability Statement: All data are available in the dataset: Chybowski, L. Lube oil—diesel
oil mixes-dataset; 2022, Ver. 3, DOI: 10.17632/scbx3h2bmf.3. Dataset is available at https://data.
mendeley.com/datasets/scbx3h2bmf/3 (accessed on 8 November 2022) [57].
Acknowledgments: Laboratory tests were performed on behalf of the author at the Center for Testing
Fuels, Working Fluids, and Environmental Protection (CBPCRiOS) of the Maritime University of
Szczecin. The author would like to thank Magdalena Szmukała and Barbara Żurańska for the
technical support.
Energies 2023, 16, 683
25 of 38
Conflicts of Interest: The author declares no conflict of interest. The funders had no role in the design
of the study, in the collection, analyses, or interpretation of data, in the writing of the manuscript, or
in the decision to publish the results.
Abbreviations
ASTM
CCE
CEA
CFR
CID
CIMAC
CCAI
CCI
CI
CII
CN
CVCC
DCN
DO
ECP
FDM
FID
FILM
FIT
FP
FTIF
GC
HFO
HFRR
IEC
IQT
ISO
SAE
SAE 30, SAE 40
SAW
VI
WSD
Symbols
m
t
V
.
γ
ε
η
λ
µ
ν
ρ
ρ15
ρt
τ
τF
American Society for Testing and Materials
crankcase explosion
crankcase explosion apparatus
Cooperative Fuel Research
cetane ignition delay
International Council on Combustion Engines
calculated carbon aromaticity index
calculated cetane index
cetane index
calculated ignition index
cetane number
constant volume combustion chamber
derived cetane number
diesel oil
electrical contact potential
fuel dilution meter
flame ionization detector
measure of oil film resistance
fuel ignition tester
flash point temperature
Fourier-transform infrared
gas chromatography
heavy fuel oil
high frequency reciprocating rig
International Electrotechnical Commission
ignition quality tester
International Organization for Standardization
Society of Automotive Engineers
viscosity grades of lubricating oils according to SAE J300-2021 standard
surface acoustic wave
viscosity index
wear scar diameter
mass of the substance
measured temperature of the substance under operating conditions
volume of the substance
shear rate
the coefficient of change of density of a substance when it is heated by 1 ◦ C
dynamic viscosity of the substance
thermal conductivity coefficient
coefficient of friction
kinematic viscosity of the substance
density of the substance
density of the substance at 15 ◦ C
density of the substance at temperature t
time
shear stresses
Energies 2023, 16, 683
26 of 38
Appendix A.
Table A1. Fuel inflow caused by mechanical effect (based on [30]).
Action
Effect
What to Do
Continued operation with
stops and start.
The fuel does not burn off completely.
Reduce the mileage change interval to the
strictest change interval indicated by the
manufacturer.
Starting in the cold.
The fuel does not burn off well because the
combustion temperature is low.
Wait for the engine to increase in temperature
before accelerating.
Problems in the
injection system.
The droplets of fuel being injected into the
chamber are big, leading to poor combustion.
Incomplete combustion is occurring; inspect
the injectors.
Poor combustion.
The fuel is not burning off completely.
Incomplete combustion is occurring. Check that
the combustion chamber and the injection
system are working properly.
Worn-out engine parts: valve
guides, injectors, and wear.
Conditions change in the combustion
chamber, meaning it is no longer optimized.
Inspect the engine and injectors.
Excessive acceleration.
Excess inflow of fuel.
Incomplete combustion is occurring; adjust
control system.
Mixture of rich fuels.
Excess fuel.
Incomplete combustion is occurring; inspect the
injection system.
Faulty injectors.
Can produce excessive inflow of fuel or
inadequate fuel injection.
It does not burn fuel as well, resulting in
deposits. Inspection of the injection system.
Table A2. Advantages and disadvantages of the main methods of detecting fuel in lubricating oil
(prepared on the basis of [56]).
Method
Advantages
Disadvantages
Gas Chromatography
Widely accepted industry standard
Highly precise
Suited for high volume labs
Can detect biodiesel and ethanol
Can only be carried out in a lab
Mandates costly equipment and gases
Takes much time to produce best results
Requires an expensive equipment and gases
Viscosity Analysis
The availability of portable instruments and
lab instruments
Accepted routine test for testing lubricant condition
Optimum screening test for probable fuel dilution
Ability to detect ethanol and biodiesel
Inability to definitively indicate fuel
dilution issue
Mandates a careful technician
Flash Point Testing
A pass/fail result is enough in the case of most
applications
Ability to detect ethanol
Very little sample required (1–2 mL)
Inability to detect biodiesel
Mandates a careful technician
Knowledge of the oil/fuel type mandatory for
quantitative measurement
Risks posed by heating fuel-laden samples
FTIR Spectroscopy
Low cost per sample after initial equipment
purchase; test can be carried out quickly
Mandates the use of costly equipment;
calibrations are mostly specific to a narrow
sample type
Surface Acoustic Wave
Sensing
Easy to use
Portable
Requires only 0.5 mL of sample
Less expensive than gas chromatographs
Can complete the test quickly
Easily adaptable to different oil/fuel types
Inability to measure biodiesel
Mandates calibration with a reference fluid
Energies 2023, 16, 683
27 of 38
Table A3. Properties of Orlen Efecta Diesel Bio as declared by the manufacturer [60].
Specification
Parameter
Cetane index
≤51
Initial boiling point
75–180 ◦ C
Boiling temperature range
95% vol. distils to 360 ◦ C
Flash point (determined in a closed crucible)
>56 ◦ C
Autoignition temperature (according to DIN51794:2003-05)
approx. 240 ◦ C
Kinematic viscosity (according to EN ISO 3104)
1.5–4.5 mm2 /s (2.549 mm2 /s) at 40 ◦ C
approx. 2.151 mm2 /s at 50 ◦ C
Density
820–845 kg/m3 at 15 ◦ C
Relative vapor density
approx. 6 (air = 1)
Cloud point
−7 ◦ C
Cold filter plugging point
−8 ◦ C
Table A4. Manufacturer-declared physicochemical properties of Agip Cladium 120 CD lubricating
oils used in tests [61–63].
Specification
Parameter
Agip Cladium 120
Agip Cladium 120
SAE 30 CD
SAE 40 CD
108 mm2 /s at 40 ◦ C
160 mm2 /s at 40 ◦ C
Kinematic viscosity (according to EN ISO 3104)
12.0 mm2 /s at 100 ◦ C
15.7 mm2 /s at 100 ◦ C
Viscosity
index
100
100
Tribometer
Friction Association
Type of Contact
Application of Tests
Total base number
12 mg KOH/g
12 mg KOH/g
Flash point (marked in closed crucible)
225
235 ◦ C
Tribometer
Friction Association
Type of Contact Testing
Application
of Testsof lubricating
the anti-wear
properties
Pour point
−18 ◦ C
−15 ◦ C
◦C
Four-ball
machine
Punctual
oils,
lubricants and
other operating
Density Friction Association
895 kg/m3 at
15 plastic
900 kg/m3 at 15 ◦ C
Tribometer
Type
of Contact
Application
of Tests
Testing the anti-wear
properties of lubricating
fluids.
Tribometer
Friction Association
Type
of Contact
of Tests
Four-ball
machine
Punctual
oils, plasticApplication
lubricants and
other operating
the anti-wear properties of lubricating
Table A5. Basic characteristics ofTesting
several
machines
to study the lubricating properties (compiled
fluids.
Tribometer
Friction Association
Type
of Contact
of Tests
Four-ball
machine
Punctual
oils, plasticApplication
lubricants and
other operating
Testing the anti-wear properties of lubricating
from [65,77]).
fluids.
Testing
theApplication
anti-wear properties
of plastic
Tribometer
Friction Association
Type
of Contact
of Tests
Four-ball
machine
Punctual
oils,
plastic
lubricants
and
other operating
Linear
Timken
Testing the anti-wear
properties
of lubricating
lubricants.
Tribometer
Friction
Association
Type
of
Contact
Application
of
Tests
fluids.
Tribometer
Friction Association
Type of Contact
Application of Tests
Four-ball machine
Punctual
oils,
plastic
lubricants
and other operating
Testing
anti-wear
properties
plastic
Testing
thethe
anti-wear
properties
of of
lubricating
Linear
Timken
fluids.
lubricants.
Four-ball machine
Punctual
oils,
plastic
lubricants
and other
Testing
thethe
anti-wear
properties
ofoperating
lubricating
Testing
anti-wear
properties
of
plastic
Testing the anti-wear
properties of lubricating oils, plastic lubricants
Linear
Timken
fluids.
Four-ball
machine
Punctual
oils, plastic
lubricants
other
operating
Four-ball
machine
Punctual
lubricants.
Testing
the properties
ofand
the
solid
lubrication
and other of
operating
Testing the anti-wear
properties
plastic fluids.
fluids.
Linear
Timken
film, anti-wear properties
of lubricating oils and
Falex
lubricants.
Testing
properties
ofproperties
the solid
lubrication
thethe
properties
of plastic
lubricants.
Testing
the
anti-wear
of plastic
Linear
Timken
Linear
film, anti-wear properties
of lubricating oils and
Falex
lubricants.
Testing
the
properties
the solid lubrication
Testing
the
anti-wearofproperties
of plastic
Linear
Timken
the properties
of plastic
lubricants.
Timken
Linear
Testing the
anti-wear
properties of plastic lubricants.
Linear
film,
anti-wear
properties
of lubricating
oils and
Falex
lubricants.
Testing
the anti-wear
properties
of plastic
Testing the properties of the solid lubrication
Linear
Timken
the
properties
ofproperties
plastic lubricants.
Testing
the
anti-wear
and maximum
lubricants.
Surface
Almen-Eieland
Linear
film, anti-wear properties of lubricating oils and
Falex
load of lubricating
oilsof
and
lubricants.
Testing
the properties
theplastic
solid lubrication
theTesting
properties
of plastic lubricants.
the properties
ofand
the maximum
solid lubrication film, anti-wear
Testing
the anti-wear
properties
Linear
film,
anti-wear
properties
of lubricating
oils and
Falex
Linear
Falex
Surface
Almen-Eieland
Testing
the
properties
of
the
solid
lubrication
properties of lubricating oils and the properties of plastic lubricants.
load of
and plastic
lubricants.
thelubricating
propertiesoils
of plastic
lubricants.
Testing
the
properties
andlubrication
maximum
Linear
film,
anti-wear
properties
oils and
Falex
Testing
theanti-wear
properties
of of
thelubricating
solid
Surface
Almen-Eieland
load
of
lubricating
oils
and
plastic
lubricants.
the
properties
of
plastic
lubricants.
Linear
film,
anti-wear
properties
of
lubricating
oils
and
Falex
Testing
theanti-wear
anti-wear
properties
of lubricating
Testing
the
properties
and
maximum
Testing
the anti-wear
properties
and maximum load of lubricating
Linear
FZG
Surface
Almen-Eieland
Almen-Eieland
Surface
theplastic
properties
of plastic
lubricants.
oils
and
lubricants,
especially
gear
oils.
oilsplastic
and plastic
lubricants.
load of lubricating oils and
lubricants.
Testing
maximum
Testingthe
theanti-wear
anti-wearproperties
propertiesand
of lubricating
Surface
Almen-Eieland
Linear
FZG
loadand
of lubricating
oils andespecially
plastic lubricants.
oils
plastic lubricants,
gear oils.
Testing
properties
and
maximum
Testingthe
theanti-wear
anti-wear
properties
of lubricating
Testing
the anti-wear
properties
of lubricating oils and plastic
Surface
Almen-Eieland
Linear
FZG
FZG
Linear
load
of
lubricating
oils
and
plastic
lubricants.
Testing
the
anti-wear
properties
of
thermoTesting
the
anti-wear
properties
and
maximum
oils and plastic lubricants,
especially
gear oils.
lubricants,
especially
gear oils.
Surface
Almen-Eieland
Testing
anti-wear
properties
ofturbine
lubricating
Vickers
Punctual
oxidizing
fluids
hydraulic
oils,
load
of the
lubricating
oils
andfluids,
plastic
lubricants.
Linear
FZG
oils
and plastic
lubricants,
gear oils.
Testing
theanti-wear
anti-wear
properties
thermogear
oils.especially
Testing
the
properties
ofoflubricating
Testing
the anti-wear
properties
of thermo-oxidizing fluids hydraulic
Linear
FZG
Vickers
Punctual
oxidizing
fluids
hydraulic
fluids,
turbine
oils,
Vickers
Punctual
oils
and plastic
lubricants,
especially
gear
fluids,
turbine
oils,oils.
gear oils.
Testing
theanti-wear
anti-wear
properties
thermoTesting
the
ofoflubricating
gearproperties
oils.
Linear
FZG
Vickers
Punctual
oxidizing
fluids
hydraulic
fluids,
turbine
oils,
oils
andthe
plastic
lubricants,
especially
gear oils.
Testing
properties
ofoflubricating
Testing
theanti-wear
anti-wear
properties
thermoLinear
FZG
gear oils.
oils
and the
plastic
lubricants,
especially
gear oils,
oils.
Vickers
Punctual
oxidizing
fluids
hydraulic
fluids,
turbine
Testing
anti-wear
properties
of
diesel
Testing
the anti-wear
properties
of oils,
diesel oils, heating oils and
Testing
the anti-wear
properties
of thermoHFFR
Punctual
Punctual
HFFR
heating oilsgear
and oils.
lubricating
oils. oils.
lubricating
Vickers
Punctual
oxidizing fluids hydraulic fluids, turbine oils,
Testingthe
theanti-wear
anti-wearproperties
propertiesofofdiesel
thermoTesting
oils,
HFFR
Punctual
gear oils.
Vickers
Punctual
oxidizing
fluids
hydraulic
fluids, turbine
oils,
heating
oils
and properties
lubricating
Testing
the
anti-wear
ofoils.
thermoTesting the anti-wear properties of diesel oils,
gear oils.fluids, turbine oils,
HFFR
Punctual
Vickers
oxidizing fluids hydraulic
heating oils and lubricating oils.
gearproperties
oils.
Testing the anti-wear
of diesel oils,
HFFR
Punctual
heating oils and lubricating oils.
Testing the anti-wear properties of diesel oils,
HFFR
Punctual
heating oils and lubricating oils.
Testing the anti-wear properties of diesel oils,
Oil
Energies 2023, 16, 683
28 of 38
Table A6. ASTM cetane rating Standards and Applicable Ranges (prepared on the basis of [66–68]).
ASTM Standard
CN Applicable Range
Range (mix.—min.)
Instrument
D6890 (DCN)
33–64
64–100
31.0
36.0
IQT (CVCC)
D613 (CN)
40–56
16.0
CFR engine
D7170 (DCN)
39.5–55.2
15.7
FIT (CVCC)
D7668 (DCN)
39.4–66.8 [66]
35.0–60.0 [67]
15.0–100.0 [68]
27.4 [66]
25.0 [67]
85.0 [68]
CID 510 (CVCC)
D976 (CI)
30–60
30.0
Correlation
D4737 (CCI)
32.5–56.5
24.0
Correlation
Energies 2023, 16, x FOR PEER REVIEW
31 of 41
Appendix
AppendixB.
B.Photographs
Photographsof
ofTraces
TracesofofWear
Wearon
ona aMoving
MovingComponent
Componentafter
afterananHFRR
HFRR
Lubricity
Test
Lubricity Test
Figure A1. SAE 30–100%; DO—0%.
Figure A1. SAE 30–100%; DO—0%.
Energies 2023, 16, 683
29 of 38
Figure A1. SAE 30–100%; DO—0%.
Energies 2023, 16, x FOR PEER REVIEW
Figure A2. SAE 30—99% m/m; DO—1% m/m.
Figure A2. SAE 30—99% m/m; DO—1% m/m.
Figure A3. SAE 30—98% m/m; DO—2% m/m.
Figure A3. SAE 30—98% m/m; DO—2% m/m.
32 of 41
Energies 2023, 16, 683
30 of 38
Figure A3. SAE 30—98% m/m; DO—2% m/m.
Energies 2023, 16, x FOR PEER REVIEW
FigureA4.
A4.SAE
SAE30—95%
30—95%m/m;
m/m; DO—5%
DO—5% m/m.
m/m.
Figure
FigureA5.
A5.SAE
SAE30—90%
30—90%m/m;
m/m; DO—10%
DO—10% m/m.
m/m.
Figure
33 of 41
Energies 2023, 16, 683
31 of 38
Figure A5. SAE 30—90% m/m; DO—10% m/m.
Energies 2023, 16, x FOR PEER REVIEW
FigureA6.
A6.SAE
SAE30—80%
30—80%m/m;
m/m; DO—20%
DO—20% m/m.
m/m.
Figure
FigureA7.
A7.SAE
SAE30—50%
30—50%m/m;
m/m; DO—50%
DO—50% m/m.
m/m.
Figure
34 of 41
Energies 2023, 16, 683
32 of 38
Figure A7. SAE 30—50% m/m; DO—50% m/m.
Energies 2023, 16, x FOR PEER REVIEW
Figure A8. SAE 40—100%; DO—0%.
Figure A8. SAE 40—100%; DO—0%.
FigureA9.
A9.SAE
SAE40—99%
40—99%m/m;
m/m; DO—1%
DO—1% m/m.
m/m.
Figure
35 of 41
Energies 2023, 16, 683
33 of 38
Figure A9. SAE 40—99% m/m; DO—1% m/m.
Energies 2023, 16, x FOR PEER REVIEW
FigureA10.
A10.SAE
SAE40—98%
40—98%m/m;
m/m; DO—2%
DO—2% m/m.
m/m.
Figure
FigureA11.
A11.SAE
SAE40—95%
40—95%m/m;
m/m; DO—5%
DO—5% m/m.
m/m.
Figure
36 of 41
Energies 2023, 16, 683
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Figure A11. SAE 40—95% m/m; DO—5% m/m.
Energies 2023, 16, x FOR PEER REVIEW
FigureA12.
A12.SAE
SAE40—90%
40—90%m/m;
m/m; DO—10%
DO—10% m/m.
m/m.
Figure
FigureA13.
A13.SAE
SAE40—80%
40—80%m/m;
m/m; DO—20%
DO—20% m/m.
m/m.
Figure
37 of 41
Energies 2023, 16, 683
35 of 38
Figure A13. SAE 40—80% m/m; DO—20% m/m.
Energies 2023, 16, x FOR PEER REVIEW
38 of 41
FigureA14.
A14.SAE
SAE40—50%
40—50%m/m;
m/m; DO—50%
DO—50% m/m.
m/m.
Figure
FigureA15.
A15.SAE
SAE30/SAE
30/SAE 40—0%;
40—0%; DO—100%.
DO—100%.
Figure
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