Ambient Temperature
Operation and Matching
MAN B&W Two-stroke Engines
Content
Introduction ................................................................................................. 5
Standard ambient temperature matched engine............................................. 5
Operating at high seawater temperature with standard matched engine..... 6
Non-standard ambient temperature matched engine...................................... 7
Engine matching for non-standard air temperature conditions................... 7
Engine matching for high tropical seawater temperature conditions........... 8
Design recommendations for operation at extremely low air temperature....... 10
Main precautions for extreme low air temperature operation................... 10
Other low temperature precautions........................................................ 11
Ships with ice class notation.................................................................. 11
Increased steam production in wintertime............................................... 11
Closing remarks.......................................................................................... 12
Ambient Temperature Operation and Matching
MAN B&W Two-stroke Engines
Introduction
All diesel engines that are used as
Standard ambient temperature
matched engine
prime movers on ships are exposed
Standard unrestricted service demands
to the varying local climatic conditions
For a standard main engine, the en-
MAN Diesel has never measured levels
that prevail throughout the world.
gine layout is based on the ambient
above 50% at 45ºC, and humidity le-
reference conditions of the Interna-
vels above standard tropical ambient
tional Standard Organization (ISO):
conditions will never occur.
be extremely high. Likewise in arc-
ISO 3046-1:2002(E) and
When applying the central cooling wa-
tic areas, the temperatures can be
ISO 15550:2002(E):
ter system which, today, is more com-
very low. Under both extreme tem-
ISO ambient reference conditions
monly used than the seawater system,
perature conditions some engine de-
Barometric pressure: 1,000 mbar
the corresponding central cooling wa-
sign precautions might be necessary
to enable the engine to operate in unre-
Turbocharger air intake
temperature: 25ºC
4ºC higher than the seawater tempera-
stricted service.
Charge air coolant temperature: 25ºC
ture, i.e. equal to 36ºC.
Relative air humidity: 30%
In some areas, the ambient sea and
for humans to survive. The corresponding wet bulb temperature is 36.8ºC.
air temperatures can, occasionally,
This paper will outline operation possi-
ter/scavenge air coolant temperature is
bilities with a standard matched engine
The winter ambient reference conditions used as standard for MAN B&W
in any extreme temperature environ-
With this layout basis, the engine
ment and describe the possibilities for
must be able to operate in unrestrict-
special matching of engines for more
ed service, i.e. up to 100% Specified
permanent operation under such con-
Maximum Continuous Rating (SMCR),
Winter ambient reference conditions
ditions.
within the typical ambient temperature
Barometric pressure: range that the ship is exposed to, oper-
Turbocharger air intake temperature: ating from tropical to low winter ambi-
two-stroke engines are as follows:
1,000 mbar
10ºC
ent conditions.
Cooling water temperature:
(minimum for lub. oil cooler) 10ºC
According to the International Associa-
Relative air humidity: 60%
tion of Classification Societies (IACS)
rule M28, the upper requirement, nor-
Shipyards often specify a constant
mally referred to as tropical ambient ref-
(maximum) central cooling water tem-
erence conditions, is as follows:
perature of 36°C, not only for tropical
ambient conditions, but also for winter
ambient conditions. The purpose is to
IACS M28 (1978):
reduce the seawater pump flow rate
Tropical ambient reference conditions
when possible, and thereby to reduce
Barometric pressure: 1,000 mbar
the electric power consumption, and/or
Air temperature: 45ºC
to reduce the water condensation in the
Seawater temperature 32ºC:
air coolers.
Relative air humidity: 60%
However, when operating with 36°C
The above tropical ambient relative hu-
cooling water instead of for example
midity of 60% at 45ºC is theoretically
10°C (to the scavenge air cooler), the
the absolute limit at which it is possible
specific fuel oil consumption (SFOC)
will increase by approx. 2 g/kWh, see
Ambient Temperature Operation and Matching – MAN B&W Two-stroke Engines
5
SFOC
g/kWh
Turbocharger air intake temperature: 10°C
36°C C.W
10°C C.W
2 g/kWh
of the engine room components. The
Nevertheless, the engine’s obtainable
55ºC is the temperature used when
load level will in all cases be much
approving engine room components.
higher than required to ensure a safe
This, however, must not be mistaken
manoeuvrability (46 knots) of the ship
for the above air intake temperature of
even at an extreme seawater tempera-
45ºC specified when related to the ca-
ture of for example 42°C.
pacity or effect of the machinery.
40
50
60
70
80
100% SMCR
90
Engine shaft power
Fig. 1: Influence on SFOC of the cooling water
(scavenge air coolant) temperature
When sailing in, for example, the harIn recent years, owners/shipyards have
bour area during manoeuvring, the en-
sometimes required unrestricted ser-
gine load will normally be relatively low
vice on special maximum ambient tem-
(1530% SMCR), and the correspond-
peratures higher than the tropical am-
ing scavenge air temperature will then
bient temperatures specified by IACS
only be slightly higher than the scav-
Fig. 1. Any obtained gain in reduced
M28. In such cases, the main engine
enge air coolant temperature. There-
electric power consumption, therefore,
has to be special high temperature
fore, a seawater temperature as high
will be more than lost in additional fuel
matched, as described later in this pa-
as for example 42°C in harbour areas
costs of the main engine.
per.
is not considered a problem for the
main engine, and a special temperature
The above ISO, tropical and win-
Furthermore, operation in arctic areas with
matching is not needed under these
ter ambient reference conditions are
extremely low air temperatures has also
operating conditions
used by MAN Diesel for ships, and
sometimes been required by owners/
MAN B&W two-stroke engines com-
shipyards, and the measures to be taken
In general, when sailing in areas with a
ply with the above rules. MAN B&W
are also described later in this paper.
high seawater temperature, it is pos-
engines matched according to the
sible to operate the standard ambient
above rules are able to operate con-
Operating at high seawater tempera-
temperature matched main engine at
tinuously up to 100% SMCR in the
ture with standard matched engine
any load as long as the scavenge air
air temperature range between about
An increase of the seawater tempera-
temperature alarm limit is not reached.
-10 and 45ºC.
ture and, thereby, the scavenge air
If the alarm is activated, the engine load
temperature has a negative impact on
has to be reduced.
Often the engine room temperature is mi-
the heat load conditions in the combus-
staken for being equal to the turbocharger
tion chamber. Therefore, all MAN B&W
air intake temperature. However, since the
twostroke engines for marine applica-
air ventilation duct outlets for a normal
tions have an alarm set point of 55°C
air intake system are placed near the
for the scavenge air temperature for pro-
turbochargers, the air inlet temperature
tection of the engine, as described later.
to the turbochargers will be very close
to the ambient outside air temperature.
For a standard ambient temperature
Under normal air temperature condi-
matched engine operating at an in-
tions, the air inlet temperature to the
creased seawater temperature existing
turbocharger is only 13°C higher than
in some inland, gulf, bay and harbour
the ambient outside air temperature.
areas, the maximum power output of
the engine should be reduced to an
The classification society rules often
engine load resulting in a scavenge
specify an engine room air temperature
air temperature below the level of the
of 0-55ºC as the basis for the design
scavenge air temperature alarm.
6
Ambient Temperature Operation and Matching – MAN B&W Two-stroke Engines
Non-standard ambient temperature
matched engine
Engine matching for non-standard
An increase of, for example, 5ºC of the
air temperature conditions
tropical air temperature from standard
If unrestricted loads are desired in a
Usually, higher or lower turbocharger
45ºC to special 50ºC will result in a too
temperature range different from the
air intake temperatures may result in
low scavenge air pressure at 50ºC.
standard, different matching possibili-
lower or higher scavenge air pressures,
ties are available.
respectively, and vice versa.
Turbocharger
air intake temperature
65
60
Standard
ISO temperature
matched engine
55
50
45
Special
Low temperature
matched engine
40
35
Max.
Special
tropical
temperature
30
25
20
15
Special
design
temperature
Standard
design
Temperature
ISO
25 °C
ISO based
design
layout
0
-5
Min.
-10 °C
-15
-25
-30
-35
Min.
Lowest
ambient air
temperature
Max.
Special
tropical
temperature
Special
design
temperature
ISO
design
layout
For engine loads
higher than 30% SMCR
a low scavenge air
coolant temperature
is recommended
(Giving low SFOC and
low scav. air press.)
5
-10
Normal
tropical
temperature
Max.
45 °C
10
-20
Special
High temperature
matched engine
Normal min.
ambient air
temperature
Possible low ambient
air temperature
exhaust gas bypass for
operation under
extremely low ambient
temperature conditions
Min.
ISO based
design
layout
Lowest
ambient air
temperature
Low ambient air
temperature exhaust
gas bypass will be
needed below min.
temperature
-40
-45
-50
Up to 100% SMCR running is not allowed
Up to 100% SMCR running is allowed
Up to 100% SMCR running only allowed when low
ambient temperature exhaust gas bypass (C1+2)
is installed
Fig. 2: Principles for standard and special high (or low) ambient air temperature matched engines
Ambient Temperature Operation and Matching – MAN B&W Two-stroke Engines
7
However, the pressure reduction can
At the other end of the air temperature
This involves that the exhaust gas tem-
be compensated for by specifying a
range, the increase of 5ºC of the de-
perature will increase by about 16ºC
correspondingly higher (turbocharger)
sign air intake temperature will involve
compared with a standard ISO tem-
scavenge air pressure at ISO ambient
a too high scavenge air pressure when
perature matched engine, whereas the
reference conditions. This involves that
operating at -10ºC. Operation below
SFOC will increase.
the engine, instead of being matched
-10 + 5 = -5ºC will then only be pos-
for the ISO-based design air tempera-
sible when installing a variable exhaust
Engine matching for high tropical
ture of 25ºC, has to be matched for the
gas bypass valve system for low air
seawater temperature conditions
25 + 5 = 30ºC turbocharger air intake
temperatures, as described later.
For long time operation in an area with
high tropical seawater temperatures,
temperature.
Fig. 2 may in a similar way also be used
the following should be observed.
The original ISO-based heat load con-
to explain a special low temperature
ditions will then almost be obtained for
matched engine. For example, if the
An increase in the seawater tempera-
this higher design air temperature. The
standard tropical air temperature need-
ture and, thereby, of the scavenge air
principles for standard and special high
ed is reduced by 10ºC, from 45ºC to
coolant temperature will involve a simi-
ambient air temperature matched en-
35ºC, the engine matching design air
lar increase in the scavenge air tem-
temperature can be reduced to 25 -10
perature, which has a negative impact
= 15ºC.
on the combustion chamber tempera-
gines are shown in Fig. 2.
tures. Therefore, for all marine applica-
Temperature °C
Standard 55 °C
56
Standard ISO temperature
matched engine
Special high temperature
matched engine
Standard air cooler design
Special air cooler design
Scavenge air temperature limit
Scavenge air temperature limit
Max. 55 °C
54
52
50
Standard 48 °C
48
46
Maximum
scavenge air
temperature
at 100% SMCR
Maximum
scavenge air
temperature
at 100% SMCR
Max. 48 °C
High tropical
scavenge air
coolant
temperature
Max. 40 °C
High tropical
seawater
temperature
Max. 36 °C
44
42
40
38
Standard 36 °C
36
34
Standard 32 °C
32
30
Standard
tropical
scavenge air
coolant
temperature
Up to 100% SMCR running is
allowed (scavenge air)
Standard tropical
seawater
temperature
High scavenge
air coolant
temperature
28
Standard
basis 25 °C
26
24
ISO based
scavenge air
coolant
temperature
Up to 100% SMCR running is
not allowed (scavenge air)
ISO
design
layout
ISO based
design
layout
Max. 29 °C
Up to 100% SMCR running is
allowed (scavenge air coolant/central
cooling water)
Up to 100% SMCR running is
allowed (seawater)
22
Fig. 3: Principles for layout of scavenge air cooler for standard and special high scavenge air coolant temperature (illustrated for a central cooling water system)
8
Ambient Temperature Operation and Matching – MAN B&W Two-stroke Engines
tions, an alarm set point of 55ºC for the
scavenge air temperature is applied for
protection of the engine.
The standard marine scavenge air cooler
is specified with a maximum 12ºC temperature difference between the cooling
water inlet and the scavenge air outlet
at 100% SMCR, which gives a maximum scavenge air temperature of 36 +
12 = 48ºC for the scavenge air cooler
layout and, accordingly, a margin of 7ºC
to the scavenge air temperature alarm
limit of 55ºC.
A temperature difference of 8ºC is considered to be the lowest possible temperature difference to be used for a
realistic specification of a scavenge air
cooler. Accordingly, the 48 - 8 = 40ºC is
the maximum acceptable scavenge air
coolant temperature for a central cooling water system, see the principles for
layout of the scavenge air cooler in Fig. 3.
The demand for an increased tropical scavenge air coolant (central cooling water) temperature of up to 40ºC,
therefore, can be compensated for by a
reduced design temperature difference
of the scavenge air cooler. This can be
obtained by means of an increased water flow and/or a bigger scavenge air
cooler.
Ambient Temperature Operation and Matching – MAN B&W Two-stroke Engines
9
Design recommendations for operation at extremely low air temperature
Furthermore, the scavenge air cool-
compressor, thus reducing the air sup-
ant (cooling water) temperature
ply and scavenge air pressure to the
When a standard ambient temperature
should be kept as low as possible
engine.
matched main engine on a ship occa-
and/or the engine power in service
sionally operates under arctic condi-
should be reduced.
For the electronically controlled ME
tions with low turbocharger air intake
engine (ME/ME-C/ME-B), the load-de-
temperatures, the density of the air will
However, for an inlet air temperature
pendent bypass control can be incor-
be too high. As a result, the scavenge
below approx. -10ºC, some engine de-
porated in the Engine Control System
air pressure, the compression pressure
sign precautions have to be taken.
(ECS) as an add-on.
Main precautions for extreme low
Engine load, fuel index and scavenge
air temperature operation
air pressure signals are already availa-
In order to prevent such excessive pres-
With a load-dependent exhaust gas by-
ble for the ME software and, therefore,
sures under low ambient air tempera-
pass system (standard MAN Diesel rec-
additional measuring devices are not
ture conditions, the turbocharger air in-
ommendation for extreme low air tem-
needed for ME engines.
let temperature should be kept as high
perature operation), as shown in Fig. 4,
and the maximum firing pressure will be
too high.
as possible (by heating, if possible).
part of the exhaust gas bypasses the tur-
In general, a turbocharger with a nor-
bocharger turbine, giving less energy to
mal layout can be used in connection
Air intake casing
Exhaust gas bypass
Exhaust gas system
Exhaust gas
receiver
B
Turbine
1
C1+2
Turbocharger
D1
2
Scavenge
air receiver
D2
Diesel engine
B
Scavenge
air cooler
Compressor
Exhaust gas bypass valve
Controlled by the scavenge air pressure
D
D1
D2
Required electric measuring device
Scavenge air pressure
Engine speed and engine load
C1+2 Control device
Ensures that the load dependent scavenge air
pressure does not exceed the corresponding
ISO-based pressure
Fig. 4: Standard load-dependent low ambient air temperature exhaust gas bypass system
10 Ambient Temperature Operation and Matching – MAN B&W Two-stroke Engines
the
with an exhaust gas bypass. However,
in a few cases a turbocharger modifica-
The following additional modifications
Ships with ice class notation
tion may be needed.
of the standard design practice should
For ships with the FinnishSwedish ice
be considered as well:
class notation 1C, 1B, 1A and even
The exhaust gas bypass system ensures
that when the engine is running at part
1A super or similar, all MAN B&W
„„
load at low ambient air temperatures,
the load-dependent scavenge air pressure is close to the corresponding pres-
„„
sure on the scavenge air pressure curve
which is valid for ISO ambient condi-
„„
tions. When the scavenge air pressure
exceeds the read-in ISO-based sca-
„„
venge air pressure curve, the bypass
valve will variably open and, irrespec-
„„
Larger electric heaters for the cylin-
twostroke diesel engines meet the
der lubricators or other cylinder oil
ice class demands, i.e. there will be no
ancillary equipment
changes to the main engines.
Cylinder oil pipes to be further heat
traced/insulated
However, if the ship is with ice class
Upgraded steam tracing of fuel oil
notation 1A super and the main engine
pipes
has to be reversed for going astern
Increased preheater capacity for
(Fixed Pitch Propeller), the starting air
jacket water during standstill
compressors must be able to charge
Different grades of lubricating oil for
the starting air receivers within half an
turbochargers
hour, instead of one hour, i.e. the com-
that the engine is not overloaded. At the
„„
Space heaters for electric motors
pressors must be the double in size
same time, it will keep the exhaust gas
„„
Sea chests must be arranged so that
compared to normal.
tive of the ambient conditions, will ensure
temperature relatively high.
blocking with ice is avoided.
For other special ice class notations,
The latest generations of turbochargers
the engines need to be checked indi-
with variable flow, e.g. the VTA (Variable
vidually.
Turbine Area) system from MAN Diesel,
can replace the variable bypass and
The exhaust gas bypass system to be
ensure, the same scavenge air pressu-
applied is independent of the ice class-
re control.
es, and only depends on how low the
specified ambient air temperature is
Other low temperature precautions
expected to be. However, if the ship is
Low ambient air temperature and low
specified with a high ice class like 1A
seawater temperature conditions come
super, it is advisable to make prepara-
together. The cooling water inlet tem-
tions for, or install, an exhaust gas by-
perature to the lube oil cooler should
pass system.
not be lower than 10°C, as otherwise
the viscosity of the oil in the cooler will
Increased steam production in win-
be too high, and the heat transfer in-
tertime
adequate. This means that some of the
During normal operation at low am-
cooling water should be recirculated to
bient temperatures, the exhaust gas
keep up the temperature.
temperature after the turbochargers will
decrease by about 1.6ºC for each 1.0ºC
Furthermore, to keep the lube oil vis-
reduction of the intake air temperature.
cosity low enough to ensure proper
The load-dependent exhaust gas by-
suction conditions in the lube oil pump,
pass system will ensure that the exhaust
it may be advisable to install heating
gas temperature after the turbochargers
coils near the suction pipe in the lube
will fall by only about 0.3ºC per 1.0ºC
oil bottom tank.
drop in the intake air temperature, thus
enabling the exhaust gas boiler to pro-
Ambient Temperature Operation and Matching – MAN B&W Two-stroke Engines
11
duce more steam under cold ambient
Closing remarks
The use of the standard loaddependent
temperature conditions.
Diesel engines installed on oceangoing
low ambient air temperature exhaust
ships are exposed to different clima-
gas bypass system may – as an additi-
Irrespective of whether a bypass sys-
tic temperature conditions because of
onal benefit – also improve the exhaust
tem is installed or not, the exhaust gas
the ship’s trading pattern. Because the
gas heat utilisation when running at low
boiler steam production at ISO ambient
temperature variations on the sea sur-
ambient air temperatures.
conditions (25ºC air and 25ºC C.W.) or
face are relatively limited, the engines
higher ambient temperature conditions,
will normally be able to operate world-
Furthermore, at the other end of the
will be the same, whereas in wintertime
wide in unrestricted service without any
temperature scale, if the ship should
the steam production may be relatively
precautions being taken.
need to sail in unrestricted service in
increased, as the scavenge air pressure
is controlled by the bypass valve.
areas with very high ambient air tempeEven if the ship has to sail in very cold
ratures, higher than 45°C, this will also
areas, the MAN B&W two-stroke en-
be possible provided a high tempera-
As an example, Fig. 5 shows the influ-
gines can, as this paper illustrates, also
ture matching of the engine is applied.
ence of the load-dependent exhaust gas
operate under such conditions without
Even when sailing should be needed at
bypass system on the steam production
any problems as long as some low
very high seawater temperatures, this
when the engine is operated in winter-
temperature precautions are taken.
will be possible provided a specially de-
time, with an ambient air temperature of
signed scavenge air cooler is installed
0ºC and a scavenge air cooling water
on the diesel engine.
temperature of 10ºC.
Steam production
The calculations have been made for a
6S60MC-C7/ME-C7 engine equipped
kg/h
6S60MC-C7/ME-C7
SMCR = 13,560 kW at 105 r/min
2,500
with a high-efficiency turbocharger, i.e.
Air intake temperature: 0 °C
Cooling water temperature: 10°C
having an exhaust gas temperature of
245ºC at SMCR and ISO ambient con-
Total steam production,
with exhaust gas bypass
2,000
ditions.
Surplus steam
Total steam production,
without bypass
Fig. 5 shows that in wintertime, it is
questionable whether an engine with-
1,500
Steam consumption
out a bypass will meet the ship's steam
demand for heating purposes (indicated for bulk carrier or tanker), whereas
with a load-dependent exhaust gas by-
Extra steam needed
1,000
pass system, the engine can meet the
steam demand.
500
0
40
50
60
70
80
90
100% SMCR
Engine shaft power
Fig. 5: Expected steam production by exhaust gas boiler at winter ambient conditions (0 °C air) for main
engine 6S60MC-C7/ME-C7 with/without a load-dependent low air temperature exhaust gas bypass system
12 Ambient Temperature Operation and Matching – MAN B&W Two-stroke Engines
Ambient Temperature Operation and Matching – MAN B&W Two-stroke Engines
13
All data provided in this document is non-binding. This data serves informational
purposes only and is especially not guaranteed in any way. Depending on the
subsequent specific individual projects, the relevant data may be subject to
changes and will be assessed and determined individually for each project. This
will depend on the particular characteristics of each individual project, especially
specific site and operational conditions. Copyright © MAN Diesel & Turbo.
5510-0069-02ppr Aug 2014 Printed in Denmark
MAN Diesel & Turbo
Teglholmsgade 41
2450 Copenhagen SV, Denmark
Phone +45 33 85 11 00
Fax +45 33 85 10 30
info-cph@mandieselturbo.com
www.mandieselturbo.com
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