Marine NOx and COx Emissions under Various Operating Conditions*
Osami Nishida**, Tomohisa Kiuchi***, Hirotsugu Fujita**,
Wataru Harano **, Wataru Adati****, Keisuke Kadowaki*****
Masahiro Taguti******, Manami Morioka**, Mitsuaki Kato*******
This paper describes NOx and COx emissions from the diesel engine on mini-vessel such as 500GT class vessel
under transient operating condition and entering and departing conditions, because the reduction of the marine
exhaust emissions has been important subject. And the Intemational Maritime Organization (IMO) advances the
prevention of air pollution from ships in 1989. The regulated level of NOx emissions will be decided by the Bulk
Chemicals (BCH), in recent years. So the emission of carbon monoxide (CO), carbon dioxide (CO2), total
Hydrocarbons (THC), sulfur dioxide (SO2), and nitrogen oxide (NOx) occupy an important part. The transient
operating conditions have been formed by change of engine speed and PPA whose region are within the range of
500-673rpm,andl1-20deg.NOx concentration in summer voyage changes within the limits of 600-1000ppm,and
CO2 concentration changes within the limits of 4-7%.
１．Introduction
The international regulated value of NOx for
marine use is almost determined. The draft regulation by
California, USA imposes the additional sanction money
according to the emission value at the rate of 1O,OOO
USD per unit ton of NOx emission, and these
regulations are fairly stringent. These regulations will
come into force within several years. Noxiousness of
NO and NO2 among NOx, and the factor for warming
effect by CO2 among COx are greatly influential, and it
is necessary to understand these data in detail as much
as possible.
The NOx emission has been mainly measured
together with the dynamic properties of the hul1
(propulsion performance test, Z-test, turning test, and
arrival/departure) mainly in Osaka Bay and Seto Inland
――――――――――――――――――――――――――――――――――
*
Translated from Journal of MESJ Vo1. 32, No. 1
(Manuscript received Jun. 15, 1996) Lectured May 15,
1996
**
Kobe University of Mercantile Marine
(Higashi-nada-ku Kobe City)
***
Marine Technical College
(Ashiya City)
* * * * Daihatsu Diesel Manufacturing Co., Ltd.
(Chuou- ku Osaka City)
* * * * * Meitec Corporation
(Nishi-ku Nagoya City)
****** Showa Seiki Co., Ltd.
(Amagasaki City)
*******Hodaka Test Co.,Ltd.
(Asahi-ku Osaka City)
February 1998
Sea. In this report, the concentration of NO, NO2,
CO,CO2, and O2, and the excess air factor were
measured not only in the engine operating condition but
also in the propulsion performance test and the
arriva1/departure conditions to obtain detailed data.
2. Test Ship (Equipment) and Measuring
Method
The training ship "Fukae Maru" of Kobe University
of Mercantile Marine was used for the test. The
principal particulars are indicated in Table 2- 1, and the
principal particulars of the main engine are indicated in
Table 2-2 respectively. The main engine of the ship is
the 4-cycle diesel engine, and the propeller is the
controllable pitch propeller. Fig. 2-J shows the
peripheral sketch of the engine. Items of measurement
include the temperature of intake air, the temperature of
exhaust gas, the combustion pressure, the fue1 flow rate
and the brake horsepower, and the concentration of
NO,NO2, CO, CO2 and O2 were sampled from the
outlet T4 of the supercharger using a copper sampling
tube (2.5 m in length; 15.5 mm in inner diameter, and
19.0
(1)
2
Osami Nishida, Tomohisa Kiuchi, Hirotsugu Fujita, Wataru Harano, Wataru Adati,
Keisuke Kadowaki, Masahiro Taguti, Manami Morioka, Mituaki Kato
mm in outer diameter). The sample gas was measured
through the drain pot and the fi1ter as indicated in Fig.
2-2.
The time of measurement of the NOx data was set
at the intervals of 30 seconds taking into consideration
the time of measurement of the engine data by the
in-board LAN. Table 2-3 shows the principle, the type
and the accuracy of various kinds of gas concentration
measuring instruments. The NOx concentration and the
CO concentration were obtained by the controlled
potentia1 electrolysis method, and the O2 concentration
was obtained by the galvanic cell method. The CO2
concentration was obtained by the fol1owing formula
using the CO2 max value and the oxygen concentration
in the exhaust gas.
(2)
The shaft horsepower was measured by the shaft
horsepower meter of elongation strain detection type,
and the heat generation ratio was measured by the
combustion analysis device of the pressure meter of
strain type (CB-466, Ono Instrument).
Measurement was mainly implemented in July
(summer time) in I 995. The meteoro1ogical conditions
Bulletin of the M.E.S.J., Vol. 26, No.1
3
Marine NOx and COx Emissions under Various Operating Conditions
in the arrival/departure are indicated in Table 2-4. No
fluctuation to affect the exhaust gas was found in the
whole schedule.
3. Results of Measurement and Examination
Measurement was mainly made in the propulsion
performance test (on July 26 and 29), and in arrival (on
July 26) at and departure (July 29) from Beppu
Port.Conditions in the propulsion performance test are
indicated in Table 3- 1.
The engine speed (M[/E rev. : rpm] in the
propu1sion performance test, the propeller pitch angle
(PPA: deg), the torque (Tq: kNm), and the change in the
NOx 13 (ppm) which is the measured NOx
concentration converted into the oxygen concentration
137o are indicated in Fig. 3-1 with time. Numbers in the
figure indicate the operating condition corresponding to
each time in Table 3- 1.
gether with the torque fluctuation torque with the engine
speed (500, 552, and 673 rpm) as the parameter. As the
PPA is increased, i.e., the torque is increased while the
engine speed is constant, both the NO concentration and
the NO2 concentration are increased. When the engine
speed is reduced with the same torque, both the NO
concentration and the NO2 concentration are increased.
This seems to be caused by the increase in the thermal
NOx accompanied by the increase in the absolute time
of combustion in the cylinder. This trend is especially
shown in the NO2 concentration. It can be concluded
that the shaft torque of the main shaft can be
3.1 Status of NOx and COx Emission in Propulsion
Performance Test
Fig. 3-2(a)(b) shows the NO, and NO2 emission
concentration in the propulsion performance test to-
February 1 998
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4
Osami Nishida, Tomohisa Kiuchi, Hirotsugu Fujita. Wataru Harano, Wataru Adati,
Keisuke Kadowaki, Masahiro Taguti, Manami Morioka, Mituaki Kato
kept low by the operation method in which the engine
speed is high and the PPA is low with the same output,
and the emission concentration can be kept low by
reducing the time of generation of NOx in the cylinder.
The NO2 concentration is low in the emission
concentration compared with the NO concentration,
which is about 10-15%. The maximum emission
concentration of the NOx 13 concentration reached
about 1050 ppm in this test.
Fig. 3-3 shows the excess air factor to the torque
fluctuation with the engine speed (500, 552, and 673
rpm) as a parameter. The excess air factor was 3.1 at the
engine speed of 500 rpm, and PPA of 13 degrees, but
reduced as the torque was increased, and rapidly
reduced down to 2.3 with 15 kNm. Thereafter, the
excess air factor was slightly reduced to around 2.2 in
the normal operation (673 rpm, 19 deg.). It is concluded
that the excess air factor is not affected much by the
engine speed.
Fig. 3-4(a)(b) shows CO (ppm) and CO2 (%)
concentration to the fluctuation torque with the engine
speed (500, 552 and 673 rpm) as parameter. The CO2
concentration is not affected much by the engine
speed,and rapidly increased up to about 15 kNm in
torque as the torque is increased, and for larger torque,
the CO2 concentration is
gradually increased as the torque is
(4)
increased. The CO concentration is neither affected
much by the engine speed, and reduced up to about 15
kNm as the torque is increased, and gradually increased
as the torque is increased for larger torque. This seems
to be because the oxygen becomes insufficient when the
torque is more than about 15 kNm, i.e., when the excess
air factor is below about 2.3, the reaction to CO is
advanced, and the CO concentration is slightly
in-creased. The CO emission concentration in the test
was below 150 ppm.
Fig. 3-5 shows the relationship between the ratio of
generation of carbon monoxide {CO/(CO2+CO).vol,
% } and the ratio of genemtion of nitrogen monox-ide
{NO/(NO2+NO). vol, %} in the propulsion performance
test with the engine speed as a parameter. The ratio of
generation of nitrogen monoxide is reduced as the ratio
of generation of carbon monoxide is increased and the
engine speed is reduced. The high-temperature field is
easily formed in the region of lower ratio of generation
of carbon monoxide, and generation of NOx becomes
dominant.
3.2 Status of NOx and COx Emission in Departure
Various operation values of the engine in the
arriva1/departure condition, and the changes in the
concentration of the emission gas components are
Bulletin of the M.E.S.J., Vol. 26, No.1
5
Marine NOx and COx Emissions under Various Operating Conditions
shown with time.
a) In Arriva1
Data in affival condition are shown in Figs.
3-6(a)-(d). The figures show that the engine speed
is reduced from 600 rpm to 500 rpm while PPA is
constant 20 minutes before the engine is
stopped,and then, PPA is used at random. Though
the excess air factor was approximately constant at
2.5 before the engine speed of the main engine was
reduced, the excess air factor indicates the rising
trend as the torque is reduced when PPA is reduced.
The NOx 13 concentration was increased/
decreased as the torque was increased/decreased in
the beginning after the engine speed was reduced to
500 rpm, but it can be seen that the NOx 13
concentration was not changed much though the
torque was reduced 10 minutes after the
measurement was started. This seems to be because
the measured NOx concentration was reduced as
the torque was reduced, but the oxygen
concentration in the combustion gas was increased
by the increase in the excess air factor and the NOx
13 concentration was
increased. The NOx concentration
February 1998
was changed between 900- 1050 ppm from the
ENG. S/B to the engine stop on the whole.
The CO2 concentration is increased/decreased in
the range of 4-6% following the increase/decrease
of the torque in about 10 minutes after
measurement,
and
thereafter,
the
CO2
concentration is fluctuated in the slightly higher
level of around 5% irrespective of the fluctuation
torque of low level. The CO concentration is in the
opposite relation-ship to the torque, and the CO
emission concentration is increased as the output is
reduced, and distributed in the range of 30- 110
ppm.
b) In Departure
The data in departure are shown in Figs. 3-7(a)-(d).
The figures show that the PPA is increased while
the engine speed is kept constant at 500 rpm
immediately after the measurement is started, and
the engine speed is increased to 673 rpm while PPA
is kept constant 20 minutes after the measurement.
The excess air factor was reduced from 6 to 2.7 as
the torque was increased in the similar manner to
that in arrival until the engine speed was increased.
Then, the engine speed was increased up to the
normal engine speed while PPA was kept constant
at 19 degrees, and the excess air factor
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6
Osami Nishida, Tomohisa Kiuchi, Hirotsugu Fujita, Wataru Harano, Wataru Adati,
Keisuke Kadowaki, Masahiro Taguti, Manami Morioka, Mituaki Kato
keeps an approximately constant value of 2.7. This
corresponds to the fact that the excess air factor in the
propulsion performance test is more than 15 kNm in
torque, and little changed.
Though the NOx 13 concentration is increased as the
torque is increased by the increase in PPA, the NOx 13
concentration indicates the downward trend to the
torque increase as the engine speed is increased.
Because the excess air factor is little changed in this
condition, the downward trend of the NOx 13
concentration seems to be attributable to reduction of
the combustion time in the cylinder. Though the NOx 13
concentration reaches the maximum value of l080 ppm
while the engine is operated from the ENG. S/B
condition to the normal operating condition, the NOx 13
concentmtion is reduced as the engine speed is increased,
and keeps an approximately constant value of 900 ppm.
The CO2 concentmtion is increased as the torque is
increased, and stable at about 6.27o in the normal
operating condition. It is also proved that the CO2
concentration is little affected by the engine speed.
(6)
The CO concentration is temporarily increased after the
engine is started, but then reduced as the torque is
increased, and stable at about 100 ppm in the normal
condition.
3.3 Comparison between Propulsion Performance
Test and Arriva1/Departure
It is shown from either the data in the propulsion
performance test or the data in arrival/departure that
PPA, i.e., the increase in the torque affects the increase
in the NOx 13 concentration if the engine speed is
constant. The NOx 13 concentration indicates the
in-creasing trend by reducing the engine speed, which is
seemingly caused by the increase in the thermal NOx
accompanied by the increase in the combustion time
because little fluctuation of the excess air factor due to
the increase in the engine speed is found with the same
torque .
The CO2 concentration is little affected by the
engine speed, and increased when the torque is
in-creased. The CO2 concentration becomes the
maximum value of 6% in arrival/departure condition
and 6.3% in the normal operation.
Bulletin of the M.E.S.J., Vol. 26, No.1
Marine NOx and COx Emissions under Various Operating Conditions
The CO concentration is neither affected by the
engine speed similar to the CO2 concentration, and
indicates the reducing trend as the torque is increased.
4.
Conclusion
The report mainly indicates the measured data on
the NO, NO2, CO, and CO2 emission concentration
during the propulsion performance test and in arrival/
departure at Seto Inland Sea in summer. The results can
be summarized as follows.
( 1) The NO and NO2 emission concentration is increased as the engine torque is increased and the
engine speed is reduced. Seemingly this is be-cause
the NOx generation is increased by the increase in
the absolute time of combustion as the engine speed
is smaller.
(2) The maximum value of the NOx 13 concentration
during this navigation was about l080 ppm. The
NO2 concentration is about 10-15% of the NO
concentration.
(3) The CO2 emission concentration is increased and
the CO emission concentration is reduced as the
torque is increased when the excess air factor
exceeds 2.3. When the excess air factor is below
2.3, the oxygen becomes insufficient by reducing
the excess air factor to advance the reaction to CO.
The CO2 emission concentration is below
6.5%,while the CO emission concentration is below
about 150 ppm.
February 1998
7
References
1) Kazuhiko OGATA, et. al., Proceedings of 53
M.E.S.J. Conference, ( 1990-May), P.6- 11.
2) Osami NISHIDA, et. al., Review of Kobe University of Mercantile Marine Part II, Maritime studies,
and Science and Engineering, No. 43 ( 1995-Oct.),
P. 1- 10.
3) Kazuhiko OGATA, et. al., Proceedings of 1st
MESJ/Japan & Taiwan Joint Conference,
( 1995-Nov.), P.7- 14.
4) Osami NISHIDA, et. al., Proceedings of 3rd
KUMM Conference, ( 1995-June), P. 19-25.
5) Osami NISHIDA,et. al.,Proceedings of 5th ISME,
YOKOHAMA '95 ( 1995-July), P.469-476.
6) Osami NISHIDA, et. al., Proceedings of
MARIENV '95, vol. 2, SNAJ ( 1995-Sept.), P.8 17823.
7) M.E.S.J, SpecialConference,Proceedings ofTechnical Meeting ( 1992- 1994) for Suppress of Marine
Air Pollution, ( 1995 -May).
(7)