=Paper=
{{Paper
|id=Vol-452/paper-17
|storemode=property
|title=Soot reduction from the combustion of 30% rapeseed oil blend in a HSDI Diesel engine
|pdfUrl=https://ceur-ws.org/Vol-452/paper17.pdf
|volume=Vol-452
}}
==Soot reduction from the combustion of 30% rapeseed oil blend in a HSDI Diesel engine==
https://ceur-ws.org/Vol-452/paper17.pdf
Soot reduction from the combustion of 30% rapeseed oil blend in a HSDI diesel
engine
L. Labecki*, L.C. Ganippa
Centre for Advanced Powertrain and Fuels Research, School of Engineering and Design,
Brunel University, West London, UB8 3PH, UK
The use of rapeseed oil (RSO) in diesel engine results in a significant reduction of NO x emissions but the soot that is
emitted from the combustion of RSO are several orders of magnitude higher compared to that of diesel. In this study
an attempt has been made to reduce the soot that is emitted from the combustion of RSO in diesel engine to take
advantage of their lower NOx emissions. This was achieved by using blends of RSO, and the soot emission from the
blend of 30% RSO was reduced to diesel equivalent levels of soot by varying the fuel injection parameters. By oper-
ating RSO blend under diesel equivalent levels of soot a further reduction in NO x emission was achieved.
Introduction given in [5-8], and it has been shown that by heat-
The internal combustion engines fueled by ing the fuel to temperatures between 70 - 80 °C
fossil fuels are one of the main sources of CO2 and results in a reduction of about 3 to 4 times of its
other hazardous pollutants. Generally the fuels viscosity.
from renewable resources are beneficial from the In this work RSO and its blend of 30% in diesel
environmental point of view. As they are very ef- have been used as a fuel in a direct injection diesel
fective in reducing some of the harmful emissions, engine. The viscosity was lowered by blending and
which eventually reduces the concentration of CO 2 preheating the fuel by allowing it to pass through a
in the atmosphere and the global climate change. heat exchanger fitted in the fuel system.
In case of diesel engines, pure plant oils (PPO)/ From our previous work [9] it has been shown
straight vegetable oil (SVO) and biodiesel are used that NOx emissions can be effectively reduced up
as renewable sources of alternative fuels. to 30% by using RSO and its blends compare to
PPO/SVO and biodiesels are non-toxic, biode- that of diesel fuel. The attempt has been taken to
gradable, non-explosive and are safe during trans- reduce soot emissions to take an advantage of
port and storage due to their high self ignition tem- lower NOx emissions from RSO. In order to exploit
peratures. Generally PPO/SVO contains triglyce- the advantage of lower NOx emissions of RSO,
rides, where one molecule of glycerol has three experiments were carried out to reduce the soot
molecules of long chain fatty acids connected to emissions by varying the fuel injection parameters
each of OH glycerol group and the fatty acids of such as injection pressure and injection timing.
PPO are mainly mono-saturated 60-70% and di- The fuel injection pressure and the fuel injection
saturated 10-20% [1-2]. These glycerol’s can be timings were swept from 800 to 1200 bar and from
removed through transesterification process to 0 to 12 deg bTDC respectively to reduce the soot
form methyl-esters, which are commonly known as from RSO to obtain diesel equivalent soot and to
biodiesel [1-3]. The properties of biodiesel are simultaneously maintain lower NOx emissions.
very close to that of diesel, however PPO/SVO
have lower calorific value, lower cetane number Experimental setup
and viscosity about 10 to 12 times higher than that In this investigation a 4 cylinder, 16 valve high
of diesel, which leads to problems associated with speed direct injection diesel engine was used. The
cold flow, cold start, deposit formation in nozzle, engine is fully instrumented with sensors and de-
injector and into the combustion chamber. High vices which enables us to control the engine tor-
viscosity of SVO/PPO can be reduced through que, speed, injection parameters, in cylinder pres-
transesterification, blending and fuel preheating. sure, emissions and fuel consumption. Detailed
The transesterification process described above schematic of the experimental setup is shown in
offers reduction of viscosity thus the biodiesel can figure 1. The engine control software allows to
be used directly in diesel engines with very little control and change engine parameters such as
modifications. Blending of PPO/SVO with diesel injection pressure, injection timing and EGR rate
fuel also reduces the viscosity, however effective on a real time basis. The in-cylinder pressures
reduction in viscosity is possible only for low con- were measured using a Kistler pressure transducer
centration of PPO/SVO in diesel. It has been and the LabView software. The gaseous emissions
shown by Rakopoulos et al. [4] that only a small (CO, THC, NOx) were measured using a Horiba-
fraction (up to 20%) of SVO/PPO can be effectively Mexa gas analyzer. The smoke number was
used without any engine modifications. Preheating measured using an AVL smoke meter and the fuel
of PPO/SVO also lowers the viscosity of the plant consumption of diesel fuel was measured using an
oils. The viscosity characteristics of PPO/SVO are AVL fuel consumption meter, however the fuel
* Corresponding author: lukasz.labecki@brunel.ac.uk
Towards Clean Diesel Engines, TCDE2009
consumption of RSO was measured using a bu- NOx emissions are lowered by 18% and the soot
rette metering management. emissions increases by 355% compared to that of
diesel. Similarly by using a blend of 30% RSO in
diesel the NOx emissions are lowered by 12% and
the soot emissions increases by 122% compared
to that of diesel.
In order to utilize the advantage of lower NO x
emissions of 50% and 30% blends of RSO, differ-
ent fuel injection strategies were tried to reduce
their soot levels to that of diesel equivalent soot
when the engine is operated under standard en-
gine conditions (injection pressure of 800bar, injec-
tion timing of 9deg bTDC, 0% of EGR, engine
speed of 2000 rpm and engine load of 2.7 bar
BMEP).
Due to the limitations of the experimental op-
erating conditions diesel equivalent soot was not
Fig. 1: The schematic of experimental setup. achieved for 50% RSO but it was possible to re-
duce the soot from the blend of 30% RSO to diesel
As can be seen in figure 1 the engine fuel sys- equivalent soot as shown in figure 3.
tem is modified to use RSO. Modifications include Diesel 800 bar 30% RSO 1200 bar
additional tank, couple of 2-way valves and in-line 30% RSO 800 bar 30% RSO 1000 bar
30% RSO 1100 bar 30% RSO 1200 bar
heater/cooler. A temperature controller is used to
regulate the temperature of the heater/cooler to 0.24
maintain uniform temperature of the fuel. The tem- injection timing 0.22
Smoke number
perature of the RSO was measured at two points 800-1200 bar 0.2
in the fuel pipe line. The temperature T 2 was 0.18
measured at the upstream of the injector and it
was maintained at 70 °C during all runs for RSO. retarded injection 0.16
To avoid problems with cold flow and cold start, timing 0.14
the engine was started with diesel and then diesel level 0.12
switched to RSO and similarly before shutting 0.1
down, the engine was switched back to diesel fuel.
12 10 8 6 4 2 0
Injection timing, CAD bTDC
Results and discussions
The results of soot and NOx emissions for pure Fig. 3: Strategies adopted for achieving diesel equivalent
RSO and their blends in diesel fuel are described level of soot from 30% RSO in diesel.
in [9] and summarized in figure 2.
Diesel equivalent level of soot emissions for
RSO NOx Diesel NOx
RSO soot Diesel soot 30% RSO was achieved by increasing the injection
1200 0.8 pressure from 800 bar to 1200 bar and by retard-
ing injection timing from 9 deg bTDC to 3 deg
1000 bTDC. As could be seen in figure 4, column A cor-
Smoke number
0.6
800 responds to standard engine operating conditions
NOx, ppm
and column B corresponds to operating conditions
600 0.4 for diesel equivalent soot for 30% RSO (at 1200
400 bar and 3 deg bTDC, 0% EGR, 2000rpm, 2.7 bar
0.2 BMEP). Higher injection pressure causes better
200 atomization and formation of smaller fuel droplets
0 0 and at the same time higher entrainment of warm
air on to the liquid core enhances vaporization of
0 20 40 60 80 100 fuel droplets, which effectively lowers soot emis-
Percentage of RSO in blend
sions.
Fig. 2: The soot and NOx emissions for RSO, their
blends and diesel (summarized from [9])
It can be seen that the emissions of NOx de-
creases with increasing concentration of RSO in
the blend and on the contrary the smoke number
increase with higher concentration of RSO in the
blend. By using a blend of 50% RSO in diesel the
NOx (DF=915 ppm) BSFC (DF=328 g/kWh) diesel equivalent level of soot emissions for
SN (DF=0.11) CO (DF=305 ppm) 30% blend of RSO were achieved by simulta-
THC (DF=226 ppm) neously retardation the injection timing and by
15 300 increase the injection pressure.
Change in SN, CO, THC, %
A B reduction of NOx emissions by about 22% was
Change in NOx, BSFC, %
5 250
achieved for 30% blend of RSO under the op-
200 erating conditions of diesel equivalent soot.
-5 30% RSO blend can be successfully used in DI
150 diesel engine with low levels of NOx emissions
-15 the same and even lower soot emissions com-
100 pared to that of diesel.
-25 50
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Conclusions soya oil and their blends with diesel fuel in
In this work the advantage of lower NOx emis- HSDI diesel engine. Fuel (2009) (submitted).
sions for 30% blend of RSO in diesel was further
explored to reduce their soot emissions to diesel
equivalent levels through different fuel injection
strategies. The main findings are summarized as:
by using pure RSO and their blends the NO x
emissions are lowered compared to that of di-
esel fuel.