26-12-2012, 12:42 PM
Application of Blend Fuels in a Diesel Engine
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Abstract
Experimental study has been carried out to analyze engine performance and emissions characteristics for diesel
engine using different blend fuels without any engine modifications. A total of four fuel samples, such as DF (100%
diesel fuel), JB5 (5% jatropha biodiesel and 95% DF), JB10 (10% JB and 90% DF) and J5W5 (5% JB, 5% waste
cooking oil and 90% DF) respectively were used in this study. Engine performance test was carried out at 100% load
keeping throttle 100% wide open with variable speeds of 1500 to 2400 rpm at an interval of 100 rpm. Whereas,
emission tests were carried out at 2300 rpm at 100% and 80% throttle position. As results of investigations, the
average torque reduction compared to DF for JB5, JB10 and J5W5 was found as 0.63%, 1.63% and 1.44% and
average power reduction was found as 0.67%, 1.66% and 1.54% respectively. Average increase in bsfc compared to
DF was observed as 0.54%, 1.0% JB10 and 1.14% for JB5, JB10 and J5W5 respectively. In case of engine exhaust
gas emissions, compared to DF average reduction in HC for JB5, JB10 and J5W5 at 2300 rpm and 100% throttle
position found as 8.96%, 11.25% and 12.50%, whereas, at 2300 and 80% throttle position, reduction was as 16.28%,
30.23% and 31.98% respectively. Average reduction in CO at 2300 rpm and 100% throttle position for JB5, JB10 and
J5W5 was found as 17.26%, 25.92% and 26.87%, whereas, at 80% throttle position, reduction was observed as
20.70%, 33.24% and 35.57%. Similarly, the reduction in CO2 compared to DF for JB5, JB10 and J5W5 at 2300 rpm
and 100% throttle position was as 12.10%, 20.51% and 24.91%, whereas, at 80% throttle position, reductions was
observed as 5.98%, 10.38% and 18.49% respectively. However, some NOx emissions were increased for all blend
fuels compared to DF. In case of noise emission, sound level for all blend fuels was reduced compared to DF. It can
be concluded that JB5, JB10 and J5W5 can be used in diesel engines without any engine modifications However,
W5B5 produced some better results when compared to JB10.
Introduction
Unlimited use of the fossil fuels has led to global environmental degradation and health hazards.
Reduction in engine emissions becomes a major task in engine development due to the increasing concern
of environmental protection and more stringent emission norms. In addition to this more efforts are
needed to reduce dependence on the petroleum fuels as it is obtained from limited reserves [1]. It has been
reported by the US department of energy that the world’s oil supply will reach its maximum production
and midpoint of depletion sometime around the year 2020 [2]. Legislations have been passed in many
countries, requiring diesel to contain a minimum percentage of biofuels. The Czech Republic proved to be
the best, which insisted on 100% biofuel use for transportation [3]. The attractive characteristics of
biodiesel include higher cetane number, non-toxic emissions, bio-degradability, absence of sulphur and
aromatic compounds and excellent lubricity [4]. Biodiesel is the fuel that can be produced from straight
vegetable oils, edible and non-edible, recycled waste vegetable oils, and animal fat [5].
To evaluate the engine performance of different biodiesel blends, several experimental studies have
been carried out around the world. Generally a slight power loss, reduction in torque and increased brake
specific fuel consumption (bsfc) were observed in case of biodiesel fuelled engines. Besides it reduces the
emissions of carbon monoxide (CO), hydrocarbon (HC), sulfur dioxide (SO2), polycyclic aromatic
hydrocarbons (PAH), nitric polycyclic aromatic hydrocarbons (nPAH) and particulate matter (PM).
However, a majority of research results have indicated an increase in nitrogen oxides (NOx) [6,8].
According to the study [7] conducted on six cylinders DI diesel engine, increase of biodiesel percentage
in the blend involves a slight decrease of both power and torque. In particular, with pure biodiesel there
was a reduction by about 3% maximum power and about 5% of maximum torque. Similar results were
reported by Aydin and Bayindir [9] using cottonseed oil methyl ester (CSOME). However, a decrease of
CO, NOx and SO2 emissions were observed in the same study. In many countries, the use of edible oil to
produce biodiesel is not feasible due to a big gap in the demand and supply of such oils for dietary
consumption.
Experimental setup and experiments
The present study is conducted on an engine installed in the heat engine laboratory of Mechanical
Engineering Department at University of Malaya. The essential fuel properties are given in the Table 1.
The experimental setup is shown in Fig. 1. A one-cylinder, four-stroke diesel engine is selected and is
mounted on a test-bed. Its major specifications are shown in Table 2. Two fuel tanks, one for DF and
another for blend fuels were used for supplying the fuels to the test engine. The engine is coupled to an
eddy current dynamometer. It can be operated at a maximum power of 20 kW at 2450 to 10000 rpm. The
engine was first fuelled with DF to determine the baseline parameters and then, it was fuelled with blend
fuels. In order to calculate mean values, each test was repeated three times.
Engine performance parameters have been measured are engine torque, brake power, and brake
specific fuel consumption (bsfc). In this regard, test procedure was carried out to run a single cylinder
diesel engine through DYNOMAX 2000 data control system. In order to carry out the performance test,
engine was run at 100% load keeping throttle 100% wide open. Engine test conditions were monitored by
Dynomax-2000 software. All engine performance data were measured at “Step RPM Test” mode
(between 1500 and 2400 rpm with intervals of 100 rpm conditions). To examine the emission
characteristics, a portable BOSCH exhaust gas analyzer (model ETT 0.08.36) was used to measure the
concentration of exhaust gases of the test engine such as hydrocarbon (HC) in part per million (ppm)
while carbon monoxide (CO) and carbon dioxide (CO2) in percentage volume (%vol). While NOX
emission was measured using AVL 4000 (Make: Graz/Austria) gas analyzer. The emissions of different
pollutants were measured at 2300 rpm at 100% and 80% throttle position.
Noise Emission
The noise emission is different from that of air pollutants or other climate gases, as noise effects are
restricted to the time of emission. The combustion noise is associated with the maximum pressure rise
rate produced in the cylinder. Thus, higher pressure rise rate produces higher combustion noise and vice
versa. The maximum pressure rise rate (dp/dӨ) can be decreased with the reduction in the ignition delay
period so the engine will be running more smoothly [21]. Shorter ignition delay reports for biodiesel and
blends have been investigated by many authors [22-23].The sound level at different directions using
different blend fuels and DF in the engine showed that among all the directions (front, rear, left right and
top), only front side from each fuel sample produced the highest level of the sound. Therefore in Fig. 4,
only front side has been selected. Generally, Fig. 4 shows that the sound level for all blend fuels is
decreased when compared to DF and increased as the load (bmep) increased for each fuel sample tested.
Conclusion
In this work, the engine performance and emissions of using blend fuels such as JB5, JB10 and J5W5
were investigated and compared with diesel fuel:
Engine torque and brake power for blend fuels were decreased when compared to diesel fuel, mainly
due to their respective lower heating values. However, J5W5 showed lower reduction compared to JB10.
The bsfc values for blend fuels were higher than that of DF due to lower heating values and higher
densities. It is also noted that at some lower engine speeds, the bsfc values for blend fuels were found
lower than that of DF because of the improved combustion due to the inherently oxygen containing.
In case of engine exhaust gas emissions, reduction in HC, CO and CO2 were found for JB5, JB10 and
J5W5 when compared to DF at both engine operating conditions. Whereas, NOx emission for all blend
fuels was increased as compared to DF.