Engine performance and emission characteristics of unmodified biodiesel fueled diesel engines are highly influenced by their ignition and combustion behavior. In this study, emission and combustion characteristics were studied when the engine operated using the different blends (B10, B20, B30, and B40) and normal diesel fuel (B0) as well as when varying the compression ratio from 16.5 : 1 to 17.5 : 1 to 18.5 : 1. The change of compression ratio from 16.5 : 1 to 18.5 : 1 resulted in 27.1%, 27.29%, 26.38%, 28.48%, and 34.68% increase in cylinder pressure for the blends B0, B10, B20, B30, and B40, respectively, at 75% of rated load conditions. Higher peak heat release rate increased by 23.19%, 14.03%, 26.32%, 21.87%, and 25.53% for the blends B0, B10, B20, B30, and B40, respectively, at 75% of rated load conditions, when compression ratio was increased from16.5 : 1 to 18.5 : 1. The delay period decreased by 21.26%, CO emission reduced by 14.28%, and
The world is presently confronted with the twin crises of fossil fuel depletion and environmental degradation. Indiscriminate extraction and lavish consumption of fossil fuels have led to reduction in underground-based carbon resources. The search for alternative fuels, which promise a harmonious correlation with sustainable development, energy conservation, efficiency, and environmental preservation, has become very important today. Intensive research is going on throughout the globe for a suitable diesel substitute. In this race among different alternatives, vegetable oils have attained primary place as some of their physical, chemical, and combustion related properties are nearly similar to those of diesel fuel. A lot of research work has been carried out to use vegetable oil in its neat form. Since India is net importer of vegetable oils, edible oils cannot be used for substitution of diesel fuel. So, major concentration has been focused on nonedible oils as the fuel alternative to diesel fuel.
Many efforts have been made by several researchers to use nonedible oil as an alternative fuel in CI engine. Nonedible oil from the plant seeds is the most promising alternative fuel for CI engine, because it is renewable, environment friendly, nontoxic, biodegradable, also has no sulphur and aromatics, and has favorable heating value and higher cetane number. Its chemical structure contains long chain saturated and unbranched hydrocarbons that are the most favorable property for the use in conventional diesel engine [
Available literature indicates that plant oils are possible alternative fuel for diesel engine. But it was reported that CI engines that run on plant oils achieve lower peak power and torque, as well as lower engine speeds, and these fuels cause injector coking, dilution of engine oil, and carbon deposits in various parts of the engine, filter clogging, and ring sticking, when it is used directly in an engine as a diesel substitute fuel [ cracking the plant oils, dilution of plant oils with diesel fuel, microemulsification, heating the plant oils before injecting into the combustion chamber, chemically transforming the plant oils to biodiesel by alcoholysis (transesterification).
Among these, chemically transforming the plant oils to biodiesel by alcoholysis (transesterification) was considered as the most suitable modification because technical properties of esters are nearly similar to diesel [
Biodiesel has a higher cetane number than petroleum diesel fuel, no aromatics, and no sulfur and contains 10% to 11% oxygen by weight [
In this study, a two-step “acid-base” process, that is, acid-pretreatment followed by main base-trans-esterification reaction using ethanol as reagent and H2SO4 as catalysts for acid and KOH for base reaction was followed to produce biodiesel from
Comparison of fuel properties of different fuels.
Fuel properties | Diesel | Jatropha oil | Ethyl Ester | Jatropha Ethyl Ester Blends | Test Method | |||
---|---|---|---|---|---|---|---|---|
B10 | B20 | B30 | B40 | |||||
Viscosity at 37°C, cS | 4.38 | 38.33 | 7.33 | 5.16 | 5.66 | 5.83 | 6.00 | D-445 |
Density at 37°C, g/cc | 0.832 | 0.931 | 0.875 | 0.843 | 0.850 | 0.856 | 0.861 | D-1298 |
Calorific value, MJ/kg | 42.90 | 32.62 | 35.77 | 41.47 | 40.39 | 39.52 | 39.08 | D-4868 |
Cloud Point, °C | 0.5 | 8 | 1.7 | 0.7 | 0.8 | 1.3 | 1.5 | D-2500 |
Pour point, °C | −7.8 | 4 | −2.8 | −7.2 | −6.8 | −6.8 | −5.3 | D-97 |
Flash Point, °C | 58 | 287.7 | 111.7 | 61.7 | 68.7 | 76.3 | 83.7 | D-93 |
A single cylinder, water cooled, 3.73 kW power, variable compression ratio engine was used for the test as shown in Figure
Brief specification of variable compression ratio (VCR) engine.
S. No. | Parameter | Specification |
---|---|---|
1 | Engine power | 5 HP |
2 | Engine speed | 1350 to 1600 rpm variable governed speed |
3 | Number of cylinders | One |
4 | Compression ratio | 5 : 1 to 20 : 1 |
5 | Bore, mm | 80 |
6 | Stroke, mm | 110 |
7 | Type of ignition | Spark ignition or compression ignition |
8 | Method of loading | Eddy current dynamometer |
9 | Method of starting | Manual crank start |
Schematic diagram of the experimental setup.
Nucon multigas analyzer was used to measure the concentration of carbon monoxide (CO) and nitric oxide (
The engine was evaluated using different fuel blends of Jatropha ethyl ester and diesel fuel at loads of 0% (no load), 25%, 50%, and 75% of rated load at compression ratio of 16.5 : 1, 17.5 : 1, and 18.5 : 1. The engine was warmed up prior to data acquisition. Initially the test engine was operated with base fuel diesel for about 10 minutes to attain the normal working temperature conditions. After that the baseline data was generated and the corresponding results were obtained. The engine was then operated with blends of Jatropha ethyl ester. During the tests with Jatropha ethyl ester blends, the engine was started with diesel until it was warmed up and then fuel was switched to various ester blends. After finishing the tests with diesel-ester blends, the engine was always switched back to diesel fuel and the engine was run until the ester blends had been purged from the fuel line, injection pump, and injector. This was done to prevent starting difficulties at the later time. Combustion and emission parameters such as peak pressure, heat release rate, ignition delay, and
Test matrix for combustion and emissions study on diesel engine.
Sr. No. | Variables | Types of variables studied | Details of variables studied |
---|---|---|---|
1 | Independent | ( |
B0, B10, B20, B30 and B40 |
( |
0, 25, 50 and 75 | ||
( |
16.5 : 1, 17.5 : 1, 18.5 : 1 | ||
|
|||
2 | Dependent | ( |
At 0%, 25%, 50%, 75% of rated load |
( |
At 0%, 25%, 50%, 75% of rated load | ||
( |
At 0%, 25%, 50%, 75% of rated load | ||
( |
At 0%, 25%, 50%, 75% of rated load | ||
( |
At 0%, 25%, 50%, 75% of rated load |
The heat release rate (HRR) is an important parameter to analyze the combustion phenomena in the engine cylinder. The important combustion phenomena parameters such as combustion duration and intensity can be easily estimated from the heat release rate diagram. The HRR diagram also provides key input parameters in the modeling of the
The combustion characteristics of the biodiesels can be compared by the means of cylinder gas pressure, heat release rate, and ignition delay.
Pressure versus crank angle for all fuels at 75% of rated load for various compression ratios.
The effect of the load on the cylinder pressure has also been investigated and the results are shown in Figure
Variation of peak cylinder pressure with engine load for all fuel at compression ratios of 16.5, 17.5, and 18.5, respectively.
Pressure versus crank angle for B0, B10, and B40 fuel at 75% of rated load for different compression ratios.
Comparison of the heat release rate for diesel and different ethyl ester blends at 75% of rated load for different compression ratios.
Figure
Ignition delay of fuel is a significant parameter in determining the knocking characteristics of C.I. engines. The cetane number of a fuel, which indicates the self-igniting capability, has a direct impact on ignition delay. The higher the cetane number, the shorter the ignition delay and vice versa. The ignition delay period was determined by the Engine Test Express’ software installed in computer attached to the engine.
Effect of engine load on the ignition delay period for diesel and ethyl ester blends at different compression ratios.
Effect of different compression ratios for B40 fuel at different load.
Variation of
Variation of
Variation of CO emission with engine load for diesel and all blends of Jatropha ethyl ester at different compression ratios.
Variation of CO emission with compression ratio for all blends at 75% of rated load conditions.
The combustion and emission characteristics of ethyl ester derived from The engine running with ester blends has produced higher peak heat release rate than the engine running with normal diesel at 75% of rated load conditions. In general, increasing the compression ratio improved the performance and cylinder pressure of the engine and had more benefits with ester blends than with diesel fuel. In spite of the slightly higher viscosity and lower volatility of ester blends, the ignition delay seems to be lower for ester blends than for diesel. On average, the delay period decreased by 21.26% for B40 blends at 75% of rated load conditions, when compression ratio was increased from 16.5 : 1 to 18.5 : 1. CO emission reduced by 14.28% and A practical conclusion can be drawn that all tested fuel blends can be used safely without any modification in engine. So blends of ethyl esters of Jatropha oil could be used successfully. On the whole it is concluded that Jatropha oil ester can be used as fuel in diesel engine by blending it with diesel fuel. Use of Jatropha oil can give better performance and reduced CO emission.
The authors declare that there is no conflict of interests regarding the publication of this paper.