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The world is confronted with the two major crisis namely, fossil fuel shortage and environmental degradation. The non edible vegetable oil and its methyl ester have been considered a promising option. In the present investigation, tests were carried out to analyze the combustion process of Rubber Seed Oil Methyl Ester (RSOME), Rubber Seed Oil (RSO) and compared with diesel. The engine performance and exhaust emissions were also studied for better understanding of the combustion process. It was observed that the premixed combustion phase of RSOME combustion was more intense than that of RSO due to its lower ignition delay. It was also noted that the ignition delay and combustion duration decreased with RSOME, which indicated higher heat release resulting in higher thermal efficiency than RSO. The brake thermal efficiency is 26.53% with RSO, 27.89% with RSOME and 29.93% with diesel at full load. The peak pressure increased by 2.3 bar for RSOME compared to that of RSO.

Vegetable oils can be directly used in compression ignition engines without any modification. A dual fuel engine was run using vegetable oils as primary and pilot fuels. Small quantities of orange oil were inducted along with air and ignited after compression by a pilot spray of Jatropha oil. The energy share of orange oil was varied till 35% of the total. Methyl ester of Jatropha oil and diesel were also used as pilot fuels for comparison. Dual fuel operation with orange oil induction reduced the smoke level and improved the thermal efficiency with all pilot fuels. However, hydrocarbon and carbon monoxide emissions were higher. Ignition delay was also increased. Methyl ester of Jatropha oil showed inferior performance than diesel. Performance with Jatropha oil was still inferior. On the whole it is concluded that the use of Jatropha oil and methyl ester of Jatropha oil as pilot fuels and orange oil as the inducted fuel will lead to reduced smoke levels and improved thermal efficiency.

Experiments were conducted to assess the relative effects of swirl (by using a masked intake valve and by providing swirl grooves on the piston crown) and squish on the performance, emission and combustion characteristics of a lean burn engine operating on liquefied petroleum gas (LPG) at a compression ratio of 10.5 under 20% and 100% throttle opening conditions. The swirl produced by the masked intake valve configuration at 100% throttle opening resulted in improved thermal efficiency and reduced HC emission, cyclic variations, ignition delay & combustion duration as compared to swirl groove piston and enhanced squish piston. The lean misfire limit was extended and there was no increase in the NO level at any given power output. At 20% throttle with high squish, under lean mixture conditions, combustion is even better than the masked valve configuration.

The main objective of the present research work is to utilise the higher amounts of exhaust energy of the LHR engines. Three vegetable oils(neem oil, rice bran oil and karanji oil) were tested in the low heat rejection engine. An electrical heater was used to heat the thick vegetable oils or the air and the results were studied. the electrical heater energy was correlated with the energy available in the exhaust of the LHR engine, so that the electrical heater can be replaced by a heat exchanger in the actual engine. The three vegetable oils, without heating, indicated a lower brake thermal efficiency of 1-4% when compared with the standard diesel engine. When these thick vegetable oils are heated and used in LHR engines the brake thermal efficiency improves. For every vegetable oil, there is an optimum temperature at which it gives the best performance.

As alternate fuels, ethyl and methyl alcohols stand out because of the feasibility of producing them in bulk from plentifully available raw materials. In the present work, methanol is used as the only fuel, in a Low Heat Rejection(LHR) engine by adapting three different methods. In the first method, methanol as the sole fuel was used in the LHR engine with a ceramic glowplug and in the second spark plug assistance was used to initiate combustion of the injected methanol. In the third method, methanol was used as the sole fuel in a LHR engine by a new method in which part of the methanol fuel was inducted through a heated inlet manifold using a carburetor and another part of methanol (with 1% castor oil for lubrication) was injected through the normal injector. With inducted methanol air charge temperature at 70 C and above the engine operated smoothly.

Use of vegetable oils in diesel engines results in increased smoke and reduced brake thermal efficiency. Dual fuel engines can use a wide range of fuels and yet operate with low smoke emissions and high thermal efficiency. In this work, a single cylinder diesel engine was converted to use vegetable oil (Jatropha oil) as the pilot fuel and methanol as the inducted primary fuel. Tests were conducted at 1500 rev/min and full load. Different quantities of methanol and Jatropha oil were used. Results of experiments with diesel as the pilot fuel and methanol as the primary fuel were used for comparison. Brake thermal efficiency increased in the dual fuel mode when both Jatropha oil and diesel were used as pilot fuels. The maximum brake thermal efficiency was 30.6% with Jatropha oil and 32.8% with diesel. Smoke was drastically reduced from 4.4 BSU with pure Jatropha oil operation to 1.6 BSU in the dual fuel mode.

As alternate fuels, ethyl and methyl alcohols stand out because of the feasibility of producing them in bulk from plentifully available raw materials. In the present work, ethanol is used as the only fuel, in the standard and Low Heat Rejection(LHR) diesel engines by adopting three different methods. In the first method, ethanol as the sole fuel was used in the LHR engine with normal metal glowplug and in the second method spark plug assistance was used to initiate combustion. In the third method, ethanol was used as the sole fuel in a LHR engine and a ceramic glow plug was used to initiate combustion. The engine was tested for performance and emissions for the above three methods of 100% ethanol operation in both the standard and LHR diesel engine and the results are compared. The spark plug assisted ethanol operation in the LHR engine gave the highest brake thermal efficiency and the lowest emissions.

In the context of fossil fuel crisis and ever increasing vehicle population, the search for alternative fuel has become necessary. Vegetable oil can be used as an alternative fuel for the diesel engine operation. How ever, engine performance is inferior to diesel due to their higher viscosity. The higher viscosity of vegetable oil causes improper atomization of fuel during injection resulting in incomplete combustion. This leads to smoky exhaust in a diesel engine. While pre-heating of vegetable oil, it was found that viscosity reduces exponentially with temperature. The high temperature of the exhaust, which is otherwise wasted, can be used to preheat the vegetable oil. For this purpose a heat exchanger has to be designed. It was observed that the rubber seed oil (RSO) requires a heating temperature of 155°C to bring down its viscosity to that of diesel.

Use of methanol and ethanol in conventional diesel engines is associated with problems on account of the high self ignition temperature of these fuels. The Hot Surface Ignition (HSI) method wherein a part of the injected fuel is made to touch an electrically heated hot surface for ignition, is an effective way of utilizing these fuels in conventional diesel engines. In the present work two types of HSI engines, one using a large ceramic base and the other using a conventional glowplug were developed. These engines were tested with methanol, M.spirit (about 90 % methanol and 10 % ethanol) and diesel. The results of performance, fuel economy emissions and combustion parameters including heat release rates for these fuels with both the types of HSI engines are presented. Diesel engines are commonly used as primemovers in the mass transportation and agricultural sectors because of their high brake thermal efficiency and reliability.

The performance of a conventional, carbureted, two-stroke spark-ignition (SI) engine can be improved by providing moderate thermal insulation in the combustion chamber. This will help to improve the vaporization characteristics in particular at part load and medium loads with gasoline fuel and high-latent-heat fuels such as methanol. In the present investigation, the combustion chamber surface was coated with a 0.5-mm thickness of partially stabilized zirconia, and experiments were carried out in a single-cylinder, two-stroke SI engine with gasoline and methanol as fuels. Test results indicate that with gasoline as a fuel, the thin ceramic-coated combustion chamber improves the part load to medium load operation considerably, but it affects the performance at higher speeds and at higher loads to the extent of knock and loss of brake power by about 18%. However, with methanol as a fuel, the performance is better under most of the operating range and free from knock.

A combustion engine of a given displacement will develop less power when running on hydrogen compared to gasoline or natural gas operation due to less heating value of the fuel air mixture in the combustion chamber. This drop in output exists for external mixing of hydrogen and air prior to intake valve closure. However, external mixing does not require intricate engine modification. Without substantial investment, supercharging is an effective method to increase the output of a hydrogen engine which uses the simple technique of external mixing of hydrogen and air. AVL stationary type research engine was used to investigate the percentage gain in output and thermal efficiency, knock limited combustion air ratios, NO emission and combustion characteristics at different supercharging pressures. The performance of the supercharged hydrogen engine is also compared with that of naturally aspirated hydrogen engine.

A diesel engine was operated with karanja oil, bio-diesel obtained from karanja oil (BDK) and diesel as pilot fuels while LPG was used as primary fuel. LPG supply was varied from zero to the maximum value that the engine could tolerate. The engine output was kept at different constant levels of 25%, 50%, 75% and 100% of full load. The thermal efficiency improved at high loads. Smoke level was reduced drastically at all loads. CO and HC levels were reduced at full load. There was a slight increase in the NO level. Combustion parameters indicated an increase in the ignition delay. Peak pressure and rate of pressure rise were not unfavorably affected. There was an increase in the peak heat release rate with LPG induction. The amount of LPG that could be tolerated with out knock at full load was 49%, 53% and 61% on energy basis with karanja oil, BDK and diesel as pilots.

The self-ignition temperature of alcohols is so high that abnormally high compression ratios would be required to use them in conventional diesel engines. This paper presents a novel approach of force igniting methanol or ethanol alone in a diesel engine at normal compression ratios. The well established proneness of methanol to pre-ignite in SI engine is made use of in the present method by employing a heated and insulated surface to initiate ignition. A conventional single cylinder diesel engine was modified to work on this principle. The engine operates satisfactorily at the rated speed (1500 RPM) on methanol and ethanol with thermal efficiencies comparable to the normal diesel engine of the same configuration. The operational experience further shows that it is possible to design a self-sustaining hot surface to initiate ignition. The engine also exhibits multi-fuel capability. A new direction for the use of methanol in diesel engines can follow from this technique.

The use of alcohol-gasoline blends enables the favorable features of alcohols to be utilized in spark ignition (SI) engines while avoiding the shortcomings of their application as straight fuels. Eucalyptus and orange oils possess high octane values and are also good potential alternative fuels for SI engines. The high octane value of these fuels can enhance the octane value of the fuel when it is blended with low-octane gasoline. In the present work, 20 percent by volume of orange oil, eucalyptus oil, methanol and ethanol were blended separately with gasoline, and the performance, combustion and exhaust emission characteristics were evaluated at two different compression ratios. The phase separation problems arising from the alcohol-gasoline blends were minimized by adding eucalyptus oil as a co-solvent. Test results indicate that the compression ratio can be raised from 7.4 to 9 without any detrimental effect, due to the higher octane rating of the fuel blends.