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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, 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 present work, investigations were carried out on a single cylinder, low compression ratio, spark-assisted low heat rejection D.I diesel engine. An extended electrode spark plug was used. Performance and emission tests on the engine were carried out with diesel fuel at two compression ratios, 10.5 and 12.5. In each case the engine was tested as a normal engine as well as a low heat rejection engine. The test results show that the low compression ratio spark assisted diesel engine operates very smoothly due to the low peak pressure and low rate of pressure rise. The low heat rejection spark assisted diesel engine gave an improved performance and reduced emissions compared to the normal baseline diesel engine.

This work demonstrates how the performance of a standard spark-assisted alcohol engine can be improved by using the Low Heat Rejection (LHR ) concept. The improved combustion is attained by better using the greater heat energy in the combustion chamber of a LHR engine - in this case for the faster vaporisation and better mixing of the alcohol fuels. For this program the LHR engine used has a single cylinder diesel and alcohols sued as sole fuels were ethanol and methanol. For spark assistance an extended electrode spark plug was used and location and projection were optimised for best results. These configurations were evaluated for performance and emissions with and without LHR implementation. The results show that the engine with LHR, ethanol fuel and spark assistance has the highest brake thermal efficiency with the lowest emissions.