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This paper discusses the experimental investigation of extended expansion and thermal insulation on the performance of a diesel engine. A single cylinder naturally aspirated air-cooled diesel engine is modified to run on the concept of extended expansion (Miller cycle). In the modified engine, the expansion ratio is maintained greater than the effective compression ratio by modulating the intake valve closing time and the clearance volume. The cylinder head, valve, and the piston top are coated with partially stabilized zirconia (PSZ) for low heat rejection. Results show a significant improvement in fuel efficiency of the insulated extended expansion engine. A ratio of expansion ratio to effective compression ratio of 1.5 is found to be optimum.

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.

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.

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.

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 this investigation the in-cylinder flow field structure was evaluated in a small displacement (50 CC) two-stroke spark-ignition engine using cylinders with Schnuerle-ports and a boost-port. A special hot-wire probe was designed, fabricated and calibrated for the use in this work. A constant temperature hot-wire anemometer was used for measurements. The effects of speed, throttle position and piston head shape were studied. The effect of compression ratio, silencer shape and inclusion of resonator to the engine induction and exhaust systems on the in-cylinder flow field activity in the Schnuerle-ported cylinder were analysed. The flow field conditions at different downward locations in the axial direction from the spark point were also evaluated in the Schnuerle-ported cylinder.

This paper deals with the experimental results of two engines - one single cylinder RDH - CFR engine with variable compression ratio and the other a four cylinder variable speed automotive type engine. The single cylinder emission results are projected for multicylinder operation and for a fixed maldistribution symmetry. The results show that there is a reduction in NOX emissions due to maldistribution where as UBF, CO and CH2O emissions are increased due to maldistribution.

A novel Air-Alcohol INDUCTOR with an inherent flexibility to tailor the alcohol flow rate, has been developed for a multi-cylinder, variable-speed, vehicular Diesel engine to enable operation in the Alcohol-Diesel bi-fuel mode. Tests have been carried out on the dynamometer over the whole speed range of the engine. Also road tests have been carried out under constant vehicular speed conditions. Upto 48% Diesel substitution was achieved on road without reduction in thermal efficiency. Laboratory tests indicate lower exhaust temperatures and lower smoke intensities than in the diesel mode.

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.