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The fuel crises of the 1970's and early 1980's focused attention on the desirability of developing alternative fuels and decreasing the dependency on petroleum-based fuels. Vegetable oils and derivatives are among the materials that were extensively investigated as alternative diesel fuels. Vegetable oils are a potential alternative to the partial or total substitution of diesel fuels. It was known that short-term engine tests have been successful with vegetable oils; however, long-term tests have revealed the fuel limitations regarding lubricating oil contamination, deposits on engine surfaces and performance problems. This study shows how the added advantages of air-cooled engine over the water-cooled engine become the preferred choice for the SVO run diesel engine. Based on the 100 hrs SVO run diesel engine, the modification has been carried out for the long run. Different emission measurements were carried out and studied in comparison with conventional diesel.

The performance and emission of spark ignition engines are optimized using combustion characteristics. The flame characteristics such as flame kernel growth rate, flame speed, flame development angle, rapid burning angle, over all burning angle and drift velocity influence the combustion process of SI engines. In this direction, experiments were conducted to measure flame kernel growth rate in AVL research spark ignition engine using AVL VISIO FEM instrument. The flame kernel growth rate measured at different engine speeds and spark timing. The measured flame kernel growth rate for gasoline fuel was in the range of 4 to 6 m/s. It was observed from the results that flame kernel growth rate is the highest at MBT spark timing. The effects of flame kernel growth rate on performance and emission characteristics were analyzed in detail. Brake thermal efficiency increases with the increase of flame growth rate. CO emission is good agreement with the kernel growth rate.

For several years, ethanol is being used in controlled but unmarked fashion (levels less than 5%) in gasoline worldwide. Several problems associated with ethanol have put a restriction in using gasoline-ethanol blends with higher ethanol percentage, as it is in an existing engine. Changed physico-chemical properties of high ethanol percentage gasoline blend needs several challenges to be overcome in order to harness the potential of high ethanol content in the blend. The present paper highlights the results of investigation carried out with three different ethanol-gasoline blends i.e 10, 30 and 70 % ethanol blended with gasoline (E10, E30 and E70 respectively). An electronically controlled online fuel blending mechanism was designed and developed to ensure correct blending of two fuels in desired percentage.

Biodiesel developed from non- edible seeds grown in the wasteland in India can be very effectively utilized in the existing diesel engines used for various applications. This paper presents the results of investigations carried out in studying the fuel properties of mahua oil methyl ester (MOME) and its blend with diesel from 20% to 80% by volume. These properties were found to be comparable to diesel and confirming to both the American and Indian standards. The performance of mahua biodiesel (MOME) and its blend with diesel in a Kirloskar DAF8 engine has been observed. The addition of MOME to diesel fuel has significantly reduced CO, UBHC and smoke emissions but increases the NOx emission slightly. The reductions in exhaust emissions could help in controlling air pollution. The results show that no significant power reduction in the engine operation when operated with blends of MOME and diesel fuel.

Estimation of the ignition delay and concentration of exhaust emissions carries great importance in engine development process. In direct injection (DI) diesel engines, ignition delay has direct effect on startability, noise and pollutant formation. Hydrocarbon (HC) emissions are mainly due to the unburnt or partially burnt fuel leaving the engine exhaust system. In the present work, correlations have been developed for ignition delay and HC emissions. Satisfactory comparison of predicted and experimental values of ignition delay and HC emission under different operating conditions for various engines, widely varying in dimensions, method of aspiration and rated speeds validated the correlations. These correlations are useful as design tools for engine development.

Exhaust gas recirculation (EGR) is an effective means to reduce NOx emissions in Diesel engines. An innovative concept of EGR admission was developed for diesel engine of heavy-duty application. A 4-cylinder, naturally aspirated, water-cooled engine was selected for experimental investigation. One-dimensional simulation software was used to predict emission and performance parameters. The engine model was initially validated with experimental data and then used for parametric study for EGR. The best EGR flow rates were determined for experimental study, to study the effect of EGR on engine emissions. A significant reduction in emissions of NOx with minimal increase in CO and HC emission was achieved. Based on number of experiments and simulations an innovative EGR system was developed to control flow of hot exhaust back into the intake manifold for NOx reduction.

In this study some experiments were carried out to evaluate fuel consumption and exhaust emissions of carbon monoxide (CO), oxides of nitrogen (NOx)) and hydrocarbons (HC) with compressed natural gas (CNG) and gasoline in a single cylinder engine. Compressed natural gas showed 3 to 5 percent higher thermal efficiency and 15 percent lower specific fuel consumption as compared to gasoline. Also CO emissions were lower by 30-80 percent in rich zone and NOx by about 12 percent at an equivalence of 1.0. At wide open throttle CNG operation resulted in 10 to 12 percent lower power output. However, thermal efficiency and brake specific fuel consumption (bsfc) was better with CNG as compared to gasoline. Dual spark plug operation increased power output by 3 to 5 percent.