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The purpose of this study is to elucidate flame propagation behavior of homogeneous propane-air mixture under application of non-uniform electric field. A needle-shaped electrode was attached to the ceiling and a plate electrode was set at bottom of combustion chamber, so that the electric field was applied in the direction of the chamber's vertical axis. A homogeneous propane-air mixture was supplied at equivalence ratio of 1.0 and was ignited by leaser induced breakdown under atmospheric pressure and room temperature. It was found that the flame front and plate electrode were repelled each other and a thin air layer was formed between the flame and plate electrode when a relatively low positive DC non-uniform electric field was applied to the needle-shaped electrode. It might be thought that the induced current was generated in the flame front, so that the flame front and plate electrode repelled each other.

The purpose of this study is to explore an effect of the coconut oil methyl ester (CME) and vegetable oil methyl ester (VME) on a low compression ratio diesel engine performance. CME and VME were produced from coconut oil and vegetable oil with methanol, respectively. Vegetable oil was assumed to contain 60 wt.% of soybean oil and 40 wt.% rapeseed oil. The engine performance was measured in the steady operating condition at 3600 rpm of engine speed. The ignition timings of CME and VME were advanced and the maximum cylinder pressures of CME and VME were higher as compared with the diesel fuel at low compression ratio, because CME and VME consisted of medium chain fatty acid methyl esters. The ignitability of CME was superior to VME, because CME consisted of saturated fatty acid. The brake thermal efficiency of diesel fuel was slightly higher than CME and VME at any compression ratios.

Internal combustion engines today are required to achieve even higher efficiency and cleaner exhaust emissions. Currently, research interest is focused on premixed compression ignition (Homogeneous Charge Compression Ignition, HCCI) combustion. However, HCCI engines have no physical means of initiating ignition such as a spark plug or the fuel injection timing and quantity. Therefore, it is difficult to control the ignition timing. In addition, combustion occurs simultaneously at multiple sites in the combustion chamber. As a result, combustion takes place extremely rapidly especially in the high load region. That makes it difficult for the engine to operate stably at high loads. This study focused on the fuel composition as a possible means to solve these problems. The effect of using fuel blends on the HCCI operating region and combustion characteristics was investigated using a single-cylinder test engine.

The purpose of this study is to explore an effect of cooled-EGR on the diesel engine performance fueled with coconut-oil methyl ester (CME). The exhaust gas was cooled by the water at room temperature and was fed to the intake manifold, and the EGR rate was changed from 0 % to 30 % at every 10 %. The engine performances were measured at several EGR rates, fuel injection pressures and timings. Test fuels were CME and commercial diesel fuel. In the case of high EGR rate at which the compression ignition was deteriorated, the ignition timing of CME was always earlier than that of diesel fuel, therefore CME had good ignitability as compared with diesel fuel under EGR application. When the fuel injection pressure was increased at high EGR rate, the ignition delay was improved by the fuel atomization and air-fuel mixing effect.