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A premixed charge compression ignition methanol engine targeting a drastic decrease in NOx emissions and a brake specific energy consumption equivalent to that of a DI diesel engine has been developed (1). The problems of this combustion system are that the brake thermal efficiency decreases, and CO and THC emissions increase due to a deterioration of high load combustion. The purpose of this study is to improve the high load combustion of a premixed charge compression ignition methanol engine using a flash boiling fuel injection technique. The results of this study have shown that the premixed charge compression ignition methanol combustion system using a flash boiling fuel injection technique increases the brake thermal efficiency, decreases CO and THC emissions, while maintaining low NOx emissions in the high load region.

A new combustion system targeting a drastic decrease in NOx emission and a brake specific energy consumption equivalent to that of a DI diesel engine has been developed. In this new combustion system, a lean burn system using early injection was employed to reduce NOx emission and an auto-ignition DI engine system was employed to achieve the low energy consumption. Methanol was used as the fuel for reducing NOx emission. The objective of this study is to clarify the possibility of the system for the auto-ignition of a premixed lean mixture of methanol fuel. This study shows that the gas temperature at ignition, Tig, is the predominant factor affecting auto-ignition. Auto-ignition occurs when Tig exceeds approximately 1000K. The methanol lean burn system in an auto-ignition DI engine drastically decreased NOx emission with almost the same brake specific energy consumption as a diesel engine in the middle load region.

Although the exhaust gas in a heavy-duty methanol engine is an oxygen rich atmosphere, there is some unburned methanol in the exhaust gas. Then, NOx control concept using lean NOx catalyst with unburned methanol as the reducing agent is considered. The purpose of this study is to verify the capability of lean NOx catalyst to reduce NOx in actual methanol engine exhaust. It was found through synthetic gas tests that alumina catalysts are effective for NOx removal. It was also found through engine tests that the catalyst temperature range between 500 °C and 600 °C and space velocity of less than 20,000 1/hr are requirements for a high NOx conversion efficiency. Although NOx conversion efficiency decreased at full load engine condition, it could substantially promote NOx conversion efficiency to add methanol into the exhaust gas before the catalyst bed.