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A three-cylinder, with a bore of 68.5 mm port fuel injection, engine was adopted to study the combustion and emission characteristics of a methanol/gasoline-fueled engine during cold start and warm up. The cylinder pressure analysis indicates that engine combustion is improved with the methanol addition into gasoline. With the increase of the methanol fraction, the flame developing period and the fast burning period are shortened and the indicated mean effective pressures become higher during the first 50 cycles. Meanwhile, a novel quasi-instantaneous measurement system was designed to measure engine emissions during this process. With the increase of the methanol fraction (below 30%), the unburned hydrocarbon and carbon monoxide (CO) are decreased obviously. The measured results show that the hydrocarbon is reduced about 40% at 5 °C and 30% at 15 °C during the cold-start and warm-up period; CO is reduced nearly 70% when the engine is fueled with M30 (30% methanol in volume), and a higher difference in the exhaust gas temperature of about 140 °C is achieved at 200 s after starting than fueled with gasoline.

The effects of homogeneous charge compression ignition (HCCI) engine compression ratio on its combustion characteristics were studied experimentally on a modified TY1100 single cylinder engine fueled with dimethyl ether. The results show that dimethyl ether (DME) HCCI engine can work stably and can realize zero nitrogen oxides (NO x ) emission and smokeless combustion under the compression ratio of both 10.7 and 14. The combustion process has obvious two stage combustion characteristics at e = 10.7 (e refers to compression ratio), and the combustion beginning point is decided by the compression temperature, which varies very little with the engine load; the combustion beginning point is closely related to the engine load (concentration of mixture) with the increase in the compression temperature, and it moves forward versus crank angle with the increase in the engine load at e = 14; the combustion durations are shortened with the increase in the engine load under both compression ratios.Effects of compression ratio on the combustion characteristics of a homogeneous charge compression ignition engine

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