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An air-cooled, four-stroke, 125 cc electronic gasoline fuel injection SI engine for motorcycles is altered to burn ethanol fuel. The effects of nozzle orifice size, fuel injection duration, spark timing and the excess air/ fuel ratio on engine power output, fuel and energy consumptions and engine exhaust emission levels are studied on an engine test bed. The results show that the maximum engine power output is increased by 5.4% and the maximum torque output is increased by 1.9% with the ethanol fuel in comparison with the baseline. At full load and 7000 r/min, HC emission is decreased by 38% and CO emission is decreased 46% on average over the whole engine speed range. However, NOx levels are increased to meet the maximum power output. The experiments of the spark timing show that the levels of HC and NOx emission are decreased markedly by the delay of spark timing.

This paper examines the diesel-ethanol dual fuel combustion at medium engine loads on a single-cylinder research diesel engine with a compression ratio of 16.5:1. The effect of exhaust gas recirculation (EGR) and ethanol energy ratio was investigated for the dual fuel combustion to achieve simultaneously ultra-low NOx and soot emissions. A medium ethanol ratio of about 0.6 was found suitable to meet the requirements for mixing enhancement and ignition control, which resulted in the lowest NOx and soot emissions among the tested ethanol ratios. A double-pilot injection strategy was found competent to lower the pressure rise rate owing to the reduced fuel quantity in the close-to-TDC injection. The advancement of pilot injection timing tended to reduce the CO and THC emissions, which is deemed beneficial for high EGR operations. The reactivity mutual-modulation between the diesel pilot and the background ethanol mixture was identified.

Gasoline homogeneous charge compression ignition (HCCI) can achieve high efficiency and extremely low NOX emissions. However, the working condition range of HCCI is limited by knock occurring during engine operation. To achieve an expanded HCCI working condition range, it is necessary to explore a method predicting knock cases accurately to avoid knock occurring. Based on a DI-HCCI engine with ethanol/gasoline mixed fuel, the knock cases under different conditions have been investigated. In-cylinder pressure signals are used to identify the knock cases and the knock oscillations are extracted with fast Fourier transform (FFT). The effects of the ethanol proportion in the fuel and air/fuel ratio on the characteristics of knock have been studied. The results have shown that the knock parameters, such as maximum frequency, start point angle and the duration, have close relationship with the knock intensity.