LAUSR

Abstract In this study, a four-stroke, high-speed spark ignition (SI) engine was conducted to reflect the effects of n-butanol blend ratio, spark timing and lambda. The experiments were conducted with four types of fuels including B0 (0 vol% n-butanol and 100 vol% gasoline), B10, B20 and B30, two operation conditions including the engine speed of 4000 r/min and 8000 r/min, the throttle position of 35% and 45%, respectively; with the spark timing range from 25° to 48° before top dead center (BTDC), and the lambda range from 0.85 to 1.5. The results demonstrate that with the increasing of n-butanol blend ratio, the fuel mass flow rate is increased when the lambda is fixed. The output power, brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) increase with increasing n-butanol ratio. The addition of n-butanol to gasoline can decrease nitric oxide (NO) emissions significantly but increase carbon monoxide (CO) emissions slightly. The lambda relative to the maximum BTE, the minimum BSFC and the maximum combustion efficiency become larger with the content of n-butanol increase. The data of engine parameters were normalized, and a calculation formula of weighted analysis for the engine performance was presented. With the n-butanol blend ratio increasing, the test engine has a better performance. Considering the emissions, the spark timing of the highest weighted normalized score (WNS) is retarded relative to maximum brake power (MBP) timing, and the lambda of the highest WNS becomes larger.