Experimental study of combustion noise level in LTC engine

In recent years, promising methods have been used to increase thermal efficiency, reduce nitrogen oxide and particle matter, which can be described as an example of an ethanol fuelled HCCI engine. But despite the many benefits of these engines, they continue to face problems such as increasing carbon monoxide production, unburned hydrocarbon, and producing combustion noise at high loads. In this paper, one single cylinder, air cooled, direct injection Yanmar diesel engine is converted to HCCI engine fuelled with ethanol. With using 38 steady state HCCI operating points at 1550 RPM, the variation of operating, combustion parameters and air pollution were studied with combustion noise level (CNL). The results indicate that the maximum pressure rise rate at lower combustion noise (CNL <85) does not increase significantly, but with increasing the maximum pressure rise rate of 4 bar/cad, CNL increases dramatically and reaches to the vibrational range of 90 dB which produces combustion noise. Also, the maximum in-cylinder pressure at 1550 rpm is 62 bar, with a limit of combustion noise of less than 90 dB.