Effect of gasoline homogeneous charge compression ignition on engine acoustics and vibration

Abstract

The homogeneous charge compression ignition (HCCI) gasoline engine promises low fuel consumption without expensive NOx aftertreatment. Owing to the self-ignition, HCCI has a faster combustion and therefore a higher level of vibration and acoustic excitation than DI-spark ignition (SI) engines. To effect a gasoline engine running in HCCI mode, residual gases must be trapped in the combustion chamber in HCCI mode. One solution to trap residual gases is to establish a negative valve timing overlap. This was done on a gasoline I4 engine, which is able to run in SI or HCCI mode by using independently controlled overhead camshafts. Noise and vibration analysis has been carried out on such an HCCI engine to quantify the impact of HCCI on the combustion and intake orifice noise. The noise and vibration analysis was done using either directly measured noise and vibrations from the development dynamometer or a noise prediction method based on recorded cylinder pressures and known transfer functions. The investigations were carried out at different speed and load points while changing control parameters such as intake cam timing, throttle, spark and injection timing and strategy. Using different data evaluation methods it was found that the HCCI mode with base settings can deliver higher NVH excitation than the SI mode at the same speed and load. However, by applying different combinations of control parameters, the NVH of the HCCI operation mode can be controlled in order to reduce its level of excitation and noise characteristics.