米勒循环汽油机燃烧噪声诊断与优化

Diagnosis and optimization on combustion noise of a Miller cycle gasoline engine

对某搭载米勒循环增压汽油机的SUV在低速高负荷区域出现的“哒哒”异响进行诊断、分析及优化。噪声振动信号经傅里叶变换、滤波及燃烧压力频谱对比分析,确认异响为1~3.5 kHz的燃烧噪声。通过对米勒循环结构分析,确认异响产生根本原因为小升程进气凸轮进气时间短、阻力大和增压器低速性能不足,在低速中高负荷节气门全开下,采用了过大的点火提前角,导致气缸压力急剧升高诱发高压力升高率,带来燃烧噪声。通过对异响工况点火提前角优化,最高压力升高率及1~3.5 kHz燃烧压力频谱成分优化明显,异响消除,且发动机性能变化不大。

The"DaDa"abnormal noise of a SUV equipped with Miller cycle turbocharged gasoline engine in low speed,high load area was studied.Through Fourier transformation,filtering of the noise and vibration signal and comparison analysis of cylinder pressure spectrum,it is confirmed that the abnormal sound is 1-3.5 kHz combustion noise.Through structure analysis of the Miller cycle engine,it is found that the root cause is that high pressure rise rate caused by unreasonable advanced ignition angle under low speed and high load while throttle is fully open condition,because Miller cycle uses an inlet cam of small lift which caused short intake time and high resistance and the supercharger low-speed performance is insufficient.By optimizing the advanced ignition angle in the abnormal noise condition,the maximum pressure rise rate and 1-3.5 kHz cylinder pressure components are obviously optimized,the abnormal noise is eliminated,and the engine performance changes little.