高阶导数物理不失真的发动机缸压曲线光顺方法

A physically undistorted smoothing method for higher derivatives of engine cylinder pressure curve

发动机气缸压力随曲轴转角的变化规律是发动机燃烧过程分析的重要依据,气缸压力关于曲轴转角的高阶导数蕴含了更深层次的热力过程信息。由于测量噪声的影响,直接从测量的气缸压力获取的2阶以上的导数往往淹没在噪声里,无法获取有效信息。以高斯曲线作为基函数,将气缸压力曲线的高阶导数的极值点数目作为约束,提出一种保持高阶导数物理不失真的发动机气缸压力曲线光顺方法。研究结果表明,所建立的方法能够获取气缸压力关于曲轴转角的4阶导数,为应用高阶导数分析发动机缸内热力过程提供了支持。

The variation of the engine cylinder pressure with crankshaft angle was an important basis for engine combustion process analysis.The higher derivatives of cylinder pressure with respect to crankshaft angle contains profound information about the thermal process.Because of measurement errors,the derivatives beyond second order calculated directly from the measured cylinder pressure was often submerged in the noise.A method for engine cylinder pressure smoothing was proposed with Gaussian function as the basis and the number of extreme points of the higher derivatives as the constraints.The results showed that the proposed method could obtain the fourth order derivatives of cylinder pressure with respect to crankshaft angle without violation to real physical trends.It provided a novel method for the application of higher derivatives in analyzing the thermal process in the engine cylinder.