压力示功图的频谱分析及其数字滤波处理

The Spectrum Property of Pressure Indicator Graph and Numerical Filtering Process

测压通道是影响柴油机示功图测量精度的主要因素之一，示功图上出现的压力波动直接影响到放热规律的计算和燃烧性能的评价。通常采用的光顺方法只是根据数学上的平滑与逼近原理，而不是按系统的物理特性建立的，很难证明其光顺结果是否符合实际。本文通过对SD2100型柴油机实测示功图的频谱特性的研究，提出了一种根据测压通道的传递函数，通过傅立叶逆变换消除示功图压力波动的滤波方法。与一般的光顺方法相比，它有效地消除了测压通道造成的压力波动，而更多地保留了示功图上的有用信息，是一种较好的示功图处理方法。

The existing of pressure measuring passage is the main factor of influencing measuring accuracy of indicator graph. The pressure oscillation of indicator graph can infltlence the calculation of release rate and the evaluation of combustion performances. Smooth method is generally used to process indicator,but it can't remove the oscillation of SD2100 diesel engine indicator graph. The author analyzes the pressure spectra of indicator graph,gives a method that is based on reverse Fourior transfer and transmission function to process indicator graph. This method can eliminate pressure oscillation that derives from pressure measuring passage. Obviously it is a good method for processing indicator graph.