基于小波包能熵谱的爆震特征频带及强度分析  

Frequency band and intensity analysis of knock characteristics based on wavelet packet energy entropy spectrum

作　　者：薛劲梓 胡春明[1,2] 刘娜[1] 赵英博 张建飞 XUE Jinzi;HU Chunming;LIU Na;ZHAO Yingbo;ZHANG Jianfei(Tianjin Internal Combustion Engine Research Institute,Tianjin University,Tianjin 300072,China;School of Mechanical Engineering,Tianjin University,Tianjin 300350,China)

机构地区：[1]天津大学内燃机研究所,天津300072 [2]天津大学机械工程学院,天津300350

出　　处：《中南大学学报（自然科学版）》2022年第6期2092-2101,共10页Journal of Central South University:Science and Technology

基　　金：国家自然科学基金资助项目(51476112)。

摘　　要：在1台航空煤油直喷发动机上进行爆震试验,然后基于小波包分解的方法提取缸内压力信号中不同频带的高频压力分量,计算其范数能量熵并组成小波包能熵谱,分析不同爆震强度工况下小波包能熵谱中的能量分布情况以探究点燃式发动机的爆震特征频带,最后提出一种新的爆震评价指标。研究结果表明:此台发动机的爆震产生的高频压力能量主要分布在4.6~16.5 kHz频带内,其中爆震特征频带分布在9.9~16.5 kHz,且此频带的能量随爆震强度增加而明显增大;基于研究结果将小波包能熵谱中各高频压力分量能量熵的最大值(the maximum ofentropy,MOE)作为新的爆震评价指标,且新的爆震评价指标MOE与用Siemens VDO算法得到的爆震因子(KF)相关系数在0.91以上,说明MOE能清晰地反映出不同强度等级的爆震工况;最后用受试者工作特性曲线(receiver operating characteristic,ROC)估计爆震阈值,在转速为3500 r/min、节气门开度为30%的工况下,将MOE为0.355作为爆震阈值最为合理。Based on the method of wavelet packet decomposition,the high frequency pressure components in different frequency bands of cylinder pressure signal were extracted,the norm energy entropy was calculated and the wavelet packet energy entropy spectrum was formed.The energy distribution in the wavelet packet energy entropy spectrum under different knock intensity conditions was analyzed to explore the characteristic frequency band of spark ignition engine,and a new knock evaluation index was proposed.The knock test was conducted on a direct injection engine fueled with aviation kerosene.The results show that the high-frequency pressure energy generated by knock is mainly distributed in the frequency band of 4.6−16.5 kHz,and the characteristic frequency band of this engine is 9.9−16.5 kHz,and the energy of this frequency band increases obviously with the increase of knock intensity.The maximum of entropy(MOE)of each high-frequency pressure component in the wavelet packet energy entropy spectrum is taken as a new knock evaluation index,and the correlation coefficient between MOE and knock factors(KF)calculated by Siemens VDO algorithm is more than 0.91,and can clearly reflect the detonation conditions of different intensity levels.Finally,the receiver operating characteristic(ROC)curve is used to estimate the knock threshold,and the MOE of 0.355 is the most reasonable knock threshold for this kerosene engine when the speed is 3500 r/min and the throttle opening is 30%.

关 键 词：点燃式煤油发动机 爆震强度评价 小波包分解 爆震特征频带 能熵谱 

分 类 号：V231.22[航空宇航科学与技术—航空宇航推进理论与工程] TK461[动力工程及工程热物理—动力机械及工程]