基于离散小波变换的二甲醚HCCI爆震试验

Experimental Analysis of Knock in a DME HCCI Engine Using Discrete Wavelet Transform

在一台由柴油机改造为二甲醚进气道喷射的发动机上,用离散小波变换分析正常燃烧工况、爆震工况的缸内压力,计算其在各尺度细节部分的能量特征值,研究二甲醚HCCI燃烧的爆震特性。结果表明,正常燃烧工况、爆震工况缸内压力的能量特征值分布具有明显的规律。正常燃烧工况时,细节部分D3的能量特征值最大;爆震工况时,细节部分D1的能量特征值最大。转速升高或进气道喷射燃料添加LPG对正常燃烧工况、爆震工况缸内压力能量特征值的分布无影响,爆震强度决定能量特征值的分布。爆震强度越大,D1的能量特征值越大。根据各尺度细节部分D1、D2和D3的能量特征值可检测爆震。

An experimental analysis of HCCI by port injection of DME was carried out on an engine retrofitted from a diesel engine. The in-cylinder pressure with and without knock were processed by discrete wavelet transform. Wavelet energy of different levels were calculated and analyzed to obtain DME knock characteristics. The analysis shows that the energy distributions with and without knock display different characteristic. Without knock, the energy value of the detail D3 at level 3 is the largest, and the value of the detail D1 at level 1 is the largest with knock. With the increase of engine speed, or adding LPG into DME injected in the port have little effects on energy distributions. The knock intensity, however, plays a key role in determining their distribution. The more intensified the knock is, the larger the energy values of D1 goes. The energy value of D1, D2 and D3 can be used to detect knock.