为揭示船用长冲程低速柴油机健康状态下的振动特征,采用小波包能量谱(Wavelet Packet Energy Spectrum,WPES)和改进的总体平均经验模态分解(Modified Ensemble Empirical Mode Decomposition,MEEMD)结合的特征提取方法,对典型推进工况下低速机的表面振动信号进行3层小波包分解和重构.通过对能量占比较大的节点采用MEEMD方法进行分解,获得IMF1分量频谱.研究结果表明,在40％以下的较低发动机负荷时,各单次燃烧循环的振动波动较小,振动幅值基本一致.提升至50％以上发动机负荷时,燃烧引起振动波动明显增强.50％工况下,中高频能量占总能量的41.51％,为主要振动源.
Research on marine main engine vibration based on WPES and MEEMD
To reveal the vibration characteristics of marine long-stroke low-speed diesel engines under healthy condi-tions,a combination of wavelet packet energy spectrum(WPES)and modified ensemble empirical mode decomposition(MEEMD)was used to extract features for the three-layer wavelet packet decomposition and reconstruction of the surface vi-bration signals of the low-speed engine under propulsion conditions.The IMF 1 component spectrum was obtained by de-composing the nodes with larger energy dominance using MEEMD method.The results show that at lower engine loads be-low 40％,the vibration fluctuations of each single combustion cycle are small and the vibration amplitude is basically the same.When the engine load is raised to more than 50％,the vibration fluctuation caused by combustion is significantly en-hanced.41.51％of the total energy is in the medium and high frequency at 50％working condition,which is the main vibra-tion source.
marine low-speed diesel enginewavelet packet energy spectrumMEEMDvibration characteristicscondition monitoring
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