Application of wavelet packet energy spectrum method to study pressure pulsation in combustion chamber of ramjet

Ramjet is the main power unit of supersonic aircraft with air-breathing method, where the pressure pulsation of the combustion chamber is a significant type of media to assess the engine operating condition and check the noise source of the engine. This paper aims to process the pressure pulsation signals obtained from the combustion chamber based on wavelet packet decomposition (WPD). The original signals can be divided into several sections with different frequency bands. Besides, the information contained in the combustion chamber pressure signals are presented by series of high and low frequency components. Since each section of the divided signal owns some unique information, the WPD method is adopted to process the sub-section signals to extract the characterization of the engine. Then the energy spectrums are obtained, which are usefully used to select the key sub-section with most important features. The results show that the WPD method is important for the condition monitoring, aircraft noise environment prediction and reliability assessment of Ramjet.