Diesel engine combustion resonant frequency extraction method based on empirical wavelet and Hilbert transform

Abstract

The invention provides a diesel engine combustion resonant frequency extraction method based on empirical wavelet and Hilbert transform. The method comprises the following steps that: 1: carrying outFourier transform on a cylinder pressure signal to obtain a cylinder pressure frequency spectrum, utilizing a scale space algorithm in an empirical wavelet algorithm to identify characteristic sub-modality in the cylinder pressure frequency spectrum, determining the position of the sub-modality, and calculating the boundary frequency of the sub-modality; 2: constructing an empirical wavelet filter, utilizing the constructed wavelet filter to carry out band-pass filtering on the cylinder pressure signal, extracting a sub-modality signal corresponding to each piece of combustion fluctuation in the cylinder pressure frequency spectrum, and selecting the sub-modality with maximum oscillation energy as a combustion oscillation signal; and 3: carrying out the Hilbert transform on the combustionoscillation signal obtained in S2, drawing a Hilbert spectrum, and obtaining oscillation frequency and an oscillation amplitude corresponding to the oscillation frequency. The method has the advantages of good astringency, high adaptivity and high accuracy, and the obtained oscillation frequency can be used for the low-noise optimal design of the diesel engine and temperature and gas quality estimation in a cylinder.

Description

technical field [0001] The invention relates to a signal processing method, in particular to a method for extracting combustion resonance frequency of a diesel engine. Background technique [0002] The combustion resonance frequency of a diesel engine is an important parameter for low-noise optimization and thermal analysis of a diesel engine. In the design of the combustion chamber, the natural frequency of the combustion chamber can be kept away from the combustion resonance frequency by optimizing the structure of the combustion chamber, so that the combustion noise of the diesel engine can be greatly reduced. In addition, the combustion resonance frequency is also related to the temperature in the cylinder, and the gas mass in the cylinder can be calculated, so the accurate calculation of the resonance frequency is very important for the related research of diesel engines. [0003] The methods currently used to calculate the combustion resonance frequency of diesel engi...

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Problems solved by technology

However, because the short-time Fourier transform needs to properly select the size and type of the window function, the calculation accuracy of the resonance frequency will also be affected by this.

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