两相流条件下的喷油系统中压力波时频特性的研究

Study on time-frequency characteristics of pressure wave of fuel injection system under condition of two-phase flow

利用W igner-V ille分布算法对液-汽两相流状态下的四冲程柴油机喷油系统中的压力波的时频特性进行了研究。研究结果表明:采用W igner-V ille分布算法进行分析时,可以更好地显示出液-汽两相流状态下的柴油机喷油系统中压力波在时间和频率范围内的能量密度,能更清晰地反映出这种非稳态信号频率随时间变化的关系。当喷油系统存在短时间存活汽泡时,其压力主波对应的频率较低,但能量密度比较大,而其压力次波具有一定量的高频率能量;当喷油系统存在长时间存活汽泡时,压力波的能量密度主要集中在主波上,除了低频率的能量外,还包含有相当一部分较高频率的能量。

Wigner-Ville distribution was used to study the time-frequency characteristics of pressure wave in fuel injection system of a four-stroke diesel engine under condition of liquid-gas tow-phase flow. The results show that using Wigner-Ville distribution the energy density of pressure wave of fuel injection system in time and frequency field could be better described and the change of frequency of this unstable signal with time could be better reflected. When short living time cavitation exists in fuel injection system, the frequencies of first pressure wave is lower, but their energy densities is higher, and second pressure has some high frequencies energies. When long living time cavitation exists in fuel injection system, energy densities of pressure waves concentrate mostly on first pressure wave, and low frequencies energies are expected, energy densities of pressure waves also involve some high frequencies energies.