自激振荡脉冲射流喷嘴装置系统频率特性理论研究

Frequency characteristics of self-excited oscillation pulsed jet nozzle device

根据相似系统原理和流体网络理论建立了自激振荡脉冲射流喷嘴装置的等效网络模型,利用系统传递函数推导了系统频率特性方程并进行了数值计算。结果表明:喷嘴装置的固有频率主要由喷嘴形状、结构参数、入口流速、射流中压力扰动波波速决定;自激振荡腔腔径、自激振荡腔腔长、上喷嘴直径、下喷嘴直径都对系统频率特性影响很大。提出了相应的自激振荡脉冲射流喷嘴设计准则,即喷嘴装置在最佳阻尼比下产生谐波共振。

The equivalent network model of the self-excited oscillation pulsed jet nozzle device is established according to the similarity principle and the fluid network theory. The system transfer function is employed to derive and to compute numerically the system frequency response. The results show that the natural frequency of this nozzle device is mainly determined by the shape of the nozzle, the structure parameters, the inlet flow velocity and the velocity of the pressure disturbance wave in jet flow. The inlet pressure of fluid, the self-excited oscillation cavity length, the diameters of upper and lower nozzles have a great influence on the system frequency response. There is a best range of the equipment structure parameters. The corresponding design criterion for the self-excited oscillation pulsed jet nozzle device is put forward, that is, the nozzle device produces the harmonic resonance under the best damping ratio.