基于Hartmann哨超声喷嘴的谐振腔结构仿真研究

Simulation Study on Resonant Cavity Structure based on Hartmann Whistle Ultrasonic Nozzles

为便于用试验方法研究汽轮机除湿问题,设计了一种新型大流量、高雾化度的喷嘴,在喷嘴设计中融入类似Hartmann哨的谐振腔结构,并通过超声波效应增强对水滴的雾化效果。采用Fluent流体仿真软件,对湿蒸汽环境下不同Hartmann哨谐振腔结构尺寸的流场速度、压力脉动以及谐振频率进行数值模拟,得到最佳谐振腔结构尺寸。研究结果表明:喷嘴入口压力一定时,改变谐振腔与喷嘴出口的角度(谐振腔夹角),速度脉动会随谐振腔夹角的增大而增大,而压力脉动随谐振腔夹角增大呈先增大后减小的趋势,在125°夹角下出现峰值;125°夹角下速度脉动最大值区域及谐振频率随谐振腔直径增大而减小;最终确定谐振腔的结构参数,其夹角为125°、直径为3.4 mm、深度为6.4 mm,该结构参数下谐振频率为21 kHz,符合所需频率。

In order to study the dehumidification problem of steam turbine by the expermiental method,a new type of nozzle with large flow rate and high atomization degree was designed,and a resonant cavity structure similar to Hartmann whistle was incorporated into the nozzle design,hoping to enhance the atomization effect of water droplets through the ultrasonic effect.The fluent fluid simulation software was used to numerically simulate the velocity,pressure pulsation and resonant frequency of the flow field under different Hartmann whistle resonant cavity structure sizes,and the optimal resonator layout structure size was obtained.The results show that when the nozzle inlet pressure is constant,changing the angle between the resonant cavity and the nozzle outlet(i.e.resonant cavity angle)increases the velocity pulsation with the increase of the resonant cavity angle,while the pressure pulsation increases first and then decreases with the increase of the resonant cavity angle,reaching a peak at an angle of 125°;the maximum velocity pulsation region and resonant frequency decreases with the increase of resonant cavity diameter;the structural parameters of the resonant cavity are finally determined that its angle is 125°,diameter is 3.4 mm and depth is 6.4 mm;the resonant frequency under this structure parameter is 21 kHz,which meets the required frequency.