制冷剂两相流音速对引射器喷嘴结构的影响

Effect of sonic velocity of two-phase refrigerant fluid on structure of ejector nozzle

将液-液引射器内部的喷嘴作为研究对象,建立了喷嘴内气液两相流的非等熵膨胀模型和均相流音速模型.研究了制冷剂R134a和R22在不同喷嘴进出口压降条件下,喷嘴出口气液两相流音速的变化规律.模拟结果表明:随着喷嘴出口饱和温度的降低,喷嘴出口音速缓慢降低,而实际速度快速增大,喷嘴出口处R22的当地音速约为R134a当地音速的1.5倍;当喷嘴入口饱和温度为40℃时,R134a在喷嘴内实际膨胀过程的临界温度为14.5℃;对于高压液体作为工作流体的引射器,其喷嘴宜采用缩放型;当喷嘴入口饱和温度分别为40和50℃时,R22在喷嘴内实际膨胀过程的临界温度分别为-3.5和3.0℃,宜采用渐缩型喷嘴.

The nozzle of a liquid-liquid ejector is selected as the research object, and a non-isentropic expanding model and a homogeneous sonic model of gas-liquid two-phase fluid in the nozzle are established. Then the change trend of sonic velocities of R134a and R22 under different inlet-outlet pressure drop of nozzle are investigated. Simulation results show that, with the decrease of saturation temperature of the nozzle outlet, the local sonic velocity of nozzle outlet decreases slowly. But the actual speed of nozzle outlet increases quickly, the sonic velocity of R22 in the nozzle outlet is about 1.5 times that of R134a. While the temperature of nozzle inlet maintains 40 ℃, the critical temperature of R134a in the actual expanding process is about 14. 5 ℃, and a convergent-divergent nozzle should be adopted for the ejector. When the inlet saturated temperature of nozzle are 40 and 50 ℃, the critical temperatures of R22 in the actual expansion process are - 3.5 and 3.0 ℃, respectively, and a tapered nozzle should be used for the ejector.