多喷嘴汽-液两相喷射器的工作特性研究

Working Character of Multi Nozzle Steam-liquid Two-phase Ejectors

对以湿蒸汽为工作流体的多喷嘴汽–液喷射器机制进行研究,利用质量、能量及动量守恒方程建立了喷射器工作特性一维理论模型。模型求解过程中,采用两相临界流均相平衡模型计算单喷射蒸汽喷嘴的临界流速,并利用多喷射速度系数对其修正,得到多喷射蒸汽喷嘴的出口速度;综合考虑Cattadori的壁面力和Howard的喉部压损理论对流动的影响来确定混合室阻力。为验证模型的正确性,设计以湿蒸汽为工作蒸汽的实验台,并采用多喷嘴喷射器作为实验元件。研究结果表明:容积喷射系数随压力比的增大而减小,且增大喷射器的截面比可使容积喷射系数增加,但缩小了喷射器的工作范围;容积喷射系数随蒸汽干度的增大和过冷水温度的升高而减小。理论计算结果与实验值基本相符。

A one-dimensional theoretical model was built to calculate the performance data of multi-nozzle steam-water two-phase ejector by the equations of mass,energy and momentum conservation for calculation of mechanism of multi nozzle steam-liquid two-phase ejector with wet saturated steam as the working fluid.The critical velocity of the single steam nozzle was computed by homogeneous equilibrium model of two-phase critical flow and amended by the multi-steam nozzle speed coefficient,and then the exit velocity of the multi-steam nozzle was obtained,and the resistance of the mixing section was determined by integrating Cattadori＇s wall forces model and Howard＇s ＂throat＂ pressure loss theory.In order to verify the proposed model,a set of experimental facility was designed with wet saturated steam as the working fluid and a type of multi-nozzle ejector as the experimental unit.The results show that volume entrainment ratio decreases with the increasing of pressure ratio,that the increasing of cross section of the ejector can increase volume entrainment ratio but cut down the working range of the ejector,and that the volume entrainment ratio decreases with the increasing of the steam dryness and sub-cooled water temperature.The computational results of volume entrainment ratio agree well with the experimental data.