Multiphase Flow Experimental Study And Numerical Simulation Of Multi-functional Ejector

Ejector was a very important part in the new-style solar desalination system. At present, the studies on ejector were mostly focused on single-phase and rarely focused on two-phase. In this thesis, a liquid-liquid & gas ejector was mainly studied. For this ejector, liquid working flow was used, and both gas and liquid were pumped synchronously to transfer heat and energy. This ejector was mainly used in solar desalination system to pump the non-condensing gas and keep an appropriate vacuum. At the same time, it could also be used to pump and drain the brine water to avoid briny crystallization. For the reasons that it transferred heat and mass for both gas and liquid and it had multi functions, it was also called multi-phase multi-function ejector.Firstly, the basic fundamental of ejector was introduced and its structure was designed and computed. The theory of turbulence flow was expatiated on, the structure and theory of ejector were presented, and the change law of pressure and velocity when liquid flowed in ejector was analyzed. Then, some performance parameters and some characteristic equations had been given. Based on the existing production, full dimensions of the ejector were designed, and the dimension of each part was given in detail.Secondly, some experimental researches were done. An experimental platform of the liquid-liquid & gas ejector was built and some detailed experiments with pumping both gas and liquid synchronously were made. The influences of structural parameters such as size of nozzle and length of mixing chamber and operational parameters such as pressure of both working flow and ejector flow on the ejecting factor were analyzed.At last, numerical simulation of this ejector was performed. Both the grid generation based on finite volume method and common-used discretization were introduced. The boundary conditions in numeric simulation were listed. Control equations about the ejector interior fluid based on two-fluid model and k-ε turbulence model had been set. On the condition of pumping both gas and liquid, numerical simulations for the influence of structural parameters and operational parameters on ejector performance were performed, and then the simulation result was compared with experiment result.Through the compare and analysis between experiment result and simulation result, it was apparent that the two results were tallied with each other well. And, from these results: the optimum size for nozzle and the optimum length for mixing chamber were educed; both the law that the ejecting factor changed according to pressure of working flow and ejecting flow and the law of velocity and pressure intensity changed in the interior fluid field were concluded. At the same time, from the simulation result, it could be seen that there was a reversed flow zone in mixing chamber, and in this thesis, both the impact of different backpressure on reversed flow in mixing chamber and the impact of reversed flow on ejector performance were analyzed. Then, the optimum range for backpressure was given.