Analysis For Performance Of Adjustable Steam Ejector

Low pressure steam can be recycled by the steam ejector, which can implement mixing the fluid, transferring the heat, increasing the pressure and so on. Because of simple structure, low manufacturing cost and many other advantages, steam ejector is widely used in industrial refrigeration, aerospace, seawater desalination, nuclear power plant safety engineering, chemical production and so on. However, the steam ejector does not have high efficiency and the traditional fixed ejector only work normally under the design conditions. Therefore, improving the efficiency of ejector and the adaptability to different working conditions have great significance in many industrial fields.In this dissertation, the wet steam model is utilized to simulate the steam flow in the fixed and adjustable steam ejectors by solving the N-S equations in conservative form. The influence of the steam non-equilibrium phase change during the transonic flow process has been analyzed. And the reliability of the results is proved by comparing with the experimental data.Under the same conditions, the spindle has great influence on the mass flow of the suction flow when the structure parameters of the fixed and adjustable steam ejector are the same. The entrainment ratio of the adjustable ejector is smaller than what of the fixed ejector. The shock happens at the same position in the two kinds of ejectors and the spindle has effect on weakening the condensation in the ejector.The intensity and position of the shock wave can be changed by moving spindle, so that the adjustable steam ejector can be adapted to different working conditions. Moving spindle towards the positive direction, dt decreases, condensation phenomenon weakens, the position of the shock wave moves towards the negative direction and the intensity of the shock wave weakens. The ejector becomes more suitable for the working conditions of low discharge pressure, high motive pressure and high suction pressure to get higher entrainment ratio. In contrast, when the spindle moves towards the negative direction, the range of working condition is enlarged and the other variations are opposite.Chocking in the ejector diffuser has significant correlation with discharge pressure, motive pressure and suction pressure. Increasing discharge pressure, decreasing motive pressure or decreasing suction pressure will cause the shocking position to move upstream and into mixing chamber. The condensation weakens and choking disappears, ejector can not work normally. Under the same conditions, the cone angle is relatively independent on the performance of ejector, while the da possesses the dominant influence on that. The result shows that the larger da, the higher entrainment ratio is.