Characteristics Research About Internal Flow Field Of The Gas Phase Ejector

Steam ejector is a kind of fluid conveying machinery without transmission device.It can recycle and utilize of low grade energy.Based on this principle,steam ejector is widely used in chemical,petroleum,paper making aerospace and other fields.The ejector's structure is simple,but the mixing layer effect,shock wave phenomena and near wall boundary layer phenomena make the flow fluid unclear.A lot of experience and semi-empirical formula was used in the design of ejector because of it.But this formula's adaptability is poor,and which restricts the optimization and development of the ejector.Based on these issues,in this paper,the characteristics of internal flow field has been analyzed and researched by the way of numerical simulation.The main conclusions are as follows:(1)Known the related data of engineering examples and requirements,using classical thermodynamics analysis method,we calculate the ejector's key structure size,as the original data of the ejector structure model in this paper.(2)In order to obtain the detail information of the internal flow field in gas ejector,establishing gas ejector computational fluid dynamic and then doing grid independence test and turbulent model verification.Finally,we choose k-? Realizable model as turbulence model used in this paper.(3)In the article,the characteristics of ejector's internal flow field have been analyzed.The conclusion is as follows:The study found that the diamond shock phenomenon has direct relationship with the ejector's performance.The ejector coefficient had an optimal value when diamond shock wave extended near by the outlet of mixing section.The diamond shock end early or late will be bad for ejector's performance.For a certain ejector,there is the best primary fluid inlet pressure to make the highest entrainment ratio of ejector.The entrainment ratio has positive correlation with the secondary fluid.For a certain ejector,there is the largest export pressure under the best working state of ejector.When the mixing fluid outlet pressure is larger than it,the entrainment ratio fell sharply.Under a certain operating environment,the nozzle outlet diameter has influence on entrainment ratio by changing the pressure environment(suction vacuum)of nozzle exit.The mixing chamber length and ejector's throat diameter have the effect on the diamond shock wave length so as to influence ejector's entrainment ratio.For a certain ejector,there is the best mixing chamber length and best throat diameter corresponding to the best performance of ejector.The structure of throat length and the angle of diffuser have little influence on entrainment ratio,but they have important effect on ejector's operating flexibility.But there is a certain range of angle to keep the ejector high operating flexibility.For a certain operating condition,there is best throat length for maximum compression ratio.The diffuser's angle should be designed under a certain range.When it is out of this range,the operating flexibility will decrease to some extent.