The Analysis And Optimization Of Air Ejection Transportation Ejector Based On CFD Simulation

Cutter suction dredger is a very important engineering ship in dredging operation. Cutter suction dredger dredges up sullage into transportation pipeline which transport sullage to designated area. The difficulty of pipeline transportation of sullage is that how to extend the discharge distance of pipeline transportation, in order to extend the displacement air ejection transportation technique is applied in pipeline. Compares with the traditional relay pump technique air ejection transportation technique performs well, it has simple structure, can be easily installed and work without additional relay pump ship and corresponding crew. As a key equipment of air ejection transportation the capability of air ejection transportation ejector has important effect to extend the discharge distance of the pipeline transportation of sullage.The core content of this article is discussing that how do different methods of the driving fluid entering the ejector effect the working performance of the ejector, and how does the structure of the air ejection transportation ejector influence the efficiency of the air ejection transportation ejector. The core content of this article is divided into the follow parts:(1)Illuminate the computational fluid dynamics theories relating to the air ejection transportation ejector; determine parameters such as the two-phase model, turbulent model, the kinds of the boundary conditions and so on.(2)Discuss the manners of the fluid phase entering the ejector such as the fluid axial flow and the fluid helical flow. Simulate the fluid axial flow and the fluid helical flow by FLUENT. Analyze the temperature field, velocity field, pressure field and the air volume fraction in the diffuser chamber of the two different fluid flow manners. By comparing with the two manners find out that the velocity field of the diffuser chamber and temperature field of the diffuser chamber are well mixed to the fluid helical flow, its jet coefficient is at a higher level, and the distribution of the air volume fraction is propitious to promote the efficiency of the pipeline transportation, as a result the fluid helical flow is a fine project.(3)Set the length of the constant area segment of the diffuser chamber of the air ejection transportation ejector and the distance between the nozzle and the entrance of the diffuser chamber as variable quantities. Divide the length of the constant area segment of the diffuser chamber into 7 levels such as 40mm,50mm,60mm,70mm,80mm,90mm,100mm and divide the distance between the nozzle and the entrance of the diffuser chamber into 9 levels such as Omm,5mm,10mm,15mm,20mm,25mm,30mm,35mm,40mm, then simulate all the levels by FLUENT. Compare the velocity magnitude and jet coefficient of the working fluid with the velocity magnitude and jet coefficient of the driving fluid at the entrance of the constant area of diffuser chamber. By analyzing the result find out the optimum values of the constant area segment of the diffuser chamber and the distance between the nozzle and the entrance of the diffuser chamber are 70mm and 15mm.