Parameter Analysis Of Upstream Pumping Grooves For Leakage Reduction In Rotary Energy Recovery Devices

In seawater desalination system,rotary energy recovery devices(RERD)are limited to improve the key performance indicator of energy recovery efficiency due to the internal leakage problem between the conjugate clearances of the,rotor,end covers and other units.The most promising to control the leakage as upstream pumping technology are considered,its application research on RERD is even inefficient for the stage of exhaustive experience accumulation.Therefore the highly efficient pumping-technology application theory needs urgent improvement.Concerning the structure of typical RERD rotor,here was obtained the flowing forms of leakage flow under CFD simulation.According to the forms,main routes of RERD leakage were defined as following: a.the radial leakage on the end face,b.the circumferential leakage on the end face,c.the annular leakage between the annular gaps.An analytical RERD leakage model was constructed by expressing above three routes with mathematical formulae.Comparing the predictions under identical working conditions either from the formulae or from CFD,the proximity about total leakage flow rate were up to 99.23%,indicating the model proposed in this paper able to illustrate RERD leakage.In addition,it's found from the model's expressions that under identical conjugate clearances,the radial route was proved as dominate route for covering 61.44% of total RERD internal leakage.Therefore,a route should be solved first in order to reduce the total leakage in RERD.Upstream pumping grooves(UPG)were introduced to the region of a.route for leakage control.And the analytical model were advanced to illustrate the radially leaking process with UPG under hydrodynamic principles.Regarding the grooved radial leaking process,the model still had the ability of accurate description for over 91.20% proximity of leakage rate to those by CFD under identical working conditions.Besides,on the basis of the model,the designing orientations of UPG parameter for leakage reduction were obtained by factor analysis.Grooves with farther radial location and bigger spiral angle differences could prevent the RERD from more radial leakage.The prevention would be maximized where it's balanced as minimum in total between the pumping flow and corresponding pressure backflow.On the basis,the designing processes of UPG on RERD has been simplified to a large extent.