Research On Influence Of The Impeller-Diffuser Gap Vortex On The Aerodynamic Characteristics Of Centrifugal Compressor

Impeller-diffuser interaction not only affect the characteristics of the impeller and diffuser,but also the characteristic of the stage,its important function approach is the flow characteristics inside the impeller-diffuser gap including the impeller-diffuser gap vortex.In order to clearly understand the influence,this paper analyzed the formation mechanism of the impeller-diffuser gap vortex,and the influence rule to the characteristics of centrifugal compressor.The main research work of this paper includes:1?The analysis of the formation mechanism of the impeller-diffuser gap vortex,and the parameters of the diffuser affected the impeller-diffuser gap vortex.The formation mechanism of impeller-diffuser gap vortex was analyzed based on the dynamics mechanism,and summarized the way to suppress the impeller-diffuser gap vortex when keeping the diffuser inlet radius and air density alike,including: minimized circumferential speed of airflow of the impeller downstream,minimized the inverse pressure gradient in the direction of meridional streamline,reduced the friction.Contrasted the impeller-diffuser gap vortex when matching some vaned and vaneless diffusers,it can be concluded that the area of expansion downstream of the impeller,diffuser import installation angle,the distribution of the diffuser blade installation angle,and channel area distribution of diffuser will produce very big effect on the impeller-diffuser gap vortex formation.2?The analysis of the affect of impeller-diffuser gap vortex on the impeller characteristic.This paper analyzed the relationship between the impeller-diffuser gap vortex and the characteristics of the impeller by the way of changing impeller-diffuser gap vortex through designed different diffuser.The decrease of the impeller-diffuser gap vortex area and the increase of the average absolute value of vorticity will benefit increasing efficiency of the impeller.There is a optimum position of the impeller-diffuser gap vortex that makes the highest efficiency of the impeller.the integral of absolute value of vorticity and the characteristics of the impeller had no obvious relationship.3?The analysis of the affect of impeller-diffuser gap vortex on the diffuser characteristic.This paper analyzed the affect of size of the impeller-diffuser gap vortex,the intensity,and the axial and radial position of the impeller-diffuser gap vortex on the diffuser characteristic through the numerical simulation analysis of the flow inside the diffuser.There is a optimum vortex area of the impeller-diffuser gap vortex that makes the highest efficiency of the diffuser,and there is a optimum average of absolute value of vorticity of the impeller-diffuser gap vortex that makes the highest efficiency of the diffuser,too.The efficiency of the diffuser increase with the increase of the axial coordinates of vortex center point.There is a radial coordinates of vortex center point that make the efficiency of the diffuser worst.The integral of absolute value of vorticity and the characteristics of the diffuser had no obvious relationship.4?The analysis of the affect of impeller-diffuser gap vortex on the stage characteristic.Through contrasted the characteristics of the compressor stage at different impeller-diffuser gap vortex,it can be concluded that the impeller-diffuser gap vortex size,the intensity,and axial coordinates and the radial coordinates of vortex center point can affect the characteristics of the compressor stage,while the integral of absolute value of vorticity and the characteristics of the compressor stage had no obvious relationship.There is a optimum vortex area of the impeller-diffuser gap vortex that makes the highest efficiency of the stage.The decrease of the average absolute value of vorticity will benefit increasing efficiency of the stage.The increasing of the the axial coordinates and radial coordinates can increase the efficiency of the stage.