Numerical Analysis And Optimization Of Tip Clearance Flow Characteristics In Centrifugal Compressor

Due to the advantages of high efficiency,high pressure ratio and wide working range,the semi open centrifugal compressor has been widely used in the fields of automobile,ship,weapon equipment,petroleum chemical industry.Impeller is the important parts of centrifugal compressor,and the impeller tip gap size is one of the important parameters,it on the turbocharger operating range,efficiency,maximum pressure ratio,energy transfer and loss,secondary flow and noise have important influence.Due to the processing technology and the structural strength of the impeller and the actual needs of the project,too small gap size is more difficult to achieve.Therefore,it is necessary achieve a balance,that between the overall performance and actual situation of the project,find a suitable impeller gap size,with both high pressure ratio,high efficiency,big stable operation range,small stall flow and other factors.In order to study the relationship between the blade tip clearance and the aerodynamic performance of the impeller.In this paper,the centrifugal compressor part of an internal combustion engine is selected as the original model.Firstly,the three-dimensional modeling software UG of centrifugal compressor impeller and volute of geometric modeling,then the CFD(Computational Fluid Dynamics)technique for the four different leaf top gap dimensions of the compressor in the gas dynamic performance,leaf tip load,the flow field inside the impeller and other aspects are studied in detail.At the same time,the simulation data of CFD are compared with the test data to ensure the accuracy of the simulation.Finally,according to the structural parameters of the impeller,the automatic optimization of multi working conditions is carried out,and the aerodynamic performance of the compressor is greatly increased.According to the four different leaf top clearance of centrifugal compressor numerical calculation shows,compressor pressure ratio and efficiency decreased with the increase of the gap and when the gap exceeds a certain degree,was reduced to accelerate,between them is nonlinear relationship;at the same time,the appropriate tip clearance can effectively increase the operating range of compressor,stall flow point has moved forward.In addition,the aerodynamic load and the static pressure distribution of the tip of the blade with a small three mass flow operating point can be seen that it has a similar rule with the clearance leakage.Centrifugal compressor under the three conditions,the blade tip position appeared different degree of velocity gradient,cause in the tip clearance leakage flow;in the compressor off design conditions and the blade suction side and pressure side pressure difference,resulting in mixing flow is very intense,obvious "jet wake" phenomenon,produced a larger export flow loss.At the same time to improve after the blade tip gap size modification of compressor,using the software NUMECA of the model impeller working free optimization,selection of small,medium and large mass flow point,through the use of the whole compressor pressure ratio and efficiency to set the objective function to achieve the purpose of optimization of compressor aerodynamic performance.