Study On Inverse Design Of Mixed-flow Pump Impeller

Due to the three-dimensional effect of mixed flow pump impeller,the internal flow is very complex.The forward design of impeller relies heavily on the experience of the designer and consumes computational resources.In view of the low efficiency of impeller forward design,this paper uses MATLAB programming language to write the rapid inverse design program of mixed flow pump impeller,in order to reduce the designer’s dependence on experience when designing impeller,and save computing resources,so as to improve the design efficiency.This paper first introduces the theory and the equations used in the process of inverse design,and then deduces the form of these equations in the orthogonal coordinate system.Then,the meridian plane meshing program is written,the program can adjust the number of meshes in the meshing program through two control parameters.Then,the finite difference scheme of the inverse design equation in the orthogonal coordinate system is derived and its solution program is written.The mean flow equation and the periodic flow equation are solved by the whole field method.The incomplete LU decomposition and the biconjugate gradient stability method of MATLAB software are used in the solution process.Finally,the generating equation of the middle arc surface is solved by the advancing method.In view of the load and blade thickness conditions required by the inverse design,this paper uses a non-uniform rational B-spline curve to give its values on the hub side and the shroud side,and the values of the remaining points on the blade are interpolated along the blade span.For a given load and thickness distribution condition,the program can achieve fast convergence in 3 minutes,which proves the feasibility of fast inverse design.The program can realize the visualization of 3D blade and output the data,as well as the information of flow field and pressure field under corresponding conditions.In order to verify the accuracy of flow field calculation,NUMECA software is used to calculate the flow field in the impeller obtained by inverse design under given load,and the turbulence model is S-A model.Comparing the flow field calculated by the program with that calculated by CFD,the results show that the inverse design program is accurate and meets the requirements of calculation accuracy.By using the inverse design program to calculate the same example,the suppression effect of two parameters in inverse design(load distribution and stacking conditions)on the low pressure area at the blade inlet is discussed as follows: for the same stacking condition and different loading conditions,the pressure distribution diagram shows that the low pressure area of the rear-loaded impeller is the smallest;For the post-loading mode and different stacking conditions,the impeller is obtained by inverse design calculation of four kinds of trailing edge middle camber surface wrap angle.Through three-dimensional CFD calculation of the obtained impeller,the results show that the suppression of the low pressure area is the most obvious when the camber surface wrap angle of the trailing edge is 30°.