Study On The Flow Characteristics Of The Low Speed Axial Compressor Based On DES Numerical Simulation

The complex three-dimensional flow effects in the compressor directly affect the aerodynamic performance of the compressor.RANS or LES method is difficult to calculate the performance of the compressor if they are used separately.In this paper,a low speed large scale axial compressor is taken as the research object and the research is carried out based on DES method of mixed RANS and LES.First of all,the experimental data of NACA65 linear cascade and Stage35 are used to validate the numerical simulation method.The application of DES97 method compared to DDES and IDDES method is verified by using OpenFOAM.And the gird partition of DES97 method is verified by using Fine/Turbo.After comparing the full annulus method,the domain scale method,the phase lagged method and nonlinear harmonic method,the domain scale method is selected as the unsteady calculated method in the paper.Finally,the low speed large scale axial compressor is calculated by DES97,URANS and RANS method.Two compressors with different stage environments are studied.The aerodynamic performance and flow characteristics in design point or near stall point are compared and analyzed by three different numerical methods.Research shows that at near stall point,the difference of numerical methods are mainly concentrated in the corner where the flow separation is severe.Compared with RANS method,the flow angle calculated by DES method is smaller than 10 degrees;the efficiency is less than 10% and the total pressure loss is larger than 0.12.The streamwise length of corner separation calculated by DES method is 80% chord length,while the result calculated by RANS method is 60% chord length.The entropy loss at the blade's tip calculated by DES method is smaller and the resolution of the fluid vorticity is greater than that of RANS method.At near stall point,the corner separation and the loss of two-stage compressor calculated by DES method are more severe than that of one-stage compressor,while the efficiency in the corner is lower and total pressure loss is larger.In addition,the efficiency of R3 blade at near stall point is about 10% less that at the design point.