Detached Eddy Simulation Method For Multistage Compressor Applications

Predicting the aerodynamic performance accurately and the corresponding flow mechanism plays an important role in the design phase of a compressor with high efficiency and high surge margin.High-order turbulence model and unsteady numerical simulations for multi-stage compressors are treated as two effective methods to improve the predicting accuracy.Therefore,in this paper,Detached-eddy Simulation(DES)and unsteady numerical simulations for multi-stage compressors are presented based on an in-house RANS(Reynolds-average Naiver-stokes)code,and the corresponding validation and application are performed.In the first place,DES CFD codes with S-A and SST turbulence models were developed.Computational results with S-A and SST turbulence models had the accuracy the same as RANS near the wall and LES in the main flow region,which was achieved by adding a scale switch in the turbulence model,and the computational time consuming was considerable.Numerical simulations on a bar and the single-row compressor Rotor 67 were performed with DES and original turbulence models.Comparison between numerical results and experimental data showed that DES had the capability of capturing small-scaled flow filed with higher predicting accuracy.Furthermore,DES with SST turbulence model behaved much better.Then CFD code of unsteady simulations based on the multiple-frequency phased-lagged method for multi-stage compressors was developed.By means of Fourier decomposition and reconstruction for unsteady flows,the phased-lagged method for the single passage could be expanded to unsteady simulations for multi-stage compressors with the row number greater than three and prime number for a certain row.Combined with DES method,this CFD code was adopted to verify its ability to simulate the single passage for a 3.5-stage compressor.Results showed that the overall performance with unsteady simulations had an error within 1%,which was better than steady simulations,and the unsteady rotor-stator effects with wake-blade and blade-shock(leading edge)interactions.Finally,the developed DES method was used to analyze a highly-loaded 2.5-stage fan with steady and unsteady simulations.Numerical results showed that there existed large enwall losses in the first stator with transonic design.Meanwhile,the unsteady forward/backward motions of the first stator passage shock waves were found to induce large pressure fluctuations for this stator and the downstream rotor,providing a guidance for the design of fan in engineering.