Numerical Investigation On The Aerodynamic Performance Of Ram-rotor By Circumferential Groove Casing Treatment

Gas turbines are the highest-end products in the field of energy power equipment.The development of high-performance compressors is of great significance for improving the overall performance of gas turbines.The airflow can be compressed sharply and efficiently through shock systems in the ram-rotor which has the advantages of high pressure ratio,compact structure and light weight.However,interaction between shocks and interaction between shock and boundary layer in ram-rotors which generates complex flow phenomena make the rotor characteristic curve steep and the peak efficiency condition close to the stall condition.Therefore,it is an urgent problem to be solved that how to effectively expand the stability margin of the ram-rotor.Taking the ram-rotor as the research object,this thesis firstly analyze the influence of single circumferential groove position parameters on the aerodynamic performance of the ram-rotor by numerical simulation method.It is found that the single circumferential grooves of each axial position reduce the total pressure ratio and peak adiabatic efficiency to different extents.The axial position influences the expansion capability of single circumferential groove,and the best stability margin increase is achieved when placed at 75%axial chord length,which is 4.71%higher than the prototype.The single circumferential groove introduces the high-energy fluid of the right flow channel into the left flow channel,increasing the flow velocity before the terminal shock.Thereby,it enhances the flow energy and the through-flow capacity at the upper end wall and delays the occurrence of the rotating stall.Subsequently,the single circumferential groove is set at the axial position with the best modification effect.Based on this,the groove depth and groove width are changed respectively and the influence of the single circumferential groove structure parameters on the aerodynamic performance of the ram-rotor is studied.The results show that the near-stall flow rate of the ram-rotor decreases with the increase of the groove depth,while the stability margin increases.and the best stability margin increase is obtained at 12mm groove depth,which is 14.99%higher than the prototype.However,the change of single circumferential groove depth also causes the range of the low-speed zone and the position and structure of the shock wave to change.When the single circumferential groove width is increased,the total pressure ratio and peak adiabatic efficiency of the ram-rotor decrease and the stability margin increases first and then decreases.Similarly,the low-speed zone in the flow path and the position and structure of the shock wave change.Finally,based on the above research conclusions,the double circumferential groove is set to study the influence of variable spacing on the aerodynamic performance of the ram-rotor.The results show that the double circumferential groove will cause the main performance parameters of the ram-rotor to decrease significantly and the influence amplitude has nothing to do with the spacing;the circumferential double groove has more influence on the mainstream of the ram-rotor than the single groove,and its shock position and structural change more obviously.