Research On The Effects Of Rotors With Shroud On Aerodynamic Characteristics Of Axial Flow Compressor

Compressor is the key components of the gas turbine.Rotor's tip leakage of the compressor is an important research direction in recent years.Many relevant control method is effectively applied to improve the condition of tip clearance's flow.But there are also some limitations and negative effect.In order to further improve performance of the compressor and the condition of tip clearance's flow,on the basis of compressor's experiment and CFX software,numerical simulation of a two stage compressor is carried out and analysis of the aerodynamic performance and internal flow field is compared with the experimental results.Shroud is added to the tip of rotors and numerical simulation is carried out.It is researched how the shroud of blades impact internal flow field of compressor after eliminating the original form of tip leakage.The result of modified compressor is compared with the result of the original compressor.The feasibility of the shroud of blades is explored and the reference is provided for the study of control of the compressor's tip leakage.The main research is as follows:1.Verification of numerical simulation method.A two-stage transonic compressor is regarded as the research object.The method of numerical simulation is adopted to get the characteristic curve of the compressor's performance under different rotational speed.Then the curve is compared with the result of the experimental results.It has validated the reliability of the numerical simulation's method.2.Analysis of internal flow field of compressor.With the change of the speed,the relative Mach number contours of the blade section of different height is analyzed in near peak efficiency condition and near stall condition and blocking conditions.It reveals the distribution of the unstable flow state of the compressor at near stall condition and blocking conditions.The streamlines of the blades' surface are analyzed under different conditions at the full speed,which shows the characteristics of unsteady state in whole blade channel.3.Analysis of the flow field of tip leakage.Tip leakage is another important factor to influence the compressor aerodynamic performance.Leakage fluid lead to the formation of leakage vortexes which impede the flow of the mainstream.When condition of the compressor approach to the border of stall,low-energy group area of leakage vortexes expand.Leakage vortexes' characteristics of R1 and R2 have some difference,the main leakage area is related to static pressure distribution of the suction and pressure surface of the blade.4.The influence of the shroud of blades on the compressor's performance and internal flow field.In this paper,numerical simulation of the modified compressor is carried out to study the influence of the compressor's performance and internal flow field at different speeds.Then the calculation results of the modified compressor are compared with the original compressor.The results show that the efficiency of the modified compressor can be improved only at certain speed range and the change have different influence on the different rotors.Seal technology makes the compressor has higher efficiency and pressure ratio.The stall boundary of the compressor without seal obviously moves to the right.Grate tooth seal is effective to reduce backflow phenomenon between the shroud of blades and the casing.The shroud of blades eliminates the leakage vortex loss caused by the original blade tip leakage flow in the compressor and a larger vortex is formed in the corner between the blades and the shroud The vortex causes the air flow to be largely separated.The shroud of blades makes turning angle of R2 reduce and the work of R2 decline.The efficiency of the whole modified compressor still has improved,for the flow field of the R1 have no vortex and loss of the tip leakage.Therefore,the shroud of rotors can improve the compressor performance and tip area flow of the rotors to some extent.