Numerical Study On The Effect Of Surface Roughness On Cascade Loss And Boundary Layer Flow Characteristics

Impeller machinery is widely used in various industrial fields and plays an important role in social and economic development.Maintaining high-efficiency operation of impeller machinery can reduce losses in the process of energy conversion and utilization.During the actual use of the impeller machinery,the blade roughness changes due to corrosion and wear,which makes the aerodynamic performance of the impeller machinery deteriorate and its internal flow state changes.Roughness can also be used as a passive control method.Arranging roughness on the blade surface can eliminate the adverse effect of flow separation on the performance of the cascade,and the roughness can reduce the loss of the cascade to a certain extent.In order to analyze the mechanism of roughness inhibiting separation more deeply and find out the influence of roughness on the flow state,this paper analyzes the characteristics of the flow in the boundary layer under the influence of roughness.The main contents of this paper are as follows:1.In this paper,NACA65-410 blade profile is used as the research object.The wind tunnel experiment of roughness cascade is carried out by spraying rough particles on the surface of the cascade.The SST k-ω turbulence model coupled with the - transition model is adopted.Numerical calculations are carried out on the cascade with roughness,and the numerical simulation results are compared with wind tunnel tests.The results show that the choice of the numerical model and the number of grids is reasonable.2.The law of the influence of surface roughness on the loss of the cascade was explored,and the numerical simulation analysis of the cascade under different attack angles and variable incoming Reynolds numbers was carried out.Judge the overall trend and sensitive area of roughness influence by the total pressure loss,wake loss and outlet airflow angle.It is found that the influence of roughness on the cascade loss is closely related to the angle of attack.At the same angle of attack,the degree of influence is different from Renault.There are also certain differences between the numbers.At the same time,combined with the dissipation function to explain the mechanism of roughness reducing cascade loss.3.The influence of surface roughness on the flow development and flow separation inhibition of the boundary layer of the suction surface of the cascade is studied.The transition process of the boundary layer of the suction surface with different roughness under variable angle of attack conditions is analyzed by using parameters such as wall friction resistance and turbulence.Quantitative analysis of the boundary layer displacement thickness and other parameters obtains the flow development state of the boundary layer as the roughness increases.It is found that the roughness will change the separation form of the suction surface and the limit streamline topology.4.The influence of roughness distribution position on cascade loss and its mechanism are studied.Combined with the flow development state in the boundary layer,the influence of different roughness positions on the cascade loss is analyzed,and the best position for controlling the boundary layer flow and the performance of the cascade at the best rough position under different working conditions are obtained.The paper contains 48 figures,5 tables,and 84 references.