Studies For The Influence Mechanism And Drag-reduction Method Of Surface Micro-topography On The Performace Of Linear Cascade

With the development of aviation industry, high requirements of aero-engine have been proposed by the modern aircraft. As an important part of aero-engine, the performance of blade will directly affect the efficiency of aero-engine. The current main task is to study the influence mechanism of surface micro-topography on blade efficiency, and to investigate how to reduce the flow loss, and improve the aerodynamic performance of linear cascade.Firstly, a new dimpled structure is designed and numerically studied the drag reduction characteristics and mechanism in the turbulent flow of it. Meanwhile, taking influence factors of dimpled surface drag reduction into account, such as dimple shape, diameter, depth, space, and configuration, we choose the combination with the best drag reduction effect. The wall shear stress, static pressure, flow field characteristics near-wall region and flow parameters along height direction are analyzed to explain the flow characteristics and drag reduction mechanism of dimpled surface.Secondly, dimples with optimal drag reduction are applied on 30%-60%and 75%-95% axial chord of blade suction side respectively. Then we study the influence of dimples on the performance of linear cascade under different incidence angles and the comparison of drag reduction characteristic about the two dimpled blade models. The pressure coefficient, viscous force, wake loss, and total pressure loss of blade with dimples are analyzed in detail. The simulation results indicate that dimples reduce the flow loss significantly. Finally, setting up subsonic-speed linear cascade wind tunnel verifies the feasibility of applying dimples on the blade surface to reduce the flow loss.Lastly, in view of the blade machining precision, adopting realizable k-s turbulent model and scalable wall function method, the effect of magnitudes and locations of surface roughness on linear cascade under different incidence angles are researched. Seven equivalent sand grain roughness magnitudes 4.96,9.92,19.84,39.06,77.5,155,200?m, and three partial locations 0-1/3,1/3-2/3,2/3-1 chord lengths of suction surface are studied. The viscous force of suction surface, wake loss, total pressure loss, and load force of blade surface with dimples are analyzed. The results indicate that the magnitude of roughness below threshold value has a very slight effect on total pressure loss. As it exceeds threshold value, the total pressure loss dramatically declines. Meanwhile, the overall roughness effect is much larger than partial roughness effect. And in all incidence angles, the roughness applied on 0-2/3 of suction surface has the largest influence on the total pressure flow loss; but arranging roughness after 2/3 of suction surface is the least sensitive to flow loss. The results acquired in experiments agree very well with determined by the numerical simulations.