Effects Of Microsurface Riblets On Aerodynamic Performance Of Compressor Cascade

Bionics research found that the surface micro structure can change the boundary layer structure,suppress the turbulence burst frequency and intensity,and reduce the surface friction,which provides a new idea for the aerodynamic performance optimization of moving objects.The microsurface riblets drag reduction technology has become a hot research topic because it does not need to consume other energy and has good drag reduction effect.In this paper,the NACA65-010 airfoil is taken as the research object.For the streamwise symmetrical V type riblet and trapezoid type riblet applied on the compressor cascade blade,the influence of microsurface riblets on the aerodynamic performance of compressor cascade and the analysis of loss reduction flow mechanism are studied by numerical simulation and experimental method under the compressible and incompressible flow conditions respectively.The main research contents and conclusions are as follows:(1)Under the condition of compressible flow,the numerical method is adopted to study the effects of V-type riblets spacing,riblets tip angle,riblets position,riblets size,and riblets shape on the aerodynamic performance of compressor blade profile.The effects of inlet turbulent intensity and Mach number on the aerodynamic performance of compressor cascade with V-type riblets are analyzed.The drag reduction mechanism of V-type riblets is analyzed.The results show that the total pressure loss reduction is mainly caused by the riblets on blade suction surface.By properly matching the riblets geometry parameters,riblets coverage position and inlet flow parameters,the optimum total pressure loss reduction can be obtained.For the optimized riblets on blade suction surface within partial blade chord range,the loss reduction of riblets without spacing is better than that of riblets with spacing at the same incidence angle.For the riblets without spacing,when the tip angle is 60 degree the loss reduction is the best.For the same riblets structures,the loss reduction is related with the incidence angle.The total pressure loss coefficient of smooth blade and blade with riblets increases with the increase of inlet turbulent intensity at the same incidence angle.The loss reduction effect of the same riblets structures at the same incidence angle and the incidence angle corresponding to the optimal loss reduction effect are affected by inlet turbulent intensity.When the incidence angle is constant,the loss reduction effect of the same riblets structures decreases with the increase of inlet Mach number.The dimensionless width of riblets corresponding to the optimum loss reduction and the range of riblets dimensionless width with loss reduction are different.When the dimensionless width and other parameters of riblets are fixed,the optimum loss reduction and its corresponding incidence angle at different inlet Mach numbers are different.The optimum loss reduction at lower Mach number is more obvious.When the V type riblets without spacing is covered on 15%-50%blade chord of suction surface and the riblets tip angle is 60 degrees,and inlet turbulent intensity is 5%,the maximum loss reduction is 3.3%at incidence angle of 0 degree at 0.4 Mach number,and the dimensionless width of riblets is 12.3.The maximum loss reduction is 3.23%at incidence angle of 8 degree at 0.3 Mach number,and the dimensionless width of riblets is 15.At the same time,the microsurface riblets has little effect on the flow turning angle.The microsurface riblets can reduce the near wall average shear stress and turbulent kinetic energy,and alleviate the turbulent boundary loss.The boundary flow separation can also be delayed,and the blade profile loss is reduced.The comparative analysis of V type riblet and trapezoid type riblet shows that both two riblets shapes can reduce the profile loss within a certain range of incidence angle,and the optimal reduction effect and the corresponding incidence angle are different.The optimal reduction effect of V type riblet is better than that of trapezoid type riblet.The trapezoid type riblet has no obvious effect on the turning angle.(2)Under the condition of incompressible flow,the numerical method is adopted to study the effects of V-type riblets position,riblets size and inlet turbulent intensity on the aerodynamic performance of the compressor blade profile;Based on the optimization scheme of V type riblet,the difference of loss reduction effect between V type riblet and trapezoid type riblet is analyzed;At the typical incidence angle,the comprehensive influence of the above various factors is analyzed.The drag reduction mechanism of V-groove and trapezoidal groove is analyzed.The results show that the effect of loss reduction is better for the blade with local riblets on the suction surface when the riblet is arranged before the separation zone under the condition of low turbulent intensity.When the riblet is arranged in the separation zone,the effect of loss reduction is not obvious,even the loss is increased.The optimal loss reduction effect and the corresponding incidence angle are different for different groove positions.For the optimal riblets position,the optimal loss reduction effect is different for different riblets sizes at the same incidence angle.At the same incidence angle,the total pressure loss of the blade with local riblets on the suction surface decreases and the flow turning angle increases with the increase of inlet turbulent intensity.At the same incidence angle,the blade with local grooves on the suction surface has different loss reduction effects under different inlet turbulent intensity.The loss reduction effect of the riblets decreases with the increase of inlet turbulent intensity.At the incidence angle of 0 degree,the maximum loss reduction of V-type riblets is 5.78%when the turbulent intensity is 1%;and the maximum loss reduction is 1.1%when the turbulent intensity is 5%.The microsurface V-type riblets has little effect on the flow turning angle.The comparative analysis of V type riblet and trapezoid type riblet shows that both two riblets shapes can reduce the profile loss within a certain range of incidence angle,and the optimal reduction effect and the corresponding incidence angle are different.The optimal reduction effect of V type riblet is better than that of trapezoid type riblet.The trapezoid type riblet has no obvious effect on the turning angle.Compared with the smooth blade,the average shear stress of the blade with microsurface riblets is less than that of the smooth blade.The microsurface riblets can change the near wall velocity and boundary layer distribution.The energy exchange of the fluid in the normal direction of the separation zone is suppressed.The turbulent kinetic energy is reduced and the blade profile loss is reduced.(3)The ultra precision machining method is used to process the trapezoidal riblets without spacing on 20%-50%blade chord of suction surface,the riblets tip angle is 30 degree,height to width ratio is 0.5 and the riblets width is 0.185 mm.When the inlet velocity is 25m/s and the turbulenct intensity is 1%,the dimensionless width of riblets is 17.The experimental results show that the microsurface riblets can reduce the loss coefficient by 26.2%at incidence angle of 0 degree.