EFFECT OF CURVING OF HEAVY DUTY BLADES ON WALL FLOW

Static pressures on endwalls and blade surfaces and growth of the losses along flow direction were measured,and the flow visualizations of the endwall and blade suction surface with ink traces were also made.The experimental results show that the positive curving of the blade increases the streamwise adverse pressure gradient in the cascade inlet and makcs isobars on the front part of the blade suction surface into opposed C shape,thereby the saddle point separation near the blade leading edges and convergence of separation lines on the suction surface to the cascade middle are intensified.The negative curving of the blade reduces the adverse pressure gradient in the cascade inlet and makes isobars perpendicular to the endwall on the front part of the blade suction sarface.As a result not only the separation flow near saddle point weakens,but also the separation flow on the suction surface turns into free vortex laminal separation so as to aviod interception of the upper and lower separation lines.In consequence,the secondary vortex losses are decreased greatly.