EFFECTS OF LEANING AND CURVING OF BLADES WITH HIGH TURNING ANGLES ON THE AERODYNAMIC CHARACTERISTICS OF TURBINE RECTANGULAR CASCADES

To understand the effects of the origination and development of centra lized vortices on the aerodynamic characteristics of turbine rectangul ar cascades with high turning angles, experiments with five-hole micro spherical probes, accompanied by color helium bubble flow displays, we re carried out. The measurement planes are arranged as three before, s ix in, and one after the cascade. The experiments reveal that the orig ination and development of horseshoe vortices and passage vortices as well as the interaction of the latters almost dominate the whole flow field of traditional linear cascades. Lean linear cascades favor the h orseshoe vortices and passage vortices in the acute angle zone, and im pede those in the obtuse angle zone. So it is a logical result to adop t the negatively curved blades, whose pressure surfaces and both endwa lls compose both obtuse angles, respectively, to improve the cascade a erodynamic characteristics.