Investigation Of The Changing Of Blade Aerodynamic Characteristics And Stage Performace Effected By Blade Leaning

Based on the discussion of the phenomena and the causes of secondary flow in turbine cascades and general methods which can reduce the secondary losses , this paper studys on a effective method --- leaned or compound leaned blades in detail . the paper mainly consists of four parts :In the first, the paper summarizes the reasons of leading secondary flow and some methods which can reduce the secondary losses effectively , especially blade leaning or compound leaning method .Secondly , the author analyses the changing of flow induced by the forces that blades exert on the flow within the flow passage between blades in different leaned condition by using a commercial three-dimensional aerodynamic computing program . The result of calculation shows that the changing of the flow leaded by blade leaning mainly occurs at the blades tip and root, and the changing in suction surface is much larger than the pressure surface . it also shows that the flow losses at the root of the positively leaned blade have remarkably been decreased , not only in intensity but also in its range of extention , and at the tip , the flow losses have been increased somewhat. The influence of negatively blade leaning is on the contrary . So , in order to reduce the flow losses at both ends of blades , compound leaning is the most effective method.Thirdly , through the annular cascade tests in different leaning , the author founds that the calculation results correspond with the test results qualitatively, and the test data obtained represents flow losses distribution along blade height in different leaning condition precisely . According to the results , we can deduce that the flow losses can be reduced 2 to 3 percent if proper leaning be used .Finally , by using the results that obtained above , the author calculated the aerodynamic characteristics of a typical turbine stage , such as reaction,rotating blade losses,flow capacity etc , in four different conditions . The result shows that the stationary blade leaning not only leads the flow of the blade itself changing , but also leads the stage characters changing . Therefore , the blade leaning or compound leaning must be used properly .