Experimental Study On The Aerodynamic Characteristics Of The Middle Pressure Blade And Cascade Of A Steam Turbine

The development of high-power steam turbine is the inevitable trend of energy saving.In order to reduce the number of stages of flow passage and improve the relative internal efficiency,the steam turbine blades are often used with large sloping inclined blades.The engineering and technical personnel of Harbin Automobile Co.,Ltd.have designed the high enthalpy drop positive inclined blade of new type high power steam turbine unit.In order to verify its aerodynamic performance index,wind tunnel tests were carried out on stator profile and cascade of medium pressure stage of new high-power steam turbine.The medium-pressure 7-stage vane has a diameter-to-height ratio of 12.2according to the leading edge and the trailing edge.The blade is a short blade and is covered by a trailing edge.The stacking line is a circumferential negative oblique straight line which only changes with the y coordinate,and the maximum tip forward of the tip is 12% axial chord length;the inner and outer meridional flow paths are respectively a conical surface with an expansion angle of 10 degrees and 11 degrees.For the three-span blade cross-section of the stationary blade cascade,the cross-section in-line cascade is used to test the variation angle characteristics,variable installation angle characteristics,variable pitch characteristics of the three types of blade types.Change the Mach number property.At the same time,the fan-shaped cascade is used as the experimental model of the 7-stage static cascade.The distribution of aerodynamic parameters along the leaf height and pitch is measured,and whether the performance index meets the design requirements is evaluated.The test results show that the medium-pressure 7-stage cascade adopts the advanced rear loading blade type,which has a streamlined "fish head" leading edge,a high-strength blade body and a thin outlet edge,which is more remarkable.The sensitivity to the inlet angle of attack is significantly reduced.The design values of the blade mounting angle and the relative pitch(referred to as the pitch)are very close to the optimal value,and the curvature loss of the blade shape with the installation angle and the relative pitch is small,and the loss of the blade type is accompanied by the increase of the Mach number decline.The geometrical shape of the stationary blade cascade improves the three-dimensional structure of the flow-through working medium,and the aerodynamic parameter distribution along the blade height is relatively uniform,especially the main flow loss source in the short-blade large-turn corner blade cascade,that is,the secondary wall secondary flow The loss is effectively controlled,and the average pressure loss coefficient curve along the leaf height is substantially in line with two nearly equal small protrusions.This test proves that the aerodynamic performance of the 7-stage stationary vane exceeds the expected design specifications.