Influences of Mach number and flow incidence on aerodynamic losses of steam turbine blade

An experiment was conducted to investigate the aerodynamic losses of high pressure steam turbine nozzle (526A) subjected to a large range of incident angles (-34 degrees to 26 degrees) and exit Mach numbers (0.6 and 1.15). Measurements included downstream Pitot probe traverses, upstream total pressure, and endwall static pressures. Flow visualization techniques such as shadowgraph and color oil flow visualization were performed to complement the measured data. When The exit Mach number for nozzles increased from 0.9 to 1.1 the total pressure loss coefficient increased by a factor of 7 as compared to the total pressure losses measured at subsonic conditions (M-2 < 0.9). For the range of incidence tested, the effect of flow incidence on the total pressure losses is less pronounced. Based on the shadowgraphs taken during the experiment, it' s believed that the large increase in losses at transonic conditions is due to strong shock/boundary layer interaction that may lead to flow separation on the blade suction surface.