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 p ressure 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). Me asurements included downstream Pitot probe traverses, upstream total pressu re, and endwall static pressures. Flow visualization techniques such as sha dowgraph 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 compa red 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 t otal pressure losses is less pronounced. Based on the shadowgraphs taken du ring the experiment, it' s believed that the large increase in losses at tr ansonic conditions is due to strong shock/boundary layer interaction that m ay lead to flow separation on the blade suction surface.