Investigation on optimal allocation of mass flow and direction for binary cooling turbine test blades

The three-dimensional viscous steady Reynolds-averaged Navier-Stokes equations and energy equation were adopted to solve coupled velocity and temperature fields for investigating the effects of the mass flow rate and the flow direction of cooling-steam and cooling-air on the blade surface temperature distribution and cooling efficiency on the basis of the SST transition turbulence model. The numerical results indicate that the simulation with the SST transition turbulence model can predict the heat transfer characteristics in the blade cascade. The blade surface temperature decreases significantly and its temperature distribution is more uniform with an increase in the mass flow rates of the coolants. Moreover, when the mass flow rate ratio is increased from 0.01874 to 0.09371, the maximum temperature difference falls by 30 K and the average cooling efficiency of the blade surface rises by up to 17%. When the mass flow rate ratio is 0.07497, the best cooling efficiency of the blade could be obtained in this study. In addition, changing the flow directions of the second and fourth channels can reduce the temperature gradient and effectively improve the temperature distribution in the blade midchord region along spanwise, and adopting the double-inlet configuration in the trailing-edge region will lead to a lower temperature gradient and ameliorate the whole temperature distribution of the blade.