In order to reveal the effects of the hot streak/airfoil count ratio on the heating patterns of high pressure turbine rotor blades in a Vaneless Counter-Rotating Turbine, three-dimensional unsteady Navier-Stokes simulations have been performed. In these simulations, the ratio of the number of hot streaks to the number of the high pressure turbine vanes and rotors is 1:3:3, 1:2:2, 2:3:3 and 1:1:1, respectively. The numerical results show that the migration characteristics of the hot streak in the high pressure turbine rotor are predominated by the combined effects of secondary flow and buoyancy. The combined effects induce the high temperature fluid migrate towards the hub in the high pressure turbine rotor. And the combined effects become more intensified when the hot streak/airfoil count ratio increases. The results also indicate that the peak temperature of the hot streak is dissipated as the hot streak goes through the high pressure turbine vane or the rotor. The dissipated extent of the peak temperature in the high pressure turbine stator and the rotor is increased as the hot streak-to-airfoil ratio increases. And the increase of the hot streak/airfoil count ratio trends to increase the relative Mach number at the high pressure turbine outlet. The relative flow angle from 23% to 73% span at the high pressure turbine outlet decreases as the hot streak-to-airfoil ratio increases. The results also indicate that the isentropic efficiency of the Vaneless Counter-Rotating Turbine is decreased as the hot streak/airfoil count ratio increases.

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