A Numerical Investigation of Stator-Rotor Interaction Effects on Flow Field and Film Cooling Effectiveness in a 3D Transonic Turbine Stage With Highly Twisted Rotors

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To reduce aerodynamic losses and optimize turbine blade cooling designs, a comprehensive understanding of rotor-stator interaction effects on the blade aerodynamics and film cooling performance is essential. This paper focuses on the numerical analysis of the interactions between shock waves and unsteady wakes and their effects on cooling effectiveness of a highly twisted rotor within a transonic turbine stage. The parameters of the turbine stage are from the Pratt & Whitney Energy Efficient Engine (E3) program. The Realizable k-ε turbulence model was selected as the suitable turbulence model by our previous study. The investigation is conducted first by analyzing mean static pressure and the Root Mean Square (RMS) of the static pressure, followed by a detailed study of the flow field in the rotor passage at blowing ratios (Br) of 0.5, 1.0 and 1.5. Effects of the complicated interactions among shock waves, trailing edge wake shedding, and blockage of moving rotors are separated and identified individually through shock strength, vortices, and entropy production. The results show that: 1) For the stator, the shock waves emanating from the trailing edge of the neighboring stator impinging on the later part of the stator’s suction side, creating static pressure fluctuations as large as 20%. 2) For the rotor, the variation of static pressure is synchronized with the rotor passing frequency, but out of phase between the suction and pressure sides. 3) A high entropy region generated by the wake flow from the upstream trailing edge in the rotor passage intensifies and moves towards the rotor hub during the rotor passing periods. 4) Most of the cooling air injected from the rotor leading edge bends towards the suction side, and the cooling air injected from the pressure side turns towards the rotor hub. 5) An increase in the blowing ratio from Br = 0.5 to Br = 1.5 does not affect the pressure fluctuations, but does significantly increase film cooling effectiveness on the rotor pressure side. 6) The mean static pressure on the suction side of the twist blade is lower than a straight blade, indicating the benefit of producing larger torque by using twist rotors.