Numerical Investigation of Stator Clocking Effects on the Downstream Stator in a 1.5-Stage Axial Turbine

The unsteady nature of the flow in multi-stage turbomachines makes it possible for designers to improve the aerodynamic performance by changing the relative pitchwise positions of consecutive stators/rotors. An in-house three-dimensional multi-stage flow solver with a volume-weighted interpolation method on the interface between adjacent blade rows is employed to compute the unsteady flow in a 1.5-stage axial turbine. The variation of entropy at the inlet of the second stator and the pressure fluctuation over the second stator blade are firstly presented to illustrate the unsteady wake characteristics and the development of pressure fluctuations in the second stator passages. Then the variations of overall aerodynamic parameters, wake characteristics and pressure fluctuations at 50% span position are further investigated for five different stator clocking configurations. The results are presented in detail, demonstrating that at 50% span position the adiabatic efficiency of the stage increases for the configurations with the upstream stator wake cores passing through the downstream stator passages near the suction side. For the fluctuation produced by the impingement of upstream low entropy on the stator blade, the amplitude is much greater for the clocking configuration with higher efficiency. However, for the fluctuation produced by the collision of two other fluctuations, the amplitude is larger for the clocking configuration with lower efficiency.