Comparison of a State of the Art and a High Stage Loading Rotor

Abstract

This paper presents measurement results of a 1½ stage LPT test rig at Graz University of Technology incorporating two different rotor geometries: one with a regular blade loading and a second rotor with a highly loaded blade geometry. The test rig was designed in cooperation with MTU Aero Engines and represents the last 1.5 stages of a commercial aero engine. Considerable efforts were put on the adjustment of all relevant model parameters (Mach number, blade count ratio, airfoil aspect ratio, blade loading, etc.) to reproduce the full scale LPT situation. The rig diameter is approximately half of that of a commercial aero engine LPT. The number of blades and vanes for the two investigated stages as well as the pressure ratio and power output are identical, resulting in a decrease in rotational speed of the HSL rotor. Measurement data from a fast response pressure probe (FRAPP) is used to compare the flow fields of the two different stages.The effect of the different stage designs can be seen when comparing the exit flow fields. The highly loaded stage shows a more pronounced tip leakage vortex compared to the datum stage. The highly loaded stage shows wider wakes with a lower total pressure deficit. The fluctuations of total pressure within the flow field are directly related to the upstream wake. If the measurement position is located within a stator wake, the fluctuations are significantly smaller than out of the wake.