Detailed Experimental Measurement and RANS Simulation of a Low Pressure Turbine With High Lift Blading

Abstract

The aerodynamic characteristics of high–lift airfoil designs is of interest for improved performance and reduced blade count in Low–Pressure Turbine (LPT) design. The present paper presents both experimental measurements as well as numerical simulation results from a single-stage LPT. The airfoils were designed for an embedded stage with a total pressure expansion ratio of 1.75 and a rotor Zweifel coefficient of 1.35. The measurement program was highly unique in that detailed measurements were obtained using a variety of different probe types, including time–resolved total pressure and hot–wires. Agreement between various measurement types was generally good, but differences beyond typically stated uncertainty bounds were noted. The computations were done using RANS and a mixing model via commercially available software. The numerical results were evaluated to determine the efficacy of this type of model for prediction and design of high–lift airfoils. The computations agreed very well with the experimental results in the midspan region, but losses were over–predicted in the lower 40% span near the hub. A basic description and understanding of the flow physics in the LPT stage are presented based on the relative agreement between the experiments and computations.

Assessment of RANS Turbulence Models on Simplified Geometries Representative of Turbine Blade Tip Shroud Flow

“…Main studies on the cavity and labyrinth flows have used the k − ω SST turbulence model with a Kato-Launder limiter [1][2][3]. Perez et al [4] have preferred a simpler oneequation Spalart-Allmaras model to simulate a single stage turbine with purge flow emanating from an upstream hub cavity. The authors noted that the simulation overpredicts the pressure losses between 20% and 40% in channel height, which corresponds approximately to the position of the passage vortex.…”