Near-Wall Flow in Turbomachinery Cascades—Results of a German Collaborative Project

Abstract

This article provides a summarizing account of the results obtained in the current collaborative work of four research institutes concerning near-wall flow in turbomachinery. Specific questions regarding the influences of boundary layer development on blades and endwalls as well as loss mechanisms due to secondary flow are investigated. These address skewness, periodical distortion, wake interaction and heat transfer, among others. Several test rigs with modifiable configurations are used for the experimental investigations including an axial low speed compressor, an axial high-speed wind tunnel, and an axial low-speed turbine. Approved stationary and time resolving measurements techniques are applied in combination with custom hot-film sensor-arrays. The experiments are complemented by URANS simulations, and one group focusses on turbulence-resolving simulations to elucidate the specific impact of rotation. Juxtaposing and interlacing their results the four groups provide a broad picture of the underlying phenomena, ranging from compressors to turbines, from isothermal to non-adiabatic, and from incompressible to compressible flows.

Characterization of the Endwall Flow in a Low-Pressure Turbine Cascade Perturbed by Periodically Incoming Wakes, Part 1: Flow Field Investigations with Phase-Locked Particle Image Velocimetry

“…Despite the vast research activity in recent years, the accurate prediction and reduction of endwall loss is expected to remain a challenge for many years to come [3]. Aimed at providing a further step in the continued understanding of endwall flow and its determining factors, an extensive research program funded by the Deutsche Forschungsgemeinschaft (DFG) was launched in 2018 by four German university institutes, see Engelmann et al [12]. Within this conglomerate, the Institute of Jet Propulsion of the University of the Bundeswehr Munich covered low-pressure turbine aspects at high-speed flow conditions.…”

Accuracy of the Gamma Re-Theta Transition Model for Simulating the DU-91-W2-250 Airfoil at High Reynolds Numbers

“…Developing a reliable transition model for general-purpose CFD codes is not an easy task for several reasons. First of all, there is no single mechanism for the transition process [29][30][31][32][33][34]. The second reason is related to conventional Reynolds averaged Navier-Stokes (RANS) procedures, which are not suitable for describing transient flow processes, where both linear and nonlinear effects are crucial [35].…”