Comparative numerical investigation of wake effect on low-pressure turbine endwall flow

Abstract

In low-pressure turbine linear cascade experiments, the upstream stator vanes are often modeled by moving bar wake generators. Different from the majority of the earlier wake effect research which is concerned with less aggressively loaded airfoils, here front-loaded high-lift airfoils are considered for both stator and rotor. Implicit large-eddy simulations of the flow through a 50% reaction stage with stator vanes and rotor blades as well as a linear cascade with bar wake generators and rotor blades were carried out and the wake effect on the flow through the rotor was investigated. The chord-based Reynolds number for the simulations was 100,000. For the chosen front-loaded high-lift airfoil the stator wake is dominated by pronounced endwall structures which are lacking for the bar wake generator. Instantaneous flow visualizations reveal a periodic suppression of the two-dimensional rotor blade suction-side separation for both configurations. With upstream stator vanes, the wake endwall structures appear to be chiefly responsible for the suppression of the rotor blade passage vortex and corner separation. For the bar wake generator, the wakes are wider and the wake effect is spread out over a larger portion of the wake passing period. The passage vortex and corner separation remain mostly intact.