Unsteady Wake Effect on Film Temperature and Effectiveness Distributions for a Gas Turbine Blade

Abstract

The film effectiveness and coolant jet temperature profile on the suction side of a gas turbine blade were measured using a transient liquid crystal and a cold-wire technique, respectively. The blade has only one row of film holes near the gill hole portion on the suction side of the blade. Tests were performed on a five-blade linear cascade in a low-speed wind tunnel. The mainstream Reynolds number based on cascade exit velocity was 5.3×105. Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. Coolant blowing ratio was varied from 0.6 to 1.2. Wake Strouhal number was kept at 0 and 0.1. Results show that unsteady wake reduces film cooling effectiveness. Results also show that film injection enhances local heat transfer coefficient while the unsteady wake promotes earlier boundary-layer transition. The development of coolant jet temperature profiles could be used to explain the film cooling performance. [S0889-504X(00)00402-5]

Numerical and experimental investigation of a new film cooling geometry with high P/D ratio

“…In order to measure the coolant effectiveness a temperature gradient is required between the coolant and the main stream. As common practice in the open literature (Coat and Lock [14], Teng et al [15]), an inverse coolant design is used where the coolant flow is heated up. During the tests the "coolant" is warmed up before entering in the recirculation channel in order to match the temperature operating conditions for the Thermocromic Liquid Crystal (TLC).…”

Turbine Blade Film Cooling Using PSP Technique

“…A reduction in film cooling effectiveness due to the unsteady wake was observed across the board. Teng et al (2000) used cold-wire anemometry to measure the mean and fluctuating temperature profiles within the film cooling jet. Increased turbulence in the boundary layer can be clearly observed in the unsteady wake case, which results in shorter coolant traces.…”

DNS study of pulsed film cooling for enhanced cooling effectiveness

“…The aerodynamics in blade passages is an inherently unsteady process which has a significant impact on the film-cooling effectiveness [1]. In addition, with coolant injection, large-scale structures result from the interaction of the film-cooling jet with the crossflow.…”