Method and Measurement of Adiabatic Wall Temperature Downstream of a High Pressure Turbine Using Thin-Film Sensors

Abstract

During engine development, heat loads in the turbomachinery are analyzed based on theoretical and numerical estimates together with correlations. Accurate models of the convective fluxes are vital to assess the thermo-mechanical integrity. This paper reports an experimental heat transfer research in a 1.5 turbine stage, the researched model is a the structural vane of a multi-splittered low pressure vane located downstream of a high pressure turbine stage. This concept is envisioned for ultra-high bypass-ratio aero-engines with a swan-neck diffuser between the high-pressure turbine and the low-pressure turbine. Measurements were performed in the large compression tube facility of the von Karman Institute, at representative conditions of modern aero-engines. Double-layered thin film gauges were employed for the measurement of the time-dependent temperature distribution around the airfoil. The initial temperature of the structural vane was adjusted using a heating system. The experimental procedure has allowed the determination of the time-mean and unsteady adiabatic wall temperature. Hence this technique allows the determination of the non-dimensional Nusselt number and proper scaling of the surface temperature to engine conditions. Furthermore, the analysis of the unsteady data reveals the contribution of the temperature fluctuations to the unsteady heat fluxes.