Transient Heat Transfer Experiments in a Linear Cascade Via an Insertion Mechanism Using the Liquid Crystal Technique

Abstract

An insertion mechanism for a linear cascade allowing the displacement of one measurement airfoil to conduct transient heat transfer experiments is introduced. A basic feature of the system is its capability to work in a continuously running tunnel driven by a compressor at steady-state conditions. The experiment is initiated by pulling the measurement airfoil very rapidly through the sidewalls of the cascade by means of a pneumatic cylinder. Heat transfer measurements were obtained on a turbine airfoil at different exit Mach numbers up to M = 0.8 and exit Reynolds numbers up to Re = 1.2E6. The transient liquid crystal method was used applying a digital image processing system capable of recording and storing the optical signal in real time. Comparisons were performed with measurements conducted in the same test facility using the naphthalene sublimation technique as well as thin film gages. Calculations were made with a two-dimensional boundary layer code.