TRANSIENT HEAT-TRANSFER EXPERIMENTS IN A LINEAR CASCADE VIA AN INSERTION MECHANISM USING THE LIQUID-CRYSTAL TECHNIQUE

An insertion mechanism for a linear cascade allowing the displacement of one measurement airfoil to conduct transient heat transfer experime nts 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 measurem ent 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 exi t Reynolds numbers up to Re = 1.2E6. The transient liquid crystal meth od was used applying a digital image processing system capable of reco rding and storing the optical signal in real time. Comparisons were pe rformed with measurements conducted in the same test facility using th e naphthalene sublimation technique as well as thin film gages. Calcul ations were made with a two-dimensional boundary layer code.