Heat transfer measurements in an annular cascade of transonic gas turbine blades using the transient liquid crystal technique

Heat transfer measurements have been made in the Oxford University Cold Heat transfer Tunnel employing the transient liquid crystal technique. Complete contours of that transfer coefficient have been obtained on the aerofoil surfaces of a large annular cascade of high-pressure nozzle guide vanes (mean blade diameter of 1.11 m and axial chord of 0.0664 m). The measurements are made at engine representative Mach and Reynolds numbers (exit Mach number 0.96 and Reynolds number 2.0 {times} 10{sup 6}). A novel mechanisms used to isolate five preheated blades in the annulus before an unheated flow of air passes over the vanes, creating a step change, in heat transfer. The surfaces of interest are coated with narrow-band thermochromic liquid crystals and the color crystal change is recorded during the run with a miniature CCD video camera. The heat transfer coefficient is obtained by solving the one-dimensional heat transfer equation for all the points of interest. This paper will describe the experimental technique and present results of heat transfer and flow visualization.