Effect of Blowing Ratio on the Internal Heat Transfer of a Cooled Nozzle Guide Vane in a Linear Cascade

Abstract

Experimental and computational heat transfer investigations are reported on the interior side of a nozzle guide vane (NGV) subjected to combined impingement and film cooling. The domain of study is a two-dimensional five-vane cascade having a space chord ratio of 0.88. The vane internal surface is cooled by dry air, supplied through the two impingement inserts: the front and the aft. The blowing ratio (ρcVc/ρmVm) is varied systematically by varying the coolant mass flow through the impingement chamber and also by changing the mainstream Reynolds number, but by keeping a fixed spacing (H) to jet diameter (d) ratio of 1.2. The surface temperature distributions, at certain locations of the vane interior surface, are measured by pasting strips of liquid crystal sheets. The vane interior surface temperature distribution is also obtained by the computations carried out by using shear stress transport (SST) k–ω turbulence model in the flow solver ansys fluent-14. The computational data are in good agreement with the measured values of temperature. The internal heat transfer coefficients are thence determined from the computational data. The results show that, when the blowing ratio is increased by increasing the coolant flow rate, the average internal surface temperature decreases. However, when the blowing ratio is varied by increasing the mainstream Reynolds number, the internal surface temperature increases. Further, the temperature variations are different all along the internal surface from the leading edge to the trailing edge and are largely dependent on the coolant flow distributions on the internal as well as the external sides.