Film Cooling Effectiveness for Three Row Compound Hole Design on Flat Plate Using PSP Technique

Abstract

A comprehensive study was performed to investigate effects of geometrical and coolant flow parameters for a three row compound hole design over a flat plate. These included β: +45 and -45, in-line and stagger arrangement, hole spacing (4d, 6d and 8d), five blowing ratios (0.5-1.5) and three density ratios (1.0, 1.5, 2.0). The mainstream Reynold’s number was kept constant at 285,000 with a turbulence intensity of 6%. Average effectiveness plots and contours were developed using Pressure Sensitive Paint (PSP) technique and cross comparisons were carried out.

The parametric results obtained from experimentation generally agreed with widely accepted trends: the cascade effect of coolant jets for multi hole design increases overall effectiveness especially at large x/d, increasing density ratio increases effectiveness particularly at higher blowing ratio and increasing hole spacing has a detrimental effect on film cooling. However, few of the more interesting observations included: stagger arrangement is not always the most optimum design (β: +45, -45, -45 with staggered 2nd and 3rd row reported the lowest effectiveness for all blowing ratios and density ratios); inline arrangement of holes with opposing orientation angles (β: +45, -45, -45) yields better effectiveness; blowing ratio effect is strongly dependent on geometric design. Moreover, hole spacing effect is closely related to neighboring coolant jet coalescence and interaction with mainstream flow.

Currently, little data is available on three row design in open literature; this study provides systematic, baseline information for future studies.