Louver and effusion cooling heat transfer for a double wall effusion plate with impingement jet array coolant supply

Abstract

Louver slot cooling is employed, which consists of an aligned collection of film cooling holes, contained within a specially-designed device which concentrates, and directs the coolant from a slot, so that cooling air then advects as a layer downstream along the test surface. This louver-supplied coolant is then supplemented by coolant which emerges from different rows of downstream film cooling holes. Coolant for both cooling arrangements is supplied using an array of impingement jets. Experimental data are provided for a mainstream Reynolds number Rems range of 168,000–181,000. Full-coverage film cooling initial blowing ratio values are 2.5, 3.2, 4.4, and 5.2, with respective louver slot blowing ratios of 1.2, 1.5, 2.1, and 2.4. Measured lateral-averaged adiabatic effectiveness results show that, with impingement supply cooling only, for blowing ratios of 4.4 and lower, the louver and effusion cooling arrangement generally provides higher effectiveness, relative to an effusion cooling only arrangement. For all blowing ratios considered, another advantage of the louver slot is more uniform values of increased effectiveness along the entire test surface, including locations which are just downstream of the slot. Relatively weak dependence on blowing ratio is present for the louver and film cooling arrangement, in contrast to the effusion only configuration, where effectiveness data generally increase progressively and substantially (at most x/de locations) as the blowing ratio becomes larger. Lateral-averaged heat transfer coefficient values for the effusion cooling only arrangement, and for the louver and effusion cooling arrangement, are approximately quantitatively similar when the blowing ratio is 4.3 to 4.4. Data for blowing ratios BR of 5.2 to 5.5 show that the louver and effusion cooling gives much lower lateral-averaged heat transfer coefficients, compared to the effusion cooling only arrangement. This is a result of reduced local turbulent thermal transport levels within the wake flows which are present downstream of the louver leap device.