Investigation of Film Cooling Effectiveness of Full-Coverage Inclined Multihole Walls With Different Hole Arrangements

Abstract

An experimental and numerical investigation of adiabatic film cooling effectiveness was conducted on four full-coverage inclined multihole walls with different hole arrangements. The hole geometrical patterns and the test conditions were chosen to be representative of film cooling designs for modern aeroengine combustor liners. The four hole arrangements were grouped into two types based on lateral hole pitch ( P ) and streamwise row spacing ( S ). One type included two test plates which had the same S and P (S/P = 2) and compound angle (β = 0 deg) but different hole inclination angles ( α ) (30 and 150 deg ). The other type included two test plates which had the same S and P (but S/P = 1) and inclination angle (α = 30 deg) but different compound angles (0 deg and 50 deg). Heat-mass transfer analogy method was employed to investigate the adiabatic film cooling effectiveness of these multihole walls with typical blowing ratios for aeroengine combustors. The numerical simulation was performed to characterize the flowfield and temperature distribution, aiming to further understand the film cooling mechanisms. The experimental results indicated that blowing ratio within the range from 1 to 4 had negligible influence on adiabatic film cooling effectiveness (η) in the case of concurrent coolant injection while hole arrangement had large effect on η. But the blowing ratio within the range from 1 to 4 had large effect on the film cooling effectiveness for the counterflow film cooling scheme. The numerical results were compared with experimental data and fairly good agreement was obtained. The numerical simulation revealed the flow structure, particularly exhibiting significant influence of the interaction between mainstream flow and coolant jets on η. With validation by experimental data, film cooling numerical simulation seems quite helpful in selecting optimum multihole arrangement for modern combustor liner design.

Flow characteristics in an annular burner with fully film cooling

“…For a proper distribution of film-cooling holes, generally, the air film is very uniform and can entirely protect the tube walls from the hot gas or flame. However, a strong injection from the [17], which shows most of colder air is injected into the tube from the dilution holes, not from the tiny cooling holes. This results in the very bad film coverage or even no film covering on the downstream areas of the dilution holes.…”

A 3-dimensional, coupled, DNS, heat transfer model and solution for multi-hole cooling

“…of the cooling system. The direct effect of the coolant jet, which is often evaluated by using an adiabatic wall, has been investigated widely as in Lin et al [1] and Fric et al [2], and it is a dominant effect at high blowing ratio (M P 1). The other two effects, however, can be more important for a high efficiency, low blowing ratio cooling system, such as a multihole cooling system for multi-hole CMC materials that can have a relatively large number of holes and percentage open area with minimal cost penalty.…”

Full-Coverage Film Cooling: Heat Transfer Coefficients and Film Effectiveness for a Sparse Hole Array at Different Blowing Ratios and Contraction Ratios

“…They consider spanwise hole spacings Y/D of 8, 10, and 14, and present results in the form of spatially averaged-adiabatic effectiveness with very little variation between a BR of 1.0 and 2.0. Lin et al [16] show that, for a range of BRs from 1 to 4 and hole spacings of X/D ¼ 8, Y/D ¼ 4 and X/D ¼ 5.67, Y/D ¼ 5.67, holes inclined in the direction of the freestream show negligible performance change with increasing BR. The authors generally report an increase in effectiveness with increasing BR.…”