[Show abstract][Hide abstract] ABSTRACT: This study performed detailed measurements of jet flows through a row of forward expanded holes into a mainstream over a concave surface using digital particle image velocimetry. Each of ejected holes had a streamwise inclined angle of 35° bounded on a concave sur-face with constant radius of 382 mm. The spacing of adjacent holes is 1.5D. The density and the momentum flux ratio of the mainstream to the jet flow were 1.0. Results show detailed 2D mean velocity maps on several horizontal and vertical planes and a 3D streamline pattern of jet mean velocity. The streamlines of 3D mean velocity clearly display different flow characteristics of the ejected jet flow along the transverse direction. In addition, the particle trajectory of a ring enclosing an ejected jet above the injection hole was also presented to show movement of jet.
[Show abstract][Hide abstract] ABSTRACT: Experimental results of film cooling effectiveness over a concave surface with two staggered rows are presented by employing transient liquid crystal thermography. Four different discrete hole configurations are used for the injection of jet flow, in-cluding a straight circular hole configuration with a spanwise injection angle (β) of 0° and three forward-expanded hole configurations with β = 0°, 45° and 90° respectively. In all test models there are two staggered rows of discrete holes with streamwise in-jection angle (γ) of 35°. Blowing ratios (M) are 0.5, 1.0, and 2.0. The effects of blowing ratio, hole expanded angle, and injection angle orientation on film cooling performance are investigated. The jet flow with M = 0.5 is fairly uniform along the wall surface. The lift-off phenomenon can be found in the jet flow with β = 0° for both cases of simple and compound angles at M = 1.0 and also exists among all test cases at M = 2.0 except for β = 90°. The lift-off effect results in a decrease in both η and h /h 0 . At β = 0°, the jet flow with a forward-expanded hole gives higher η and lower h /h 0 than a simple angle hole. At a fixed blowing ratio, the jet flow with compound angle holes has lower q /q 0 and thus provides better wall protection than that with simple angle holes. In the present study, the compound angle with β = 0° at M = 2.0 provides the best film-cooling protection over the concave surface among all the test configurations.
Journal of the Chinese Institute of Engineers. 01/2005; 28:827-836.