Numerical Study on Improving Film Cooling Effectiveness With Double-wave Trench

Double-wave trench was proposed on the basis of transverse trench to get wider laterally coverage of the cooling jet. Film cooling characteristics have been numerically studied for transverse trench and double-wave trench. Meanwhile, the film cooling effectiveness of double-wave trench at different trench width (W = 0.8D, 1.4D, 2.1D) and trench depth (H = 0.75D, 1D) conditions are investigated. The results show that double-wave trench effectively improves the film cooling effectiveness and the uniformity of jet at the downstream. The span-wise averaged film cooling effectiveness of the double-wave trench model increases 20%∼63% comparing with that of the transverse trench at high blowing ratio condition. The anti-counter-rotating vortices which can press the film on near-wall are formed at the downstream double-wave trench. With the double-wave trench width decreasing, the film cooling effectiveness gradually decreases at the hole center-line region of the downstream trench, on the contrary, the cooling effectiveness increases at the hole middle region of the downstream trench, which is because of that narrowing trench width makes guidance action enhanced. With the increase of the trench depth, at low blowing ratio of 0.5 condition, the span-wise averaged film cooling effectiveness of downstream trench increases; at high blowing ratio of 2.0, the double-wave trench W = 2.1D condition, the span-wise averaged film cooling effectiveness is almost unchanged, but span-wise uniformity of jet is significantly improved.