Experiment of discharge coefficients for small scale cylindrical holes

Discharge coefficients of small scale cylindrical holes were investigated experimentally. And the trend of air discharge coefficient in the condition of various geometry and flow parameters was considered in this paper. Discharge coefficient data were acquired with the diameter of 0.5, 1.0, 2.0 and 3.0 mm, the ratio of pitch to diameter of 5, 10 and 20, the ratio of length to diameter of 1, 2 and 4, the inclination angle of 30°, 60° and 90°, and the Reynolds number in the range of 0 and 6000. Moreover, influential factors were discussed. The experimental results show that the inclination angle of holes is one of the critical influential factors, the influence of the diameter of holes on discharge coefficients is distinct and the influences of the ratio of pitch to diameter and the ratio of length to diameter are different. The above results are of important significance in the design and research of small scale holes in film cooling and impingement cooling in the blades or vanes of aero-engines.