Film cooling characteristics of rows of round holes at various streamwise angles in a crossflow: Part I. Effectiveness

Film cooling effectiveness were studied experimentally on rows of cylindrical holes with streamwise angles of 30°, 60° and 90°, in a flat plate test facility with a zero pressure gradient. Detailed effectiveness and heat transfer results for a single cylindrical hole at the same inclinations have been presented in Yuen and Martinez-Botas [C.H.N. Yuen, R.F. Martinez-Botas, Film cooling characteristics of a single hole at various streamwise angles: Part I. Effectiveness, Int. J. Heat Mass Transfer 46 (2003) 221–235; C.H.N. Yuen, R.F. Martinez-Botas, Film cooling characteristics of a single hole at various streamwise angles: Part II. Heat transfer coefficient, Int. J. Heat Mass Transfer 46 (2003) 237–249] with the same test facility and measurement technique. This present investigation commenced with a single row of holes with two pitch-to-diameter ratios (p/D) of 3 and 6. It then presents and discusses the effects of introducing inline and staggered rows for each streamwise angle and pitch-to-diameter ratio. The row spacing in the inline and staggered rows is 12.5 diameters in the streamwise direction. The short but engine representative hole length (L/D = 4) is constant for all geometries. The blowing ratio ranges from 0.33 to 2, and the freestream Reynolds number based on the freestream velocity and hole diameter (ReD) was 8563. Both local values and laterally averaged ones are presented, the latter refers to the averaged value across the central hole. The current results are compared with the experimental results obtained by other researchers, the effects of the additional inline and staggered rows, and of the variations in injection angle, pitch-to-diameter ratio are described.The objectives of the present study are to provide a consistent set of measurements in terms of effectiveness and heat transfer coefficients presented in the companion paper [C.H.N. Yuen, R.F. Martinez-Botas, Film cooling characteristics of rows of round holes at various streamwise angles: Part II. Heat transfer coefficient, Int. J. Heat Mass Transfer, in press], obtained systematically with the same test facility, and to deliver a better understanding of film cooling performance. The present results also serve as a database with 105 test cases, in addition to the 21 cases presented in [C.H.N. Yuen, R.F. Martinez-Botas, Film cooling characteristics of a single hole at various streamwise angles: Part I. Effectiveness, Int. J. Heat Mass Transfer 46 (2003) 221–235], for future numerical modelling.