No abstract

Film cooling effectiveness were studied experimentally on rows of cylindrical holes with streamwise angles of 30°, 60°a nd 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 (Re D ) 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.

No abstract

No abstract

The steady-state wide band liquid crystal technique is used to study the film cooling performance downstream of a variety of geometries in a flat plate. This technique provides a detailed measurement of both cooling effectiveness and heat transfer coefficient. This paper presents the effects of compound and fan–shaped holes, the effect of streamwise angle variation has been presented at previous meetings. The following configurations are investigated: a single hole, a row of holes with a pitch-to-diameter ratio, p/D, of 3, two inline rows with p/D of 3 and two staggered rows with p/D of 6; all with a stream–wise angle of 30°. The spacing between two rows was chosen as 12.4D. Two lateral injection are investigated: 30° and 60° compound angle. The fan shaped hole used comprised of a lateral expansion of 14° from the original simple cylindrical shape with streamwise inclination of 30°; forward expansion was not incorporated. The length-to-diameter ratio, L/D, was maintained at a value of 4 for all the compound cases, the L/D for the fan shaped-hole was 6, larger due to its physical limitation. The tests were performed with a jet-to-freestream density ratio of 1.5; achieved by using a foreign gas (CO2) injection. The range of momentum flux ratios (M) covered was 0.33 to 1.67. The row of 30° compound angle holes gave a lower value of effectiveness when compared to the non-compound case at M<0.67, but greater values and coverage at M>1.0, consistent with previous experiments. The row of 60° compound angle gave greater effectiveness, coverage and uniformity than the row of 30° compound at a given blowing ratio; the jet-to-jet interaction was greater for the 60° row due to the added lateral momentum. The row of 60° compound gave an increase of order 100% relative to the non-compounded row for M>1. Two inline rows of fan-shape holes delivered less effectiveness than the corresponding single row at the same spanwise distance for a given jet fluid mass, or blowing ratio with twice the jet fluid mass. For equal blowing ratios and equal flow rates the fan-shaped hole gave a much higher effectiveness.