Adiabatic Film Cooling Effectiveness Measurements Throughout Multirow Film Cooling Arrays

Abstract

Adiabatic film cooling effectiveness measurements are obtained using pressure-sensitive paint (PSP) on a flat film cooled surface. The effects of blowing ratio and hole spacing are investigated for four multirow arrays comprised of eight rows containing 52 holes of 3.8 mm diameter with 20 deg inclination angles and hole length-to-diameter ratio of 11.2. The four arrays investigated have two different hole-to-hole spacings composed of cylindrical and diffuser holes. For the first case, lateral and streamwise pitches are 7.5 times the diameter. For the second case, pitch-to-diameter ratio is 14 in lateral direction and 10 in the streamwise direction. The holes are in a staggered arrangement. Adiabatic effectiveness measurements are taken for a blowing ratio range of 0.3–1.2 and a density ratio of 1.5, with CO2 injected as the coolant. A thorough boundary layer analysis is presented, and data were taken using hotwire anemometry with air injection, with boundary layer, and turbulence measurements taken at multiple locations in order to characterize the boundary layer. Local effectiveness, laterally averaged effectiveness, boundary layer thickness, momentum thickness, turbulence intensity, and turbulence length scale are presented. For the cylindrical holes, at the first row of injection, the film jets are still attached at a blowing ratio of 0.3. By a blowing ratio of 0.5, the jet is observed to lift off, and then impinge back onto the test surface. At a blowing ratio of 1.2, the jets lift off, but reattach much further downstream, spreading the coolant further along the test surface. A thorough uncertainty analysis has been conducted in order to fully understand the presented measurements and any shortcomings of the measurement technique. The maximum uncertainty of effectiveness and blowing ratio is 0.02 counts of effectiveness and 3%, respectively.

Parametric experimental study on high porosity film cooling features on turbine blade geometries

“…Similarly, a range of studies have been carried out on the effect of injection angle. Reducing the angle between the mainstream and film hole is seen to have a positive effect on both the film cooling, by improving film attachment, as well as on internal cooling by increasing the hole length (Crawford, Kays, & Moffat, 1980) (Natsui, Little, Kapta, & Dees, 2017). However, it was noted by Andrews (1995) that the effect of reducing the streamwise injection angle would become more limited as the pitch to diameter ratio was decreased.…”

Numerical investigations of endwall film cooling design of a turbine vane using four-holes pattern

“…Some research works about film cooling are fundamental studies which are performed on a flat plate and concentrate on one parameter by isolating the effects of other parameters (Natsui et al , 2017; Wang et al , 2019; Zhang et al , 2019; Hou et al , 2019). Natsui et al (Natsui et al , 2017) measured the adiabatic film cooling effectiveness ( ƞ ) on a flat surface with multi-row arrays of film cooling holes by pressure-sensitive paint (PSP) method. With a thorough boundary layer analysis obtained by hotwire anemometry, the interaction of multi-row film cooling arrays is presented.…”