777 Shaped Film Cooling Hole
The Penn State START lab developed a baseline film cooling hole referred to as the 7-7-7 shaped hole, which is now used for experimental and computational studies in over 50 organizations. Numerous experimental and computational simulations have been conducted on this publicly available 7-7-7 shaped film cooling hole including detailed flow and heat transfer data sets. The cooling hole was meant to be a baseline (not necessarily an optimal) cooling hold that is relevant to many shaped holes found in engine hardware today. (https://sites.psu.edu/turbine/public-shaped-hole/)
Solid model drawings of the 7-7-7 shaped film cooling hole and plate array in solid body format to improve accuracy of the conjugate heat transfer simulations.
An illustration showing a subset of the experimental data is given below, which is a quantification of the streamwise and lateral velocity fields including turbulence levels. The contours show the three dimensional complexity of the flow field in the vicinity of the hole exit-plane in which the cooling air was found to mix rapidly with the warmer mainstream flow. The resulting flow field circulation patterns that develop significantly influence the mainstream temperature flow field and the local solid wall thermal distribution.
Experimental setup of the 7-7-7 shaped hole and example turbulence intensity contours from mainstream PIV velocity measurements.
Experimental setup of the 7-7-7 shaped hole and example thermal contours from mainstream temperature measurements.
Experimental data sets and analyses for the 7-7-7 shaped film cooling holes have been conducted in a conjugate model constructed using additive manufacturing with a co- and counter-flow feed channel. The coupon and cooling hole geometry were manufactured at true engine scale and the holes were compared using the conventional EDM drilled holes as well as the 3D printed holes. The experimental test apparatus is shown in which an infrared camera is used to view the mainstream channel side of the coupon through a Zinc Selenide window that is positioned directly over the coupon.
Experimental test apparatus used to study the additively manufactured flat plate coupon containing the 7-7-7 shape film cooling holes at true engine scale.
The mainstream and internal channel dimensions were sized to ensure that the Reynolds numbers, Biot number, and ratio of external-to-internal convective heat transfer coefficients (h¥/hi) were engine representative. The internal channel Reynolds number was varied in the range of approximately 10,000 to 15,000, while the Biot number and the convection ratio h¥/hi were held constant at Bi = 0.1 and h¥/hi = 1.0. The density ratio of the internal channel cooling flow to the mainstream warm flow was also engine representative and held constant at DR =1.7.
The film cooling holes within the coupon were photographed using a scanning electron microscope (SEM) as shown in Figure X to help visualize the wall surface quality within the holes. Cooling flow passing through the shaped cooling holes were quantified in terms of a flow parameter versus pressure ratio across the hole. Example results from the tests at two different internal channel Reynolds numbers. The thermal performance results of the coupon and cooling hole design are plotted in the form of overall cooling effectiveness which show values near f = 0.4 to 0.6 that are representative of those experienced within actual turbine components in real engines. The geometries and test results from these flat plate coupon experiments are being used to help benchmark the conjugate heat transfer simulation models.
Micrographs of a shaped film cooling hole within the additively manufactured coupon taken using a scanning electron microscope.
Experimental test results showing contours of overall cooling effectiveness for the additively manufactured coupon having 7-7-7 shaped film cooling holes compared with tradition electron discharge machining (EDM).