LOCAL HEAT TRANSFER COEFFICIENT AND FILM EFFECTIVENESS DISTRIBUTIONS ON A CYLINDRICAL LEADING EDGE MODEL USING A TRANSIENT LIQUID CRYSTAL IMAGE METHOD
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A transient liquid crystal technique is presented for measuring detailed heat transfer coefficients and film effectiveness on a cylindrical test model with film cooling. The technique uses a thin liquid crystal coating on the test surface and two similar transients tests. The cylinder, coated with a thin layer of liquid crystals, is heated to a uniform surface temperature and suddenly exposed to a cooler mainstream. The time history of color change at each pixel location is analyzed to obtain the local heat transfer coefficient and film effectiveness. Tests were run at a mainstream Reynolds number based on cylinder diameter of 100,900. The effect of blowing ratio on heat transfer coefficient and film effectiveness was studied for five blowing ratios ranging between 0.2 and 1.2. Two roles of holes at 15 from stagnation and hole spacing of four-hole diameters apart and angled at 30 and 90 to the surface in the spanwise and streamwise directions were used for coolant ejection. Air was used as coolant. Detailed distributions obtained using the present technique provide a better understanding of the film cooling phenomena on the cylinder surface. The technique provides high resolution and more accurate results compared with classic heat transfer measurement techniques. Some of the results from the present study are compared with results obtained using classic heat transfer measurement methods. Copyright 1996 by Begell House, Inc.
