DETAILED FILM-COOLING MEASUREMENTS ON A CYLINDRICAL LEADING-EDGE MODEL - EFFECT OF FREE-STREAM TURBULENCE AND COOLANT DENSITY

Detailed heat transfer coefficient and film effectiveness distribution s are presented on a cylindrical leading edge model using a transient liquid crystal technique. Tests were done in a low-speed wind tunnel o n a cylindrical model in a crossflow with two rows of injection holes. Mainstream Reynolds number based on the cylinder diameter was 100,900 . The two rows of injection holes were located at +/- 15 deg from stag nation. The film holes were spaced four hole diameters apart and were angled 30 and 90 deg to the surface in the spanwise and streamwise dir ections, respectively. Heat transfer coefficient and film effectivenes s distributions are presented on only one side of the front half of th e cylinder. The cylinder surface is coated with a thin layer of thermo chromic liquid crystals and a transient test is run to obtain the heat transfer coefficients and film effectiveness. Air and CO2 were used a s coolant to simulate coolant-to-mainstream density ratio effect. The effect of coolant blowing ratio was studied for blowing rations of 0.4 , 0.8, and 1.2. Results show that Nusselt numbers downstream of inject ion increase with an increase in blowing ratio for both coolants. Air provides highest effectiveness at blowing ratio of 0.4 and CO2 provide s highest effectiveness at a blowing ratio of 0.8. Higher density cool ant (CO2) provides lower Nusselt numbers at all blowing ratios compare d to lower density coolant (air). An increase in free-stream turbulenc e has very small effect on Nusselt numbers for both coolants. However, an increase in free-stream turbulence reduces film effectiveness sign ificantly at low blowing ratios for both coolants.