Experimental study of heat-transfer and pressure-drop performances of a rotating two-pass channel with composite stepped skew ribs and internal effusion

Abstract

The full-field endwall Nusselt number (Nu) distribution, Fanning friction factor (f), and aerothermal performance index (API) of a rotating two-pass square channel with the stepped composite skew ribs and internal effusion are measured at rotation (Ro), Reynolds (Re) and buoyancy (Bu) numbers in the respective ranges of 0.05-0.4, 5000-15,000, and 0.003-0.325. The novel composite ribs in the static channel raise the area-average Nusselt numbers to 5.97-4.9 times Dittus-Boelter (D-B) correlation levels with Fanning friction factors between 13-9.6 times Blasius equation (B-E) values to give rise to the high aerothermal performance index (API∞) of 2.65-2.39. With rotation, the averaged Nusselt numbers on leading and trailing ribbed endwalls are, respectively modified to 1.1-1.62 and 0.94-1.42 times of the non-rotating values with the channel averaged Fanning friction factors increased to 1.01-1.31 times of the static-channel references. The minimum Nusselt number on each rotating endwall is identified and compared with its area-average Nusselt number to highlight the safety margin of surplus coolant flow rate for hot spot prevention when a cooling network in a gas turbine blade is designed with reference to the area-averaged heat transfer data. Empirical heat-transfer and pressure-drop correlations for the present rotating channel are generated to assist the relevant applications.