Effect of Unsteady Wake on Detailed Heat Transfer Coefficient and Film Effectiveness Distributions for a Gas Turbine Blade

Abstract

Unsteady wake effects on detailed heat transfer coefficient and film cooling effectiveness distributions from a gas turbine blade with film cooling are obtained using a transient liquid crystal technique. Tests were performed on a five-blade linear cascade at a axial chord Reynolds number of 5.3 × 105 at cascade exit. Upstream unsteady wakes are simulated using a spoke-wheel type wake generator. The test blade has three rows of film holes on the leading edge and two rows each on the pressure and suction surfaces. Air and CO2 were used as coolants to simulate different coolant-to-mainstream density ratio effect. Coolant blowing ratio for air injection is varied from 0.8 to 1.2 and is varied from 0.4 to 1.2 for CO2. Results show that Nusselt numbers for a film-cooled blade are much higher compared to a blade without film injection. Particularly, film injection causes earlier boundary layer transition on the suction surface. Unsteady wakes slightly enhance Nusselt numbers but significantly reduce film cooling effectiveness on a film-cooled blade compared with a film-cooled blade without wakes. Nusselt numbers increase slightly but film cooling effectiveness increases significantly with an increase in blowing ratio for CO2 injection. Higher density coolant (CO2) provides higher effectiveness at higher blowing ratios (M = 1.2) whereas lower density coolant (Air) provides higher effectiveness at lower blowing ratios (M = 0.8).

Unsteady Pressure Field Investigation of an Axial Fan—Inlet and Outlet Unsteady Pressure Field Measurement

“…profiles of the gas turbine blades as reported by Du, Han, and Ekkad (1998). It is shown that the pressure and velocity fluctuations are caused by the upstream passing wakes, for which again the testing results are in agreement with the theoretical analysis section.…”

Film cooling on a turbine guide vane: A numerical analysis with a multigrid technique

“…A substantial number of experimental investigations have been performed to demonstrate coolant behaviour and effectiveness on at plates, turbine blades and endwalls. Representative examples of the studies of lm cooling over turbine blades are Camci and Arts [3,4], Du et al [5], Ames [6] and, most recently, Drost and Bolcs [7]. The overall conclusion was that lm cooling provides better cooling effectiveness on the suction surface compared with that on the pressure surface.…”