On Improving Full-Coverage Effusion Cooling Efficiency by Varying Cooling Arrangements and Wall Thickness in Double Wall Cooling Application

Abstract

Overall cooling effectiveness was determined for a full-coverage effusion cooled surface which simulated a portion of a double wall cooling gas turbine blade. The overall cooling effectiveness was measured with high thermal-conductivity artificial marble using infrared thermography. The Biot number of artificial marble was matched to real gas turbine blade conditions. Blowing ratio ranged from 0.5 to 2.5 with the density ratio of DR = 1.5. A variation of cooling arrangements, including impingement-only, film cooling-only, film cooling with impingement, and film cooling with impingement and pins, as well as forward/backward film injection, was employed to provide a systematic understanding on their contribution to improve cooling efficiency. Also investigated was the effect of reducing wall thickness. Local, laterally averaged, and area-averaged overall cooling effectiveness were shown to illustrate the effects of cooling arrangements and wall thickness. Results showed that adding impingement and pins to film cooling, and decreasing wall thickness increase the cooling efficiency significantly. Also observed was that adopting backward injection for thin full-coverage effusion plate improves the cooling efficiency.

Comparison of Showerhead Film Cooling and Double Wall Cooling in a Guide Vane Leading Edge with Hot Streak

“…Using infrared thermography and particle image velocimetry techniques, Shrager et al [20,21] measured the overall effectiveness and time-averaged flow field of a DWC test panel. Furthermore, Ren et al [22] and Li et al [23] experimentally investigated heat transfer characteristics of different DWC flat plates. By means of high temperature wind tunnel and infrared thermal imaging system, Wang et al [24] compared the temperature fields of a DWC endwall and a simple film cooled endwall, their results indicated that in comparison with the simple film cooled endwall, the DWC endwall can decease not only the endwall temperature, but also the temperature gradient on the endwall surface.…”

Coupled Aerothermal-Mechanical Analysis in Single Crystal Double Wall Transpiration Cooled Gas Turbine Blades with a Large Film Hole Density

“…To achieve this, effusion and transpiration type systems [7,8] with arrays of film cooling holes are being considered, which offer the benefits of higher internal surface area and elevated external film protection [9,10]. Recently, the double wall transpiration cooling (DWTC) system has been proposed to enhance the cooling capability through a combination of film and impingement cooling [11].…”

“…The wall-connecting pedestals resist bursting loads and facilitate thermal conduction between the hotter outer wall and cooler inner wall. The outstanding cooling effectiveness of DWTC systems has been demonstrated through Computational Fluid Dynamics (CFD) analysis and empirical correlations by a number of authors, including Li et al [11], Murray et al [1] and Ngetich et al [12]. The beneficial effect of film hole density, i.e.…”