Adiabatic and Overall Effectiveness for the Showerhead Film Cooling of a Turbine Vane

Abstract

There have been a number of previous studies of the adiabatic film effectiveness for the showerhead region of a turbine vane, but no previous studies of the overall cooling effectiveness. The overall cooling effectiveness is a measure of the external surface temperature relative to the mainstream temperature and the inlet coolant temperature, and consequently is a direct measure of how effectively the surface is cooled. This can be determined experimentally when the model is constructed so that the Biot number is similar to that of engine components, and the internal cooling is designed so that the ratio of the external to internal heat transfer coefficient is matched to that of the engine. In this study, the overall effectiveness was experimentally measured on a model turbine vane constructed of a material to match Bi for engine conditions. The model incorporated an internal impingement cooling configuration. The cooling design consisted of a showerhead composed of five rows of holes with one additional row on both pressure and suction sides of the vane. An identical model was also constructed out of low conductivity foam to measure adiabatic film effectiveness. Of particular interest in this study was to use the overall cooling effectiveness measurements to identify local hot spots which might lead to failure of the vane. Furthermore, the experimental measurements provided an important database for evaluation of CFD simulations of the conjugate heat transfer effects that occur in the showerhead region. Continuous improvement in both measures of performance was demonstrated with increasing momentum flux ratio.

Overall Effectiveness of a Blade Endwall With Jet Impingement and Film Cooling

“…Although engine relevance was limited because matched Bi and h^lh, were not confirmed, these studies improved understanding of the thermal fields of a conducting vane and provided experimental data for benchmarking computational work. Nathan et al [14] measured (p on the stagnation region of the vane, which was cooled intemally with impingement and extemally with a showerhead arrangement of cooling holes. Nathan et al [14] measured (p on the stagnation region of the vane, which was cooled intemally with impingement and extemally with a showerhead arrangement of cooling holes.…”

Experimental investigation of the interaction between showerhead coolant jets and main flow

“…However, this increase in the adiabatic effectiveness had been adversely affected by high mainstream turbulence [9]. Nathan et al [10] also measured adiabatic film cooling effectiveness in the showerhead region of a model of a C3X turbine vane by increasing the momentum flux ratio up to I = 6.7. Their results were consistent with [7] and [8].…”

Conjugate Heat Transfer Study of Combined Impingement and Showerhead Film Cooling Near NGV Leading Edge

“…Here is the wall temperature under conjugate condition. The values of adiabatic and overall cooling effectiveness at the leading edge region of a turbine vane with internal impingement cooling were compared by Nathan et al [12]. They reported that the values of Φ are equivalent to the actual engine values and are higher compared to the adiabatic effectiveness.…”