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

Abstract

Ever increasing thermal loads on gas turbine components require improved cooling schemes to extend component life. Engine designers often rely on multiple thermal protection techniques, including internal cooling and external film cooling. A conjugate heat transfer model for the endwall of a seven blade cascade was developed to examine the impact of both convective cooling and solid conduction through the endwall. Appropriate parameters were scaled to ensure engine relevant temperatures were reported. External film cooling and internal jet impingement cooling were tested separately and together for their combined effects. Experiments with only film cooling showed high effectiveness around film cooling holes due to convective cooling within the holes. Internal impingement cooling provided more uniform effectiveness than film cooling, and impingement effectiveness improved markedly with increasing blowing ratio. Combining internal impingement and external film cooling produced overall effectiveness values as high as 0.4. A simplified one-dimensional heat transfer analysis was used to develop a prediction of the combined overall effectiveness using results from impingement only and film cooling only cases. The analysis resulted in relatively good predictions, which served to reinforce the consistency of the experimental data.