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Ever-increasing thermal loads on gas turbine components require improved cooling schemes to extend component life. Engine designers often rely on multiple thermal pro-tection 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 impinge-ment 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 cool-ing only cases. The analysis resulted in relatively good predictions, which served to rein-force the consistency of the experimental data. [DOI: 10.1115/1.4025835

Fire fighters are exposed to highly variable thermal environments including elevated temperatures, convective heat flux, and radiant heat flux, which can put a significant burden on personal protective equipment. Thermally degraded and melted self-contained breathing apparatus (SCBA) facepieces have been identified as a contributing factor in certain fire fighter fatalities and injuries in the United States. At the current time, standard performance tests for SCBA facepieces are conducted at less severe thermal conditions than other components of a fire fighter's ensemble and equipment. In order to better understand the level of thermal performance of the SCBA facepiece lens and to develop an improved performance test method, facepieces were exposed to controlled and well characterized elevated thermal environments. In these experiments, SCBA facepieces were exposed to radiant heat fluxes of 2 kW/m 2 to 15 kW/m 2 from a natural gas fired radiant panel apparatus. The facepieces were mounted on a headform and instrumented with thermocouples to measure the temperatures of the exterior lens surface, the interior lens surface, inside the facepiece, on the headform, and in the airway of the headform during exposure. Heat flux to the headform was also measured during the exposures. Airflow through the mouth and respiratory system was simulated using a breathing apparatus, with the air to the mask supplied by an SCBA, at an average flow rate of 40 L/min at 24 breaths/min. The pressure inside the facepiece was measured during the experiments. During the experiments, the facepiece lenses sustained various degrees of thermal damage, ranging from no visible damage to the formation of crazing, bubbles, holes, and protuberant deformations. The maximum temperatures measured on the exterior of the lenses were approximately 290 °C, while the maximum airway temperatures were approximately 55 °C. An incident radiant heat flux of 15 kW/m 2 was selected as representative of fire fighter exposure and as a useful test criterion for evaluating the performance of the SCBA facepiece lenses. Measurement of internal facepiece pressure was found to be a valuable method for determining the effect of holes on firefighter air supply duration and breathing protection. All of the SCBA facepieces tested exhibited holes in the lens in less than 5 min of exposure to 15 kW/m 2 of incident heat flux. Although much was learned about conditions associated with thermal degradation of SCBA facepiece lenses, more research and development are needed to understand the thermal degradation of facepiece lenses and to develop equipment that better resists the radiant heat fluxes encountered by the fire service during structure fires. These experiments were conducted with support in part by the

Multiple thermal protection techniques, including thermal barrier coatings (TBCs), internal cooling and external cooling, are employed for gas turbine components to reduce metal temperatures and extend component life. Understanding the interaction of these cooling methods, in particular, provides valuable information for the design stage. The current study builds upon a conjugate heat transfer model of a blade endwall to examine the impact of a TBC on the cooling performance. The experimental data with and without TBC are compared to results from conjugate computational fluid dynamics (CFD) simulations. The cases considered include internal impingement jet cooling and film cooling at different blowing ratios with and without a TBC. Experimental and computational results indicate the TBC has a profound effect, reducing scaled wall temperatures for all cases. The TBC effect is shown to be more significant than the effect of increasing blowing ratio. The computational results, which agree fairly well to the experimental results, are used to explain why the improvement with TBC increases with blowing ratio. Additionally, the computational results reveal significant temperature gradients within the endwall, and information on the flow behavior within the impingement channel.

Advancements in cooling for applications such as gas turbines components require improved understanding of the complex heat transfer mechanisms and the interactions between those mechanisms. Critical cooling applications often rely on multiple thermal protection techniques, including internal cooling and external film cooling in gas turbine airfoils, to efficiently cool components and limit the use of coolant. Most research to quantify the effectiveness of such cooling technologies for gas turbine applications has isolated internal and external cooling in separate experiments. The research presented in this paper uses a conjugate heat transfer approach to account for the combined effects of both internal and external cooling. The geometry used for this study is a turbine blade endwall that includes impingement and film cooling as well as the relevant conduction through the endwall. Appropriate geometric and flow parameters were scaled to ensure engine relevant dimensionless temperatures were obtained. Using the conjugate heat transfer approach, the effect of varying the height of the impingement channel was examined using spatially resolved external wall temperatures obtained from both experiments and simulations. A one-dimensional heat transfer analysis was used to derive the average internal heat transfer coefficients from the experimental results. Both experiments and simulations showed good agreement between area averaged cooling effectiveness and impingement heat transfer coefficients. The cooling effectiveness and heat transfer coefficients peaked for an impingement channel height of around three impingement hole diameters. However, the heat transfer coefficients were more sensitive than the overall effectiveness to the changes in height of the impingement channel.