A Review on Film Cooling Research: Historical Developments in Hole Shapes, Measurement Techniques, Effects of Operating Conditions, and Impact of Additive Manufacturing

Abstract Film cooling is a widely adopted technology in high pressure stages of gas turbines in both propulsion and power-generation areas to keep the turbine components in the safe operation range. This cooling concept was first introduced by Prof. Goldstein’s group from University of Minnesota in 1970s. Much of the follow up research efforts have been focused on the film hole shapes, measurement techniques, and film cooling performance under various mainstream and coolant side operating conditions. Here, a comprehensive developmental review from mid 2000s is presented to summarize the technical improvements and future path. Due to recent rapid advancements in the areas of measurement techniques (e.g., Pressure sensitive paints) and metal additive manufacturing, the film cooling technology has undergone significant changes. This article provides a historical perspective with over five decades of innovations in the area, and the effects of injection angle, hole shape, density ratio, momentum-flux ratio, blowing ratio, advective capacity ratio, and freestream conditions, etc. The impact of additive manufacturing on the film hole design strategies, current challenges posed by state-of-the-art AM technology, and pathways for future research is then discussed thoroughly. Detailed discussion is provided on the AM print quality in terms of dimensional accuracy, surface roughness and its subsequent effect on the adiabatic film cooling effectiveness and net heat flux reduction. A comparative study is performed with the AM assisted film hole fabrication and conventionally manufactured film holes.