Advances in Effusive Cooling Techniques of Gas Turbines

Gas turbine combustion chambers and turbine blades require better cooling techniques to cope with the increase in operating temperatures with each new engine model. Current gas turbine inlet temperatures are approaching 2000 K. Transpiration-cooled components have proved an effective way to achieve high temperatures and erosion resistance for gas turbines operating in aggressive environments, though there is a shortage of durable and proven technical solutions. Effusion cooling, on the other hand, is a relatively simple and more reliable technique offering a continuous coverage of cooling air over the component's hot surfaces. This paper presents a numerical model suitable to design the geometric features of effusive cooling systems of gas turbine hot components, and to evaluate their thermo-fluid-dynamic characteristics. The model has been developed specifically with the aim to show the potential advantages deriving from the adoption of the new Poroform® technology. According to this technology the design of the distributions of the diameter and density of holes on the cooled surface allows complete freedom for the thermo-mechanical optimization of the cooled component, with a view to reducing the metal's working temperature and achieving isothermal conditions for large blade areas. In this paper the diameter, density and spacing of the holes, the adiabatic film efficiency and the coolant air consumption of a first stage gas turbine effusion cooled blade are extensively discussed to highlight the system cooling capacity. The results of two cooling solutions for a first-stage gas turbine blade are presented, i.e. the thermo-fluid-dynamic optimized design and one possible manufacturing-oriented optimized design of the cooled component