A Low Order Mass Flow-Heat Transfer-Stress Model as a Design Code for Transpiration Cooled Nickel Gas Turbine Blades and a Guide for Crystal Plasticity-Based Fatigue-Creep Life Assessment

Transpiration Cooling (TC) systems offer the opportunity to significantly improve the fuel efficiency of jet engines by allowing them to run much hotter than current designs allow. The enhanced heat transfer provided by TC systems requires the adoption of new radical design concepts, but large cyclic thermomechanical stresses and creep-plastic deformation generated during operation can severely limit the life of a component. TC systems can only be realised in real engines if an integrated design approach is adopted, which simultaneously considers the aerothermal and mechanical performance. We develop here a multidisciplinary low order aerothermal-stress model (LOM) which addresses this need by combining first order coolant mass flow and fluid-solid convective-conductive heat transfer calculations with thermomechanical stress calculations in the solid. The LOM provides rapid answers to crucial questions posed during conceptual and preliminary design stages, such as: how much cooling air and how many cooling holes are required in gas turbine blades for them to operate safely at a given turbine inlet (hot gas) temperature? Simultaneously, the LOM narrows the range of conditions under which Crystal Plasticity Finite Element (CPFE) simulations may be required for fatigue-creep life assessment at the detailed design stage. Our answer to previous pessimistic views on the practical use of TC is that TC systems can actually work thanks to the threefold benefit of cooling holes in reducing metal temperatures, temperature gradients and effective thermal stresses. CPFE simulations confirm this new conclusion, encouraging the wider use of our methods in the design of turbomachines and hypersonic technologies as well as the take-up of TC systems to deliver fuel efficient and durable turbines for net zero.