Second Vane Endwall Heat Transfer Reduction by Iceform Contouring

Abstract

Endwall heat transfer within high pressure turbines is important in the quest for higher gas turbine combustion temperatures, improved cycle performance and longer part life. In this paper, the iceformation design method was used to reduce endwall heat transfer by contouring the endwall, altering the secondary flows that produce elevated endwall heat transfer load and obtaining an isothermal endwall geometry. Iceformation is analogous to metal melting regions where a hot fluid alters the isothermal surface shape of a part being maintained by a cooling fluid. The passage flow, heat transfer and geometry evolve together under the constraints of flow and thermal boundary conditions. The iceformation concept is not media dependent and can be used in analogous flows and materials to evolve novel boundary shapes. In the past, this method has been shown to reduce aerodynamic drag and total pressure loss in flows such as diffusers and cylinder/endwall junctures. This paper adds to the iceformation design record by investigating endwall surface heat transfer reduction in an air flow. The second vane endwall heat transfer problem is important as combustion temperatures rise with the demand for higher thrust or work output and with the limited amount of cooling air devoted to components beyond the first stage. A Reynolds number matched geometry reduced the averaged endwall Stanton number by 24% compared to the rotationally symmetric geometry of an Energy Efficiency Engine (E3) second vane endwall. The iceformation method has applications in experimentally or computationally shaping an isothermal endwall geometry prior to detailed design of internal convection and film cooling circuits.