This paper presents a novel optimisation methodology based on both Adjoint sensitivity analysis and trust-based dynamic response surface modelling to improve performance of a modern turbine of a large civil aero-engine in the presence of high-fidelity geometry configurations. The system has been applied to the non-axisymmetric hub and tip endwall optimisation of a high-pressure turbine stage making use of multi-row 3D simulations, parametric modelling and rapid meshing of real geometry features such as rim seals and modelling of film cooling flows.
It has been shown in previous papers that improvements gained using simplified models of the stage are lost when applying the high-fidelity geometry configuration. New results presented in this paper indicate that controlling the purge flow that exits the disc space through the rim seal at the hub of the main annulus is more significant than the reduction of secondary flows in the main passage. For a given rim sealing mass flow rate and whirl velocity, the non-axisymmetric endwalls are optimised such that the detrimental impact of the sealing flow on the turbine performance is reduced, and hence the stage efficiency is significantly increased. The traditional optimisation approaches based on evolutionary methods or even sequential modifications for defining the endwalls shape are computationally demanding. Since, turbomachinery industry continuously strive to reduce the design cycle time, in particular when high fidelity 3D CFD is used, the main body of this paper outlines the novel methods developed to produce a practical design in a very aggressively short design cycle time.