DESIGN AND OPTIMIZATION OF THE INTERNAL COOLING CHANNELS OF A HP TURBINE BLADE - PART I, METHODOLOGY

This first paper describes the Conjugate Heat Transfer (CHT) method and its application to the performance and life-time prediction of a high pressure turbine blade operating at a very high inlet temperature. It is the analysis tool for the aerothermal optimization described in a second paper. The CHT method uses three separate solvers: a Navier-Stokes (NS) solver to predict the non-adiabatic external flow and heat flux, a Finite Element Analysis (FEA) to compute the heat conduction and stress within the solid, and a ID aero-thermal model based on friction and heat transfer correlations,for smooth and rib-roughened cooling channels. Special attention is given to the boundary conditions linking these solvers and to the stability of the complete CHT calculation procedure. The Larson-Miller parameter model is used to determine the creep-to-rupture failure lifetime of the blade. This model requires both the temperature and thermal stress inside the blade, calculated by the CHT and FEA. The CHT method is validated on two test cases: a gas turbine rotor blade without cooling and one with 5 cooling channels evenly distributed along the camber line, The metal temperature and thermal stress distribution in both blades are presented and the impact of the cooling channel geometry on lifetime is discussed.