Conjugate heat transfer in high pressure turbines

• Main Author: Maffulli, Roberto
• Other Authors: He, Li
• Published: University of Oxford 2016
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.728952

In the present thesis the link between aerodynamics and heat transfer in high pressure turbines is investigated through steady numerical calculations. The investigations include the effect of wall temperature on the Heat Transfer coefficient (HTC), aiming to understand whether the conventional assumption of HTC being invariant with the thermal boundary condition does hold in a typical compressible flow, where the aerodynamic and thermal fields are strongly coupled. A novel non-linear three point method is proposed to scale wall heat transfer accounting for the dependence of HTC on wall temperature and local flow history. The effect of wall boundary condition on external aerodynamics and heat transfer calls for the need of Conjugate Heat Transfer (CHT) methods as design tools. For this reason CHT capabilities have been developed and integrated in Rolls-Royce Hydra CFD solver. The implemented CHT solver is fully-coupled, allowing for simultaneous solution of the solid and fluid domains. The implemented CHT coupling has been shown to be numerically stable with a good convergence rate for all cases tested. The implemented code has been successfully validated against both experimental, analytical and numerical data. Conjugate analysis of a double-wall trailing edge cooling design has been performed under matched external Biot conditions. Aim of the investigation has been to quantify the effect of CHT on the cooling discharge characteristics and external aerodynamics in a cooling configuration where coolant and external flow are separated by a lower thermal resistance than in a traditional internal cooling configuration. Detailed CHT results for this case are presented and discussed.