Aerothermal characterization of finned surfaces in high-speed flows

Abstract

Surface Air Cooled Oil Coolers are finned heat exchangers installed in the bypass duct of a turbofan engine that act as an additional cooling source for the engine components, having transonic flow as a heat sink. Characterizing the heat transfer and the aerodynamics of finned surface designs is essential to understanding their impact on overall engine efficiency. In the present study, different models are assessed numerically and experimentally. Two geometries are tested in a high-speed linear wind tunnel where measurements are taken using several sensors and optical techniques. An Inverse Heat Conduction Methodology based on a Levenberg-Marquardt Algorithm is developed to retrieve the heat flux on the fin’s surfaces accurately. A numerical analysis is performed using Reynolds Averaged Navier-Stokes simulations, and the results are compared against the experimental findings. A good agreement is observed between the datasets supporting the accuracy of the numerical methodology. Finally, a multi-objective optimization algorithm is coupled with the solver to explore new geometries that maximize the heat transfer while minimizing the pressure drop across the studied domain. Over 400 profiles were generated and numerically analyzed, allowing for identifying the features that have a more decisive influence on the performance of the fins. Profiles that present improvements of up to 19% are selected and analyzed in further detail. A combined improvement of 7.5% heat transfer enhancement and 9.1% reduction in pressure losses is achieved while maintaining a constant mass flow.