The analysis of heat transfer in engine cavities or blade internal cooling systems is one of the most challenging work for aircraft engines designers for two main reasons. Firstly, the efficiency of such systems has a direct influence on both life and performance of these engines. Secondly, the available tools to predict heat transfer in both solid parts and surrounding cooling gases, i.e. Navier Stokes and conduction codes, are often used independently. An interaction model between the fluid and solid media is generally required and remains a difficult issue in engine configurations. A coupling procedure between a Navier-Stokes code and a conduction solver is therefore the only way to achieve heat transfer predictions in all flow situations. The objective of this work is to present such a procedure, which has been developed at Snecma and based on a Finite Volume Navier-Stokes code and a commercial Finite Element solver.
The first application showed in the paper demontrates, with an uncoupled calculation that the Navier-Stokes code MSD, from ONERA, is able to predict heat transfer with an acceptable accuracy. The discretization used in the solid to predict heat conduction is briefly presented. Then the steady state coupling procedure is exposed and validated with an analytical solution. Finally, a conjugate heat transfer computation in a rotor/rotor cavity of a real engine, with rotating solid disks, is described in detail.
A combined experimental and numerical study has been conducted in order to investigate the turbulent flow in a heated rotor-stator cavity of low gap ratio, subjected to a superposed centripetal flow. In the scope of this work, the fluid can be considered as incompressible, with the consequence that the heat transfer process is dissociated from the dynamical effects. The flowfield is characterized by two separated Ekman layers and a core region.
Detailed velocity measurements have been carried out. Reynolds stresses were examined in great detail using hot wire measurements, whereas temperature-velocity correlations were obtained using combined hot wire–cold wire measurements. The temperature distribution was specified on the stator and heat fluxes were measured with fluxmeters.
Numerical simulations of the above configuration have been carried out with the following turbulence models: a two equation k-1 model, an Explicit Algebraic Reynolds Stress Model (EARSM), and an anisotropic thermal extension of the k-1 ASM model. The agreement between experimental and numerical results is generally good for the nondimensional velocities, except in the Ekman layer region. A comparison of Reynolds Stresses is also provided. The heat flux on the stator appears to be underestimated, due to the poor prediction of the Ekman layer zone.
The numerical study reveals the critical importance of the inlet conditions, and in particular of the nondimensional tangential velocity on the flow inside the cavity. A comparison with experimental data also confirms that the anisotropy is of importance mainly in the Ekman layer region.
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