Fluid dynamics and intrinsic flow properties of effusion cooled CMC structures in liquid rocket engines

Kurzfassung

The state-of-the-art of coolant flow modelling for effusion cooled CMC thrust chamber liners in liquid rocket engines is briefly reviewed. CFD studies of the effusion cooling process clearly show that common models for flow through porous media are not able to precisely predict the local coolant mass flow rates emerging from the hot gas side wall surface along an effusion cooled liner. In order to adapt existing CFD tools for the modelling of the compressible coolant flow through porous CMC micro structures, their anisotropic flow and heat transfer properties (permeability, area porosity, tortuosity, mean hydraulic pore diameter, thermal conductivity, convective heat transfer coefficient, inner pore surface) must be entered in the software. In this study several test series with various diffusion fluids and material samples have been conducted in order to determine the tortuosity of C/C material by means of the diffusion theory in porous media. The diffusion of the fluids in the C/C material has been investigated in two configurations, i.e. with the fibre orientation perpendicular and parallel relative to the vector of the 1D diffusive flow. The experimental setup for the diffusive flow measurement and some exemplary results are presented. The tests showed that the tortuosity is independent of the fluid media but is strongly dependent of the inclination angle between the fibre orientation and the flow direction.