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This research work describes the experimental and numerical investigation of flow behaviour in effusively cooled, porous combustion chamber walls for use in rocket propulsion. The primary goal of the investigation is to develop methods for determining the properties of wall materials, with which the momentum and mass transport at the wall inner surface can be modelled macroscopically using existing laws from the theory of porous media (TPM). Based on these models, the flow of cooling fluid inside the porous chamber walls can be simulated using Navier-Stokes flow solvers, for example those implemented in commercial CFD software. The flow solver FLOTRAN, integrated in the software package ANSYS, was used in the current work to numerically investigate the behaviour of isothermal flows through material samples. The investigated material samples consist of carbon fibre-reinforced carbon (C/C). Orthotropic material behaviour was determined for the momentum and mass transport properties of the C/C material, considering the variation in material properties depending on the sample orientation (parallel or orthogonal flow). To characterise the influence of the cooling fluid on the momentum and mass transport properties, two different flow media (nitrogen, hydrogen) and diffusion media (pentane, diethyl ether) were tested. As a further measure of the influence on momentum transport, the relationship between the permeability coefficient of the C/C material and fluid pressure for isothermal flow through the material sample was investigated experimentally. The variation of pressure served to validate the Forchheimer model for momentum transport in effusion cooled, porous combustion chamber walls over a large range of pressure and therefore density values, which was the second goal of the current work. In this document, simplified expressions for both the mean hydraulic pore diameter and the convective heat transfer surface between the porous combustion chamber wall material and the coolant flow will be derived analytically. These properties of the C/C material will also be quantified based on the gathered experimental data for momentum and mass transport. |
