A first step into the blanching modelling of Liquid Rocket Engines: taking into account the roughness increase of the chamber wall

Kurzfassung

Whereas pure oxidation of a copper based liquid rocket combustion chamber wall results (due to the brown color of copper oxide) in a darkening of the hot-gas side of this chamber wall, blanching (on the contrary) leads to a lighter color. This is a result of a cyclic oxidation and reduction of the chamber wall material. The most important influence of blanching is the roughness increase of the chamber wall. The strong effect of this roughness increase is exemplarily considered for the main combustion chamber of a 10 MPa chamber pressure, 1 MN vacuum thrust reference engine. A thermally fully coupled CFD analysis of the hot-gas flow and thermal FE analysis of the heat conduction in the chamber wall and CFD analysis of the coolant flow is applied to a chamber wall model of this reference engine. By running this analysis for both: initial (small) roughness as well as blanching-caused (strongly increased) roughness, the severe thermal influence of blanching can be assessed. Finally, the blanching-caused decrease of the fatigue life of the chamber wall of the reference engine is shown.