High Temperature Oxidation of Platinum Alloys in the Presence of Monomethylhydrazine, Dinitrogen Tetroxide and their Reaction Products

摘要

The aim of this study was to investigate the behaviour of platinum rhodium alloys exposed to liquid rocket propellants, as Monomethylhydrazine (MMH), Dinitrogen Tetroxide (N2O4), and their reaction products. To analyse the chemical composition of the combustion products over a thrust chamber cross section a simulation with Rocflam-II was performed. Additional, light microscopy and scanning electron microscopy (SEM) were used to investigate the surface morphology of the deposited and non-volatile combustion reaction products (soot and salts) and their interaction with the platinum surface. The results show, that NO_2, H_2O, CO_2, CO, HCN, N_2, H_2, H_2O, CH4 and OH are the main combustion reaction products of the hypergolic reaction of MMH and N2O4. The simulation with Rocflam-II can underline the distribution of the combustion reaction products over a thrust chamber cross section. Furthermore, the microscopic investigations represent the combustion characteristics, which have a circular shape, were linked to the injection pattern and the liquid fuel film cooling widely used in bipropellant rocket engines, to keep the upper combustion chamber and injection head at lower and optimum working temperatures. The performed investigations feature no significant attack of the platinum rhodium surface by high temperature oxidation. This could be attributed to the fact, that the representative exposure period and temperature of the investigated samples were too low to show significant oxidation effects.