عنوان مقاله [English]
Hydrazine monopropellant thrusters are commonly used in the situation control and orbital transmission systems of satellites and space crafts. In these thrusters, hydrazine is decomposed into a hot gas product after passing through the catalyst bed during an exothermic reaction. The decomposition chamber of a monopropellant thruster is numerically modeled at the pore scale. Then the effect of catalyst bed porosity coefficient, which is the most important parameter affecting the performance of the decomposition chamber, is investigated. Simulations were performed in two-dimensional axial symmetry as the steady flow in the gas phase. Catalyst granules with an average diameter of 1 mm with three porosity coefficients of 0.4, 0.55, and 0.65 have been considered and the inlet pressure of the decomposition chamber has been considered to 15 bar. The results showed that the porosity coefficient has a very significant effect on the performance of the catalyst bed so that by decreasing this coefficient, the decomposition of hydrazine increases, the bed temperature, and outer wall temperature increase, and the mass flow rate decreases. Reducing the bed porosity coefficient from 0.65 to 0.4 causes about a 40% drop in the bed pressure compared to the initial inlet pressure and also about a 40% reduction in the mass flow rate through the bed. Therefore, the study of this parameter can greatly help the researchers in determining and optimizing the efficiency of the decomposition chamber.