عنوان مقاله [English]
Hydrazine monopropellant thrusters are commonly used in the situation control and orbital transmission systems of satellites and space crafts. In this paper, the decomposition chamber of a monopropellant thruster is numerically modeled on the scale of the bed granules. Then the effect of the 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 and catalyst granules with an average diameter of 1 mm with three porosity coefficients of 0.4, 0.55 and 0.65 has been considered and the inlet pressure of the decomposition chamber has been considered 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 the outer wall temperature increase and the mass flow rate decreases. Reducing the bed porosity coefficient from 0.65 to 0.4, causes about 40% drop in the bed pressure compared to the initial inlet pressure and also about 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.