Computational study of a MEMS-based catalyzed micro-thruster with homogeneous chemical reaction

Miniaturized satellites have attracted numerous interests due to their increasing demands for space missions. In contrast to traditional satellites, the operations of the nano-scale or even pico-scale satellites require extremely low levels of thrust and precise spatial maneuverings. Micro-electro-mechanical-system (MEMS) technology has demonstrated great potentials in various industrial applications such as automobile, electronics, medicine, and life science fields, etc. and is well-suitable to meet the fabrication requirements of a micro-thruster. Furthermore, the liquid catalyst-based micro-propulsion system which is driven by the catalytic decomposition of the hydrogen peroxide (H₂O₂) with the catalysis of an aqueous ferrous chloride (FeCl₂) solution is proposed under the considerations of the advantages of simplicity, high reliability, fewer external power input, the prevention of aging problem of heterogeneous catalyst, and environmentally friendly nature. However, the experiment of the liquid catalyst-based micro-propulsion system is difficult because the development of the fabrication processes for micro-thruster will take much time, and the problem of the tube connection and the control of the excessively small flow rate are not overcome easily. Thus, the numerical simulation was utilized to study the micro-fhruster in this preliminary investigation. Due to the immaturity of the current numerical study of the heterogeneous chemical reaction, the numerical simulation of the chemical reaction in micro-fhruster is simplified to homogenous chemical reaction. Two 2-D computational models which consist of an injector, reaction chamber and nozzle, as well as are referred as the Ml and M2, respectively, were used in this study. The numerical solutions are based on solving the conservation equations of mass, momentum, energy, and species transport. Simulation results showed that the average temperature, oxygen concentration, and velo- - city of M2 model at outlet were higher than those of Ml. The differences of the parameters described above between Ml and M2 increased as the temperatures of inlets rose. These meant that the hydrogen peroxide consumption in M2 was higher than that in Ml, i.e. the performance of M2 model was better than Mi´s. Besides, the effect of the variation in positions where the ferrous chloride is injected was very small in M2 model. Also the different ratios of mass flow rate of aqueous hydrogen peroxide solution and aqueous ferrous chloride solution were calculated in this study. The results showed that the performance of the mass flow rate ration of 3:1 was the best, 1:1 was middle, and 7:1 was the worst.