Abstract. The SPT-100 thruster plume was simulated using two different methods: the combined particlein-cell technique with direct simulation Monte Carlo method and the particle-in-cell with the addition of Monte Carlo collisions method. The former method offers a more detailed description of the plume, taking into account the effect of ion-neutral collisions on neutral flow. This effect is ignored in the second method, but this method has much lower computational cost. To analyze the influence of uncertainties in plasma parameters at the thruster exit plane, the computations with different boundary conditions were performed. It is shown that the difference in results obtained by the two methods is significantly smaller than that caused by the uncertainty in flow parameters at the thruster exit plane.
The RF plasma thruster has considerable potential to ease the impact of severe constraints on power, mass, volume and lifetime of microsatellite propulsion systems. This concept is classified as an electrothermal propulsion system and exploits RF capacitively coupled discharge (RFCCD) for heating of a propellant. The plasma is characterized as a low-power discharge possessing a low-current density with high uniformity and propagating through low-pressure gas. To assess computationally the thruster's propulsive capabilities as a function of mass flow rate, electrode separation, RF frequency and power input, a numerical model comprises particle-in-cell/Monte Carlo (PIC/MCC) and Direct Simulation Monte Carlo (DSMC) algorithms. Thruster performance is investigated by permuting electrode geometry (0.5 -2 cm), chamber pressure (0.05 -50 Torr), applied voltage (100 -500 V), and frequency (10 -1000 MHz). For this parameter space, PIC/MCC determines overall trends in plasma characteristics. One selected case (3 Torr, 500 V, 200 MHz) and its set of conditions (plasma density, plasma heating, gas temperature, etc.) form the basis for an in-depth flow field and thrust performance analysis with DSMC. Assuming adiabatic wall conditions, the RF plasma thruster achieves a specific impulse of 104.4 s with Argon at the throat Reynolds number of 25. The RF heating increases the specific impulse by 125 %. This study shows that propulsive capability of the RF plasma thruster can be enhanced by increasing the discharge chamber length, redesigning the nozzle contour, and using propellants with lower molecular weights.
It is shown that at present an acceptable way of reducing the concentration of harmful substances in the surface layer of the atmosphere at rheostat tests of locomotives is their dispersion in a large volume of air. Channels, installed above an exhaust pipe of diesel locomotive with a break at the gas flow, work as ejectors. We have solved jointly the equation of aerodynamic characteristics of the ejector device and the equation of diffusion of gases; as a result the calculated dependence for determining the necessary height of ejector device has been obtained.
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