Research on Arc Heating Engine in Vacuum System

Research on Arc Heated Engine in Vacuum System 1 Dang Daoyuan, Zhao Wenhua, Shi Yong (Department of Engineering Mechanics, Tsinghua University, Beijing, 100084) Anode and cathode) Made of high temperature resistant tungsten metal. The restraint section stabilizes the arc at the midline of the passage and avoids severe ablation of the throat.

After the gas (propellant) enters the channel, it can be heated to a very high temperature by the arc. After expansion, it is ejected at high speed to form a thrust force. A part of the propellant is ionized into a plasma by the high temperature of the center arc to maintain the center arc.

1:200- to 06; Revised date: 200-0-08 2, where the engine, stand, and thrust measurement scale are placed in a vacuum chamber.

The vacuum system consists of a vacuum tank and a vacuum unit. The vacuum tank size is 50.8m1m. The vacuum pumping unit is composed of a Roots pump (150L/s) and a mechanical pump (15L/s). The mechanical pump can keep the vacuum degree of the vacuum chamber within 1000Pa, and the Roots pump can make the vacuum level the lowest. When the engine is working in a vacuum chamber, the vacuum degree of the vacuum chamber is maintained at about 10Pa.

Current 0~50A high frequency arc power supply. The working process of the power supply is divided into two steps: First, the arc ignition system of the power supply ignites the arc. During this process, the power supply generates high-frequency oscillating current. Therefore, it is necessary to pay attention to the protection of the circuit. After the arc is successfully generated, the power supply will supply DC power to stabilize the engine. .

Propellant supply systems include gas cylinders, pressure relief valves, digital gas mass flow meters, and piping, of which the most critical is a gas mass flow meter. Flowmeter with signal feedback system Even in the case of pressure changes in the pipeline, the controller can still control the supply of the set mass flow to ensure the stability of the flow, the flowmeter reading unit is L/min, using argon as the In the case of a working gas, the mass flow rate is equal to 0.042 g/s multiplied by the volumetric flow rate.

Parameters measured by the parametric measuring device include volumetric flow of working gas, current during engine operation, voltage, arc chamber pressure, vacuum chamber pressure, and thrust. The most critical of these is the measurement of the thrust of the engine. In the case where the expansion ratio of the nozzle is 400, the lower nut is used to fasten the arc chamber and the area where leakage easily occurs. The sealing material is still a flexible graphite mat.

The cathode uses a metal tungsten rod with a diameter of 3 mm and uses a gas having oxidizing properties as a working fluid. The upper part of the king is required to play a gas sealing role. The interior is equipped with pyrophyllite (high temperature resistant insulation material, produced in Beijing Mentougou) with a flexible graphite seal. It is mainly used for the sealing and insulation of shells and cathodes. The nut is mainly used for fastening and the material is stainless steel.

Engine shape experimental results and analysis of different impulses with different power ratio change with mass flow Cooling (no arc) specific impulse with mass flow change Flow rate 21mg/s power 100W at various ambient pressures Specific impulse test Arc chamber pressure is about 202kPa Under different power conditions, to ensure stable operation of the engine, it must be ensured that the volumetric flow rate is greater than a certain value. For different arc power conditions, the relationship between specific impulse and volumetric flow rate changes, from which it can be seen that the increase of arc power can increase the specific impulse. Under the same power condition, the specific impulse decreases with the increase of mass flow, because the unit Because of the reduced energy carried by the quality of the propellant, when designing the engine, it is necessary to select a certain working arc power, improve the efficiency of the engine, and adopt certain insulation measures to avoid unnecessary heat loss. It is not difficult to see from the comparison with and without, when there is no arc effect, the specific impulse of pure argon is about 1/2 that when there is an arc effect, and the specific impulse is slightly reduced with the increase of the mass flow rate when the arc is not added. In short, the factors affecting engine specific impulse are arc power, arc chamber pressure, working fluid properties, design optimization, adiabatic measures and environmental pressure (see below).

5. Conclusions The arc heating engine that can work stably under different ambient pressures has been designed through theoretical calculations and experiments; the relationship between engine specific impulse and various parameters has been measured under different arc power conditions; a certain degree of thermal insulation has been adopted while optimizing engine design. Measures increase the odds.

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