Thermo-Electric Emission for Plasma Processes
Just as in an arc welder, a high-current electric arc is struck between the anode and cathode. As the cathode heats up, it emits electrons, which collide with and ionize a propellant gas to create plasma in MPD thruster. For gases, there are many circumstances where the electron temperature Te differs from the heavy particle ( ions and neutral atoms) temperature Th. The electrical conductivity and other coefficients in the equations of motion depend on Te. It's therefore necessary in such circumstances to include Te among the variables which define the state of gas, and to employ an additional equation which governs the behavior of the electron temperature. The ZARMmpdMultiRegionFoam is a solver inherited from the Built-in heat transfer solver ChtMultiregionFoam in open source CFD Software OpenFoam, which will take the temperature deviation from LTE (Local Temperature Equilibrium) into account. Through this solver we can get the numerical results of electron number density and electric potential distribution along the electrode-plasma space and in turn the electron emission rate from the cathode to the present plasma flow is determined.