3温度モデルを用いた水素MPDスラスタの電磁流体解析

Abstract

Plasma flowfields and performances of an MPD thruster (MY-II thruster), which uses hydrogen as a propellant, are studied by solving axi-symmetrical two-dimensional magnetoplasmadynamic equations. The three-temperature model including the translation Ttr, vibration Tvib, and electron Te temperatures is incorporated into the flow solver. When the mass flow rate (m) is 1.37g/s, there is reasonable agreement on the thrust with measured data, especially at a discharge current (Jdis) of 7, 8kA. Under the conditions of m = 0.4g/s and Jdis = 5kA, the calculated thrust, specific impulse and thrust efficiency are 7.50N, 1,911s and 21.3% (without considering sheath voltage drop), respectively. The calculated flow shows a temperature nonequilibrium state (Te = 2.53eV, Tvib = 1.32eV, Ttr = 0.60eV) at the edge of the straight part, and it is found that the relaxation time between the vibration and the electron energy is equal to the characteristic time of the flow at (z, r) = (30mm, 20mm). Along the symmetrical axis, the dissociation and ionization fractions reach 1.0 (fully dissociation) and 0.2, respectively. Because the discharge current path by the three-temperature model can explain the important feature of hydrogen MPD (current expansion to the downstream), it is concluded that the three-temperature model can reproduce the experimental results.