Numerical studies on plasma plume flows from a cluster of electric propulsion devices

Several hybrid fluid–particle simulations are performed to investigate the plasma plume flows from a cluster of Hall thrusters. These simulations adopt a detailed fluid electron model to describe electron properties. A general finite element solver is developed to solve for these electron properties, and the cathode geometry, facility effects, and vacuum chamber background pressure are included in the simulations; these are compared with available experimental data, and indicate that the cathode had effects on some flow property distributions. They also clearly display charge exchange collision effects and the clustering effects. There exist complex three-dimensional near field structures in the ion number density with Hall thrusters in operation. With four thrusters in operation, a severe impingement is expected right behind the cluster center. Compared with axisymmetric simulations, these three-dimensional simulations have several improvements. When compared with the Boltzmann relation, the detailed fluid electron model displays superiority in predicting the electron temperature as well.