Computational Model for Electrode Erosion by High-Pressure Moving Arcs

ABSTRACT: The goal of this project is to develop theoretical models for electrode erosion in high-pressure arcs and incorporate them into computational tools for simulations of arc heaters. The complexity of the electrode material removal process is associated with the multi-phase nature of the arc-electrode interactions, melting and vaporization of the electrodes near the arc foot. Available models can predict material removal rates within an order of magnitude, but have many adjustable parameters that are poorly understood. Our goal is to advance the electrode erosion models, and combine them with state-of-the-art codes for simulation of arc discharges. A comprehensive computational tool will be developed to simulate the arc motion by external magnetic fields, gas-plasma interactions in the arc attachment region, the formation of cathode and anode spots, the melting and vaporization of the electrode surface, material removal due to vaporization, surface shear, chemical reactions, and magnetic forces. In Phase I, we will evaluate erosion models and existing codes developed at CFDRC, develop architecture of the new computational tool, and design an experimental apparatus for testing and validation of the models. In Phase II, the new computational tool will be fully developed and validated versus experiments conducted by the Drexel Plasma Institute. BENEFIT: Arc heaters provide the high-temperature airflows needed for simulating extreme conditions for space vehicles and hypersonic weapon systems. The U.S. Army, U.S. Air Force, U.S. Navy, and NASA use ground-test facilities to develop thermal protection systems for hypersonic flight vehicles and launch vehicles. This tool will help to improve the arc heaters in these specialized facilities by predicting optimal operating conditions with minimal electrode erosion. For industrial applications of arc heaters, electric switches, circuit breakers, etc. this project will help better understand the electrode erosion process and increase the usable lifetime of the devices. For other technologies such as gas-metal cutting and welding, this project can offer improved capabilities for simulating multi-phase processes involving gas, plasma, solid and liquid interactions in a space of a few millimeters, which have proven difficult to measure and control experimentally.