Numerical Prediction of the Electric Field Produced Within Launch Vehicle Plumes

Abstract

A novel Eulerian-Lagrangian numerical scheme is developed to characterize the electric nature of rocket plumes. An Eulerian flow solver (Wind-US) is used to simulate the ionized, chemical non-equilibrium, turbulent plume produced by a methane-oxygen rocket engine, including a detailed chemi-ion reaction set (34-species, 178-reactions).A one-way Lagrangian solver is described for simulation of soot effects on the electrical nature of the plume using the Eulerian flow solution, and addresses ion emission from soot, and soot-ion attachment. The numerical scheme is demonstrated for a hypothetical 15000-lbf thrust rocket methane-oxygen engine. The sensitivity of the electric nature of the plume is evaluated for a stoichiomtetric and fuel-rich mixture. Results from initial demonstrations of this scheme suggest that substantial ion fields are generated witin the plumes, and that soot particles capture the free electrons to form a region of negatively charged particles which likely persist for hundreds of nozzle exit diameters downstream. Nomenclature C D= drag coefficient m = mass of soot particle r = radial distance from centerline S = surface area of soot particle u rel = relative velocity -gas velocity minus soot particle velocity ∆t = time step x = axial distance from nozzle throat φ = equivalence ratio (also ER) ρ = density of gas