Publicado 6 números por año
ISSN Imprimir: 2150-766X
ISSN En Línea: 2150-7678
Indexed in
AEROTHERMOCHEMICAL MODEL FOR THE INTERIOR BALLISTICS OF SOLID PROPELLANT ROCKET MOTORS
SINOPSIS
A one-dimensional model is formulated to simulate the interior ballistics of a solid propellent rocket motor, considering the mass, momentum and energy conservation equations, applied to a control volume. The model describes the transient ignition process, flame spreading and complete grain burning. The suitable selection of the numerical method allows an efficient solution, resulting in a very low computational cost that permits the use of a personal computer.
Three steps are considered for modeling the ignition transient: induction, flame spreading and combustion chamber filling. The igniter is modeled by an assumed mass flow rate function, with time as the independent variable. For flame spreading calculation, the conservation equations are combined with a heat transfer model, which considers convection from the igniter gases and conduction through the propellant grain. In this way, the grain surface temperature evolution is calculated using a one-dimensional solution to the transient heat conduction equation. Flame spreading is evaluated using a critical temperature of the grain surface: each element of grain surface is assumed to start burning when its calculated temperature reaches the critical value.
An outstanding feature of this model is the changing boundary conditions downstream of the nozzle. Initially, at the start of the ignition process, the zero-flow boundary conditions are set, simulating the nozzle plug. Later, when the plug expulsion pressure is achieved, the boundary conditions change to subsonic outflow. Finally, when the critical pressure is reached in the combustion chamber, boundary conditions turn into supersonic flow. Instability associated with the initial low Mach number flow is solved using an artificial diffusion term. Also included is the blowing effect of the gases generated on the propellant surface on the friction coefficient, and burning rate correlation considering erosive burning.