Numerical simulation of a rocket motor with chemical reaction flow / Simulação numérica do escoamento em um motor foguete com reação química

AUTOR(ES)
DATA DE PUBLICAÇÃO

2000

RESUMO

This work presents a numerical simulation of the flow field in a propellant rocket engine chamber and exit nozzle using techniques to allow the results to be taken as starting points for designing those propulsive systems. This was done using a finite volume method simulating the different flow regimes which usually take place in those systems. As the flow field has regions ranging from the low subsonic to the supersonic regimes, the numerical code used, initially developed for compressible flows only, was modified to work proficiently in the whole velocity range. It is well known that codes have been developed in CFD, for either compressible or incompressible flows, the joint treatment of both together being complex even today, given the small number of references available in the area. Here, an existing code for compressible flow was used; in this were introduced primitive variables in the Transport (Euler) equations, here the pressure, the Cartesian components of the velocity and the temperature instead of the conserved variables. This was done to permit the treatment at any Mach number. Unstructured meshes with adaptive refinement were employed here. The convective terms were treated with first and second order upwind methods. The numerical stability was kept with artificial dissipation and in the time coverage one used a five-stage Runge-Kutta scheme for the Fluid Mechanics and the VODE (Value of Ordinary Differential Equations) scheme along with the Chemkin II in the chemical reacting solution. During the development of this code simulating the flow in a rocket engine, comparison tests were made with several different types of internal and external flows, at different velocities, seeking to establish the confidence level of the techniques being used. These comparisons were done with existing theoretical results and with other codes already validated and well accepted by the CFD community. To simulate internal and external flows with velocity regimes in the range from low subsonic (M = 0.05) to supersonic (M = 4), linearized Euler equations were used. Among the external flows this was done with the flow around a circular cylinder and the one over an aerodynamic wedge, and for the internal flows, the flow in a channel with a downstream decreasing cross section and the converging-diverging nozzle flow were used in the code validation procedure. In the reactive it test was used the parabolic approximation of the bell shaped nozzle and the chemical kinetics model chosen was the one dealing with Hydrogen and Oxygen with the extinction and production of chemical species. The temperature field was found ranging from 1518 K on the onset of the chemical reaction down to 838.4K; this value lower was due to the non-zero velocity conditions in the chamber.

ASSUNTO(S)

tubeira divergente câmaras de combustão finite volume method divergent nozzles backward differencing propulsion and combustion diferenciação numérica gradientes de pressão numerical differentiation pressure gradients thrust chambers diferença atrasada método de volume finito propulsÃo e combustÃo

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