Numerical study of chemically reacting flows with catalytic surface reactions using the pressure correction algorithm

Abstract

This paper describes a numerical method to study a general chemically reacting flow with catalytic surface reactions. Multi-step finite rate chemistry models are employed to model the physics of the reaction process. A split-operator method separates the chemical kinetics terms from the fluid dynamical terms. The changes of species concentrations on a catalytic surface are included as boundary conditions in the species transportation equations. The pressure-velocity correction method in the CFD2000 package is used to enhance numerical stability. Introduction Numerical simulation of chemically reacting flows continues to become an important tool in the design and analysis of modem reactor concepts. Surface chemical reactions occur at a gassolid, gas-liquid or liquid-solid interface. The comprehensive understanding of chemical vapor deposition (CVD) systems, which are used throughout the microelectronics industry today, requires this technology. Despite the importance of CVD, many other chemical reaction devices, such as solid rocket propulsion systems, high efficiency internal combustion engines, high altitude hypersonic vehicles also need this technology. It is well known that the detailed mechanism about surface reaction procedures is very complicated. Numerically, a phenomenological model is required. Chemical reactions are frequently coupled with fluid flows and take place at extremely small time scales. Accordingly, chemically reacting flows are divided into three general types: (1) Equilibrium; (2) Frozen and (3) Finite rate. The first two of these are limiting cases which correspond to instantaneous reactions(equilibriura) and to no reactions(frozen). Copyright © 1998 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Finite rate reactions occur on time scales which allow for numerical modeling, and are those which are observed to occur in most reacting flows. The numerical methods used to simulate the flow physics for these real flows face a major difficulty. The difficulty is the stiffness of the mathematical models which describe the transport characteristics for the species concentrations. For a general reacting flow, the gas phase chemical reactions and surface reactions may exist simultaneously. For surface reaction, especially in CVD systems, the pioneering work of Moffat and Jensen pointed out that the thermal diffusion term sometimes may play an important role in the study of several reactor configurations. However, the method in their work is limited to boundary layer type flows. Currently, this paper reports a new development combining the noniterative pressure correction method with source term splitting technique to simulate general non-equilibrium chemically reacting flows in which gas phase and surface reactions occur simultaneously. Analysis Governing Equations The governing equations compressible flow are as follows: Continuity: Momentum: in tensor form for