Multi-dimensional Numerical Simulation Based On Eddy Dissipation Concept Combustion Model Coupling Reduced Chemical Reaction

With the development of modern industry and building materials, fuels become increasingly complicated. Combustion contains a series of chemical reactions and some physical effects, such as viscosity, thermal conductivity, binary diffusion between components and so on. In fact, combustion is the couple of multicomponent complex chemistry and turbulent flow. With the advancement of technology, computer numerical research has become an important method of fire science. The researches of complex chemical problems have made a great progress for the past few years. In order to describe the process of complex chemical in combustion reasonably and predict the yield of products, the application of complex chemical reaction mechanisms in computer numerical simulation is very necessary. However, the coupled flow and combustion with great stiffness problems bring difficulties to numerical simulation, which is mainly emerged in detailed combustion chemical kinetic mechanisms. It greatly limits the application of CFD methods in the study of complex chemistry. The reduced chemical mechanism simplifies reaction steps and reduces the calculation time under the premise of preserving some important properties of detailed chemical kinetic mechanism. The reduced chemical kinetic mechanisms provide a great contribution to the development of numerical simulation of combustion in modern engineering, and it is an important branch of chemical kinetics.An eddy dissipation concept (EDC) combustion model is added to replace mixture fraction model in fire dynamics simulator (FDS6.0) which is published by US National Institute of Standards and Technology (NIST). Theoretically, EDC model is capable to deal with problems of more complicated chemistry and combustion components. NIST, however, only considers independent elementary reactions and chemical properties of a single component in its limited chemical kinetics database. Almost all the international chemical kinetic mechanisms are given in CHEMKIN format, that is, FDS cannot directly use these results.Reduced chemical mechanisms are integrated into the code of EDC model to achieve the multi-dimensional numerical simulation of turbulent combustion based on chemical kinetic reactions. This simulating platform combines the function of FDS and CHEMKIN, which expands the application range and versatility of FDS with CHEMKIN database. Compared with simple chemical method, the reduced chemical mechanisms provide much richer combustion data. It is helpful to represent the process of chemical reactions realistically and collects some combustion products which are unpredictable for simple chemical reaction. This simulation platform can provide the data basis for hazard evaluation of the combustion products in the fire engineering.Firstly, a four-step reaction mechanism of methane is applied into FDS to verify the effectiveness of dimensional numerical simulation platform. A0.3m diameter methane turbulent diffusion flame is simulated and results show that the simulation method is reliable compared with simple chemical method. Secondly, a full-scale fire case is simulated based on the combine platform and the transport process of pollutant emission is described reasonably. And the toxic potency of combustion products containing nitrides is assessed.