Homogeneous and heterogeneous reaction rates data pertaining to a catalytically stabilized combustion system with a heat-recirculating structure
Description
The homogeneous and heterogeneous reaction rates data are obtained by performing computational fluid dynamics simulations. A mesh independence test is performed to assure independence of the solution to the problem. Velocity inlet boundary conditions are used to define the velocity properties of the flow at the inlet boundary of the fluid region. All the solid surfaces are assumed to be gray and diffuse. The surface-to-surface radiation model is used to account for the radiation exchange in an enclosure of the gray-diffuse surfaces. The radiation model is computationally expensive. The porous media model incorporates independently heat source and momentum resistance terms. The standard energy transport equation is solved in the porous media region with a modification to the heat conduction flux only. A uniform velocity profile is specified at the flow inlet. The temperature of the mixture is prespecified at the flow inlet. The complex physicochemical processes involved in the system can require extensive computing resources. The computational fluid dynamics calculations may take days in order to arrive at a reasonably accurate solution, using fine grids of the system, due to the time-consuming nature of the model. The mathematical formalism developed to describe transport phenomena and chemical kinetics is implemented into ANSYS FLUENT. The computer code and its usage are fully documented. More specifically, ANSYS FLUENT is applied to define the terms in the equations relating to conservation, thermodynamics, chemical production rates, and equation of state, and then combine the results to define the problem involving surface chemistry. To describe the surface reaction mechanisms in symbolic form, the following information is required, including the thermochemical properties of surface species in the surface phases, names of the surface species, site densities, names of all surface phases, Arrhenius rate coefficients, reaction descriptions, and any optional coverage parameters. Natural parameter continuation is performed by moving from one stationary solution to another. A critical point is denoted as the solution to the problem when a turning point is reached. Knowledge of critical parameters of flow velocity and heat loss coefficient gains a fundamental understanding of the essential factors affecting the stability of the combustion process. The critical parameters are useful as the design guides associated with the system. Contributor: Junjie Chen, E-mail address: koncjj@gmail.com, ORCID: 0000-0002-5022-6863, Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China
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Steps to reproduce
The governing equations are discretized in space, and the second-order upwind discretization scheme is used. The under-relaxation factors are reduced for all variables. The residuals decrease by at least six orders of magnitude. Overall heat and mass balances are achieved and the net imbalance is less than one percent of smallest flux through the domain boundaries. The solution converges when the residuals reach the specified tolerance and overall property conservation is satisfied.