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A Computationally Efficient Model for the Simulation of Catalytic Monolith Reactors with Detailed Chemistry

Nair, Nikhil
http://rave.ohiolink.edu/etdc/view?acc_num=osu1374005338

Abstract Details

2013, Master of Science, Ohio State University, Mechanical Engineering.
A catalytic monolith reactor can be modeled using direct numerical simulation, where all the length scales within a monolith reactor are resolved. This, however, requires the use of a fine grid with millions of cells, which makes it computationally prohibitive. The objective of this thesis is to develop a reduced model for modeling a full-scale catalytic monolith reactor. This model is a computationally inexpensive way of simulating the reacting flow within the entire reactor including the monolith, the pre-monolith and post-monolith regions. The modeling approach developed in this study, termed as sub-grid scale modeling, utilizes a grid that resolves only the largest length scales, while the physics in the smallest (channel or pore) scales are modeled using scale-averaged models, thereby making this approach a computationally efficient alternative to direct numerical simulation. The thesis begins with the development and validation of a turbulence model to simulate turbulent flow in the open regions of the converter. This is followed by the development, verification and validation of a porous media model for flow, heat and mass transfer, since in sub-grid scale modeling framework the monolith reduces to an anisotropic porous medium. A scale-averaged model for simulating the surface chemistry is also incorporated into the porous media model. Finally, all the sub-models are integrated to create a unified model that can simulate the reacting flow through a catalytic monolith reactor. After verifying and validating the individual sub-models, two full-scale validation studies are undertaken. The first validation study involves the catalytic combustion of a premixed hydrogen-air mixture flowing through a monolith containing platinum catalyst. A 12-step reaction mechanism with 4 gas-phase species and 5 surface adsorbed species is used for this study. The second validation study involves the catalytic conversion of a mixture of unburnt hydrocarbon, carbon monoxide, nitric oxide and air in a platinum-rhodium three-way catalytic converter. In this case, a 61-step reaction mechanism with 31 species was used. In both studies, only steady state operation is simulated. The simulation results in both the validation studies are in reasonable agreement with experimental data given the numerous uncertainties in boundary conditions and the underlying chemistry. Key contributions of this thesis includes extending a CFD code that could simulate laminar flow and surface chemistry to a model that can simulate laminar or turbulent transport of mass, momentum, energy and species, as well as simulate transport and surface chemistry in an anisotropic porous medium, developing a special numerical treatment of the mass and momentum transport equations to account for the porous-fluid interface and integrating the turbulence model and porous media model into a single simulation tool for simulation of full-scale catalytic monolith reactor.
Sandip Mazumder, Prof. (Advisor)
Ahmet Selamet, Prof. (Committee Member)
160 p.
Mechanical Engineering
CFD,computational fluid mechanics,catalytic monolith reactor,anisotropy,porous medium,porous interface,surface chemistry,sub-grid scale model

Recommended Citations

Citations

  • Nair, N. (2013). A Computationally Efficient Model for the Simulation of Catalytic Monolith Reactors with Detailed Chemistry [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1374005338

    APA Style (7th edition)

  • Nair, Nikhil. A Computationally Efficient Model for the Simulation of Catalytic Monolith Reactors with Detailed Chemistry. 2013. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1374005338.

    MLA Style (8th edition)

  • Nair, Nikhil. "A Computationally Efficient Model for the Simulation of Catalytic Monolith Reactors with Detailed Chemistry." Master's thesis, Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1374005338

    Chicago Manual of Style (17th edition)

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