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Journal ArticleDOI

Numerical modeling of catalytic ignition

01 Jan 1996-Vol. 26, Iss: 1, pp 1747-1754
TL;DR: In this paper, a simplified multicomponent model of catalytic ignition of CH4, CO, and H2 oxidation on platinum and palladium at atmospheric pressure is studied numerically and the dependence of the ignition temperature on fuel/oxygen ratio is calculated and compared with experimental results.
Abstract: Catalytic ignition of CH4, CO, and H2 oxidation on platinum and palladium at atmospheric pressure is studied numerically. Two simple configurations are simulated: the stagnation flow field over a catalytically active foil and a chemical reactor with a catalytically active wire inside. The simulation includes detailed reaction mechanisms for the gas phase and for the surface. The gas-phase transport and its coupling to the surface is described using a simplified multicomponent model. The catalyst is characterized by its temperature and its coverage by adsorbed species. The dependence of the ignition temperature on the fuel/oxygen ratio is calculated and compared with experimental results. The ignition temperature of CH4 oxidation decreases with increasing CH4/O2 ratio, whereas the ignition temperature for the oxidation of H2 and CO increases with increasing fuel/oxygen ratio. The kinetic data for adsorption and desorption are found to be critical for the ignition process. They determine the dependence of the ignition temperature on the fuel/oxygen ratio. A sensitivity analysis leads to the rate-determining steps of the surface reaction mechanism. The bistable ignition behavior observed experimentally for lean H2/O2 mixtures on palladium is reproduced numerically. The abrupt transition from a kinetically controlled system before ignition to one controlled by mass transport after ignition is described by the time-dependent codes applied.
Citations
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Journal ArticleDOI
TL;DR: In this article, a review of the development of micro-power generators by focusing more on the advance in fundamental understanding of microscale combustion is presented, and the conventional concepts of combustion limits such as flammability limit, quenching diameter, and flame extinction and heat recirculation are revisited.

621 citations

Journal ArticleDOI
Kaoru Maruta1
01 Jan 2011
TL;DR: A review of research and development on micro and mesoscale combustion is presented in this article, with an emphasis on fundamental understandings achieved in the field during the last decade, due to its small scale nature, increasing effects of flame-wall interaction and molecular diffusion.
Abstract: A review of research and development on micro and mesoscale combustion is presented, with an emphasis on fundamental understandings achieved in the field during the last decade. Due to its small scale nature, increasing effects of flame–wall interaction and molecular diffusion are the characteristic features of micro and mesoscale combustion. After brief review of device developments, overview of fundamentals in micro and mesoscale combustion as well as possible future directions is presented.

361 citations

Journal ArticleDOI
01 Jan 2005
TL;DR: In this paper, a spiral counterflow "Swiss roll" burner was evaluated with and without a bare-metal Pt catalyst and a wide range of Reynolds numbers (Re ) were tested using propane-air mixtures.
Abstract: An experimental study of a spiral counterflow “Swiss roll” burner was conducted, with emphasis on the determination of extinction limits and comparison of results with and without bare-metal Pt catalyst. A wide range of Reynolds numbers ( Re ) were tested using propane–air mixtures. Both lean and rich extinction limits were extended with the catalyst, though rich limits were extended much further. With the catalyst, combustion could be sustained at Re as low as 1.2 with peak temperatures as low as 350 K. A heat transfer parameter characterizing the thermal performance of both gas-phase and catalytic combustion at all Re was identified. At low Re , the “lean” extinction limit was actually rich of stoichiometric, and rich-limit had equivalence ratios exceeded 40 in some cases. No corresponding behavior was observed without the catalyst. Gas-phase combustion, in general, occurred in a “flameless” mode near the burner center. With or without catalyst, for sufficiently robust conditions (high Re , near-stoichiometric) not requiring heat recirculation, a visible flame would propagate out of the center, but this flame could only be re-centered if the catalyst were present. Gas chromatography indicated that at low Re , even in extremely rich mixtures, CO and non-propane hydrocarbons did not form. For higher Re , where both gas-phase and catalytic combustion could occur, catalytic limits were slightly broader but had much lower limit temperatures. At sufficiently high Re , catalytic and gas-phase limits merged. It is concluded that combustion at low Re in heat-recirculating burners greatly benefits from catalytic combustion with the proper choice of mixtures that are different from those preferred for gas-phase combustion. In particular, the importance of providing a reducing environment for the catalyst to enhance O 2 desorption, especially at low Re where heat losses are severe thus peak temperatures are low, is noted.

276 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a new modeling approach that is based on the combination of the elementary-kinetic description of electrochemistry, where multi-step chemical mechanisms account for coupled charge-transfer and surface chemistry, and the physical representation of electric potential steps due to interfacial double layers, allowing to calculate the cell voltage without using the Nernst equation.

256 citations

Journal ArticleDOI
TL;DR: In this article, the authors evaluate three alternative formulations for simulating the steady-state flow and chemistry in a honeycomb channel for conditions that are typical of the catalytic combustion of natural gas.

222 citations


Cites methods from "Numerical modeling of catalytic ign..."

  • ...Laxminarayan L. Raja and Robert J. Kee Engineering Division Colorado School of Mines Golden, CO 80401 Olaf Deutschmann and Juergen Warnatz Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen (IWR) Universitaet Heidelberg 69120 Heidelberg, Germany Lanny D. Schmidt Department of Chemical Engineering and Material Science University of Minnesota Minneapolis, MN 55455 The objective of this paper is to evaluate three alternative formulations for simulating the steady-state flow and chemistry in a honeycomb channel for conditions that are typical of the catalytic combustion of natural gas....

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  • ...The reaction mechanism shown in Table 1 was developed by Deutschmann[15, 16, 17, 18] and is used in all the simulations in this paper....

    [...]

References
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Journal ArticleDOI
TL;DR: In this paper, the authors present a compilation of critically evaluated kinetic data on elementary homogeneous gas phase chemical reactions for use in modelling combustion processes Data sheets are presented for some 196 reactions each data sheet sets out relevant thermodynamic data, rate coefficient measurements, an assessment of the reliability of the data, references and recommended rate parameters Tables summarizing the preferred rate data are also given
Abstract: This compilation contains critically evaluated kinetic data on elementary homogeneous gas phase chemical reactions for use in modelling combustion processes Data sheets are presented for some 196 reactions Each data sheet sets out relevant thermodynamic data, rate coefficient measurements, an assessment of the reliability of the data, references, and recommended rate parameters Tables summarizing the preferred rate data are also given The reactions considered are limited largely to those involved in the combustion of methane and ethane in air but a few reactions relevant to the chemistry of exhaust gases and to the combustion of aromatic compounds are also included

1,986 citations

Journal ArticleDOI
TL;DR: The paper analyzes one-step methods for differential-algebraic equations (DAE) in terms of convergence order in view of extrapolation methods and certain perturbed asymptotic expansions are shown to hold.
Abstract: The paper analyzes one-step methods for differential-algebraic equations (DAE) in terms of convergence order. In view of extrapolation methods, certain perturbed asymptotic expansions are shown to hold. For the special DAE extrapolation solver based on the semi-implicit Euler discretization, the perturbed order pattern of the extrapolation tableau is derived in detail. The theoretical results lead to modifications of the known code. The efficiency of the modifications is illustrated by numerical comparisons over critical examples mainly from chemical combustion.

458 citations

Journal ArticleDOI
TL;DR: In this article, a detailed reaction mechanism and a multispecies transport model were used to simulate the explosion limits of the hydrogen-oxygen system and the minimum ignition energies for various mixture compositions, pressures, radii of the external energy source and ignition times.

440 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied the energetic, kinetic and structural properties of hydrogen chemisorbed on a Pd(100) surface by means of thermal desorption, work function and LEED measurements.

345 citations

Journal ArticleDOI
TL;DR: In this paper, angle resolved measurements of the sticking coefficient for H2 on Ni(111, Ni(110), Ni(100) and Pd(100), were performed, assuming a distribution of one-dimensional activation barriers.

248 citations