Homogeneous ignition of methane-air mixtures over platinum: Comparison of measurements and detailed numerical predictions

Dogwiler, Urs; Mantzaras, John; Benz, P.; Kaeppeli, Beat; Bombach, Rolf; Arnold, A.

doi:10.1016/s0082-0784(98)80077-5

Cited by 78 publications

(98 citation statements)

References 12 publications

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“…The numerical model is validated by comparing the results with the experimental data of Dogwiler et al (1998). Direct comparisons between simulation and experiment allow for an assessment of the CFD model used herein.…”

Section: Fig 3 Oh Concentration Profiles Along the Fluid Centerlinementioning

confidence: 99%

CFD Modeling of the Combustion Characteristics and Stability in Catalytic Micro-Channels

Junjie¹,

Xu²

2017

AJHMT

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Combustion characteristics and stability of premixed methane-air mixtures in catalytic micro-channels is studied numerically, using CFD (computational fluid dynamics). The characteristics of the fluid mechanics are also analyzed. A two-dimensional CFD model with detailed reaction mechanisms and multicomponent transport is developed to evaluate the effect of operating conditions on the combustion stability. The laminar flow is assumed, and steady-steady simulations are performed. The fuel-lean equivalence ratio operation limit for the system is determined by the analysis of Reynolds number. The primary focus is on CFD as a means of understanding thermal management at small scales. It is shown that an appropriate choice of the flow velocity is crucial in achieving the self-sustained operation. Large gradients in temperature and species concentration are observed, despite the small scales of the system under certain conditions. The flow velocity is very important as it determines the flame location. Furthermore, the flow velocity plays a dual, competing role in the stability of the system. Low flow velocities reduce the heat generation, whereas high flow velocities reduce the convective time-scale. There is a narrow regime of flow velocities that allows self-sustained operation. When a low-power system is desired, highly insulating materials should be preferred, whereas a high-power system would favor highly conductive materials. Engineering maps that delineate combustion stability are constructed. In order to gain further insight into the combustion characteristics of the system, the optimum Reynolds number is determined. Finally, design recommendations are made.

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Section: Fig 3 Oh Concentration Profiles Along the Fluid Centerlinementioning

confidence: 99%

CFD Modeling of the Combustion Characteristics and Stability in Catalytic Micro-Channels

Junjie¹,

Xu²

2017

AJHMT

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“…One-hundred images were integrated to increase the signalto-noise ratio. The PLIF was calibrated with absorption measurements performed with the laser sheet crossing laterally (z-direction) through both quartz windows, as in previous CH 4 /air studies [4].…”

Section: Laser Diagnosticsmentioning

confidence: 99%

“…The numerical models should be capable of reproducing crucial CST characteristics such as light-off, catalytic fuel conversion, and-for safety reasonsthe onset of homogeneous ignition. Elementary heterogeneous reaction schemes for simple fuels (CH 4 , CO, and H 2 ) over Pt were developed and tested in their capacity to reproduce measured light-off characteristics and minor species fluxes [1][2][3], whereas combined hetero-/homogeneous schemes for CH 4 and H 2 over Pt were validated recently [4,5]. In particular, the experimental and numerical investigation of Appel et al [5] assessed the homogeneous ignition capabilities of various H 2 /O 2 hetero-/homogeneous reaction schemes.…”

Section: Introductionmentioning

confidence: 99%

An experimental and numerical investigation of turbulent catalytically stabilized channel flow combustion of hydrogen/air mixtures over platinum

Appel

Mantzaras

Schaeren

et al. 2002

Proceedings of the Combustion Institute

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The turbulent catalytically stabilized combustion (CST) of fuel-lean hydrogen/air mixtures over platinum was investigated experimentally and numerically in channel-flow configurations. Experiments were performed in an optically accessible catalytic channel reactor, established by two Pt-coated ceramic plates 300 mm long and placed 7 mm apart, with incoming Reynolds numbers of 15,000 and 30,000. Planar laserinduced fluorescence of the OH radical was used to monitor the onset of homogeneous (gas-phase) ignition, one-dimensional (across the 7 mm transverse direction) Raman measurements of major species and temperature assessed the turbulent scalar transport, laser doppler velocimetry yielded the inlet velocity and turbulence, and thermocouples embedded beneath the catalyst provided the surface temperature distribution. Computations were carried out with a two-dimensional elliptic fluid mechanical code that included elementary heterogeneous and homogeneous chemical reaction schemes. Three different low-Reynolds number near-wall turbulence models were examined, in conjunction with a thermochemistry model that included a presumed-shape (Gaussian) probability density function approach for the gaseous reactions and a laminar-like closure for catalytic reactions. Comparisons between predictions and measurements have shown that key CST issues, such as catalytic fuel conversion and onset of homogeneous ignition, are strongly dependent on the particular turbulence model. Moreover, the discrepancies between predictions and measurements were ascribed to the capacity of the various turbulence models to capture the strong flow laminarization induced by the heat transfer from the hot catalytic surfaces. A turbulence model that yields good agreement with the measurements is presented as particularly suited for CST. Experiments and predictions have shown that a continuous increase of the turbulent transport led to incomplete combustion through the gaseous reaction zone with subsequent catalytic conversion of the leaked fuel and, finally, to extinction of the gaseous flame.

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“…In addition, multidimensional numerical models capable of treating detailed surface and gas-phase kinetics are now available, e.g. Dogwiler et al (1998), Deutschmann and Schmidt (1998). The onset of homogeneous ignition within the catalytic reactor is detrimental to the catalyst integrity (it can cause catalyst meltdown) and the knowledge of such an event is of prime interest to CST reactor design.…”

Section: Introductionmentioning

confidence: 99%

“…The gas-phase ignition is strongly influenced by the hetero/homogeneous coupling (catalytic fuel depletion, radical adsorption/desorption reactions) and, therefore, its accurate prediction requires the use of validated hetero/homogeneous chemical reaction schemes. In Dogwiler et al (1998) and (1999) we validated hetero/homogeneous reaction schemes in CST of CH4/air mixtures over Pt, using a 2-D elliptic fluid mechanical model with elementary hetero/homogeneous reaction schemes and experimental ignition characteristics from an optically-accessible catalytic combustor. Mantzaras and Benz (1999) have provided analytical homogeneous ignition criteria in 2-D channel configurations that included dependencies on the relevant chemical, flow, transport and geometrical parameters.…”

Section: Introductionmentioning

confidence: 99%

Catalytic Combustion of Hydrogen-Air Mixtures Over Platinum: Validation of Hetero/Homogeneous Chemical Reaction Schemes

Appel

Mantzaras

Schaeren

et al. 2004

Inter J Ener Clean Env

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The applicability of various hetero/homogeneous chemical reaction schemes in the catalytically stabilized combustion (CST) of hydrogen/air mixtures over platinum was investigated experimentally and numerically in channelflow configurations. The present work stems from the internationally intensified effort to commercialize power generation systems with ultra-low NOx (< 3 ppm), CSTbased gas turbines. Crucial in the development of such systems is the understanding of the heterogeneous (catalytic) kinetics, the homogeneous (gas-phase) kinetics, and their respective coupling. Experiments were performed at atmospheric pressure and laminar flow conditions in an optically-accessible catalytic channel combustor: planar laser induced fluorescence (PLIF) of the OH radical was used to monitor the onset of homogeneous ignition and line-Raman measurements provided the boundary-layer profiles of the temperature and major species. Measured homogeneous ignition distances were compared against numerical predictions obtained with a two-dimensional elliptic fluid mechanical model. Six homogeneous (elementary, reduced and single-step schemes) and three heterogeneous schemes were tested in the model. The comparisons have revealed substantial differences between measured and predicted homogeneous ignition distances (ranging from 8% to 85%) and, moreover, these differences were attributed primarily to the homogeneous reaction pathway.

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Homogeneous ignition of methane-air mixtures over platinum: Comparison of measurements and detailed numerical predictions

Cited by 78 publications

References 12 publications

CFD Modeling of the Combustion Characteristics and Stability in Catalytic Micro-Channels

CFD Modeling of the Combustion Characteristics and Stability in Catalytic Micro-Channels

An experimental and numerical investigation of turbulent catalytically stabilized channel flow combustion of hydrogen/air mixtures over platinum

Catalytic Combustion of Hydrogen-Air Mixtures Over Platinum: Validation of Hetero/Homogeneous Chemical Reaction Schemes

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