Numerical study on catalytic combustion and extinction characteristics of pre-mixed methane–air in micro flatbed channel under different parameters of operation and wall

Yan, Yunfei; Huang, Weipeng; Tang, Weimin; Zhang, Li; Li, Lixian; Ran, Jing Yu; Yang, Zhongqing

doi:10.1016/j.fuel.2016.04.085

Cited by 41 publications

(12 citation statements)

References 25 publications

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“…Based on the theory proposed by Kuo et al., the continuous hypothesis is suitable and the gas dynamic process was considered to be incompressible laminar. Therefore, the fluid‐volume force, dissipation, and gas‐radiation effect can be ignored, and the fluid flow is described by the Navier–Stokes equations, an energy conservation equation, and additional conservation equations for each chemical species …”

Section: Modeling Approachmentioning

confidence: 86%

“…In this model, the channel height of 1 mm is not only smaller than the quenching distance of gaseous methane/air (2.5 mm) combustion, but also smaller than the stability limit diameter (2.25 mm) of the gas‐phase reaction for stoichiometric methane/air in a tube . Additionally, due to the actual restriction of the Pt catalyst on gas‐phase methane oxidation, the impact of gaseous reactions on the whole catalytic reaction is small and the validity and rationality of this model has been demonstrated in our previous work . Thus, this numerical study on the catalytic combustion of methane/hydrogen/air only investigated the sole catalytic combustion effects without considering the gaseous chemistry.…”

Section: Modeling Approachmentioning

confidence: 99%

“…Therefore, the fluid-volumef orce,d issipation, and gas-radiatione ffect can be ignored, and the fluid flow is described by the Navier-Stokes equations, an energy conservationequation, and additional conservationequations for each chemical species. [3] Chemical kinetic model…”

Section: Modeling Approach Physicalmodel and Control Equationmentioning

confidence: 99%

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The Effect of Inlet Velocity on CH₄ Catalytic Combustion Behavior with H₂ Addition in a Microchannel Combustor

Yan

Tang

et al. 2017

Energy Tech

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The characteristics of premixed methane/air combustion in a microchannel with a Pt catalyst were examined and the effect of inlet velocity on catalytic methane combustion with hydrogen addition was investigated numerically. It is shown that appropriate hydrogen addition can expand the extinction limits, particularly the upper extinction limit of the inlet velocity, and increase methane conversion at higher inlet velocities. However, it is proved that methane conversion at an equivalent ratio of 0.8 decreased with hydrogen addition when inlet velocity was lower than 0.36 m s−1. The heat released in the hydrogen–oxygen reaction increased the wall temperature, which resulted in the adsorption–desorption equilibrium of oxygen shifting towards desorption as Pt(s) coverage increased and O(s) coverage decreased. With the same amount of hydrogen added, the changes in wall temperature that reflected the thermal effects of hydrogen were more obvious at higher inlet velocities, which improved methane conversion. If the heat released by hydrogen was neglected, the competitive consumption of oxygen, which demonstrates the chemical effect of hydrogen, was more significant at lower inlet velocities, which inhibited methane conversion.

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Section: Modeling Approachmentioning

confidence: 86%

Section: Modeling Approachmentioning

confidence: 99%

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The Effect of Inlet Velocity on CH₄ Catalytic Combustion Behavior with H₂ Addition in a Microchannel Combustor

Yan

Tang

et al. 2017

Energy Tech

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“…Substantial increases in flow rate would eventually result in incomplete conversion, breakthrough, and even blowout. This is due primarily to low residence times associated with high heat losses in the form of a hot exit gas (Kaisare et al, 2007b;Yan et al, 2016).…”

Section: Heat Lossmentioning

confidence: 99%

Computational Fluid Dynamics Simulation of the Thermal Uniformity in Catalytic Micro-Combustors

Chen¹,

Song²,

Xu³

2017

Frontiers in Heat and Mass Transfer

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The combustion and heat transfer characteristics of hydrogen-air or methane-air mixtures in catalytic micro-combustors were studied numerically to assess the impact of wall thermal properties and key operation parameters on the thermal uniformity. A two-dimensional computational fluid dynamics (CFD) model was developed with detailed hetero-/homogeneous chemistry, heat conduction within the solid wall, surface radiation heat transfer, and external heat losses. Parametric studies were carried out to investigate the effect of wall thermal conductivity, feed composition, and flow rate on the thermal uniformity during highly exothermic catalytic reactions. Comparisons of hydrogen-with methane-air systems were made. Based on these insights, an overall energy balance analysis was performed in terms of enthalpy loss. It was shown that the wall thermal properties strongly affect the thermal uniformity, but little impact on the extinction limit and conversion. The feed composition and flow rate have a significant impact on the operating temperature, but only a moderate effect on the thermal uniformity. Most of the enthalpy released by the exothermic reaction is lost to the surroundings under certain conditions, although this energy exchange becomes less efficient as the flow rate increases. This feature is beneficial for heat-exchanger applications.

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“…In order to fully understand these differences, more studies are required. One interesting topic includes how the operation and wall thermal properties affect combustion stability and the self-sustained combustion envelope through the change in reactivity and the Lewis number effect (Yan et al, 2016). Another interesting topic includes how the choice of combustor geometry affects the design and operation of micro-power generation systems (Zhang et al, 2017).…”

Section: Effect Of Reynolds Numbermentioning

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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Numerical study on catalytic combustion and extinction characteristics of pre-mixed methane–air in micro flatbed channel under different parameters of operation and wall

Cited by 41 publications

References 25 publications

The Effect of Inlet Velocity on CH₄ Catalytic Combustion Behavior with H₂ Addition in a Microchannel Combustor

The Effect of Inlet Velocity on CH₄ Catalytic Combustion Behavior with H₂ Addition in a Microchannel Combustor

Computational Fluid Dynamics Simulation of the Thermal Uniformity in Catalytic Micro-Combustors

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

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Numerical study on catalytic combustion and extinction characteristics of pre-mixed methane–air in micro flatbed channel under different parameters of operation and wall

Cited by 41 publications

References 25 publications

The Effect of Inlet Velocity on CH4 Catalytic Combustion Behavior with H2 Addition in a Microchannel Combustor

The Effect of Inlet Velocity on CH4 Catalytic Combustion Behavior with H2 Addition in a Microchannel Combustor

Computational Fluid Dynamics Simulation of the Thermal Uniformity in Catalytic Micro-Combustors

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

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The Effect of Inlet Velocity on CH₄ Catalytic Combustion Behavior with H₂ Addition in a Microchannel Combustor

The Effect of Inlet Velocity on CH₄ Catalytic Combustion Behavior with H₂ Addition in a Microchannel Combustor