Gas-phase and catalytic combustion in heat-recirculating burners

Ahn, Jeongmin; Eastwood, C. D.; Sitzki, Lars; Ronney, Paul D.

doi:10.1016/j.proci.2004.08.265

Cited by 255 publications

(94 citation statements)

References 14 publications

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“…Experimental studies using a heat-recirculating combustion system have found that there is an optimum Reynolds number at a relatively shallow minimum fuel-air equivalence ratio (Ahn et al, 2005). The optimum Reynolds number and the minimum equivalence ratio are generally consistent with the findings in this study.…”

Section: Effect Of Reynolds Numbersupporting

confidence: 88%

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: Effect Of Reynolds Numbersupporting

confidence: 88%

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

Junjie¹,

Xu²

2017

AJHMT

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“…For catalytic microscale combustion applications, typically long residence time channel reactors are employed, such as the swiss-roll type reactor [4,22]. Considering the short catalytic substrate sample (19 mm) and the high reactant flow rates (200-1000 mL/min) used here, it is expected that only fractional conversion of the fuel and oxidizer mixture is achieved.…”

Section: Device Performance Implicationsmentioning

confidence: 99%

“…Since hydrocarbon fuels have an energy density of ∼40 MJ/kg, a device having an overall systemlevel efficiency (chemical-to-electrical energy) in excess of 1% would have a comparable energy density to the stateof-the-art Li-ion batteries (∼0.5 MJ/kg) [18,19]. Sustaining combustion, however, in small-scale channels necessitates the use of catalysts or advanced heat recirculating strategies, otherwise conduction heat loss owed to the high surface area of the device exceeds the heat generation rate (∼volume of the device), and self-sustained operation cannot be achieved [20][21][22][23]. In this application, it is envisioned that nanosized platinum catalysts can be used to sustain combustion at low operating temperatures, alleviating concerns with quenching.…”

Section: Introductionmentioning

confidence: 99%

Catalysis of Methanol‐Air Mixture Using Platinum Nanoparticles for Microscale Combustion

Applegate

Pearlman

Bakrania

2012

Journal of Nanomaterials

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High surface area, active catalysts containing dispersed catalytic platinum nanoparticles (d p ∼ 11.6 nm) on a cordierite substrate were fabricated and characterized using TEM, XRD, and SEM. The catalyst activity was evaluated for methanol oxidation. Experimental results were obtained in a miniature-scale continuous flow reactor. Subsequent studies on the effect of catalyst loading and reactor flow parameters are reported. Repeat tests were performed to assess the stability of the catalyst and the extent of deactivation, if any, that occurred due to restructuring and sintering of the particles. SEM characterization studies performed on the postreaction catalysts following repeat tests at reasonably high operating temperatures (∼500• C corresponding to ∼0.3T m for bulk platinum) showed evidence of sintering, yet the associated loss of surface area had minimal effect on the overall catalyst activity, as determined from bulk temperature measurements. The potential application of this work for improving catalytic devices including microscale reactors is also briefly discussed.

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“…One of the challenges in micro combustor design is to reduce the heat loss. To reduce the heat loss by reducing surface-to-volume ratio, wall thickness should be as small as possible [Ahn et al 2004]. The application of micro swiss-roll combustor includes portable electronics, such as cell phone, laptop, space vehicles, military uses, telecommunication, etc.…”

Section: Application Of Micro Ed Milling: Micro Swiss-roll Combustor mentioning

confidence: 99%

Micro Eletro Discharge Milling for Microfabrication

Ali¹,

Mehfuz²,

Khan³

et al. 2012

Micromachining Techniques for Fabrication of Micro and Nano Structures

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Gas-phase and catalytic combustion in heat-recirculating burners

Cited by 255 publications

References 14 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

Catalysis of Methanol‐Air Mixture Using Platinum Nanoparticles for Microscale Combustion

Micro Eletro Discharge Milling for Microfabrication

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