Effect of structural conduction and heat loss on combustion in micro-channels

Leach, Timothy T.; Cadou, Christopher P.; Jackson, Gregory S.

doi:10.1080/13647830500277332

Cited by 75 publications

(44 citation statements)

References 17 publications

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“…This work shows that streamwise heat conduction within the structure of the combustor is a dominating effect at the microscale chambers. Recent analytical and numerical work by Leach et al [15] demonstrated similar effects in micro-channels. Also, in another research [16] , they claimed that axial conduction of heat through walls plays a major role in determining the performance of micro-combustor.…”

Section: Introductionmentioning

confidence: 53%

Investigation over the recirculation influence on the combustion of micro organic dust particles

Bidabadi

Fanaee

Rahbari

2010

Appl. Math. Mech.-Engl. Ed.

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This paper investigates the role of recirculation and non-unity Lewis number on the combustion of organic dust particles. Since recirculation effect is more noticeable in micro-combustors, it is necessary to propose a modeling approach of this phenomenon to better simulate the performance of micro-combustors. In this research, in order to model the combustion of organic dust particles, it is assumed that the dust particles vaporize first to yield a known chemical structure which is oxidized in the gas phase, and the chemical structure of this gaseous fuel is assumed methane. To study the flame structure and solve the governing equations, it is considered that the flame structure consists of three zones titled the preheat-vaporization zone, the narrow reaction zone and finally the post flame zone. The recirculation phenomenon is evaluated by entering the exhausted heat from the post flame zone into the preheat zone. The solution is based on the following approach. First, the governing equations in each zone are nondimensionalized. Then the needed boundary and matching conditions are applied in each zone. After that, these equations and the required boundary and matching conditions are simultaneously solved with the analytical model. Consequently, the remarkable effects of recirculation and nonunity Lewis number on the combustion characteristics of the organic dust particles such as burning velocity and temperature profiles for different particle radii are obtained. The results show reasonable agreement with published experimental data.

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Section: Introductionmentioning

confidence: 53%

Investigation over the recirculation influence on the combustion of micro organic dust particles

Bidabadi

Fanaee

Rahbari

2010

Appl. Math. Mech.-Engl. Ed.

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“…However, high thermal conductivity walls offer a larger hot area for external heat losses and become susceptible to spatially global-like extinction (Norton and Vlachos, 2004). To quantitatively differentiate between the different regions and monitor the possible blowout behavior, the flame location is defined as the axial position with the greatest reaction rate (Leach et al, 2006). The flame location in all cases occurs on the fluid centerline.…”

Section: Temperature Profilesmentioning

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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“…Their results showed that the wall thermal properties, flow velocity, and channel width have significant effects on the flame propagation, and cause extinction limits and multiple flame regimes. Leach et al (2006) and Seyed-Reihani and Jackson (2004) performed a one-dimensional numerically investigated the effects of heat exchange on the reaction zone thickness of stoichiometric premixed hydrogen-air mixtures in micro-channel combustors. They presented an analytical model, which is used to predict the reaction zone thickness of hydrogenair mixtures based on the thermal properties and the channel size.…”

Section: Introductionmentioning

confidence: 99%

EFFECT OF WALL THERMAL CONDUCTIVITY ON MICRO-SCALE COMBUSTION CHARACTERISTICS OF HYDROGEN-AIR MIXTURES WITH DETAILED CHEMICAL KINETIC MECHANISMS IN Pt/γ-Al2O3 CATALYTIC MICRO-COMBUSTORS

Chen¹,

Liu²,

Song³

2014

Frontiers in Heat and Mass Transfer

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To understand the effect of different thermal conductivities on catalytic combustion characteristics, effect of thermal conductivity on micro-combustion characteristics of hydrogen-air mixtures in Pt/γ-Al2O3 catalytic micro-combustors were investigated numerically with detailed chemical kinetics mechanisms. Three kinds of wall materials (100, 7.5, and 0.5 W/m·K) were selected to investigate the effect of heat conduction on the catalytic combustion. The simulation results indicate that the catalytic reaction restrains the gas phase reaction in Pt/γ-Al2O3 catalytic micro-combustors. The gas phase reaction restrained by Pt/γ-Al2O3 catalysts is sensitive to thermal boundary condition at the wall. For most conditions, the gas phase reaction cannot be ignored in Pt/γ-Al2O3 catalytic micro-combustors. For low thermal conductivity, the higher temperature gradient on the wall will promote the gas phase reaction shift upstream; high temperature gradient exists on the wall, and the hot spot can cause the material to melt or degrade the catalyst. Due to the gas phase reaction is ignited and sustained in micro-combustors by the heat from the catalytic reaction, the effect of thermal conductivity on micro-scale combustion characteristics is not as obvious as it is in micro-combustors without Pt/γ-Al2O3 catalysts.

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Effect of structural conduction and heat loss on combustion in micro-channels

Cited by 75 publications

References 17 publications

Investigation over the recirculation influence on the combustion of micro organic dust particles

Investigation over the recirculation influence on the combustion of micro organic dust particles

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

EFFECT OF WALL THERMAL CONDUCTIVITY ON MICRO-SCALE COMBUSTION CHARACTERISTICS OF HYDROGEN-AIR MIXTURES WITH DETAILED CHEMICAL KINETIC MECHANISMS IN Pt/γ-Al2O3 CATALYTIC MICRO-COMBUSTORS

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