Experimental investigation and numerical analysis on flame stabilization of CH4/air mixture in a mesoscale channel with wall cavities

Wan, Jianlong; Fan, Aiwu; Liu, Yi; Yao, Hong; Liu, Wei; Gou, Xiaolong; Zhao, Daiqing

doi:10.1016/j.combustflame.2014.09.024

Cited by 149 publications

(32 citation statements)

References 44 publications

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“…The flame used by Marbach et al (2007) is formed on a porous media surface, the flame by Sakurai et al (2013) is stabilized in the stagnation flow field, and the flame by Wan et al (2015) is formed by utilizing the low-speed region of the cavity. First, our results are compared with the combustor developed by Wan et al Both combustor volume Vo and chamber volume Vi in the present study are smaller than those of Wan et al (2015). And further, both ηhl and ηex,loss are also smaller than those of Wan et al (2015).…”

Section: Exergy Loss Ratementioning

confidence: 99%

“…There are several different types of meso-scale combustors: (1) the premixed flat flame type formed on a porous plate (Marbach et al, 2007), (2) the flat flame type formed in stagnation flow (Sakurai et al, 2013), (3) the flame type stabilized by the cavity (Fan et al, 2009;Wan et al, 2015), (4) the flame type formed in the vortex flow (Li et al, 2009;Shimokuri et al, 2015) and so forth. Sakurai et al (2013) have developed a combustor that can be applied to the ultra-micro gas turbine.…”

Section: Introductionmentioning

confidence: 99%

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Combustion characteristics of an annular type meso-scale combustor

Suenaga

Yanaoka

Takeda

et al. 2016

JTST

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This study was conducted to develop a meso-scale annular type combustor that uses two types of coaxial cylindrical flames, rich premixed flame and diffusion flame. The combustor consists of inner and outer porous tubes, and rich C 3 H 8 -air mixture and air issued, respectively, through the inner tube outwardly and through the outer tube inwardly, forms a cylindrical stagnation plane sandwiched by the inner rich premixed flame and the outer diffusion flame. A petal type flame was also observed in the downstream of the cylindrical flames. Maintaining a constant equivalence ratio φ i and flow rate q i of the rich mixture, the overall equivalence ratio φ all is controlled by varying the air flow rate q o of the outer tube. In order to investigate the combustion performance, the temperature was measured inside and at the outlet of the combustion chamber. The heat loss rate and exergy loss rate were evaluated from the obtained temperature data. The minimum values of the heat loss rate and exergy loss rate were 0.30 and 0.57, respectively. These loss rates were compared with the performance of other meso-scale combustors.

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Section: Exergy Loss Ratementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Combustion characteristics of an annular type meso-scale combustor

Suenaga

Yanaoka

Takeda

et al. 2016

JTST

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“…(12) where q is the heat flux; ho is the exterior convective heat transfer coefficient and is assumed to be 20 W/(m 2 ·K) (Liu et al, 2016;Wan et al, 2015), a value in the range of free convection; Tw,o is the temperature at the exterior surface; Tamb is the ambient temperature and is assumed to be 300 K; εo is the exterior surface emissivity and is set as 0.8; σ is the Stephan-Boltzmann constant.…”

Section: Computation Schemementioning

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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“…Future efforts could be made to extend the operational limits to further increase the system output. Some potential methods such as machining a combustor with wall cavities [140] and using catalytic combustion [203,204] are worth trying. When considering the overall energy conversion (from chemical to electrical) efficiency, the calculated system efficiency at the maximum power condition for the best combustor configuration (quartz + SiC) is ∼0.08% (assuming that the radiation from both sides of the combustor are available to be harvested).…”

Section: −34mentioning

confidence: 99%

“…Past work on experimental micro/mesoscale combustion revealed a range of interesting flame features such as flames with repetitive extinction and ignition (FREI) [127] and various unstable flame patterns [63,65], demonstrated the enhancement of flame stability limits [66,[138][139][140], as well as developed prototype systems for electrical power generation [36,37,141]. However, experimental works have inherent difficulties in obtaining spatially resolved measurements at small scales.…”

Section: Introductionmentioning

confidence: 99%

Micro/mesoscale combustion based portable power generating system

Kang¹

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Micro/mesoscale combustion-driven power generation is a promising alternative to replace traditional batteries for powering small scale electronics owing to its much higher energy densities. However, the considerable heat losses from the combustor walls due to the dramatically increased surface-tovolume ratio, as well as the short flow residence time at small scales pose a technical challenge in stabilising the flame inside the micro/mesoscale combustor. On the other hand, the significantly enhanced flame-wall thermal coupling at small scales can also lead to some unique flame characteristics.Recently, solid state power conversion of the heat released in the micro/mesoscale combustor such as thermoelectric (TE) and thermophotovoltaic (TPV) has been favoured over traditional power conversion methods such as micro-turbines. This is due to the excessive mechanical and viscous losses that rotating machinery suffers from upon miniaturisation.One of the main aims of this thesis is to perform numerical simulations to investigate the fundamental aspects of micro/mesoscale combustion, such as micro-flame behaviours of propagation and stabilisation, the conditions under which flame dynamics occur and the choices that suppress them. A set of modelling techniques that gives guidelines and practices for performing the time-accurate micro/mesoscale combustion simulations has been developed through investigation. Knowledge on standard and well-accepted numerical methods in literature are collected in a cohesive document. The less well-established modelling choices have been thoroughly evaluated and discussed.Using the developed numerical models, the effects of hydrogen and carbon monoxide addition on premixed methane/air flame dynamics is investigated. Results show that the flame instabilities which exist in pure methane/air flames could be effectively suppressed via a small amount of additives. Deep understanding of the underlying physics and chemistry has been gained. The effects of wall temperature profiles on the simulated micro-flame behaviours are also studied. The role of the combustion heat release and the gas-solid heat transfer in determining the micro-flame propagation speed is identified.Experimental works are also carried out, towards a full system demonstration for micro-power generation. The focus is placed on the "wall thermal engineering" on the improvement of the combustor performance and power output. The thermally-orthotropic pyrolytic graphite for the combustor wall material is explored. Compared to an isotropic material of stainless steel, a widened flame stability limit with pyrolytic graphite is demonstrated. Moreover, a uniform and moderate temperature distribution over the combustor surface is achieved, which is favourable for thermoelectric power conversion applications. Meanwhile, a novel, compact mesoscale thermophotovoltaic power generating system using a combination of porous media combustion and a simple band-pass filtering method is developed. The use of the porous media effectively enh...

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Experimental investigation and numerical analysis on flame stabilization of CH4/air mixture in a mesoscale channel with wall cavities

Cited by 149 publications

References 44 publications

Combustion characteristics of an annular type meso-scale combustor

Combustion characteristics of an annular type meso-scale combustor

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

Micro/mesoscale combustion based portable power generating system

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