Maximum superadiabatic temperature for stabilized flames within porous inert media

Pereira, Fernando M.; Oliveira, Amir Antônio Martins; Fachini, Fernando F.

doi:10.1016/j.combustflame.2011.04.001

Cited by 16 publications

(19 citation statements)

References 21 publications

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“…Note, that the maximal temperature varies only weakly with the front velocity (x). This justifies using approximation (18) to estimate the limiting adiabatic temperature (DT lim ) with x 5 v th .…”

Section: Validationmentioning

confidence: 99%

“…6 and 7 under BCs 17) for the non-adiabatic case (compare thick and thin solid lines in Figure 5b,c). Approximations (18) and (21) were applied assuming x m 51 (the simplest form, see Conclusions). Relation (18), as mentioned above, underestimates the simulation results within the whole operation domain, while the heuristic correlation (21) shows a reasonable agreement with simulations (thick dashed lines in Figures 5 and 6).…”

Section: Validationmentioning

confidence: 99%

“…7,15 Gatica et al 16 obtained several relations between the front parameters, but, the problem was not closed analytically and only numerical solutions were presented. In series of the following studies [17][18][19][20][21][22] approximate pseudo-homogeneous and heterogeneous models of different complexity were proposed. The obtained analytical relations were not tested in a wide domain of operation conditions, the approximation of the minimal adiabatic temperature rise (DT lim ) was not addressed.…”

Section: Introductionmentioning

confidence: 99%

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What is the leanest stream to sustain a nonadiabatic loop reactor: Analysis and methane combustion experiments

2016

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While previous studies experimentally demonstrated that loop reactor (LR) can be sustained with a lean feed (using ethylene combustion) and have analyzed the single‐reaction adiabatic case, this work analyzes the effects of heat loss and of reactor size to determine the leanest stream (expressed in terms of adiabatic temperature rise ΔTlim) that will sustain the operation. For an adiabatic infinitely long reactor ΔTlim→0 while for a finite reactor ΔTlim scales as (1 + Pe/4)−1 where Pe = Luρcpf/k, and heat loss increases this limit by (β/Pe)1/2. Thus, a good design of a LR will aim to decrease conductivity (k) and radial heat‐transfer coefficient (β) while increasing throughput (u) and reactor length. This article is also the first experimental demonstration of auto‐thermal operation in a LR for catalytic abatement of low‐concentration of methane, showing the leanest stream to be of 8000 ppm vs. 33,000 ppm in a once‐through reactor. Experimental combustion results of methane and of ethylene are compared with model predictions. © 2016 American Institute of Chemical Engineers AIChE J, 63: 2030–2042, 2017

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Section: Validationmentioning

confidence: 99%

Section: Validationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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What is the leanest stream to sustain a nonadiabatic loop reactor: Analysis and methane combustion experiments

2016

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“…Excess enthalpy combustion in porous media [1,2], also known as energy concentration, draws constant interest from researchers due to its wide range of applications and outstanding features of heat recovery and pollutant control. The energy concentration phenomenon and combustion characteristics in porous burners have been investigated extensively in the literature including experimental [3][4][5][6][7][8], numerical [9][10][11][12][13][14][15][16] and analytical studies [16][17][18][19][20][21][22][23][24][25][26][27]. Babkin et al [21] presented a detailed review of this issue and stated that the phenomenon of energy concentration is more widespread in nature than was assumed previously.…”

Section: Introductionmentioning

confidence: 99%

Theoretical analysis of superadiabatic combustion for non-stationary filtration combustion by excess enthalpy function

et al. 2020

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The superadiabatic combustion for non-stationary filtration combustion is analytically studied. The non-dimensional excess enthalpy function ( H ) equation is theoretically derived based on a one-dimensional, two-temperature model. In contrast to the H equation for the stationary filtration combustion, a new term, which takes into account the effect of non-dimensional combustion wave speed, is included in the H equation for transient filtration combustion. The governing equations with boundary conditions are solved by commercial software Fluent. The predictions show that the maximum non-dimensional gas and solid temperatures in the flame zone are greater than 3 for equivalence ratio of 0.15. An examination of the four source terms in the H equation indicates that the thermal conductivity ratio ( Γ s ) between the solid and gas phases is the dominant one among the four terms and basically determines H distribution. For lean premixed combustion in porous media, the superadiabatic combustion effect is more pronounced for the lower Γ s .

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“…Since TPV systems require a temperature of operation above 1000°C, the ability to achieve superadiabatic temperatures is extremely interesting for this type of application, once less amount of fuel is required. Pereira et al (2009) and Pereira et al (2011) the energy equation in its suitable form for both the gas phase and the solid matrix. The two equations are simultaneously solved, once they are coupled through the convection heat exchange between them.…”

Section: Introductionmentioning

confidence: 99%

Simplified Heat Transfer Model for Stabelized Premixed Fla-Mes in Porous Media

Bueno¹,

Maranhão²,

Silva³

et al. 2017

Semioses

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This work presents a simplified steady state one dimensional heat transfer model for stabilized premixed flames in porous inert media. Two energy conservation equations describe the heat transfer process in solid and fluid regions of a porous burner. The thermophysical properties are considered constant and a plug flow is adopted. The stabilized premixed flame acts as a heat source in a specified section of the domain. The energy conservation equations are discretized by the finite volume method, using upwind scheme on the convective terms and central difference scheme on the diffusive terms. The linear systems of algebraic equations are solved by Tridiagonal Matrix Algorithm (TDMA). The results are compared with experimental and theoretical data. The effects of the porosity, Peclet number and thermal conductivity ratio between the solid and the fluid on temperature fields are depicted. Furthermore, the results reveal that the model is able to represent superadiabatic flames and the heat recirculation process in the porous burner.Keywords: Porous inert media. Super-adiabatic combustion. Heat recirculation. RESUMOO trabalho apresenta um modelo simplificado unidimensional em regime permanente da transferên-cia de calor em meio poroso para chamas estabilizadas pré-misturadas. Duas equações de conservação descrevem o processo de transferência de calor nas regiões sólida e fluida do do combustor poroso. As propriedades termofísicas são consideradas constantes e o perfil de velocidade transversal ao escoamento é constante. A chama pré-misturada e estabilizada atua como uma fonte de calor em uma seção específica do domínio. As equações de energia são discretizadas pelo método dos volumes finitos, usando o esquema upwind nos termos convectivos e o esquema de diferenças centrais nos termos difusivos. O sistema de equações algébricas lineares é resolvido pelo Tridiagonal Matrix Algorithm (TDMA). Os resultados são comparados com dados experimentais e teóricos. Os efeitos da porosidade, do número de Peclet e da razão entre a condutividade térmica do sólido pela do fluido são analisados. Além disso, os resultados revelam que o modelo é capaz de representar chamas superadiabáticas e o processo de recirculação de calor no combustor poroso. Palavras-chave:Meio inerte poroso. Combustão superadiabática. Recirculação de calor.

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Maximum superadiabatic temperature for stabilized flames within porous inert media

Cited by 16 publications

References 21 publications

What is the leanest stream to sustain a nonadiabatic loop reactor: Analysis and methane combustion experiments

What is the leanest stream to sustain a nonadiabatic loop reactor: Analysis and methane combustion experiments

Theoretical analysis of superadiabatic combustion for non-stationary filtration combustion by excess enthalpy function

Simplified Heat Transfer Model for Stabelized Premixed Fla-Mes in Porous Media

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