Numerical study of the chemical, thermal and diffusion effects of H 2 and CO addition on the laminar flame speeds of methane–air mixture

Liu, Jie; Zhang, Xin; Wang, Tao; Hou, Xiaofan; Zhang, Jibao; Zheng, Shizhuo

doi:10.1016/j.ijhydene.2015.04.133

Cited by 49 publications

(20 citation statements)

References 27 publications

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“…Based on these studies, it is expected that the addition of the hydrogen into biogas leads to positive effects in terms of improved laminar burning velocity, heat transfer rate, and flame temperature. This statement is further supported by numerous researches, which can be referred for the detailed analyses. On the contrary, there is a research gap regarding the effect of the hydrogen addition on the blowoff velocity of premixed biogas/air mixtures.…”

Section: Introductionmentioning

confidence: 82%

“…Due to its strong accessibility, the abundance of its sources and environmentally friendly combustion, biogas has drawn lots of attention in the field of combustion research . Although biogas brings these benefits, it has certain challenges restricting its use in the application of engine . One of the significant problems of biogas is the high content of CO 2 in the mixture, which also varies in composition with the primary hydrocarbon, CH 4 , based on the change of the temperature, pressure and the production method.…”

Section: Introductionmentioning

confidence: 99%

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Enhancement of biogas/air combustion by hydrogen addition at elevated temperatures

et al. 2019

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Summary In this study, combustion characteristics of various biogas/air mixtures with hydrogen addition at elevated temperatures were experimentally investigated using bunsen burner method. Methane, CH4, was diluted with different concentrations of carbon dioxide, CO2, 30 to 40% by volume, to prepare the biogas for testing. It is followed by the hydrogen, H2, enrichment within the range of 0 to 40% by volume and the temperature elevation of unburned gas till 440 K. Blowoff velocities were measured by lowering the jet velocity until a premixed flame could be stabilized at the nozzle exit, while laminar burning velocities were calculated by analyzing the shape of the directly captured premixed bunsen flames. The results showed that hydrogen had a positive effect on the blowoff velocity for all three fuel samples. Nonlinear growth of the blowoff velocity with hydrogen addition was associated to the dominance of methane‐inhibited hydrogen combustion process. It was also observed that the increase in the initial temperature of the unburned mixture led to a linear increase of the blowoff velocity. Moreover, specific changes in flame structure such as flame height, standoff distance, and the existence of tip opening were attributed to the change in the blowoff velocity. The effect of CO2 content in the mixture was examined with regards to laminar burning velocity for all compositions. The outcome of the experiment showed that the biogas mixture with higher content of CO2 possessed lower values of laminar burning velocity over the wide range of equivalence ratios. A reduced GRI‐Mech 3.0 was used to simulate the combustion of biogas/air mixtures with different compositions using ANSYS Fluent. The numerically simulated stable conical flames were compared with the experimental flames, in terms of flame structure, showing that the reduced GRI‐Mech 3.0 was suitable for modeling the combustion of biogas/air mixtures.

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Section: Introductionmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Enhancement of biogas/air combustion by hydrogen addition at elevated temperatures

et al. 2019

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“…(27), another calculation establishes the critical velocity of pyrolysis gases at the material surface for Ma=5.5, 6.5, 7.5, 8.5 and 9.5. The round dots in Fig.…”

Section: Analysis Of the Critical Velocity Of Pyrolysis Gases At The mentioning

confidence: 99%

“…The mathematical model of the heat and mass transport processes must take numbers of chemical reactions, gas-phase multi-component viscosities, thermal conductivities, diffusion coefficients, thermal diffusion coefficients, thermodynamics and chemical rates into consideration [19][20][21][22][23][24][25][26][27][28][29][30][31]. However, the combination of counterflow diffusion flame and surface ablation of charring materials has never been reported.…”

Section: Introductionmentioning

confidence: 99%

Protection of pyrolysis gases combustion against charring materials’ surface ablation

Huang

Wang

et al. 2016

International Journal of Heat and Mass Transfer

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractCharring ablation materials are widely used for thermal protection systems in a vehicle during hypersonic reentry. The pyrolysis gases from the charring materials can react with oxygen in the boundary layer, which makes the surface ablation rate decrease. The problem of protection of combustion of pyrolysis gases in charring material against surface ablation is solved by the detached normal shock wave relations and the counterflow diffusion flame model. The central difference format for the diffusion term and the upwind scheme for the convection term are used to discretize the mathematical model of the counterflow diffusion flame. Numerical results indicate that the combustion of pyrolysis gases in the boundary layer can completely protect the material surface from recession when the velocity of pyrolysis gases injecting to the boundary layer is higher than the critical velocity. There is an allometric relationship between the critical velocity and Mach number, and the combustion heat has little influence on the temperature distribution originating from the aerodynamic heating. This study will be helpful for the design of the thermal protection system in hypersonic reentry vehicles.

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“…It is known that such processes as Soret diffusion [2][3][4][5][6][7][8], radical-wall interaction [9][10][11][12][13][14][15][16][17], adding of flame inhibitors/flame suppressants [18,19] can affect the concentration of radicals in the In hydrocarbon flames the inclusion of Soret diffusion affects the mass fluxes of light components of reacting mixtures, mainly, H and H 2 [2][3][4][5][6][7]. In freely propagating flames it is sufficient to consider the thermal diffusion of H radicals, which causes the additional flux of H atoms in the downstream direction.…”

Section: Introductionmentioning

confidence: 99%

The effect of depletion of radicals on freely propagating hydrocarbon flames

et al. 2015

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In this work we investigate the properties and stability of deflagration waves in the model which include the two-step chain-branching reaction mechanism, first order reaction of conversion of radicals into products, and Newtonian cooling to the surroundings. The propagation velocity, the maximum temperature and concentration of radicals monotonically decay as the rate of the radical termination reaction is increased. The critical parameter values for the onset of instabilities and quenching of the travelling combustion wave are found. It is demonstrated that the depletion of radicals through the additional termination reaction enhances the onset of instabilities and extinction. The comparison of the efficiency of the radical and thermal quenching mechanisms is performed. The solutions emerging once the travelling deflagration wave becomes unstable are studied.

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Numerical study of the chemical, thermal and diffusion effects of H 2 and CO addition on the laminar flame speeds of methane–air mixture

Cited by 49 publications

References 27 publications

Enhancement of biogas/air combustion by hydrogen addition at elevated temperatures

Enhancement of biogas/air combustion by hydrogen addition at elevated temperatures

Protection of pyrolysis gases combustion against charring materials’ surface ablation

The effect of depletion of radicals on freely propagating hydrocarbon flames

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