Junjie Chen^*, Xuhui Gao, Deguang Xu

Frontiers in Heat and Mass Transfer, Vol.6, pp. 1-13, 2015, DOI:10.5098/hmt.6.10

Abstract Effect of wall thermal conductivity on hydrogen self-ignition and hydrogen-assisted ignition of propane-air mixtures in different feeding modes from ambient cold-start conditions were investigated numerically with chemical kinetic model in Pt/γ-Al2O3 catalytic micro-combustors. For the steady and transient state, effect of wall thermal conductivity on self-ignition characteristics of lean hydrogen-air mixtures was presented, and hydrogenassisted combustion of propane-air mixtures was investigated numerically in the co-feed mode and the sequential feed mode. The computational results indicate the large thermal inertia of the micro-combustor solid structure leads to slow temperature dynamics, and transient response is dominated by the thermal inertia. The heat… More >

Xiaoqian Ma^a , Mo Yang^a,*, Yuwen Zhang^b

Frontiers in Heat and Mass Transfer, Vol.7, pp. 1-8, 2016, DOI:10.5098/hmt.7.36

Abstract Combustion mechanism of a 300 MW pulverized coal boiler is analyzed and the optimization of the performance of the boiler is carried out. The flow field, temperature field, devolatilization, char combustion and CO generation in the boiler furnace under actual condition is obtained by using Fluent. Three methods to improve the efficiency of boiler combustion are proposed based on the pulverized coal combustion mechanism; their feasibilities are verified through numerical simulation and analysis. The three proposed methods to increase the combustion efficiency may give theoretical reference for air arrangement and combustion optimization of the same type of burners. More >

Etim S. Udoetok^*

Frontiers in Heat and Mass Transfer, Vol.7, pp. 1-5, 2016, DOI:10.5098/hmt.7.39

Abstract The radiation of heat by a hot body of gas is studied and a Stefan-Boltzmann kind of equation is developed. The proposed gas radiation equation is used to estimate the volumetric total emissivity of gas. The proposed total emissivity highlights the characteristics observed in published charts. The proposed gas radiation model requires the estimation of photon heat capacity from experimental data. Accurate estimation of total gas emission is very useful in applications involving combustion. Ideal gas and constant specific heats assumptions were used in the analysis for simplification. More >

Junjie Chen^*, Wenya Song, Xuhui Gao, Longfei Yan, Deguang Xu

Frontiers in Heat and Mass Transfer, Vol.7, pp. 1-9, 2016, DOI:10.5098/hmt.7.3

Abstract The flame stability of single-pass heat-recirculation micro-combustors was investigated using computational fluid dynamics and compared to singlechannel micro-combustors with respect to critical heat loss coefficient and total power loss. The effect of wall thermal conductivity was also explored. The simulations show that heat recirculation profoundly affects blowout because of preheating of the cold incoming gases but has only minimal effect on extinction. In the limit of low-conductivity walls, the heat-recirculation micro-combustor is much more stable than the single-channel microcombustor. Under certain conditions, the heat recirculation micro-combustor can operate with room-temperature inlet and outlet streams and moderate outer wall temperatures while… More >

Shibo Wu¹, Weidong Chen^1,*, Jingxin Ma², Lan Liu¹, Shengzhuo Lu¹, Honglin Meng¹, Xiquan Song³

CMES-Computer Modeling in Engineering & Sciences, Vol.138, No.2, pp. 1207-1236, 2024, DOI:10.32604/cmes.2023.029471

Abstract Launch safety of explosive charges has become an urgent problem to be solved by all countries in the world as launch situation of ammunition becomes consistently worse. However, the existing numerical models have different defects. This paper formulates an efficient computational model of the combustion of an explosive charge affected by a bottom gap in the launch environment in the context of the material point method. The current temperature is computed accurately from the heat balance equation, and different physical states of the explosive charges are considered through various equations of state. Microcracks in the explosive charges are described with… More > Graphic Abstract

Hu Shi, Wei Cai, Xin Wang^*, Lei Song, Yuan Hu^*

Journal of Renewable Materials, Vol.11, No.12, pp. 3991-4006, 2023, DOI:10.32604/jrm.2023.029888

Abstract To solve the fire accidents caused by coal combustion, this work prepared four hybrid hydrogel materials using bio-based polymers, flame retardants, and inorganic materials. Compared to pure water and 3.5 wt% MgCl₂ solution, the as-prepared hydrogel presents good fire prevention performance. In addition, it is found that CO and CO₂ are not produced by coal when the pyrolysis temperature is lower than 200°C. During low-temperature pyrolysis, CO is more likely to be produced than CO₂, indicating inadequate pyrolysis behavior. At the same time, the addition of fire-preventing hydrogel can not only decrease the maximum CO₂ concentration before the critical temperature… More > Graphic Abstract

Binbin Yang^1,*, Leilei Liu¹, Yan Zhang¹, Jingyu Gong¹, Fan Zhang², Tiezhu Zhang¹

Energy Engineering, Vol.120, No.10, pp. 2233-2250, 2023, DOI:10.32604/ee.2023.028898

Abstract Gasoline compression ignition (GCI) has been considered as a promising combustion concept to yield ultra-low NO_X and soot emissions while maintaining high thermal efficiency. However, how to improve the low-load performance becomes an urgent issue to be solved. In this paper, a GCI engine model was built to investigate the effects of internal EGR (i-EGR) and pre-injection on in-cylinder temperature, spatial concentration of mixture and OH radical, combustion and emission characteristics, and the control strategy for improving the combustion performance was further explored. The results showed an obvious expansion of the zone with an equivalence ratio between 0.8~1.2 is realized… More >

John Freddy Gelves-Díaz^1,*, Ludovic Dorkis², Richard Monroy-Sepúlveda¹, Sandra Rozo-Rincón¹, Yebrail Alexis Romero-Arcos¹

Journal of Renewable Materials, Vol.11, No.10, pp. 3769-3787, 2023, DOI:10.32604/jrm.2023.029270

Abstract Secondary lignocellulosic biomass has proved to be useful as an energy source through its oxidation by means of combustion processes. In accordance with the above, in this paper, we wanted to study the ash from urban pruning residues that are generated in cities in the Neotropics. Species such as Licania tomentosa, Azadirachta indica, Ficus benjamina, Terminalia catappa, Leucaena leucocephala, Prosopis juliflora and Pithecellobium dulce were selected because they have been previously studied and showed potential for thermal energy generation. These materials were calcined in an oxidizing atmosphere and characterized by X-ray diffraction and fluorescence, scanning electron microscopy with microchemistry, BET… More > Graphic Abstract

John Freddy Gelves Díaz^1,*, Ludovic Dorkis², Richard Monroy-Sepúlveda¹, Sandra Rozo-Rincón¹, Gabriel de Jesús Camargo Vargas³

Journal of Renewable Materials, Vol.11, No.9, pp. 3547-3566, 2023, DOI:10.32604/jrm.2023.029267

Abstract The material associated with tree pruning in a city in the Colombian neotropics was characterized in order to determine its energy potential. The species studied for their relevance in the territory were Prosopis juliflora, Licania tomentosa, Terminalia catappa, Azadirachta indica, Pithecellobium dulce, Ficus benjamina and Leucaena leucocephala. Moisture content, bulk density, hygroscopic response, elemental chemical analysis, proximal analysis, calorific value, ease of ignition and combustion, thermogravimetric and heat flow analysis, steam generation capacity, and qualitative analysis of gases (mass spectrometry) were determined. The results that were obtained show high initial moisture contents that vary between 37% and 67% and a… More > Graphic Abstract

Junjie Chen^* , Wenya Song, Deguang Xu

Frontiers in Heat and Mass Transfer, Vol.8, pp. 1-10, 2017, DOI:10.5098/hmt.8.21

Abstract 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… More >