The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Wan Ki Chow - One of the best experts on this subject based on the ideXlab platform.
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Flame Propagation of premixed liquefied petroleum gas explosion in a tube
Applied Thermal Engineering, 2017Co-Authors: Yan Huo, Wan Ki ChowAbstract:Abstract Flame Propagation in premixed liquefied petroleum gas (LPG) explosion was studied experimentally in a tube of diameter 2.6 m and length 25 m. Experiments on LPG explosion were conducted in a single zone first in this large explosion tube. The explosion tube was then divided into two zones with different mixing ratios of LPG and air. A thin polyvinyl chloride (PVC) film sheet was used to adjust the length of each zone. A total of three single-zone experiments and five two-zone experiments were carried out. Explosion phenomena and Flame Propagation in the tube were studied analytically using experimental results and theoretical analysis. A simple model for the Flame Propagation was proposed and tested using the experimental data in the present study and some literature results. Flame Propagation characteristics were found with a general trend to vary with time as an exponential function for adequate fuel with uniform concentrations within a certain distance of the tube. The Flame Propagation speed at a point in explosion depends on the turbulent burning speed and expansion ratio. Experimental data deviated more from the empirical exponential function for larger variations of fuel concentrations.
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Flame Propagation of premixed liquefied petroleum gas explosion in a tube
Applied Thermal Engineering, 2017Co-Authors: Yan Huo, Wan Ki ChowAbstract:Flame Propagation in premixed liquefied petroleum gas (LPG) explosion was studied experimentally in a tube of diameter 2.6 m and length 25 m. Experiments on LPG explosion were conducted in a single zone first in this large explosion tube. The explosion tube was then divided into two zones with different mixing ratios of LPG and air. A thin polyvinyl chloride (PVC) film sheet was used to adjust the length of each zone. A total of three single-zone experiments and five two-zone experiments were carried out. Explosion phenomena and Flame Propagation in the tube were studied analytically using experimental results and theoretical analysis. A simple model for the Flame Propagation was proposed and tested using the experimental data in the present study and some literature results. Flame Propagation characteristics were found with a general trend to vary with time as an exponential function for adequate fuel with uniform concentrations within a certain distance of the tube. The Flame Propagation speed at a point in explosion depends on the turbulent burning speed and expansion ratio. Experimental data deviated more from the empirical exponential function for larger variations of fuel concentrations.Department of Building Services Engineerin
Yan Huo - One of the best experts on this subject based on the ideXlab platform.
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Flame Propagation of premixed liquefied petroleum gas explosion in a tube
Applied Thermal Engineering, 2017Co-Authors: Yan Huo, Wan Ki ChowAbstract:Abstract Flame Propagation in premixed liquefied petroleum gas (LPG) explosion was studied experimentally in a tube of diameter 2.6 m and length 25 m. Experiments on LPG explosion were conducted in a single zone first in this large explosion tube. The explosion tube was then divided into two zones with different mixing ratios of LPG and air. A thin polyvinyl chloride (PVC) film sheet was used to adjust the length of each zone. A total of three single-zone experiments and five two-zone experiments were carried out. Explosion phenomena and Flame Propagation in the tube were studied analytically using experimental results and theoretical analysis. A simple model for the Flame Propagation was proposed and tested using the experimental data in the present study and some literature results. Flame Propagation characteristics were found with a general trend to vary with time as an exponential function for adequate fuel with uniform concentrations within a certain distance of the tube. The Flame Propagation speed at a point in explosion depends on the turbulent burning speed and expansion ratio. Experimental data deviated more from the empirical exponential function for larger variations of fuel concentrations.
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Flame Propagation of premixed liquefied petroleum gas explosion in a tube
Applied Thermal Engineering, 2017Co-Authors: Yan Huo, Wan Ki ChowAbstract:Flame Propagation in premixed liquefied petroleum gas (LPG) explosion was studied experimentally in a tube of diameter 2.6 m and length 25 m. Experiments on LPG explosion were conducted in a single zone first in this large explosion tube. The explosion tube was then divided into two zones with different mixing ratios of LPG and air. A thin polyvinyl chloride (PVC) film sheet was used to adjust the length of each zone. A total of three single-zone experiments and five two-zone experiments were carried out. Explosion phenomena and Flame Propagation in the tube were studied analytically using experimental results and theoretical analysis. A simple model for the Flame Propagation was proposed and tested using the experimental data in the present study and some literature results. Flame Propagation characteristics were found with a general trend to vary with time as an exponential function for adequate fuel with uniform concentrations within a certain distance of the tube. The Flame Propagation speed at a point in explosion depends on the turbulent burning speed and expansion ratio. Experimental data deviated more from the empirical exponential function for larger variations of fuel concentrations.Department of Building Services Engineerin
Yoshitaka Takeuchi - One of the best experts on this subject based on the ideXlab platform.
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Characteristics of Flame Propagation in a vortex core: Validity of a model for Flame Propagation☆
Combustion and Flame, 1997Co-Authors: Katsuo Asato, Hidetada Wada, Takayuki Hiruma, Yoshitaka TakeuchiAbstract:Abstract Characteristics of Flame Propagation for methane-, propane-, and hydrogen-air mixtures and the validity of a model for Flame Propagation in a vortex core were investigated experimentally using a vortex ring generated by pulsing a quantity of the mixture through a circular nozzle. The experimental results show that the ratio of the Flame speed to the maximum tangential velocity of the vortex core decreases as the maximum tangential velocity is increased. This experimental observation agrees qualitatively with predictions of a model that considers the shape of the Flame tip in the vortex core. The Flame speeds calculated by the proposed model are proportional to the square root of the ratio of the density of the unburned gas to that of the burned gas ( ρu ρb ) 1 2 , which agree with the experimental results. The present predictions better match the experimental results than those calculated using Chomiak's model. The constant of proportionality between Flame speed and ( ρu ρb ) 1 2 depends on the type of fuel used. This experimental observation is not predicted by Chomiak's model. The Flame speed in the vortex core can be predicted by a model of Flame Propagation taking into account the shape of the Flame tip. The calculated Flame speeds, however, are still higher than those obtained in experiments. In order to predict the Flame speed exactly, not only the shape of the Flame tip in the vortex core, but also the effects of baroclinic torque, curvature of the vortex core, unsteadiness of the Propagation velocity, and structure of the Flame in the vortex core should be considered.
Osamu Fujita - One of the best experts on this subject based on the ideXlab platform.
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Turbulent Flame Propagation limits of ammonia/methane/air premixed mixture in a constant volume vessel
Proceedings of the Combustion Institute, 2020Co-Authors: Genya Hashimoto, Khalid Hadi, Nozomu Hashimoto, Yu Xia, Aainaa Hamid, Akihiro Hayakawa, Hideaki Kobayashi, Osamu FujitaAbstract:Abstract Ammonia is one of promising energy carriers that can be directly used as carbon-neutral fuel for combustion applications. However, because of the low-burning velocity of ammonia, it is challenging to introduce ammonia to practical combustors those are designed for general hydrocarbon fuels. One of ways to enhance the combustibility of ammonia is by mixing it with other hydrocarbon fuels, such as methane, with a burning velocity is much higher than the burning velocity of ammonia. In this study, we conducted Flame Propagation experiments of ammonia/methane/air using a fan-stirred constant volume vessel to clarify the effect of methane addition to ammonia on the turbulent Flame Propagation limit. From experimental results, we constructed the Flame Propagation maps and clarified the Flame Propagation limits. The results show that the Flame Propagation limits were extended with an increase in mixing a fraction of methane to ammonia. Additionally, ammonia/methane/air mixtures with the equivalence ration of 0.9 can propagate at the highest turbulent intensity, even though the peak of the laminar burning velocity is the fuel-rich side because of the diffusional-thermal instability of the Flame surface. Furthermore, the Markstein number of the mixture obtained in this research successfully expressed the strength of the diffusional-thermal instability effect on the Flame Propagation capability. The turbulence Karlovitz number at the Flame Propagation limit monotonically increases with the decreasing Markstein number.
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Spherical turbulent Flame Propagation of pulverized coal particle clouds in an O2/N2 atmosphere
Proceedings of the Combustion Institute, 2019Co-Authors: Khalid Hadi, Ryo Ichimura, Nozomu Hashimoto, Osamu FujitaAbstract:Abstract The present study aims to clarify the effects of turbulence intensity and coal concentration on the spherical turbulent Flame Propagation of a pulverized coal particle cloud. A unique experimental apparatus was developed in which coal particles can be dispersed homogeneously in a turbulent flow field generated by two fans. Experiments on spherical turbulent Flame Propagation of pulverized coal particle clouds in a constant volume spherical chamber in various turbulence intensities and coal concentrations were conducted. A common bituminous coal was used in the present study. The Flame Propagation velocity was obtained from an analysis of Flame Propagation images taken using a high-speed camera. It was found that the Flame Propagation velocity increased with increasing Flame radius. The Flame Propagation velocity increases as the turbulence intensity increases. Similar trends were observed in spherical Flames using gaseous fuel. The coal concentration has a weak effect on the Flame Propagation velocity, which is unique to pulverized coal combustions in a turbulent field. These are the first reports of experimental results for the spherical turbulent Flame Propagation behavior of pulverized coal particle clouds. The results obtained in the present study are obviously different from those of previous pulverized coal combustion studies and any other results of gaseous fuel combustion research.
Wei Gao - One of the best experts on this subject based on the ideXlab platform.
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Flame Propagation and pressure characteristics of polymethyl methacrylate dust explosions in a horizontal pipe
Journal of Loss Prevention in the Process Industries, 2019Co-Authors: Bo Gan, Shulin Zhang, Mingrui Yang, Yonghao Zhou, Wei GaoAbstract:Abstract To reveal the characteristics of Flame Propagation and pressure in organic dust explosions during pneumatic transportation, 30 μm polymethyl methacrylate (PMMA) dust explosions with different airflow velocities were experimentally conducted in a horizontal pipe. The results showed that dust Flame transited from the luminous Flame with a continuous structure to discrete Flames as Flame propagating. After the appearance of the discrete Flames, Flame Propagation velocity increased sharply owing to the positive feedback coupling between combustion and expansion. With the increase of dust concentration, the average Flame Propagation velocity, maximum Flame temperature, temperature rising rate, maximum pressure, and maximum rate of pressure rise increased and then decreased. These explosion characteristics (except for the maximum Flame temperature) increased significantly with the increase of airflow velocity. When airflow velocity increased from 6.39 m/s to 13.3 m/s, the peaks of average Flame Propagation velocity increased from 23.9 m/s to 38.2 m/s; the peaks of maximum pressure and maximum rate of pressure rise were increased by 1.9 and 6.1 times respectively. In addition, it was found that the optimum dust concentration decreased as airflow velocity increased. Furthermore, the relationship among Flame Propagation, temperature, and pressure was discussed in detail.
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Flame Propagation behaviors and temperature characteristics in polyethylene dust explosions
Powder Technology, 2018Co-Authors: Bo Gan, Wei Gao, Haipeng Jiang, Qi ZhangAbstract:Abstract To reveal the Flame Propagation mechanism in polyethylene (PE) dust explosions, the Flame Propagation behaviors and temperature characteristics of polyethylene dust clouds were experimentally studied in an open duct. Flame Propagations in polyethylene dust clouds with different concentrations and particle size distributions were recorded using high-speed photography. The Flame temperatures were measured using two fine thermocouples comprising Pt–Pt/Rh13% wires of diameter 25 μm. Because of severe agglomeration, the minimum explosible concentration of polyethylene particles with diameter
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effects of particle size distributions on pmma dust Flame Propagation behaviors
Powder Technology, 2017Co-Authors: Xinyan Zhang, Wei Gao, Jinhua Sun, Dawei Zhang, Song Guo, Ritsu DobashiAbstract:Abstract Experiments of polymethyl methacrylate (PMMA) dust clouds with same Sauter diameters were conducted to reveal the effects of particles size distributions on PMMA dust Flame Propagation behaviors. High-speed photography was used to capture the Flame Propagation behaviors and microstructures. The results showed that the combustion behaviors of PMMA dust clouds with different mass fractions of 100 nm, 5 μm and 30 μm PMMA dust particles were complicated. The macroscopical developments of the Flames were determined by the major mass proportion dust particles. The Flame front became smoother and the average pulsating Flame Propagation velocity was faster with more proportion of smaller PMMA dust particles. The Flame temperatures were detected by a fine thermocouple comprising 25 μm-diameter Pt-Pt/Rh13% wires. It was found that the faster the Flame propagated, the higher maximum Flame temperature was. The maximum temperatures of mixture B and E dust clouds could maintain longer time due to the larger mass fractions of smaller particles. The thermal conversion processes of mixture A–E dust clouds were dominated by the external heat transfer sources, including radiation from burned region and heat convection between particles and gases. And pyrolysis/devolatilization controlled the overall mixture B–E dust clouds combustion processes. Flames of mixtures were coupled with the premixed gas Flame of the smaller particles, the diffusion Flame of the agglomerates accompanying local premixed Flame around split agglomerates, and the diffusion Flame accompanying local premixed Flame in high pyrolyzates concentration areas of larger particles. The combustion mechanism was determined by the dominant mass fraction dust particles. Smaller particles not only accelerated Flame Propagation but influenced the Flame structure and combustion mechanism.
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Flame Propagation behaviors of nano- and micro-scale PMMA dust explosions
Journal of Loss Prevention in the Process Industries, 2016Co-Authors: Xinyan Zhang, Xingqing Yan, Qiaofeng Xie, Wei GaoAbstract:Abstract Flame Propagation behaviors of nano- and micro-polymethyl methacrylate (PMMA) dust explosions were experimentally studied in the open-space dust explosion apparatus. High-speed photography with normal and microscopic lenses were used to record the particle combustion behaviors and Flame microstructures. Simple physical models were developed to explore the Flame Propagation mechanisms. High-speed photographs showed two distinct Flame Propagation behaviors of nano- and micro-PMMA dust explosions. For nano-particles, Flame was characterized by a regular spherical shape and spatially continuous combustion structure combined with a number of luminous spot Flames. The Flame Propagation mechanism was similar to that of a premixed gas Flame coupled with solid surface combustion of the agglomerates. In comparison, for micro-particles, Flame was characterized by clusters of Flames and the irregular Flame front, which was inferred to be composed of the diffusion Flame accompanying the local premixed Flame. It was indicated that smaller particles maintained the leading part of the propagating Flame and governed the combustion process of PMMA dust clouds. Increasing the mass densities from 105 g/m 3 to 217 g/m 3 for 100 nm PMMA particles, and from 72 g/m 3 to 170 g/m 3 for 30 μm PMMA particles, the Flame luminous intensity, scale and the average Propagation velocity were enhanced. Besides, the Flame front became more irregular for 30 μm PMMA dust clouds.
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Flame Propagation mechanisms in dust explosions
Journal of Loss Prevention in the Process Industries, 2015Co-Authors: Wei Gao, Toshio Mogi, Jinhua Sun, Xingqing Yan, Ritsu DobashiAbstract:Abstract To reveal the effects of particle characteristics, including particle thermal characteristics and size distributions, on Flame Propagation mechanisms during dust explosions clearly, the Flame structures of dust clouds formed by different materials and particle size distributions were recorded using an approach combining high-speed photography and a band-pass filter. Two obviously different Flame Propagation mechanisms were observed in the experiments: kinetics-controlled regime and devolatilization-controlled regime. Kinetics-controlled regime was characterized by a regular shape and spatially continuous combustion zone structure, which was similar to the premixed gas explosions. On the contrary, devolatilization-controlled regime was characterized by a complicated structure that exhibited heterogeneous combustion characteristics, discrete blue luminous spots appeared surrounding the yellow luminous zone. It was also demonstrated experimentally that the Flame Propagation mechanisms transited from kinetics-controlled to devolatilization-controlled while decreasing the volatility of the materials or increasing the size of the particles. Damkohler number was defined as the ratio of the heating and devolatilization characteristic time to the combustion reaction characteristic time, to reflect the transition of Flame Propagation mechanisms in dust explosions. It was found that the kinetics-controlled regime and devolatilization-controlled regime can be categorized by whether Damkohler number was less than 1 or larger than 1.