Temperature distribution and control have been investigated in a liquefiedpetroleum gas (LPG) fluidized bed with hollow corundum spheres (A1_2O_3) of 0.867-1.212 mm indiameter at moderately high temperatures (800-1100...Temperature distribution and control have been investigated in a liquefiedpetroleum gas (LPG) fluidized bed with hollow corundum spheres (A1_2O_3) of 0.867-1.212 mm indiameter at moderately high temperatures (800-1100℃). Experiments were carried out for the airconsumption coefficient α in the range of 0.3 to 1.0 and the fluidization number N in the range of1.3 to 3.0. Particle properties, initial bed height, α and N all affect temperature distribution inthe bed. Bed temperature can be adjusted about 200℃ by combined the adjusting of α and N.展开更多
Coal pyrolysis gas from different ranks of coal was monitored on real time basis using photoionization mass spectroscopy. The molecular weight distribution of different products as a function of temperature from vario...Coal pyrolysis gas from different ranks of coal was monitored on real time basis using photoionization mass spectroscopy. The molecular weight distribution of different products as a function of temperature from various coal ranks studied was observed. It was noted that the release of different classes of compounds like phenols, alkenes, alkylated aromatics and aromatic skeletons was temperature dependent. For all the coal ranks at lower temperatures phenols were the main component, with alkenes and alkylated aromatics at slight higher temperatures and aromatic skeletons were released at the highest temperatures studied.展开更多
This study numerically simulated and investigated the flow field characteristics of a typical dual-pulse solid rocket motor with a soft pulse separation device through thermal insulation ablation under high-temperatur...This study numerically simulated and investigated the flow field characteristics of a typical dual-pulse solid rocket motor with a soft pulse separation device through thermal insulation ablation under high-temperature dual-pulse erosion.The ablation rate of ethylene-propylene-diene monomer(EPDM)insulator was measured after the experiment.Experimental results were analyzed through scanning electron microscopy and microcomputed tomography.The ablation mechanism of the EPDM insulator under the operation conditions of a dual-pulse solid rocket motor was evaluated by analyzing the results.The results reveal that the internal flow field of the motor with a soft pulse separation device is uniform.The original charred layer existing on the EPDM insulator surface in the first pulse combustor is the decisive factor affecting the final ablation rate of the dual-pulse motor during the second pulse operation,and the ablation characteristic region is easily formed with the exfoliation of the charred layer.The ablation rate difference of the insulator increases with gas velocity.展开更多
To study the temperature distribution and thermal-stress field in different service stages, a two-dimensional model of a turbine blade with thermal barrier coatings is developed, in which the conjugate heat transfer a...To study the temperature distribution and thermal-stress field in different service stages, a two-dimensional model of a turbine blade with thermal barrier coatings is developed, in which the conjugate heat transfer analysis and the decoupled thermal-stress calculation method are adopted. Based on the simulation results, it is found that a non-uniform distribution of temperature appears in different positions of the blade surface, which has directly impacted on stress field. The maximum temperature with a value of 1030 ℃ occurs at the leading edge. During the steady stage, the maximum stress of thermally grown oxide （TGO） appears in the middle of the suction side, reaching 3.75 GPa. At the end stage of cooling, the maximum compressive stress of TGO with a value of-3.5 GPa occurs at the leading edge. Thus, it can be predicted that during the steady stage the dangerous regions may locate at the suction side, while the leadine edge mav be more Drone to failure on cooling.展开更多
Al-7graphite composite was processed using Al-7graphite mushy prepared by electromagnetic-mechanical stirring method, and the influence of solid fraction on the distributing of graphite particles in ingot was studied....Al-7graphite composite was processed using Al-7graphite mushy prepared by electromagnetic-mechanical stirring method, and the influence of solid fraction on the distributing of graphite particles in ingot was studied. The results shows that the relationship between solid fraction and stirring temperature of mushy is: f(s) = 591.5-0.897 t (where f(s) is the solid fraction, t is the stirring temperature). For Al-7graphite composite, with the increasing of solid fraction, the aggregation extent of graphite particles reduced gradually, and when solid fraction was larger than 30%, graphite particles could distribute evenly in ingot.展开更多
Experimental analysis was conducted to study the impact of fuel-air mixing and dilution jet on the temperature distribution in a small gas turbine combustor using various optical diagnostic techniques.The strength and...Experimental analysis was conducted to study the impact of fuel-air mixing and dilution jet on the temperature distribution in a small gas turbine combustor using various optical diagnostic techniques.The strength and velocity of the swirler at the venturi exit were adjusted to modify the fuel-air mixture,which is presumed to dominate the heat release of the main combustion zone.Additionally,the dilution hole configuration,including the number and size of the holes,was varied to investigate the dilution effect on outlet temperature distribution.Various optical diagnostic techniques,such as particle image velocimetry,planar Mie scattering,and OH~*chemiluminescence,were used to measure the flow field,fuel spray distribution,and flame structure,respectively.A reduction in swirling strength led to a decrease in the average flow rate in the throat,which improved the structure and symmetry of the axial vortex system in the sleeve,enhanced the mixing of fuel and gas in the dome swirling air,and ultimately,improved the temperature uniformity of the heat release zone.Compared to larger and sparse dilution jets,smaller and dense dilution jets tended to generate hot spots shifted towards the radial middle area.展开更多
A three-dimensional steady-state mathematical model, considering the chemical reactions and transfers of momentum, heat and mass between the gas and solid phases, was developed to investigate the characteristics of th...A three-dimensional steady-state mathematical model, considering the chemical reactions and transfers of momentum, heat and mass between the gas and solid phases, was developed to investigate the characteristics of the shaft furnace with the central gas distribution (CGD) device. The model was verified by the practical production data of a COREX-3000 shaft furnace, and then, it was used to study the inner characteristics of the shaft furnace with CGD. The results show that, compared with the COREX shaft furnace without CGD, the gas utilization rate (UR) and solid metallization rate (MR) increase from 33.66% to 34.18% and 60.4% to 61.8%, respectively. Especially, the standard deviation of solid MR decreases from 6.9% to 0.8%, which means that the MR of direct reduced iron from the furnace with CGD is more uniform than that without CGD. Additionally, the effects of operational conditions and CGD design on gas UR, solid MR and direct reduced iron uniformity were further discussed and the optimized conditions were suggested.展开更多
During the loading process,buried gas pipes can experience severe stresses due to soil-structure interaction,the presence of traffic load,the soil’s column weight,daily and/or seasonal temperature changes and uniform...During the loading process,buried gas pipes can experience severe stresses due to soil-structure interaction,the presence of traffic load,the soil’s column weight,daily and/or seasonal temperature changes and uniform internal pressure.In this research,the finite element method is employed to evaluate the behavior of buried Medium Density Polyethylene(MDPE)pipes which have been subjected to damage at the pipe crown.The modeled pipe damage ranges from a very small circular hole to a large circular hole and elliptic holes with various minor to major diameter ratios,a/b,to simulate circular to crack-shaped defects.The computer simulation and stress analyses were performed using the ANSYS software finite element package.The stress distribution around the defect was determined under the aforementioned mechanical and thermal loading conditions.Then,the maximum values of Von Mises stresses in the damaged buried PE pipes,which were evaluated by finite element solution,were compared with their corresponding reduced strength for safe operation with a life expectancy of fifty years.Based on the results,the maximum Von Mises stress values in the defective buried polyethylene gas pipeline are significantly above the pipe strength limit at 35℃.The previously mentioned stress values increase with the following factors:temperature increase,increase in circular hole diameter and decrease in elliptic hole diameter ratio(a/b).The maximum stress in the damaged PE pipe is due to the simultaneous loading effects of soil column weight,internal pressure,vehicle wheel load and pipe temperature increase.Additionally,the novel finite element models and stress plots for the buried damaged pipe and the pipe material allowable strength will be used to investigate the correct repair method for the damaged gas pipeline and to choose the best patch arrangement which will assure a safe repair.展开更多
基金This work was financially suppoded by the Key Project Foundation for Science and Technology Research by the Education Ministry of China (No.00020).
文摘Temperature distribution and control have been investigated in a liquefiedpetroleum gas (LPG) fluidized bed with hollow corundum spheres (A1_2O_3) of 0.867-1.212 mm indiameter at moderately high temperatures (800-1100℃). Experiments were carried out for the airconsumption coefficient α in the range of 0.3 to 1.0 and the fluidization number N in the range of1.3 to 3.0. Particle properties, initial bed height, α and N all affect temperature distribution inthe bed. Bed temperature can be adjusted about 200℃ by combined the adjusting of α and N.
文摘Coal pyrolysis gas from different ranks of coal was monitored on real time basis using photoionization mass spectroscopy. The molecular weight distribution of different products as a function of temperature from various coal ranks studied was observed. It was noted that the release of different classes of compounds like phenols, alkenes, alkylated aromatics and aromatic skeletons was temperature dependent. For all the coal ranks at lower temperatures phenols were the main component, with alkenes and alkylated aromatics at slight higher temperatures and aromatic skeletons were released at the highest temperatures studied.
基金financially supported by the National Natural Science Foundation of China,under grant numbers 51876177,51276150,and 51576165。
文摘This study numerically simulated and investigated the flow field characteristics of a typical dual-pulse solid rocket motor with a soft pulse separation device through thermal insulation ablation under high-temperature dual-pulse erosion.The ablation rate of ethylene-propylene-diene monomer(EPDM)insulator was measured after the experiment.Experimental results were analyzed through scanning electron microscopy and microcomputed tomography.The ablation mechanism of the EPDM insulator under the operation conditions of a dual-pulse solid rocket motor was evaluated by analyzing the results.The results reveal that the internal flow field of the motor with a soft pulse separation device is uniform.The original charred layer existing on the EPDM insulator surface in the first pulse combustor is the decisive factor affecting the final ablation rate of the dual-pulse motor during the second pulse operation,and the ablation characteristic region is easily formed with the exfoliation of the charred layer.The ablation rate difference of the insulator increases with gas velocity.
基金supported by the National Natural Science Foundation of China(Grant Nos.51172192,11272275 and 11002122)the Natural Science Foundation of Hunan Province(Grant No.11JJ4003)the Doctoral Scientific Research Foundation of Xiangtan University(Grant Nos.KZ08022,KZ03013 and KF20140303)
文摘To study the temperature distribution and thermal-stress field in different service stages, a two-dimensional model of a turbine blade with thermal barrier coatings is developed, in which the conjugate heat transfer analysis and the decoupled thermal-stress calculation method are adopted. Based on the simulation results, it is found that a non-uniform distribution of temperature appears in different positions of the blade surface, which has directly impacted on stress field. The maximum temperature with a value of 1030 ℃ occurs at the leading edge. During the steady stage, the maximum stress of thermally grown oxide （TGO） appears in the middle of the suction side, reaching 3.75 GPa. At the end stage of cooling, the maximum compressive stress of TGO with a value of-3.5 GPa occurs at the leading edge. Thus, it can be predicted that during the steady stage the dangerous regions may locate at the suction side, while the leadine edge mav be more Drone to failure on cooling.
基金China and Tsinghua-Zhongda Postdoctoral Science Foundation.]
文摘Al-7graphite composite was processed using Al-7graphite mushy prepared by electromagnetic-mechanical stirring method, and the influence of solid fraction on the distributing of graphite particles in ingot was studied. The results shows that the relationship between solid fraction and stirring temperature of mushy is: f(s) = 591.5-0.897 t (where f(s) is the solid fraction, t is the stirring temperature). For Al-7graphite composite, with the increasing of solid fraction, the aggregation extent of graphite particles reduced gradually, and when solid fraction was larger than 30%, graphite particles could distribute evenly in ingot.
基金financially supported by the National Science and Technology Major Project(J2019-Ⅲ-0014-0057)the National Natural Science Foundation of China(92041001)。
文摘Experimental analysis was conducted to study the impact of fuel-air mixing and dilution jet on the temperature distribution in a small gas turbine combustor using various optical diagnostic techniques.The strength and velocity of the swirler at the venturi exit were adjusted to modify the fuel-air mixture,which is presumed to dominate the heat release of the main combustion zone.Additionally,the dilution hole configuration,including the number and size of the holes,was varied to investigate the dilution effect on outlet temperature distribution.Various optical diagnostic techniques,such as particle image velocimetry,planar Mie scattering,and OH~*chemiluminescence,were used to measure the flow field,fuel spray distribution,and flame structure,respectively.A reduction in swirling strength led to a decrease in the average flow rate in the throat,which improved the structure and symmetry of the axial vortex system in the sleeve,enhanced the mixing of fuel and gas in the dome swirling air,and ultimately,improved the temperature uniformity of the heat release zone.Compared to larger and sparse dilution jets,smaller and dense dilution jets tended to generate hot spots shifted towards the radial middle area.
基金the National Key Technology R&D Program during the“12th Five-year Plan”of China(Grant No.2011BAE04B02)the National Natural Science Foundation of China(Grant No.51574064)for their financial support.
文摘A three-dimensional steady-state mathematical model, considering the chemical reactions and transfers of momentum, heat and mass between the gas and solid phases, was developed to investigate the characteristics of the shaft furnace with the central gas distribution (CGD) device. The model was verified by the practical production data of a COREX-3000 shaft furnace, and then, it was used to study the inner characteristics of the shaft furnace with CGD. The results show that, compared with the COREX shaft furnace without CGD, the gas utilization rate (UR) and solid metallization rate (MR) increase from 33.66% to 34.18% and 60.4% to 61.8%, respectively. Especially, the standard deviation of solid MR decreases from 6.9% to 0.8%, which means that the MR of direct reduced iron from the furnace with CGD is more uniform than that without CGD. Additionally, the effects of operational conditions and CGD design on gas UR, solid MR and direct reduced iron uniformity were further discussed and the optimized conditions were suggested.
文摘During the loading process,buried gas pipes can experience severe stresses due to soil-structure interaction,the presence of traffic load,the soil’s column weight,daily and/or seasonal temperature changes and uniform internal pressure.In this research,the finite element method is employed to evaluate the behavior of buried Medium Density Polyethylene(MDPE)pipes which have been subjected to damage at the pipe crown.The modeled pipe damage ranges from a very small circular hole to a large circular hole and elliptic holes with various minor to major diameter ratios,a/b,to simulate circular to crack-shaped defects.The computer simulation and stress analyses were performed using the ANSYS software finite element package.The stress distribution around the defect was determined under the aforementioned mechanical and thermal loading conditions.Then,the maximum values of Von Mises stresses in the damaged buried PE pipes,which were evaluated by finite element solution,were compared with their corresponding reduced strength for safe operation with a life expectancy of fifty years.Based on the results,the maximum Von Mises stress values in the defective buried polyethylene gas pipeline are significantly above the pipe strength limit at 35℃.The previously mentioned stress values increase with the following factors:temperature increase,increase in circular hole diameter and decrease in elliptic hole diameter ratio(a/b).The maximum stress in the damaged PE pipe is due to the simultaneous loading effects of soil column weight,internal pressure,vehicle wheel load and pipe temperature increase.Additionally,the novel finite element models and stress plots for the buried damaged pipe and the pipe material allowable strength will be used to investigate the correct repair method for the damaged gas pipeline and to choose the best patch arrangement which will assure a safe repair.
