Hydrodynamic cavitaion venturi tube technique is used for pico and nano bubble generations in coal column flotation. In order to determine the optimal design of hydrodynamic cavitation venture tube for pico and nano b...Hydrodynamic cavitaion venturi tube technique is used for pico and nano bubble generations in coal column flotation. In order to determine the optimal design of hydrodynamic cavitation venture tube for pico and nano bubble generation, a four-factor three-level Central Composite Design of Experimental was conducted for investigating four important design parameters of cavitation venturi tube governing the median size and the volume of pico and nano bubbles. The test results showed that maximum volume of pico and nano bubbles, 65–75%, and minimum mean pico and nano bubble size,150–240 nm, were achieved at the medium ratio of the diameter of outlet of the venturi-tube and diameter of throat(3–4), medium outlet angle(11–13°), high inlet angle(26–27°) and high ratio of the length of the throat and the diameter of throat(2.3–3). Study the effects of the producing pico and nano bubbles on fine coal flotation was performed in a 5 cm diameter 260 cm height flotation column. The optimal percentage of pico and nano bubbles was about 70%, which produced maximum combustible material recovery of 86% with clean coal ash content of 11.7%.展开更多
A new model for concentration dependence of polymer chain dimensions over the wholeconcentration range was proposed. The hydrodynamic volume of a solvated macromoleculewas found to be a universal function of the degre...A new model for concentration dependence of polymer chain dimensions over the wholeconcentration range was proposed. The hydrodynamic volume of a solvated macromoleculewas found to be a universal function of the degree of coil overlapping (c/c~*). The radiusof gyration (R_g) and the expansion coefficient (α) of polymer in solution or in bulk. pre-dicted by this model are much better in agreement with the experimental data of small angleX-ray scattering and neutron scattering from literature, than with the values predicted byother models and theories.展开更多
We propose a numerical solution to incorporate in the simulation of a system of conservation laws boundary conditions that come from a microscopic modeling in the small mean free path regime.The typical example we dis...We propose a numerical solution to incorporate in the simulation of a system of conservation laws boundary conditions that come from a microscopic modeling in the small mean free path regime.The typical example we discuss is the derivation of the Euler system from the BGK equation.The boundary condition relies on the analysis of boundary layers formation that accounts from the fact that the incoming kinetic flux might be far from the thermodynamic equilibrium.展开更多
Based on multi-fluid volume fraction and piecewise parabolic method （PPM）, a multi-viscosity-fluid hydrodynamic code MVPPM （Multi-Viscosity-Fluid Piecewise Parabolic Method） is developed and applied to the problem...Based on multi-fluid volume fraction and piecewise parabolic method （PPM）, a multi-viscosity-fluid hydrodynamic code MVPPM （Multi-Viscosity-Fluid Piecewise Parabolic Method） is developed and applied to the problems of shock-induced hydrodynamic interfacial instability and mixing. Simulations of gas/liquid interface instability show that the influences of initial perturbations on the fluid mixing zone （FMZ） growth are significant, especially at the late stages, while grids have only a slight effect on the FMZ width, when the interface is impulsively accelerated by a shock wave passing through it. A numerical study of the hydrodynamic interfacial instability and mixing of gaseous flows impacted by re-shocks is presented. It reveals that the numerical results are in good agreement with the experimental results and the mixing growth rate strongly depends on initial conditions. Ultimately, the jelly layer experiment relevant to the instability impacted by exploding is simulated. The shape of jelly interface, position of front face of jelly layer, crest and trough of perturbation versus time are given; their simulated results are in good agreement with experimental results.展开更多
部分充液下液力偶合器内部介质运动为离心力场作用下的复杂两相流动,而液相分布形态对涡轮输出特性有着直接影响。为掌握偶合器内液相分布规律,将工作腔内介质运动视为分层流动,采用流体体积法(Volume of fluid,VOF)两相流模型,追踪562...部分充液下液力偶合器内部介质运动为离心力场作用下的复杂两相流动,而液相分布形态对涡轮输出特性有着直接影响。为掌握偶合器内液相分布规律,将工作腔内介质运动视为分层流动,采用流体体积法(Volume of fluid,VOF)两相流模型,追踪562型标准桃形腔偶合器内不同工况下的气—液分界面。建立三维周期性流道模型,采用Realizable k-ε湍流模型和压力隐式算子分裂(Pressure-implicit with splitting of operators,PISO)压力耦合算法,并用内部面模拟泵、涡轮间的交互作用,转速比i=1.0和i=0.6时的叶片表面液相分布与文献中试验结果具有高度相似性。仿真结果表明,随泵涡轮间转差增大,气液分界面倾斜加剧,直至形成大的环流,而泵轮叶片压力面液相分布区域增大,吸力面液相减小;低挡圈(R=155 mm)对环流形态影响较小,主要起到限矩作用,而高挡圈(R=175 mm)可抑制大环流的产生。展开更多
限矩型液力偶合器始终工作在部分充液状态下,工作腔内部的工作液体做复杂的气-液两相螺旋环流运动。在不同的载荷工况下,工作液体气-液两相的具体分布形式和环流形态很大程度上决定了偶合器的限矩特性。为了掌握限矩型偶合器内部的气-...限矩型液力偶合器始终工作在部分充液状态下,工作腔内部的工作液体做复杂的气-液两相螺旋环流运动。在不同的载荷工况下,工作液体气-液两相的具体分布形式和环流形态很大程度上决定了偶合器的限矩特性。为了掌握限矩型偶合器内部的气-液两相环流特性,该文以YOXD200偶合器为分析模型,在建立全流道模型的基础上,应用滑移网格瞬态算法,两相流模型采用流体体积法VOF(volume of fluid)模型,对3种典型充液率下的环流形态进行CFD数值模拟分析。数值模拟结果很好地预测了在不同充液率下,随载荷的增加,内部气-液两相流体由小环流向大环流运动的转化过程。该文为实现限矩型液力偶合器转矩跌落工况点的预测及过载能力的估算提供了数值计算的方法和依据。展开更多
基金West Virginia State Coal and Energy Research Bureau(WVCERB)the Department of Mining Engineering,West Virginia University
文摘Hydrodynamic cavitaion venturi tube technique is used for pico and nano bubble generations in coal column flotation. In order to determine the optimal design of hydrodynamic cavitation venture tube for pico and nano bubble generation, a four-factor three-level Central Composite Design of Experimental was conducted for investigating four important design parameters of cavitation venturi tube governing the median size and the volume of pico and nano bubbles. The test results showed that maximum volume of pico and nano bubbles, 65–75%, and minimum mean pico and nano bubble size,150–240 nm, were achieved at the medium ratio of the diameter of outlet of the venturi-tube and diameter of throat(3–4), medium outlet angle(11–13°), high inlet angle(26–27°) and high ratio of the length of the throat and the diameter of throat(2.3–3). Study the effects of the producing pico and nano bubbles on fine coal flotation was performed in a 5 cm diameter 260 cm height flotation column. The optimal percentage of pico and nano bubbles was about 70%, which produced maximum combustible material recovery of 86% with clean coal ash content of 11.7%.
文摘A new model for concentration dependence of polymer chain dimensions over the wholeconcentration range was proposed. The hydrodynamic volume of a solvated macromoleculewas found to be a universal function of the degree of coil overlapping (c/c~*). The radiusof gyration (R_g) and the expansion coefficient (α) of polymer in solution or in bulk. pre-dicted by this model are much better in agreement with the experimental data of small angleX-ray scattering and neutron scattering from literature, than with the values predicted byother models and theories.
基金This work is supported by Thales Alenia Space.We are gratefully indebted to J.-F.Coulombel,F.GolseK.Aoki for many useful advices concerning this work and for their kind encouragements。
文摘We propose a numerical solution to incorporate in the simulation of a system of conservation laws boundary conditions that come from a microscopic modeling in the small mean free path regime.The typical example we discuss is the derivation of the Euler system from the BGK equation.The boundary condition relies on the analysis of boundary layers formation that accounts from the fact that the incoming kinetic flux might be far from the thermodynamic equilibrium.
基金supported by the National Natural Science Foundation of China (Grant Nos 10672151 and 10772166)the Foundation of China Academy of Engineering Physics (Grant No 2008B0202011)the Fundamental Quality and Reliability of National Defence Science and Technology Industry of China
文摘Based on multi-fluid volume fraction and piecewise parabolic method （PPM）, a multi-viscosity-fluid hydrodynamic code MVPPM （Multi-Viscosity-Fluid Piecewise Parabolic Method） is developed and applied to the problems of shock-induced hydrodynamic interfacial instability and mixing. Simulations of gas/liquid interface instability show that the influences of initial perturbations on the fluid mixing zone （FMZ） growth are significant, especially at the late stages, while grids have only a slight effect on the FMZ width, when the interface is impulsively accelerated by a shock wave passing through it. A numerical study of the hydrodynamic interfacial instability and mixing of gaseous flows impacted by re-shocks is presented. It reveals that the numerical results are in good agreement with the experimental results and the mixing growth rate strongly depends on initial conditions. Ultimately, the jelly layer experiment relevant to the instability impacted by exploding is simulated. The shape of jelly interface, position of front face of jelly layer, crest and trough of perturbation versus time are given; their simulated results are in good agreement with experimental results.
文摘部分充液下液力偶合器内部介质运动为离心力场作用下的复杂两相流动,而液相分布形态对涡轮输出特性有着直接影响。为掌握偶合器内液相分布规律,将工作腔内介质运动视为分层流动,采用流体体积法(Volume of fluid,VOF)两相流模型,追踪562型标准桃形腔偶合器内不同工况下的气—液分界面。建立三维周期性流道模型,采用Realizable k-ε湍流模型和压力隐式算子分裂(Pressure-implicit with splitting of operators,PISO)压力耦合算法,并用内部面模拟泵、涡轮间的交互作用,转速比i=1.0和i=0.6时的叶片表面液相分布与文献中试验结果具有高度相似性。仿真结果表明,随泵涡轮间转差增大,气液分界面倾斜加剧,直至形成大的环流,而泵轮叶片压力面液相分布区域增大,吸力面液相减小;低挡圈(R=155 mm)对环流形态影响较小,主要起到限矩作用,而高挡圈(R=175 mm)可抑制大环流的产生。
文摘限矩型液力偶合器始终工作在部分充液状态下,工作腔内部的工作液体做复杂的气-液两相螺旋环流运动。在不同的载荷工况下,工作液体气-液两相的具体分布形式和环流形态很大程度上决定了偶合器的限矩特性。为了掌握限矩型偶合器内部的气-液两相环流特性,该文以YOXD200偶合器为分析模型,在建立全流道模型的基础上,应用滑移网格瞬态算法,两相流模型采用流体体积法VOF(volume of fluid)模型,对3种典型充液率下的环流形态进行CFD数值模拟分析。数值模拟结果很好地预测了在不同充液率下,随载荷的增加,内部气-液两相流体由小环流向大环流运动的转化过程。该文为实现限矩型液力偶合器转矩跌落工况点的预测及过载能力的估算提供了数值计算的方法和依据。
