It is an effective way to use coal slime as fuel for circulating fluidized bed boilers, which will not only solve its pollution to the environment, but also turn waste to treasure. In order to provide basic technical ...It is an effective way to use coal slime as fuel for circulating fluidized bed boilers, which will not only solve its pollution to the environment, but also turn waste to treasure. In order to provide basic technical information for transportation of coal slime from the coal preparation plant to the boiler, this paper experimentally studied the rheological behaviors of coal slime produced by filter-pressing. By using a rotational viscometer, the influences of water content, temperature, and shear time on the rheological behaviors of coal slime were investigated. Experimental results show that the coal slime will behave like Bingham plastics with low water content and like Bingham pseudo-plastics with 37.5% water content,while like pseudo-plastics with 40% water content. This indicates that the water content of coal slime must be controlled in consideration of both transportation resistance and combustion efficiency. Study results also show that, the apparent viscosity of coal slime at 5℃ is about 1.5–1.7 times of that at 40℃ for water contents 32%–37.5%, while the influence of temperature can be neglected when the water content is 40%. With increasing of water content, the influences of shear time on the apparent viscosity of coal slime becomes less. When the water content is more than 30%, the effect of shear time is negligible. It indicates that water content has the most important influence on the rheological behaviors of coal slime. There must be an optimal water content in considering conveying resistance and combustion efficiency. The environmental temperature must also be considered in coal slime transportation.展开更多
Researches on the boundary shape of fluid flow in porous media play an important role in engineering practices, such as petroleum exploitation, nuclear waste disposal and groundwater contamination. In this paper, six ...Researches on the boundary shape of fluid flow in porous media play an important role in engineering practices, such as petroleum exploitation, nuclear waste disposal and groundwater contamination. In this paper, six types of artificial porous samples (emery jade) with different porosities are manufactured. With the background of slow flow in porous media, laboratory experiments are carried out by observing the movement of five types of fluids with different dynamic viscosities in various types of porous media. A digital video recorder is employed to record the complete process of the fluid flow in the porous media. Based on the digital photos of the moving boundaries of fluid flow in porous media, the average displacement and fractal dimension of the moving boundary are estimated for different combinations of porosity and dynamic viscosity. Moreover, the evolution behavior of the average velocity and fractal dimension of the moving boundary with time is known. The statistical relations of the average velocity, the fractal dimension of the moving boundary and the porosity of porous media and the dynamic vis- cosity of fluids are proposed in this paper. It is shown that the front shape of the moving boundary of fluid flow in porous media is an integrated result of the porosity of porous media and the dynamic viscosity of fluids.展开更多
大叶片板式贮箱是当前最为先进的一种新型贮箱,大叶片板式结构是该贮箱推进剂管理的核心部件.对微重力条件下大叶片板式贮箱内流体行为进行了数值仿真和微重力试验验证.采用液体体积分数法(VOF,volume of fluid)两相流动模型数值模拟板...大叶片板式贮箱是当前最为先进的一种新型贮箱,大叶片板式结构是该贮箱推进剂管理的核心部件.对微重力条件下大叶片板式贮箱内流体行为进行了数值仿真和微重力试验验证.采用液体体积分数法(VOF,volume of fluid)两相流动模型数值模拟板式贮箱内流体流动特性,得到了流体分布规律.搭建了大叶片板式贮箱缩比模型试验系统,对板式贮箱内流体行为进行微重力落塔试验,得到微重力环境下流体特性.数值仿真和试验结果表明,大叶片板式贮箱在微重力环境下管理流体性能良好,大叶片板式结构为空间流体(包括低温流体)管理提供一种良好的途径.同时本文仿真和试验为国内板式贮箱设计提供了必要的支撑数据.展开更多
基金the National Key Technology R&D Program for the 12th Five-Year Plan of China (No. 2014BAB01B03)the National Natural Science Foundation of China (No. 51304192)
文摘It is an effective way to use coal slime as fuel for circulating fluidized bed boilers, which will not only solve its pollution to the environment, but also turn waste to treasure. In order to provide basic technical information for transportation of coal slime from the coal preparation plant to the boiler, this paper experimentally studied the rheological behaviors of coal slime produced by filter-pressing. By using a rotational viscometer, the influences of water content, temperature, and shear time on the rheological behaviors of coal slime were investigated. Experimental results show that the coal slime will behave like Bingham plastics with low water content and like Bingham pseudo-plastics with 37.5% water content,while like pseudo-plastics with 40% water content. This indicates that the water content of coal slime must be controlled in consideration of both transportation resistance and combustion efficiency. Study results also show that, the apparent viscosity of coal slime at 5℃ is about 1.5–1.7 times of that at 40℃ for water contents 32%–37.5%, while the influence of temperature can be neglected when the water content is 40%. With increasing of water content, the influences of shear time on the apparent viscosity of coal slime becomes less. When the water content is more than 30%, the effect of shear time is negligible. It indicates that water content has the most important influence on the rheological behaviors of coal slime. There must be an optimal water content in considering conveying resistance and combustion efficiency. The environmental temperature must also be considered in coal slime transportation.
基金the National Natural Science Foundation of China (Grant Nos. 10372112, 50674092, 50221402)National Basic Research Program of China (Grant No. 2002CB412701)+1 种基金 New Century Excellent Talents in University (Grant No. NCET-04-0491) Excellent Young Teachers Program of Ministry of Education of China
文摘Researches on the boundary shape of fluid flow in porous media play an important role in engineering practices, such as petroleum exploitation, nuclear waste disposal and groundwater contamination. In this paper, six types of artificial porous samples (emery jade) with different porosities are manufactured. With the background of slow flow in porous media, laboratory experiments are carried out by observing the movement of five types of fluids with different dynamic viscosities in various types of porous media. A digital video recorder is employed to record the complete process of the fluid flow in the porous media. Based on the digital photos of the moving boundaries of fluid flow in porous media, the average displacement and fractal dimension of the moving boundary are estimated for different combinations of porosity and dynamic viscosity. Moreover, the evolution behavior of the average velocity and fractal dimension of the moving boundary with time is known. The statistical relations of the average velocity, the fractal dimension of the moving boundary and the porosity of porous media and the dynamic vis- cosity of fluids are proposed in this paper. It is shown that the front shape of the moving boundary of fluid flow in porous media is an integrated result of the porosity of porous media and the dynamic viscosity of fluids.
文摘大叶片板式贮箱是当前最为先进的一种新型贮箱,大叶片板式结构是该贮箱推进剂管理的核心部件.对微重力条件下大叶片板式贮箱内流体行为进行了数值仿真和微重力试验验证.采用液体体积分数法(VOF,volume of fluid)两相流动模型数值模拟板式贮箱内流体流动特性,得到了流体分布规律.搭建了大叶片板式贮箱缩比模型试验系统,对板式贮箱内流体行为进行微重力落塔试验,得到微重力环境下流体特性.数值仿真和试验结果表明,大叶片板式贮箱在微重力环境下管理流体性能良好,大叶片板式结构为空间流体(包括低温流体)管理提供一种良好的途径.同时本文仿真和试验为国内板式贮箱设计提供了必要的支撑数据.
