Falcon离心分选机流场模拟及其计算理论的基础研究
发布时间：2018-11-28 18:44
【摘要】：随着细粒煤入洗比例的逐年提高以及高硫煤市场销售的限制,寻找更有效的细粒煤脱硫降灰新技术乃是当前煤炭工业的迫切任务和难题。采用离心力场分选的Falcon离心分选机在细粒煤的高效脱硫降灰中具有明显的优势。本论文主要利用数值计算以及CFD模拟研究Falcon离心分选机的流场特性,其中结合高速动态拍摄技术对流场进行实际观测,进而保证数值计算及模拟的有效应用。论文综述了细粒煤重选及目前选矿设备发展现状,阐述了适用于Falcon离心分选机数值模拟的多相流模型、湍流模型以及曳力模型,综述了目前多相流流场观测与CFD模拟的发展现状。整理并完善了关于Falcon离心分选机的计算理论,建立了分层区与分选区的流膜厚度计算公式,反冲水流量公式以及流膜分选下限计算公式,并进行了实验验证。通过研究得到:分层区流膜厚度与给料速度成正比,与离心机转速成反比,且流膜呈反比例函数曲线分布;分层区流膜厚度与反冲水压成正比和转速成反比;反冲水流速主要和水压和孔口结构有关;Falcon离心分选的分选下限受到颗粒极限脉动高度和表面波的双重限制。利用高速动态技术对离心分选机流场进行测试,获得流场流态以及流速信息,通过观查和实测发现:分层区流膜分布与数值计算分析吻合,且流膜厚度计算公式较为准确;采用雷诺应力模型模拟Falcon离心分选机流场流速与实测结果偏差不大,因此该模型具有良好的适用性;流场内存在雾化现象,会造成一定回流。CFD模拟中采用欧拉模型为多相流模型,雷诺应力模型为湍流模型,模拟得到离心分选机分层区与分选区内颗粒运动情况,切向、径向、轴向三向速度的分布情况,以及湍流场的分布情况。经研究发现:颗粒运动轨迹呈三维螺旋结构且来复圈内伴有一定的绕流运动;分层区速度分布与其他离心分选机相差不大,但分选区特别是来复圈内速度分布则大不相同;反冲水的引入使得分选区的湍流强度明显增加,但高强度湍流区域集中在近壁面薄层。此外,结合模拟得到的相关流场信息并利用模拟应用于实际问题,将CFD数值模拟应用于离心分选机分选机制和结构改造等方面。
[Abstract]:With the increasing of fine coal washing ratio year by year and the restriction of high sulfur coal market sales, it is an urgent task and difficult problem to find more effective desulfurization and ash reduction technology for fine coal. Falcon centrifugal separator with centrifugal force field separation has obvious advantages in high efficiency desulphurization and ash reduction of fine coal. In this paper, the flow field characteristics of Falcon centrifuge are studied by numerical calculation and CFD simulation. The flow field of Falcon centrifuge is observed in combination with high speed dynamic shooting technology, so as to ensure the effective application of numerical calculation and simulation. This paper summarizes the development of fine coal gravity separation and its equipment at present, and expounds the multiphase flow model, turbulence model and drag model suitable for numerical simulation of Falcon centrifuge separator. The development of multiphase flow field observation and CFD simulation is reviewed. The calculation theory of Falcon centrifugal separator is sorted out and improved. The formula of the thickness of flow film, the formula of backwash water flow and the calculation formula of lower limit of separation of flow film are established, and the experimental results are verified. The results show that the thickness of the flow film in the stratified zone is directly proportional to the feed speed and inversely proportional to the speed of the centrifuge, and the flow film is distributed in an inverse proportional function curve, and the thickness of the flow film in the stratified zone is directly proportional to the backwash water pressure and the speed of the flow film is inversely proportional to the speed of the centrifuge. The velocity of recoil water is mainly related to water pressure and pore structure, and the lower limit of separation for Falcon centrifugal separation is limited by the limit of particle pulsation height and surface wave. The flow field of centrifugal separator was measured by high speed dynamic technology, and the flow state and velocity information were obtained. Through observation and measurement, it was found that the flow film distribution in the stratified zone was in agreement with the numerical analysis, and the formula for calculating the thickness of the flow film was more accurate. The Reynolds stress model is used to simulate the flow velocity of Falcon centrifuge. The phenomenon of atomization exists in the flow field, which will cause a certain reflux. In the CFD simulation, the Euler model is used as the multiphase flow model, the Reynolds stress model is the turbulence model, and the movement of the particles in the stratified zone and the separation zone of the centrifugal separator is obtained by simulation, which is tangential and radial. The distribution of axial three direction velocity and the distribution of turbulent field. It is found that the velocity distribution of the stratified zone is not different from that of other centrifugal separators, but the velocity distribution in the sub-area, especially in the inner ring, is quite different from that of the other centrifugal separators, and the velocity distribution in the stratified zone is similar to that of the other centrifugal separators, and the velocity distribution in the stratified zone is different from that of other centrifugal separators. With the introduction of recoil water, the turbulence intensity of the subdistrict is increased obviously, but the high intensity turbulence region is concentrated near the wall layer. In addition, the CFD numerical simulation is applied to centrifuge sorting mechanism and structural modification by combining the relevant flow field information obtained from the simulation and the application of the simulation to practical problems.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD455.5
本文编号：2363922
[Abstract]:With the increasing of fine coal washing ratio year by year and the restriction of high sulfur coal market sales, it is an urgent task and difficult problem to find more effective desulfurization and ash reduction technology for fine coal. Falcon centrifugal separator with centrifugal force field separation has obvious advantages in high efficiency desulphurization and ash reduction of fine coal. In this paper, the flow field characteristics of Falcon centrifuge are studied by numerical calculation and CFD simulation. The flow field of Falcon centrifuge is observed in combination with high speed dynamic shooting technology, so as to ensure the effective application of numerical calculation and simulation. This paper summarizes the development of fine coal gravity separation and its equipment at present, and expounds the multiphase flow model, turbulence model and drag model suitable for numerical simulation of Falcon centrifuge separator. The development of multiphase flow field observation and CFD simulation is reviewed. The calculation theory of Falcon centrifugal separator is sorted out and improved. The formula of the thickness of flow film, the formula of backwash water flow and the calculation formula of lower limit of separation of flow film are established, and the experimental results are verified. The results show that the thickness of the flow film in the stratified zone is directly proportional to the feed speed and inversely proportional to the speed of the centrifuge, and the flow film is distributed in an inverse proportional function curve, and the thickness of the flow film in the stratified zone is directly proportional to the backwash water pressure and the speed of the flow film is inversely proportional to the speed of the centrifuge. The velocity of recoil water is mainly related to water pressure and pore structure, and the lower limit of separation for Falcon centrifugal separation is limited by the limit of particle pulsation height and surface wave. The flow field of centrifugal separator was measured by high speed dynamic technology, and the flow state and velocity information were obtained. Through observation and measurement, it was found that the flow film distribution in the stratified zone was in agreement with the numerical analysis, and the formula for calculating the thickness of the flow film was more accurate. The Reynolds stress model is used to simulate the flow velocity of Falcon centrifuge. The phenomenon of atomization exists in the flow field, which will cause a certain reflux. In the CFD simulation, the Euler model is used as the multiphase flow model, the Reynolds stress model is the turbulence model, and the movement of the particles in the stratified zone and the separation zone of the centrifugal separator is obtained by simulation, which is tangential and radial. The distribution of axial three direction velocity and the distribution of turbulent field. It is found that the velocity distribution of the stratified zone is not different from that of other centrifugal separators, but the velocity distribution in the sub-area, especially in the inner ring, is quite different from that of the other centrifugal separators, and the velocity distribution in the stratified zone is similar to that of the other centrifugal separators, and the velocity distribution in the stratified zone is different from that of other centrifugal separators. With the introduction of recoil water, the turbulence intensity of the subdistrict is increased obviously, but the high intensity turbulence region is concentrated near the wall layer. In addition, the CFD numerical simulation is applied to centrifuge sorting mechanism and structural modification by combining the relevant flow field information obtained from the simulation and the application of the simulation to practical problems.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD455.5
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