非球形顆粒典型流化床氣固兩相流數(shù)值模擬及實驗研究
發(fā)布時間：2018-07-31 19:40
【摘要】：氣固兩相顆粒系統(tǒng)廣泛存在于自然界和工業(yè)過程中。而在當前針對流化床內(nèi)氣固兩相流動的研究中,通�；谇蛐晤w粒的假設。盡管這樣能夠降低研究難度,但是不可避免的引入了誤差,尤其是造成了顆粒運動及脈動的各向異性特性缺失,導致了氣固兩相顆粒系統(tǒng)內(nèi)顆粒動力學特性的不同。在近期逐漸開展起來的非球形顆粒系統(tǒng)研究也主要應用離散單元模型(Discrete Element Method,DEM)中的軟球模型,使用硬球模型的研究還未見報道,相關機理與模型研究仍需進一步的探索。本文基于非球形顆粒間動量和能量守恒原理,應用DEM硬球模型研究了非球形顆粒稠密氣固兩相流動中的顆粒行為。以組合顆粒模型為基礎,采用四元數(shù)理論描述非球形顆粒的運動。對于顆粒碰撞搜尋算法,提出了幾何代數(shù)兩步搜尋方法,大大減少了非球形顆粒搜尋算法的計算需求,并保證了計算精度�；赗outh的圖解法,結合Poisson恢復系數(shù)假設和Coulumb定律,建立了適用于非球形顆粒的三維碰撞模型�；赑IV技術搭建了噴動床實驗臺,開展了非球形顆粒流態(tài)化行為的實驗研究,并應用本文建立的非球形顆粒DEM硬球模型進行了相同操作條件下噴動床內(nèi)顆粒行為的數(shù)值模擬研究。與球形顆粒相比,非球形顆粒噴動床內(nèi)顆粒的運動更為劇烈,顆粒的揚析現(xiàn)象更為明顯,床內(nèi)氣泡的邊界較為模糊,并且氣泡內(nèi)包含較多分散顆粒。對比數(shù)值模擬與實驗測量結果,可以看出應用非球形顆粒硬球模型得到的結果與實驗結果吻合較好,速度分布趨勢基本相同。應用建立的非球形顆粒離散顆粒硬球模型,對鼓泡流化床內(nèi)氣固兩相流體動力學特性進行了數(shù)值模擬研究。鼓泡流化床內(nèi)首先進行了球形顆粒動力特性的數(shù)值模擬研究,并得到了非常規(guī)重力加速度條件下顆粒的鼓泡行為。隨后,對比了非球形顆粒和球形顆粒的速度、顆粒分離情況、氣泡行為和顆粒的脈動運動等,獲得了不同彈性恢復系數(shù)和重力加速度條件下非球形顆粒的動力學特性。對單組份鼓泡流化床,非球形顆粒系統(tǒng)的氣固分布周期性規(guī)律較為復雜,并且在系統(tǒng)內(nèi)氣泡的邊界并不清晰,內(nèi)部存在大量分散的顆粒,氣泡的脈動運動趨勢不明顯,而顆粒的微觀脈動運動與氣泡的行為有著密切的聯(lián)系。對于雙組份鼓泡流化床,非球形顆粒雙組份鼓泡流化床中顆粒的混合較為均勻,其中氣泡的脈動運動要強于球形顆粒系統(tǒng)。應用建立的非球形顆粒離散顆粒硬球模型,對噴動流化床內(nèi)氣固兩相流體動力學特性進行了數(shù)值模擬研究。應用區(qū)域相關的顆粒行為分析方法,獲得了非球形顆粒與球形顆粒噴動流化床流態(tài)化特性在空間上的關聯(lián)。研究表明球形顆粒噴動流化床中的分區(qū)方式是以床內(nèi)中部為中心,不同的流化區(qū)域呈環(huán)形分布。而在非球形顆粒系統(tǒng)中,其分區(qū)呈現(xiàn)分層的形式。不同的分區(qū)特性表明球形顆粒與非球形顆粒的流態(tài)化行為存在較大的差異。應用建立的非球形顆粒離散顆粒硬球模型,對噴動流化床內(nèi)氣固兩相流體動力學特性進行了數(shù)值模擬研究。開展了非球形顆粒和球形顆粒系統(tǒng)內(nèi)顆粒聚團微觀脈動特性的研究,提出了廣義的聚團顆粒溫度的概念,用于考察顆粒系統(tǒng)中聚團的脈動運動。對球形顆粒系統(tǒng),不同曳力模型下的聚團顆粒溫度分布差別較大。大顆粒的分布更集中,小顆粒分布更分散。對非球形顆粒系統(tǒng),提升管中的顆粒位置分布較為均勻,聚團的微觀脈動運動也相對較弱。與球形顆粒系統(tǒng)類似,小顆粒的廣義聚團顆粒溫度比大顆粒的數(shù)值更大,說明了小顆粒及其顆粒聚團的脈動運動更劇烈。
[Abstract]:Gas-solid particle systems are widely used in natural and industrial processes. In the current study of gas-solid two-phase flow in a fluidized bed, the assumption of spherical particles is usually based on the assumption that it can reduce the difficulty of the study, but the error is inevitably introduced, especially the anisotropy of the particle motion and the pulsation. The loss is different in the particle dynamics in the gas-solid particle system. The research on the soft sphere model in the discrete element model (Discrete Element Method, DEM) is also mainly used in the recent development of the non spherical particle system. The research on the hard ball model has not been reported, and the related mechanism and model research still need to be further studied. In this paper, based on the principle of momentum and energy conservation among non spherical particles, the particle behavior in dense gas-solid two-phase flow of non spherical particles is studied by using the DEM hard ball model. Based on the combined particle model, the motion of non spherical particles is described by the four element number theory. Two steps of geometric algebra are proposed for the search algorithm of particle collision. In search method, the calculation requirement of non spherical particle search algorithm is greatly reduced and the calculation accuracy is guaranteed. Based on the graphical method of Routh, a three-dimensional collision model suitable for non spherical particles is established by combining the Poisson recovery coefficient hypothesis and the Coulumb law. A spouted bed experiment platform is built based on PIV technology, and the non spherical particle fluidized bed is carried out. For the experimental study, the numerical simulation of particle behavior in a spouted bed under the same operating conditions was carried out by using the non spherical particle DEM hard ball model established in this paper. Compared with the spherical particle, the motion of the particles in the non spherical particle spouted bed is more intense, the particle's uplift phenomenon is more obvious, the boundary of the bubble in the bed is more blurred. There are more dispersed particles in the bubble. Comparing the numerical simulation and the experimental results, it can be seen that the results obtained by the non spherical particle hard ball model are in good agreement with the experimental results, and the velocity distribution trend is basically the same. The application of the established non spherical particle discrete particle hard ball model to the gas-solid two-phase fluid dynamics in the bubbling fluidized bed The numerical simulation of the characteristics was carried out. The numerical simulation of the dynamic characteristics of the spherical particles was first carried out in a bubbling fluidized bed, and the bubbling behavior of the particles under the unconventional gravity acceleration was obtained. Then, the velocity of the non spherical and spherical particles, the particle separation, the bubble behavior and the pulsating motion of the particles were obtained. The dynamic characteristics of non spherical particles under the conditions of different elastic recovery coefficient and gravity acceleration are obtained. The periodic regularity of gas solid distribution in a single component bubbling fluidized bed is complicated, and the boundary of bubbles is not clear in the system, and there are a large number of dispersed particles in the interior of the system, and the fluctuating movement trend of the bubbles is not obvious. The microcosmic pulsation movement of the particles is closely related to the behavior of the bubbles. For the double component bubbling fluidized bed, the particle mixing in the bubbling fluidized bed with non spherical particles is more uniform, and the pulsation motion of the bubble is stronger than the spherical particle system. The application of the established non spherical particle discrete particle hard ball model to the spouted flow The aerodynamic characteristics of the gas-solid two-phase fluid in the bed are numerically simulated. The spatial correlation of the fluidization characteristics of the non spherical particles and the spherical particles in the spout fluidized bed is obtained by the method of region related particle behavior analysis. The study shows that the partition mode of the spherical particle spouted fluidized bed is centered in the middle of the bed. In the non spherical particle system, the zone presents a stratified form in the non spherical particle system. The different characteristics of the zoning show that there is a great difference in the fluidization behavior between the spherical particles and the non spherical particles. The application of the established non spherical particle discrete particle hard ball model is used to improve the gas-solid two-phase fluid dynamics in the spouted fluidized bed. The study on the microcosmic pulsation characteristics of the particles in the non spherical and spherical particles system has been carried out. The concept of the generalized cluster particle temperature is proposed to investigate the pulsating motion of the cluster in the particle system. The temperature distribution of the particles in the spherical particle system is different from that of the different drag models. The distribution of particles is more concentrated and the distribution of small particles is more dispersed. In the non spherical particle system, the distribution of particles in the riser is more uniform and the micropulsation motion of the cluster is relatively weak. Similar to the spherical particle system, the temperature of the small particles in the generalized agglomeration particles is larger than that of the large particles, indicating the pulsation of the small particles and their particles. Exercise is more intense.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：O359
本文編號：2156626
[Abstract]:Gas-solid particle systems are widely used in natural and industrial processes. In the current study of gas-solid two-phase flow in a fluidized bed, the assumption of spherical particles is usually based on the assumption that it can reduce the difficulty of the study, but the error is inevitably introduced, especially the anisotropy of the particle motion and the pulsation. The loss is different in the particle dynamics in the gas-solid particle system. The research on the soft sphere model in the discrete element model (Discrete Element Method, DEM) is also mainly used in the recent development of the non spherical particle system. The research on the hard ball model has not been reported, and the related mechanism and model research still need to be further studied. In this paper, based on the principle of momentum and energy conservation among non spherical particles, the particle behavior in dense gas-solid two-phase flow of non spherical particles is studied by using the DEM hard ball model. Based on the combined particle model, the motion of non spherical particles is described by the four element number theory. Two steps of geometric algebra are proposed for the search algorithm of particle collision. In search method, the calculation requirement of non spherical particle search algorithm is greatly reduced and the calculation accuracy is guaranteed. Based on the graphical method of Routh, a three-dimensional collision model suitable for non spherical particles is established by combining the Poisson recovery coefficient hypothesis and the Coulumb law. A spouted bed experiment platform is built based on PIV technology, and the non spherical particle fluidized bed is carried out. For the experimental study, the numerical simulation of particle behavior in a spouted bed under the same operating conditions was carried out by using the non spherical particle DEM hard ball model established in this paper. Compared with the spherical particle, the motion of the particles in the non spherical particle spouted bed is more intense, the particle's uplift phenomenon is more obvious, the boundary of the bubble in the bed is more blurred. There are more dispersed particles in the bubble. Comparing the numerical simulation and the experimental results, it can be seen that the results obtained by the non spherical particle hard ball model are in good agreement with the experimental results, and the velocity distribution trend is basically the same. The application of the established non spherical particle discrete particle hard ball model to the gas-solid two-phase fluid dynamics in the bubbling fluidized bed The numerical simulation of the characteristics was carried out. The numerical simulation of the dynamic characteristics of the spherical particles was first carried out in a bubbling fluidized bed, and the bubbling behavior of the particles under the unconventional gravity acceleration was obtained. Then, the velocity of the non spherical and spherical particles, the particle separation, the bubble behavior and the pulsating motion of the particles were obtained. The dynamic characteristics of non spherical particles under the conditions of different elastic recovery coefficient and gravity acceleration are obtained. The periodic regularity of gas solid distribution in a single component bubbling fluidized bed is complicated, and the boundary of bubbles is not clear in the system, and there are a large number of dispersed particles in the interior of the system, and the fluctuating movement trend of the bubbles is not obvious. The microcosmic pulsation movement of the particles is closely related to the behavior of the bubbles. For the double component bubbling fluidized bed, the particle mixing in the bubbling fluidized bed with non spherical particles is more uniform, and the pulsation motion of the bubble is stronger than the spherical particle system. The application of the established non spherical particle discrete particle hard ball model to the spouted flow The aerodynamic characteristics of the gas-solid two-phase fluid in the bed are numerically simulated. The spatial correlation of the fluidization characteristics of the non spherical particles and the spherical particles in the spout fluidized bed is obtained by the method of region related particle behavior analysis. The study shows that the partition mode of the spherical particle spouted fluidized bed is centered in the middle of the bed. In the non spherical particle system, the zone presents a stratified form in the non spherical particle system. The different characteristics of the zoning show that there is a great difference in the fluidization behavior between the spherical particles and the non spherical particles. The application of the established non spherical particle discrete particle hard ball model is used to improve the gas-solid two-phase fluid dynamics in the spouted fluidized bed. The study on the microcosmic pulsation characteristics of the particles in the non spherical and spherical particles system has been carried out. The concept of the generalized cluster particle temperature is proposed to investigate the pulsating motion of the cluster in the particle system. The temperature distribution of the particles in the spherical particle system is different from that of the different drag models. The distribution of particles is more concentrated and the distribution of small particles is more dispersed. In the non spherical particle system, the distribution of particles in the riser is more uniform and the micropulsation motion of the cluster is relatively weak. Similar to the spherical particle system, the temperature of the small particles in the generalized agglomeration particles is larger than that of the large particles, indicating the pulsation of the small particles and their particles. Exercise is more intense.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：O359
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