本文選題：離散單元法 + 顆粒流��； 參考：《中國科學(xué)院大學(xué)(中國科學(xué)院過程工程研究所)》2017年博士論文

【摘要】：離散單元法(Discrete element method,DEM)是顆粒流模擬的主流方法,并且能夠適應(yīng)不同顆粒物性以及設(shè)備操作條件。但DEM方法本身存在計(jì)算量巨大、模擬時(shí)間過長等問題,因而難以針對(duì)工業(yè)規(guī)模的設(shè)備進(jìn)行顆粒流動(dòng)混合過程的模擬。為了克服此困難,本論文在前人工作基礎(chǔ)上拓展并優(yōu)化了基于多尺度異構(gòu)超級(jí)計(jì)算系統(tǒng)的高效大規(guī)模離散單元模擬方法和程序,實(shí)現(xiàn)了膠囊和圓柱等非球形顆粒的模擬,并以此考察了滾筒混合器以及料斗內(nèi)顆粒物性對(duì)其流動(dòng)混合性能的影響,加深了對(duì)相應(yīng)設(shè)備中顆粒流動(dòng)混合機(jī)理的認(rèn)識(shí)。論文研究表明在水平滾筒內(nèi)采用交錯(cuò)抄板能夠促進(jìn)顆粒的徑向拋灑和沿抄板的軸向?qū)Я�。�?duì)所研究的滾筒,在最優(yōu)抄板結(jié)構(gòu)下,其軸向混合效率分別為無抄板滾筒和全抄板滾筒的16倍和5倍。模擬還表明該效應(yīng)對(duì)不同顆粒物性(粒徑、形狀、密度和摩擦系數(shù))和滾筒尺寸均存在,預(yù)示了其廣泛的應(yīng)用前景。論文研究還表明,滾筒內(nèi)膠囊顆粒的形狀能夠影響其堆積密度和空間取向,從而影響其混合性能。而在所考察的物性范圍內(nèi),顆粒密度對(duì)偏析結(jié)構(gòu)的影響較形狀更為顯著。利用顆粒形狀與密度的共同作用可進(jìn)一步提高混合性能。論文通過與實(shí)驗(yàn)數(shù)據(jù)的對(duì)比表明,三維非規(guī)則顆粒碰撞力模型較傳統(tǒng)的線性模型對(duì)料斗中落料過程模擬的準(zhǔn)確性更高。以此進(jìn)行的模擬表明:Beverloo方程一般能夠較好地預(yù)測(cè)多粒徑顆粒體系的落料行為,但在顆粒尺寸差異較大時(shí),會(huì)高估整體落料速度。分析表明,顆粒體系的力鏈強(qiáng)度明顯增加導(dǎo)致的內(nèi)部流動(dòng)阻力增大和動(dòng)態(tài)拱橋的形成是其重要成因。論文最后總結(jié)了對(duì)DEM模型與模擬方法的改進(jìn),及其在顆粒流動(dòng)與混合模擬研究中的應(yīng)用,并展望了其后續(xù)工作與工業(yè)應(yīng)用前景。
[Abstract]:Discrete element method (DEM) is the main method of particle flow simulation, and it can adapt to different particle properties and equipment operating conditions.However, the DEM method itself has many problems, such as huge computation and long simulation time, so it is difficult to simulate the particle flow mixing process for industrial scale equipment.In order to overcome this difficulty, this paper extends and optimizes the simulation method and program of high-efficient large-scale discrete element based on multi-scale heterogeneous supercomputing system, and realizes the simulation of non-spherical particles such as capsules and cylinders.The influence of particle properties in drum mixer and hopper on its flow mixing performance was investigated, and the mechanism of particle flow mixing in the corresponding equipment was further understood.In this paper, it is shown that the use of staggered plate in the horizontal drum can promote the radial sprinkling of particles and the axial flow along the plate.The axial mixing efficiency of the studied drum is 16 times and 5 times higher than that of the non-plate roller and the full plate plate roller respectively under the optimal plate reading structure.The simulation also shows that the effect exists for different particle size, shape, density and friction coefficient and cylinder size, which indicates its wide application prospect.It is also shown that the shape of the capsule particles in the drum can affect the packing density and spatial orientation, thus affecting their mixing properties.In the range of physical properties investigated, the effect of particle density on segregation structure is more significant than shape.The mixing performance can be further improved by the interaction of particle shape and density.By comparing with the experimental data, it is shown that the 3D irregular particle collision force model is more accurate than the traditional linear model in simulating the blanking process in the hopper.The simulation results show that the weight Beverloo equation can generally predict the blanking behavior of multi-particle system, but it can overestimate the overall blanking rate when the particle size is different.The analysis shows that the increase of internal flow resistance and the formation of dynamic arch bridge caused by the obvious increase of the strength of the force chain of the granular system are the important causes of its formation.Finally, the paper summarizes the improvement of DEM model and simulation method, and its application in particle flow and mixing simulation, and looks forward to its future work and industrial application.
【學(xué)位授予單位】：中國科學(xué)院大學(xué)(中國科學(xué)院過程工程研究所)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ027.1

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本文編號(hào)：1755185