【作者】 陆启明；

【导师】 郁杰； 汪振；

【作者基本信息】 中国科学技术大学 ， 核能科学与工程， 2023， 硕士

【摘要】 核聚变反应堆内高能等离子体与壁面相互作用会产生大量金属粉尘,其在事故下存在燃爆风险,严重威胁聚变堆安全。然而目前,在这方面的实验数据非常缺乏,不足以支持核聚变反应堆的安全性评估。基于此,本文主要利用20 L球形爆炸装置进行微米级纯钨粉及与氢气、水蒸气等多元混合物的爆炸实验,借助瞬态压力测量系统、扫描电镜(SEM)、X射线衍射(XRD)等实验手段获取不同实验条件下微米级钨粉的爆炸性参数、火焰传播速度、爆炸产物微结构等数据,揭示了微米级钨粉的燃爆反应机理,建立了钨粉燃爆反应的物理图景。本文的主要工作和结论如下:(1)实验获得了微米级钨粉的爆炸强度参数。发现钨粉的最大可燃粒径在2～5 μm之间,钨粉最大爆炸压力随浓度呈现先上升后下降的趋势,最佳爆炸浓度为3000 g/m3,在该浓度下的最大爆炸压力为0.46 MPa,其最大压力上升速率为16 MPa/s,火焰传播速度接近4 m/s,钨粉的爆炸指数为4.346 MPa·m/s,爆炸危险等级为St1,属于弱爆炸性。(2)建立了描述爆炸前流场的CFD-DPM三维数值模型。对20 L球形爆炸实验的钨粉扬尘过程进行数值模拟,得到了在不同时间点下,流动速度,湍动能,压力等的分布,并和实验结果进行了比较,得到最佳点火延迟时间在80 ms左右。(3)分析了不同初始条件对纯钨粉燃爆的影响。发现初始压力在0.06 MPa～0.1 MPa范围内,最大爆炸压力成正比关系,主要是由于单位体积助燃剂浓度与初始压力呈线性关系;发现点火延迟时间对钨粉的最大爆炸压力呈现先增大后减小的趋势,并且通过实验及数值模拟得到最佳点火延迟时间在80 ms左右;发现存在一个最小点火能才能点燃钨粉爆炸;发现在测量范围内(20-120℃),钨粉的最大爆炸压力随着初始温度的升高而减小。(4)探究了氢气、水蒸气对钨粉燃爆反应的影响。发现氢气对最大爆炸压力大小呈现先增加后减小的趋势,且随粉尘浓度增加整体呈现明显的下降趋势。并发现加入水蒸气可以削减燃烧和爆炸的强度,起到一定的抑燃和抑爆作用。本文研究成果能够为聚变堆粉尘爆炸危害评估和抑爆系统设计提供重要理论指导和数据支持,此外,该方法还可以为食品、冶金等传统工业体系中的可燃性气体/粉尘爆炸研究提供参考借鉴。更多还原

【Abstract】 The interaction between high energy plasma and wall surface in nuclear fusion reactor will produce a large amount of metal dust,which has the risk of explosion in an accident and seriously threatens the safety of fusion reactor.However,experimental data in this area are very lacking to support the safety of Evaluation of nuclear fusion reactors.Based on this,this paper mainly uses 20 L spherical explosive device to carry out explosion experiments of micron-level pure tungsten powder and multi-component mixtures such as hydrogen and water vapor.With the help of transient pressure measurement system,scanning electron microscopy(SEM),X-ray diffaction(XRD)and other experimental means,explosive parameters,flame propagation velocity,microstructure of explosive products and other data under different experimental conditions are obtained.The mechanism of combustion and detonation reaction of micron tungsten powder was revealed and the physical picture of combustion and detonation reaction of tungsten powder was established.The main work and conclusions of this paper are as follows:(1)The explosion intensity parameters of micron tungsten powder were obtained.It is found that the maximum combustible particle size of tungsten powder is between 2～5 μm,Moreover,the maximum explosive pressure of tungsten powder increases firstly,and then decreases with the increase of concentration.The optimal explosion concentration is 3000 g/m3,the maximum explosion pressure is 0.46 MPa,the highest pressure is 16 MPa/s,and the flame propagation velocity approaches 4 m/s.The explosion index of tungsten powder is 4.346 MPa·m/s,and the explosion danger level is Stl,it is weakly explosive.(2)The CFD-DPM three-dimensional numerical model describing the flow field before explosion is established.Dust Deposition of Tungsten Powder in 20 L Ball Explosion Experiment was simulated by numerical simulation,and the velocity distribution,turbulent kinetic energy and pressure at different time points were obtained,and the results were compared with those of experiments.(3)The effects of different initial conditions on the ignition and detonation of pure tungsten powder are analyzed.The results show that the maximum explosive pressure is in direct proportion to the initial pressure within the range of 0.06 MPa to 0.1 MPa.The main reason is that the concentration of the accelerant is linear with the initial pressure,but the maximal increase rate is not sensitive.Firstly,the delay time of ignition is increased,and then it is reduced to explosion overpressure.The optimum ignition delay time is about 80 ms.It is found that the ignition energy has no obvious effect on the maximum explosion pressure of tungsten powder,but there is a minimum ignition energy to ignite the tungsten powder explosion.(4)The influence of hydrogen and water vapor on the ignition reaction of tungsten powder was explored.The results show that the maximum explosion pressure of H2 is firstly increased,then decreased,and then decreased with the increase of the dust.Researchers found that adding steam can reduce the intensity of combustion and Explosion,and play a certain role in flame suppression and explosion suppression.The results of the study can provide important theory instruction and data support for dust explosion hazard assessment of fusion reactor and the design of explosion suppression system.In addition,the method can also provide references for the study of combustible gas/dust explosion in traditional industrial systems such as food and metallurgy.Therefore,the method has important scientific significance and engineering value.更多还原