电弧加热等离子发动机射流流动特性研究

发布时间：2018-02-20 18:19

本文关键词： 电弧加热等离子发动机等离子体射流流动特性伏安特性数值模拟　出处：《南京理工大学》2016年硕士论文　论文类型：学位论文

【摘要】：电弧加热等离子发动机在国外已经应用于卫星保持系统,在空间推进系统中有广阔的应用前景。电弧加热等离子发动机利用电弧将工质加热到20000K的高温电离,然后流经拉瓦尔喷管迅速膨胀加速,在这个过程中将工质的内能转化为超音速的等离子射流而形成反推力。本文主要通过理论分析与数值模拟的相结合的方法,对电弧加热等离子发动机射流进行研究,并借助实验手段对发动机阳极喷嘴烧蚀情况进行了初步的探究。(1)本文将三种湍流模型(标准k-e模型、标准k-ω模型、SST k-ω模型)应用于电弧加热等离子射流数值模拟中,并将计算结果与实验结果比较,发现采用标准k-ε模型和标准k-ω模型时与实验结果相差较大,采用SST k-ω模型时与实验结果较吻合。相对标准k-ε模型和标准k-o模型,SST k-ω模型更适合电弧加热等离子发动机射流的数值模拟。(2)针对自主设计的电弧加热等离子发动机,分别从工作电流、工质和阳极结构三个方面,采用数值模拟的方法,讨论其对电弧加热等离子发动机工作特性的影响。研究结果如下：工作电流对等离子体射流流场有较大的影响,电流强度直接决定发动机内的电流密度,从而影响焦耳热,增加电流可以明显增加等离子体温度和速度。同时,对于自主设计的电弧加热等离子发动机,在所研究的电流范围得到上升的伏安特性。由于导电率的差异,不同工质的电弧加热等离子发动机的工作特性差异较大。当工作电流为150A时,三种推进的发动机的弧电压值关系为：UH2UN2UAr,即在相同工作电流下,发动机的功率关系为：PH2PN2PAr。发动机功率的差异也最终影响到温度分布,发动机的温度也出现相同的关系：TH2TN2TAr,发动机中心轴线上速度分布由于受温度的影响从阳极喉部位置开始出现较为明显的差异。相对阳极收缩角α和喉部长度l,阳极喉部直径d对发动机工作特性的影响最大。随着喉部直径d的增加,发动机中心轴线上的电流密度减小,电弧电压随之增加,发动机中心轴线上等离子体的最高温度和最大速度都随之减小。而阳极收缩角α和喉部长度l的变化,对发动机的伏安特性和等离子体射流流场的影响基本可以忽略。(3)通过对电弧加热等离子发动机的改进,提高了冷却效率,有效的防止了阳极的烧蚀,延长阳极喷嘴使用寿命的效果。同时通过实验研究发现：当阳极喉部直径为2mm时,阳极烧蚀主要集中在阳极喉部和扩张段,而喉部直径为4mm时阳极烧蚀主要集中在喷嘴出口周围,且烧蚀量增加。通过本文的研究,为今后电弧加热等离子发动机的数值模拟和发动机的工程应用提供相应的理论基础。
[Abstract]:Arc heated plasma engine has been used in satellite maintenance system abroad and has a wide application prospect in space propulsion system. Arc heating plasma engine uses arc to heat the working fluid to 20000K high temperature ionization. In this process, the internal energy of the working fluid is transformed into supersonic plasma jet to form the reverse thrust. The method of combining theoretical analysis with numerical simulation is used in this paper. In this paper, three turbulence models (standard k-e model, standard k-e model) are studied. The standard k- 蠅 model and SST k- 蠅 model are applied to the numerical simulation of arc heated plasma jet. The results are compared with the experimental results. It is found that the standard k- 蔚 model and the standard k- 蠅 model are different from the experimental results. Compared with the standard k- 蔚 model and the standard k-o model, the SST k- 蠅 model is more suitable for the numerical simulation of the arc heated plasma engine jet than the standard k- 蔚 model and the standard k-o model. From three aspects of working current, working fluid and anode structure, the method of numerical simulation is used. The results are as follows: the working current has great influence on the flow field of the plasma jet, and the current intensity directly determines the current density in the engine, thus affecting the Joule heat. Increasing the current can obviously increase the temperature and velocity of the plasma. At the same time, for the self-designed arc heated plasma engine, the volt-ampere characteristic is increased in the range of the studied current. When the working current is 150A, the arc voltage relation of the three kinds of propulsion engines is: 1: UH2UN2UAr. that is, under the same working current, The power relationship of the engine is: PH2PN2PAr. the difference in engine power also ultimately affects the temperature distribution. The engine temperature also shows the same relation: TH2TN2TAr. the velocity distribution on the center axis of the engine is obviously different from the position of the anode throat due to the influence of temperature. Relative to the anodic shrinkage angle 伪 and throat length l, the anode is different. The laryngeal diameter d has the greatest influence on the engine performance. With the increase of the throat diameter d, The current density on the central axis of the engine decreases, the arc voltage increases, and the maximum temperature and velocity of the plasma on the central axis of the engine decrease, while the anode contraction angle 伪 and the length of the throat l change. The influence on the volt-ampere characteristic of the engine and the flow field of the plasma jet can be neglected. (3) through the improvement of the arc heating plasma engine, the cooling efficiency is improved, and the anode ablation is effectively prevented. The effect of prolonging the service life of anodic nozzles. At the same time, it is found that when the diameter of anodic throat is 2 mm, the anode ablation is mainly concentrated in the anode throat and expansion section. When the throat diameter is 4 mm, the anode ablation is mainly around the nozzle outlet, and the ablation amount is increased. The research in this paper provides a theoretical basis for the numerical simulation of the arc heated plasma engine and the engineering application of the engine in the future.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：V439.2

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