【作者】 周学；

【导师】 翟国富；

【作者基本信息】 哈尔滨工业大学 ， 电机与电器， 2011， 博士

【摘要】 航天电磁继电器是可靠性及寿命要求较高的一类密封继电器,其寿命主要取决于分断过程的燃弧特性及电弧对触头的烧蚀特性。本文建立航天热力学环境下银触头在N₂、H₂和He气体中分断电弧的三维磁流体动力学模型,研究不同分断因素对电弧温度、电压、燃弧时间等参数的影响,研究触头烧蚀量与燃弧因素之间的关系,比较各种适用于航天继电器的电弧抑制措施对触头烧蚀量的减小程度。燃弧气体和触头蒸汽混合等离子体的热力学特性和输运系数是研究电弧特性和触头烧蚀特性的前提和基础。针对银蒸汽带来的组份之间碰撞现象,提出了碰撞积分的计算方法。银原子与中性气体组份的碰撞采用Lennard-Jones势描述,碰撞参数采用组合法获得;银原子与气体离子组份之间、银离子与气体中性组份之间的碰撞采用极化势描述。采用Gibbs自由能最小化原理和Chapman-Enskog估计法给出了200K²0000K温度范围内任意比例银蒸汽与N₂、H₂和He气体的混合物平衡组份、热力学特性和输运系数,解决因电弧等离子体热力学特性和输运系数未知而无法进行航天继电器电弧理论分析与建模仿真的问题。建立了航天热力学条件下银触头在N₂中分断电弧的三维磁流体动力学模型。该模型考虑了银触头材料汽化烧蚀、银蒸汽浓度和弧根区域鞘层的等效。提出了热力学环境在航天继电器电弧模型中的描述方法,其中力学环境等效为动量方程的体积力,热学环境通过温度边界条件、压力边界条件及电弧热力学特性和输运系数实现。结合动态层铺法实现了分断过程温度场、电场、磁场以及银蒸汽浓度的耦合求解,研究了不同分断条件下电弧电压、燃弧时间、触头烧蚀量等参数,给出了热力学环境对电弧特性和触头烧蚀特性的影响规律。采用航天继电器分断电弧三维磁流体动力学模型,研究了H₂和He作为燃弧气体、增大气体压强、永磁体磁场吹弧等适用于航天继电器的电弧抑制措施对电弧特性和触头烧蚀特性的影响规律。研究结果表明,H₂可作为航天继电器的理想燃弧气体;增大压强有利于提高电弧电压,减少蒸发烧蚀量,从而提高电寿命;永磁磁场吹弧可缩短燃弧时间、减少触头蒸发烧蚀量。采用H₂熄弧、提高气体压强及磁场吹弧等措施均能有效地加快电弧熄灭,减轻电弧对触头的烧蚀程度。采用高气压H₂作为燃弧气体,并配合小体积永磁体吹弧,可有效提高灭弧性能和触头分断寿命。最后,本文设计了碰撞式触头恒速分断电弧试验系统,利用高速摄像机拍摄了分断过程电弧和银原子浓度分布图像,提出了弧根运动特性自动提取的图像处理算法,研究了电弧的形态及其在磁场作用下的运动特性。实验研究了不同电流、分断速度、外加磁场等因素对电弧特性和触头烧蚀特性的影响规律,为理论分析和仿真研究提供实验依据。最终通过电弧电压、燃弧时间和磁场作用下电弧运动特性的测试结果证明所建电弧模型的正确性。更多还原

【Abstract】 Aerospace relay is a hermetically sealed relay with high requirements on life and reliability, and its life depends greatly on electrical arc characteristics and contacts erosion rate during the opening process. A three-dimensional Magneto Hydrodynamic (MHD) model of electrical arc with the existence of required thermal and dynamic environment in aerospace equipments was proposed. The influence of opening conditions on temperature, voltage, arc duration and silver contact erosion of opening arc in nitrogen, hydrogen and helium gases was investigated. Comparison was also made on the erosion mass under different extinguishing methods usable in aerospace relay. The results of this dissertation will provide theoretical basis for designing a long life aerospace relay in future.Thermal dynamic properties and transport coefficients of plasmas formed by gas and contact vapor are preconditions for studying arc characteristics and erosion mass. An empirical approximation method was proposed for calculating the collision integrals between species of silver vapor and species of arcing gases. The Lennard-Jones potential was used to approach interactions between atomic silver and neutral species, and their interaction parameters were obtained through using a combination method. The polarization potential was used to approach interactions between atomic silver and ions produced by gases and between ionized silver and neutral species produced by gases. Finally, minimization of Gibbs free energy and Chapman-Enskog method were used to calculate compositions and thermal physical properties of silver-nitrogen plasmas, silver-hydrogen plasmas and silver-helium plasmas with different silver percentages, in the temperature range of 200 K~20000 K .A three-dimensional MHD model of silver-nitrogen arc was proposed with the thermal and dynamic environments. Silver contact erosion, silver concentration and one-dimensional sheath model were taken into consideration in this model. The modeling method of thermal and dynamic environment was also proposed, where the thermal environment was treated as temperature boundary, pressure boundary and variation in thermal physical properties of arc, and the dynamic environment was treated as body force in the fluid. A dynamic layering method was used to update the calculated meshes during the opening process. The influence of opening factors on arc voltage, arc duration and silver contact erosion was investigated based on this model, and the effect of environments on those arc characteristics was also revealed.Arc extinguishing methods adoptable in aerospace relay were then investigated on the basis of the arc MHD model. The adoptable methods are taking hydrogen and helium as arcing gases, increasing gas pressure, and driving arc by using transverse magnetic fields or radial magnetic fields. It revealed that hydrogen is a promising arcing gas for highest arc voltage and lowest erosion mass, that higher pressure is good for increasing arc voltage and alleviating erosion, and that magnetic fields are also able to shorten the arc duration and alleviating erosion.Finally, an experiment system was realized with the mechanism of collision breaking, which ensured a constant opening velocity. In this system, a high-speed camera was used to take photos of arc imaging and silver concentration during the opening process, and an image processing methods was proposed to extra arc root motion characteristics. Experiments on arc characteristics and erosion mass during the opening process were carried out under different currents, opening velocities and magnetic fields, which proved the validation of simulation results. Good agreements were seen between the simulation arc voltage, arc duration, and arc motion characteristics and their test results, respectively.更多还原