空心阴极的发射热特性研究

Investigation on Thermal Characteristics of Thermionic Emission in a Hollow Cathode

关键词:  空心阴极  热电子发射  热特性  逆向迭代  数值计算

Key words:  Hollow cathode  Thermionic emission  Thermal characteristics  Reverse iteration  Numerical simulation

摘要:

空心阴极的发射体在电子发射时会处于动态热平衡状态，这种发射热特性对发射体的利用率和工作寿命有重要意义。为研究空心阴极发射热特性及相关热设计方法，建立一种流-热耦合数值模型，将等离子体流场计算与组件热分布计算进行耦合，并采取一种逆向迭代方法来收敛计算，数值模型在验证试验下的计算误差低于11.3%。在此基础上，对发射体温差的机理以及阴极顶孔径对发射体温差的影响规律进行数值分析，主要结论为：羽状模式下的核心电离区较发散，导致发射体温差较点状模式高出50 K左右；适当增加阴极顶孔径可对发射体温差有降低作用。

Abstract:

A dynamic thermal balance will be established as the emitter performing in the thermionic emission state in the hollow cathode, in which the thermal characteristics exerts a great influence on the utilization and life time of the emitter. In order to study the thermal behavior of the electron emission and the relevant optimizing strategy of the thermal performance, an numerical model was employed to simulate the charged particle transportation coupling with the heat transfer process in the assemblies of the cathode, namely the flow-heat coupling model. In this model, a reverse iteration method was conducted to make the computational solution converged. A measurement test of the temperature of three cathodes has been performed to examine the accuracy of the flow-heat coupling model, and the relative error of this model was no more than 11.3%. Based on those, the physics of temperature difference in emitter and the change law of the temperature difference at different orifice diameters were analyzed numerically. This was because the core ionization region of the plume mode was more diverging than that of spot mode so that the temperature difference of the emitter in plume mode was 50 K more than that of spot mode; an appropriate size of the orifice diameter would decrease the emitter temperature difference for the sake of thermal performance optimization.