|
|
|
| Study on the Velocity Measurement and Dynamic Characteristics of Laser-Sustained Plasma Flow Field Based on Schlieren Method |
| Wang Pengyu1, Li Jie1, Ma Xiao1, Cheng Zhiwen2, Cheng Liang2, Xiong Qing1 |
1. School of Electrical Engineering Chongqing University Chongqing 400044 China;
2. Shenzhen Xinkailai Industrial Machinery Co. Ltd Shenzhen 518116 China |
|
|
|
Abstract Laser-sustained plasma (LSP) is an advanced plasma radiation source characterized by high brightness and a broad spectrum, offering significant application value in fields such as semiconductor wafer defect detection. However, its stability is affected by self-excited oscillations caused by thermal convection, making the dynamic behavior of its flow field a key point of interest. In this paper, the schlieren method is used to visualize the LSP flow field. Through image processing techniques such as the optical flow method, the two-dimensional velocity distribution of the flow field and the variation of the oscillation period with laser input power are obtained. Additionally, numerical simulations of the flow field are conducted using COMSOL, providing mutual validation with the experimental results.
In this study, the LSP itself is utilized as a point light source, and by leveraging the advantages of a reflective schlieren system, a schlieren setup consisting of nine components is designed. After initiating the LSP, a high-speed camera is used to record 1 000 schlieren images within one second. The laser power is adjusted proportionally to obtain six sets of schlieren images under different power levels. The captured schlieren images clearly show periodic “heat bubble” rise near the plasma region, successfully visualizing the internal flow field of the LSP. Based on the schlieren images obtained at different power levels, Fourier transform is first applied to measure the LSP oscillation frequency. The results indicate that the oscillation frequency decreases as the laser power increases. Subsequently, the optical flow method is used to measure the two-dimensional velocity distribution of the schlieren images under different power levels.
Based on the experimental results, a heat source was configured according to the LSP dimensions observed in the schlieren images, and a thermo-flow coupled model of the LSP was developed using COMSOL simulations. This model provided two-dimensional dynamic distributions of density, temperature, and velocity. Analysis of the simulation results revealed periodic oscillations in all parameters, consistent with experimental observations, and identified the toroidal vortex near the plasma region as a key factor likely responsible for the periodic LSP oscillations: when the flow near the LSP core is heated and rises, the resulting vortex draws surrounding gas into the central heating zone, establishing a self-sustained periodic cycle of heating and ascent. Furthermore, by varying input parameters such as the gas medium and pressure in the simulation model, the oscillation frequency of the LSP under different operational conditions was obtained.
The following conclusions can be drawn from the experimental and simulation analysis: (1) The combination of the schlieren method and the optical flow method enables effective visualization of the LSP flow field oscillation and measurement of key parameters such as oscillation frequency and velocity. (2) The mechanism behind the periodic LSP oscillation is closely related to the formation and evolution of the vortex. The vortex periodically draws surrounding gas into the central heating area, creating a recurring cycle of heating and ascent. Furthermore, the oscillation frequency v can be estimated by an empirical formula related to the equilibrium radius r? of the plume bubble. (3) The oscillation frequency of the LSP can be reduced by increasing the input laser power, using gas media with lower molecular weight, or reducing the ambient pressure.
These findings are of great significance for suppressing LSP oscillations and advancing the development of high-brightness, broadband laser plasma radiation sources based on LSP technology.
|
|
Received: 10 August 2025
|
|
|
|
|
|
[1] 刘定新, 张基珅, 王子丰, 等. 等离子体活化介质技术及其生物医学应用[J]. 电工技术学报, 2024, 39(12): 3855-3868.
Liu Dingxin, Zhang Jishen, Wang Zifeng, et al.Plasma-activated media technology and its biomedical applications[J]. Transactions of China Electrotech- nical Society, 2024, 39(12): 3855-3868.
[2] 陈星宇, 陆晨, 熊紫兰. 表面微放电等离子体特性参数计算及介质片性质的影响[J]. 电工技术学报, 2024, 39(22): 7256-7265.
Chen Xingyu, Lu Chen, Xiong Zilan.Calculation of the characteristic parameters of surface micro- discharge and the effect of dielectric sheet properties[J]. Transactions of China Electrotechnical Society, 2024, 39(22): 7256-7265.
[3] 张国治, 王文祥, 张磊, 等. 介质阻挡放电等离子体处理变压器废弃绝缘油的实验探究[J]. 电工技术学报, 2025, 40(1): 325-334.
Zhang Guozhi, Wang Wenxiang, Zhang Lei, et al.Experimental exploration of dielectric barrier discharge plasma treatment of transformer waste insulating oil[J]. Transactions of China Electrotechnical Society, 2025, 40(1): 325-334.
[4] Raǐzer Y P.Subsonic propagation of a light spark and threshold conditions for the maintenance of plasma by radiation[J]. Soviet Journal of Experimental and Theoretical Physics, 1970, 31: 1148.
[5] Generalov N A, Zimakov V P, Kozlov G I, et al.Continuous optical discharge[J]. Soviet Journal of Experimental and Theoretical Physics Letters, 1970, 11: 302.
[6] Hu Yanfei, Wang Xinbing, Zuo Duluo.Research of continuous fiber laser sustained Xe plasma[J]. Vacuum, 2022, 203: 111229.
[7] Rudoy I G, Solovyov N G, Soroka A M, et al.Xenon plasma sustained by pulse-periodic laser radiation[J]. Plasma Physics Reports, 2015, 41(10): 858-861.
[8] Liu Jinbao, Zhang Dongheyu, Fu Yangyang.Formation and evolution of multiple-core structures in laser-sustained plasmas[J]. New Journal of Physics, 2023, 25(12): 122001.
[9] 张东荷雨, 刘金宝, 付洋洋. 激光维持等离子体多物理场耦合模型与仿真[J]. 物理学报, 2024, 73(2): 172-185.
Zhang Dongheyu, Liu Jinbao, Fu Yangyang.Multiphysics modeling and simulations of laser- sustained plasmas[J]. Acta Physica Sinica, 2024, 73(2): 172-185.
[10] Lavrentyev S Y, Solovyov N G, Shemyakin A N, et al.Buoyancy driven convection instability and related pulsing of continuous optical discharges[J]. Journal of Physics: Conference Series, 2019, 1394(1): 012012.
[11] Zimakov V P, Lavrentyev S Y, Solovyov N G, et al.Spatial and temporal instabilities of optical discharges[J]. Fluid Dynamics, 2022, 57(1): S84-S96.
[12] Kotov M A, Lavrentyev S Y, Shemyakin A N, et al.Oscillations of convective flow around a continuous optical discharge in high-pressure xenon[J]. Plasma Sources Science and Technology, 2022, 31(12): 124002.
[13] Kotov M A, Lavrentyev S Y, Solovyov N G, et al.Dynamics of laser plasma convective plume in high pressure xenon[J]. Journal of Physics: Conference Series, 2020, 1675(1): 012073.
[14] Kotov M A, Osipenko K Y, Solovyov N G, et al.Visualization of an optical discharge behavior in the combined mode of sustaining[J]. Fluid Dynamics, 2023, 58(8): 1564-1567.
[15] 朱海军, 王倩, 梅笑寒, 等. 基于高速纹影/阴影成像的流场测速技术研究进展[J]. 实验流体力学, 2022, 36(2): 49-73.
Zhu Haijun, Wang Qian, Mei Xiaohan, et al.A review on flow field velocimetry based on high-speed schlieren/shadowgraph systems[J]. Journal of Experiments in Fluid Mechanics, 2022, 36(2): 49-73.
[16] 李佐光, 张展, 魏绍清, 等. REBCO高温超导多芯带材的制备技术及性能研究进展[J]. 电工技术学报, 2024, 39(21): 6591-6603.
Li Zuoguang, Zhang Zhan, Wei Shaoqing, et al.Research progress on fabrication technology and properties of REBCO high temperature superconducting multifilamentary tape[J]. Transactions of China Electrotechnical Society, 2024, 39(21): 6591-6603.
[17] 刘洋, 章子潇, 赵贤根, 等. 进气流量对滑动电弧放电分解CO2的瞬态电-光-热特性和转化性能的影响[J]. 电工技术学报, 2024, 39(23): 7616-7627.
Liu Yang, Zhang Zixiao, Zhao Xiangen, et al.The effect of inlet flow rate on the transient electrical- optical thermal characteristics and conversion performance of CO2 decomposition in gliding arc discharges[J]. Transactions of China Electrotechnical Society, 2024, 39(23): 7616-7627.
[18] Toepler A J I. Beobachtungen Nach der Schlieren Methode[M]. Leipzig: W. Engelmann, 1906.
[19] 刘绍勇, 王纪儒, 孙昊, 等. 光学测试平台在气体电弧测试中的应用研究[J]. 高压电器, 2024, 60(9): 163-170.
Liu Shaoyong, Wang Jiru, Sun Hao, et al.Research on the application of optical test platform in gas arc test[J]. High Voltage Apparatus, 2024, 60(9): 163-170.
[20] Horn B K P, Schunck B G. Determining optical flow[J]. Artificial Intelligence, 1981, 17(1-3): 185-203.
[21] 孙福利, 马骁, 杨琦, 等. 激光维持高气压氙气等离子体的时空动态光谱诊断[J/OL]. 重庆大学学报, 2025: 1-12. (2025-05-15)[2025-08-10]. https://kns.cnki.net/KCMS/detail/detail.aspx?filename=FIVE20250514001&dbname=CJFD&dbcode=CJFQ.
Sun Fuli, Ma Xiao, Yang Qi, et al. Spatio-temporal dynamic spectral diagnostics of laser-sustained high- pressure xenon plasma[J/OL]. Journal of Chongqing University, 2025: 1-12. (2025-05-15)[2025-08-10]. https://kns.cnki.net/KCMS/detail/detail.aspx?filename=FIVE20250514001&dbname=CJFD&dbcode=CJFQ.
[22] Zhang Dongheyu, Liu Jinbao, Fu Yangyang.Power- absorption mechanism and coupling effects in dual- wavelength laser-sustained plasma[J]. Physical Review Applied, 2025, 23(5): 054083.
[23] Murphy A B, Tam E.Thermodynamic properties and transport coefficients of arc lamp plasmas: argon, krypton and xenon[J]. Journal of Physics D: Applied Physics, 2014, 47(29): 295202.
[24] 师肇江, 呼和, 杨世超, 等. 激光维持等离子体中的对流羽流振荡及其抑制方法[J]. 中国激光, 2025, 52(6): 0601004.
Shi Zhaojiang, Hu He, Yang Shichao, et al.Convective plume pulsation in laser-sustained plasma and its inhibition[J]. Chinese Journal of Lasers, 2025, 52(6): 0601004.
[25] 葛逸飞, 李森, 魏小林. 利用相空间重构方法分析层流扩散火焰燃烧不稳定现象[J]. 工程热物理学报, 2020, 41(6): 1550-1555.
Ge Yifei, Li Sen, Wei Xiaolin.An analysis of laminar co-flow diffusion flame instability based on phase space reconstruction method[J]. Journal of Engineering Thermophysics, 2020, 41(6): 1550-1555.
[26] Xia Xi, Zhang Peng.A vortex-dynamical scaling theory for flickering buoyant diffusion flames[J]. Journal of Fluid Mechanics, 2018, 855: 1156-1169. |
|
|
|
2026, Vol. 41 
