Correction method for pulse energy density of compression plasma flows
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摘要: 介绍了压缩等离子体流能量密度诊断存在的问题，基于能量的耗散走向分析及热传导计算模型，针对汽化过程对诊断带来的误差，给出了一种基于测量的质量损失，通过表面退行的有限元计算反推损失相同质量所需输入能量的能量密度修正方法，并对能量密度修正进行了评估，通过此方法得到的修正能量密度与实验结果相吻合，但要获得更准确的能量密度，还需针对屏蔽等离子体、反冲应力波等因素进行能量密度修正，或开发出更准确的能量密度诊断方法。Abstract: The problems of energy density diagnosis of compression plasma flows are introduced in this paper. Based on the energy dissipation analysis and the heat conduction calculation model, aiming at the errors caused by vaporization, an energy density correction method based on measured mass loss is proposed, and the input energies required to lose the same mass are deduced through the finite element calculation of surface receding. The energy density correction is evaluated, and the corrected energy density obtained by this method is in good agreement with the experimental results. However, to obtain more accurate energy density, it is necessary to correct the energy density for shielded plasma and recoil stress wave or develop a more accurate energy density diagnosis method.
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图 1 紧凑型磁等离子体压缩机和产生的压缩等离子体流
Figure 1. Compact magnetoplasma compressor and compression plasma flow
图 2 钨在名义能量密度0.3 MJ/m2(脉宽 0.1 ms)的CPF单脉冲辐照下的表面形貌
Figure 2. Surface morphology of tungsten under CPF single pulse irradiation with nominal energy density of 0.3 MJ/m2 (pulse width 0.1 ms)
图 3 用Comsol计算出不同的脉冲能量密度(脉宽 0.1 ms)下表面温度随时间的变化
Figure 3. Variation of surface temperature with time under different pulse energy densities (pulse width 0.1 ms) calculated by Comsol
图 4 无汽化和烧蚀的情况下能量输入与耗散示意图
Figure 4. Schematic diagram of energy input and dissipation without boiling and ablation
图 5 有汽化或者烧蚀的情况下能量输入与耗散示意图
Figure 5. Schematic diagram of energy input and dissipation with vaporization or ablation
图 6 针对汽化过程的能量密度修正方法
Figure 6. Energy density correction method for vaporization process
图 8 钨在入射能量密度1.2 MJ/m2(脉宽 0.1 ms)的CPF单脉冲辐照下深度方向温度分布随时间的变化
Figure 8. Time dependence of temperature distribution in depth direction of tungsten irradiated by CPF single pulse (pulse width 0.1 ms) with input energy density of 1.2 MJ/m2
图 9 计算得到的表面退行量随计算输入能量密度的变化
Figure 9. Variation of the calculated surface degeneration with the input energy density
图 10 实验中质量损失随名义能量密度的变化
Figure 10. Variation of mass loss with nominal energy density in experiment
图 12 能量密度修正的结果评估示意图
Figure 12. Schematic diagram of result evaluation of energy density correction
表 1 钨材料的参数
Table 1. Parameters of tungsten materials
parameter value specific heat capacity of solid state/(J·kg−1·K−1) 144 specific heat capacity of liquid state/(J·kg−1·K−1) 200 solid density/(kg·m−3) 19 350 liquid density/(kg·m−3) 17 600 thermal conductivity/(W·m−1·K−1) variation with temperature melting point Tm/K 3 683.15 boiling point Tb/K 5 933.15 latent Heat LS-L/(kJ·kg−1) 187 latent Heat LL-G/(kJ·kg−1) 4 009 
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表 2 计算模拟得到的不同输入能量密度下的表面退行量
Table 2. Calculated surface degeneration under different input energy densities
$ \varepsilon $/(MJ/m2) $ \Delta x $/μm 0.70 0.00 0.75 0.19 0.80 0.58 0.95 1.94 1.00 2.52 1.05 2.94 1.15 3.98 1.20 4.51
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表 3 实验中质量损失所对应的表面退行量
Table 3. Surface degeneration corresponding to mass loss in the experiment
$ {\varepsilon _n} $/(MJ/m2) $ \Delta m $/mg $ \Delta x' $/μm 0.30 2.80 1.28 0.40 4.45 2.04 0.50 6.10 2.80 0.95 13.54 6.20 1.00 14.36 6.58 1.05 15.19 6.96 1.15 16.84 7.72 1.20 17.67 8.10
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表 4 名义平均能量密度的修正结果
Table 4. Correction results of nominal average energy densities
$ {\varepsilon _n} $/(MJ/m2) $ \varepsilon $/(MJ/m2) 0.3 0.87 0.4 0.95 0.5 1.03 0.95 1.39 1.05 1.46 1.15 1.54 1.20 1.58
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