Numerical study of atmospheric pressure He plasma jets with dual-channel inlet under different electrode structures
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摘要: 采用二维轴对称流体模型对单电极结构(不锈钢针管)和双电极结构(不锈钢针管-高压环形电极)下同轴双通道进气的大气压氦气等离子体射流进行了对比研究。研究表明:相比于单电极结构,双电极结构下射流的传播速度明显降低,介质管内尤为严重。同时双电极结构下射流的空间结构也发生了显著变化。在单电极结构下,随射流发展由环形中空结构转变为实心圆盘结构;而在双电极结构下则呈现出实心圆盘结构至环形中空结构再至实心圆盘结构的演化过程,改善了射流空间分布的均匀性。此外,还研究了双电极结构下高压环形电极厚度对射流的影响。研究表明,随环形电极厚度的增加,射流的传播速度进一步降低,射流通道径向收缩,同时环形中空结构的射流内径减小,进而改善了射流径向分布的均匀性。Abstract: An atmospheric pressure helium plasma jet with a coaxial dual-channel inlet under single electrode structure (stainless steel needle tube) and double electrode structure (stainless steel needle tube—high voltage ring electrode) is comparatively studied using a two-dimensional axisymmetric fluid model. The study shows that compared with the single electrode structure, the propagation velocity of the jet decreases significantly under the double electrode structure, and decreases more in the dielectric tube. Meanwhile, the spatial structure of the jet changes significantly under the double electrode structure. Under the single electrode structure, the jet structure changes from a donut-shaped hollow structure to a solid disk-shaped structure with its development; while under the double electrode structure, a transformation process from a solid disk-shaped structure to a donut-shaped hollow structure and then to a solid disk-shaped structure is shown, which improves the uniformity of the jet spatial distribution. The effect of high-voltage ring electrode thickness on jet under the double electrode structure is also investigated. It is shown that as the ring electrode thickness increases, the jet propagation velocity decreases further and the jet channel shrinks radially, and the inner diameter of the jet with the donut-shaped hollow structure decreases, which improves the uniformity of the radial distribution of the jet.
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Key words:
- plasma jet /
- electrode structure /
- coaxial dual-channel inlet /
- jet structure /
- radial distribution
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图 6 单电极和双电极结构下电离波在管内和管外传播至不同轴向位置时电离头处电场的径向分布
Figure 6. Radial profiles of electric field in the ionization head when the ionization wave propagates to different axial positions inside and outside the tube for single and double electrode structure
Note: solid line: the single electrode structure; dashed line: the double electrode structure
表 1 模拟中采用的化学反应
Table 1. Chemistry reactions used in the simulation
index reaction rate coefficient reference (R1) e + He → e + He BOLSIG+ [21] (R2) e + He → e + He* BOLSIG+ [21] (R3) e + He → 2e + He+ BOLSIG+ [21] (R4) e + N2 → 2e + N2+ BOLSIG+ [21] (R5) e + N2 → e + N2(c3Π) BOLSIG+ [21] (R6) He+ + 2He → He2+ + He 1.1 ×10−43 [m6/s] [22] (R7) He* + 2He → He2* + He 2.0 ×10−46 [m6/s] [22] (R8) 2He2* → He2+ + 2He + e 1.5 ×10−15 [m3/s] [22] (R9) He2* + M → 2He + M 1.0 ×104 [1/s] [22] (R10) 2He* → He2+ + e 1.5 ×10−15 [m3/s] [22] (R11) e + He2+ → He + He* 8.9 ×10−15 (Te/Tg) −1.5 [m3/s] [22] (R12) e + N2+ → N2 4.8 ×10−13 (Te/Tg) −0.5 [m3/s] [22] (R13) He2+ + N2 → N2+ + He2* 1.4 ×10−15 [m3/s] [22] (R14) He* + N2 → He + N2+ + e 5.0 ×10−17 [m3/s] [22] (R15) He2* + N2 → 2He + N2+ + e 3.0 ×10−17 [m3/s] [22] (R16) N2+ + 2N2 → N4+ + N2 1.9 ×10−41 [m6/s] [22] (R17) N2+ + N2 +He → N4+ + He 5.0 ×10−41 [m6/s] [22] (R18) N4+ + N2 → N2+ + 2N2 2.5 ×10−21 [m3/s] [22] (R19) N4+ + He → He + N2 + N2+ 2.5 ×10−21 [m3/s] [22] (R20) e + N4+ → 2N2 2.0 ×10−12 [m3/s] [21] (R21) N2(c3πΠ) → N2 + hv 2.45 ×107 [1/s] [21] Note: In reaction R9, “M” represents background particles He and N2. -
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