Development of massively parallel simulation software applied to multi-physics effect with electromagnetic pluses excitation
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摘要: 介绍了自主研发的强电磁脉冲多物理效应并行计算程序JEMS-CDS-System的情况,该程序采用时域有限元方法,基于JAUMIN并行自适应结构网格支撑框架研制,并行效能高,可扩展性强,且支持动态负载平衡。通过算例测试表明,该程序对于键合线的电-热-应力失效过程的最高温度与范式等效应力计算结果与COMSOL软件计算结果吻合较好;SiP功率放大模块的热-应力耦合天河2高性能计算平台并行计算结果表明,该程序在CPU1024核时,具有38.1%并行效率。Abstract: This paper presents the study of massively parallel simulation of multi-physics effect with electromagnetic pluses excitation using a high-performance computing scheme based on JAUMIN. Our in-house time-domain finite element parallel program JEMS-CDS-System is employed for simulating the electro-thermo-mechanical responses of bonding wire arrays and their highest temperatures and von Mises stress are captured and validated in comparison with those of the commercial simulator COMSOL. The thermo-mechanical responses of a part of SiP are simulated and parallel efficiency of our parallel program is assessed by the experiment of its strong parallel scalability. Our parallel program can reach a speedup of 6.095 and strong scalability efficiency of 38.1% on 1024 CPU cores.
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高压纳秒脉冲源在加速器技术、X射线、电磁脉冲效应等多个领域应用广泛[1-4]。在电磁脉冲效应研究中,高压脉冲源是电磁脉冲模拟器的关键组成部分。随着高空核爆电磁脉冲(HEMP)环境标准前沿缩短,需要研制一台快前沿高压脉冲源,与有界波电磁脉冲模拟器配套,建立与IEC61000-2-9标准相近的电磁环境[5],为开展抗HEMP效应研究提供工作环境。采用同轴型结构,电容放电的技术方案的纳秒脉冲源可产生满足百千伏幅值,符合IEC指标要求的纳秒脉冲[6-9]。本文研制的紧凑型自动化纳秒脉冲源采用低电感同轴结构,内置可快速更换的陶瓷电容实现脉宽可调,配套自动化控制系统,输出电压(500 V~50 kV范围内)连续可调。该脉冲源可直接驱动导波天线产生符合IEC标准的电磁脉冲环境,也可用于绝缘材料击穿特性试验等研究。
1. 脉冲源基本原理
输出电压低于100 kV时,电磁脉冲模拟器的高压脉冲源一般采用电容直接放电[6-14]。原理如图1所示:R为负载等效阻抗,C为脉冲源放电回路等效电容,L为脉冲源放电回路等效电感,K为等效开关。tr为脉冲源输出脉冲波形前沿,t50%为脉冲源输出脉冲波形脉宽。当R取120 Ω时,根据IEC61000-2-9标准和式(1),(2),t50%=23 ns,那么C≈278 pF;tr<3 ns,则L<163 nH。
tr=2.2L/R (1) t50%=0.69RC (2) 采用定制陶瓷或膜电容,C的容值比较容易实现。因此电容脉冲源设计的难点在于选取开关K和适合的结构使得脉冲源放电回路电感L满足要求。
2. 脉冲源设计
研制的纳秒脉冲源结构如图2所示。该脉冲源最大直径190 mm,长度295 mm。输出杆一端通过弹簧结构与电容地极板实现电连接,另一端与负载(例如导波天线上极板)相连。脉冲源通过接地金属外筒接地。电容地极板,陶瓷电容,电容高压极板连成一体,电容高压极板固定在电容高压端支撑绝缘子与充电引入绝缘子上,可伸缩电极与电容高压极板构成气体间隙开关。通过更换不同容量的陶瓷电容(或膜电容),并调整输出杆长度与之配合,即可方便调整脉冲源输出脉宽。输出绝缘筒与接地金属外筒构成了一个绝缘腔室,可内充气体绝缘介质提高陶瓷电容的充电电压。
图 2 脉冲源结构Figure 2. Structural design of pulse source(1-output insulated barrel, 2-earthing metal barrel, 3-the output shaft, 4-capacitance ground electrode, 5-ceramic capacitor, 6-capacitor high voltage plate, 7-the insulator of charge leads, 8-the flexible electrode, 9-air cylinder, 10-the insulator supported the high voltage end of the capacitor)脉冲源工作过程如下:首先给绝缘腔室充入预设气压的绝缘气体;其次高压电源通过充电引入绝缘子给陶瓷电容充电;当电压达到预设值时,气缸动作,顶出可伸缩电极,将气体间隙开关短路,电容高压极板接地,此时在负载上产生一个与充电电压极性相反的纳秒前沿高压脉冲。
高压电源应及时断电,并将可伸缩电极推出,间隙开关恢复,准备下一次试验。此工作流程可通过自动控制系统自动运行。
3. 自动控制设计
3.1 控制参数与模块选取
脉冲源控制系统需要监测充电电压、腔体气压两个模拟量,控制腔体充放气,气缸顶出气腔充放气,气缸推进气腔充放气,充电电压升降压控制等几个控制量。可编程逻辑控制器(Programmable Logic Controller,PLC)可以实现上述参数的读取和控制[15]。我们选取了OMRON CPM2A作为脉冲源的控制器,采用光电隔离+组态软件HMIBuilder实现了整个工作流程远程自动化的可视化状态监控。
3.2 程序设计
首先预设腔体气压和充电电压,其次闭合高压电源,启动升压,实时监测充电电压,与预设电压进行比较,当满足充电电压不小于预设电压条件时充电完成,控制气缸顶出气腔充气,将开关电极顶出,高压电源断电,停留2 s后,将气缸推回气腔充气,将开关电极推回。脉冲源的工作流程如图3所示。
该流程通过PLC编程实现自动运行。利用组态软件HMIBuilder实现了可视化状态监控,控制界面如图4所示。在控制界面上点击总启动按钮,即可自动完成上述流程,也可分步手动实现各个流程步骤。
4. 测试结果
将纳秒脉冲源与有界波模拟器导波天线相连,测得导波天线内的典型电场波形如图5所示。前沿2.1 ns,半宽23.6 ns,满足IEC标准中关于前沿和半宽的要求。
间隙开关为气体开关,火花通道电阻和电感对输出脉冲前沿的影响不可忽略,因此通过调节绝缘腔室所充绝缘介质的种类和气压可实现间隙开关的击穿时刻控制,从而实现输出波形的前沿调整。
5. 结 论
本文研制的紧凑型自动化纳秒脉冲源,通过选用更高耐压的电容以及绝缘子,脉冲源可以工作在更高电压。当其他条件不变时,脉冲源输出电压前沿随着充电电压提高而变大。脉冲源外接有界波模拟器导波天线时,可以产生满足IEC标准的电磁环境。脉冲源采用自动化控制方式,通过修改程序设置,即可实现脉冲源自动循环运行,从而实现脉冲源连续自动运行。脉冲源结构简单,元件易更换,远程光电隔离使得其能够在更多场合发挥作用。
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表 1 验证性并行计算相关参数
Table 1. Parallel scalability of the proposed simulation
number of CPU cores time of one step/s speedup efficiency/% 64 1035.0 1× 100 128 718.2 1.265× 72.1 256 486.4 2.128× 53.2 512 259.9 3.982× 49.8 1024 169.8 6.095× 38.1 -
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