Experimental study on mitigation effects of water mist on blast wave
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摘要: 为了探究水雾特性与爆炸载荷衰减效果之间的关系,在爆炸驱动的激波管内两种不同特性的水雾环境下进行了不同强度的爆炸实验,并评估了两种水雾对爆炸冲击波超压和比冲量的衰减效果。实验结果表明:喷雾区域内的压力分为两个上升阶段,第一个阶段为透射冲击波的压力,第二个阶段为液滴二次雾化和弛豫过程导致的压力上升;冲击波掠过的喷雾区域越长,水雾对压力峰值和比冲量的衰减效果越好;冲击波强度的增加将削弱水雾对爆炸载荷的衰减效果;Sauter平均直径为136.04 μm、体积分数为1.72×10−3的水雾使压力峰值衰减了34.2%~60.9%,使比冲量衰减了9%到54%;Sauter平均直径为255.34 μm、体积分数为3.43×10−3的水雾使压力峰值衰减了48.4%~78.6%,使比冲量衰减了14%~66%;冲击波压力峰值的衰减率随着冲击波-雾滴之间的比例交换面积增加而线性减少。Abstract: To examine the mitigation characterisitics of blast wave in water mist, a comprehensive series of blast experiments were carried out utilizing a blast-driven shock tube with a 4 m length and 180 mm square inner cross-section. The blast wave was generated by detonating trinitrotoluene charges with masses of 7, 10 and 13 g within the shock tube. Five pressure gauges were installed to measure blast wave pressure within the spray region. In order to create varying water mist properties, a spray system was employed, which covered a distance of 3 m within the experimental setup. Droplet size and distribution were measured using a laser light scattering analyzer. The mitigation effect of water mist with two distinct properties on blast overpressure and impulse was evaluated. Results indicated that the pressure in the spray region raised in two stages. The first stage corresponded to the pressure associated with the transmitted shock wave, while the second stage was attributed to the secondary atomization and relaxation processes of the droplets. The longer the spray region traversed by the blast wave, the greater the mitigation effect on peak overpressure and impulse. Increased shock wave intensity diminished the mitigation effect of water mist on blast loads. Specifically, when water mist with a Sauter mean diameter of 136.04 μm and a volume fraction of 1.72×10−3 was employed, peak pressure values experienced a reduction ranging from 34.2% to 60.9%, while impulse values were reduced by 9% to 54%. On the other hand, when water mist with a Sauter mean diameter of 255.34 μm and a volume fraction of 3.43×10−3 was used, peak pressure values witnessed a reduction ranging from 48.4% to 78.6%, and impulse values were reduced by 14% to 66%. The mitigation coefficient of peak overpressure decreased linearly with increased scaled exchange surface area between blast wave and droplets.
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Key words:
- shock wave /
- water mist /
- blast mitigation /
- overpressure /
- impulse
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表 1 喷头的参数
Table 1. Nozzle parameters
喷头 Q/(L·min-1) D/mm θ/(°) d0/μm A 0.9 1.8 60 136.04 B 4 2.8 120 255.34 注:Q为喷雾流量,D为喷头出口直径,θ为喷雾角度,d0为水雾液滴的Sauter直径. 表 2 实验工况
Table 2. Test conditions
工况 TNT质量/g 喷嘴 喷雾时间/s 7-N 7 无 0 10-N 10 无 0 13-N 13 无 0 7-A 7 喷头A 5 10-A 10 喷头A 5 13-A 13 喷头A 5 7-B 7 喷头B 5 10-B 10 喷头B 5 13-B 13 喷头B 5 表 3 所有试验工况中每个测点的正压持续时间
$t_+ $ 及其相对变化率$K_{\rm{t}} $ Table 3. Positive pressure duration (t+) and its relative change ratio (Kt) obtained witheach pressure gauge under all test conditions
工况 t+1/ms Kt1/% t+2/ms Kt2/% t+3/ms Kt3/% t+4/ms Kt4/% t+5/ms Kt5/% 7-N 7.5 − 6.7 − 5.8 − 5.3 − 3.8 − 10-N 7.2 − 6.2 − 5.8 − 5.1 − 3.6 − 13-N 6.2 − 5.8 − 5.6 − 5.0 − 3.4 − 7-A 7.8 4 7.1 6 6.4 10 6.8 28 4.6 21 10-A 7.8 8 6.5 5 7.2 24 6.4 25 4.1 14 13-A 8.2 32 7.4 28 6.9 23 6.1 22 4.2 24 7-B 10.1 35 9.7 45 9.3 60 7.3 38 4.7 24 10-B 10.2 42 9.4 52 8.4 45 7.3 43 4.6 28 13-B 10.0 61 9.0 55 8.5 52 7.2 44 4.5 32 表 4 不同测点处的最大比冲量
$I $ 及其相对变化率$K_{\rm{i}} $ Table 4. Maximum impulse (I) and its relative change ratio (Ki) obtained with each pressure gauge
工况 I1/(Pa·ms) Ki1/% I2/(Pa·ms) Ki2/% I3/(Pa·ms) Ki3/% I4/(Pa·ms) Ki4/% I5/(Pa·ms) Ki5/% 7-N 944 − 830 − 735 − 603 − 380 − 10-N 950 − 860 − 769 − 743 − 494 − 13-N 924 − 900 − 966 − 782 − 581 − 7-A 568 −40 490 −41 417 −43 277 −54 184 −52 10-A 615 −35 570 −34 561 −27 455 −39 242 −51 13-A 840 −9 790 −12 727 −25 650 −17 320 −45 7-B 551 −42 520 −37 552 −25 266 −56 131 −66 10-B 765 −19 690 −20 639 −17 380 −49 171 −65 13-B 796 −14 660 −27 552 −43 395 −49 217 −63 -
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