Influence of explosion venting conditions on the deflagration characteristics of gas-powder two-phase mixture system in pipe
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摘要: 为探究气粉两相混合体系泄爆特性变化规律，以甲烷-硝酸铵为实验介质，利用自行搭建的不锈钢火焰加速管道开展了泄爆口不同静态动作压力（pst）的燃爆实验，着重研究了pst对气粉两相燃爆压力、火焰传播速度和泄爆火焰形态的影响规律。pst由泄爆口阻塞比（θ）和泄爆膜层数（n）决定，θ和n增大的共同作用使pst升高。pst升高将增强管道对气粉和反应产物冲出管外的约束，增大管内流体的黏滞效应，促进管内气粉两相反应，降低未燃气在管外二次爆炸的强度。对爆燃压力进行分析，发现pst从2.97 kPa升高至14.64 kPa时，爆燃压力时程曲线呈含维稳平台的双峰结构。第一压力峰值从5.48 kPa增大至10.20 kPa，维稳时间从6 ms延长至25 ms，第二压力峰值从23.03 kPa减小至9.71 kPa；pst为16.08 和24.12 kPa时，破膜前压力多次叠加反射，致使泄爆膜压力时程曲线呈特殊振荡上升的三峰结构。对火焰传播速度进行分析，发现pst升高使火焰的平均传播速度从161.33 m/s降低至67.99 m/s。对泄爆火焰进行分析，发现当n=2时，θ增大将使泄爆火焰结构由簇状转变为射流状；θ=88.9%时，泄爆火焰呈典型的射流状。θ增大和n增大均使火焰亮度逐渐降低，火焰发光区长度减小，破膜至火焰出现时间间隔和火焰持续时间延长。Abstract: To investigate the variation law of the blasting characteristics of the gas-powder two-phase mixed system, blast experiments with different outlet static action pressures (pst) were carried out in a self-built stainless steel flame acceleration pipeline, and the variation law of pst on two-phase blasting pressure, flame propagation velocity, and blasting flame morphology was emphatically studied. pst is determined by the blasting hole blocking ratio (θ) and the number of blasting film layers (n). The increase of θ and n together increases pst. The increase of pst strengthens the constraint of gas powder and reaction products flowing out of the pipe, increases the viscosity effect of the fluid in the pipe, promotes the reaction of gas powder in the pipe, and reduces the degree of secondary explosion of unfired gas outside the pipe. For the pressure-time interval curve analysis, pst increases from 2.97 kPa to 14.64 kPa, and the pressure time interval curve shows a double peak structure with a keep platform. The first pressure peak increases from 5.48 kPa to 10.20 kPa, the keep time extends from 6 ms to 25 ms, and the second pressure peak decreases from 23.03 kPa to 9.71 kPa. When pst is 16.08 and 24.12 kPa, the pressure before the bursting film is superimposed and reflected many times, resulting in the time-history curve of bursting film pressure showing a special oscillating and rising three-peak structure. In the analysis of flame propagation velocity, the increase of pst decreases the average flame propagation velocity from 161.33 m/s to 67.99 m/s. When n=2, the increase of θ makes the flame structure change from cluster to jet. When θ=88.9%, the blasting flame shows a typical jet shape. The increase of θ and n makes the flame brightness gradually decrease, the length of the flame luminescence zone decreases, the time interval from breaking film to flame emergence and the flame duration increase.
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图 5 θ=0%条件下不同n工况的压力时程曲线
Figure 5. Pressure-time history curves under different working conditions of n at θ=0%
图 6 θ=55.6%条件下不同n工况的压力时程曲线
Figure 6. Pressure-time history curves of different working conditions of n at θ=55.6%
图 7 θ=88.9%条件下不同n工况的压力时程曲线
Figure 7. Pressure-time history curves of different working conditions of n at θ=88.9%
图 8 2.97 kPa≤pst≤14.64 kPa时pp1与pst的关系
Figure 8. Relationship between pp1 and pst when 2.97 kPa≤pst≤14.64 kPa
图 9 各工况火焰传播速度在管道中的变化曲线
Figure 9. Variation curves of flame propagation velocity in the pipeline under different working conditions
图 10 各工况火焰平均传播速度变化趋势
Figure 10. Variation trend of average flame propagation velocity under different conditions
图 11 n=2时，θ=0%、55.6%和88.9%瞬态泄爆火焰结构
Figure 11. Transient burst flame structures under the conditions of n=2 and θ=0%, 55.6%, and 88.9%, respectively
图 12 θ=88.9%条件下，n=1、2和3瞬态泄爆火焰结构
Figure 12. Transient burst flame structures under the conditions of θ=88.9% and n=1, 2, and 3, respectively
表 1 泄爆口径与阻塞比的关系
Table 1. Relationship between blasting aperture and blocking ratio
D/mm SC/cm2 θ/% 120 0 0 80 249.33 55.6 40 400.12 88.9 
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表 2 静态动作压力测试结果
Table 2. Test results of static action pressure
n pst/kPa D=120 mm D=80 mm D=40 mm 1 3.25 5.20 9.16 2 6.36 9.61 18.96 3 9.16 14.62 22.28 4 16.51 19.25 31.82
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表 3 静态动作压力计算模型预测结果
Table 3. Results predicted by static action pressure calculation model
n pst/kPa D=120 mm D=80 mm D=40 mm 1 2.97 4.88 8.04 2 5.94 9.70 16.08 3 8.91 14.64 24.12
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