Effects of flat obstacle channel shapes on characteristics of gasoline-air explosion

doi:10.11949/0438-1157.20191320

Abstract

Abstract:

To study the influence of the shape of flat obstacle channel on the characteristics of gasoline-air explosion, a comparison experiment was performed under three initial gasoline vapor concentration conditions of 1.3% (low), 1.7% (medium), and 2.1% (high). The results show that: the shape of obstacle channel has little effect on the evolution of overpressure time series curve of gasoline-air explosion. The effect of obstacle channel shape on the peak value of maximum overpressure, the maximum rate of pressure rise and the average rate of pressure rise is increased in the order of“trapezium—circular—triangle—square—rectangle”,“trapezium—circular—triangle—square—rectangle”and“trapezium—circular—square—triangle—rectangle”, respectively. The shape of the obstacle channel has little effect on the upstream flame shape of the obstacle, but the rectangular channel has the most significant effect on the turbulence characteristics of the downstream flame of the obstacle, followed by the square, trapezoid, triangle and circle, respectively. The effect degree of obstacle channel shape on the maximum flame propagation distance and average flame propagation velocity under the initial gasoline vapor concentration of 1.7%, which is close to the equivalence ratio, is smaller than that of low concentration (1.3%) and high concentration condition (2.1%), and the influence degree of circular channel plate obstacle is the smallest, while that of rectangular and square channel is relatively larger.

Key words: flat obstacle channel shape, gasoline-air explosion, explosion overpressure, overpressure rise rate, flame propagation

摘要：

为研究平板障碍物通道形状对油气爆炸特性的影响，进行了1.3%（低）、1.7%（中）、2.1%（高）三种初始油气浓度工况下对比实验。研究表明：障碍物通道形状对油气爆炸超压随时间变化规律的影响较小；障碍物通道形状对最大爆炸超压峰值、最大升压速率、平均升压速率的影响程度分别按照通道形状为“梯形—圆形—三角形—正方形—矩形”、“梯形—圆形—三角形—正方形—矩形”、“梯形—圆形—正方形—三角形—矩形”的顺序递增；障碍物通道形状对障碍物上游火焰形态基本没影响，但矩形通道障碍物对障碍物下游火焰的湍流特性影响最显著，其次为正方形、梯形、三角形和圆形；初始油气浓度接近当量比时（约为1.7%），障碍物通道形状对最大火焰传播距离和平均火焰传播速度的影响要小于低浓度(1.3%)和高浓度(2.1%)工况，且圆形通道平板障碍物的影响程度最小，矩形和正方形通道的影响程度相对较大。

关键词: 障碍物通道形状, 油气爆炸, 爆炸超压, 升压速率, 火焰传播

CLC Number:

X 932

Guoqing LI, Yang DU, Jie BAI, Jun WU, Mengyuan LI, Xiaoshu WU, Liang ZHU. Effects of flat obstacle channel shapes on characteristics of gasoline-air explosion[J]. CIESC Journal, 2020, 71(4): 1912-1921.

李国庆, 杜扬, 白洁, 武军, 李孟源, 吴晓澍, 朱亮. 平板障碍物通道形状对油气爆炸传播特性影响[J]. 化工学报, 2020, 71(4): 1912-1921.

Figures/Tables 14

Fig.1 Schematic diagram of experimental setup

Fig.2 Diagram of main experimental platform(vertical view)

Fig.3 Five kinds of flat obstacles with different channel shapes(thickness: 3 mm)

Table 1 Size of obstacle channel

Obstacle channel shape	Size of obstacle channel/mm	Area of obstacle channel/mm²
triangle	b=80	2771
trapezium	a₃=90,a₄=39,h=44	2838
circular	r=30	2827
rectangle	a₁=80,a₂=35.3	2824
square	a=53	2809

Fig.4 Overpressure vs time under five kinds of flat obstacles with different channel shapes

Fig.5 Effects of five kinds of flat obstacles with different channel shapes on the overpressure peaks

Fig.6 Effects of five kinds of flat obstacles with different channel shapes on time to reach maximum overpressure peaks

Table 2 Contribution rate of obstacles with different channel shapes to maximum overpressure peak value of gasoline-air explosion under three initial gasoline vapor concentration conditions

Shape	Φ			Φ_ave
Shape	φ=1.3%	φ=1.7%	φ=2.1%	Φ_ave
triangle	-18.70%	8.90%	6.60%	-1.00%
trapezium	-15.20%	-25.50%	-22.50%	-21.10%
circular	-6.60%	-24.70%	5.70%	-8.50%
rectangle	36.50%	28.20%	17.60%	27.40%
square	4.00%	13.10%	-7.40%	3.20%

Fig.7 Overpressure rise rate vs time under five kinds of flat obstacles with different channel shapes

Table 3 Maximum overpressure rise rate and average overpressure rise rate of gasoline-air explosions under various conditions

φ/%	(dp/dt)_max/(MPa/s)					(dp/dt)_ave/(MPa/s)
φ/%	Triangle	Trapezium	Circular	Rectangle	Square	Triangle	Trapezium	Circular	Rectangle	Square
1.3	16.5	19.3	24.9	40.7	27.1	1	1.1	1.2	1.7	1.3
1.7	92.4	56.7	76.5	119.3	95.8	4.7	3.1	3.2	5.5	5
2.1	64.7	37.4	56.1	72.5	53.9	2.7	1.6	2.4	2.7	1.8

Table 4 Contribution rates of maximum overpressure rise rate and average overpressure rise rate of gasoline-air explosions under various conditions

φ	(dp/dt)_max					(dp/dt)_ave
φ	Triangle	Trapezium	Circular	Rectangle	Square	Triangle	Trapezium	Circular	Rectangle	Square
1.3%	-35.8%	-24.9%	-3.1%	58.4%	5.4%	-20.6%	-12.7%	-4.8%	34.9%	3.2%
1.7%	4.9%	-35.6%	-13.2%	35.4%	8.7%	9.3%	-27.9%	-25.6%	27.9%	16.3%
2.1%	13.7%	-34.3%	-1.4%	27.4%	-5.3%	22.7%	-27.3%	9.1%	22.7%	-18.2%
$Θ a v e$	-5.7%	-31.6%	-5.9%	40.4%	2.9%	3.8%	-22.6%	-7.1%	28.5%	0.4%

Table 4 Contribution rates of maximum overpressure rise rate and average overpressure rise rate of gasoline-air explosions under various conditions

φ	(dp/dt)_max					(dp/dt)_ave
φ	Triangle	Trapezium	Circular	Rectangle	Square	Triangle	Trapezium	Circular	Rectangle	Square
1.3%	-35.8%	-24.9%	-3.1%	58.4%	5.4%	-20.6%	-12.7%	-4.8%	34.9%	3.2%
1.7%	4.9%	-35.6%	-13.2%	35.4%	8.7%	9.3%	-27.9%	-25.6%	27.9%	16.3%
2.1%	13.7%	-34.3%	-1.4%	27.4%	-5.3%	22.7%	-27.3%	9.1%	22.7%	-18.2%
$Θ a v e$	-5.7%	-31.6%	-5.9%	40.4%	2.9%	3.8%	-22.6%	-7.1%	28.5%	0.4%

Fig.8 Flame propagation structures under various operating conditions with initial gasoline vapor concentration of 1.7%

Fig.9 Images of maximum flame propagation distance under three initial gasoline vapor concentrations

Table 5 Maximum flame propagation distance and average flame propagation velocity under different conditions

φ/%	(L_f)_max/m					(S_f)_ave/(m/s)
φ/%	Triangle	Trapezium	Circular	Rectangle	Square	Triangle	Trapezium	Circular	Rectangle	Square
1.3	1.35	1.29	1.28	1.40	1.41	26.47	28.04	26.12	29.79	28.78
1.7	1.58	1.54	1.48	1.55	1.53	43.89	43.06	42.29	44.29	43.71
2.1	1.47	1.45	1.42	1.53	1.51	29.80	26.36	26.79	29.42	26.03

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