Prediction of natural gas explosion overpressure considering external turbulence
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摘要: 为预先评估外加湍流工况下天然气的爆炸超压峰值，通过揭示外加湍流对天然气爆炸火焰形态、火焰前锋速度和爆炸超压的影响规律，建立了耦合外加湍流的天然气爆炸超压峰值预测模型。结果表明：外加湍流可使火焰加速传播，且随着外加湍流强度的增加，火焰前锋速度逐渐增加；随着外加湍流强度的增加，爆炸超压峰值和最大升压速率逐渐增加；随着压力监测点和点火位置间距的增加，爆炸超压峰值和最大升压速率整体呈减小的变化趋势。外加湍流工况下天然气的爆炸超压预测必须考虑火焰的加速特征，实验测得爆炸超压峰值介于层流火焰模型和湍流火焰模型计算的爆炸超压峰值之间。Abstract: Natural gas is an important energy material for national development, but its hazardous properties lead to frequent explosion accidents. In order to pre-evaluate the maximum overpressure of natural gas explosion under the condition with external turbulence, it is proposed to reveal the mechanism of accelerated propagation of turbulent flame, and to establish a prediction model of natural gas explosion overpressure coupled with external turbulence. To this end, an experimental platform for natural gas explosion under external turbulence was firstly established, and the particle image velocimetry system was used to obtain the intensity of external turbulence. Then, the effects of external turbulence with different turbulent intensities on the flame evolution, flame front velocity and explosion overpressure of natural gas explosion were obtained for the methane-air premixed gas with stoichiometric ratio. Finally, through introducing the folding factors of flame instability-induced folds, flame turbulence-induced folds and external turbulence-induced folds, a theoretical model of predicting maximum explosion overpressure of natural gas explosion by considering external turbulence is established. The results indicated that compared with the condition without external turbulence, the external turbulence can exacerbate the degree of flame surface folds. Without external turbulence, the flame radius increases linearly with time; in the presence of external turbulence, the flame is characterized by self-accelerating propagation. The flame acceleration can be triggered by external turbulence, with the increasing intensity of external turbulence, the flame front velocity increases gradually. Additionally, with the increasing intensity of external turbulence, maximum explosion overpressure and maximum rate of pressure rise continue to increase. With the increasing distance between pressure monitoring point and ignition position, maximum explosion overpressure and maximum rate of pressure rise totally decrease. The flame acceleration must be considered to predict natural gas explosion overpressure under external turbulence. Maximum explosion overpressure measured in the experiments is between the value calculated using laminar flame model and turbulent flame model.
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图 1 外加湍流工况下天然气爆炸实验平台
Figure 1. Experimental platform of natural gas explosion under external turbulence
图 2 外加湍流对天然气爆炸火焰形态演变的影响规律
Figure 2. Effects of external turbulence on flame evolution of natural gas explosion
图 3 外加湍流对天然气爆炸火焰半径和火焰前锋速度的影响规律
Figure 3. Effects of external turbulence on flame radius and flame front velocity of natural gas explosion
图 5 外加湍流对天然气爆炸超压峰值和最大升压速率的影响规律
Figure 5. Effects of external turbulence on the maximum explosion pressure and the maximum rate of pressure rise of natural gas explosion
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