Maximum Temperature in Bifurcated Tunnel Based on Synergistic Effect of Longitudinal Ventilation and Air Curtain
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摘要:
为研究城市分岔隧道中纵向通风和空气幕的协同作用对控制隧道火灾烟气的影响，基于1:10小尺寸分岔隧道火灾实验，综合考虑纵向通风、空气幕射流速度、角度和厚度等变量，对纵向通风和空气幕协同作用下的分岔隧道沿程温度和最高温度进行分析. 首先，通过57组小尺寸隧道火灾实验，分析空气幕的防烟隔热效应；然后，根据隧道火灾顶棚最大温升的无量纲经验相关公式，在固定热释放速率47.9 kW下，构建空气幕和纵向通风协同作用下的最高温升模型；最后，将不同工况下的最大温升实验值与所构建的最高温升理论模型预测值进行对比验证. 研究表明：空气幕可以有效地帮助纵向通风降低主隧道温度，最高可降低420 ℃，同时可有效防止烟气进入分岔隧道；而当空气幕射流速度较小时，纵向风速的增加，能有效防止烟气在分岔口积聚，提高空气幕对烟气的阻隔效率，隧道分岔点处烟气温度最高可降低170 ℃；最高温升理论模型与实验结果之间的误差小于10%.
Abstract:To investigate the effect of synergistic longitudinal ventilation and air curtain on the control of tunnel fire smoke in urban bifurcated tunnels, the 1:10 small-sized bifurcated tunnel fire experiments were conducted, and the along-travel and maximum temperatures of bifurcated tunnels under the synergistic effect of longitudinal ventilation and air curtains were analyzed by taking into account the variables of longitudinal ventilation, jet velocity, angle, and thickness of air curtain. Firstly, the smoke and heat insulation effect of the air curtain was analyzed through 57 sets of small-sized tunnel fire experiments. Then, based on the dimensionless empirical correlation formula for the maximum temperature rise of the ceiling in a tunnel fire, a model of the maximum temperature rise under the synergistic effect of air curtain and longitudinal ventilation was constructed at a fixed heat release rate of 47.9 kW. Finally, the experimental values of the maximum temperature rise under different working conditions were compared with the predicted values of the theoretical models of the maximum temperature rise. The results show that an air curtain can effectively help longitudinal ventilation reduce the temperature in the main tunnel by up to 420 ℃ while effectively preventing smoke from entering the bifurcated tunnels. When the jet velocity of the air curtain is small, the increase in longitudinal wind speed can effectively prevent the accumulation of smoke in the bifurcation and improve the insulation efficiency of the air curtain on the smoke. In addition, the temperature of the smoke at the tunnel bifurcation point can be reduced by up to 170 ℃. The constructed theoretical model of the maximum temperature rise is compared with the experimental results, and the error between them is less than 10%.
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图 1 城市隧道分岔段火灾实验平台
Figure 1. Experimental platform for fires in urban bifurcated tunnels
图 3 不同纵向通风下主隧道温度场分布
Figure 3. Temperature field distribution in main tunnel with different longitudinal ventilation
图 4 不同纵向通风下分岔隧道温度分布
Figure 4. Temperature distribution in bifurcated tunnel with different longitudinal ventilation
图 5 不同空气幕射流速度下$ v^{2} / (g H) $与$ \Delta T_{\max } / T_{\infty} $之间的关系
Figure 5. Relationship between $ v^{2} / (g H) $ and $ \Delta T_{\max } / T_{\infty} $at different jet velocities of air curtain
图 6 $ {v_{{\mathrm{air}}}}/{(gH)^{1/2}} $与系数m和n之间的关系
Figure 6. Relationship between$ {v_{{\mathrm{air}}}}/{(gH)^{1/2}} $and coefficients m and n
图 7 不同空气幕射流速度下无量纲预测与实验的最大温升对比
Figure 7. Comparison of dimensionless predicted and experimental maximum temperature rise at different jet velocities of air curtain
图 8 不同空气幕角度下$ {{{v^2}} \mathord{\left/ {\vphantom {{{v^2}} {(gH)}}} \right. } {(gH)}} $与$ {{\Delta {T_{\max }}} \mathord{\left/ {\vphantom {{\Delta {T_{\max }}} {{T_\infty }}}} \right. } {{T_\infty }}} $的关系
Figure 8. Relationship between $ v^{2} / ({gH}) $and $ \Delta T_{\max } / T_{\infty} $at different angles of air curtain
图 10 不同空气幕角度下无量纲预测与实验的最大温升对比
Figure 10. Comparison of dimensionless predicted and experimental maximum temperature rise at different angles of air curtain
图 11 不同空气幕厚度下$ v/{(gH)^{1/2}} $与$ {{\Delta {T_{\max }}} \mathord{\left/ {\vphantom {{\Delta {T_{\max }}} {{T_\infty }}}} \right. } {{T_\infty }}} $之间的关系
Figure 11. Relationship between $ v/{(gH)^{1/2}} $ and $ \Delta T_{\max } / T_{\infty} $at different angles of air curtain
图 12 $ T/H $与系数a、b和c之间的关系
Figure 12. Relationship between T/H and coefficients a, b, and c
图 13 不同空气幕喷射宽度下无量纲预测与实验的最大温升对比
Figure 13. Comparison of dimensionless predicted and experimental maximum temperature rise at different jet widths of air curtain
表 1 实验工况表
Table 1. Experimental conditions
工况 HRR/kW 纵向通风/（m•s−1） 空气幕风速/（m•s−1） 角度/（°） 厚度/m 1～15 15.9，47.9，77.7 0.4，0.8，1.2，1.6，2.0 1.0 0 0.15 16～33 47.9 0.4，0.8，1.2 1.5，2.0，2.5，3.0，3.5，4.0 0 0.15 34～51 47.9 0.4，0.8，1.2 3.5 −45，−30，−15，15，30，45 0.15 52～57 47.9 0.4，0.8，1.2 3.5 30 0.05，0.10 
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