Y型合流分岔隧道临界风速计算模型
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摘要
临界风速是Y型合流分岔隧道能否有效抑制烟气侵入分岔支路的重要参数。为确定Y型合流分岔隧道临界风速计算公式,对影响Y型合流分岔隧道临界风速的相关因素进行量纲分析,推导出临界风速与火源热释放率、主分隧道高度比、连拱长度及隧道分岔夹角这4个因素的无量纲函数关系式。通过数值模拟得到临界风速最大的火源位置,并对上述4个影响因素进行了量化分析。结果表明:火源距分岔段隧道洞口15～25 m时临界风速最大;当无量纲火源热释放速率小于0. 3时,隧道临界风速与火源热释放率呈现1/3次方关系,当无量纲火源热释放速率大于0. 3时,隧道临界风速不再随火源热释放速率增加而增加;临界风速与分岔隧道高度比近似成-3/10次方关系,与分岔夹角成-3/40次方关系,而与连拱长度无关。进而得到分岔隧道临界风速的无量纲计算模型,且与数值模拟结果吻合良好。
The given paper intends to make an analysis of all the factors that may affect the critical velocity so as to derive the dimensionless relationship between the critical velocity in a Yshaped combined bifurcation tunnel under the impact of the 4 influential parameters. As is known,the critical velocity in a branch tunnel serves as one of the significant parameters to decide whether the aforementioned Y-shaped combined bifurcation tunnel can help to inhibit the smoke from intrusion via π theorem and/or the other similarity theories,for the problem involves the thermos releasing rate,the primary tunnel height ratio,the tunnel arch length,as well as the tunnel bifurcation angle. Then the paper has proposed a mathematical model for calculating the critical velocity of the Y-shape combined bifurcation tunnel through FDS 6. 1 for numerical simulation. The aforementioned numerical simulation can help to find the maximum velocity likely to be near the fire source through the quantitative analysis of the above4 influential factors. It can also help to show that the critical ventilation velocity can turn to be the greatest in a distance between the fire source and the tunnel entrance being 15-25 meters away from each other. What is more,at the different heat releaserates,there may exist an inverse relationship between the 2 factors. For example,when the heat releasing rate from a dimensionless source is low( Q*< 0. 3),the critical ventilation velocity in the dimensionless state may tend to increase with the increase of the HRR of 1/3 power. However,if the heat releasing rate from a dimensional source were to be greater than 0. 3,the critical ventilation velocity wouldn't be increasing with the increase of HRR; Thus,it is also shown clearly that the critical velocity in a tunnel through-the passage would vary in a ratio of-3/10 power of the height,for-3/40 power of the angle of bifurcation may seem to be almost independent of the arch length.Therefore,fitting the results of the data,it would be possible to obtain the formula of the critical velocity of the tunnel fire with the 4 different dimensionless factors in actuality,with the correlation coefficient being 0. 991 3. Thus,the critical velocity model we have gained proves to be well in accord with the numerical simulation results.
The given paper intends to make an analysis of all the factors that may affect the critical velocity so as to derive the dimensionless relationship between the critical velocity in a Yshaped combined bifurcation tunnel under the impact of the 4 influential parameters. As is known,the critical velocity in a branch tunnel serves as one of the significant parameters to decide whether the aforementioned Y-shaped combined bifurcation tunnel can help to inhibit the smoke from intrusion via π theorem and/or the other similarity theories,for the problem involves the thermos releasing rate,the primary tunnel height ratio,the tunnel arch length,as well as the tunnel bifurcation angle. Then the paper has proposed a mathematical model for calculating the critical velocity of the Y-shape combined bifurcation tunnel through FDS 6. 1 for numerical simulation. The aforementioned numerical simulation can help to find the maximum velocity likely to be near the fire source through the quantitative analysis of the above4 influential factors. It can also help to show that the critical ventilation velocity can turn to be the greatest in a distance between the fire source and the tunnel entrance being 15-25 meters away from each other. What is more,at the different heat releaserates,there may exist an inverse relationship between the 2 factors. For example,when the heat releasing rate from a dimensionless source is low( Q*< 0. 3),the critical ventilation velocity in the dimensionless state may tend to increase with the increase of the HRR of 1/3 power. However,if the heat releasing rate from a dimensional source were to be greater than 0. 3,the critical ventilation velocity wouldn't be increasing with the increase of HRR; Thus,it is also shown clearly that the critical velocity in a tunnel through-the passage would vary in a ratio of-3/10 power of the height,for-3/40 power of the angle of bifurcation may seem to be almost independent of the arch length.Therefore,fitting the results of the data,it would be possible to obtain the formula of the critical velocity of the tunnel fire with the 4 different dimensionless factors in actuality,with the correlation coefficient being 0. 991 3. Thus,the critical velocity model we have gained proves to be well in accord with the numerical simulation results.
引文
[1] MA Weixiang(马尉翔). Study on the spread regularityand control of fire smoke in large scale interchange tunnel(大型互通立交隧道火灾烟气迁移规律及控制研究)[D]. Chengdu:Southwest Jiaotong University,2015.
[2] LEE C K,HWANG C C,SINGER J M,et al. Influenceof passageway fires on ventilation flows[C]//Proc of theSecond International Mine Ventilation Congress. NewYork:American Institute of Mining,Metallurgical,andPetroleum Engineers,Inc.,1979.
[3] OKA Y,ATKINSON G T. Control of smoke flow in tunnelfires[J]. Fire Safety Journal,1995,25(4):305-322.
[4] ATKINSON G T,WU Y. Smoke control in sloping tun-nels[J]. Fire Safety Journal,1996,27(4):335-341.
[5] WENG M C,LU X L,LIU F,et al. Study on the criticalvelocity in a sloping tunnel fire under longitudinal ventila-tion[J]. Applied Thermal Engineering, 2016, 94:422-434.
[6] WU Y,BAKER M Z A. Control of smoke flow in tunnelfires using longitudinal ventilation systems—a study of thecritical velocity[J]. Fire Safety Journal,2000,35(4):363-390.
[7] TSAI K C,LEE Y P,LEE S K. Critical ventilation veloc-ity for tunnel fires occurring near tunnel exits[J]. FireSafety Journal,2011,46(8):556-557.
[8] LI Y Z,INGASON H. Effect of cross section on criticalvelocity in longitudinally ventilated tunnel fires[J]. FireSafety Journal,2017,91(S1):303-311.
[9] JIANG Xuepeng(姜学鹏),ZHANG Jiangao(张剑高),HE Chao(何超). Study on critical wind velocity of crosspassage in railway tunnel[J]. China Railway Science(中国铁道科学),2015,36(4):80-86.
[10] JTG D07—2004 Code for design of rode tunnel(公路隧道设计规范)[S].
[11] ZHU Shi(祝实),HUO Ran(霍然),HU Longhua(胡隆华),et al. Influence of mesh grid and computationaldomain on FDS simulation[J]. Journal of Safety andEnvironment(安全与环境学报), 2008, 8(4):131-135.
[12] HU Longhua(胡隆华). Studies on thermal physics ofsmoke movement in tunnel fires(隧道火源烟气蔓延的热物理特性研究)[D]. Hefei:University of Science andTechnology of China,2006.
[13] LI Y Z,LEI B,INGASON H. Theoretical and experi-mental study of critical velocity for smoke control in atunnel cross-passage[J]. Fire Technology,2013,49(2):435-449.
[2] LEE C K,HWANG C C,SINGER J M,et al. Influenceof passageway fires on ventilation flows[C]//Proc of theSecond International Mine Ventilation Congress. NewYork:American Institute of Mining,Metallurgical,andPetroleum Engineers,Inc.,1979.
[3] OKA Y,ATKINSON G T. Control of smoke flow in tunnelfires[J]. Fire Safety Journal,1995,25(4):305-322.
[4] ATKINSON G T,WU Y. Smoke control in sloping tun-nels[J]. Fire Safety Journal,1996,27(4):335-341.
[5] WENG M C,LU X L,LIU F,et al. Study on the criticalvelocity in a sloping tunnel fire under longitudinal ventila-tion[J]. Applied Thermal Engineering, 2016, 94:422-434.
[6] WU Y,BAKER M Z A. Control of smoke flow in tunnelfires using longitudinal ventilation systems—a study of thecritical velocity[J]. Fire Safety Journal,2000,35(4):363-390.
[7] TSAI K C,LEE Y P,LEE S K. Critical ventilation veloc-ity for tunnel fires occurring near tunnel exits[J]. FireSafety Journal,2011,46(8):556-557.
[8] LI Y Z,INGASON H. Effect of cross section on criticalvelocity in longitudinally ventilated tunnel fires[J]. FireSafety Journal,2017,91(S1):303-311.
[9] JIANG Xuepeng(姜学鹏),ZHANG Jiangao(张剑高),HE Chao(何超). Study on critical wind velocity of crosspassage in railway tunnel[J]. China Railway Science(中国铁道科学),2015,36(4):80-86.
[10] JTG D07—2004 Code for design of rode tunnel(公路隧道设计规范)[S].
[11] ZHU Shi(祝实),HUO Ran(霍然),HU Longhua(胡隆华),et al. Influence of mesh grid and computationaldomain on FDS simulation[J]. Journal of Safety andEnvironment(安全与环境学报), 2008, 8(4):131-135.
[12] HU Longhua(胡隆华). Studies on thermal physics ofsmoke movement in tunnel fires(隧道火源烟气蔓延的热物理特性研究)[D]. Hefei:University of Science andTechnology of China,2006.
[13] LI Y Z,LEI B,INGASON H. Theoretical and experi-mental study of critical velocity for smoke control in atunnel cross-passage[J]. Fire Technology,2013,49(2):435-449.