高層建筑樓梯間及相連空間內(nèi)煙氣流動(dòng)特性與火行為研究
發(fā)布時(shí)間：2018-08-21 11:03
【摘要】：隨著城市化進(jìn)展的加快和土地資源的日益稀缺,我國高層建筑的數(shù)量和高度得到了快速增長,再加上近年來房價(jià)的飛速上漲和住房需求量的不斷攀升,進(jìn)一步刺激各房地產(chǎn)企業(yè)加快投資和建設(shè)高樓大廈的速度,各地(超)高層建筑如雨后春筍般不斷拔地而起,具有數(shù)量多、高度高、結(jié)構(gòu)復(fù)雜、功能多樣化的特點(diǎn),并且許多建筑已經(jīng)成為城市的標(biāo)志性建筑,同時(shí),高層建筑也是對(duì)施工技術(shù)和安全保障的嚴(yán)峻考驗(yàn),尤其是高層建筑火災(zāi)安全問題備受人們關(guān)注。近年來發(fā)生了許多大型高層建筑火災(zāi)事故,并有愈演愈烈之勢(shì)。高層建筑由于樓層多、結(jié)構(gòu)復(fù)雜、體積大,且煙氣蔓延途徑多,其火災(zāi)危險(xiǎn)性更大,尤其是煙囪效應(yīng)和外界風(fēng)帶來后果尤其嚴(yán)重,因此,研究高層建筑煙氣運(yùn)動(dòng)規(guī)律和火災(zāi)發(fā)展特性具有重要意義。 湍流混合運(yùn)動(dòng)和煙囪效應(yīng)是樓梯間內(nèi)煙氣運(yùn)動(dòng)的兩種主要機(jī)制,兩種運(yùn)動(dòng)機(jī)制分別在火災(zāi)發(fā)展不同階段起主要作用。在第一個(gè)穩(wěn)定階段,樓梯間內(nèi)煙氣主要依靠湍流混合作用向上緩慢的運(yùn)動(dòng)；在第二個(gè)穩(wěn)定階段,樓梯間內(nèi)煙氣主要依靠煙囪效應(yīng)向上快速的運(yùn)動(dòng)。兩個(gè)穩(wěn)定階段的持續(xù)時(shí)間都會(huì)受到火源功率和通風(fēng)口位置的影響。樓梯間內(nèi)煙氣運(yùn)動(dòng)機(jī)制影響其豎向溫度分布。與湍流混合運(yùn)動(dòng)作用階段相比,在煙囪效應(yīng)作用階段,樓梯間煙氣豎向溫度衰減較慢,溫度衰減系數(shù)β值較小。隨著樓梯間通風(fēng)口位置升高和火源功率增大,β值越小,封閉樓梯間的煙氣溫度衰減最快,β值最大。著火層位于高層建筑中間樓層時(shí),著火層上方和下方通風(fēng)口狀態(tài)對(duì)樓梯間內(nèi)豎向溫度分布有較大的影響。 在煙囪效應(yīng)作用下,甲醇和正庚烷池火向樓梯間方向傾斜,本文引入理查森數(shù)Ri分析煙囪效應(yīng)對(duì)火焰傾角的影響。對(duì)于甲醇池火,火焰傾角θ與理查德森數(shù)Ri1呈線性遞增關(guān)系,而對(duì)于正庚烷池火,在煙囪效應(yīng)作用下各工況火焰傾角θ相差不大,其平均值為69.7°,樓梯間通風(fēng)口位置對(duì)正庚烷的火焰傾角θ影響較小。對(duì)于火焰長度和火焰高度,實(shí)驗(yàn)結(jié)果表明在煙囪效應(yīng)作用下正庚烷池火的無量綱火焰長度(Lf/D)和火焰高度(Hf/D)與無量綱火源熱釋放速率(Q*)的1/4次方呈正比。對(duì)于火焰溫度,在煙囪效應(yīng)產(chǎn)生的風(fēng)速的冷卻作用下,不僅傾斜火焰連續(xù)區(qū)的溫升(△T)低于開放空間的火焰連續(xù)區(qū)溫升,AT大約776℃,而且火焰連續(xù)區(qū)和間歇區(qū)的范圍也有所增大,對(duì)于火焰連續(xù)區(qū),L/Q2/5從無風(fēng)情況下0-0.08增加到0-0.12,而對(duì)于火焰間歇區(qū),L/Q2/5從無風(fēng)情況下0.08-0.2增加到0.12-0.25。煙囪效應(yīng)產(chǎn)生的風(fēng)速和火源的燃燒速率相互作用、相互影響,研究結(jié)果表明風(fēng)速V與火源功率Q的1/3次方呈線性遞增關(guān)系。樓梯間通風(fēng)口位置和狀態(tài)對(duì)火源的燃燒速率、著火房間和前室的溫度場(chǎng)分布以及樓梯間內(nèi)輻射和總熱流值有一定的影響。 通過設(shè)計(jì)和建造1/6尺寸外界風(fēng)樓梯間實(shí)驗(yàn)臺(tái),研究結(jié)果表明在不同外界風(fēng)向和外界風(fēng)速作用下,樓梯間內(nèi)煙氣運(yùn)動(dòng)和相連房間的火災(zāi)特性具有四種明顯不同的模式。模式Ⅰ：隨著燃燒時(shí)間增加,樓梯間內(nèi)各層煙氣溫度和總熱流也逐漸增加,同時(shí)房間內(nèi)火焰逐漸向樓梯間方向傾斜,最終溫度、熱量值、火焰傾斜程度都達(dá)到最大。煙囪效應(yīng)是樓梯間內(nèi)煙氣運(yùn)動(dòng)的主要驅(qū)動(dòng)力。模式Ⅱ：在燃燒初期,樓梯間內(nèi)各層溫度和總熱流值都非常小,燃燒一段時(shí)間后,樓梯間內(nèi)溫度和總熱流突然地迅速升高。隨著燃燒速率的增大,煙囪效應(yīng)逐漸克服外界風(fēng)成為主要的驅(qū)動(dòng)力。模式Ⅲ：當(dāng)外界風(fēng)速比較大時(shí),在整個(gè)燃燒過程中,樓梯間內(nèi)各層煙氣溫度和總熱流值都非常小,房間內(nèi)火焰一直向室外方向傾斜�；鹪串a(chǎn)生的熱煙氣始終不能克服外界風(fēng)的阻力進(jìn)入樓梯間內(nèi)部。模式Ⅳ：在燃燒期間啟動(dòng)風(fēng)機(jī),樓梯間內(nèi)各樓層的煙氣溫度和總熱流呈現(xiàn)下降的趨勢(shì),房間內(nèi)火焰逐漸向室外方向傾斜,隨著外界風(fēng)速增大,煙氣溫度和熱流下降越快。房間內(nèi)火焰的傾斜方向主要與煙囪效應(yīng)作用力Fstack和外界風(fēng)作用力Fwind有關(guān),通過理論分析引入修正的弗洛德數(shù)Fr來判斷和分析房間內(nèi)火焰傾斜方向,最終計(jì)算出火焰方向轉(zhuǎn)變的臨界弗洛德數(shù)Fr值為0.814。當(dāng)Fr小于O.814時(shí),火焰向室外方向傾斜,否則,火焰向樓梯間方向傾斜。
[Abstract]:With the acceleration of urbanization and the increasing scarcity of land resources, the number and height of high-rise buildings in China have been growing rapidly. In addition, the rapid rise of housing prices and the rising demand for housing in recent years have further stimulated the real estate enterprises to speed up investment and the construction of high-rise buildings. High-rise buildings in all parts of the country (super) are raining like rain. With the characteristics of large quantity, high height, complex structure and diversified functions, many buildings have become the symbolic buildings of the city. At the same time, high-rise buildings are also a severe test of construction technology and safety assurance, especially the fire safety of high-rise buildings has attracted people's attention in recent years. Many large-scale high-rise building fire accidents are getting worse and worse. High-rise buildings have more floors, complex structures, large volumes, and many ways of smoke spreading, so their fire hazards are more serious, especially the chimney effect and the consequences of external wind. Therefore, it is important to study the smoke movement and fire development characteristics of high-rise buildings. Significance.
Turbulent mixing motion and chimney effect are the two main mechanisms of smoke movement in stairwells, which play a major role in different stages of fire development. The flue gas movement mechanism in stairwell affects its vertical temperature distribution. Compared with the turbulent mixing movement stage, the vertical temperature of flue gas in stairwell decreases slowly and the temperature decays slowly in the chimney effect stage. The temperature of flue gas in the closed staircase decreases fastest and the value of beta is the largest with the increase of the position of the vent and the power of the fire source.
Under the chimney effect, methanol and n-heptane pool fires tilt toward the stairwell. In this paper, Richardson number Ri is introduced to analyze the effect of chimney effect on the flame inclination angle. The results show that the dimensionless flame length (Lf/D) and flame height (Hf/D) of n-heptane pool fire are directly proportional to the 1/4 power of heat release rate (Q*) of dimensionless fire source under chimney effect. For the flame temperature, the temperature rise in the inclined flame continuum (T) is lower than that in the open flame continuum (T) under the cooling effect of the wind velocity produced by the chimney effect, and the temperature rise in the flame continuum (T) is about 776, and the range of the flame continuum and the intermittent zone is also enlarged. For the flame continuum, the L/Q2/5 increases from 0-0.08 to 0-0.12 in the windless In the intermittence zone, L/Q2/5 increases from 0.08-0.2 to 0.12-0.25 in the absence of wind. The wind velocity produced by the chimney effect interacts with the burning rate of the fire source. The results show that the relationship between the wind velocity V and the 1/3 power of the fire source Q increases linearly. The temperature field distribution and the radiation and total heat flux in the stairwell are affected.
Through the design and construction of a 1/6 scale external wind stairwell test bench, the results show that under the action of different external wind direction and external wind speed, the smoke movement in stairwell and the fire characteristics of adjacent rooms have four distinct patterns. Mode I: With the increase of combustion time, the smoke temperature and total heat flow in stairwell also gradually increase. The chimney effect is the main driving force of smoke movement in the staircase. Mode II: In the initial stage of combustion, the temperature and total heat flux in the staircase are very small. After a period of combustion, the temperature and total heat flux in the staircase are very small. With the increase of combustion rate, the chimney effect gradually overcomes the external wind and becomes the main driving force. Mode III: When the external wind speed is relatively high, the flue gas temperature and the total heat flux in the staircase are very small, and the flame in the room tilts outdoors all the time. Hot smoke can not overcome the resistance of external wind to enter the stairwell. Mode IV: Start the fan during the combustion, the smoke temperature and total heat flow in the stairwell floors show a downward trend, the room flame gradually inclined to the outdoor direction, with the increase of external wind speed, the smoke temperature and heat flow fall faster. The inclination direction is mainly related to the chimney effect force Fstack and the external wind force Fwind. The modified Freud number Fr is introduced to judge and analyze the inclination direction of the flame in the room through theoretical analysis. The critical Fr value of the flame direction transition is calculated to be 0.814. When Fr is less than O.814, the flame inclines outdoors, otherwise, The flame inclines towards the stairwell.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU972.4;TU998.1
本文編號(hào)：2195516
[Abstract]:With the acceleration of urbanization and the increasing scarcity of land resources, the number and height of high-rise buildings in China have been growing rapidly. In addition, the rapid rise of housing prices and the rising demand for housing in recent years have further stimulated the real estate enterprises to speed up investment and the construction of high-rise buildings. High-rise buildings in all parts of the country (super) are raining like rain. With the characteristics of large quantity, high height, complex structure and diversified functions, many buildings have become the symbolic buildings of the city. At the same time, high-rise buildings are also a severe test of construction technology and safety assurance, especially the fire safety of high-rise buildings has attracted people's attention in recent years. Many large-scale high-rise building fire accidents are getting worse and worse. High-rise buildings have more floors, complex structures, large volumes, and many ways of smoke spreading, so their fire hazards are more serious, especially the chimney effect and the consequences of external wind. Therefore, it is important to study the smoke movement and fire development characteristics of high-rise buildings. Significance.
Turbulent mixing motion and chimney effect are the two main mechanisms of smoke movement in stairwells, which play a major role in different stages of fire development. The flue gas movement mechanism in stairwell affects its vertical temperature distribution. Compared with the turbulent mixing movement stage, the vertical temperature of flue gas in stairwell decreases slowly and the temperature decays slowly in the chimney effect stage. The temperature of flue gas in the closed staircase decreases fastest and the value of beta is the largest with the increase of the position of the vent and the power of the fire source.
Under the chimney effect, methanol and n-heptane pool fires tilt toward the stairwell. In this paper, Richardson number Ri is introduced to analyze the effect of chimney effect on the flame inclination angle. The results show that the dimensionless flame length (Lf/D) and flame height (Hf/D) of n-heptane pool fire are directly proportional to the 1/4 power of heat release rate (Q*) of dimensionless fire source under chimney effect. For the flame temperature, the temperature rise in the inclined flame continuum (T) is lower than that in the open flame continuum (T) under the cooling effect of the wind velocity produced by the chimney effect, and the temperature rise in the flame continuum (T) is about 776, and the range of the flame continuum and the intermittent zone is also enlarged. For the flame continuum, the L/Q2/5 increases from 0-0.08 to 0-0.12 in the windless In the intermittence zone, L/Q2/5 increases from 0.08-0.2 to 0.12-0.25 in the absence of wind. The wind velocity produced by the chimney effect interacts with the burning rate of the fire source. The results show that the relationship between the wind velocity V and the 1/3 power of the fire source Q increases linearly. The temperature field distribution and the radiation and total heat flux in the stairwell are affected.
Through the design and construction of a 1/6 scale external wind stairwell test bench, the results show that under the action of different external wind direction and external wind speed, the smoke movement in stairwell and the fire characteristics of adjacent rooms have four distinct patterns. Mode I: With the increase of combustion time, the smoke temperature and total heat flow in stairwell also gradually increase. The chimney effect is the main driving force of smoke movement in the staircase. Mode II: In the initial stage of combustion, the temperature and total heat flux in the staircase are very small. After a period of combustion, the temperature and total heat flux in the staircase are very small. With the increase of combustion rate, the chimney effect gradually overcomes the external wind and becomes the main driving force. Mode III: When the external wind speed is relatively high, the flue gas temperature and the total heat flux in the staircase are very small, and the flame in the room tilts outdoors all the time. Hot smoke can not overcome the resistance of external wind to enter the stairwell. Mode IV: Start the fan during the combustion, the smoke temperature and total heat flow in the stairwell floors show a downward trend, the room flame gradually inclined to the outdoor direction, with the increase of external wind speed, the smoke temperature and heat flow fall faster. The inclination direction is mainly related to the chimney effect force Fstack and the external wind force Fwind. The modified Freud number Fr is introduced to judge and analyze the inclination direction of the flame in the room through theoretical analysis. The critical Fr value of the flame direction transition is calculated to be 0.814. When Fr is less than O.814, the flame inclines outdoors, otherwise, The flame inclines towards the stairwell.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU972.4;TU998.1
【參考文獻(xiàn)】
相關(guān)博士學(xué)位論文 前3條
1 孫曉乾;火災(zāi)煙氣在高層建筑豎向通道內(nèi)的流動(dòng)及控制研究[D];中國科學(xué)技術(shù)大學(xué);2009年
2 毛少華;煙氣中性面的理論模型及實(shí)驗(yàn)研究[D];中國科學(xué)技術(shù)大學(xué);2012年
3 涂然;高原低壓低氧對(duì)池火燃燒與火焰圖像特征的影響機(jī)制[D];中國科學(xué)技術(shù)大學(xué);2012年
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