【摘要】：當(dāng)城市隧道內(nèi)發(fā)生火災(zāi)后，其狹長的內(nèi)部結(jié)構(gòu)為救援工作的開展帶來一定的阻礙，火災(zāi)產(chǎn)生的煙氣和熱量大大影響了救援的速度，容易造成大量的人員傷亡和財產(chǎn)損失，因此對城市隧道內(nèi)火災(zāi)煙氣流動的研究非常重要，可以有效指導(dǎo)隧道的滅火和人員疏散，對隧道內(nèi)防排煙設(shè)計也具有很大的指導(dǎo)意義。 本文采用FDS大渦模擬方法和1/10小尺寸實驗對縱向風(fēng)下隧道火災(zāi)煙氣分岔流動現(xiàn)象進(jìn)行研究，研究表明隨著縱向風(fēng)速的增大，隧道火災(zāi)煙氣流動匯聚區(qū)逐漸遠(yuǎn)離羽流撞擊區(qū)，出現(xiàn)分岔流動，隧道頂棚形成一個幾乎無煙氣存在的中心低溫區(qū)，研究還揭示了煙氣分岔流動的產(chǎn)生是由煙氣浮力和縱向風(fēng)慣性力所決定的。另外，在通過數(shù)值模擬研究火源位置對煙氣流動情況影響時發(fā)現(xiàn)，隨著火源逐漸靠近側(cè)壁，煙氣流動由對稱分岔流動轉(zhuǎn)變?yōu)椴粚ΨQ分岔流動，最后向兩側(cè)流動的煙氣逐漸匯聚呈“S”型流動。 本文研究發(fā)現(xiàn)，煙氣分岔流動臨界風(fēng)速即羽流撞擊區(qū)上游煙氣逆流完全消失時的最小風(fēng)速。利用FDS模擬計算改變火源熱釋放速率和隧道高度時的分岔流動臨界風(fēng)速，得出煙氣分岔流動臨界風(fēng)速與無量綱火源熱釋放速率的1/3次方成正比，是煙氣逆流臨界風(fēng)速的1.48倍，建立煙氣分岔流動臨界風(fēng)速預(yù)測模型，并通過一系列小尺寸實驗驗證該模型的可行性。 最后本文通過數(shù)值模擬對縱向風(fēng)下不同位置處豎井排煙進(jìn)行研究和比較。研究表明，煙囪效應(yīng)和邊界層分離現(xiàn)象影響豎井的排煙效果，縱向風(fēng)速較小時（1m/s），煙囪效應(yīng)引起的吸穿現(xiàn)象導(dǎo)致豎井排煙能力較差，隨著風(fēng)速的增大，吸穿現(xiàn)象消失，豎井排煙能力增強，，當(dāng)風(fēng)速過大時（2.5m/s），明顯的邊界層分離現(xiàn)象將減弱豎井的排煙能力。通過對豎井口CO體積流率的比較發(fā)現(xiàn)各豎井在縱向風(fēng)速為1-1.5m/s時排煙效果最佳，且對于與火源有相同徑向距離的豎井，側(cè)壁豎井與中心豎井排煙能力相差不大，基于實際隧道工程的需要，在豎井位置設(shè)計時可優(yōu)先選擇側(cè)壁豎井，另外，豎井的排煙能力隨著豎井逐漸遠(yuǎn)離火源而逐漸減弱，因此，在設(shè)計排煙豎井間距時，需把該因素考慮在內(nèi)。
[Abstract]:When there is a fire in the urban tunnel, its narrow internal structure brings some obstacles to the development of the rescue work. The smoke and heat generated by the fire greatly affect the speed of rescue, and it is easy to cause a large number of casualties and property losses. Therefore, the study of fire smoke flow in the urban tunnel is very important, which can effectively guide the fire fighting and evacuation of the tunnel. It also has great guiding significance for the design of smoke prevention and exhaust in tunnel. In this paper, FDS large vortex simulation method and 1 脳 10 small size experiment are used to study the phenomenon of smoke bifurcation flow in tunnel fire under longitudinal wind. The results show that with the increase of longitudinal wind speed, the convergence area of tunnel fire smoke flow is gradually away from the plume impact area, and the bifurcation flow occurs, and a central low temperature zone with almost no smoke exists in the tunnel roof. It is also revealed that the generation of flue gas bifurcation flow is determined by smoke buoyancy and longitudinal wind inertia. In addition, when the influence of fire source position on flue gas flow is studied by numerical simulation, it is found that with the fire source approaching the side wall, the smoke flow changes from symmetrical bifurcation flow to asymmetric bifurcation flow, and finally the smoke flowing to both sides gradually converges into "S" type flow. In this paper, it is found that the critical wind speed of flue gas bifurcation flow is the minimum wind speed when the upstream flue gas countercurrent in the plume impact zone disappears completely. The critical wind speed of bifurcation flow is calculated by FDS simulation when the heat release rate of fire source and tunnel height are changed. It is concluded that the critical wind speed of flue gas bifurcation flow is proportional to the 1 鈮

本文編號：2497966