長隧道通風之實用化

Abstract

本文在數值計算上使用有限體積法及紊流kε−模式計算風扇於隧道內的流場分析本文研究於不同風扇轉速下之隧道流場分析，以及隧道內高溫源以速度v=5 m/s和v=0.5m/s 向隧道頂端衝之流場分析，最後並分析加裝風扇的效能提高效率。 。 結果顯示，風扇在100∼1000rpm可以使隧道內的流場，產生通風的效應。於隧道的入口端有氣體被吸入，到接近風扇入口處的流場時，呈現漸縮狀的流場分佈進入風扇，經過風扇旋轉加壓後，在風扇出口，被加壓的流體直直地往隧道出口端方向吹出一段距離之後，分為兩股左右對稱流體，分別往隧道兩旁的牆壁移動，之後這兩股流體撞到牆壁之後，沿著牆壁往隧道出口處移動，同時這兩股流體也漸漸地往隧道截面的中間處擠壓。因此在隧道的出口截面的速度，發現到隧道截面兩旁的速度較大，而中間則是較小。以上介紹的流場行為是直接被風扇帶動的流體；另外還有一個是被動的流體，受直接被帶動流體的牽引，以速度較緩慢的方式往隧道出口流動。 利用數值模擬結果，還找出風扇壓差與隧道截面的流量組成的無因次式。透過這樣的無因次式，可以知道要推動多少的隧道截面流量，必須使用多少的風扇壓差。 另外，於串聯方向加裝雙風扇(皆為100rpm)和單一風扇(100rpm)於隧道內相比較，發現加裝風扇，可以使整個隧道截面的流量1.28倍。

The paper focous on the numerical calculation on fan-induced ventilation of a long tunnel by finite volume seheme and kε− turbulent model. The paper analyzes tunnel flow field at different fan rotated speed and tunnel flow field caused by fan ventilation and high temperature source flowing upward to the tunnel ceiling in v=5 m/s and v=0.5 m/s. Finally, the paper also analyzes the performance improvement efficiency by adding another fan. The results shows that tunnel flow field is on ventilation when fan blades roates at the range from 100 to 1000 rpm. At the inlet of tunnel,the gas is inhaled. Near the fan inlet area , the flow enter to the fan inlet in nozzle style.After pressued, gas is blowed in straight long distance.to the direction of tunnel outlet .After a distance,the gas is graduately divided to two group flows separately moving to the tunnel wall. Two group flows move forward to outlet of tunnel and also move to the center of tunnel cross area.So, at the outlet cross area of tunnel , the velocity near the wall is larger than that in the center of tunnel cross area. The induced flow behave is the flow induced directly by fan blades rotating. It belongs active fan-induced flow.Another is adjective flow caused by active fan-induced flow. The velocity of adjective flow is smaller than that of active fan-induced flow. Using simulation results , the dimensionless equation is created intuitively including the components of fan pressure drop and mean mass flow of tunnel corss area. Using such dimensionless equation, we can get the relation between fan pressure drop and mean mass flow of tunnel cross area. Additionally , adding another fully-similar fan can enhance the mass flow rate up to 1.28 times at the same tunnel module.