捷運車站防火性能設計探討

Abstract

本研究利用性能式設計法( performance-based design method )之設計程序和步驟，以及數值模擬軟體FDS ( Fire Dynamics Simulator )，針對捷運地下車站公共區以及軌道區進行案例分析。首先根據火災緊急疏散檢核，選取其中最嚴重之案例( the worst case )作為模擬案例，接著再以FDS模擬軟體，對於火災發生時之流場，溫度場及煙霧濃度作三維模擬分析，分析模擬結果所得之速度，溫度及一氧化碳濃度分布和相關的能見度及熱輻射強度來驗證車站排煙系統之設計性能是否能符合NFPA130所建議之逃生環境標準。 本研究共模擬七個案例，主要分為車站火災模擬及車站軌道區火災模擬兩部份。案例一至案例四，火源分別位於車站內之穿堂層、月台層以及通道層；案例五至案例七，火源分別位於車站軌道區第三節和第一節列車底盤。根據模擬結果可得知，由於車站部分採用分區排煙系統設計，而此設計可集中排煙風機的抽風能力，對特定區劃進行排煙，增強排煙效果，因此可減緩煙塵影響逃生避難空間的速度，增加乘客逃生避難的時間。另外，經由軌道區火災案例之模擬結果發現，無啟動月台加壓系統時，可使濃煙集中在火源鄰近的區劃，再加上UPE(Under Platform Exhaust)切換OTE(Over Track Exhaust)並隨後開啟TVF(Tunnel Ventilation Fan)的控制模式，以及月台門的設置，都有助於延後車廂內以及月台層逃生環境受到火災影響時間，提供乘客充裕的逃生時間。最後，經由數值模擬結果比對逃生時間後可得知，所有案例均滿足人員生命安全的標準，可提供捷運系統作為逃生避難計畫及煙控設計之參考。

This research carried out the fire-safety case studies for the public and track areas of underground Metro Rapid Transit (MRT) station by utilizing the design procedures of performance-based design method and the numerical simulation software, FDS (Fire Dynamics Simulator). The worst cases are selected according to the fire emergency evacuation report provided from the architecturer/builder. Then, FDS are performed to solve the three-dimensional flow, energy and species equations for the given designed fires on the public and track areas, respectively. The resultant velocity, temperature and CO concentration distributions and the corresponding visibility and radiation intensity for each case are used to evaluate whether the smoke management system can provide the tenable conditions, required by NFPA 130, on the evacuation route. In this research, seven fire scenarios were specified. Four of them were located at the different public areas (case 1 to case 4), where were the passage, concourse and platform floors, respectively. The other three undercarriage fires were located at the track areas (case 5 to case 7), where were under the first train and middle train, separately. From the simulation results, they show that using the compartmental desmoke system can utilize the full capacity of smoke exhaust fan for the particular region to enhance the smoke effect and to mitigate the smoke influence on occupant traveling speed so that the evacuation time can be increased. From the simulation results of train fires at underground station trackway, it is found that if air conditioner system is not under operation, such means can draw the smoke around the compartment of fire origin by incorporating with emergency mode, which turns off the under platform exhaust (UPE) and turns the on over track exhaust (OTE) simultaneously, and turns on tunnel ventilation fan (TVF). This desmoke procedure and the installation are very helpful for mitigate the fire/smoke influence on the evacuation route that increases the escaping time from the train and platform to the safe area. Finally, from the simulation results, all the fire protection designs are found to be able to comply with the life safety requirements for passenger evacuation. The results of this study can serve as a reference for evacuation plan and smoke control system design for underground MRT system.