Optimization of Smoke Control in Subway Stations
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Ghent University Faculty of Engineering Department of Flow, Heat and Combustion Academic Year 2011-2012 OPTIMIZATION OF SMOKE CONTROL SYSTEMS IN UNDERGROUND SUBWAY STATIONS Nicholas Bartlett Promoter: Bart Merci Master thesis submitted in the Erasmus Mundus Study Programme International Master of Science in Fire Safety Engineering DISCLAIMER This thesis is submitted in partial fulfillment of the requirements for the degree of The International Master of Science in Fire Safety Engineering (IMFSE). This thesis has never been submitted for any degree or examination to any other University/programme. The author declares that this thesis is original work except where stated. This declaration constitutes an assertion that full and accurate references and citations have been included for all material, directly included and indirectly contributing to the thesis. The author gives permission to make this master thesis available for consultation and to copy parts of this master thesis for personal use. In the case of any other use, the limitations of the copyright have to be respected, in particular with regard to the obligation to state expressly the source when quoting results from this master thesis. The thesis supervisor must be informed when data or results are used. April 30, 2012, Nicholas Bartlett Summary/Abstract History has shown that fires in underground subway stations pose a severe threat to the life safety of occupants. The purpose of this thesis is to analyze various smoke control strategies in underground subway stations, starting from an existing subway station. Strategies implemented include passive only, mechanical only, and hybrid methods of smoke control. Each case is studied by means of CFD, using FDS V5.0. Cases are ranked based on ability to maintain a smoke free environment on both levels of the station. Platform screen doors and longitudinal ventilation are found to be most useful in controlling smoke spread at platform level. Extraction and stairwell enclosures are seen to control smoke spread to the upper level. Hybrid methods of smoke control result in tenable conditions on both levels for the longest average period of time. Sufficient exit capacity and proper location within the station are critical to ensuring safe occupant egress. Some conclusions drawn can be applied to general fire safety design of subway stations. 2 Contents 1. List of Abbreviations & Definitions ....................................................................................................... 5 2. List of Tables and Figures ...................................................................................................................... 6 3. Introduction & Objective ...................................................................................................................... 9 3.1 Need .............................................................................................................................................. 9 3.2 Objectives.................................................................................................................................... 10 3.3 Limitations of Research ............................................................................................................... 10 4. Literature Review ................................................................................................................................ 11 4.1 Small Scale Material Tests ................................................................................................................. 11 4.2 Heat Release Rates of Subway Trains ............................................................................................... 14 4.2.1 Real-Scale Tests .......................................................................................................................... 15 4.2.2 Alternate Methods of HRR Prediction ....................................................................................... 18 4.2.3 Previously Proposed Design Fires .............................................................................................. 19 4.2.4 Carry-on Luggage ....................................................................................................................... 22 4.2.5 Miscellaneous Issues Related to the HRR .................................................................................. 23 4.2.6 Design Fire Proposal ................................................................................................................... 24 4.3 Risk Assessment Discussion .............................................................................................................. 24 5. Current Practices in Station Fire Safety .............................................................................................. 25 5.1 Results of Questionnaire ................................................................................................................... 25 5.2 Methods of Smoke Control ............................................................................................................... 26 5.2.1 Smoke Control Methods – Mechanical Ventilation ................................................................... 26 5.2.2 Smoke Control Methods – Natural Ventilation ......................................................................... 29 5.2.3 Smoke Control Methods – Passive ............................................................................................. 30 6. Case Study Subway Station ..................................................................................................................... 32 6.1 Station & Tunnel Description ............................................................................................................ 32 6.2 Train Geometry ................................................................................................................................. 33 7. Evacuation Calculations .......................................................................................................................... 34 7.1 Prescriptive Approach ....................................................................................................................... 34 7.2 FDS+Evac Approach .......................................................................................................................... 34 8. CFD Simulations ...................................................................................................................................... 36 8.1. Choice of FDS ................................................................................................................................... 36 3 8.2 Organization of Simulations .............................................................................................................. 36 8.3 Input Parameters .............................................................................................................................. 37 8.3.1 Geometry ................................................................................................................................... 37 8.3.2 Material Selection ...................................................................................................................... 38 8.3.3 Window Properties .................................................................................................................... 39 8.3.4 Soot Production ......................................................................................................................... 39 8.3.5 Heat Release Rate & Combustion Parameters .......................................................................... 41 8.3.6 Boundary Conditions .................................................................................................................. 41 8.3.7 Radiation Model ......................................................................................................................... 42 8.4 Tenability Criteria .............................................................................................................................. 42 9. Results ................................................................................................................................................. 44 9.1 Grid sensitivity .................................................................................................................................. 44 9.2 Material sensitivity ............................................................................................................................ 46 9.3 Boundary Condition Sensitivity ......................................................................................................... 47 9.4 Resulting HRR .................................................................................................................................... 49 9.5 Simulation Results – Concourse Level Visibility ................................................................................ 54 9.5.1 Passive Smoke Control ............................................................................................................... 56 9.5.2 Mechanical Smoke Control ........................................................................................................ 60 9.6 Simulation Results – Platform Level Visibility ............................................................................. 68 9.7 Simulation Results - Temperature ...................................................................................................