Combustion Science and Technology · 1979 · 77 citations · 2 references
EngineeringMechanical EngineeringCombustionTunnel EngineeringVentilationFire DynamicsFire TestingFlame PropagationHeat Transfer In FiresVentilation Network AnalysisVentilation ResistanceAir Velocity MeasurementDuct Flow ResistanceDuct ResistanceDuct VentilationFire VentilationFuel InjectionTunnel Fire VentilationVentilation During Fire Events
The study examined how wood fires in a 0.3 × 0.3 × 10 m duct affect forced ventilation flow in a model tunnel network by measuring gas mass flow, velocity, pressure, and temperature. By comparing these measurements before and during fires at various ventilation velocities and applying flow‑network analysis, the authors elucidated the coupling between duct fires and ventilation flow, revealing fire‑throttling effects and reverse‑flow phenomena. The results showed that duct fires increased tunnel flow resistance by a factor of six in the fire zone (≈1.5 upstream and downstream), throttling ventilation velocity to less than half its initial value and causing reverse flow when the throttled velocity reached about 0.6 m/s (Froude ≈ 7).
Abstract The influence of wood fires in a 0·3 ×0·3 × 10 m duct on forced ventilation flow was studied in a model tunnel network by measuring tunnel gas mass flow rate, velocity, pressure, and temperature. Comparison of these measurements obtained before and during the fires at various ventilation air velocities provides useful information on the interaction between duct fires and ventilation flow in terms of fire throttling effects and reverse flow phenomena. Results show that duct fires essentially increase flow resistances of the passageways of a tunnel network by virtue of volatile fuel mass injection and high combustion temperatures. In the present tunnel network, the flow resistance in the fire zone was increased by a factor of 6, and upstream and downstream of the fire by ∼1·5. The ventilation air velocity was thus throttled to less than half of its initial value before the fire. Reverse flow occurred when the throttled air velocity was ∼0·6 m/s, which corresponds to a Froude number of ∼7 (based on duct height and ventilation air velocity). The experimental measurements were utilized in a flow network analysis to further elucidate the coupling process between duct fires and ventilation flow.
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