Numerical Investigation of Impulse Ventilation for Smoke Control in an Underground Car Park

Abstract

This paper examines the performance of Impulse Ventilation System (IVS) for smoke control in an underground car park. The system is evaluated in relation to important parameters including fire location, number and locations of 40 N thrust jet fans, supply rates, and extract rates. Fire Dynamic Simulator software version 5.5 is utilized to simulate 9 case studies in an 80.1 m long, 40.5 m wide and 3.3 m height domain with a car fire source simulated as a fire with a steady heat release rate of 4 MW resulted from burning polyurethane as a fuel in which soot yield equals 0.1 kg soot/kg fuel. An additional case study is carried out to examine the performance of IVS for a real car fire based on an experimental test. Results show that impulse ventilation system helps in prevention of fire smoke spreading as well as maintaining a good visibility above 5 m at a height of 1.8 m to provide a clear access for fighters. The jet fans are distributed in a way to reduce backlayering and improve visibility. The air velocity inside the car park is maintained below 5 m/s at a height of 1.8 m. However, IVS may cause temperature rise on the downwind zone of fire source with a maximum value of 90 °C (70 °C above the ambient) and fire plume tilt. High exhaust air change per hour (36 ACH) is recommended for improving the visibility and reducing the smoke backlayering.