An experimental study on the suppression of shielded fires by water mist sprays in a compartment

This study investigates the effectiveness of water mist systems in extinguishing shielded fires aboard marine vessels. Experiments were conducted in a standard ISO 9705 room, modified to simulate a scaled-down version of a ship engine room. A series of ten benchmark experiments were conducted varying the size of the fuel tray, ventilation in the room, presence of obstruction and its size, and suppression of the fire. Heptane was used as fuel and water mist nozzles were employed for fire suppression. The heat release rate, temperature, thermal radiation and oxygen concentration were measured during the experiments. The results showed that the water mist spray of 22 lpm extinguished a reasonably large fire of 570 kW quickly, even when the fire was shielded with a 1.4 x 1.4 m obstruction. After activation of the spray the concentration of oxygen also reduced to below combustion requirements. Key findings highlight the capability of water mist in suppressing shielded fires effectively, despite the complexities introduced by obstructions. The water mist showed an outstanding ability to reduce heat release rate, lower radiation and temperature levels, and decrease oxygen concentrations to below combustible levels, effectively extinguishing fires in compliance with established pass/fail criteria for maritime fire suppression. The data of these experiments can serve as a benchmark for validating numerical and analytical fire models.