Effect of ignition distance on deflagration characteristics of non-uniform oil mist in closed cabins

The deflagration of non-uniform oil mist in closed cabins can easily cause damage to ship equipment and casualties. In this work, the influence of ignition distances on the oil mist deflagration hazard is experimentally investigated, focusing on analyzing the oil mist deflagration propagation process, flame propagation speed, deflagration overpressure, and gas temperature, and exploring its influence mechanism. The results show that as the ignition distance decreases, the oil mist deflagration intensifies, flame propagation speed increases, deflagration overpressure improves, and gas temperature increases. Oil mist deflagration is divided into deflagration stage, turbulent combustion stage, and self-extinguishing stage. In deflagration stage, the center of the flame volume grows, and then gradually shrinks, moving in the direction of the nozzle. Flame propagation speed increases firstly and then decrease, accompanied by oscillatory changes in the process. The deflagration peak overpressure gradually decreases from the nozzle position to the right side of the cabin. With a nozzle diameter of 0.1 mm, the peak oil mist deflagration overpressure is around 0.25 MPa when the ignition distance is 10 cm away from the nozzle. However, when the ignition distance is 30 cm away from the nozzle, the oil mist deflagration peak overpressure is around 0.21 MPa. The high-temperature range of oil mist deflagration is mainly concentrated in the deflagration center area.