Numerical Study On Characteristics Of Ship Engine Room Fires

The implementation of national marine strategy will promote a new round of development of shipping industry. And the ship security issue receives more and more attention. Fire is one of main threats to ship security, leading to heavy casualties and property losses. As the power source of the ship, engine room is the location of the highest frequency of fire with the presence of high temperature and inflammables. Because of characteristics of engine room in the function, structure, ventilation and so on, ship engine room fire is very different from conventiona l building fire which has been widely studied. The study of ship engine room fire has important theoretical value and widely applying perspective, which will help to develop specific fire fighting strategies and offer references to ship fire prevention designs. For all above reasons, in this thesis, numerical analysis of characteristics of ship engine room fire has been taken.With research on a certain type of bulk carrier engine room, full scale ship engine room fire was simulated based on low Mach compressible thermally-driven flow model. And characteristics of ship engine room fire were analysed through related fire parameters. Firstly, geometric models were established through rational simplification of the engine room prototype. Numerical models describin g the ship engine room fire process and grid meshing were introduced. Then, based on the ship ceiling vented compartment model, the effect of ceiling vents and oil poo l on fire processes was investigated, focusing on quenching mode s under different ventilation conditions and fire parameters of diverse modes including temperature, gas component concentration, flame shape and so on. At last, in this thesis, influence of other factors in the real ship engine room fire scene were considered, such as pipes and equipment in the engine room, pool locatio n, initial temperature and so on.Investigation results show that the fire quenching mode of ship engine room fire can be divided into oxygen control type and fuel control type, according to the difference of fuel consumption rate and other fire parameters. And the critica l horizontal ventilation factor of two kinds of quenching mode equals 2000. Durin g the fire process, the temperature field in the cabin is distributed evenly among the horizontal direction. And the temperature stratification is obvious in the vertica l direction. The change of gas component concentration is of stage characteristics. When the ceiling vent is relatively small, the heptane gas concentration will rise quickly in the later stage of the fire. Therefore, secondary disasters, such as deflagration, should be avoided when extinguishing fire by sealing the cabin. Flame shape changes can be divided into four stages: conical flame, flame pulsation, cylindrical flame and ghosting fire. And the presence of ghosting fire is affected by the fire quenching mode. In the real ship engine room fire scene,with the increase of the oil pool’s height, the fire quenching mode will change and the extinguishing time will be prolonged. But damage of the fire is relatively reduced with the increase of the oil pool’s height in view of temperature and oxygen concentration. The increase of the initial temperature of the cabin will accelerate the oxygen consumption and the temperature rise, increasing the fire hazard. When ship engine room fire occurs, the temperature in the adjacent cabins will rise rapidly due to the spread of smoke, threatening the personnel and property in the adjacent cabins. Therefore, the safety of adjacent cabins should be taken into account in the formulation of the ship engine room fire prevention strategy.