Experimental Investigation On The Fire Characteristics Evolution Under Typical Ship Environmental Condition

Drifting in the sea,ships often carry a large number of fire hazards,such as fuel oil and cargo,with high added value.Once the fire occurs on the ship,the fire risk is greater and it is easier to cause a large number of casualties and property losses.Thus,investigation on the disaster characteristics of ship fires is of great significance for guiding ship fire protection,design and fire extinguishingIn this paper,theoretical analysis and experiments are combined to study the disaster characteristics of two typical fire scenarios: deck surface and interior engine room:(1)The combustion characteristics of kerosene under different external temperature and wind environment are experimentally studied.The results show that when the initial temperature was lower than the flash point,the flame spread velocity increased linearly with the initial temperature;when the initial temperature is higher than flash point,and the flash burning velocity and actual burning velocity increased rapidly.When the temperature of the deck surface and the initial temperature of kerosene are lower than 60?,the heat release rate,combustion time and combustion thermal radiation characteristics of kerosene pool fire are not affected by the initial temperature.Wind environment of large scale pool fire have significant impact on burning rate: When U < 6 m/s,the steady burning rates of both fuels accelerate with the increase of the effective wind velocity;when U ? 6 m/s,the burning rates tend to be stable.Based on the full scale test,a general model for calculating the combustion rate of large-scale oil pool in a wind environment with a piecewise function consisting of a linearly increasing section and a constant section was developed.(2)The temperature profile of large scale pool fire in Marine environment under ambient wind were studied in full scale experiment.However,if the temperature field is strongly affected by the ambient wind,the flame will tilt.When the flame is inclined but not attached to the ground,the Gaussian Fit is available in the modeling of the lateral temperature profile for the vertical height level Z = 0 and other heights can be described by partial Gaussian function.The centerline temperature distribution of fire plume is predicts higher by classical plume model.The three regimes(continuous regime,buoyant plume area,intermittent flame regime)in Mc Caffrey's model are redefined and correlated well with the vertical temperature profile upon the pool centerline for large scale pool fires.(3)The spilled plumes behavior and disaster parameters of single-opening engine room are studied theoretically and experimentally.Results show that the ejected flame with horizontal eave can be distinguished into the “free flame stage”,the “flame horizontal spread stage” and the “flame overflow stage”.Based on the flame spreading model,an implicit correlation in regarding with the visible flame height,the updated flame extension area beneath the horizontal eave as well as the vertical height of the horizontal eave to the window top is established.In addition,the Gaussian distribution function is applied to the non-axial temperature distribution,and a new characteristic length p is proposed as the fitting coefficient of the Gaussian distribution.When the horizontal eave length increases,or the horizontal eave is elevated,the heat fluxes are found to be decreased.A new model of heat fluxes regarding all windows dimensions,the horizontal eave conditions and heat release rates is well correlated by-5/3 power of the normalized vertical height.(4)The theoretical model of smoke overflow with multiple openings at the top of engine room is studied.Based on the neutral surface theory and the engine room zone model,the open flow equations of engine room with top openings under mechanical smoke extraction and air supply are established,and the general simultaneous equations for the neutral plane height are obtained.A calculation model for the critical smoke extraction in the engine room without overflow is obtained under mechanical smoke exhaust and air supply,and the validity of the model is verified by experiments.When the actual smoke emission volume and the critical smoke emission volume are relatively close,the internal and external pressure difference at the opening is very small,and it is extremely susceptible to interference from outside wind and internal combustion expansion pressure,resulting in intermittent flue gas overflow.In order to form a more reliable opening overflow suppression effect,it is recommended that in practical applications,a 50% redundancy factor based on the critical smoke emission can be used to more reliably suppress flue gas overflow and make the entire fire combustion process smokeless overflow.