Radiation Characteristics Models Impact On Engine Room Fire Simulation

With the development of computer hardware and computation methods,the radiationheat transfer numerical simulation has also gained rapid development.Some of the radiationcharacteristics models with handling the products of combustion as a non-gray media havebeen put in commercial software applications. But these models accuracy for combustioncalculation have not been verified.Firstly, in the article,it numerically simulated heptane fire combustion experimentsunder different environments by adopting a gray body and a gray band radiationcharacteristics models as well as being combined with the finite volume method, and theresults are compared with literature experimental data in order to verify the accuracy of theradiation characteristics. The results show that gray band model based on statistical narrowband is more than50%accurate than the gray body model in general. When gas are mainlycombustion products,gray band model can effectively improve the accuracy of thecalculation.Then the radiation characteristics models were applied to the simulation of the engineroom fire. It selected a marine engineering ship2#cabin as the physical model and FDS asthe software platform, simulated the development of the fire when cabin was closed. Theresults show that: some characterization fire development parameters, such as temperaturevalue, radiation heat flux, the source of fire extinguished will have obvious differences dueto different model applications, Gray body temperature predictive value is30%greater thanthe gray band model overall;50seconds before the fire occurred, the two models are notvery different, the gray body model also can get satisfactory results, after50s, the increaseof participatory media shows the difference of the two models.To simulate fire processaccurately, in the bottom of the cabin area, must be take a non-gray gas model.And then analysing the radiation characteristics of the engine room fire products,basedon calculation procedure of statistical Narrow Band Model，RADCAL， calculated bandsradiation intensity, bands transmittance and other characteristic parameters of the mixed gasin the cabin fire, the study radiant heat transfer of the cabin fire refined to each band, theresults showed that the in the2100-2400cm-1,3800cm-1wave number, the minimumtransmittance, the radiation intensity maximum; as the combustion proceeds, the bandtransmittance decreased and the bands radiation intensity increases, indicating that theconcentration, temperature, significant effects of radiation heat transfer, and found that fromradiation in the wave number range of0to4000cm-1, gas is the main radiation heattransfer media, after wave number of4000cm-1,the soot radiation enhanced significantly. Finally we explored the soot volume fraction of the radiation, when the soot volumefraction at E-06or more, the soot enhanced radiation significantly.As the soot absorptionalong with spectrum continuous, at this time a gray body assumptions would meet thecomputing requirements. This research work provide the basis for selection of differentradiation characteristics model when simulating the combustion process.