Numerical Simulation Of Soot Model Based On Laminar Smoke Point Height Combustion Model

Soot is an important product of incomplete combustion of hydrocarbon fuels.Soot has always been an important parameter in fire risk assessment research because of its important influence on flame radiation,fire field visibility,and toxic gas generation.Indepth study of the formation and oxidation mechanism of soot in flames and numerical calculation models are important for fire smoke prediction and risk assessment.Therefore,the establishment of a flame combustion environment by numerical simulation and the development of a universal soot model that can meet the accuracy requirements for large-scale transient simulation of fire scenarios are of great practical significance and scientific value for flue gas prediction and evacuation.In this paper,we study and analyze the soot model put forward by previous researchers,choose the soot generation model based on the smoke point height as the research object,and improve the soot surface reaction oxidation model so that it can be coupled with the mixed fractional combustion model.The model was coupled to computational fluid dynamics software FLUENT via UDF.By simulating the laminar diffusion flames of ethylene and propane,the results show that the simulation results of flame temperature,axial velocity and soot volume fraction are basically consistent with the experimental values,which shows that the correction of soot oxidation model is basically reasonable.The soot volume fraction is widely distributed in the radial direction compared to the experimental values.The simulated value at the bottom of the flame is higher than the experimental value.This may be due to the neglect of the short preheating process at the fuel inlet and the generation and oxidation of soot’s endothermic/exothermic process.The modified soot generation model coupled with the eddy dissipation concept(EDC)model introduces the soot generation rate correction coefficient κ,and simultaneously couples the soot oxidation model with the turbulent combustion model-batch reactor model to make the model can be applied to turbulent combustion process.Through the simulation of the heptane and toluene oil pool fires,the adaptability of the soot generation correction model to turbulent combustion was compared and analyzed.The results show that the simulated predicted values are in good agreement with the experimental ones,indicating that the turbulent soot generation model is suitable for the turbulent combustion process;there is still a large deviation in the simulation results of the soot volume fraction at the bottom of the flame,which may be due to the soot generation.The model ignores the effects of soot particle number density and particle diameter,and does not apply to soot concentration prediction at the initial stage of soot generation.