Modelling and simulation of soot generation and transport

Soot released from fires not only causes danger to lives and property damage, but also effects fire spread by altering the radiation characteristics of fire effluents. In many situations, it is the soot concentration that controls the fire development. Therefore, soot modelling is of great importance in fire safety science. This necessitates the development of a global and general soot model within fire field models that can simulate the amount of soot generated and transported in large-scale fires in order to obtain an accurate soot concentration distribution within the building. \n \nA soot transport model, called Multi-Particle-Size (MPS) model, has been developed in this study to improve the prediction of soot particle behaviour during transportation by considering the uneven soot mass size distributions and gravitational settling force on soot particles. The efficiency of the MPS model was investigated by simulating soot movements in three real experiments. The first two validation experiments were cable fires in a large-scale enclosed corridor and the third experiment analysed the soot produced from a soot generator in a warehouse with a high ceiling. The soot layers predicted by the MPS model matched the measurements/observation better than that from the Conventional Model in which the soot generation is modelled with a constant soot yield (CY) value and soot particles are treated as a gaseous combustion product. \n \nA global soot generation model, called Beta soot generation (BSG) model has also been developed for non-premixed laminar flames. By making use of the characteristics of the beta function, the model has been extended to turbulent flames in the pre-scribed probability density function (PDF) approach with low cost in terms of computational resources. The model was validated by two turbulent methane and ethylene pool fires. The simulation results demonstrated that the soot volume fractions produced by the BSG model were in good agreement with the experimental data. \n \nFurther, the two new models have been integrated into a single soot model called BSG+MPS model. The performance of the model was examined by predicting the soot generation and transport in a large-scale enclosed corridor. The BSG+MPS model improved the prediction of soot concentration distribution in the corridor compared with the CY +MPS model. \n \nFinally, the entire work is summarised and future work is suggested.