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Abstract
Combustion-generated soot particulates is a subject of great interest due to its past and ongoing applications in research and industrial sectors. An in-house Direct Quadrature Method of Moments (DQMOM) based population balance model has been developed to investigate the evolution of soot particulate. Most commercial packages assume the particle size is monodispersed, while the proposed model enables the evaluation of real-time soot particle size distribution which further enhances prediction accuracies. The proposed model is fully coupled with all essential fire sub-modelling components and integrated with the strained laminar flamelet model considering detailed chemical kinetics. Numerical simulation with the implementation of the proposed DQMOM soot model has been validated against an in-house co-flow burner experimental study and compared with other numerical studies. The results demonstrate that the improved DQMOM soot model has a significant improvement to the accuracy of simulation when compared with Moss-Brookes soot model. It has also discovered an optimised combination of numerical configurations, e.g., nucleation and oxidation kinetics, as well as fractal dimension and Schmidt number, that yield the most agreeing results against experimental data.
The validated DQMOM model is designed to practically model realistic fire scenarios, e.g., fire whirl, a catastrophic fire phenomenon driven by eddy-generation associated with radiation feedback. Owing to the intriguing coupling of the flow dynamic and combustion kinetic, pilot investigation of fire whirl formulated under various entrainment conditions has been carried out. The test was conducted in a numerical environment decoupling all interacting, to characterise the flame temperature, flame height, velocity in axial, radial and tangential direction over a 50 s timeframe. The result demonstrates the significant enhancement of the combustion process, i.e., flame temperature and flame height, due to the intensified eddy-generation when compared with non-swirling free-standing counterpart. It also showcases the difference in the fire whirl formation pathway under various entrainment conditions. With the prior knowledge of the underlying phenomenon, the proposed DQMOM is hence subsequently integrated with the test case. In comparisons with Moss-Brookes model, the advancement of the proposed model is demonstrated in terms of fully characterising the time-dependent flaming/flow interacting behaviours.