Influence of Eddy-Generation Mechanism on the Characteristic of On-Source Fire Whirl

Abstract

This paper numerically examines the characterisation of fire whirl formulated under various entrainment conditions in an enclosed configuration. The numerical framework, integrating large eddy simulation and detailed chemistry, is constructed to assess the whirling flame behaviours. The proposed model constraints the convoluted coupling effects, e.g., the interrelation between combustion, flow dynamics and radiative feedback, thus focuses on assessing the impact on flame structure and flow behaviour solely attribute to the eddy-generation mechanisms. The baseline model is validated well against the experimental data. The data of the comparison case, with the introduction of additional flow channelling slit, is subsequently generated for comparison. The result suggests that, with the intensified circulation, the generated fire whirl increased by 9.42 % in peak flame temperature, 84.38 % in visible flame height, 6.81 % in axial velocity, and 46.14 % in velocity dominant region. The fire whirl core radius of the comparison case was well constrained within all monitored heights, whereas that of the baseline tended to disperse at 0.5 m height-above-burner. This study demonstrates that amplified eddy generation via the additional flow channelling slit enhances the mixing of all reactant species and intensifies the combustion process, resulting in an elongated and converging whirling core of the reacting flow.

Numerical Study of the Comparison of Symmetrical and Asymmetrical Eddy-Generation Scheme on the Fire Whirl Formulation and Evolution

“…It should be noted that the simulation result is validated against experimental data and achieve good comparison in temperature profile as well as the incoming velocity at the entraining slits at various HABs (height above burners), which is explained in detail in the co-published work [49]. For the sake of brevity, the validation process is not presented in this work.…”

“…The geometric features of the two domains are shown in Figure 2. The detailed description of the numerical configuration of the model has been detailed in our previous work of the characterisation of the fire whirl formulated in an enclosed chamber with different entrainment schemes [49], for the sake of brevity, such information would not be repeated herein. In summary, the geometrical features of the model include a fuel pan located in the domain centreline.…”

“…With the formulation of the nascent fire whirl after Stage B, assorted key parameters have been generated to assessed to compare the characteristic of the swirling reacting flow generated by the two cases. A quantitative assessment of key parameters of both flow dynamic and combustion perspectives of the formulated fire whirl has been described in detail in the co-published work [49], and hence for the sake of brevity, would not repeat herein. In summary, it could be concluded that, the nascent fire whirl formulated under stronger eddy-generation mechanisms, i.e., domain with two slit configuration, has elongated, constrained swirling combustion region, compared with that generated in the single slit baseline model.…”

Capturing the flame structure and the transition process of the fire whirl using two combustion kinetic considerations

“…However, the flame temperature was considerably over-predicted nearing the interface between the continuous flame and plume, the axial velocity along the vertical direction was over-predicted as well. The works presented by Wang et al (2019) firstly used the detailed chemistry mechanism in the fire whirl simulation. The air entrance via the flow channelling slit was identified as the critical condition to determine the flame structure and flame behaviour of the fully developed fire whirls.…”

Progress in Combustion Diagnostics, Science and Technology

“…This book includes a series of seventeen research studies that reveal new knowledge about combustion and its application. The topics covered span many diverse areas associated with combustion including: fires [1][2][3], engines and applications [4][5][6][7][8][9][10][11][12][13][14][15], and acoustics [16,17].…”