Numerical investigation of effects on premixed hydrogen/air flame propagation in pipes with different contraction or expansion angles. (May 2021)

• Record Type: Journal Article
• Authors: Song, Yuhan; Zhang, Ying; Chen, Yue; Liu, Xiaoyong; Fu, Ming; Li, Yuntao
• Is Part Of: Journal of loss prevention in the process industries. Volume 70(2021)
• Publication Date: 2021-05
• Subjects: Hydrogen flame -- Tulip re-formation -- Vortex -- Expansion angle -- Triple flame; Chemical industries -- Safety measures -- Periodicals; 660.2804
• DOI: 10.1016/j.jlp.2020.104201
• Languages: English
• ISSNs: 0950-4230

Abstract

Abstract: Numerical simulations of premixed hydrogen-air flame propagation in a pipe with different contraction or expansion angles are carried out in this study. The effects on the flame propagation characteristics are investigated, including flame shape, the speed of flame front and overpressure. Results show that the flame propagation at different contraction angles experiences 6 flame stages: spherical flame stage, finger-shaped flame stage, stage of flame front touching the sidewalls, classic tulip flame stage, dissipation stage of tulip flame and its re-formation stage. The formation of tulip flame and the following stages are promoted by the contraction structure. Meanwhile, the development of the flow and pressure fields near the contraction are analyzed and it is found that the paraclinical effects induced by the contraction angle enhance the tulip re-formation. In the sudden expansion pipes, a triple flame stage appears in the pipes. The flame front remains relatively static for a period of time. However, the flame would continue to propagate when the expansion angle becomes larger and the flame propagation distance in the ducts increased obviously with the larger expansion angle. Baroclinic effect can inhibit the intensity of the vortex in the flow field, and hence weaken the forward transport of fuel. This inhibit effects decrease with the expansion angle becomes larger. The results of this study have implications concerning designs for pipe geometry of hydrogen and may help get better hydrogen transportation. Highlights: FLACS simulations of hydrogen-air flame in pipes with different contraction and expansion angles are presented. The effect of different angles on the change of flame shape is studied. The feature of "triple flame extension" stage are presented. Useful conclusions are found to provide strategies for the design of hydrogen transport pipes.