On the transition from a highly turbulent curved flame into a tulip flame |
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| Affiliation: | 1. State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, PR China;2. School of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, PR China;1. The Collaborative Innovation Center of Safety Production of Henan Province, Henan Polytechnic University, Jiaozuo, 454003, Henan, PR China;2. State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Jiaozuo 454003, Henan, PR China;3. School of Marxism Studies, Henan Polytechnic University, Jiaozuo, 454003, Henan, PR China;1. School of Safety Science and Engineering, Xi''an University of Science and Technology, Xi''an 710054, PR China;2. Shaanxi Key Laboratory of Prevention and Control of Coal Fire, Xi''an 710054, PR China;3. Shaanxi Engineering Research Center for Industrial Process Safety and Emergency Rescue, Xi''an 710054, PR China;1. School of Safety Science and Engineering, Xi’an University of Science and Technology, 58, Yanta Mid. Rd., Xi’an 710054, Shaanxi, PR China;2. Xi''an Key Laboratory of Urban Public Safety and Fire Rescue, 58, Yanta Mid. Rd., Xi’an 710054, Shaanxi, PR China;3. Shaanxi Engineering Research Center for Industrial Process Safety & Emergency Rescue, 58, Yanta Mid. Rd., Xi’an 710054, Shaanxi, PR China;4. Shaanxi Key Laboratory of Prevention and Control of Coal Fire, 58, Yanta Mid. Rd., Xi’an 710054, Shaanxi, PR China;5. International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xi''an Jiaotong University, Xi''an, Shaanxi 710049, PR China;6. Xi''an Xinzhu Fire & Rescue Equipment Co., Ltd, Technology 1st Road 17, High-tech District, Xi''an 710075, Shaanxi, PR China;1. School of Mechanical and Power Engineering, Henan Polytechnic University, Jiaozuo 454003, PR China;2. School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454003, PR China |
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| Abstract: | Experimental and numerical investigations of premixed flame propagation behaviour associated with vortex interactions due to planar pressure waves crossing a curved flame front have been carried out. The resulting “tulip flame” formation in such a closed tube has been studied by Schlieren visualization. The “tulip flame” phenomenon was observed only in closed tubes, while cellular flame fronts appeared in half-open tubes. A physical model has been developed and implemented in a discrete vortex method combined with a flame tracking algorithm. The numerical method has been applied to model and understand the processes that cause the flame to change from a curved to a tulip shape. The results of the simulation are in good agreement with the experimental observations. We find that the rotational flows causing the tulip formation in our experimental case originate from the baroclinic effect — an interaction of non-parallel density and pressure gradients. Pressure waves were generated ahead of the accelerating and highly turbulent flame front. In closed tubes the pressure waves were reflected and crossed the curved flame front. As a result we saw the “tulip flame”. Within 0.5 ms, the flame front velocity reversed from about 50 m/s to about −20 m/s. |
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