Affiliation:
1. Hopkinson Laboratory, Department of Engineering, University of Cambridge, Trumpington Street, Cambridge, Cambridgeshire CB2 1PZ, UK
Abstract
Axisymmetric plumes of hydrogen, acetylene, or n-heptane were formed by the continuous injection of (pure or nitrogen-diluted) fuel into confined turbulent coflows of hot air. Autoignition and subsequent flame propagation was visualized with an intensified high-speed camera. The resulting phenomena that were observed include the statistically steady “random spots” regime and the “flashback” regime. It was found that with higher velocities and smaller injector diameters, the boundary between random spots and flashback shifted to higher air temperatures. In the random spots regime the autoignition regions moved closer to the injector with increasing air temperature and/or decreasing air velocity. After a localized explosive autoignition event, flames propagated into the unburnt mixture in all directions and eventually extinguished, giving rise to autoignition spots of mean radii of 2–5mm for hydrogen and 6–10mm for the hydrocarbons. The average flame propagation velocity in both the axial and radial directions varied between 0.5 and 1.2 times the laminar burning speed of the stoichiometric mixture, increasing as the autoigniting regions shifted upstream.
Subject
Mechanical Engineering,Energy Engineering and Power Technology,Aerospace Engineering,Fuel Technology,Nuclear Energy and Engineering
Cited by
15 articles.
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