Experimental and numerical investigations of hydrogen-air premixed combustion in a converging-diverging micro tube

Experimental and numerical studies of hydrogen air premixed combustion in a converging diverging micro tube with inner diameters of the inlet, throat, and outlet of 2, 1, and 2 mm, respectively, have been performed to study the combustion and flame characteristics. The influences of the equivalence ratio (Phi) and inlet velocity (v(in)) are investigated. The experiments reveal that the v(in) range for stable combustion-between 3.4 and 41.4 m/s-was significantly expanded, particularly when Phi = 1.4. This effect can primarily be attributed to the converging-diverging structure. As Phi increased, both the wall and the flame temperatures exhibited an increasing-decreasing trend; the largest heat loss ratio occurred at Phi = 1.0. The ignition position initially moved upstream and then moved downstream. The flame thickness increased and then decreased, reaching its peak value at Phi = 1.2. The flame length decreased monotonously. As v(in) increased, the wall temperature increased, the flame temperature decreased, and the flame moved downstream to grow thicker and longer. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.