Observations of the cellular structure of fuel–air detonations |
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| Affiliation: | 1. University of Evansville, Evansville, IN 47722, USA;2. Sandia National Laboratories, Albuquerque, NM 87185, USA;1. Beijing Institute of Technology, State Key Laboratory of Explosion Science and Technology, Beijing, 100081, PR China;2. Concordia University, Department of Mechanical and Industrial Engineering, 1455 de Maisonneuve Blvd. West, Montreal, H3G 1M8, Canada;3. McGill University, Department of Mechanical Engineering, Montreal, H3A 2K6, Canada;1. East China University of Science and Technology, State Environmental Protection Key Laboratory of Risk Assessment and Control on Chemical Process, Shanghai 200237, China;2. Beijing Institute of Technology, State Key Laboratory of Explosion Science and Technology, Beijing 100081, China;3. Concordia University, Department of Mechanical and Industrial Engineering, Montréal H3G 1M8, Canada;4. McGill University, Department of Mechanical Engineering, Montréal H3A 2K6, Canada;1. East China University of Science and Technology, Key Laboratory of Coal Gasification and Energy Chemical Engineering of Ministry of Education, Shanghai 200237, China;2. Beijing Institute of Petrochemical Technology, Beijing 102617, China;3. Peking University, College of Engineering, Department of Mechanics and Engineering Science, SKLTCS, Beijing 100871, China |
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| Abstract: | Detonation cell widths, which provide a measure of detonability of a mixture, were measured for hydrocarbon–air and hydrogen–air–diluent mixtures. Results were obtained from a 0.43-m-diameter, 13.1-m-long heated detonation tube with an initial pressure of 101 kPa and an initial temperature between 25 and 100 °C. The cell widths of simple cyclic hydrocarbons are somewhat smaller than those of comparable straight-chain alkanes. Cyclic hydrocarbons tested generally had similar cell sizes despite differences in degree of bond saturation, bond strain energy, oxygen substitution, and chemical structure. There was a significant reduction in the cell width of octane, a straight-chain alkane, when it was mixed with small quantities of hexyl nitrate. The effect of a diluent, such as steam and carbon dioxide, on the cell width of a hydrogen–air mixture is shown over a wide range of mixture stoichiometries. The data illustrate the effects of initial temperature and pressure on the cell width when compared to previous studies. Not only is carbon dioxide more effective than steam at increasing the mixture cell width, but also its effectiveness increases relative to that of steam with increasing concentrations. The detonability limits, which are dependent on the facility geometry and type of initiator used in this study, were measured for fuel-lean and fuel-rich hydrogen–air mixtures and stoichiometric hydrogen–air mixtures diluted with steam. The detonability limits are nominally at the flammability limits for hydrogen–air mixtures. The subcellular structure within a fuel-lean hydrogen–air detonation cell was recorded using a sooted foil. The uniform fine structure of the self-sustained transverse wave and the irregular structure of the overdriven lead shock wave are shown at the triple point path that marks the boundary between detonation cells. |
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