Extinction characteristics of isolated n-alkane fuel droplets during low temperature cool flame burning in air |
| |
| Institution: | 1. Department of Mechanical Engineering, University of South Carolina, Columbia, SC 29208, USA;2. Department of Mechanical and Aerospace Engineering, Princeton University, Princeton NJ 08544. USA;1. Karlsruhe Institute of Technology (KIT), Engelbert-Arnold-Str. 4, Karlsruhe 76131, Germany;2. Technical University of Darmstadt, Alarich-Weiss-Straße 10, Darmstadt 64287, Germany;1. Combustion Research Facility, Sandia National Laboratories, MS 9052, 7011 East Avenue, Livermore, CA 94550, USA;2. Industry and Energy Area, Delegation of Government of Aragón, 50018 Zaragoza, Spain;3. School of Chemical and Biomolecular Engineering, University of Sydney, NSW 2006, Australia;1. Department of Mechanical Engineering, Faculty of Science and Technology, Keio University, Japan;2. Clean Combustion Research Center, King Abdullah University of Science and Technology, Saudi Arabia |
| |
| Abstract: | Large carbon number n-alkanes are a notable component in all real transportation fuels, and their chemical structure fosters substantial low temperature kinetic reactivity. Normal alkanes have been studied in various canonical configurations but rarely in systems with strong coupling between low temperature chemistry and transport for pure as well as for multi-component n-alkane mixtures. The Flame Extinguishment (FLEX) experiments onboard the International Space Station provided a unique platform for investigating low temperature multi-phase n-alkane and iso-alkane combustion. Among the many interesting phenomena experimentally observed, cool flame extinction can occur, accompanied by the concurrent formation of a surrounding cloud of condensed vapor. In this work we conduct numerical simulations of high and low temperature combustion of large, initially single-component n-heptane, n-decane and n-dodecane droplets. The role of initial droplet diameter, operating pressure, and n-alkyl carbon number on the extinction of hot and low temperature flames is investigated and compared against the available experimental data. While all three fuels exhibit similar hot flame behavior, cool flame activity increases with the carbon number, resulting in an increased cool flame temperature and decreased extinction diameter. Multi-cyclic “hot/cool flame transitions” are found in air as pressure is slightly increased above one atmosphere. The cyclic behaviors correspond to continuously varying hot and cool flame transitions across the high, low, and negative temperature coefficient (NTC) kinetic regimes. Further increase in pressure results in a second stage steady “Warm flame” transition. The extinction of hot and cool flame has a strong non-linear dependence on ambient pressure but as the hot flame extinction diameter increases with pressure the extinction diameter of the cool flame decreases. The computational results are compared with a recent asymptotic analysis of FLEX n-alkane cool flames. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
