Effects of the Initial Gel Fuel Temperature on the Ignition Mechanism and Characteristics of Oil-Filled Cryogel Droplets in the High-Temperature Oxidizer Medium
The ignition mechanism was studied for a group of gel fuel compositions in a high-temperature oxidizer medium. It was determined how the initial temperature of the fuel influences the ignition characteristics. The gel fuel (oil-filled cryogel) was prepared from an oil emulsion based on the mixture o...
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| Published in: | Energy & fuels Vol. 33; no. 11; pp. 11812 - 11820 |
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| Main Authors: | , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
American Chemical Society
21-11-2019
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| Online Access: | Get full text |
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| Summary: | The ignition mechanism was studied for a group of gel fuel compositions in a high-temperature oxidizer medium. It was determined how the initial temperature of the fuel influences the ignition characteristics. The gel fuel (oil-filled cryogel) was prepared from an oil emulsion based on the mixture of a combustible liquid and polyvinyl alcohol. The composition of primary oil emulsions was as follows: the aqueous solution of polyvinyl alcohol (5, 10 wt %) + 40–60 vol % of oil + 2 vol % of emulsifier. The initial temperature of gel fuels ranged from 188 to 293 K. Combustion was initiated in high-temperature motionless air at 873–1273 K. Using a high-speed video recording system, we established that at different initial temperatures of the gel fuel, a set of identical processes occurs during the induction period; these are different from the same physical and chemical processes during the ignition of a combustible liquid. After reaching threshold conditions, the flame spreads in the droplet’s vicinity from a hot spot through the gas mixture. Hot spot is an ignited and a small-sized fragment separating and moving away from the molten fuel droplet as a result of a microexplosion. The values of the main process characteristicignition delay timesdiffer 25–95% for fuel samples with the initial temperature of 293 K and temperatures of 188–233 K because of a long heating and melting stage of the latter. This is explained by a 2.5–3.6-fold difference in the amount of energy, which is necessary to supply to a colder fuel sample for this phase transformation to occur, other things being equal. |
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| ISSN: | 0887-0624 1520-5029 |
| DOI: | 10.1021/acs.energyfuels.9b02300 |