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Measurements of Spark Ignition Energy of n-Octane and i-Octane
| Title: | Measurements of Spark Ignition Energy of n-Octane and i-Octane |
| Author: | Rimpf, Lisa M. |
| Description: | Spark ignition energies were examined for various small hydrocarbons in the 1940’s and 1950’s related to mine gas explosions. In 1996, the TWA flight 800 center wing tank explosion focused interest on the measurement of aviation fuel minimum ignition energy. The goal of this study is to obtain spark ignition energy data and acquire the resultant pressure rise for n-octane and i-octane combustion as the selected species of jet fuel. Using a composite electrical spark system, ignition energy was plotted versus dc-arc spark duration time while varying the fuel/air mixture equivalence ratio, φ. For rich mixtures of i-octane, the minimum ignition energy decreased with spark duration time, reached a minimum value, and then further increased as expected; while results for lean mixtures of n-octane are not so apparent, displaying abrupt irregular behavior. The minimum of the minimum ignition energy (commonly called minimum ignition energy, MIE) for i-octane at φ≈2 was 1.5 mJ which is close to the literature value of 1.35 mJ. Also, reducing the oxygen content appears to raise the minimum ignition energy and lessen the pressure rise. The ignition process (ignition + successful flame propagation) was analyzed by considering energy furnished from the composite spark and heat release from chemical reactions opposing heat conduction energy losses to the unburned gas and electrodes. Extending and preserving the ignition kernel (plasma kernel) with dc-arc energy is critical for successful flame propagation. In this regard, dc-arc energy deposition rate is more important than the absolute energy supply. Overall, it was shown that ignition energy is dependent upon equivalence ratio as well as spark duration time while pressure rise is also subject to the stoichiometry. |
| Permanent Link: |
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1134070676
http://hdl.handle.net/2374.OX/19350 |
| Date: | 2005 |
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