| OCR Text |
Show not surprising and is most likely due to differences in fuel reactivity, which generally increases with the increase in carbon number, and to the differnces in fuel structure, with the branched compounds more readily forming ring structures than straight chain compounds. In this light, the low peak LCO level with isopar-M (highly branched) is surprising, unless degree of branching is important. Experiments performed with pure aromatic fuels such as toluene, tetralin and aromatic-150 (a solvent of C/- - C._ aromatics) also produced similar results. However, tetralin did not burn well, as indicated by high concentrations of unburned fuel in the gas samples and by somewhat lower flame temperatures. Further, a low peak LCO level was also observed, perhaps indicating that LCO is not readily formed from tetralin. Overall, the peak LCO levels for aromatic fuels was observed to increase as tetralin< toluene< aromatic-150. Toluene and aromatic-150, produced much higher LCO levels as compared to straight chain paraffins, supporting the earlier results obtained by Petrow and Cernansky (1979) and Hills and Schleyerbach (1979). The samples that produced the peak LCO levels in each of the above experiments were analysed using GC/MS. LCO samples collected during the oxidation of straight chain paraffins consisted primarily of C , C , and C 6 7 8 alcohols, ketones and aldehydes, with a few furan derivatives. However, for branched paraffins such as iso-octane, the major products formed were ring compounds, consisting of azulene, cinnoline, and benzaldehyde and naphthalene derivatives, with very few straight chain compounds. This indicates that branching may lead to rearrangement and cyclization. Isopar-M, which is solvent of branched paraffins, produced primarily C , Cin, C. n, and C. o 1U i I 12 ketones and alcohols, with very few ring structures (benzaldehyde and furan). -7- |
