Thermal ignition of acetonitrile. Experimental results and kinetic modeling

✍ Scribed by Assa Lifshitz; Carmen Tamburu; Harvey F. Carroll

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 247 KB
• Volume: 29
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/(sici)1097-4601(1997)29:11<839::aid-kin5>3.0.co;2-n

✦ Synopsis

Ignition delay times of acetonitrile (CH 3 CN) in mixtures containing acetonitrile and oxygen diluted in argon were studied behind reflected shock waves. The temperature range covered was at overall concentrations behind the reflected shock wave ranging 1420-1750 K from 2 to mol/cm 3 . Over this temperature and concentration range the ignition delay Ϫ5 4 ϫ 10 times varied by approximately one order of magnitude, ranging from ca. 100 s to slightly above 1 ms. From a total of some 70 tests the following correlation for the ignition delay times was derived: s, Ϫ12 3 0.12 Ϫ0.76 0.34 t ϭ 9.77 ϫ 10 exp(41.7 ϫ 10 /RT) ϫ {[CH CN] [O ] [Ar] } ign 3 2

where concentrations are expressed in units of mol/cm 3 and R is expressed in units of cal/(K mol). The ignition delay times were modeled by a reaction scheme containing 36 species and 111 elementary reactions. Good agreement between measured and calculated ignition delay times was obtained. A least-squares analysis of 60 computed ignition delay times from six different groups of initial conditions gave the following temperature and concentration dependence: and The ignition 3 E ϭ 46.2 ϫ 10 cal/mol, ␤ ϭ 0.43, ␤ ϭ Ϫ1.18, ␤ ϭ 0.18.

CH CN O Ar

3 2 process is initiated by H-atom ejection from acetonitrile. The addition of oxygen atoms to the system from the dissociation of molecular oxygen and from the reaction CH CN ϩ O : 3 2 is negligible. In view of the relatively high concentration of methyl radicals HO D ϩ CH CND 2 2 obtained in the reaction the branching step CH CN ϩ H : CH ϩ HCN, CH ϩ O : 3 3 3 2 plays a more important role than the parallel step A discussion CH O ϩ O H ϩ O : OH ϩ O. 3 2

of the mechanism in view of the sensitivity analysis is presented.