Shock-Tube Study of the Ignition of Gas-Phase 1,3,5-Trimethylbenzene in Air

The
ignition delay times of gas-phase 1,3,5-trimethylbenzene/air
mixtures were measured behind reflected shock waves in a heated shock
tube facility. The experimental conditions spanned as follows: temperatures
of 1080–1560 K, pressures of 1.0–20.0 atm, and equivalence
ratios of 0.5, 1.0, and 2.0. Ignition delay times were determined
using pressure and CH* emission signals monitored at the sidewall.
The increasing temperature or pressure results in decreasing ignition
delay time definitely. However, the effect of equivalence ratio on
the ignition delay time is complex. Lean mixtures are fastest to ignite
at temperatures above 1390 K at 1.0 atm, whereas they are slowest
to ignite below 1300 K at 20.0 atm, and the equivalence ratio does
not have an evident effect on the ignition time at 5.0 atm. The global
activation energy decreases dramatically as the pressure increases
at all equivalence ratios. Current results are in good agreement with
other shock-tube experimental data, and comparisons of current data
to kinetic predictions from two recently published mechanisms are
presented. In addition, sensitivity analysis was performed to access
the important reactions in the ignition process. To our knowledge,
this study provides the first ignition delay time data for 1,3,5-trimethylbenzene
at a pressure of 1.0 atm. Present results extend the database for
1,3,5-trimethylbenzene ignition delay time.