Laminar burning velocities and Markstein lengths of aromatics at elevated temperature and pressure

Laminar burning velocities are presented for benzene, toluene, ethylbenzene, m-xylene, and n-propylbenzene. The data have been acquired at elevated temperature (450 K) and pressure (304 kPa) over the equivalence ratio range 0.80 <= phi <= 1.4. High speed schlieren visualization, used to monitor flame growth following ignition, provides a direct determination of the laminar flame speed. The data are corrected for flame stretch to yield the unstretched laminar burning velocities and burned gas Markstein lengths. The data show benzene to be the fastest, followed by ethylbenzene > n-propylbenzene > toluene > m-xylene. Iso-octane results are also presented for comparison to the literature. Flame front perturbations are observed, particularly under fuel-rich conditions, due to hydrodynamic and preferential mass diffusion instabilities. The kinetic factors responsible for the changes in the laminar burning velocities upon alkyl substitution of the aromatic ring are discussed. (c) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.