Comparison between Experimental Measurements and Numerical Calculations of the Structure of Heptane-Air Diffusion Flames

Abstract

Detailed numerical calculations are performed to determine the structure of heptane-air diffusion flames, and the results are compared with experimental measurements. The configuration used is the diffusion flame stabilized in the vicinity of a stagnation plane, which is formed by directing an oxidi2ing gas flow onto the vaporizing surface of a pool of heptane. Profiles of the concentration of various stable species and of the temperature have been measured by gas chromatography and by thermocouples. respectively. To evaluate the influence of strain on the structure or the flame, the measurements taken at a fixed composition of the oxidizer stream and at two values of the strain rate were chosen for comparison with the calculated results. The computations were performed using a chemical kinetic mechanism consisting of forty-two elementary reactions involving eighteen species. To simplify the chemical kinetic mechanism, it was assumed that heptane is attacked by radicals to form the heptyl radical whose decomposition to CH₃ and C₃H₆ is represented by a one-step overall reaction. Good agreement was obtained between the results of the detailed numerical calculations and the experimental measurements. It was found that aspects of the structure of heptane-air diffusion flames relevant to asymptotic descriptions are similar to those of methane-air diffusion flames. Hence, the previously developed techniques for asymptotic analysis of the structure of methane-air flames can be used for analyzing the structure of heptane-air flames.