LASER-BASED INVESTIGATION OF SOOT FORMATION IN LAMINAR PREMIXED FLAMES AT ATMOSPHERIC AND ELEVATED PRESSURES

ABSTRACT

An experimental investigation into soot formation in laminar premixed flames at atmospheric and elevated pressures (1–5 bar) has been conducted. The flames were produced in a dual-flame burner enclosed in a pressure housing. Quantitative soot volume fraction measurements were obtained using laser-induced incandescence coupled with a quasi-simultaneous absorption measurement for calibration; the data were corrected for signal trapping using an “onion peeling” algorithm. Temperature measurements were obtained using shifted vibrational coherent anti-Stokes Raman scattering, which yields well-resolved, accurate temperature measurements in sooting and nonsooting environments. Results are presented for stable homogeneous flames using air as oxidizer and ethylene, propylene, and toluene as fuels. The variation of soot volume fraction and temperature with height above burner and as a function of fuel, equivalence ratio, and pressure are presented and discussed. The present soot data are well represented by a first-order growth rate law. The data identify trends and features useful for the validation of numerical models of soot formation.

Keywords:

• soot volume fraction
• premixed flame
• temperature
• elevated pressure
• LII
• CARS

Acknowledgments

The authors gratefully acknowledge the financial support of the Helmholtz-Gemeinschaft Deutscher Forschungszentren for funding during the PAZI program and of the Alexander von Humboldt Foundation for the award of a fellowship to R. Hadef.

Notes

Pressures are in bar.