Detailed measurements of equivalence ratio modulations in premixed flames using laser Rayleigh scattering and absorption spectroscopy

Heiner Schwarz (1) , Laurent Zimmer (1) , Daniel Durox (1) , Sébastien Candel (1)

1 EM2C - Laboratoire d'Énergétique Moléculaire et Macroscopique, Combustion

Equivalence ratio non-uniformities may give rise to some of the instabilities observed in modern lean premixed combustion systems. The present work intends to investigate the influence of equivalence ratio perturbations on the dynamics of premixed flames. A burner equipped with a secondary injection system is used to generate equivalence ratio perturbations which are convected by the flow and impinge on a conical flame. Two laser-diagnostics, based on Rayleigh scattering and hydrocarbon infrared absorption respectively, are employed to give insight into the spatial and temporal evolution of the mixture composition field. Rayleigh scattering images also reveal the flame front dynamics providing an indication on the response of a weakly turbulent flame subject to mixture composition inhomogeneities. Laser light absorption provides a time resolved signal which is used to estimate the equivalence ration perturbation level. A theoretical model based on the G-equation is used to interpret the experimental data and compare the relative effects of velocity and equivalence ratio perturbations.

Mots clés: Flame dynamics; Rayleigh scattering; Absorption spectroscopy; Equivalence ratio perturbations

Domaines: Milieux fluides et réactifs

Heiner Schwarz, Laurent Zimmer, Daniel Durox, Sébastien Candel. Detailed measurements of equivalence ratio modulations in premixed flames using laser Rayleigh scattering and absorption spectroscopy. Experiments in Fluids, 2010, 49 (4), pp.809-821. ⟨10.1007/s00348-010-0972-3⟩. ⟨hal-00514496v2⟩