Experimental study of lean premixed turbulent combustion

Benoît Taupin (1) , David Vauchelles (1) , Gilles Cabot (1) , Abdelkrim Boukhalfa (2)

1 CORIA - Complexe de recherche interprofessionnel en aérothermochimie
2 LCSR - Laboratoire de combustion et systèmes reactifs

The purpose of this experimental study is to identify the factors that give rise to combustion instability in case of lean premixed combustion. The studied experimental device is gas turbine combustor, where the flame is stabilized in the dump combustor with a swirling and bluff-body injector. This combustor is optically accessible. A parametrical study has been conducted in the way to provide information on the effect of the equivalence ratio, φ, while the mean inlet velocity remains constant. LDV and OH * chemiluminescence measurements were performed in the reacting flows for a 50° swirler and for different equivalence ratio conditions. LDV measurements show that two distinct recirculations zones appears in the resulting flow. One is formed in the corner due to the sudden-expansion, while the other one is due to the swirling motion of the incoming flow. In order to obtain the 2D mean reaction location, an Abel deconvolution algorithm is applied to the average of 200 OH* chemiluminescence images. It allows to enhance the following relationships: as the premixing becomes leaner, the flame takes different locations in the flow. For φ > 0.7, the flame is in a steady state, anchored near the bluff-body between the two recirculation zones. For 0.7 > φ > 0.65, an extension of reaction zone occurs in the corner recirculation zone and downstream near the quartz tube. For 0.65 > φ > 0.6, the flame becomes unsteady and an oscillation of the OH * emission intensity occurs with the same frequency as measured by dynamic pressure in the combustion chamber (≈16 Hz). For φ = 0.57, the flame becomes stable again without any reaction in the corner recirculation zone. When φ is more reduced (φ <0.57), the blow-out occurs. In order to characterize the unsteady state, CH * visualization is realized by triggering acquisition with the temporal signal of pressure. Results shows a periodic behavior of flame position and combustion intensity. The analysis of all results shows a coupling between the cyclic phenomenon of vortex shedding and fluctuations in gas supply inducing a cyclic equivalence ratio at the inlet.

Domaines: Sciences de l'ingénieur [physics]; Milieux fluides et réactifs

Benoît Taupin, David Vauchelles, Gilles Cabot, Abdelkrim Boukhalfa. Experimental study of lean premixed turbulent combustion. 11th International Symposium on Applications of Laser, 2002, Lisbonne, Portugal. ⟨hal-02014967⟩