An Experimental Investigation of the Interaction between a Karman Vortex Street and a Premixed Laminar Flame.
CALIFORNIA UNIV BERKELEY DEPT OF MECHANICAL ENGINEERING
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The interaction of a premixed C2H4-air flame with a Karman vortex street was studied. Laser Doppler anemometry was used for velocity measurements and Rayleigh scattering was used to measure total gas density. A reference hotwire was used to enable phase-locked ensemble averaging to be performed on the data. The velocity measurements, for vortex shedding cylinder Reynolds numbers 73 and 110, indicated that the vortex street and, hence, the flow field upstream of the flame is deflected by the flame. This is due to the pressure drop across the flame which is necessary to accelerate the flow behind the flame. The vortices were not observed behind the flame. The combination of dilatation and increased dissipation consumed the vortices. Density statistics obtained from Rayleigh scattering measurements were compared with predictions by the Bray-Moss-Libby B-M-L model which neglects intermediate states. Density fluctuations were overpredicted by the B-M-L model by a small amount for 73 and 110. The flame was essentially a wrinkled-laminar flame for these conditions. However, for UDv 500 the flame consisted of a distributed reaction zone and intermediate states accounted for as much as 80 of all states encountered in portions of the flame. The B-M-L model significantly overpredicted density fluctuation statistics for this condition. A qualitative comparison was made with numerical calculations by Karasalo and Namer for the time dependent interaction of a flame with an ideal Karman vortex street and suggestions for improving the model were made.
- Combustion and Ignition