Tulip flame

Tulip Flames The Shape of Deflagrations in Closed Tubes.93... 

Tulip Flames in Relahvely Short Closed Tubes.96... 

Comparison between tulips, (a) Image of an actual tulip flower that has been rotated and sized for comparison (b) the tulip shape noted by Salamandra et al. [7] in flames on their transition to detonation and (c) the inverted flame shape identified by Ellis and Wheeler [5] in closed tubes that is now being called a tulip flame. The image to the right is simply a negative of that to its left. 

Tulip Flames in Relatively Short Closed Tubes... 

As mentioned earlier, the tulip flame has been observed under a wide variety of conditions, suggesting that it is a... 

Tulip-flame formation begins simultaneously with the rapid decrease in the flame area that accompanies the flame quench at the sidewalls of fhe combustion vessel... 

The more pronounced the flame-area reduction is, the more pronounced is the tulip-flame transition... 

Formation of a tulip flame is relatively insensitive to mass loss and endwall geometry... 

Taken together, these observations indicate that the basic tulip-flame formahon is a remarkably robust phenomenon that depends somewhat on the overall geometry of the combustion vessel. There is little doubt that the growth of the cusp represents a Darrieus-Eandau instability [33-35] that is stabilized by the thermo-diffusive fransporf af fhe small scales, buf an inferesfing lingering... 

Early attempts to explain the trigger for the tulip flame focused on the pressure wave/flame interactions. This was a natural consequence of the well-documented vibratory behavior of flames seen in the very first streak images recorded [2], and the images of Markstein (like that in... 

Velocity vectors of the gas flow measured using laser Doppler anemometry inside a closed chamber during the formation of a tulip flame. Images of the flame are also shown, though the velocity measurements required many repeated runs, hence, the image is only representative. The chamber has square cross sections of 38.1mm on the side. The traces in the velocity fields are the flame locations based on velocity data dropout. The vorticity generated as the flame changes shape appears clearly in the velocity vectors. 

Laser Doppler anemometry data showing the axial velocity along the centerline of a 380 mm long closed chamber during the formation of acetylene/air tulip flames of different equivalence ratios. The velocity is measured 265 mm from the ignition thus, the tulip shape is already formed before the flame reaches the measurement point. This work shows the behavior similar to the results described in Figure 5.3.9. (Adapted from Starke, R. and Roth, R, Combust. Flame, 66,249,1986.)... 

Similar to Figure 5.3.11, another schlieren image of a tulip flame and the remnants of the vortex, proposed to initiate the instability. The location of the vortex suggests that it forms just as the hemispherical cap flame burns out at the sidewalls. 

Dunn-Rankin, D., Barr, P.K., and Sawyer, R.E., Numerical and experimental study of "Tulip" flame formation in a closed vessel, Twenty-First Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, pp. 1291-1301, 1986. 

Gonzalez, M., Borghi, R., and Saouab, A., Interaction of a flame front with its self-generated flow in an enclosure The "tulip flame" phenomenon. Combustion and Flame, 88,201-220,1992. 

N Konga,B., Fernandez, G.,Guillard,H.,and Larrouturou, B., Numerical investigations of the tulip flame instability—comparisons with experimental results, Combustion Science and Technology, 87, 69-89,1992. 

Dold, J.W. and Joulin, G., An evolution equation modeling inversion of tulip flames. Combustion and Flame, 100, 450-456, 1995. 

Jeung, I., Cho, K., and Jeong, K., Role of flame generated flow in the formation of tulip flame, paper AlAA 89-0492, 27th AlAA Aerospace Sciences Meeting, Reno, Nevada, January 9-12,1989. 

Dunn-Rankin, D. and Sawyer, R.R, Tulip flames Changes in shape of premixed flames propagating in closed tubes. Experiments in Fluids, 24,130-140,1998. 

In Chapter 5.3, D. Dunn-Rankin discusses the shape of deflagrations in closed tubes and the conditions under which it assumes the form of a tulip. The propagation of a premixed flame in closed vessels has been studied from the nineteenth century. The tulip flame is an interesting example of flame-flow interaction originating from the Landau-Darrieus instability. 

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