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NEWS ARCHIVE

2/20/2013

UCICL research unraveling the mechanisms of “flashback”

 

To attain state-of-the-art criteria emission levels many combustion systems utilized lean premixed strategies.  These strategies can avoid formation of high temperature reaction zones that are responsible for high NOx emissions.  A challenge with this strategy is that the fuel and air are mixed upstream of the reaction zone.  Upsets in the system (e.g., load change, changes in ambient conditions, fuel compositional changes) can lead to propagation of the reaction from the reaction zone into the premixer causing damage and leading to high emissions.  An understanding of the mechanisms behind flashback is needed to help designers develop premixing systems that less prone to flashback.  A key mechanism is “boundary layer” flashback.  Due to the low velocity region along walls in the premixer, propagation of a reaction from downstream is likely to occur in these regions.  The ability to propagate is a complex function of, among other things, the fuel composition, the local conditions within the premixer, the wall material, and the turbulence levels in the system.  At the UCICL, extensive data have been obtained for various factors and work is underway to develop design rules that predict when flashback will occur.  Funding from the California Energy Commission and the U.S. Department of Energy, initial design rules have been developed that can be used to estimate boundary layer flashback in practical premixer tubes.

FLASHBACK 3

 

More details can be found in recent and upcoming publications:

STUDY OF FUEL COMPOSITION EFFECTS ON FLASHBACK USING A CONFINED JET FLAME BURNER (2013).  ASME J. Engr Gas Turbines and Power, Vol 135, pp. 011502-1:9 (B.Shaffer, Z. Duan, and V.G. McDonell)

 

Schlieren Image of Reaction Just Prior to Flashback
 
OH* Chemiluminensence Just Prior to Flashback

 

 

Last updated on August 21, 2013 10:52 AM -

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