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UBC Theses and Dissertations

The influence of swirl and turbulence on flames in lean gaseous mixtures Bauwens, Luc


Repeated measurements were made of pressure rise, in a cylindrical constant volume combustion bomb, with central ignition, in swirling mixture, for a combination of different lean mixtures of propane and air and different swirls. The swirl was obtained by high speed charging through an eccentric port. Different flow conditions were obtained by varying the decay time between the end of charging and ignition. Two different lean mixtures of propane and air were tested. Velocity measurements provided information relating to the flow field. No large spatial variation of the turbulence intensity is observed, and its decay is approximately described by the homogeneous, isotropic laws. Computing the length scales according to such a model, one observes that for both mixtures, turbulent burning velocities appear to vary linearly with Re[sub λ] . The burning rate was found to depend strongly on the equivalence ratio. Even at the highest levels obtained of turbulence intensity, the leanest mixture burns at half the speed of the richer one. No difference in ignition delay is apparent, and the ratio of burning velocities seems to be maintained virtually over the whole combustion time.

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