Publications

Impact of heat release on strain rate field in turbulent premixed Bunsen flames

Coriton, Bruno R.; Frank, Jonathan H.

The effects of combustion on the strain rate field in turbulent premixed CH4/air Bunsen flames were investigated using simultaneous tomographic PIV and OH LIF measurements. Measurements were compared in three lean-to-stoichiometric flames that have different amounts of heat release and Damköhler numbers greater than unity. The extensive strain rate preferentially aligned with the flame normal in the reaction zone. The strength of this alignment increased with increasing heat release leading to highly extensive flame-normal strain rate. These effects are associated with the gas expansion normal to the flame surface which is largest for the stoichiometric flame. In the preheat zone the compressive strain rate exhibited a tendency to align with the flame normal while away from the flame front the flame the strain rate alignment was arbitrary in both the reactants and products. The flame-tangential strain rate was on average positive across the flame front implying that the turbulent strain rate field contributes to the enhancement of scalar gradients as in passive scalar turbulence.