Flashback in Lean Prevaporized Premixed Combustion: Nonswirling Turbulent Pipe Flow Study

A fundamental study has been performed on the upstream flame propagation of a turbulent kerosene flame, stabilized in a confined stagnation flow at atmospheric pressure. Besides temperature and equivalence ratio, mixture properties and fluid dynamic parameters have been varied. The flashback phenomenon is discussed in terms of critical mean velocities and additionally based on detailed LDV data at the outlet of the premixing duct. The largest critical velocities uc for flashback are found for the “perfectly” premixed case and equivalence ratios close to stoichiometric, which is in accordance with the theory on laminar flame propagation. In the case of a homogeneous mixture, flashback is determined by the velocity distribution at the outlet of the premixing section. In the undisturbed pipe flow the flame propagates through the wall boundary layer. The data for this case are compared with the theory of side-wall quenching in terms of a critical Peclet number and critical velocity gradients at the wall. Both are deduced from the experimental data. Reducing the velocity on the axis forces the flame to propagate through the center at a velocity predicted by correlations on turbulent flame velocity.