One-dimensional-turbulence simulation of flame extinction and reignition in planar ethylene jet flames

Abstract

A series of three simulations of temporally evolving, planar, nonpremixed ethylene jet flames are performed using the one-dimensional-turbulence (ODT) model. The simulations are performed at a fixed Reynolds number, but varying Damköhler numbers, under conditions that result in significant flame extinction and reignition. Results are compared to corresponding direct numerical simulations (DNSs), which exhibit 40, 70, and nearly 100% peak flame extinction among the three cases. The planar, temporal configuration is ideal for comparison and validation of the ODT model, and identical thermodynamic, transport, and kinetic models were used. The ODT model captures the jet evolution and heat release effects. Line of sight profiles are qualitatively similar between the ODT and DNS. Good agreement is found for scalar dissipation statistics. While ODT captures the flame extinction process, the level of flame reignition is underpredicted, and conditional mean temperature profiles are depressed during reignition compared to the DNS. This is in contrast to previous ODT studies using CO/H2 mixtures (syngas). As a one-dimensional model, ODT is unable to capture multi-dimensional edge flame propagation during reignition, but is able to capture reignition via flame folding. Given the fidelity of the fine-scale transport and reaction processes built into ODT, and good flow modeling observed, more reduced combustion models will be challenged to capture nonpremixed flame reignition.