Lagrangian conditional statistics of turbulent n-heptane spray combustion in different injection conditions

Abstract

3D DNS is performed for n-heptane sprays that go through ignition and combustion in different injection conditions. Conditional statistics are obtained for multiple Lagrangian groups of sequentially evaporating fuel in the group and the collective combustion regime. Ignition occurs close to but leaner than the most reactive mixture fraction for fuel of the longest residence time and low scalar dissipation rates. Combustion propagates with strong interaction among neighboring groups after ignition of the preceding flame group in the given conditions. Multiple flame groups are required for accurate description of combustion of a spray over long injection duration or multiply injected sprays. Reasonable agreement is shown between DNS and model predictions of conditional evaporation and scalar dissipation rates in the range of meaningful probabilities. Budgets are checked for all component terms in the balance equation of conditional sensible enthalpy with evaporation source terms.