Pressure-Based Ignition Delay Times of Non-Premixed Turbulent Jet Flames Using Various Turbulence Models

Abstract

Pressure-based ignition delay times of turbulent spray combustion of n-dodecane fuel were studied using two turbulence models: Large Eddy Simulations (LES) of turbulence and Reynolds Averaged Navier Stokes (RANS). Standard RNG k-ε and Dynamic Structure models were utilized for RANS and LES turbulence modeling respectively. The simulated combustion chamber pressure rise, lift-off length, liquid penetration, and vapor penetration were compared with experimental data. The combustion chamber initial gas temperatures ranged from 850 K to 1200 K at an initial gas density of 22.8 kg/m3. A recently developed skeletal mechanism of n-dodecane with 85 species was utilized in the current work. The pressure-based ignition delay times using the Dynamic Structure turbulence model were well matched with experimental data, but the simulated pressure-based ignition delay time was over-predicted using RNG k-ε model at initial combustion chamber temperature of 850 K. The flame lift-off length, spray structure and species production and consumption histories were also investigated using different models. Both turbulence models show similar spray lift-off length at time of luminosity-based ignition delay at various combustion chamber temperatures.