Large Eddy Simulation of High Reynolds Number Non-Reacting and Reacting JP8 Sprays With a Kerosene Surrogate and Detailed Chemistry

Abstract

High-resolution single-plume JP-8 spray simulations have been performed to characterize detailed mixture formation process of high-pressure sprays for several common rail fuel injectors of interest to the Army. The first phase of the study involves examining the spray-induced turbulent mixing and global penetration parameters to present experimentally validated results across several computationally challenging length scales. Statistical convergence effects on the spray behavior and penetration profiles are presented by conducting several realizations for each injection case study. The second phase of the project adopts the grid-criteria approach developed for evaporating conditions to model turbulent combustion of a JP-8 reacting spray at compression-ignition engine conditions. A coupled Eulerian Lagrangian formulation is used to model the ensuing spray primary and secondary atomization regions using classical Kelvin Helmholtz - Rayleigh Taylor (KH-RT) wave type models. The flow turbulence subgrid scale microstructure is modeled via Dynamic Structure Large Eddy Simulation (DSLES) approach, largely resolving the anisotropic flow structures. The simulations are conducted across several fuel injector nozzle orifice dimensions ranging from 40–147 μm at a rail pressure of 1000 bar and typical compression-ignition engine operating condition of 900K and 60 bar, which is denoted as ECN Spray A. Liquid fuel physical properties are prescribed using a JP-8 surrogate mixture containing 80% n-decane and 20% trimethylbenzene (TMB) by volume. The reacting gas phase kinetics is modeled using the Aachen mechanism [26–27] and a detailed chemistry approach of a kerosene surrogate mixture. Measurements from the Army Research Laboratory (ARL) Constant Pressure Flow (CPF) chamber provide global spray and combustion parameters for comparison, including spray penetration profiles, ignition delay and flame lift-of-lengths (LOL) for JP-8 fuels. The simulation results present validated non-reacting and reacting spray simulations (ignition delay agreed within 4% and flame LOL agreed within 5% of measured data) and provide insights into the atomization and mixing characteristics across several orifice dimensions.