Comparison of Transient Spray Characteristics of N-dodecane and OME 3 Using Large Eddy Simulation

Abstract

There have been continuing efforts in the Engine Combustion Network (ECN) community to understand the detailed spray characteristics by investigating several standard diesel injectors. With the increasing interest in the use of alternative and renewable fuels, the present study conducted large eddy simulations with dynamic structure subgrid closure in the Eulerian volume-of-fluid (VOF) framework to identify the characteristics of oxymethylene ethers (OME), which has distinct physical and chemical properties leading to low soot emissions. In particular, the spray features of n-dodecane and OME₃ were compared and analyzed in terms of their transient dynamics following the nozzle opening. ECN Spray A, C, and D were considered to assess the effects of nozzle convergence factor and nozzle diameter. The measured nozzle geometries by the Argonne National Laboratory were adopted to mimic the internal flow development. Due to the higher density of OME₃, it generates a higher projected density, but a lower injection velocity is obtained. This behavior is attributed to its higher mass inertia. The diverging Spray C injector induces a significantly lower projected density and mass flow rate than the converging Spray D injector owing to cavitation just after the sharp nozzle inlet corner. By comparison, the Spray A injector generates the lowest projected density and mass flow rate for its smallest nozzle diameter. Various fuels demonstrate similar flow fields, evidenced by the significantly similar pressure distribution. The OME₃ cases lead to a slightly higher temperature distribution within the nozzle channel, which is attributed to the lower turbulent kinetic energy and thus the slower heat transfer process.