The effect of fuel on high velocity evaporating fuel sprays: Large-Eddy simulation of Spray A with various fuels

Lagrangian particle tracking and Large-Eddy simulation were used to assess the effect of different fuels on spray characteristics. In such a two-way coupled modeling scenario, spray momentum accelerates the gaseous phase into an intense, multiphase jet near the nozzle. To assess fuel property effects on liquid spray formation, the non-reacting Engine Combustion Network Spray A baseline condition was chosen as the reference case. The validated Spray A case was modified by replacing n-dodecane with diesel, methanol, dimethyl ether, or propane assuming 150 MPa injection pressure. The model features and performance for various fuels in the under-resolved near-nozzle region are discussed. The main findings of the paper are as follows. (1) We show that, in addition to the well-known liquid penetration (Lliq), and vapor penetration (Lvap), for all the investigated fuels, the modeled multiphase jets exhibit also a third length scale Lcore, with discussed correspondence to a potential core part common to single phase jets. (2) As a characteristic feature of the present model, Lcore is noted to correlate linearly with Lliq and Lvap for all the fuels. (3) A separate sensitivity test on density variation indicated that the liquid density had a relatively minor role on Lliq. (4) Significant dependency between fuel oxygen content and the equivalence ratio (phi) distribution was observed. (5) Repeated simulations indicated injection-to-injection variations below 2% for Lliq and 4% for Lvap. In the absence of experimental and fully resolved numerical near-nozzle velocity data, the exact details of Lcore remain as an open question. In contrast, fuel property effects on spray development have been consistently explained herein.