Transient nozzle flow simulations of gasoline direct fuel injectors

• Published in: Applied thermal engineering Vol. 175; p. 115356
• Main Authors: Shahangian, Navid, Sharifian, Leila, Uehara, Kazuhiro, Noguchi, Yasushi, Martínez, María, Martí-Aldaraví, Pedro, Payri, Raúl
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 05.07.2020; Elsevier BV
• Subjects: Aerodynamics; Air-fuel ratio; Alternative fuels; Boundary conditions; Cavitation; CFD; Computational fluid dynamics; Computer simulation; Engines; Ethanol; Flow simulation; Flow velocity; Fluid flow; Fuel injection; Fuel mixtures; Gasoline; GDi; Injectors; Internal combustion engines; Isooctane; Mass flow; Mathematical models; Multiphase flow; Navier-Stokes equations; Nozzle flow; Octane; Predictive model; Reynolds number; Simulation; Size reduction; Software; Transient; CFD; Transient; Nozzle flow; GDi; Predictive model
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2020.115356

•Opening and closing 3D URANS CFD calculations for different operating conditions are analyzed.•Same simulation strategy is successfully applied to two different injector units.•Relevance of inlet pressure for predicting the transient of the injection process is presented.•Simulation results are compared to experiments, finding a difference of about 5%.•Nozzle flow recirculations areas exert great influence on the spray pat-tern. In the field of Internal Combustion Engines (ICE) the usage of Gasoline Direct fuel injectors (GDi) with gasoline, iso-octane, ethanol (or other alternative fuels) has gained relevance in the past years with the goal of reducing fuel consumption and thus emissions. In this type of direct injections, the injector plays a major role in defining the air-fuel mixture quality. Nevertheless, the study of the phenomena inside the nozzle becomes a challenge due to its reduced size, high flow velocities and multiphase flow nature. Computational Fluid Dynamics (CFD) tools allow gaining valuable insight and understanding into such complex flow physics. Therefore, the objective of this work is the development of a predictive methodology for simulating two GDi nozzles. Unsteady Reynolds-Averaged Navier Stokes (URANS) is chosen for modeling the turbulence. The Homogeneous Relaxation Model (HRM) is used to investigate the possible phase change of the fuel through cavitation or flash boiling. Different injection conditions are simulated and results are compared against experimental data of mass flow and momentum rate for validation. CFD is able to accurately predict steady state values, but transients are very dependent on the initial and boundary conditions imposed on the model. A methodology for their definition is proposed and tested, and with it the accuracy in the prediction of the opening transient is improved.