ECN Spray G: Coupled Eulerian internal nozzle flow and Lagrangian spray simulation in flash boiling conditions

Abstract

Flash-boiling of fuel sprays occurs when a super-heated fuel is discharged into an environment whose pressure is lower than the saturation pressure of the fuel and can dramatically alter spray formation due to complex two-phase flow effects and rapid droplet vaporization. In gasoline direct injection (GDI) engines, typically, it occurs during the injection process when high fuel temperatures make its saturation pressures higher than the in-cylinder one. Flash boiling significantly affects the spray structure and fuel-air mixture formation, with, potentially, if spray collapse is avoided, positive consequences for the engine performance and pollutant emissions. Hence, this paper developed a modelling approach based on the coupling of Eulerian multi-phase and Eulerian-Lagrangian simulations to reproduce flash boiling sprays physics. It allows a comprehensive description of the flash-boiling phenomena that begins within the injector’s ducts and continues outside, where a particular mechanism for primary breakup occurs. Experimental data of the Engine Combustion Network (ECN) Spray G injector, covering various operating conditions, were exploited to assess the reliability of the numerical technique adopted. The validation was performed taking into account various parameters such as axial liquid and vapour penetrations, droplet size and images regarding the near-nozzle zone. The numerical model achieves a pretty good level of agreement with the experimental data and, in particular, it is sensitive to the spray behaviour in the different operating conditions.

Experimental Investigation and Numerical CFD Assessment of a Thermodynamic Breakup Model for Superheated Sprays with Injection Pressure up to 700 Bar

“…The graph highlights that penetration length is overestimated using only the aerodynamic breakup model. This result has been already observed by the authors studying the Spray G with the same approach [23].…”

“…A specific input parameter allow to activate the fbBreakup model when flashing conditions were simulated. This combined thermodynamic-aerodynamic breakup model was validated in previous works of the authors, but in the present contribution, it will be extended to ultrahigh injection pressure conditions [23,28].…”

“…Therefore, without adjusting certain constants, aerodynamic breakup techniques alone cannot replicate the various flashboiling situations and, in particular, provide unrealistic droplet sizes [21,22]. An effervescent breakup model developed expressly to account for bubble expansion within droplets in flashboiling sprays exhibited significant improvement for Lagrangian spray simulations [23] and so is strongly advised. It is a distinct primary breakup mechanism that interacts with the aerodynamic breakup and considers droplet shattering as a result of thermodynamic nonequilibrium conditions.…”

Blood Flow Simulation of Aneurysmatic and Sane Thoracic Aorta Using OpenFOAM CFD Software

“…The equations were discretised by adopting the upwind scheme, while temporal integration was performed with the Euler method. The PIMPLE algorithm, featuring an implicit solution of the pressure-velocity coupling, was adopted to compute the solution [20][21][22][23].…”

Under-Expanded Jets in Advanced Propulsion Systems—A Review of Latest Theoretical and Experimental Research Activities

“…Further than in-house developed codes, basically three finite volume CFD codes were used. They are OpenFOAM, CONVERGE and STAR-CCM+ [59][60][61]. It should also be mentioned that some studies use the Lattice Boltzmann method [62,63].…”