Coupled Simulations of Nozzle Flow, Primary Fuel Jet Breakup, and Spray Formation

2004 ◽  
Vol 127 (4) ◽  
pp. 897-908 ◽  
Author(s):  
Eberhard von Berg ◽  
Wilfried Edelbauer ◽  
Ales Alajbegovic ◽  
Reinhard Tatschl ◽  
Martin Volmajer ◽  
...  
Keyword(s):  
Fluid Model ◽  
Liquid Core ◽  
Nozzle Flow ◽  
Nozzle Orifice ◽  
Spray Formation ◽  
Jet Breakup ◽  
Fuel Jet ◽  
Primary Breakup ◽  
Two Fluid Model ◽  
Breakup Model

Presented are two approaches for coupled simulations of the injector flow with spray formation. In the first approach the two-fluid model is used within the injector for the cavitating flow. A primary breakup model is then applied at the nozzle orifice where it is coupled with the standard discrete droplet model. In the second approach the Eulerian multi-fluid model is applied for both the nozzle and spray regions. The developed primary breakup model, used in both approaches, is based on locally resolved properties of the cavitating nozzle flow across the orifice cross section. The model provides the initial droplet size and velocity distribution for the droplet parcels released from the surface of a coherent liquid core. The major feature of the predictions obtained with the model is a remarkable asymmetry of the spray. This asymmetry is in agreement with the recent observations at Chalmers University where they performed experiments using a transparent model scaled-up injector. The described model has been implemented into AVL FIRE computational fluid dynamics code which was used to obtain all the presented results.

Validation of a CFD Model for Coupled Simulation of Nozzle Flow, Primary Fuel Jet Break-Up and Spray Formation

2003 ◽  
Author(s):  
E. v. Berg ◽  
W. Edelbauer ◽  
R. Tatschl ◽  
M. Volmajer ◽  
B. Kegl ◽  
...  
Keyword(s):  
Fluid Model ◽  
Liquid Core ◽  
Nozzle Flow ◽  
Coupled Simulation ◽  
Nozzle Orifice ◽  
Spray Formation ◽  
Break Up ◽  
Two Fluid Model ◽  
Two Fluid ◽  
Primary Break

A coupled simulation methodology for cavitating nozzle flow and spray formation has been developed at AVL and applied within the framework of the FIRE CFD code. In this approach a two-fluid model for cavitating nozzle flow inside the injector and a primary break-up model applied at the nozzle orifice are combined with the standard Discrete Droplet Model (DDM). Using an alternative calculation method presently also an approach with an Eulerian multi-fluid model applied for the nozzle and spray regions together is developed. A two-fluid model is used to simulate injector flows. The primary break-up model developed is based on locally resolved properties of the cavitating nozzle flow in the orifice cross section. The model delivers the initial droplet size and velocity distribution with droplet parcels released from the surface of a coherent liquid core. The characteristic feature of the results from the model is a remarkable asymmetry of the spray. Recent experimental findings from Chalmers University gained from a transparent model injector are used for model validation.

scholarly journals Evidence of vortex driven primary breakup in high pressure fuel injection

2017 ◽  
Author(s):  
Junmei Shi ◽  
Pablo Aguado Lopez ◽  
Eduardo Gomez Santos ◽  
Noureddine Guerrassi ◽  
Gavin Dober ◽  
...  
Keyword(s):  
Fuel Injection ◽  
Hybrid Approach ◽  
Flow Dynamics ◽  
Nozzle Flow ◽  
Spray Formation ◽  
Vortex Interactions ◽  
Eddy Simulation ◽  
X Ray Imaging ◽  
Diesel Injection ◽  
Primary Breakup

This paper is to present a detailed case study on how the nozzle flow dynamics influences the primary breakup inthe spray formation process of diesel injection. The investigation was based on a 3-hole real-application nozzle with highly tapered injection holes using a URANS-LES (Large Eddy Simulation) hybrid approach in combination with the coupled Volume of Fluid (VOF) and Level Set method. High resolution LES was applied to simultaneously resolve the multi-scale nozzle flow dynamics downstream of the needle seat and the primary breakup process in the near-nozzle spray. Phase Contrast X-ray imaging (PCX) was applied to characterize the liquid-gas interfaces in the near-nozzle spray for validation purposes. The results provide detailed information on how the vortex shedding and vortex interactions in the injection hole drives the jet deformation, ligament anddroplet formation in the primary breakup process.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.5707

A Numerical Investigation of Non-Evaporating and Evaporating Diesel Sprays

2008 ◽  
Author(s):  
Sibendu Som ◽  
Suresh K. Aggarwal
Keyword(s):  
Diesel Engines ◽  
Fuel Injection ◽  
Spray Penetration ◽  
Nozzle Orifice ◽  
Fuel Droplets ◽  
Injector Nozzle ◽  
Primary Breakup ◽  
Penetration Data ◽  
Modeling Code ◽  
Breakup Model

Fuel injection characteristics, in particular the atomization and penetration of the fuel droplets, are known to affect emission and particulate formation in diesel engines. It is also well established that the primary atomization process is induced by aerodynamics in the near nozzle region, as well as cavitation and turbulence from the injector nozzle. However, most breakup models used to simulate the primary breakup process in diesel engines only consider the aerodynamically induced breakup. In this paper, the standard breakup models in Diesel Engine modeling code called “CONVERGE” are examined in constant volume spray chamber geometry using the available spray data. Since non-evaporating sprays provide a more stringent test for spray models, the x-ray data from Advanced Photon Source is used for detailed validation of the primary breakup model, especially in the region very close to the nozzle. Extensive validation of the spray models is performed under evaporating conditions using liquid length and spray penetration data. Good agreement is observed for global spray characteristics. However, the breakup model could not reproduce some of the experimental trends reported in literature thus identifying the need for a more comprehensive primary breakup model. An attempt is made to statically couple the internal nozzle flow with spray simulations, and examine the effect of nozzle orifice geometry on spray penetration.

An Evaluation of a Two-Fluid Eulerian-Liquid Eulerian-Gas Model for Diesel Sprays

2003 ◽  
Vol 125 (4) ◽  
pp. 660-669 ◽  
Author(s):  
Venkatraman Iyer ◽  
John Abraham
Keyword(s):  
Fluid Model ◽  
Near Field ◽  
Far Field ◽  
Diesel Sprays ◽  
Jet Breakup ◽  
Wide Range ◽  
Numerical Grid ◽  
Two Fluid Model ◽  
Grid Independence ◽  
Two Fluid

A two fluid Eulerian-liquid Eulerian-gas (ELEG) model for diesel sprays is developed. It is employed to carry out computations for diesel sprays under a wide range of ambient and injection conditions. Computed and measured results are compared to assess the accuracy of the model in the far field, i.e., at axial distances greater than 300 orifice diameters, and in the near field, i.e., at axial distances less than 100 orifice diameters. In the far field, the comparisons are of drop mean velocities and drop fluctuation velocities and in the near field they are of entrainment velocities and entrainment constants. Adequate agreement is obtained quantitatively, within 30 percent, and qualitatively as parameters are changed. Unlike in traditional Lagrangian-drop Eulerian-fluid (LDEF) approaches that are employed for diesel spray computations, adequate resolution can be employed in the near field to achieve numerical grid independence when the two-fluid model is employed. A major source of uncertainty in the near field is in the modeling of liquid jet breakup and atomization.

Computational Prediction of the Effect of Microcavitation on an Atomization Mechanism in a Gasoline Injector Nozzle

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
Jun Ishimoto ◽  
Fuminori Sato ◽  
Gaku Sato
Keyword(s):  
High Speed ◽  
Liquid Core ◽  
Liquid Interface ◽  
Nozzle Flow ◽  
Force Model ◽  
Shear Stresses ◽  
Atomization Process ◽  
Injector Nozzle ◽  
Liquid Atomization ◽  
Primary Breakup

The effect of microcavitation on the 3D structure of the liquid atomization process in a gasoline injector nozzle was numerically investigated and visualized by a new integrated computational fluid dynamics (CFD) technique for application in the automobile industry. The present CFD analysis focused on the primary breakup phenomenon of liquid atomization which is closely related to microcavitation, the consecutive formation of liquid film, and the generation of droplets by a lateral flow in the outlet section of the nozzle. Governing equations for a high-speed lateral atomizing injector nozzle flow taking into account the microcavitation generation based on the barotropic large eddy simulation-volume of fluid model in conjunction with the continuum surface force model were developed, and then an integrated parallel computation was performed to clarify the detailed atomization process coincident with the microcavitation of a high-speed nozzle flow. Furthermore, data on such factors as the volume fraction of microcavities, atomization length, liquid core shapes, droplet-size distribution, spray angle, and droplet velocity profiles, which are difficult to confirm by experiment, were acquired. According to the present analysis, the atomization rate and the droplets-gas atomizing flow characteristics were found to be controlled by the generation of microcavitation coincident with the primary breakup caused by the turbulence perturbation upstream of the injector nozzle, hydrodynamic instabilities at the gas-liquid interface, and shear stresses between the liquid core and periphery of the jet. Furthermore, it was found that the energy of vorticity close to the gas-liquid interface was converted to energy for microcavity generation or droplet atomization.

An Empirical Shaped Charge Jet Breakup Model

2014 ◽  
Author(s):  
Ernest L. Baker ◽  
James Pham ◽  
Tan Vuong
Keyword(s):  
Shaped Charge ◽  
Jet Breakup ◽  
Shaped Charge Jet ◽  
Breakup Model

Simulation of Laminar Liquid Jets in Gaseous Crossflow Before the Onset of Primary Breakup

2011 ◽  
Author(s):  
C.-L. Ng ◽  
K. A. Sallam
Keyword(s):  
Experimental Data ◽  
Fuel Injection ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Jet Breakup ◽  
Primary Breakup ◽  
Density Ratios ◽  
First Time ◽  
Two Sides ◽  
Reduced Pressures

The deformation of laminar liquid jets in gaseous crossflow before the onset of primary breakup is studied motivated by its application to fuel injection in jet afterburners and agricultural sprays, among others. Three crossflow Weber numbers that represent three different liquid jet breakup regimes; column, bag, and shear breakup regimes, were studied at large liquid/gas density ratios and small Ohnesorge numbers. In each case the liquid jet was simulated from the jet exit and ended before the location where the experimental data indicated the onset of breakup. The results show that in column and bag breakup, the reduced pressures along the sides of the jet cause the liquid to move to the sides of the jet and enhance the jet deformation. In shear breakup, the flattened upwind surface pushes the liquid towards the two sides of the jet and causing the gaseous crossflow to separate near the edges of the liquid jet thus preventing further deformation before the onset of breakup. It was also found out that in shear breakup regime, the liquid phase velocity inside the liquid jet was large enough to cause onset of ligament formation along the jet side, which was not the case in the column and bag breakup regimes. In bag breakup, downwind surface waves were observed to grow along the sides of the liquid jet triggered a complimentary experimental study that confirmed the existence of those waves for the first time.

scholarly journals Natural modes of the two-fluid model of two-phase flow

2021 ◽  
Vol 33 (3) ◽  
pp. 033324
Author(s):  
Alejandro Clausse ◽  
Martín López de Bertodano
Keyword(s):  
Two Phase Flow ◽  
Fluid Model ◽  
Phase Flow ◽  
Two Phase ◽  
Natural Modes ◽  
Two Fluid Model ◽  
Two Fluid
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