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.

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.

Integrated Computational Study for Total Atomization Process of Primary Breakup to Spray Droplet Formation in Injector Nozzle

2016 ◽  
Author(s):  
Naoya Ochiai ◽  
Jun Ishimoto ◽  
Akira Arioka ◽  
Nobuhiko Yamaguchi ◽  
Yuzuru Sasaki ◽  
...  
Keyword(s):  
Computational Study ◽  
Droplet Formation ◽  
Atomization Process ◽  
Spray Droplet ◽  
Injector Nozzle ◽  
Primary Breakup

The effect of transient needle lift on the internal flow and near-nozzle spray characteristics for modern GDI systems investigated by high-speed X-ray imaging

2021 ◽  
pp. 146808742098675 ◽  
Author(s):  
Dmitrii Mamaikin ◽  
Tobias Knorsch ◽  
Philipp Rogler ◽  
Jin Wang ◽  
Michael Wensing
Keyword(s):  
High Speed ◽  
Near Field ◽  
Internal Flow ◽  
Transient Behavior ◽  
Liquid Jet ◽  
Nozzle Flow ◽  
Spray Characteristics ◽  
X Ray ◽  
X Ray Imaging ◽  
Primary Breakup

The development of the injector nozzle is a dynamic area in regard of several technical aspects. At first, the internal flow influences the near-field spray characteristics via various phenomena such as cavitation and turbulence. However, these phenomena are not fully understood due to their extremely fast, complex and multiscale nature. Furthermore, it governs the spray targeting inside the combustion chamber. High-speed X-ray imaging of GDI injector nozzles is performed in this study. The experimental results presented are related to the internal flow and primary breakup of discharged liquid jets. The injectors used are equipped with nozzles made of aluminum which have been specially developed for these investigations to enhance optical accessibility. The visualization of the needle motion, in-nozzle flow and the primary breakup region provides several exciting observations. First, the needle lift tracking exhibits short overshooting right before the steady-state of the injection phase. This event leads to a short-term, however, significant change in the associated performance of the breakup. This phenomenon is found to be a consequence of the transient behavior of the in-nozzle flow. It is shown that under some circumstances hydraulic flip may occur during this overshooting period. The primary jet breakup region is visualized and evaluated by means of image processing. Thus, the transient behavior of liquid jet expansion is quantified in the vicinity of the nozzle. It is observed that the liquid jet direction deviates from the hole axis already at the nozzle outlet, which is caused by internal flow characteristics.

Liquid Atomization in a High-Speed Slinger Atomizer

2019 ◽  
Author(s):  
Arnab Chakraborty ◽  
Srikrishna Sahu
Keyword(s):  
Liquid Flow ◽  
Rotational Speed ◽  
High Speed ◽  
Working Fluid ◽  
Light Illumination ◽  
Atmospheric Conditions ◽  
Atomization Process ◽  
High Rotational Speed ◽  
Jet Breakup ◽  
Liquid Atomization

Abstract The present research aims to investigate the liquid atomization process in a slinger atomizer test rig that houses a high-speed motor which allows high rotational speed of the slinger disc. Instead of delivering the liquid directly on the slinger disc, which is commonly reported in the literature, a stationary manifold was designed that receives the liquid from the pump and supply multiple liquid jets that impinge on the rotating slinger disc. The liquid jet breakup process was visualized using front light illumination technique. All experiments were performed using water as the working fluid and under atmospheric conditions. Four different water flow rates, ranging from 0.2 lpm up to 0.8 lpm were considered. The rotational speed of the slinger was varied from 5000 rpm up to 30000 rpm, which has been rarely reported in the past. The paper reports a comprehensive study on the differences in the liquid breakup modes due to higher liquid flow rate for the same rotational speed and vice-versa. Mostly the liquid was found to attach to the side of the slinger holes that is opposite to the direction of rotation indicating the strong influence of Coriolis forces on the liquid flow within the slinger and hence the atomization process. The droplet size in the spray was measured using the Interferometric Laser Imaging for Droplet Sizing (ILIDS) technique.

Research on Solid Modeling and a Different Mode of Loading with Finite Element Analysis for Flat End Mill

2012 ◽  
Vol 500 ◽  
pp. 550-555
Author(s):  
Qing Shan Liu ◽  
Guang Yu Tan ◽  
Guang Jun Liu ◽  
Yan Li Su ◽  
Guang Hui Li
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cutting Force ◽  
High Speed ◽  
Force Model ◽  
Shear Stresses ◽  
End Mill ◽  
Element Analysis ◽  
High Speed Cutting ◽  
Loading Mode

This work aims to investigate parameterized modeling and a different mode of loading with finite element analysis for flat end mill. A loading mode is chosen according to the cutting force model of overall end mills. Normal and shear stresses which calculate from the cutting force experiments are loaded on the rack face of flat end mill. The stress distribution of end mill in high-speed cutting is obtained by finite element analysis. It is shown that the maximum stress is located at major flank face near the tool tip, rather than the nose of tool and the chisel edge. It shows the tool breakage mechanism in the local region. In the end, we compared the finite element analysis results with the experiment ones. It indicates that the analysis results agree well with the experimental data. Therefore, the proposed loading mode is available.

On the Axisymmetrical Dissemination of Glycerine Driven by Shock Wave

2014 ◽  
Vol 721 ◽  
pp. 149-152
Author(s):  
Lei Yang ◽  
Xiang Long Yang ◽  
Zhong Wei Huang
Keyword(s):  
Shock Wave ◽  
High Speed ◽  
Liquid Interface ◽  
Initial Disturbance ◽  
High Speed Photography ◽  
Pressure Transducers ◽  
Liquid Front ◽  
Disturbance Waves ◽  
Instability Development ◽  
Primary Breakup

Pressure transducers and high-speed photography technology were applied on the experimental device which formed the axisymmetrical dissemination of glycerine. The instability development at gas/liquid interface and the primary breakup were recorded by high speed photographs. It can be concluded that the wavelength of initial disturbance waves will decrease with the incensement of shock wave intensity. At the same time, the degree of mixing of spike and airflow will also be increased. The acceleration of liquid front remains unchanged in the earlier stage and rise rapidly in the later stage.

A Benchmark Control Problem for Supercavitating Vehicles and an Initial Investigation of Solutions

2003 ◽  
Vol 9 (7) ◽  
pp. 791-804 ◽  
Author(s):  
John Dzielski ◽  
Andrew Kurdila
Keyword(s):  
High Speed ◽  
Linear Models ◽  
The Body ◽  
Control Surface ◽  
Force Model ◽  
Entire Body ◽  
Benchmark Problem ◽  
Supercavitating Vehicles ◽  
Forcing Function ◽  
Natural Cavitation

At very high speeds, underwater bodies develop cavitation bubbles at the trailing edges of sharp corners or from contours where adverse pressure gradients are sufficient to induce flow separation. Coupled with a properly designed cavitator at the nose of a vehicle, this natural cavitation can be augmented with gas to induce a cavity to cover nearly the entire body of the vehicle. The formation of the cavity results in a significant reduction in drag on the vehicle and these so-called high-speed supercavitating vehicles (HSSVs) naturally operate at speeds in excess of 75 m s-1. The first part of this paper presents a derivation of a benchmark problem for control of HSSVs. The benchmark problem focuses exclusively on the pitch-plane dynamics of the body which currently appear to present the most severe challenges. A vehicle model is parametrized in terms of generic parameters of body radius, body length, and body density relative to the surrounding fluid. The forebody shape is assumed to be a right cylindrical cone and the aft two-thirds is assumed to be cylindrical. This effectively parametrizes the inertia characteristics of the body. Assuming the cavitator is a flat plate, control surface lift curves are specified relative to the cavitator effectiveness. A force model for a planing afterbody is also presented. The resulting model is generally unstable whenever in contact with the cavity and stable otherwise, provided the fin effectiveness is large enough. If it is assumed that a cavity separation sensor is not available or that the entire weight of the body is not to be carried on control surfaces, limit cycle oscillations generally result. The weight of the body inevitably forces the vehicle into contact with the cavity and the unstable mode; the body effectively skips on the cavity wall. The general motion can be characterized by switching between two nominally linear models and an external constant forcing function. Because of the extremely short duration of the cavity contact, direct suppression of the oscillations and stable planing appear to present severe challenges to the actuator designer. These challenges are investigated in the second half of the paper, along with several approaches to the design of active control systems.

Quantitative Analysis of Reynolds and Navier–Stokes Based Modeling Approaches for Isothermal Newtonian Elastohydrodynamic Lubrication

2021 ◽  
Vol 143 (12) ◽  
Author(s):  
Leoluca Scurria ◽  
Tommaso Tamarozzi ◽  
Oleg Voronkov ◽  
Dieter Fauconnier
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Thickness Distribution ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Shear Stresses ◽  
Low Viscosity ◽  
Fluid Film Thickness

Abstract When simulating elastohydrodynamic lubrication, two main approaches are usually followed to predict the pressure and fluid film thickness distribution throughout the contact. The conventional approach relies on the Reynolds equation to describe the thin lubricant film, which is coupled to a Boussinesq description of the linear elastic deformation of the solids. A more accurate, yet a time-consuming method is the use of computational fluid dynamics in which the Navier–Stokes equations describe the flow of the thin lubricant film, coupled to a finite element solver for the description of the local contact deformation. This investigation aims at assessing both methods for different lubrication conditions in different elastohydrodynamic lubrication (EHL) regimes and quantify their differences to understand advantages and limitations of both methods. This investigation shows how the results from both approaches deviate for three scenarios: (1) inertial contributions (Re > 1), i.e., thick films, high speed, and low viscosity; (2) high shear stresses leading to secondary flows; and (3) large deformations of the solids leading to inaccuracies of the Boussinesq equation.

A Mechanistic Force Model of the 5-Axis Milling Process

2000 ◽  
Author(s):  
Paul A. Clayton ◽  
Mohamed A. Elbestawi ◽  
Tahany El-Wardany ◽  
Dan Viens
Keyword(s):  
High Speed ◽  
Mechanistic Model ◽  
Back Propagation ◽  
High Speed Steel ◽  
Cutting Edge ◽  
Analytic Description ◽  
Force Model ◽  
Force Output ◽  
Five Axis ◽  
Milling Force Model

Abstract This paper presents a five-axis milling force model that can incorporate a variety of cutters and workpiece materials. The mechanistic model uses a discretized cutting edge to calculate an area of intersection which is multiplied by the specific cutting pressure to produce a force output along the primary cartesian coordinate system. By using an analytic description of the cutting edge with a non-specific cutter and workpiece intersection routine, a model was created that can describe a variety of cutting situations. Furthermore, a back propagation neural network is used to calibrate the model, providing robustness and scalability to the calibration process. Testing was performed on 1020 steel using various cutting parameters with a high speed steel two flute cutter and a tungsten carbide insert cutter. Furthermore, both linear cuts and a test die surface yielded good agreement between predicted and measured results.

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