Begell House Inc.
Atomization and Sprays
AAS
1044-5110
9
6
1999
VALVE-COVERED-ORIFICE (VCO) FUEL INJECTION NOZZLE DELIVERY ANALYSIS
541-579
10.1615/AtomizSpr.v9.i6.10
Edward D.
Klomp
GM R&D and Planning, Warren, Michigan, USA
This article derives analytical expressions based on a simplified analysis specifying the needle lift-time relationship and the instantaneous injection pressure which permit the fuel delivery rate, total fuel delivered per injection, and jet penetration prior to jet breakup to be evaluated for valve-covered-orifice (VCO) diesel fuel injection nozzles. This type of injection nozzle is becoming popular for use in diesel engines of advanced design. Comparisons are made to measured data from several sources with good agreement. The effect of needle eccentricity on fuel delivery is also illustrated.
ATOMIZERS FOR MOLTEN METALS: MACROSCOPIC PHENOMENA AND ENGINEERING ASPECTS
581-599
10.1615/AtomizSpr.v9.i6.20
L. A.
Nunez
Departamento de Ingenieria Mecdnica, Universidad de Chile, Santiago, Chile
T.
Lobel
Departamento de Ingenieria de Materiales, Universidad de Chile, Santiago, Chile
R.
Palma
Departamento de Ingenieria Mecánica, Universidad de Chile, Santiago, Chile
Atomizers for molten metals are used extensively for industrial and research purposes; however, the phenomena governing atomizer design — the interaction between fluids and the pressure field developed — and performance are less understood. In this article, the phenomena governing confined and free-fall atomizer behavior and performance are studied to develop engineering rules for atomizer design.
The behavior and performance of confined and free-fall atomizers, such as liquid flow rate and fineness of atomized powders, are strongly dependent on the aerodynamic pressure field (APF) developed in the atomization region. The aerodynamic pressure field defines the operational mode of an atomizer: aspirating, gravity/aspirating, or gravity. Confined atomizers can only operate in aspirating mode, since the pressure field has a wide aspirating region. Free-fall atomizers can operate in either gravity or mixed gravity/ aspirating mode, since the pressure field exhibits a narrow aspirating region followed by a flat and low-pressurization one.
A calculation methodology was developed on the basis of Lubanska's equation to evaluate the required gas flow, the total area of atomizer nozzles, the required aspiration, and the liquid delivery tube tip positions.
PRODUCTION OF HIGHLY UNIFORM SOLDER SPHERES USING A DIGITAL INTEGRAL CONTROL SCHEME
601-621
10.1615/AtomizSpr.v9.i6.30
Juan C.
Rocha
Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
Jung-Hoon
Chun
Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
The uniform droplet spray (UDS) process produces solder spheres by controlling the breakup of a continuous laminar jet into uniform droplets, which are then rapidly solidified in a liquid bath or an inert gas. Although the spheres have a narrow size distribution (±9% from mean size), still greater size accuracy is required (±3% from mean size) for the use of these spheres by the electronics industry, particularly for ball grid array (BGA) chip interconnection technology. This article discusses the production of highly size-accurate solder microspheres (75−1000 μ;m in diameter) by the UDS process. An on-line droplet size control system was developed to achieve the size distribution requirements. Droplet size control is accomplished by performing a real-time measurement of the droplet size, and then compensating for the difference between actual and target sizes by adjusting the breakup frequency. The control system is effective in controlling sphere size, enabling the UDS process to accurately determine and control solder sphere size within ±2.5% of the target size. While this article focuses on the production of large solder spheres (250−800 μ;m), the control system can be applied to spheres of any size produced by the controlled breakup of a liquid jet.
MODELING SPRAY ATOMIZATION WITH THE KELVIN-HELMHOLTZ/RAYLEIGH-TAYLOR HYBRID MODEL
623-650
10.1615/AtomizSpr.v9.i6.40
Jennifer C.
Beale
Engine Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
Rolf D.
Reitz
Engine Research Center, University of Wisconsin-Madison, Rm 1018A, 1500 Engineering Drive, Madison, Wisconsin 53706, USA
An improved spray atomization model is presented for use in both diesel and gasoline spray computations. The KH-RT hybrid atomization model consists of two distinct steps: primary and secondary breakup. The Kelvin-Helmholtz (KH) instability model was used to predict the primary breakup of the intact liquid core of a diesel jet. The secondary breakup of the individual drops was modeled with the Kelvin-Helmholtz model in conjunction with the Rayleigh-Taylor (RT) accelerative instability model. A modification was made to the KH-RT hybrid model that allowed the RT accelerative instabilities to affect all drops outside the intact liquid core of the jet. In previous implementations, only the drops beyond the breakup length are affected by RT breakup. Furthermore, a Rosin-Rammler distribution was used to specify the sizes of children drops after the RT breakup of a parent drop. The modifications made to the KH-RT hybrid model were found to give satisfactory results and to improve the temperature dependence of the liquid fuel penetration of the diesel sprays significantly. The KH-RT model was also found to predict the spray shape, penetration, and local SMD of hollow-cone sprays as well as previous gasoline spray models based on the TAB model.
EFFERVESCENT ATOMIZATION AT INJECTION PRESSURES IN THE MPa RANGE
651-667
10.1615/AtomizSpr.v9.i6.50
Robert A.
Wade
Maurice J. Zucrow Laboratories (Formerly Thermal Sciences and Propulsion Center), School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, USA
Jennifer M.
Weerts
Maurice J. Zucrow Laboratories (Formerly Thermal Sciences and Propulsion Center), School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, USA
Jay P.
Gore
Maurice J. Zucrow Laboratories (Formerly Thermal Sciences and Propulsion Center), School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, USA
W. A.
Eckerle
Fuel Systems Technology, Cummins Engine Company, Columbus, Indiana, USA
The spray characteristics of an effervescent atomizer operating in the MPa injection pressure range are reported. This work will serve as a preliminary study in the effort to apply effervescent atomization to the fuel injection process in Diesel engines. Spray mean drop size (D32) and drop size distribution width (indicated by the Rosin-Rammler exponent N) are reported as functions of injection pressure, atomizing gas-to-liquid-ratio by mass (GLR), exit orifice diameter, aerator tube geometry, and radial distance from the spray centerline. Spray cone angle is also reported as a function of injection pressure and GLR. D32 is seen to increase slightly with an increase in GLR and to decrease with an increase in exit orifice diameter. The aerator tube geometry is seen to have some influence on D32. Finally, the spray cone is found to widen with an increase in GLR and injection pressure.
Contents, Indexes of Volume 9
669-678
10.1615/AtomizSpr.v9.i6.60