Begell House
Atomization and Sprays
Atomization and Sprays
1044-5110
11
3
2001
MEASUREMENT OF BREAKUP LENGTH OF CYLINDRICAL LIQUID JETS. APPLICATION TO LOW-PRESSURE CAR INJECTOR
The present article reports an experimental investigation on the characterization of the atomization of plain cylindrical liquid jets. The main objective of the work is to measure the stability curve of jets produced by two different injectors, one of them being dedicated to low-pressure fuel-port-injected engines. Furthermore, in order to investigate the influence of the liquid, three different liquids have been tested. The experimental technique used here was developed in a previous investigation and allows one to obtain jet breakup lengths averaged from 1000 measurements for each situation. The results are therefore regarded as very accurate and reliable. It is found that the stability curve of a liquid jet contains useful information as far as the atomization of the liquid system is concerned. Confirming results obtained in a previous study, it is found here that according to the fluid used, the jet produced by an injector can show different behavior that affects its breakup length as well as the sensitivity of this length to the ambient condition. In applications such as in low-pressure gasoline injection, such information may be very valuable for development of an injection strategy.
Christophe
Dumouchel
CORIA−UMR 6614, Normandie Universite, CNRS, Universite et INSA de Rouen, France
201-226
EXPERIMENTAL INVESTIGATION OF THE DROP SIZE DISTRIBUTION OF SPRAYS PRODUCED BY A LOWVELOCITY NEWTONIAN CYLINDRICAL LIQUID JET
The origin of the critical point of a cylindrical liquid jet, first maximum of the stability curve, is not fully understood so far. In a previous experimental investigation, three different jet regimes of atomization were defined according to the influence of the gas density on the jet critical velocity.
Whether a jet is in a given regime was found to be a function of a parameter rG*, equivalent to a density. In the present investigation, the relevance of this parameter is considered and jet atomization processes are studied through the analysis of the evolution of the drop size distribution in the vicinity of the critical condition.
A (rG*, Z) map is derived from the analysis of a large amount of experimental results found in the literature. This map is of practical interest, as it helps in presupposing the behavior of a liquid jet. The analysis of the drop size distribution reveals that the instability that develops when the critical velocity is reached may be a subcritical or a supercritical instability, according to the jet regime of atomization. When a subcritical instability develops, the disintegration process is controlled by capillary instability even for velocities greater than the critical velocity, and the breakup length varies according to the initial conditions. It was found that the development of such instabilities has no effect on the relative drop size distribution width, which seems therefore to be mainly a function of the perturbation growth process. When a supercritical instability develops, the development of the critical point is due to the action of the aerodynamic forces, which increases the temporal growth rate of the instability as the velocity increases.
Helene
Malot
UMR 6614—CNRS—CORIA, Universite et INSA de Rouen, Laboratoire de Thermodynamique, Mont-Saint-Aignan, France
Christophe
Dumouchel
CORIA−UMR 6614, Normandie Universite, CNRS, Universite et INSA de Rouen, France
227-254
AN APPROACH FOR DETERMINING CONFIDENCE INTERVALS FOR COMMON SPRAY STATISTICS
The statistical analysis of spray data is a possible application for a resampling statistical technique called bootstrap. Bootstrap is a numerical technique for making statistical inferences on data when assumptions about the population distribution are unrealistic and/or the spray statistics are very complex. Application of the technique for determining confidence intervals for Sauter mean diameter and 90% cumulative volume diameter is demonstrated with drop size data from two automotive fuel injectors.
R. M.
Wagner
Department of Mechanical and Aerospace Engineering and Engineering Mechanics, University of Missouri—Rolla, Rolla, Missouri, USA
James A.
Drallmeier
Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, USA
255-268
DROPLET FORMATION AND SIZE DISTRIBUTIONS FROM AN IMMISCIBLE INTERFACE IMPINGED WITH A VERTICAL NEGATIVELY BUOYANT JET
When an upward-flowing water jet impinges on an interface with an immiscible layer of lighter oil above it, the jet momentum lifts the interface and forms a cavity. Below a threshold based on Richardson number (Ri) and Reynolds number (Re), no droplets form. Above this threshold, oil
drops are formed by two Richardson number-dependent mechanisms. At high Richardson number, an oil lip created at the edge of the cavity detaches to form oil droplets in the water below. At lower Richardson number, the water cavity becomes unstable and alternately collapses and reforms.
As the collapsing cavity impacts the interface, it drags down fingers of the upper oil layer, which break into oil droplets. This article contains extensive droplet size distributions for varying Richardson number and Reynolds number and discusses the effects of varying viscosity ratio
(h) and Morton number (Mo). Droplet sizes exhibit polydisperse log-normal distributions with mode diameters ranging from 0.6 to 1.5 mm. Characteristic diameters decrease primarily with increasing Re3/Ri, and to a lesser extent with decreasing viscosity ratio. Droplet distributions resulting from the lip pinch-off mechanism have a larger characteristic diameter than those formed by the cavity collapse mechanism.
Peter
Friedman
University of Massachusetts Dartmouth
A. L.
Winthrop
Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, Maryland, USA
Joseph
Katz
Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, Maryland, USA
269-290
THE KINETIC-SECTIONAL APPROACH FOR NONCOLLIDING EVAPORATING SPRAYS
The sectional approach, introduced by Y. Tambour [6], is aimed at reducing the numerical costs when dealing with polydisperse sprays. Indeed, by grouping the particles into sections of size, it is possible to write a system of equations involving mean quantities of each section. These mean quantities are the new unknowns of the problem, and the sectional approach proposes a method for deriving the equations. The relation between the Williams equation and the sectional approach was made precise by Greenberg et al. [3]. However, some choices in the derivation may appear arbitrary. The aim of this article is to show that, using kinetic schemes, one can write precise schemes for evaporating sprays. The study emphasizes the meaning of the different parameters involved in the derivation of the scheme.
Komla
Domelevo
UMR MIP, Universit Paul Sabatier, Toulouse, France
291-303