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2009 | Book

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Charge Injection Systems

Phycical Principles, Experimental and Theoretical Work

Author: John Shrimpton

Publisher: Springer Berlin Heidelberg

Book Series : Heat and Mass Transfer

Part of: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik"

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About this book

C Specific heat at constant pressure p D Displacement field D Diffusion coefficient d D Orifice diameter E Electric field E Electron charge F Force G Acceleration due to gravity I Current J Current flux K Conductivity k Boltzmann constant B L Atomizer geometry: length from electrode tip to orifice plane i L Atomizer geometry : length of orifice channel o P Polarization Q Flow rate/Heat flux Q Charge r Atomizer geometry : electrode tip radius p T Time T Temperature U Velocity V Voltage W Energy X Distance Nomenclature (Greek) Thermal expansion coefficient ? Permittivity ? Permutation operator ? ijk Ion mobility ? VI Nomenclature Debye length ? D ? Dynamic viscosity ? Mass density Surface tension ? T Electrical conductivity ? ? Timescale ? Vorticity Nomenclature (Subscripts) Reference state ? o Cartesian tensor notation ? ijk Volume density (? per unit volume) ? v Surface density (? per unit area) ? s Linear density (? per unit length) ? l ‘critical’ state ? c Bulk mean injection ? inj Nomenclature (Superscripts) Time or ensemble averaged ? Contents Contents 1 Introduction…………………………………………………………. 1 1.1 Introduction and Scope………………………………………….. 1 1.2 Organization…………………………………………………….. 3 2 Electrostatics, Electrohydrodynamic Flow, Coupling and Instability………………………………………………………... 5 2.1 Electrostatics…………………………………………………….. 5 2.1.1 The Coulomb Force……………………………………… 5 2.1.2 Permittivity……………………………………………… 6 2.1.3 Conductors, Insulators, Dielectrics and Polarization…….. 6 2.1.4 Gauss’s Law……………………………………………... 8 2.2 Mobility and Charge Transport…………………………………. 10 2.2.1 Introduction……………………………………………… 10

Table of Contents

Frontmatter
Introduction
Abstract
This monograph covers the literature and patents relevant to a specific type of liquid and a specific method of atomization. The liquids are dielectrics; poor electrical conductors, typically vegetable oils such as corn, soy and rapeseed, or petroleum products, such as petrol/gas, aviation fuel and Diesel oils. The liquids need not be ‘doped’ to enhance their electrical conductivity. The ‘charge injection’ atomizer injects electric charge into the poorly conducting liquid and the liquid atomization, spray dispersion and combustion are significantly influenced by the presence of the injected electric charge. The monograph initially covers electrohydrodynamic basics, fundamental studies of charge injection into quiescent liquid, and the design and operation of the atomizer itself. The review then continues by surveying studies of the primary atomization process, spray characterization, and effect on combustion before finally discussing measurements of the radial distribution of spray charge and modeling of the drop diameter and charge probability distribution. The review concludes that whilst some fundamental understanding still requires more research, sufficient knowledge exists to design and operate practical devices.
John Shrimpton
Electrostatics, Electrohydrodynamic Flow, Coupling and Instability
Abstract
Electrostatics is a term used to describe the physics of charge in motion and at rest in the absence of significant magnetic field effects and can be used to refer to any type of phase where this is the case [13]. Electrohydrodynamics (EHD) is a more specialized term that is generally used to refer to the role of electrostatics in liquid media. A good introduction to electrostatics can be found in texts such as Crowley [13] and Chang et al. [10] with a more EHD orientated approach taken in Melcher [14] and specific to dielectrics, Castellanos [15]. Much of what follows in this chapter can be found in these references, but for the benefit of those new to the subject is repeated here in a more concise form to enable a better understanding of the literature discussed in chapters 3 onwards. A discussion of instability due to EHD interactions is included, since the internal flow within charge injection atomizers is generally within this regime.
John Shrimpton
Charge Injection into a Quiescent Dielectric Liquid
Abstract
Upstream of the atomizer orifice the dielectric liquid remains in a continuous phase. The physics acting on this region were discussed in the preceding sections however the analysis given automatically assumes that an electrical charge is present. The aim of this chapter is to describe how the electrical charge actually enters the dielectric liquid, the effect on the measurable electrical quantities and, depending on the operating conditions of the atomizer, additional physical phenomena that may arise.
John Shrimpton
Single Charged Drop Stability, Evaporation and Combustion
Abstract
Before moving onto more applied and empirical aspects of the monograph, in this chapter the effect electrical charge has upon the stability, and also the evaporation and combustion processes of a single liquid drop is discussed. This may be viewed as a precursor to a discussion of the characteristics of spray plumes, which are generated by electrostatic atomizers and are comprised of electrically charged drops.
John Shrimpton
Charge Injection Atomizers: Design and Electrical Performance
Abstract
The ease and efficiency by which fluids and solids can be atomized and manipulated by electrostatic fields has long been recognized and there now exists a plethora of applications and systems for the spraying of liquids that are at least electrically semi-conducting. A brief review is presented here, which is by no means exhaustive, and serves to demonstrate the dearth of systems able to electrostatically charge and hence spray electrically insulating fluids. The remainder of the chapter then summarises the empirical knowledge available concerning simple charge injection atomizer designs, required to electrostatically atomize electrically insulating liquids.
John Shrimpton
Jet Instability and Primary Atomization
Abstract
Studies of the break-up of dielectric liquid jets are theoretically more complicated than prediction of instability of conducting liquids because the surface charge distribution is not at an equipotential and the surface area evolves. Therefore the jet surface electrical boundary conditions are not well defined. This chapter covers the experimental data available, and provides qualitative understanding and empirical correlations.
John Shrimpton
Spray Characterization and Combustion
Abstract
For charge injection atomization, of electrically insulating liquids, it is typical that a polydisperse drop diameter distribution is present in the spray. It is also typical that the mean trajectories of the drops are a function of the mean drop diameter, and that the smaller drops tend to be found on the spray periphery, and the larger drops nearer the spray axis. These observations are now discussed in more detail.
John Shrimpton
Conclusions and Future Outlook
Conclusions
The manuscript brings together several disparate fundamental research areas and presents the information in the context of the development of understanding of a practical technology application; charge injection atomization. The technology permits standard liquid combustion fuels, and any other electrically insulating liquid, to be electrically atomized and dispersed efficiently.
John Shrimpton
Backmatter
Metadata
Title
Charge Injection Systems
Author
John Shrimpton
Copyright Year
2009
Publisher
Springer Berlin Heidelberg
Electronic ISBN
978-3-642-00294-6
Print ISBN
978-3-642-00293-9
DOI
https://doi.org/10.1007/978-3-642-00294-6

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