scholarly journals Qualitative analysis of the minimum flow rate of a cone-jet of a very polar liquid

2017 ◽  
Vol 816 ◽  
pp. 428-441 ◽  
Author(s):  
F. J. Higuera
Keyword(s):  
Electric Field ◽  
Flow Rate ◽  
Scaling Laws ◽  
Shear Stresses ◽  
Minimum Flow ◽  
Electrostatic Atomization ◽  
Finite Electrical Conductivity ◽  
Order Of Magnitude ◽  
Induced Flow ◽  
Minimum Flow Rate

Electrostatic atomization of a liquid of finite electrical conductivity in the so-called cone-jet regime relies on the electric shear stresses that appear in a region of the liquid surface when a meniscus of the liquid is subjected to an intense electric field. An order of magnitude analysis is used to describe the flow induced by these stresses, which drive the liquid of the meniscus into a jet that issues from the tip of the meniscus and breaks into droplets at some distance from it. When the dielectric constant of the liquid is large, the electric shear stresses extend into the jet and cause a depression that sucks liquid from the meniscus. The induced flow rate is estimated and shown to represent approximately the minimum flow rate at which a cone-jet can be established. It is argued that the meniscus can be stabilized by the electric field that the charge of the jet induces on it. This stabilizing mechanism weakens when the flow rate supplied to the meniscus decreases, and its failure may determine an alternative minimum flow rate for the cone-jet regime. The instability of the jet and existing scaling laws for the size of the spray droplets are discussed.

The steady cone-jet mode of electrospraying close to the minimum volume stability limit

2018 ◽  
Vol 857 ◽  
pp. 142-172 ◽  
Author(s):  
A. Ponce-Torres ◽  
N. Rebollo-Muñoz ◽  
M. A. Herrada ◽  
A. M. Gañán-Calvo ◽  
J. M. Montanero
Keyword(s):  
Transition Region ◽  
Electric Fields ◽  
Flow Rate ◽  
Scaling Laws ◽  
Stability Limit ◽  
Dominant Mode ◽  
Minimum Flow ◽  
Local Character ◽  
Stabilizing Effect ◽  
Minimum Flow Rate

We study both numerically and experimentally the steady cone-jet mode of electrospraying close to the stability limit of minimum flow rate. The leaky dielectric model is solved for arbitrary values of the relative permittivity and the electrohydrodynamic Reynolds number. The linear stability analysis of the base flows is conducted by calculating their global eigenmodes. The minimum flow rate is determined as that for which the growth factor of the dominant mode becomes positive. We find a good agreement between this theoretical prediction and experimental values. The analysis of the spatial structure of the dominant perturbation may suggest that instability originates in the cone-jet transition region, which shows the local character of the cone-jet mode. The electric relaxation time is considerably smaller than the residence time of a fluid particle in the cone-jet transition region (defined as the region where the surface and bulk intensities are of the same order of magnitude) except for the high-polarity case, where these characteristic times are commensurate with each other. The superficial charge is not relaxed within the cone-jet transition region except for the high-viscosity case, because significant inner electric fields arise in the cone-jet transition region. However, those electric fields are not large enough to invalidate the scaling laws that do not take them into account. Viscosity and polarization forces compete against the driving electric shear stress in the cone-jet transition region for small Reynolds numbers and large relative permittivities, respectively. Capillary forces may also play a significant role in the minimum flow rate stability limit. The experiments show the noticeable stabilizing effect of the feeding capillary for diameters even two orders of magnitude larger than that of the jet. Stable jets with electrification levels higher than the Rayleigh limit are produced. During the jet break-up, two consecutive liquid blobs may coalesce and form a bigger emitted droplet, probably due to the jet acceleration. The size of droplets exceeds Rayleigh’s prediction owing to the stabilizing effect of both the axial electric field and viscosity.

The minimum flow rate of electrosprays in the cone-jet mode

2019 ◽  
Vol 876 ◽  
pp. 553-572 ◽  
Author(s):  
Manuel Gamero-Castaño ◽  
M. Magnani
Keyword(s):  
Dielectric Constant ◽  
Reynolds Number ◽  
Flow Rate ◽  
Numerical Solutions ◽  
Viscous Stress ◽  
Flow Rates ◽  
Minimum Flow ◽  
Electric Stress ◽  
Work Done ◽  
Minimum Flow Rate

Stable electrospraying in the cone-jet mode is restricted to flow rates above a minimum, and understanding the physics of this constraint is important to improve this atomization technique. We study this problem by measuring the minimum flow rate of electrosprays of tributyl phosphate and propylene carbonate at varying electrical conductivity $K$ (all other physical properties such as the density $\unicode[STIX]{x1D70C}$, surface tension $\unicode[STIX]{x1D6FE}$ and viscosity $\unicode[STIX]{x1D707}$ are kept constant and equal to those of the pure liquids), and through the analysis of numerical solutions. The experiments show that the dimensionless minimum flow rate is a function of both the dielectric constant $\unicode[STIX]{x1D700}$ of the liquid and its Reynolds number, $Re=(\unicode[STIX]{x1D70C}\unicode[STIX]{x1D700}_{o}\unicode[STIX]{x1D6FE}^{2}/\unicode[STIX]{x1D707}^{3}K)^{1/3}$. This result is unexpected in the light of existing theories which, for the conditions investigated, predict a minimum flow rate that depends only on $\unicode[STIX]{x1D700}$ and/or is marginally affected by $Re$. The experimental dependency on the Reynolds number requires the viscous stress to be a factor in the determination of the minimum flow rate. However, the numerical solutions suggest that a balance of opposing forces including the fixing viscous stress, which at decreasing flow rates may lower the acceleration of the flow to the point of making it unstable, is unlikely to be the cause. An alternative mechanism is the significant viscous dissipation taking place in the transition from cone to jet, and which at low flow rates cannot be supplied by the work done by the tangential electric stress in the same area. Instead, mechanical energy injected into the system farther downstream must be transferred upstream where dissipation predominantly takes place. This mechanism is supported by the balance between the energy dissipated and the work done by the electric stress in the transition from cone to jet, which yields a relationship between the minimum flow rate, the Reynolds number and the dielectric constant that compares well with experiments.

A Mechanistic Study on Minimum Flow Rate for the Continuous Removal of Liquids from Gas Wells

2012 ◽  
Vol 30 (2) ◽  
pp. 122-132 ◽  
Author(s):  
W. Zhibin ◽  
L. Yingchuan ◽  
L. Zhongneng ◽  
Z. Haiquan ◽  
L. Yonghui
Keyword(s):  
Flow Rate ◽  
Mechanistic Study ◽  
Gas Wells ◽  
Minimum Flow ◽  
Minimum Flow Rate

Analysis and Prediction of Minimum Flow Rate for the Continuous Removal of Liquids from Gas Wells

1969 ◽  
Vol 21 (11) ◽  
pp. 1475-1482 ◽  
Author(s):  
R.G. Turner ◽  
M.G. Hubbard ◽  
A.E. Dukler
Keyword(s):  
Flow Rate ◽  
Gas Wells ◽  
Minimum Flow ◽  
Minimum Flow Rate

scholarly journals Modelling Minimum Flow Rate Required for Unloading Liquid in Gas Wells

2020 ◽  
Author(s):  
Adesina Fadairo ◽  
Gbadegesin Adeyemi ◽  
Temitope Ogunkunle ◽  
Oreoluwa Lawal ◽  
Olugbenga Oredeko
Keyword(s):  
Flow Rate ◽  
Gas Wells ◽  
Minimum Flow ◽  
Minimum Flow Rate

The minimum flow rate scaling of Taylor cone-jets issued from a nozzle

2014 ◽  
Vol 104 (2) ◽  
pp. 024103 ◽  
Author(s):  
William J. Scheideler ◽  
Chuan-Hua Chen
Keyword(s):  
Flow Rate ◽  
Taylor Cone ◽  
Minimum Flow ◽  
Minimum Flow Rate

scholarly journals Electric current of an electrified jet issuing from a long metallic tube

2011 ◽  
Vol 675 ◽  
pp. 596-606 ◽  
Author(s):  
F. J. HIGUERA
Keyword(s):  
Electric Field ◽  
Electric Current ◽  
Flow Rate ◽  
Surface Current ◽  
Linear Increase ◽  
Current Transfer ◽  
Metallic Tube ◽  
Electrically Conducting ◽  
Transfer Region ◽  
Order Of Magnitude

This paper presents an analysis of the transport of electric current in a jet of an electrically conducting liquid discharging from a metallic tube into a gas or a vacuum, and subject to an electric field due to a high voltage applied between the tube and a far electrode. The flow, the surface charge and the electric field are computed in the current transfer region of the jet, where conduction current in the liquid becomes surface current due to the convection of electric charge accumulated at its surface. The electric current computed as a function of the flow rate of the liquid injected through the tube increases first as the square root of this flow rate, levels to a nearly constant value when the flow rate is increased and finally sets to a linear increase when the flow rate is further increased. The current increases linearly with the applied voltage at small and moderate values of this variable, and faster than linearly at high voltages. The characteristic length and structure of the current transfer region are determined. Order-of-magnitude estimates for jets which are only weakly stretched by the electric stresses are worked out that qualitatively account for some of the numerical results.

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