1. High Voltage Jet Fuel Atomization
Vigneshwaran Selvaraju1, Jean Hertzberg1, Daniel Bosnich1, Scott Oubre1 , Albin Gasiewski2
1 - Department of Mechanical Engineering, University of Colorado, Boulder
2 - Department of Electrical Engineering, University of Colorado, Boulder
Introduction:
Methods:
Conclusion:Results:
Acknowledgements:
High voltage DC current is injected
through a stainless steel needle
into the JP-8 jet fuel upstream
of the spray orifice.
The experiment is run in a
nitrogen environment to
prevent combustion.
The jet is back-lit by
a 5 ns laser pulse
which is decorrelated
using a colloidal medium [2]
(milk) to create a uniform field.
A range of flowrates from
0.2 to 0.5 ml/s through a 200 µm
orifice have been studied at up to
20 kV.
This work has been partially supported
by UROP and the US Army. Thanks to
Prof. James Nabity, TDA and previous
undergraduate research groups for the
design and construction of the
apparatus.
 The above images were taken under the following conditions:
flow rate: 0.2 ml/s, needle distance from orifice: 5mm,
magnification: 90 X, imaging distance from orifice plane: 75mm.
 Figure 1 shows the un-charged jet breaking up due to Plateau-Rayleigh
instability. The falling stream accelerates and narrows until surface tension
causes it to break up into droplets which continue to separate as they fall.
 Figure 2 shows the droplets in a charged stream breaking up and repelling
each other primarily along the axis of the jet. This is due to the surface
charge on droplets in addition to Plateau-Rayleigh instability.
 Figure 3 shows transverse dispersion of droplets, which occurs sporadically.
This is due to the increased surface charge density. Additional explanations
for this behavior are being sought.
 Figure 4 is a time averaged (1 second) picture, showing how the excited
stream bends slightly and wanders.
 By comparing Figures 1 and 2 it can be observed that applying voltage
creates a more uniform axial distribution of droplets.
 Time averaged data shows an increase in radial spread with voltage.
Fig 1: 0 kV Fig 2: 13 kV Fig 3: 15kV Fig 4: 15kV
References:
[1] Rigit, A. R. H & Shrimpton, J. S. - Electrical
performance of charge injection – Atomization
& Sprays, vol . 6, pp. 401-419(2006)
[2] Falko Riechert, Georg Bastian, and Uli
Lemmer - Laser speckle reduction via colloidal-
dispersion-filled projection screens Applied
Optics, Vol. 48, Issue 19, pp. 3742-3749 (2009)
An electrostatic
spray augmentation
method has been
proposed to
broaden the range of
fuels that can be
used in
reciprocating engines.
The spray properties
are being studied by altering the applied
voltage and flow rate. Flow visualization
techniques are being used to understand
the physics of the liquid stream breakup.
High
Voltage DC
Jet
Fuel ->
Spray
200 µm
Orifice
It was observed that by applying voltage to
a free stream of jet fuel, the stream began
to wander about the vertical axis of flow.
Although the time averaged images show a
spray, the time resolved images show a
single stream of droplets except in 15% of
images.
The single stream of droplets quickly
changes axes to make it look like a spray.
The findings seem to agree with the results
of the literature [1].
Study of the electrostatically enhanced
spray is ongoing.
Future work will involve quantifying the
surface charge density, PIV measurement of
droplets, and simulations .
(High voltage DC spray
AJ Shrimpton [1])