Combined aerodynamic and electrostatic atomization of dielectric
liquid jets


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Abstract

The electrical and atomization performance of a
plane–plane charge injection atomizer using a dielectric
liquid, and operating at pump pressures ranging from 15 to
35 bar corresponding to injection velocities of up to 50 m/s,
is explored via low current electrical measurements, spray
imaging and phase Doppler anemometry. The work is
aimed at understanding the contribution of electrostatic
charging relevant to typical higher pressure fuel injection
systems such as those employed in the aeronautical, automotive
and marine sectors. Results show that mean-specific
charge increases with injection velocity significantly.

Introduction

Classical atomization
Typical pump pressures for current common rail Diesel
engine injection systems are of the order *103 bar
(Lefebvre 1989) with direct injection spark ignition engine
systems and gas turbines requiring *102 bar. This pump
pressure requirement is a system inefficiency, which is
manageable in larger power systems; however, there are
examples where smaller scale systems require the type of
atomization performance that turbulent primary atomization
provides, such as small internal combustion engines
less than 250 cc. In this paper, a method is explored to
enable primary atomization akin to turbulent conditions but
from liquid jets at relatively low pressure and under
hydrodynamically laminar conditions. Prior to discussing
this method, a brief review of break-up regimes and conventional
atomization is provided.

Conclusion

Spray imaging and PDA have revealed that electrostatic
charging of dielectric liquids is advantageous at pressures of
up to 35 bar. The device is capable of supplying up to
approximately 70% more spray-specific charge when compared
to low-pressure plane–plane systems.