The influence of liquid fuel properties on atomisation remains an open question. The
droplet sizes in sprays from atomisers operated with different fuels may be modified
despite the small changes of the liquid properties. This paper examines experimentally
the development of a liquid jet injected from a plain orifice in order to evaluate
changes in its behaviour due to modifications of the liquid properties, which may
influence the final atomisation characteristics. Two aviation kerosenes with similar,
but not identical physical properties are considered, namely standard JP8 kerosene as
the reference fuel and bio-derived Hydro-processed Renewable Jet (HRJ) fuel as an
alternative biofuel. The corresponding density, dynamic viscosity, kinematic viscosity
and surface tension change by about +5%, -5%, -10% and +5% respectively, which
are typical for ‘drop-in’ fuel substitution. Three aspects of the liquid jet behaviour are
experimentally considered. The pressure losses of the liquid jet through the nozzle are
examined in terms of the discharge coefficient for different flowrates. The
morphology of the liquid jet is visualised using high magnification Laser Induced
Fluorescence (LIF) imaging. Finally, the temporal development of the liquid jet
interfacial velocity as a function of distance from the nozzle exit is measured from
time-dependent motion analysis of dual-frame LIF imaging measurements of the jet.
The results show that for the small changes in the physical properties between the
considered liquid fuels, the direct substitution of fuel did not result in a drastic change
of the external morphology of the fuel jets. However, the small changes in the
physical properties modify the interfacial velocities of the liquid and consequently the
internal jet velocity profile. These changes can modify the interaction of the liquid jet
with the surroundings, including air flows in coaxial or cross flow atomisation, and
influence the atomisation characteristics during changes of liquid fuels.