Diesel fuel and Diesel fuel with Water Emulsions Spray and Combustion Characterization
Abstract
The legislative demand to simultaneously reduce nitrogen oxide(s) emissions and
particulate matter emissions from compression ignition engines is proving difficult
to achieve in the real world. One promising strategy is the use of Diesel fuel emulsified
with water. There is little work concerning the e↵ect of emulsification on
fuel injection sprays. This work details an experimental campaign to characterize
non-vaporizing sprays of Diesel fuel and Diesel emulsions, with 10% and 20% water
by mass. Characterization of the fuel sprays has been done using: high speed
photography, applying focused shadowgraphy and a di↵used back-lighting technique
and; hydraulically using a force transducer placed 0.5mm from the injector nozzle
to measure spray momentum flux. All measurements have been made in an optically
accessible high pressure chamber filled with nitrogen, resulting in an ambient
gas density of 22.6 kg/m3 and 34.5 kg/m3, with injection pressures of 500, 700 and
1000bar used.
The images collected have been used to determine the spray cone angle, the tip
penetration and the tip velocity. The signal from the force transducer has been used
to determine spray momentum flux, instantaneous mass flow rate, dimensionless
nozzle coefficients and injection velocity. The injection pressure had no discernible
influence on the spray cone angle for the Diesel fuel sprays but did for the emulsified
fuels. Increasing the ambient density resulted in an increase in the spray cone angle
for Diesel fuel, this was not always the case for the emulsified fuel sprays. The spray
tip emerged from the nozzle and accelerated for a very short period after the start
of injection until a maximum velocity was reached.
The momentum flux for each fuel was almost the same for corresponding conditions.
Increasing the chamber gas density reduced the measured spray momentum.
The total mass of fuel injected for Diesel fuel was larger than for the emulsions
for the equivalent conditions and duration, although emulsions had a larger density
and viscosity. The emulsions had a higher injection velocity. The nozzle discharge
coefficient for Diesel was higher than for the emulsions. The velocities measured
hydraulically are much higher than the maximum tip velocities measured optically.
The study has been completed by some preliminary combustion studies of the
fuels in an optically accessible combustion chamber. The emulsion tested exhibited
much lower natural flame luminosity, used to determine the spatially integrated
natural luminosity of the flame which may be useful as a soot indicator. There was
no evidence that the microexplosion phenomenon was present in these tests.
Authors
Emberson, David RobertCollections
- Theses [4200]