|dc.description.abstract||This thesis presents the work done within the PhD research project focusing on the utilisation
of plant oils in Common Rail (CR) diesel engines. The work scope included
fundamental experimental studies of rapeseed oil (RSO) in comparison to diesel fuel,
the feasibility analysis of diesel substitution with various plant oils, the definition and
implementation of modifications of a common rail injection system and future work recommendations
of possible changes to the injection system.
It was recognised that neat plant oils can be considered as an alternative substitute
for diesel fuel offering a natural way to balance the CO2 emissions. However, due to the
differences between diesel and plant oils, such as density, viscosity and surface tension,
the direct application of plant oils in common rail diesel engines could cause degradation
of the injection process and in turn adversely affect the diesel engine’s performance. RSO
was chosen to perform the spray characterisation studies at various injection pressures and
oil temperatures under conditions similar to the operation of the common rail engine. High
speed camera, Phase Doppler Anemometry and Malvern laser techniques were used to
study spray penetration length and cone angle of RSO in comparison to diesel. To study
the internal flow inside the CR injector the acoustic emission technique was applied.
It was found that for oil temperatures below 40°C the RSO viscosity, density and
surface tension are higher in comparison to diesel, therefore at injection pressures around
37.50 MPa the RSO spray is not fully developed. The spray penetration and cone angle at
these spray conditions exhibit significant spray deterioration.
In addition to the lab experiments, KIVA code simulated RSO sprays under CR conditions.
The KH-RT and RD breakup models were successfully applied to simulate the
non-evaporating sprays corresponding to the experimental spray tests and finally to predict
real in-cylinder injection conditions. Numerical results showed acceptable agreement with
the experimental data of RSO penetration.
Based on experimental and numerical results it was concluded that elevated temperature
and injection pressure could be the efficient measures to overcome operational obstacles
when using RSO in the CR diesel engine. A series of modifications of low- and highpressure
loops was performed and experimentally assessed throughout the engine tests.
The results revealed that the modifications allowed to run the engine at the power and
emission outputs very close to diesel operation. However, more fundamental changes were
suggested as future work to ensure efficient and trouble-free long-term operation. It is
believed that these changed should be applied to meet Euro IV and V requirements.||en_US