UWE Bristol Engineering showcase 2015

Darren Millwood
MEng Mechanical Engineering
Project Supervisor
Neil Larsen
The determination of the performance characteristics of MPW derived
fuel in a high speed diesel engine – Part B
Introduction
For the duration of this research, a company called
Recycling Technologies Ltd will be collaborated
with. They have developed a process that will aim
to address some of today’s environmental issues,
by taking the vast amounts of waste plastic
generated in society, and recovering the dormant
energy within by way of pyrolysis. The result is a
diesel fuel substitute that can be used to power a
diesel engine, in this case, coupled to a generator
as part of a combined heat and power (CHP)
system. Conversion of waste plastic into fuel,
whilst still vastly understudied, is not an entirely
new concept, and competition companies exist; it
is the application into a CHP unit that is unique.
Previous work – Testing facility and DoE
Previous work conducted during Part A focused on
the design and specification of a bespoke testing
facility within which to conduct experimentation
on the waste plastic fuel; this consisted of various
forms of instrumentation in order to collect data
pertaining to the follow engine performance
characteristics:
• engine emissions output (unburnt
hydrocarbons and oxides of nitrogen;
• engine specific fuel consumption;
• engine speed; and
• fuel injection pressure.
Experimental results
Predictions were made based on the reviewed
literature. These were:
• HC output would increase as diesel content is
reduced;
• NOx production would decrease as diesel
content is reduced;
• specific fuel consumption would increase;
• injection pressures would decrease; and
• engine speed would decrease.
Summary
There is a large push within modern society to reduce
the human impact on the environment. This includes
energy consumed, the amount of waste generated,
and the level of pollution created. Recycling
Technologies Ltd are a new company aiming to
address some of these issues by way of utilising
waste plastic as a derivative fuel for a diesel engine.
Therefore, this research aims to characterise the
performance of this fuel in order to determine
whether it is both an economically and
environmentally viable future alternative to
traditional diesel.
Objectives
The project objectives are as follows:
• quantify the effect of the fuel on specific fuel
consumption, emissions, injection pressures, and
engine speed;
• fit approximate models to the data using
statistical analysis techniques;
• determine the optimal temperature and
compositional percentage that can be utilised;
• make final conclusions as to the viability of the
fuel.
However, the downside to method employed by
Recycling Technologies Ltd is that the
implementation of the fuel is difficult, not only
because it is unusable in its raw form, but also
because it contains long chain hydrocarbons,
meaning that its combustion characteristics may
not suit the operating conditions provided by a
high speed diesel engine, preferable to slower
diesel engines due to their cost. The success of this
venture lies almost exclusively in how well the new
fuel will perform; this will be the focus of this
research, such that its viability as a future,
sustainable energy method can be successfully
determined.
Further work was conducted into the experimental
methods to be used in order to gather the
required data in such a way that was both efficient
and facilitated the appropriate analysis of the
results realised; the central composite design was
decided upon, with the contributing inputs being
the percentage mix between diesel and the mixed
plastic waste fuel, and the temperature at which it
was injected into the engine.
All predictions were correct, except for injection
pressure, which increased. Approximate models
were fitted to the data with statistical analysis
techniques; this showed that the injection
temperature was not a significant contributor to
the recorded outputs. It was also found that the
best trade-off in order to minimise all emissions
outputs and specific fuel consumption was at a
35/65 mix of waste plastic fuel with diesel. Overall,
future viability was proven, however much
development is still required.
Conclusion
Waste plastic fuel is certainly a viable product
for the future. Whilst there were undesirable
increases in certain engine responses, these
were not observed to be over a reasonable
limit during the experiments conducted, and
with further development, vast
improvements are likely to be made. Future
cost reductions are also likely with increased
development due to improved production
efficiency and greater product demand over
time.