UWE Bristol Engineering showcase 2015

Robert Hilliard
MEng Mechanical Engineering
Project Supervisor
Rohitha Weerasinghe
Micro-combustion Fuel cell Design
Difficulties of micro-combustion
• Close to wall flow means more losses of heat and other energy leading to
flame quenching
• Manufacturing with small tolerances can prove challenging
• Moving Parts involved in power generation are difficult to accommodate
• Laminar boundary flow dominates means adequate mixing hard to
achieve
Concept
The concept chosen to investigate is a Swiss-roll micro-combustor. Spiraling
the inlets together with the outlets means that heat can be recuperated and
so Reduces the effect of the heat losses to the wall. It also aids in mixing.
Project summary
The demand for portable power is ever
increasing, with devices requiring more
power that lasts longer. This project explores
an alternative to electrochemical battery cells
that utilizes the high energy density of
hydrocarbons. Combustion of hydrocarbons
release a large amount of energy, which has
been the foundation of many large scale
power processes throughout recent history.
Scaling traditional processes down comes
with its own problems and this project aims
to deal with them.
Temperature K
3000
2500
2000
1500
1000
500
0
Temperature against time
0 1 2 3 4 5 6
time (s)
Results
• The small temperature of the lines
show lots of heat can be transferred
back into the inlet
• Straight sections show eat transfer
follows a linear pattern
• Boundary conditions can be
treacherous as can be seen by the rise
in the outlet
Start up times are low which is
essential in portable applications
Centre
exit
Turbulence is induced in the
changing diameter of the
combustion chamber. Helps with
combustion
Project Objectives
• Choose an appropriate Design concept
that directly reduces micro-combustion
shortfalls
• Create a model for computational analysis
• Use sound Engineering reasoning to
validate and justify model results
Project Conclusion
In conclusion, it can be seen that the
challenges intrinsic to this technology are
many and tough to conquer. What can be
seen is that by spiralling flow paths together a
substantial amount of heat can be
recuperated and that this heat recuperation
follows a linear pattern for the most part.
With more work combustion can be modelled
so that the influence of a simulated spark has
less effect on the overall result.