Taylor, Mark Stewart (2016) Effect of compression ratio on the performance, emissions and efficiency of E-85 Ethanol-Unleaded petrol in a homogenous charge, spark ignition engine. Coursework Masters thesis, University of Southern Queensland. (Unpublished)
Abstract
High ethanol blend bio-fuels such as E-85 have the ability to reduce dependence on fossil
fuels and extend the useful life of existing oil reserves. However the much lower latent
heat of evaporation and corresponding lower energy output means that existing
homogenous charge spark ignition (HCSI) engines require modifications to operate
effectively on this fuel source. This study utilised a variable compression engine to
determine the effect compression ratio has on the specific output of E-85 and therefore
determine an optimum range to balance performance, thermal efficiency and emissions.
Ethanol is a renewable resource produced from the fermentation and distillation of glucose
which is readily available around the world. Previous research has shown that ethanol
blended fuels operating with an optimised compression ratio can produce higher specific
output with fewer emissions than pure unleaded petrol (Yucesu H.S.et al 2006).
A G.U.N.T CT300 11 kW variable compression ratio (VCR) single cylinder engine was
operated at compression ratios from 8:1 through to 10:1 on both E-85 and Unleaded petrol.
Three runs with different amounts of ignition timing were made on each fuel at each
compression ratio. Engine performance, energy balance data and the exhaust gas
composition was collected using various sensors, an exhaust calorimeter and a five gas
analyser. From the results obtained a clear comparison of the optimum running conditions
at each data point is presented and relationships developed for the designated variables.
Key outcomes were to identify if E-85 biofuel is a viable alternative fuel in an optimised
engine. The limited data has shown a more linear torque curve for E-85 than petrol with
significantly increased NOx emissions. After completing testing from 8:1 CR to 10:1 CR,
testing was cut short due to an issue with the G.U.N.T. VCR engine. However the results
show a clear trend of higher performance with increased compression ratio and
significantly lower brake specific fuel consumption for E-85 when operated slightly leaner
( = 1.1) than expected while producing similar power to petrol. Additional testing will
be required to gather the remaining data once the engine is fully operational.
The primary outcome of this research project is that higher compression ratios increase the
power and efficiency of E-85 blended biofuel. However as the compression ratio increases
so does the concentration of NOx emissions and at lean mixtures the levels are much
higher than for petrol. To take advantage of the lower carbon emissions and better BSFC
of lean E-85 biofuel mixtures the high NOx must be addressed. If this can be addressed E
85 biofuel may be a viable sustainable alternative fuel.
Mitigating this increase in noxious NOx emissions may be achieved through the use of a
selective catalytic reduction (SCR) which is outside the scope of this project but may be an
area for further research.
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| Item Type: | Thesis (Non-Research) (Coursework Masters) |
|---|---|
| Item Status: | Live Archive |
| Additional Information: | Current UniSQ staff and students can request access to this thesis. Please email research.repository@unisq.edu.au with a subject line of SEAR thesis request and provide: Name of the thesis requested and Your name and UniSQ email address. |
| Faculty/School / Institute/Centre: | Current - Faculty of Health, Engineering and Sciences - No Department (1 Jul 2013 -) |
| Supervisors: | Baker, Paul |
| Qualification: | Master of Engineering Sciences (Mechanical Engineering) |
| Date Deposited: | 14 Jul 2026 04:50 |
| Last Modified: | 14 Jul 2026 04:50 |
| Uncontrolled Keywords: | ethanol, bio-fuels, blend bio-fuels, |
| URI: | https://sear.unisq.edu.au/id/eprint/53226 |
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