Mechanical Engineering - Research Publications

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    The feasibility of downsizing a 1.25 liter normally aspirated engine to a 0.43 liter highly turbocharged engine
    Attard, William ; Konidaris, Steven ; Toulson, Elisa ; Watson, Harry (SAE Technical Paper Series, 2007)
    In this paper, performance, efficiency and emission experimental results are presented from a prototype 434 cm3, highly turbocharged (TC), two cylinder engine with brake power limited to approximately 60 kW. These results are compared to current small engines found in today’s automobile marketplace. A normally aspirated (NA) 1.25 liter, four cylinder, modern production engine with similar brake power output is used for comparison. Results illustrate the potential for downsized engines to significantly reduce fuel consumption while still maintaining engine performance. This has advantages in reducing vehicle running costs together with meeting tighter carbon dioxide (CO2) emission standards. Experimental results highlight the performance potential of smaller engines with intake boosting. This is demonstrated with the test engine achieving 25 bar brake mean effective pressure (BMEP). Results are presented across varying parameter domains, including engine speed, compression ratio (CR), manifold absolute pressure (MAP) and lambda (λ). Engine operating limits are also outlined, with spark knock highlighted as the major limitation in extending the operating limits for this downsized engine.
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    Compression ratio effects on performance, efficiency, emissions and combustion in a carbureted and PFI small engine
    Attard, William ; Konidaris, Steven ; Hamori, Ferenc ; Toulson, Elisa ; Watson, Harry (SAE Technical Paper Series, 2007)
    This paper compares the performance, efficiency, emissions and combustion parameters of a prototype two cylinder 430 cm3 engine which has been tested in a variety of normally aspirated (NA) modes with compression ratio (CR) variations. Experiments were completed using 98-RON pump gasoline with modes defined by alterations to the induction system, which included carburetion and port fuel injection (PFI). The results from this paper provide some insight into the CR effects for small NA spark ignition (SI) engines. This information provides future direction for the development of smaller engines as engine downsizing grows in popularity due to rising oil prices and recent carbon dioxide (CO2) emission regulations. Results are displayed in the engine speed, manifold absolute pressure (MAP) and CR domains, with engine speeds exceeding 10,000 rev/min and CRs ranging from 9 to 13. Combustion analysis is also included, allowing mass fraction burn (MFB) comparison. Experimental results showed minimum brake specific fuel consumption (BSFC) or maximum brake thermal efficiency (nTH) values in the order of 220 g/kWh or 37% could be achieved. A maximum brake mean effective pressure (BMEP) of 13 bar was also recorded at 8000 rev/min.