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.
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    Highly turbocharging a restricted two cylinder small engine: turbocharger development
    Attard, William ; Watson, Harry ; Konidaris, Steven (SAE Technical Paper Series, 2007)
    This paper describes the turbocharger development of a restricted 430 cm3 odd firing two cylinder engine. The downsized test engine used for development was specifically designed and configured for Formula SAE, SAE’s student Formula race-car competition. A well recognised problem in turbocharging Formula SAE engines arises from the rules, which dictate that the throttle and air intake restrictor must be on the suction side of the compressor. As a consequence of upstream throttling, oil from the compressor side seal assembly is drawn into the inlet manifold. The development process used to solve the oil consumption issue for a Garrett GT-12 turbocharger is outlined, together with cooling and control issues. The development methodology used to achieve high pressure ratio turbocharging is discussed, along with exhaust manifold development and operating limitations. This includes experimental and modeling results for both pulse and constant pressure type turbocharging. The engine completed extensive static and transient testing with no turbocharger issues after initial development. Peak values of 25 bar brake mean effective pressure (BMEP) were recorded while running on pump gasoline.
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    Development of a 430cc constant power engine for formula SAE competition
    Attard, William ; Watson, Harry (SAE Technical Paper Series, 2006)
    This paper describes the design and development of an engine with constant power for SAE’s student Formula race-car competition, allowing the avoidance of gear shifting for much of the Autocross event. To achieve constant power for over 50% of the speed range, turbocharging was adopted with a boost pressure ratio of 2.8 at mid-range speeds and applied to an engine capacity of 430 cc. This engine was specifically designed and configured for the purpose, being a twin cylinder in-line arrangement with double overhead camshafts. Most of the engine components were specially cast or machined from billets. The capacity was selected to minimise frictional losses and thus increase delivered power along with dry sump lubrication and a three speed gear box. The engine manifolds and plenums were designed using a CAE application and proved to be well suited to the task resulting in excellent agreement between predicted and actual performance. One of the major challenges of the experimental development was overcoming the turbocharger oil consumption under throttled operation at part load conditions and at full power when the FSAE restrictor is choked. For the 2004 Australian competition the engine was run with slightly reduced mid speed power to avoid excessive use of the traction control system and was very competitive finishing first in the fuel economy event.
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    Highly turbocharging a restricted, odd fire, two cylinder small engine: design, lubrication, tuning and control
    Attard, William ; Watson, Harry ; Konidaris, Steven (SAE Technical Paper Series, 2006)
    This paper describes the mechanical component design, lubrication, tuning and control aspects of a restricted, odd fire, highly turbocharged (TC) engine for Formula SAE competition. The engine was specifically designed and configured for the purpose, being a twin cylinder in-line arrangement with double overhead camshafts and four valves per cylinder. Most of the engine components were specially cast or machined from billets. A detailed theoretical analysis was completed to determine engine specifications and operating conditions. Results from the analysis indicated a new engine design was necessary to sustain highly TC operation. Dry sump lubrication was implemented after initial oil surge problems were found with the wet sump system during vehicle testing. The design and development of the system is outlined, together with brake performance effects for the varying systems. Tuning an odd fire engine with an intake restriction and upstream throttle location was explored together with varying injector locations and manifold geometry. To improve engine efficiency, turbocharging and specific engine downsizing were employed in conjunction with a lean burn strategy at low brake mean effective pressure (BMEP). This engine package and tuning strategy resulted in the Melbourne University Formula SAE vehicle being very successful in competition, finishing first in the fuel economy event at the 2004 Australasian competition. Peak BMEP values of 25 bar, believed to be the highest recorded for small engines on pump gasoline were also achieved.
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    Design and development of a gasketless cylinder head / block interface for an open deck, multi cylinder, highly turbocharged small engine
    Attard, William ; Watson, Harry ; Stryker, Peter (SAE Technical Paper Series, 2006)
    This paper describes the design and development of a gasketless interface, which was used successfully to couple an aluminium cylinder head to an open deck design cylinder block. The cylinder block was manufactured from aluminium, featuring shrink fit dry cast iron liners. Extensive CAE modelling was employed to implement the gasketless interface and thus avoid using a conventional metal or fiber based cylinder head gasket. The engine was specifically designed and configured for the purpose, being a 430 cm3, highly turbocharged (TC) twin cylinder in-line arrangement with double overhead camshafts and four valves per cylinder. Most of the engine components were specially cast or machined from billets. The new design removed the conventional head gasket and relied on the correct amount of face pressure generated by interference between the cylinder head and block to seal the interface. This had advantages in improving the structural integrity of the weak open deck design. Extensive FEM analysis determined the correct amount of interference needed for successful operation under all operating conditions. Extensive thermal analysis concluded that removing the conventional gasket had the advantage of improving the heat path between the cylinder head and block, as the gasket behaves as an insulator. The possibility of gasket failure due to abnormal combustion is also eliminated. The design proved successful in operation, withstanding knock amplitudes of 30 bar, in-cylinder pressures exceeding 100 bar and high combustion temperatures. The engine completed extensive static and transient testing with no interface problems after initial development, recording 25 bar brake mean effective pressure (BMEP) on pump gasoline.
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    Comparing the performance and limitations of a downsized formula SAE engine in normally aspirated, supercharged and turbocharged modes
    Attard, William ; Watson, Harry ; Konidaris, Steven ; Khan, Mohammad (SAE International Technical Paper, 2006)
    This paper compares the performance of a small two cylinder, 430 cm3 engine which has been tested in a variety of normally aspirated (NA) and forced induction modes on 98-RON pump gasoline. These modes are defined by variations in the induction system and associated compression ratio (CR) alterations needed to avoid knock and maximize volumetric efficiency (hVOL). These modes included: (A) NA with carburetion (B) NA with port fuel injection (PFI) (C) Mildly Supercharged (SC) with PFI (D) Highly Turbocharged (TC) with PFI. The results have significant relevance in defining the limitations for small downsized spark ignition (SI) engines, with power increases needed via intake boosting to compensate for the reduced swept volume. Performance is compared in the varying modes with comparisons of brake mean effective pressure (BMEP), brake power, hVOL, brake specific fuel consumption (BSFC) and brake thermal efficiency (hTH). The test engine used in experiments was specifically designed and configured for Formula SAE, SAE’s student Formula race-car competition. A downsized twin cylinder in-line arrangement was chosen, which featured double overhead camshafts and four valves per cylinder. Most of the engine components were specially cast or machined from billets. Experimental results showed BSFC or hTH values in the order of 240 g/kWh or 34% could be achieved. TC BMEP values in the region of 25 bar were also achieved, the highest recorded for small engines on pump gasoline [1]. The engine was installed into successive Melbourne University Racing (MUR) vehicles in 2003 and 2004, where it was very competitive, finishing first in the fuel economy event at the 2004 Australasian competition.
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    Combustion system development and analysis of a carbureted and PFI normally aspirated small engine
    Attard, William P. ; Toulson, Elisa ; Hamori, Ferenc ; Watson, Harry C. (SAE Japan & SAE International, 2009)
    This paper focuses on the combustion system development and combustion analysis results for a normally aspirated 0.43 liter small engine. The inline two cylinder engine used in experiments has been tested in a variety of normally aspirated modes, using 98-RON pump gasoline. Test modes were defined by alterations to the induction system, which included carburetion and port fuel injection fuel delivery systems. The results from this paper provide some insight into the combustion effects for small cylinder normally aspirated spark ignition engines. This information provides future direction for the development of smaller engines as oil prices fluctuate and CO2 emissions begin to be regulated. Small engine combustion is explored with a number of parametric studies, including a range of manifold absolute pressures up to wide open throttle, engine speeds exceeding 10,000 rev/min and compression ratios ranging from 9 to 13. Combustion system optimization through compression ratio development enabled the engine to achieve 37% brake thermal efficiency and 13 bar brake mean effective pressure. Hence, the test engine performance and efficiency results demonstrate that smaller bore engines can match or exceed typical larger bore engines found in passenger vehicles. However, this was only possible after compression ratio optimization to compensate for the higher levels of dissociation, friction and heat losses associated with the small cylinder size.
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    Combustion system development and analysis of a downsized highly turbocharged PFI small engine
    Attard, William P. ; Toulson, Elisa ; Hamori, Ferenc ; Watson, Harry C. (SAE Japan & SAE International, 2009)
    This paper provides some insight into the future direction for developing smaller capacity downsized engines, which will be needed to meet tight CO2 targets and the world’s future powertrain requirements. This paper focuses on the combustion system development and combustion analysis results for a downsized 0.43 liter highly turbocharged engine. The inline two cylinder engine used in experiments was specifically designed and constructed to enable 25 bar BMEP. Producing this specific output is one way forward for future passenger vehicle powertrains, enabling in excess of 50% swept capacity reduction whilst maintaining comparable vehicle performance. Previous experiments and analysis have found that the extent to which larger engines can be downsized while still maintaining equal performance is combustion limited. Hence, small engine combustion is explored over a number of parametric studies, including a range of manifold absolute pressures up to 270 kPa, engine speeds exceeding 10,000 rev/min and compression ratios ranging from 9 to 13. Experimental results indicate that small engine combustion hurdles can be overcome to reliably extend the specific output to 25 bar BMEP. This is believed to be the highest recorded specific output for a non-intercooled small spark ignition PFI engine operating on pump gasoline. However, the boosted combustion effects illustrate that the thermal efficiency is highly dependent on the combustion efficiency, which deteriorates rapidly if uncontrolled combustion, specifically knock in the end-gas region is encountered. However, with this combustion system design strategy, potential drive cycle fuel consumption improvements in excess of 20% are still achievable.