The Feasibility of Downsizing a 1.25 Liter Normally Aspirated Engine to a 0.43 Liter Highly Turbocharged Engine

This paper provides some insight into the future direction for developing smaller capacity downsized engines, which will be needed to meet tight CO 2 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 endgas region is encountered. However, with this combustion system design strategy, potential drive cycle fuel consumption improvements in excess of 20% are still achievable.

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Combustion System Development and Analysis of a Carbureted and PFI Normally Aspirated Small Engine

Attard¹,

Toulson²,

Hamori³

et al. 2010

SAE Technical Paper Series

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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 CO 2 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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The Feasibility of Downsizing a 1.25 Liter Normally Aspirated Engine to a 0.43 Liter Highly Turbocharged Engine

Cited by 6 publications

References 26 publications

Gas Assisted Jet Ignition of Ultra-Lean LPG in a Spark Ignition Engine

Gas Assisted Jet Ignition of Ultra-Lean LPG in a Spark Ignition Engine

Combustion System Development and Analysis of a Downsized Highly Turbocharged PFI Small Engine

Combustion System Development and Analysis of a Carbureted and PFI Normally Aspirated Small Engine

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