The Effects of Engine Variables and Exhaust Gas Recirculation on Emissions, Fuel Economy, and Knock-Part II

Morgan, C. R.; Hetrick, S. S.

doi:10.4271/760198

Cited by 7 publications

(2 citation statements)

References 6 publications

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“…With moderate levels of EGR (10-15%), the reduction in end-gas reactivity outweighed the slower flame-front propagation, and hence the compression ratio could be raised and Brake-Specific Fuel Consumption (BSFC) improved, as described by Hodges [139] of Rensselaer Polytechnic Institute. EGR in combination with lean AFRs was also being investigated by Morgan [140] of Mobil Research and Development Corp., but led to HC increases. Secondary air introduction into the exhaust system was found to be effective in reducing HC emissions, but only for stoichiometric or rich mixtures.…”

Section: The 1970s: Oil Shortages Emissions Control and Unleaded Fuelsmentioning

confidence: 99%

Knock: A Century of Research

Corrigan¹,

Fontanesi²

2021

SAE Int. J. Engines

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Knock is one of the main limitations on increasing spark-ignition (SI) engine efficiency. This has been known for at least 100 years, and it is still the case today. Knock occurs when conditions ahead of the flame front in an SI engine result in one or more autoignition events in the end gas. The autoignition reaction rate is typically much higher than that of the flame-front propagation. This may lead to the creation of pressure waves in the combustion chamber and, hence, an undesirable noise that gives knock its name. The resulting increased mechanical and thermal loading on engine components may eventually lead to engine failure. Reducing the compression ratio lowers end-gas temperatures and pressures, reducing end-gas reactivity and, hence, mitigating knock. However, this has a detrimental effect on engine efficiency.Automotive companies must significantly reduce their fleet carbon dioxide (CO 2 ) values in the coming years to meet targets resulting from the 2015 Paris Agreement. One path towards meeting these is through partial or full electrification of the powertrain. However, the vast majority of automobiles in the near future will still feature a gasoline-fueled SI engine; hence, improvements in combustion engine efficiency remain fundamental.As knock has been a key limitation for so long, there is a huge amount of literature on the subject. A number of reviews on knock have already been published, including in recent years. These generally concentrate on current understanding and status. The present work, in contrast, aims to track the progress of research on knock from the 1920s right through to the present day. It is hoped that this can be a useful reference for new and existing researchers of the subject and give further weight to occasionally neglected historical activity, which can still provide important insights today.

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Section: The 1970s: Oil Shortages Emissions Control and Unleaded Fuelsmentioning

confidence: 99%

Knock: A Century of Research

Corrigan¹,

Fontanesi²

2021

SAE Int. J. Engines

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“…The absolute value of specific HC emissions also decreases as the speed and load are increased. This is probably due to the higher exhaust temperatures which accompany higher speeds and loads (2,4,6).…”

Section: La Ementioning

confidence: 99%

Investigative study of engine limiting

Bechtold¹

1978

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An experimental study was conducted to determine the effect of cylinder cutout or "engine limiting" on fuel consumption and exhaust emissions for a current technology V-type 8-cylinder engine. Increases in energy conversion efficiency while operating with only 4 cylinders ranged from 10 to 40 pct compared to operation with 8 cylinders at the same power outputs. The speeds and loads chosen were representative of those required to operate a 4,500-lb vehicle at speeds up to 60 mph. Hydrocarbon emissions increased at low speed/ load points under 4 cylinder operation. An insignificant change in carbon monoxide emissions was observed while an increase in oxides of nitrogen emissions resulted at the higher speed/load points.

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