This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Combustion Chamber Deposits and Knock in a Spark Ignition Engine - Some Additive and Fuel Effects
Annotation ability available
Sector:
Language:
English
Abstract
A four-cylinder engine with a slice between the head and the block carrying instrumented plugs has been used to study the growth of combustion chamber deposits and knock. Deposit thicknesses vary substantially at different locations, the thickness generally being greatest at the coolest surfaces. If a dirty engine is run on a low-boiling-point fuel such as a primary reference fuel, deposits are removed and octane requirement is reduced rapidly. Of the head deposits, those in the cooler squish region where the end gas is likely to be situated affect knock more than the deposits in the hotter regions. Different fuel additives have different effects on deposits in different areas. For instance, an additive might cause a substantial increase in deposit thickness in the hotter areas and a slight increase in total deposit weight but can control deposits in the cooler squish regions and so reduce octane requirement increase (ORI) compared to the base fuel alone. Different fuels respond to the same deposits to different extents in terms of knock. Knock ratings can depend on the fuel the deposits have been exposed to just prior to the rating. Low octane, low-boiling-point fuels appear to make the engine more prone to knock probably by facilitating the release of pro-knock species trapped in the deposits. This “chemical” ORI can be alleviated by running the engine on a full boiling range gasoline for a short time.
Recommended Content
Citation
Kalghatgi, G., "Combustion Chamber Deposits and Knock in a Spark Ignition Engine - Some Additive and Fuel Effects," SAE Technical Paper 962009, 1996, https://doi.org/10.4271/962009.Also In
References
- Kalghatgi, G.T. “Deposits in Gasoline Engines - A Literature Review” SAE Paper No. 902105 1990
- Kalghatgi, G.T. “Combustion Chamber Deposits in Spark Ignition Engines - A Literature Review” SAE Paper No. 952443 1995
- “Proceedings of the CRC Workshop on Combustion Chamber Deposits, Orlando, Florida, November 15-17, 1991.” CRC Inc. 219 Perimeter Center Parkway, Suite 400, Atlanta, GA 30346, U.S.A.
- Kalghatgi, G.T. McDonald, C.R. Hopwood, A.B. “An experimental study of combustion chamber deposits and their effects in a spark-ignition engine” SAE Paper No. 950680 1995
- Cheng, S.S. “A physical mechanism for deposit formation in a combustion chamber” SAE Paper No. 9418292 SAE SP-1094 1994
- Hayes, T.K. White, R.A. Peters, J.E. “The in-situ measurement of thermal diffusivity of combustion chamber deposits in a spark ignition engine” SAE Paper No. 920513 1992
- Bert, J.A. Gething, J.A. Hansell, T.J. Newhall, H.K. Peyla, R.J. Voss, D.A. “A gasoline additive concentrate removes combustion chamber deposits and reduces vehicle octane requirements” SAE Paper No. 831709 1983
- Megnin, M.K. Choate, P.J. “Combustion chamber deposit measurement technique” SAE Paper No. 940346 1994
- Woodyard, M.E. “Gasoline additive and deposit effects on the road and a Ford 2.3L engine test” SAE Paper No. 952446 SAE SP-1118 1995
- Owens, J.P. “Comparison of cylinder head deposit thickness and weight data in fleet and dynamometer testing” SAE Paper No. 952448 SAE SP-1118 1995
- Benson, J.D. “Some factors which affect octane requirement increase” SAE Paper No. 750933 1975
- Brussovansky, S. Heywood, J.B. Keck, J.C. “Predicting the effects of air and coolant temperature, deposits, spark timing and speed on knock in spark ignition engines” SAE Paper No. 922324 1992