This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Fuel Blend and Mixture Strength Effects on Autoignition Heat Release Rates and Knock Intensity in S.I. Engines
Annotation ability available
Sector:
Language:
English
Abstract
In general, the rate of heat release during combustion in a spark ignition engine, can have two components: one due to normal burning in a propagating flame, and another due to autoignition in the end gas. It has been possible to separate these two components by analysing the pressure trace of a single cylinder engine. From this, the volumetric autoignition heat release rate can be inferred and studied in some detail. To approximate this rate in an Arrhenius form presents difficulties, in so far as it is not possible to measure the temperature at the instant of maximum heat release rate, at the onset of knock. However, it was possible to measure end gas temperatures by the CARS technique prior to autoignition and then to estimate the temperature at the onset of autoignition by extrapolation. Estimation of the temperature at the instant of maximum heat release rate has enabled kinetic parameters to be assigned in an Arrhenius expression for this rate over a range of temperatures. These parameters have been measured for fuels of different octane number, and for an aromatic and paraffinic fuel blend of identical MON at different mixture strengths. From these parameters and an earlier analysis of the coupling of pressure waves generated during autoignition with chemical reaction, the likelihood of a particular fuel blend giving rise to a particular mode of autoignition can be assessed. The most damaging mode is a developing detonation, which occurs at high values of the autoignition volumetric heal release rate. Such rates are higher for paraffinic than for aromatic fuels under the same conditions of temperature and pressure. As a result, a developing detonation is more likely for a paraffinic than for an aromatic fuel blend. For the paraffinic blends, the lower are both the octane number and the air/fuel ratio, the higher is the volumetric heal release rate, and hence also the knock intensity.
Recommended Content
| Technical Paper | Knock Intensity as a Function of Engine Rate of Pressure Change |
| Technical Paper | Methanol Preignition Temperature Behavior |
Authors
Citation
Bradley, D., Kalghatgi, G., and Golombok, M., "Fuel Blend and Mixture Strength Effects on Autoignition Heat Release Rates and Knock Intensity in S.I. Engines," SAE Technical Paper 962105, 1996, https://doi.org/10.4271/962105.Also In
References
- Heywood, J. B. Internal Combustion Engine Fundamentals McGraw Hill New York 1988
- Golombok, M. Kalghatgi, G. T. Tindall, A. “Heat release and knock in paraffinic and aromatic fuels and the effect of an ashless anti-knock additive” SAE Paper No. 952405 1995
- Kalghatgi G. T. Golombok, M. Snowdon, P. “Fuel effects on knock heat release and “CARS” temperatures in a spark ignition engine” Comb. Sci., and Tech. 110-111 209 1995
- Lutz, A. E. Kee, R. J. Miller, J. A. Dwyer, H. A. Oppenheim, A. K. “Dynamic effects of autoignition centers for hydrogen an C1,2 - hydrocarbon fuels.” Twenty-Second Symposium (International) on Combustion The Combustion Institute Pittsburgh 1683 1989
- König, G. Sheppard, C. G. W. “End gas autoignition and knock in SI engines” SAE Trans. 99 820 1990
- König, G. Maly, R. R. Bradley, D. Lau, A. K. C. Sheppard, C. G. W. “Role of exothermic centres on knock initiation and knock damage” SAE Trans. 99 840 1990
- Pan, J. Sheppard C. G. W. “A theoretical and experimental study of the modes of end gas autoignition leading to knock in SI engines” SAE Paper No. 942060 1994
- König, G. Maly, R.R. Schöffel, S. Blessing, G. “Effects of engine conditions,” Commission of the European Community 1993
- Bäuerle, B. Hoffman, F Behrendt, F. Warnatz, J. “Detection of hot spots in the end gas of an I. C. engine using two dimensional LIF of formaldehyde,” Twenty-Fifth International Symposium on Combustion The Combustion Institute Pittsburgh 135 1995
- Stiebels, B. Schreiber, M. Sadat Sakak, A “Development of a new measurement technique for the investigation of end-gas autoignition and engine knock,” SAE Paper No. 960827 1996
- Bradley, D. “Hot spots’ and gasoline engine knock,” J. Chem. Soc., Faraday Trans. 1996
- Bradley, D. Kalghatgi, G. T. Morley, C. Snowdon, P. Yeo, J. “CARS temperature measurements and the cyclic dispersion of knock in spark ignition engines” Twenty Fifth Symposium (International). on Combustion The Combustion Institute Pittsburgh 125 1994
- Bradley, D. Kalghatgi. G. T. Golombok, M. Yeo, J. “Heat release rates due to autoignition and their relationship to knock intensity in spark ignition engine” Twenty-Sixth Symposium (International) on Combustion The Combustion institute Pittsburgh
- Griffiths, J. F. “Reduced kinetic models and their application to practical combustion systems.” Prog. Energy and Combust. Sci. 21 25 1995
- Chun, K. M. Heywood, J. B “Estimating heat-release and mass-of-mixture burned from spark-ignition engine pressure data” Combust. Sci. and Tech. 541133 1987
- Cheung H. M. Heywood, J. B. “Evaluation of one-zone burn-rate analysis procedure using production SI engine pressure data” SAE Paper No. 932749 1993
- Kalghatgi, G. T. Snowdon, P. Macdonald, C. “Studies of knock in a spark ignition engine with “CARS” temperature measurements and using different fuels” SAE Paper No. 950690 1995
- Morley, C. Private communication