Surface Ignition: Factors Affecting Its Occurrence In Engines

Pahnke, A. J.

doi:10.4271/630489

Cited by 4 publications

(4 citation statements)

References 15 publications

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“…Since autoignition of the fuel/air mixture plays no role in preignition, the probability of preignition should not and, as multiple experiments have shown, 41,44,46,47 does not correlate with RON and MON, which describe the autoignition behavior of the fuel, all else being equal. For a given engine operating condition, a fuel with a larger laminar burning velocity is more likely to cause preignition.…”

Section: Implications For Fuels For Si Enginesmentioning

confidence: 99%

“…Preignition is an abnormal combustion phenomenon where an expanding flame front is established before the spark plug fires in the engine. It was a major area of concern in the 1950s 41 –46 but not in the succeeding decades. With the increasing trend in downsizing and turbocharging, it has again become a concern in turbocharged direct injection spark-ignition (DISI) engines (Chapter 5 in Kalghatgi 12 ).…”

Section: Implications For Fuels For Si Enginesmentioning

confidence: 99%

“…In older studies, this source was shown to be hot spots on internal surfaces of the engine and combustion chamber deposits played a role. 41–46 However, in modern DISI engines, this source seems to be the combustion, away from the internal surfaces, of droplets of the mixture of lubricant oil and fuel flying into the cylinder 49–51 from the piston top land crevice, although surface ignition cannot be entirely ruled out. The process leading up to the creation of the initial hot spot from the burning of the droplets is not well understood but must involve autoignition and possibly catalytic reactions.…”

Section: Implications For Fuels For Si Enginesmentioning

confidence: 99%

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The outlook for fuels for internal combustion engines

Kalghatgi

2014

International Journal of Engine Research

201

142

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The demand for transport energy is increasing, but this increase is heavily skewed toward heavier fuels such as diesel and jet fuel while the demand for gasoline might decrease. As spark-ignition engines develop to become more efficient, abnormal combustion such as knock and preignition will become more likely. High antiknock quality fuels, those with high research octane number and preferably low motor octane number, will enable future spark-ignition engines to reach their full potential. Higher fuel antiknock quality is also likely to mitigate “superknock” resulting from preignition—an abnormal combustion problem in turbocharged spark-ignition engines. In many parts of the world, fuel antiknock specifications are set on the assumption that higher motor octane number contributes to increased knock resistance. Specifications for fuel antiknock quality have a great impact on fuels manufacture and will need to be revised as this mismatch between existing specifications and engine requirements widens. The primary challenge for diesel engines is to reduce emissions of soot and NOx while maintaining high efficiency, and this becomes much easier if such engines are run on fuels of extremely low cetane. Significant development is needed before such engines can be seen on practical vehicles. In the long term, compression ignition engines are likely to use fuels with research octane number in the range of 70–85 (cetane number<∼30) but with no strict requirements on volatility. Such fuels would require less processing in the refinery than today’s fuels. Such an engine/fuels system will be at least as efficient as today’s diesel engine but could be significantly cheaper and also open a path to mitigate the imbalance in demand growth between heavy and light fuels that is expected to arise otherwise. The review concludes with a possible long-term fuel scenario.

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Section: Implications For Fuels For Si Enginesmentioning

confidence: 99%

Section: Implications For Fuels For Si Enginesmentioning

confidence: 99%

Section: Implications For Fuels For Si Enginesmentioning

confidence: 99%

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The outlook for fuels for internal combustion engines

Kalghatgi

2014

International Journal of Engine Research

201

142

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“…The experimental derivation of such comparative ratings has been the objective of several engine investigations, 5,11,29 which have consistently shown i -octane to have a good resistance to pre-ignition. Downs and Theobald 6 measured the minimum electrical power for a pre-igniter to cause pre-ignition of different fuels in a Ricardo E.6 single-cylinder engine.…”

Section: Pre-ignition At Hot Surfacesmentioning

confidence: 99%

Pre-ignition and ‘super-knock’ in turbo-charged spark-ignition engines

Kalghatgi

Bradley

2012

International Journal of Engine Research

252

135

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Earlier studies of pre-ignitions at hot surfaces are first reviewed. The concept of a critical radius of a hot pocket of gas, closely related to the laminar flame thickness, that is necessary to initiate a propagating flame, has been used successfully to predict relative tendencies of different fuel-air mixtures to pre-ignite. As the mixture is compressed, the thickness of potential laminar flames decreases, and when this becomes of the order of the thermal sheath thickness at the hottest surface, pre-ignition can occur there, creating a propagating flame. Measured engine pre-ignition ratings are shown to correlate well with laminar flame thicknesses. Predictions are made concerning the effects of changes in intake temperature and pressure on the pre-ignition of different fuels.A growing current concern is occasional gas-phase, autoignitive, pre-ignitions that can occur in turbo-charged engines, giving rise to very severe autoignition and knock. It is concluded from the evidence of engine pressure records and autoignition delay times of the mixtures that such pre-ignitions have not arisen from autoignition of the fuel, but of a mixture with a smaller autognition delay time than stoichiometric n-heptane-air. One possibility is that autoignition occurs at hot spots containing some lubricating oil. It is shown that such pre-ignitions, particularly with catalytic enhancement, could initiate a propagating flame, rather than autoignitive propagation.In the later, much more severe autoignition arising after pre-ignition, autoignitive propagation velocities at a hot spot are estimated from computed values of the ignition delay times and assumed reactivity gradients in the fuel-air mixture at the hot spot. The severity of the associated pressure pulse is dependent upon the ratios j, of the acoustic speed to the localised autoignitive velocity, and e, of the residence time of the acoustic wave in the hot spot to the short excitation time in which most of the chemical energy is released. The regime in which a localised detonation can be generated in the hot spot is defined by a peninsula on a plot of j against e. A locus is plotted on this figure corresponding to the growing measured intensities of the engine knock as the pressure increases. This is based on computed autoignition delays and excitation times, for an appropriate surrogate fuel. These changes are characterised by j tending to unity and e tending to ever-higher values, with increasingly intense, localised, developing detonations.

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Surface Ignition and Rumble in Engines: A Literature Review

Pless¹

1965

SAE Technical Paper Series

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Surface Ignition: Factors Affecting Its Occurrence In Engines

Cited by 4 publications

References 15 publications

The outlook for fuels for internal combustion engines

The outlook for fuels for internal combustion engines

Pre-ignition and ‘super-knock’ in turbo-charged spark-ignition engines

Surface Ignition and Rumble in Engines: A Literature Review

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