Grenzen des Downsizing bei Ottomotoren durch Vorentflammungen

Willand, Jürgen; Daniel, Marc; Montefrancesco, Emanuela; Geringer, Bernhard; Hofmann, Peter; Kieberger, Markus

doi:10.1007/bf03225495

Cited by 12 publications

(5 citation statements)

References 2 publications

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“…20,28,29 LSPI events are usually very abrupt and cannot be controlled as simply as it is in the case of knocking combustion by retarding the spark angle or using richer mixtures. [29][30][31] LSPI can cause irregular combustion that is intermittent and unpredictable leading to high peak pressures (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) and intense knocking combustion (up to 13 MPa), which can potentially cause severe engine damage in a single cycle. 7,8,15,18,28 This irregular combustion phenomenon is referred to as super-knock or megaknock.…”

Section: Low-speed Pre-ignitionmentioning

confidence: 99%

“…They can also serve as high temperature spots to ignite the mixture. 30,46,50 As for the pre-ignition mechanism connected with combustible solid particles, it is as follows: The deposits formed by wetting of the cylinder liner wall and the deposits formed at low engine loads over an extended period of time peel off and float inside the combustion chamber volume. Immediately before pre-ignition, combustible solid particles in the cycle are maintained in a gradual combustion state and stay in the combustion chamber until the next cycle.…”

Section: Mechanisms Of Lspi Formationmentioning

confidence: 99%

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Reasons influencing the formation of low-speed pre-ignition

Stępień

2022

International Journal of Engine Research

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Low-speed pre-ignition (LSPI) is a problem for many highly boosted engines and constitutes a major industry challenge. This paper provides an overview of the reasons that might lead to low-speed pre-ignition. These reasons have been systematized and divided into four groups related to the engine, fuel, lubricating engine oil, and engine operating conditions. In the case of the engine, particular attention was drawn, among others, to the type of fuel injection, the method of mixture formation, the compression ratio, and piston design as important factors affecting the occurrence of pre-ignition in the case of stochastic self-ignition. The paper analyzes the influence of the engine operation and the adjustment of its operating parameters on the frequency of occurrence of low-speed pre-ignition. The paper extensively discusses the relationship between the engine lubricating oil including the oil base groups and its additives and the occurrence of abnormal combustion. The impact of different types of detergents was considered in more detail. The paper also describes the effects of the fuel properties on low-speed pre-ignition. The most important fuel properties from the point of view of its confirmed influence on the formation of low-speed pre-ignition are the its chemical composition, deposit control additives and volatility. The conclusion emphasizes that the operating conditions in a modern downsized, turbocharged gasoline engine can induce a low-speed pre-ignition problem, which can lead to destructive super-knock events. It was indicated that low-speed pre-ignition tends to become more prominent in the operating regime that is most beneficial to attaining improved fuel economy. Therefore, the solution to this problem is considered to be a key factor in further development of downsizing and improving the engine efficiency. An innovative element of the article, which distinguishes it from other similar articles, is the proposed logical division and systematization of the hitherto identified factors influencing the LSPI phenomenon. This has been done by separating, comprehensively listing and ordering these factors

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Section: Low-speed Pre-ignitionmentioning

confidence: 99%

Section: Mechanisms Of Lspi Formationmentioning

confidence: 99%

Reasons influencing the formation of low-speed pre-ignition

Stępień

2022

International Journal of Engine Research

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“…Engine downsizing is an effective method of reducing fuel consumption, and therefore the exhaust emissions of greenhouse gasses, and the obtained benefits are directly related to the degree of downsizing. The mechanical and thermal loads of engine components are the barrier to further increasing engine unit power, and in the case of SI engines also the problem of knocking, especially the socalled extreme knocking [62,63,70]. In the case of very large boost pressure even a single phenomenon of spontaneous mixture ignition initiated from hot components in the engine head (known as hot spots) can cause permanent damage to the piston-cylinder components [62].…”

Section: Ethanol As Fuel For Future Enginesmentioning

confidence: 99%

“…The mechanical and thermal loads of engine components are the barrier to further increasing engine unit power, and in the case of SI engines also the problem of knocking, especially the socalled extreme knocking [62,63,70]. In the case of very large boost pressure even a single phenomenon of spontaneous mixture ignition initiated from hot components in the engine head (known as hot spots) can cause permanent damage to the piston-cylinder components [62]. As a result engines of this type use a two thermostats cooling system which ensures a lower temperature of the fluid flowing through the cylinder head in comparison to the rest of the engine block, sub-optimal compression ratios are used due to the engine efficiency, the air fuel mixture is deliberately enriched under maximum load conditions to cool the combustion chamber and the ignition is delayed [60].…”

Section: Ethanol As Fuel For Future Enginesmentioning

confidence: 99%

An innovative system for piston engine combustion with laser-induced ignition of the hydrocarbon fuel consisting carbon nanotubes

et al. 2017

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The article proposes the concept of a new piston engine combustion system that is designed to meet future-oriented ecological requirements. The concept is to use ethanol as a fuel, in which a slurry of carbon nanotubes would be formed, which are characterized by the ability to ignite using a pulse of laser light fed into the combustion chamber. Modifying the shape of the light beam that penetrates the combustion chamber would allow to control the position and the size of the area in which the ignition of fuel would occur. The originality of the concept is to combine the latest achievements in the field of nanotechnology in the construction of lasers and the production of biofuels, so as to contribute to improving the environmental performance of engines using the existing synergies.The article discusses the prospects for the use of bioethanol as a fuel with zero carbon balance, a critical review of related research on light pulse initiated ignition of hydrocarbon fuels from carbon nanotubes was presented, and a review of studies of laser ignition for conventional fuels. The results of studies of carbon nanotubes suspensions in a variety of fuels conducted by the authors in order to seek solutions for the stable dispersions formation, that are resistant to nanotube agglomeration and sedimentation. The summary indicates directions for further research highlighting the importance of environmental impact.

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“…The so-called degree of downsizing (increase of cylinder pressure) is limited by the occurrence of irregular combustion phenomena like knocking and pre-ignition. Especially at high engine loads and low engine speeds (low-end torque), the probability of pre-ignition events increases drastically, as shown in testbed investigations [5][6][7][8].…”

Section: Introductionmentioning

confidence: 95%

Experimental and Numerical Analysis on Two-Phase Induced Low-Speed Pre-Ignition

et al. 2021

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The root cause of the initial low-speed pre-ignition (LSPI) is not yet clarified. The literature data suggest that a two-phase phenomenon is most likely triggering the unpredictable premature ignitions in highly boosted spark-ignition engines. However, there are different hypotheses regarding the actual initiator, whether it is a detached liquid oil-fuel droplet or a solid-like particle from deposits. Therefore, the present work investigates the possibility of oil droplet-induced pre-ignitions using a modern downsized engine with minimally invasive endoscopic optical accessibility incorporating in-cylinder lubrication oil detection via light-induced fluorescence. This setup enables the differentiation between liquid and solid particles. Furthermore, the potential of hot solid particles to initiate an ignition under engine-relevant conditions is analyzed numerically. To do so, the particle is generalized as a hot surface transferring heat to the reactive ambient gas phase. The gas-phase reactivity is represented as a TRF/air mixture based on RON/MON specifications of the investigated fuel. The chemical processes are predicted using a semi-detailed reaction mechanism, including 137 species and 633 reactions in a 2D CFD simulation framework. In the optical experiments, no evidence of a liquid oil droplet-induced pre-ignition could be found. Nevertheless, all observed pre-ignitions had a history of flying light-emitting objects. There are strong hints towards solid-like deposit LSPI initiation. The application of the numerical methodology to mean in-cylinder conditions of an LSPI prone engine operation point reveals that particles below 1000 K are not able to initiate a pre-ignition. A sensitivity analysis of the thermodynamic boundary conditions showed that the particle temperature is the most decisive parameter on the calculated ignition delay time.

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Grenzen des Downsizing bei Ottomotoren durch Vorentflammungen

Cited by 12 publications

References 2 publications

Reasons influencing the formation of low-speed pre-ignition

Reasons influencing the formation of low-speed pre-ignition

An innovative system for piston engine combustion with laser-induced ignition of the hydrocarbon fuel consisting carbon nanotubes

Experimental and Numerical Analysis on Two-Phase Induced Low-Speed Pre-Ignition

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