Numerical Simulation to Understand the Cause and Sequence of LSPI Phenomena and Suggestion of CaO Mechanism in Highly Boosted SI Combustion in Low Speed Range

Moriyoshi, Yasuo; Yamada, Toshio; Tsunoda, Daisuke; Xie, Mingzhao; Kuboyama, Tatsuya; Morikawa, Koji

doi:10.4271/2015-01-0755

Cited by 32 publications

(7 citation statements)

References 12 publications

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“…Additionally, it could be shown that the viscosity grade of the lubricating oil influences the droplet release probability significantly. This observation is confirmed by numerical simulations of the piston crevice volume using a Volume-of-Fluid (VoF)-approach [15,16]. Further on, the influence of fuel spray/wall interaction is also reported by testbed investigations [5,[17][18][19][20].…”

supporting

confidence: 54%

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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confidence: 54%

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

et al. 2021

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“…Fewer pre-ignition events are observed after preliminary cleaning of the combustion chamber compared to a contaminated one . 17,27,[53][54][55][56][57][58] It is also important to remember that, as the engine ages, deposits start to form. Deposits are primarily formed on the cylinder head, piston crown, intake valves, injector tip, and on the piston crown land.…”

Section: Mechanisms Of Lspi Formationmentioning

confidence: 99%

“…Fewer pre-ignition events are observed after preliminary cleaning of the combustion chamber compared to a contaminated one . 17,27,53–58…”

Section: Low-speed Pre-ignitionmentioning

confidence: 99%

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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“…26,27 Calcium-based detergent additives in the lubricant oil may undergo exothermic reaction to form an ignition source. 28…”

Section: Introductionmentioning

confidence: 99%

Optimizing split fuel injection strategies to avoid pre-ignition and super-knock in turbocharged engines

Singh

Morganti

Dibble

2019

International Journal of Engine Research

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Fuel injection strategies often have a considerable impact on pre-ignition in high specific output gasoline engines. Splitting the injection event into two or more pulses has been widely explored as one means of reducing pre-ignition. As effective as these strategies can be with respect to pre-ignition suppression, they often introduce other compromises into the combustion process, for example, reduced indicated mean effective pressure or greater cycle-to-cycle variation. This study examines a split injection strategy with up to three injection pulses for suppressing pre-ignition, while optimizing the start of injection and duration of injection to minimize the associated compromises on the combustion process. The results demonstrate that splitting the injection event generally lowers the in-cylinder temperature and reduces the fuel mass that reaches the cylinder liner. This leads to a lower probability of creating oil-fuel droplets, which may act as a precursor for pre-ignition. The split injection strategy with a late injection when the piston is close to top dead center is shown to perform even better in terms of pre-ignition suppression, while providing comparable indicated mean effective pressure and cycle-to-cycle variation to the baseline case with a single injection pulse. Finally, the injection pressure is varied to establish an optimal combination of operating parameters for avoiding pre-ignition in high specific output gasoline engines.

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Numerical Simulation to Understand the Cause and Sequence of LSPI Phenomena and Suggestion of CaO Mechanism in Highly Boosted SI Combustion in Low Speed Range

Cited by 32 publications

References 12 publications

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

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

Reasons influencing the formation of low-speed pre-ignition

Optimizing split fuel injection strategies to avoid pre-ignition and super-knock in turbocharged engines

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