A RANS knock model to predict the statistical occurrence of engine knock

D'Adamo, Alessandro; Breda, Sebastiano; Fontanesi, Stefano; Irimescu, Adrian; Merola, Simona Silvia; Tornatore, Cinzia

doi:10.1016/j.apenergy.2017.01.101

Cited by 45 publications

(19 citation statements)

References 32 publications

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“…Wall wetting is directly related to load, meaning that as engine output is increased at fixed rotational speed, larger quantities of fuel need to be injected; several mechanisms during air-fuel mixture formation contribute to complex effects on charge distribution during combustion, that can be identified through combined experimental and numerical investigations [18,19]. Mixture inhomogeneity plays a significant role during the initial stages of flame kernel development [20], but also influences the occurrence of abnormal combustion phenomena due to autoignition [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Effect of Fuel Injection Strategy on the Carbonaceous Structure Formation and Nanoparticle Emission in a DISI Engine Fuelled with Butanol

et al. 2017

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Within the context of ever wider expansion of direct injection in spark ignition engines, this investigation was aimed at improved understanding of the correlation between fuel injection strategy and emission of nanoparticles. Measurements performed on a wall guided engine allowed identifying the mechanisms involved in the formation of carbonaceous structures during combustion and their evolution in the exhaust line. In-cylinder pressure was recorded in combination with cycle-resolved flame imaging, gaseous emissions and particle size distribution. This complete characterization was performed at three injection phasing settings, with butanol and commercial gasoline. Optical accessibility from below the combustion chamber allowed visualization of diffusive flames induced by fuel deposits; these localized phenomena were correlated to observed changes in engine performance and pollutant species. With gasoline fueling, minor modifications were observed with respect to combustion parameters, when varying the start of injection. The alcohol, on the other hand, featured marked sensitivity to the fuel delivery strategy. Even though the start of injection was varied in a relatively narrow crank angle range during the intake stroke, significant differences were recorded, especially in the values of particle emissions. This was correlated to the fuel jet-wall interactions; the analysis of diffusive flames, their location and size confirmed the importance of liquid film formation in direct injection engines, especially at medium and high load.

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Section: Introductionmentioning

confidence: 99%

Effect of Fuel Injection Strategy on the Carbonaceous Structure Formation and Nanoparticle Emission in a DISI Engine Fuelled with Butanol

et al. 2017

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“…In RANS analyses a statistical version (RANS-PDF) of the knock model is used, which is developed to infer knock statistics from RANS equation and whose details can be found in [35][36][37]. The model details are briefly recalled here for the sake of completeness.…”

Section: Knock Modellingmentioning

confidence: 99%

“…The approach is based on the RANS formalism for averaged quantities, combined with the use of transport equations for variances of physical conditions allowing to estimate a knock probability or a fraction of knocking cycles. Pursuing the same concept developed by Linse et al [46] and relying on transport equations for mixture fraction and enthalpy variances, a statistical RANS model described in [35][36][37] was proposed to infer not only the average KI but also the presumed distribution of knock intensity, and the model validation was carried out on both an optically accessible research engine as well as a production unit. Conversely from the use of a traditional RANS approach, the use of the developed statistics-based knock model gives a quantitative information regarding the presumed fraction of knocking cycles affecting the mean simulation for a given operating condition, thus enhancing the consistency of a RANS simulation of knock with a typical test-bench acquisition dataset.…”

Section: Introductionmentioning

confidence: 99%

The potential of statistical RANS to predict knock tendency: Comparison with LES and experiments on a spark-ignition engine

et al. 2019

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“…Thanks to the blooming development of high-performance computing clusters, the CFD method has been proved able to help us understand abnormal combustion mechanisms [31][32][33][34][35]. In the 1-D numerical field, Livengood and Wu [36] proposed an equation to predict the occurrence of auto-ignition in unburned mixtures.…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of End-Gas Autoignition and Pressure Oscillation in a Downsized SI Engine Using Large Eddy Simulation

Zhong

Liu

2019

Energies

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Knock and super-knock are abnormal combustion phenomena in engines, however, they are hard to study comprehensively through optical experimental methods due to their inherent destructive nature. In present work, the methodology of large eddy simulation (LES) coupled with G equations and a detailed mechanism of primary reference fuel (PRF) combustion is utilized to address the mechanisms of knock and super-knock phenomena in a downsized spark ignition gasoline engine. The knock and super-knock with pressure oscillation are qualitatively duplicated through present numerical models. As a result, the combustion and onset of autoignition is more likely to occur at top dead center (TDC), which causes end gas at a higher temperature and pressure. It is reasonable to conclude that the intensity of knock is not only proportional to the mass fraction of mixtures burned by the autoignition flame but the thermodynamics of the unburned end-gas mixture, and the effect of thermodynamics is more important. It also turns out that two auto-ignitions occur in conventional knock conditions, while only one auto-ignition takes place in super-knock conditions. However, the single autoignition couples with the pressure wave and they reinforce each other, which eventually evolves into detonation combustion. This work gives the valuable insights into knock phenomena in spark ignition gasoline engines.

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A RANS knock model to predict the statistical occurrence of engine knock

Cited by 45 publications

References 32 publications

Effect of Fuel Injection Strategy on the Carbonaceous Structure Formation and Nanoparticle Emission in a DISI Engine Fuelled with Butanol

Effect of Fuel Injection Strategy on the Carbonaceous Structure Formation and Nanoparticle Emission in a DISI Engine Fuelled with Butanol

The potential of statistical RANS to predict knock tendency: Comparison with LES and experiments on a spark-ignition engine

Numerical Analysis of End-Gas Autoignition and Pressure Oscillation in a Downsized SI Engine Using Large Eddy Simulation

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