Temperature gradient induced detonation development inside and outside a hotspot for different fuels

Pan, Jiaying; Dong, Shengjie; Wei, Haiqiao; Li, Tao; Zhou, Lei

doi:10.1016/j.combustflame.2019.04.003

Cited by 61 publications

(24 citation statements)

References 43 publications

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“…It is noted that the present detonation regime is much broader than the one reported by Pan et al 22 for methane/air. This may be due to the fact that stronger criterion for detonation development was used by Pan et al 22 Figure 6 compares the detonation development regimes predicted by three kinetic models: GRI reduced, Aramco 3.0 and FFCM-1. Qualitatively, all these kinetic models predict the C-shaped boundaries for the detonation development regime.…”

Section: Resultscontrasting

confidence: 47%

Detonation development from a hot spot in methane/air mixtures: Effects of kinetic models

Dai

Chen

2020

International Journal of Engine Research

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Natural gas is a promising alternative fuel which can be used in internal combustion engines to achieve low carbon emission and high thermal efficiency. However, at high compression ratio, super-knock due to detonation development might occur. In this study, the autoignitive reaction front propagation and detonation development from a hot spot were investigated numerically and the main component of natural gas, methane, was considered. The objective is to assess the performance of different kinetic models in terms of predicting hot spot–induced detonation development in methane/air mixtures. First, simulations for the constant-volume homogeneous ignition in a stoichiometric methane/air mixture were conducted. The ignition delay time, excitation time, critical temperature gradient, thermal sensitivity and reduced activation energy predicted by different kinetic models were obtained and compared. It was found that there are notable discrepancies among the predictions by different kinetic models. Then, hundreds of one-dimensional simulations were conducted for detonation development from a hot spot in a stoichiometric CH4/air mixture. Different autoignition modes were identified and the detonation regimes were derived based on the peak pressure and reaction front propagation speed. It was found that even at the same conditions, different propagation modes can be predicted by different kinetic models. The broadest detonation development regime was predicted by the reduced GRI mechanism, while a relatively narrow regime was predicted by the recent kinetic models such as FFCM-1 and Aramco 3.0. The present results indicate that super-knock prediction strongly depends on the kinetic model used in simulations. Therefore, significant efforts should be devoted to the development and validation of kinetic models for natural gas at engine conditions.

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Section: Resultscontrasting

confidence: 47%

Detonation development from a hot spot in methane/air mixtures: Effects of kinetic models

Dai

Chen

2020

International Journal of Engine Research

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“…The diagram has been widely adopted to determine the detonation conditions for different fuels with good prediction (Bates et al 2016;Bates and Bradley 2017;Kalghatgi and Bradley 2012;Peters et al 2013;Dai et al 2015;Yu and Chen 2015;Dai et al 2017;Terashima et al 2017;Pan et al 2016Pan et al , 2017bWei et al 2018;Pan et al 2019;Sow et al 2019). The effects of multiple hot spots in terms of their size and separation distance have also been investigated in one-dimensional (1-D) configurations (Wei et al 2018;Terashima et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Effects of Turbulence and Temperature Fluctuations on Knock Development in an Ethanol/Air Mixture

Luong

Pérez

Sankaran

et al. 2020

Flow Turbulence Combust

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The effects of turbulence on knock development and intensity for a thermally inhomogeneous stoichiometric ethanol/air mixture at a representative end-gas autoignition condition in internal combustion engines are investigated using direct numerical simulations with a skeletal reaction mechanism. Two-and three-dimensional simulations are performed by varying the most energetic length scale of temperature, l T , and its relative ratio with the most energetic length scale of turbulence, l T ∕l e , together with two different levels of the turbulent velocity fluctuation, u ′ . It is found that l T /l e and the ratio of ignition delay time to eddy-turnover time, ig ∕ t , are the key parameters that control the detonation development. An increase in either l T or l e enhances the detonation propensity by allowing a longer run-up distance for the detonation development. The characteristic length scale of the temperature field, l T , is significantly modified by high turbulence intensity achieved by a large l e and u ′ . The intense turbulence mixing effectively distributes the initial temperature field to broader scales to support the developing detonation waves, thereby increasing the likelihood of the detonation formation. On the contrary, high turbulence intensity with a short mixing time scale, achieved by a small l e and a large u ′ , reduces the super-knock intensity attributed to the finer broken-up structures of detonation waves. Either ig ∕ t less than unity or l e = l T even with a large u ′ is found to have no significant effect on super-knock mitigation. Finally, high turbulent intensity may induce high-pressure spikes comparable to the von Neumann spike. Increased temperature and pressure by combustion heating, noticeably after the peak of heat release rate, significantly enhance the collision and interaction of multiple emerging autoignition fronts near the ending combustion process, resulting in localized high-pressure spikes.

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“…However, being operated at elevated pressure and high-load conditions leads to a higher propensity of undesired preignition, knock, and even superknock [1][2][3][4][5][6][7][8]. Superknock is characterized as a developing detonation process featuring excessive pressure oscillations and extremely high-pressure amplitudes that can damage combustion-chamber components [7,[9][10][11][12][13][14][15][16][17][18][19][20]20]. Improved understandings of the superknock propensity and a reliable criterion to predict it are needed to prevent destructive operation of combustion devices [2,4,5,7,[21][22][23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Knock propensity in a thermally inhomogeneous DME/air mixture: a DNS study

Luong

2022

AIAA SCITECH 2022 Forum

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Superknock propensity in a stoichiometric dimethyl-ether (DME)/air mixture with temperature inhomogeneities under realistic IC engine conditions is investigated using two-dimensional direct numerical simulations (DNS). The developing detonation regime at different conditions is identified by varying the initial mean temperature lying in the low-, intermediate-, and high-temperature chemistry regimes, the level of temperature fluctuations, and its characteristic length scale. We found that the cool flame from the first-stage ignition induces synergistic effects on promoting knock tendency. First, it significantly decreases a minimum run-up distance requirement for developing detonation due to the low-temperature chemistry. Second, analyzing the temporal evolution of the spatial distribution of ignition delay field reveals that the heat release rate from the first-stage ignition effectively modifies the initial field of the ignition delay time, thereby shifting the mixture towards the developing detonation regime. The interaction of multiple ignition kernels is also found to play an important role in enhancing the onset of detonation.

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Temperature gradient induced detonation development inside and outside a hotspot for different fuels

Cited by 61 publications

References 43 publications

Detonation development from a hot spot in methane/air mixtures: Effects of kinetic models

Detonation development from a hot spot in methane/air mixtures: Effects of kinetic models

Effects of Turbulence and Temperature Fluctuations on Knock Development in an Ethanol/Air Mixture

Knock propensity in a thermally inhomogeneous DME/air mixture: a DNS study

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