Numerical investigations on the effects of turbulence intensity on knocking combustion in a downsized gasoline engine

Lin Chen, Haiqiao Wei, Ceyuan Chen, Dengquan Feng, Lei Zhou and Jiaying Pan

Energy, 2019, vol. 166, issue C, 318-325

Abstract: In this work, the influence of turbulence intensity on knocking characteristics was studied. Different levels of initial swirl ratio inside cylinder were firstly performed to investigate the effect of turbulence intensity on combustion process. The results show that the enhanced turbulence intensity with increasing initial swirl ratio accelerates the spark-ignited flame (main flame) propagation, resulting in a shortage of combustion phasing (or an advance combustion phasing) and a faster flame speed. Under low turbulence intensity, the faster flame propagation can facilitate knocking combustion because of the enhanced compression of SI flame on the improvement of end-gas thermodynamic conditions. However, further increases in turbulence intensity and flame speed suppress the knocking combustion due to the insufficient time for end-gas autoignition occurrence. Further analysis shows that knock intensity mainly depended on the Unburned Mass Fraction (UBMF). Under lower levels of initial swirl ratios, the enhanced compression of SI flame with the increase of turbulence intensity induces an advanced knock onset, which leads to a larger UBMF and heavier knock intensity. However, under higher swirl ratio scenarios, UBMF and knock intensity exhibited an opposite trend because the consumption of end-gas by the fast main flame played a dominating role.

Keywords: Turbulence intensity; Swirl ratio; Flame speed; Knock intensity; Unburned mass fraction (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (9)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:166:y:2019:i:c:p:318-325

DOI: 10.1016/j.energy.2018.10.058

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