Prediction of ignition modes of NTC-fuel/air mixtures with temperature and concentration fluctuations

Abstract

Prediction of ignition modes of NTC-fuel/air mixtures with temperature and concentration fluctuations. Combustion and Flame, 213,[382][383][384][385][386][387][388][389][390][391][392][393]

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

“…Although a short ig resulting in a large u ′ is selected to save the computational cost, the selected conditions are still relevant to the SI engines by preserving the relevant length and time-scale ratios (Hawkes et al 2006;Yoo et al 2011). By a theoretical scaling analysis, and validated by a systematically parametric set of DNS cases, the previous studies (Hawkes et al 2006;Yoo et al 2011Yoo et al , 2013Im et al 2015;Luong et al 2020a) found that the flame-turbulence interaction can be understood in terms of relevant length and time-scale ratios of the turbulent flow structure compared with those of the flame. Particularly, ig ∕ t and l T ∕l e were found to be the key parameters instead of their absolute values (i.e., ig , u ′ , l e and l T ).…”

“…In these studies, a key issue was to identify the ignition characteristics, which was further developed into the ignition regime diagram (Im et al 2015;Pal et al 2017a) to predict the occurrence of strong and weak ignition modes in the presence of temperature and turbulence fluctuations. Further extension of the ignition regime identification to temperature and composition fluctuations has been proposed and validated (Luong et al 2019(Luong et al , 2020aAli et al 2018). In previous multi-dimensional DNS studies, the importance of the ratio of the length scale of temperature fluctuation to that of turbulence, l T ∕l e , as well as the ratio of the turbulent eddy turnover time, t = l e ∕u � , to the ignition delay time, ig , has been reported (Yoo et al 2011(Yoo et al , 2013.…”

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

“…The skeletal mechanism for DME oxidation was developed from the detailed mechanism consisting of 55 species and 290 elementary reactions. More details can be found in [1,51,52].…”

“…The initial mean temperature, the level of temperature fluctuations, and its characteristic length scale are varied to identify the developing detonation regime in a thermally inhomogeneous DME/air mixture. All the simulations are performed with initial uniform equivalence ratio, 𝜙 0 , and pressure, 𝑃 0 , of 1 and 40 atm, respectively, which represent the near top-dead-center conditions of an IC engine [1,2,2,21,[53][54][55][56][57][58][59][60][61]. As shown in Fig.…”

“…Modern internal combustion (IC) engines operate under elevated pressure enabled by downsized boosted technologies to achieve higher thermal efficiency, higher power-density output per volume, and ultra-low emission. 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].…”