Detonation development in PRF/air mixtures under engine-relevant conditions

Lee，Hsu Chew1; Dai，Peng1; Chen，Zheng2; Gan，Xiaohua1

2022

10.1016/j.proci.2022.09.049

PROCEEDINGS OF THE COMBUSTION INSTITUTE   Impact Factor & Quartile

1540-7489

The development of advanced boosted internal combustion engines (ICEs) is constrained by super-knock which is closely associated with end gas autoignition and detonation development. The present study numerically investigates the transient autoignition and detonation development processes under engine-relevant conditions for primary reference fuel (PRF) consisting of n-heptane and isooctane. The effects of PRF composition are systematically examined. By considering the transient local sound speed rather than its initial value, a new non-dimensional parameter is proposed to assess the transient chemical-acoustic interaction and to quantify the autoignition modes. Two detonation sub-modes, normal and over-driven detonation, are identified and the corresponding mechanisms are interpreted. For the over-driven detonation, there exist two developing regimes with weak/strong chemical-acoustic coupling and slow/rapid pressure enhancement. It is found that the maximum pressure caused by autoignition decreases with the blending ratio of isooctane, mainly due to the increase in excitation time. Besides, the strongest detonation induced by hot spot usually occurs within the over-driven detonation sub-regime. Its condition can be well quantified by the new non-dimensional parameter proposed in work and its strength is determined by the ratio of hot spot acoustic time to excitation time. The deviation of transient autoignition front propagation from prediction based on homogenous ignition is mainly attributed to the non-uniform compression effect caused by gradually enhanced pressure wave, while the influence of heat conduction and mass diffusion is negligible. The initial expansion stage dominating the induction period of local autoignition is greatly influenced by the compression of pressure wave. Therefore, the continuously enhanced pressure wave non-uniformly changes the local ignition delay (i.e. reduces its spatial gradient) within the hot spot and thereby accelerates the autoignition front propagation. The relationship among the parameters quantifying the detonation propensity is assessed and interpreted. The present study provides helpful understanding of detonation development under engine conditions.

Autoignition Detonation development Hot spot Pressure wave PRF

English

First ; Corresponding

ENGINEERING

2-s2.0-85142836749

Scopus

1.Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, China
2.SKLTCS, CAPT, BIC-ESAT, College of Engineering, Peking University, Beijing 100871, China

Lee，Hsu Chew,Dai，Peng,Chen，Zheng,et al. Detonation development in PRF/air mixtures under engine-relevant conditions[J]. PROCEEDINGS OF THE COMBUSTION INSTITUTE,2022.

Lee，Hsu Chew,Dai，Peng,Chen，Zheng,&Gan，Xiaohua.(2022).Detonation development in PRF/air mixtures under engine-relevant conditions.PROCEEDINGS OF THE COMBUSTION INSTITUTE.

Lee，Hsu Chew,et al."Detonation development in PRF/air mixtures under engine-relevant conditions".PROCEEDINGS OF THE COMBUSTION INSTITUTE (2022).