State-of-the-art modeling of two-stage auto-ignition: Turbulence, evaporation and chemistry effects

• Published in: Energy conversion and management 2023-09, Vol.291, p.117269, Article 117269
• Main Authors: Zhang, Yu, Peng, Qianchen, Wang, Chunmei, Huang, Yuhan, Zhou, Pei, Qian, Yejian, Ye, Bin, Indra Mahlia, T.M., Chyuan Ong, Hwai
• Format: Article
• Language: English
• Subjects: administrative management; Clean combustion; combustion; droplets; energy conversion; energy use and consumption; evaporation; Evaporation-turbulence-chemistry; mathematical models; Numerical modeling; pollutants; temperature; turbulent flow; Two-stage auto-ignition
• ISSN: 0196-8904; 1879-2227
• DOI: 10.1016/j.enconman.2023.117269

[Display omitted] •Evaporation affects ignition in homogeneous conditions by changing thermal states.•Stratification causes preferential ignition, front propagation and scalar dissipation.•Induction timescale is analyzed by statistics in turbulent environments.•Enhanced turbulence and scalar dissipation cause non-monotonic deflagration speed.•Turbulence affects ignition front by changing spatial gradients of ignition delay. Internal combustion engines are the dominant power sources in transport, accounting for significant amounts of fuel consumption and pollutant emissions. Low-temperature combustion is a promising technology for engine combustion, whose main challenge is the complex control of two-stage auto-ignition that determines the performance of a low-temperature combustion engine. This paper systematically reviews the state-of-the-art advances in auto-ignition modeling which is an essential tool to understand auto-ignition mechanisms and provides valuable guidance for designing more efficient and cleaner engines. This paper focuses on turbulence, evaporation and chemistry effects without the consideration of inter-droplet interactions. Five models with increasing complexity are discussed and compared, including homogeneous models without and with evaporation (models 1 and 2), droplet simulation in static environments (model 3), and direct numerical simulation without and with evaporation (models 4 and 5). Rapid mixing leads to homogeneous conditions in models 1 and 2, in which two-stage auto-ignition is divided into low-temperature induction, low-temperature auto-ignition, high-temperature induction and high-temperature auto-ignition. Model 1 only considers chemical reactions and auto-ignition is determined for a certain thermal state. Droplet evaporation affects the auto-ignition evolution in model 2 through evaporation-induced changes in the thermal state. Compared with homogeneous models, droplet evaporation in model 3 leads to compositional and temperature stratifications which cause three new phenomena: preferential auto-ignition, reaction front propagation and non-zero scalar dissipationrate. Models 4 and 5 introduce turbulent effects on induction timescale and front propagation. Finally, challenges and future directions in auto-ignition modeling are outlined.