Multi-stage heat release in lean combustion: Insights from coupled tangential stretching rate (TSR) and computational singular perturbation (CSP) analysis
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ArticleKAUST Department
Chemical Engineering ProgramClean Combustion Research Center
Combustion and Pyrolysis Chemistry (CPC) Group
Mechanical Engineering
Mechanical Engineering Program
Physical Science and Engineering (PSE) Division
Date
2020-06-17Online Publication Date
2020-06-17Print Publication Date
2020-09Embargo End Date
2022-06-17Submitted Date
2019-12-10Permanent link to this record
http://hdl.handle.net/10754/663748
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There is a growing interest in leaner burning internal combustion engines as an enabler for higher thermodynamic efficiency. The extension of knock-limited compression ratio and the increase in specific heat ratio with lean combustion are key factors for boosting efficiency. Under lean burning conditions, there is emerging evidence that certain fuels exhibit unusual heat release characteristics. It has been reported that fuel/air mixtures undergo three-stage heat release or delayed high temperature heat release: starting with an initial low temperature heat release, similar to the one observed in two stage ignition, followed by an intermediate stage where thermal runaway is inhibited, and then advances to a relatively slow third stage of combustion. The focus of this study is to examine the conditions under which various fuels exhibit three stage ignition or delayed high temperature heat release. The auto-ignition of hydrocarbons/air mixtures is simulated in a closed adiabatic homogenous batch reactor where the charge is allowed to auto-ignite at constant volume vessel under predefined initial temperature and pressure. The simulations cover pressures of 10–60 bar, temperatures of 600 K–900 K, and fuel to air ratio from stoichiometry (equivalence ratio) of 0.3–1.0. Tangential stretching rate (TSR) and the computational singular perturbation Slow Importance Indices for temperature are used to identify important reactions contributing to the temperature growth rate at critical time instants of the auto-ignition process. Overall, three-stage ignition or delayed high temperature heat release is found to be present for most fuels under lean fuel/air mixtures, high pressures, and low temperature conditions. The radical termination reactions of H, OH, and HO2 during the high temperature heat release are leading factors for the distinct separation of heat release stages.Citation
AlRamadan, A. S., Galassi, R. M., Ciottoli, P. P., Valorani, M., & Sarathy, S. M. (2020). Multi-stage heat release in lean combustion: Insights from coupled tangential stretching rate (TSR) and computational singular perturbation (CSP) analysis. Combustion and Flame, 219, 242–257. doi:10.1016/j.combustflame.2020.05.026Sponsors
The simulation work was supported by King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) with funds given to the Clean Combustion Research Center. We acknowledge funding from the KAUST Clean Fuels Consortium and its member companies. MV, PPC, and RMG acknowledge the partial support from the Italian Ministry of University and Research.Publisher
Elsevier BVJournal
Combustion and FlameAdditional Links
https://linkinghub.elsevier.com/retrieve/pii/S0010218020302133ae974a485f413a2113503eed53cd6c53
10.1016/j.combustflame.2020.05.026