n-Heptane cool flame chemistry: Unraveling intermediate species measured in a stirred reactor and motored engine

Journal Article · 03 October 2017 · Combustion and Flame

DOI: https://doi.org/10.1016/j.combustflame.2017.09.003 · OSTI ID:1474083

Wang, Zhandong  ^[1]; Chen, Bingjie ^[1]; Moshammer, Kai ^[2]; Popolan-Vaida, Denisia M. ^[3]; Sioud, Salim ^[4]; Shankar, Vijai Shankar Bhavani ^[1]; Vuilleumier, David ^[5]; Tao, Tao ^[6]; Ruwe, Lena ^[7]; Bräuer, Eike ^[7]; Hansen, Nils ^[5]; Dagaut, Philippe ^[8]; Kohse-Höinghaus, Katharina ^[7]; Raji, Misjudeen A. ^[4]; Sarathy, S. Mani ^[1]

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1. King Abdullah Univ. of Science and Technology (KAUST), Thuwal (Saudi Arabia). Clean Combustion Research Center (CCRC)
2. Sandia National Lab. (SNL-CA), Livermore, CA (United States). Combustion Research Facility; Physikalisch-Technische Bundesanstalt, Braunschweig (Germany)
3. Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Chemical Sciences Division
4. King Abdullah Univ. of Science and Technology (KAUST), Thuwal (Saudi Arabia). Analytical Core Lab.
5. Sandia National Lab. (SNL-CA), Livermore, CA (United States). Combustion Research Facility
6. Sandia National Lab. (SNL-CA), Livermore, CA (United States). Combustion Research Facility; Tsinghua Univ., Beijing (China). Center for Combustion Energy. Dept. of Thermal Engineering
7. Bielefeld Univ. (Germany). Dept. of Chemistry
8. Inst. of Engineering Sciences and Systems (CNRS-INSIS), Orléans (France)

This paper identifies classes of cool flame intermediates from n-heptane low-temperature oxidation in a jet-stirred reactor (JSR) and a motored cooperative fuel research (CFR) engine. The sampled species from the JSR oxidation of a mixture of n-heptane/O₂/Ar (0.01/0.11/0.88) were analyzed using a synchrotron vacuum ultraviolet radiation photoionization (SVUV-PI) time-of-flight molecular-beam mass spectrometer (MBMS) and an atmospheric pressure chemical ionization (APCI) Orbitrap mass spectrometer (OTMS). The OTMS was also used to analyze the sampled species from a CFR engine exhaust. Approximately 70 intermediates were detected by the SVUV-PI-MBMS, and their assigned molecular formulae are in good agreement with those detected by the APCI-OTMS, which has ultra-high mass resolving power and provides an accurate elemental C/H/O composition of the intermediate species. Furthermore, the results show that the species formed during the partial oxidation of n-heptane in the CFR engine are very similar to those produced in an ideal reactor, i.e., a JSR. The products can be classified by species with molecular formulae of C₇H₁₄O_x (x = 0–5), C₇H₁₂O_x (x = 0–4), C₇H₁₀O_x (x = 0–4), C_nH_2n (n = 2–6), C_nH_2n-2 (n = 4–6), C_nH_2n+2O (n = 1–4), C_nH_2nO (n = 1–6), C_nH_2n-2O (n = 2–6), C_nH_2n-4O (n = 4–6), C_nH_2n+2O₂ (n = 0–4, 7), C_nH_2nO₂ (n = 1–6), C_nH_2n-2O₂ (n = 2–6), C_nH_2n-4O₂ (n = 4–6), and C_nH_2nO₃ (n = 3–6). The identified intermediate species include alkenes, dienes, aldehyde/keto compounds, olefinic aldehyde/keto compounds, diones, cyclic ethers, peroxides, acids, and alcohols/ethers. Reaction pathways forming these intermediates are proposed and discussed herein. Finally, these experimental results are important in the development of more accurate kinetic models for n-heptane and longer-chain alkanes.

• Research Organization: Sandia National Lab. (SNL-CA), Livermore, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); King Abdullah University of Science and Technology (KAUST), Thuwal (Saudi Arabia); Bielefeld Univ. (Germany); Inst. of Engineering Sciences and Systems (CNRS-INSIS), Orléans (France); Tsinghua Univ., Beijing (China)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE National Nuclear Security Administration (NNSA); King Abdullah Univ. of Science and Technology (KAUST) (Saudi Arabia); Saudi Aramco (Saudi Arabia); German Research Foundation (DFG); European Research Council (ERC); China Scholarship Council
• Grant/Contract Number: AC04-94AL85000; AC02-05CH11231; 767 OSR-2016-CRG5-3022; KO1363/31-1; 291049-2G-CSafe; 201506210349; AC04-94-AL85000
• OSTI ID: 1474083
• Alternate ID(s): OSTI ID: 1549270
• Report Number(s): SAND-2018-10258J; 667992
• Journal Information: Combustion and Flame, Vol. 187; ISSN 0010-2180
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
n-heptane
auto-oxidation
peroxides
synchrotron VUV photoionization mass spectrometry
APCI Orbitrap mass spectrometry