Products of catalytic oxidative coupling of methane to improve thermal efficiency in natural gas engines

Seokwon Cho, Hyewon Lee, Ying Lin, Satbir Singh, William F. Northrop

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Pretreating natural gas using catalytic oxidative coupling of methane (OCM) produces ethylene and ethane, both species that increase fuel reactivity, thus increasing the potential to expand the operability range of highly efficient compression ignition combustion in natural gas engines. This paper presents the first experimental results on the impact of OCM product species on engine thermal efficiency and operability range. In the work, a benchtop experiment was conducted to generate a product species distribution from OCM over a Sr/La2O3 catalyst. A computational study using known chemical mechanisms was then employed to investigate the laminar flame speed and ignition delay of the OCM-modified fuel. Finally, engine experiments in both spark-ignition and compression-ignition combustion modes were carried out using a variable compression ratio single-cylinder engine. Results from the benchtop catalyst experiments showed that practical fuel conversion for single-pass OCM resulted in 18 % methane conversion, 60 % C2 selectivity, and 10.8 % C2 yield at a molar C/O ratio of 6. After determining realistic fuel blending ratios for engine operation, the numerical simulation results showed that fuel reactivity and ignition delay improved compared to with methane alone, while laminar flame speed decreased due to higher dilution from the presence of inert OCM products. Engine experimental results confirmed that OCM products have an advantage in CI mode due to reduced ignition delay time. The CI operating range was widely expanded, and approximately 9.9% thermal efficiency gain was achieved. By contrast, efficiency in SI mode was reduced when using OCM products due to an increase in combustion duration and retarded combustion phasing.

Original languageEnglish (US)
Article number116030
JournalEnergy Conversion and Management
Volume268
DOIs
StatePublished - Sep 15 2022

Bibliographical note

Funding Information:
This material is based upon work supported by the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE) under Award Number DE-EE0008333. The authors would also like to acknowledge Daniel Olsen at Colorado State University for providing the ARIES82 mechanism for use in the modeling presented in this paper. Pinaki Pal from Argonne National Laboratory is also acknowledged for providing the 3D CFD mesh and CAD model used to validate experimental data.

Funding Information:
This material is based upon work supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under Award Number DE-EE0008333. The authors would also like to acknowledge Daniel Olsen at Colorado State University for providing the ARIES82 mechanism for use in the modeling presented in this paper. Pinaki Pal from Argonne National Laboratory is also acknowledged for providing the 3D CFD mesh and CAD model used to validate experimental data.

Publisher Copyright:
© 2022 The Author(s)

Keywords

  • Combustion properties
  • Internal combustion engines
  • Natural gas
  • Oxidative coupling of methane

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