Spark-ignited engine NOx emissions in a low-nitrogen oxycombustion environment

Andrew Van Blarigan*, Darko Kozarac, Reinhard Seiser, J. Y. Chen, Robert Cattolica, Robert Dibble

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


This paper investigates the formation of the pollutant nitric oxides (NOx) in the low-nitrogen (N2) environment of methane oxycombustion in a spark-ignited (SI) internal combustion engine. Working fluid composition, N2 concentration, O2 concentration, compression ratio (CR) and spark-timing have been investigated to evaluate the feasibility of operating such a system below NOx regulation levels without after-treatment systems.NOx emissions in g/kWh are shown under equivalent CR, intake temperature, and indicated mean effective pressure (IMEP) at maximum brake torque spark-timing, to have an approximately linear dependence on N2 concentration from no N2 to normal air combustion. At a given N2 concentration, NOx emissions were found to be adversely correlated with power, thermal efficiency, and the coefficient of variation of IMEP. It was found that with 2-3% N2 by volume in the working fluid, it was possible to reduce NOx emissions to satisfy regulation levels, but this corresponds to non-ideal engine performance in other metrics. Satisfying regulations while operating at the maximum thermal efficiency required the N2 concentration be reduced to 1-2% by volume.The system was simulated using an AVL Boost model, with results indicating that the increasing NOx concentrations at higher O2 cases and earlier spark-timings can largely be attributed to higher burned-gas temperatures. An additional simulation utilizing CHEMKIN and the GRI 3.0 mechanism was used to estimate NOx formation, and with results indicating that air-calibrated NOx mechanisms maintain reasonable accuracy in low-N2 environments.

Original languageEnglish (US)
Pages (from-to)22-31
Number of pages10
JournalApplied Energy
StatePublished - Apr 1 2014
Externally publishedYes


  • Exhaust gas recirculation (EGR)
  • Experiment
  • Oxycombustion
  • SI engine
  • Simulation

ASJC Scopus subject areas

  • Mechanical Engineering
  • General Energy
  • Management, Monitoring, Policy and Law
  • Building and Construction


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