DeNOx mechanism caused by thermal cracking hydrocarbons in the stratified rich zone during diesel combustion

Y. Kidoguchi, K. Miwa, H. Noge

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


This study concerns an experimental and theoretical investigation of the deNOx mechanism caused by thermal cracking hydrocarbons during diesel combustion. A total gas sampling experiment using a rapid compression machine showed that NOx can be reduced under fuelrich and high-swirl conditions. It was found that under these conditions, a large amount of thermal cracking hydrocarbons, including unsaturated hydrocarbons such as C 2H4, are produced during the ignition delay period, and that stratified fuel-rich combustion regions that contain these thermal cracking hydrocarbons are distributed widely throughout the combustion chamber. During the diffusion combustion phase, the CH4 concentration surpasses that of C2H4 and becomes the dominant hydrocarbon species. These thermal cracking hydrocarbons are supposed to be active in NOx reduction chemistry. To confirm the assumption, a flow reactor experiment was conducted focusing on the thermal cracking process of diesel fuel and the NOx reduction process. The experiment showed that when a solvent was used as fuel, light hydrocarbons similar to those observed in the rapid compression experiment are formed, and that about 60 per cent of NOx was reduced at equivalence ratios over 2.5 and a temperature of 1500 K. In addition to the above experiments, a chemical kinetic calculation using CHEMKIN III was carried out. The calculation revealed that C2H4 is easily decomposed during its oxidation process, forming HCCO or CH2, which reacts promptly with NO and that in this reaction path, C 2H2 formed through the thermal cracking process of C 2H4 is an essential species to the formation of HCCO and CH2.

Original languageEnglish
Pages (from-to)547-556
Number of pages10
JournalInternational Journal of Engine Research
Issue number6
Publication statusPublished - Dec 2005
Externally publishedYes


  • Diesel combustion
  • Emission
  • Hydrocarbon
  • NO
  • Thermal cracking

ASJC Scopus subject areas

  • Automotive Engineering
  • Aerospace Engineering
  • Ocean Engineering
  • Mechanical Engineering


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