Algorithmic determination of the mechanism through which H2O-dilution affects autoignition dynamics and NO formation in CH4/air mixtures

Tingas, Efstathios Al.; Kyritsis, Dimitrios C.; Goussis, Dimitris A.

Abstract

The Computational Singular Perturbation (CSP) algorithm is employed in order to determine how H2O-dilution influences ignition delay and chemical paths that generate NO during isochoric homogenous lean CH4/air autoignition. Regarding the ignition delay, it is shown that H2O-dilution enhances reactivity, mainly due to the increased OH production throughout the explosive stage via reaction H2O2 (+H2O) -> OH + OH(+H2O). With regard to NO generation, the relative importance of thermal and chemical effects are examined and it is concluded that both are important. The thermal effects result in a lower temperature at the end of the explosive stage, while the most notable chemical effect is the lower level of O after this stage, mainly due to the effect of H2O-dilution on the equilibrium of the reaction O + H2O OH + OH. The depletion of O, together with the thermal effect, causes a substantial decrease in final NO generation.

• Journal Article Type: Article
• Acceptance Date: Jun 9, 2016
• Online Publication Date: Jun 18, 2016
• Publication Date: 2016-11
• Deposit Date: Jun 26, 2020
• Journal: Fuel
• Print ISSN: 0016-2361
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 183
• Pages: 90-98
• DOI: https://doi.org/10.1016/j.fuel.2016.06.057
• Keywords: Autoignition; NO; Methane; Water dilution; CSP
• Public URL: http://researchrepository.napier.ac.uk/Output/2672616