Implications of detailed and global kinetics on the first-stage ignition delay in NTC-affected phenomena

Peng Zhao, Chung King Law

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Computation was first performed for the first-stage ignition delay, τ1, in the homogeneous autoignition of n-heptane/air mixtures. Results show that τ1 possesses a minimum value, τ1,min, in that it first decreases and then increases with increasing temperature, and that τ1 is largely insensitive to the equivalence ratio (ρ) and pressure (p) of the mixture when the temperature is sufficiently below the initial temperature corresponding to τ1,min. This is consistent with the experimental results from shock tubes and rapid compression machines. Furthermore, in this regime the global reaction order was found to be close to unity, hence supporting the notion that the limiting steps in this temperature regime are the RH2 isomerization reactions, which in turn explains the insensitivity of τ1 on ρ and p. However, when the temperature approaches that of τ1,min, competition of the β scission reactions of the alkyl radicals with the lowtemperature chemistry chain reactions as well as the equilibrium shift of the oxygen combination reactions increases the first-stage ignition delay and consequently results in τ1,min. The corresponding global reaction order also increases, to about two, indicating the progressive importance of the oxygen combination reactions. Additional simulation of ignition in the nonpremixed counterflow showed that the characteristic time scale given by the critical strain rate, hence the reaction order, also follows the same density (pressure) dependence as those for τ1 and τ1,min, indicating the preservation and thereby essential role of the NTC-chemistry in transport-affected ignition.

Original languageEnglish (US)
Title of host publication8th US National Combustion Meeting 2013
PublisherWestern States Section/Combustion Institute
Pages334-340
Number of pages7
ISBN (Electronic)9781627488426
StatePublished - Jan 1 2013
Event8th US National Combustion Meeting 2013 - Park City, United States
Duration: May 19 2013May 22 2013

Publication series

Name8th US National Combustion Meeting 2013
Volume1

Other

Other8th US National Combustion Meeting 2013
CountryUnited States
CityPark City
Period5/19/135/22/13

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Mechanical Engineering
  • Physical and Theoretical Chemistry

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  • Cite this

    Zhao, P., & Law, C. K. (2013). Implications of detailed and global kinetics on the first-stage ignition delay in NTC-affected phenomena. In 8th US National Combustion Meeting 2013 (pp. 334-340). (8th US National Combustion Meeting 2013; Vol. 1). Western States Section/Combustion Institute.