Analytical, experimental and computational investigation of the influence of stoichiometric mixture fraction on structure and extinction of laminar, nonpremixed methane flames and ethane flames
(2016) 2016 Spring Technical Meeting of the Western States Section of the Combustion Institute, WSSCI 2016 Abstract
Fundamental studies on combustion in laminar, nonpremixed flames are often carried out using conserved scalar quantities. These conserved scalar quantities, represented here by mixture fraction, E, are used as independent variables in activationenergy asymptotic analysis and in rateratio asymptotic analysis. These analyses are carried out in the asymptotic limit of large Damköhler number, with chemical reactions presumed to take place in a thin reaction zone, that is located at E = Est. The quantity Est is the stoichiometric mixture fraction. A characteristic diffusion time is given by the reciprocal of the scalar dibipation rate, X. Previous computational studies have shown that the scalar dibipation rate at extinction depends on Est... (More)
Fundamental studies on combustion in laminar, nonpremixed flames are often carried out using conserved scalar quantities. These conserved scalar quantities, represented here by mixture fraction, E, are used as independent variables in activationenergy asymptotic analysis and in rateratio asymptotic analysis. These analyses are carried out in the asymptotic limit of large Damköhler number, with chemical reactions presumed to take place in a thin reaction zone, that is located at E = Est. The quantity Est is the stoichiometric mixture fraction. A characteristic diffusion time is given by the reciprocal of the scalar dibipation rate, X. Previous computational studies have shown that the scalar dibipation rate at extinction depends on Est and the maximum flame temperature, Tst. Here a rateratio asymptotic analysis is carried out using reduced chemistry to elucidate the influence of Est on critical conditions of extinction. The scalar dibipation rate at extinction was predicted as a function of Est with the mab fractions of reactants so chosen that the adiabatic flame temperature, Tst, is fixed. The predictions of the analysis show that with increasing values of Est, the scalar dibipation rate at extinction first increases and then decreases. To test the predictions of the asymptotic analysis critical conditions of extinction are measured on nonpremixed methane flames stabilized in the counterflow configuration. With increasing values of stoichiometric mixture fraction, the strain rate at extinction was found to increase and the scalar dibipation rate at extinction was found to first increase and then decrease. The predictions of the asymptotic analysis agreed with experiments. A key outcome of the analysis is that with increasing Est the thickneb of the regions where oxygen and fuel are consumed first increase and the decrease. This is responsible for the observed nonmonotonic changes in the values of the scalar dibipation rate at extinction with changes in Est.
(Less)
 author
 Mairhofer, Philipp; Seshadri, Kalyanasundaram; Bai, Xue Song ^{LU} ; Narayanaswamy, Krithika; Raghavan, Vasudevan and Pucher, Ernst
 organization
 publishing date
 2016
 type
 Chapter in Book/Report/Conference proceeding
 publication status
 published
 subject
 host publication
 2016 Spring Technical Meeting of the Western States Section of the Combustion Institute, WSSCI 2016
 publisher
 Western States Section/Combustion Institute
 conference name
 2016 Spring Technical Meeting of the Western States Section of the Combustion Institute, WSSCI 2016
 conference location
 Seattle, United States
 conference dates
 20160321  20160322
 external identifiers

 scopus:84979581150
 ISBN
 9781510823969
 language
 English
 LU publication?
 yes
 id
 34375f2d1db241f0bbe2dc6dcb6eb896
 date added to LUP
 20170208 10:04:51
 date last changed
 20191015 05:59:08
@inproceedings{34375f2d1db241f0bbe2dc6dcb6eb896, abstract = {<p>Fundamental studies on combustion in laminar, nonpremixed flames are often carried out using conserved scalar quantities. These conserved scalar quantities, represented here by mixture fraction, E, are used as independent variables in activationenergy asymptotic analysis and in rateratio asymptotic analysis. These analyses are carried out in the asymptotic limit of large Damköhler number, with chemical reactions presumed to take place in a thin reaction zone, that is located at E = Est. The quantity Est is the stoichiometric mixture fraction. A characteristic diffusion time is given by the reciprocal of the scalar dibipation rate, X. Previous computational studies have shown that the scalar dibipation rate at extinction depends on Est and the maximum flame temperature, Tst. Here a rateratio asymptotic analysis is carried out using reduced chemistry to elucidate the influence of Est on critical conditions of extinction. The scalar dibipation rate at extinction was predicted as a function of Est with the mab fractions of reactants so chosen that the adiabatic flame temperature, Tst, is fixed. The predictions of the analysis show that with increasing values of Est, the scalar dibipation rate at extinction first increases and then decreases. To test the predictions of the asymptotic analysis critical conditions of extinction are measured on nonpremixed methane flames stabilized in the counterflow configuration. With increasing values of stoichiometric mixture fraction, the strain rate at extinction was found to increase and the scalar dibipation rate at extinction was found to first increase and then decrease. The predictions of the asymptotic analysis agreed with experiments. A key outcome of the analysis is that with increasing Est the thickneb of the regions where oxygen and fuel are consumed first increase and the decrease. This is responsible for the observed nonmonotonic changes in the values of the scalar dibipation rate at extinction with changes in Est.</p>}, author = {Mairhofer, Philipp and Seshadri, Kalyanasundaram and Bai, Xue Song and Narayanaswamy, Krithika and Raghavan, Vasudevan and Pucher, Ernst}, isbn = {9781510823969}, language = {eng}, location = {Seattle, United States}, publisher = {Western States Section/Combustion Institute}, title = {Analytical, experimental and computational investigation of the influence of stoichiometric mixture fraction on structure and extinction of laminar, nonpremixed methane flames and ethane flames}, year = {2016}, }