TY - JOUR
T1 - Quantitative scalar dissipation rate measurements in vortex-perturbed counterflow diffusion flames
AU - Kyritsis, Dimitrios C.
AU - Santoro, Vito S.
AU - Gomez, Alessandro
N1 - Funding Information:
The support of NSF, grant CTS-9904296 (Dr. F. Fischer, Contract Monitor) is gratefully acknowledged. The authors would like to acknowledge Prof. M. B. Long of Yale University for his insightful suggestions on the implementation of the Raman diagnostic technique.
PY - 2002
Y1 - 2002
N2 - Even though the scalar dissipation rate at the stoichiometric surface, χstoich, is recognized to be the most fundamental fluid time scale in laminar diffusion flames, their structure and extinction behavior are often characterized simply in terms of strain rate, a much more easily measurable observable. Yet, the two variables are different, especially in unsteady flamelets. An experimental technique based on line Raman imaging of major species is presented for the quantitative measurement of χstoich in vortex-perturbed counterflow diffusion flames. Three formulations are evaluated, and it is shown that a formulation based on N2-mass fraction is the most appropriate, provided that N2 is experimentally accessible and that there is no significant preferential diffusion. The technique is used to compare vortex-perturbed and quasi-steady extinction. The thesis that for a given composition of the counterflowing streams, extinction occurs at a given value of χstoich, irrespective of the mode of perturbation, steady or unsteady, is verified experimentally and is contrasted with the observation that vortex-perturbed flames can sustain an almost double strain rate at extinction compared to steadily strained ones. The effect of two-dimensional phenomena on the results is discussed. Finally, a promising approximation of χstoich using estimates of the thickness of mixing layer from temperature profiles, with significant simplifications in the required measurements, is investigated.
AB - Even though the scalar dissipation rate at the stoichiometric surface, χstoich, is recognized to be the most fundamental fluid time scale in laminar diffusion flames, their structure and extinction behavior are often characterized simply in terms of strain rate, a much more easily measurable observable. Yet, the two variables are different, especially in unsteady flamelets. An experimental technique based on line Raman imaging of major species is presented for the quantitative measurement of χstoich in vortex-perturbed counterflow diffusion flames. Three formulations are evaluated, and it is shown that a formulation based on N2-mass fraction is the most appropriate, provided that N2 is experimentally accessible and that there is no significant preferential diffusion. The technique is used to compare vortex-perturbed and quasi-steady extinction. The thesis that for a given composition of the counterflowing streams, extinction occurs at a given value of χstoich, irrespective of the mode of perturbation, steady or unsteady, is verified experimentally and is contrasted with the observation that vortex-perturbed flames can sustain an almost double strain rate at extinction compared to steadily strained ones. The effect of two-dimensional phenomena on the results is discussed. Finally, a promising approximation of χstoich using estimates of the thickness of mixing layer from temperature profiles, with significant simplifications in the required measurements, is investigated.
UR - https://www.scopus.com/pages/publications/0037966118
U2 - 10.1016/S1540-7489(02)80206-1
DO - 10.1016/S1540-7489(02)80206-1
M3 - Conference article
AN - SCOPUS:0037966118
SN - 1540-7489
VL - 29
SP - 1679
EP - 1685
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 2
T2 - 30th International Symposium on Combustion
Y2 - 25 July 2004 through 30 July 2004
ER -
