TY - JOUR
T1 - Experimental evaluation of flame observables for simplified scalar dissipation rate measurements in laminar diffusion flamelets
AU - Bijjula, Kowtilya
AU - Kyritsis, Dimitrios C.
N1 - Publisher Copyright:
© 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
PY - 2005
Y1 - 2005
N2 - We present a comparative evaluation of the potential of several flame observables to yield a simplified measurement of the scalar dissipation rate (v). The realization of the importance of this quantity for the structure of diffusion flamelets has led to brilliant experimental efforts targeted to its measurement, with a particular emphasis on xstoich, i.e., its value at the stoichiometric surface, which has been shown to control extinction. Such measurements require a significant amount of experimental resources, since they necessitate the simultaneous acquisition of multi-scalar data. The possibility of a simplified measurement stems from the realization that the related gradient of the mixture fraction scales as the inverse of an appropriately defined thickness of the mixing layer. In this paper, we investigate experimentally the utilization of several flame observables for the measurement of this thickness. In a flat, nitrogen diluted, counterflow, methane/oxygen diffusion flame, the scalar dissipation rate was first measured directly using line Raman imaging of major species and a N2-molecule based definition of the mixture fraction. Additionally, LIF measurements of the hydroxyl radical (OH) and formaldehyde (HCHO) as well as Raman measurements of carbon monoxide (CO) were performed across the flamelet. The precision of xstoich estimates based on the thickness of the layers of these three observables as well as the layers corresponding to [HCHO] × [OH] and [CO] × [OH] ''overlap'' zones was evaluated in terms of following the theoretically expected inversesquare-root dependence on strain rate. Also, the absolute thickness of these layers was recorded, since it may restrict the application of simplified techniques in turbulent flow fields.
AB - We present a comparative evaluation of the potential of several flame observables to yield a simplified measurement of the scalar dissipation rate (v). The realization of the importance of this quantity for the structure of diffusion flamelets has led to brilliant experimental efforts targeted to its measurement, with a particular emphasis on xstoich, i.e., its value at the stoichiometric surface, which has been shown to control extinction. Such measurements require a significant amount of experimental resources, since they necessitate the simultaneous acquisition of multi-scalar data. The possibility of a simplified measurement stems from the realization that the related gradient of the mixture fraction scales as the inverse of an appropriately defined thickness of the mixing layer. In this paper, we investigate experimentally the utilization of several flame observables for the measurement of this thickness. In a flat, nitrogen diluted, counterflow, methane/oxygen diffusion flame, the scalar dissipation rate was first measured directly using line Raman imaging of major species and a N2-molecule based definition of the mixture fraction. Additionally, LIF measurements of the hydroxyl radical (OH) and formaldehyde (HCHO) as well as Raman measurements of carbon monoxide (CO) were performed across the flamelet. The precision of xstoich estimates based on the thickness of the layers of these three observables as well as the layers corresponding to [HCHO] × [OH] and [CO] × [OH] ''overlap'' zones was evaluated in terms of following the theoretically expected inversesquare-root dependence on strain rate. Also, the absolute thickness of these layers was recorded, since it may restrict the application of simplified techniques in turbulent flow fields.
KW - Combustion measurements
KW - Laminar flamelet
KW - Laser induced fluorescence
KW - Raman imaging
KW - Scalar dissipation rate
UR - http://www.scopus.com/inward/record.url?scp=84964304844&partnerID=8YFLogxK
U2 - 10.1016/j.proci.2004.08.029
DO - 10.1016/j.proci.2004.08.029
M3 - Conference article
AN - SCOPUS:84964304844
SN - 1540-7489
VL - 30
SP - 493
EP - 500
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 1
T2 - 30th International Symposium on Combustion
Y2 - 25 July 2004 through 30 July 2004
ER -