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Title: Piloted methane/air jet flames: Transport effects and aspects of scalar structure

Abstract

Previously unpublished results from multiscalar point measurements in the series of piloted CH{sub 4}/air jet flames [R.S. Barlow, J.H. Frank, Proc. Combust. Inst. 27 (1998) 1087-1095] are presented and analyzed. The emphasis is on features of the data that reveal the relative importance of molecular diffusion and turbulent transport in these flames. The complete series A-F is considered. This includes laminar, transitional, and turbulent flames spanning a range in Reynolds number from 1100 to 44,800. Results on conditional means of species mass fractions, the differential diffusion parameter, and the state of the water-gas shift reaction all show that there is an evolution in these flames from a scalar structure dominated by molecular diffusion to one dominated by turbulent transport. Long records of 6000 single-point samples at each of several selected locations in flame D are used to quantify the cross-stream (radial) dependence of conditional statistics of measured scalars. The cross-stream dependence of the conditional scalar dissipation is determined from 6000-shot, line-imaging measurements at selected locations. The cross-stream dependence of reactive scalars, which is most significant in the near field of the jet flame, is attributed to radial differences in both convective and local time scales of the flow. Results illustratemore » some potential limitations of common modeling assumptions when applied to laboratory-scale flames and, thus, provide a more complete context for interpretation of comparisons between experiments and model calculations.« less

Authors:
;  [1];  [2];  [3]
  1. Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551-0969 (United States)
  2. Department of Aerospace Engineering, Texas A and M University, College Station, TX 778453-3141 (United States)
  3. Mechanical Engineering Department, University of California, Berkeley, CA 94720 (United States)
Publication Date:
OSTI Identifier:
20681463
Resource Type:
Journal Article
Resource Relation:
Journal Name: Combustion and Flame; Journal Volume: 143; Journal Issue: 4; Other Information: Elsevier Ltd. All rights reserved
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 03 NATURAL GAS; METHANE; AIR; FLAMES; JETS; DIFFUSION; TURBULENCE; COMBUSTION KINETICS

Citation Formats

Barlow, R.S., Frank, J.H., Karpetis, A.N., and Chen, J.-Y. Piloted methane/air jet flames: Transport effects and aspects of scalar structure. United States: N. p., 2005. Web. doi:10.1016/j.combustflame.2005.08.017.
Barlow, R.S., Frank, J.H., Karpetis, A.N., & Chen, J.-Y. Piloted methane/air jet flames: Transport effects and aspects of scalar structure. United States. doi:10.1016/j.combustflame.2005.08.017.
Barlow, R.S., Frank, J.H., Karpetis, A.N., and Chen, J.-Y. Thu . "Piloted methane/air jet flames: Transport effects and aspects of scalar structure". United States. doi:10.1016/j.combustflame.2005.08.017.
@article{osti_20681463,
title = {Piloted methane/air jet flames: Transport effects and aspects of scalar structure},
author = {Barlow, R.S. and Frank, J.H. and Karpetis, A.N. and Chen, J.-Y.},
abstractNote = {Previously unpublished results from multiscalar point measurements in the series of piloted CH{sub 4}/air jet flames [R.S. Barlow, J.H. Frank, Proc. Combust. Inst. 27 (1998) 1087-1095] are presented and analyzed. The emphasis is on features of the data that reveal the relative importance of molecular diffusion and turbulent transport in these flames. The complete series A-F is considered. This includes laminar, transitional, and turbulent flames spanning a range in Reynolds number from 1100 to 44,800. Results on conditional means of species mass fractions, the differential diffusion parameter, and the state of the water-gas shift reaction all show that there is an evolution in these flames from a scalar structure dominated by molecular diffusion to one dominated by turbulent transport. Long records of 6000 single-point samples at each of several selected locations in flame D are used to quantify the cross-stream (radial) dependence of conditional statistics of measured scalars. The cross-stream dependence of the conditional scalar dissipation is determined from 6000-shot, line-imaging measurements at selected locations. The cross-stream dependence of reactive scalars, which is most significant in the near field of the jet flame, is attributed to radial differences in both convective and local time scales of the flow. Results illustrate some potential limitations of common modeling assumptions when applied to laboratory-scale flames and, thus, provide a more complete context for interpretation of comparisons between experiments and model calculations.},
doi = {10.1016/j.combustflame.2005.08.017},
journal = {Combustion and Flame},
number = 4,
volume = 143,
place = {United States},
year = {Thu Dec 01 00:00:00 EST 2005},
month = {Thu Dec 01 00:00:00 EST 2005}
}
  • Previously unpublished results from multiscalar point measurements in the series of piloted CH{sub 4}/air jet flames [R.S. Barlow, J.H. Frank, Proc. Combust. Inst. 27 (1998) 1087-1095] are presented and analyzed. The emphasis is on features of the data that reveal the relative importance of molecular diffusion and turbulent transport in these flames. The complete series A-F is considered. This includes laminar, transitional, and turbulent flames spanning a range in Reynolds number from 1100 to 44,800. Results on conditional means of species mass fractions, the differential diffusion parameter, and the state of the water-gas shift reaction all show that there ismore » an evolution in these flames from a scalar structure dominated by molecular diffusion to one dominated by turbulent transport. Long records of 6000 single-point samples at each of several selected locations in flame D are used to quantify the cross-stream (radial) dependence of conditional statistics of measured scalars. The cross-stream dependence of the conditional scalar dissipation is determined from 6000-shot, line-imaging measurements at selected locations. The cross-stream dependence of reactive scalars, which is most significant in the near field of the jet flame, is attributed to radial differences in both convective and local time scales of the flow. Results illustrate some potential limitations of common modeling assumptions when applied to laboratory-scale flames and, thus, provide a more complete context for interpretation of comparisons between experiments and model calculations.« less
  • It is shown that the Re number dependency of the mechanical-to-scalar-timescale ratio C{sub {phi}} is potentially important for Sandia flames D, E, and F, and that different constant values are preferred. It is also shown that a nonconstant model has some advantages over a constant timescale ratio. However, the model used is not sufficiently sensitive to changes in flow field conditions and thus not sufficiently general.
  • No meaningful difference is observed between the predictions with the conditional velocity modeled by linear scaling and gradient diffusion assumption for the test flames under consideration. The AMC and Girimaji's model for CSDR show similar results, while the pdf integration method results in an asymmetric profile with some deviation from the other two. The difference tends to decrease as mixing proceeds, to result in a lower level of scalar dissipation at downstream locations. Reasonable agreement is achieved with measured scalar dissipation rates at different axial locations for the Sandia Flame D, while direct comparison is difficult due to radially averagedmore » pdfs and no measured scalar dissipation rates being available for the Sydney bluff-body flame.« less