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Title: Turbulence-chemistry interaction in lean premixed hydrogen combustion

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Journal Article: Publisher's Accepted Manuscript
Journal Name:
Proceedings of the Combustion Institute
Additional Journal Information:
Journal Volume: 35; Journal Issue: 2; Related Information: CHORUS Timestamp: 2017-05-17 09:45:24; Journal ID: ISSN 1540-7489
Country of Publication:
United States

Citation Formats

Aspden, A. J., Day, M. S., and Bell, J. B. Turbulence-chemistry interaction in lean premixed hydrogen combustion. United States: N. p., 2015. Web. doi:10.1016/j.proci.2014.08.012.
Aspden, A. J., Day, M. S., & Bell, J. B. Turbulence-chemistry interaction in lean premixed hydrogen combustion. United States. doi:10.1016/j.proci.2014.08.012.
Aspden, A. J., Day, M. S., and Bell, J. B. 2015. "Turbulence-chemistry interaction in lean premixed hydrogen combustion". United States. doi:10.1016/j.proci.2014.08.012.
title = {Turbulence-chemistry interaction in lean premixed hydrogen combustion},
author = {Aspden, A. J. and Day, M. S. and Bell, J. B.},
abstractNote = {},
doi = {10.1016/j.proci.2014.08.012},
journal = {Proceedings of the Combustion Institute},
number = 2,
volume = 35,
place = {United States},
year = 2015,
month = 1

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.proci.2014.08.012

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Cited by: 21works
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  • We present numerical simulations of lean hydrogen flames interacting with turbulence. The simulations are performed in an idealized setting using an adaptive low Mach number model with a numerical feedback control algorithm to stabilize the flame. At the conditions considered here, hydrogen flames are thermodiffusively unstable, and burn in cellular structures. For that reason, we consider two levels of turbulence intensity and a case without turbulence whose dynamics is driven by the natural flame instability. An overview of the flame structure shows that the burning in the cellular structures is quite intense, with the burning patches separated by regions inmore » which the flame is effectively extinguished. We explore the geometry of the flame surface in detail, quantifying the mean and Gaussian curvature distributions and the distribution of the cell sizes. We next characterize the local flame speed to quantify the effect of flame intensification on local propagation speed. We then introduce several diagnostics aimed at quantifying both the level of intensification and diffusive mechanisms that lead to the intensification. (author)« less
  • A modeling study of N{sub 2}O chemistry in lean, premixed, atmospheric-pressure combustion is presented. Laminar flame and homogeneous combustion modeling calculations were performed using the PREMIX and CHEMKIN codes, respectively. Four systems containing H{sub 2}, O{sub 2}, Ar, and an N-containing dopant (NH{sub 3}, NO, or N{sub 2}O) were modeled and compared to recent flat-flame burner experiments. Agreement between measured and computed N{sub 2}O, NO, and N{sub 2} concentration profiles indicated that the model is a reasonable representation of the chemistry and transport in the flame system. The effects of assumed burner temperature, temperature profile shape, mass diffusion, and probingmore » are investigated. A sensitivity analysis of the flame calculations is presented. For cases where burner temperatures were identical but temperatures were either determined by solving the energy equation numerically or were specified to be equivalent to measured temperatures, calculated N{sub 2}O, NO, and N{sub 2} profiles differed by 2%-15%. Calculations that differed only in specified flameholder surface temperature (400-1000 K) produced concentration profiles that varied by approximately 20% in NO and N{sub 2} and by as much as a factor of 7 in N{sub 2}O.« less
  • The velocity-composition probability density function (pdf) model coupled with a k-{var{underscore}epsilon}-based mean flow computational fluid dynamics (CFD) model was used to describe the turbulent fluid flow, heat transfer, chemistry, and their interactions in a bluff-body, lean, premixed, methane-air combustor. Measured data including velocity, temperature, and chemical species concentrations were used to evaluate the model. The chemistry calculations were performed with an in situ look-up tabulation method. A reduced, 5-step chemical mechanism for describing fuel oxidation, CO, and NO chemistry was used in the model. NO formation from thermal, N{sub 2}O-intermediate, and prompt pathways was included in the 5-step mechanism. Anmore » axisymmetric, unstructured grid was used for solving the Eulerian, mean flow equations and the vertices were used to store mean statistics for solving the Lagrangian, fluid particle equations. Predicted velocity and composition mean statistics were compared to measurements in the bluff-body combustor for a lean equivalence ratio of 0.59. The predictions of major species matched measured and calculated equilibrium values in the recirculation zone. Comparisons of mean CO throughout the combustor were always within an order of magnitude and showed marked improvements over past predictions. Maximum discrepancies between measured and predicted NO concentration were between 5 and 7 ppm ({approximately}50%). The accessed composition space in this turbulent combustion simulation represented the values of species mole fraction and enthalpy for each fluid particle at each time step and was found to lie in a relatively small, uniquely shaped region that was dictated by the mixing, reaction, and heat transfer in the combustor. This accessed composition region was obtained in situ and required about 35 megabytes of storage once a steady state was reached.« less
  • Ultra-lean, hydrogen-air mixtures are found to support another kind of laminar flame that is steady and stable beside flat flames and flame balls. Direct numerical simulations are performed of flames that develop into steadily and stably propagating cells. These cells were the original meaning of the word"flamelet'' when they were observed in lean flammability studies conducted early in the development of combustion science. Several aspects of these two-dimensional flame cells are identified and are contrasted with the properties of one-dimensional flame balls and flat flames. Although lean hydrogen-air flames are subject to thermo-diffusive effects, in this case the result ismore » to stabilize the flame rather than to render it unstable. The flame cells may be useful as basic components of engineering models for premixed combustion when the other types of idealized flames are inapplicable.« less
  • A numerical model for the partially stirred reactor (PaSR) is developed, and the effects of turbulence on NO, CO, and other quantities are computed. Turbulent mixing is accounted for by the Interaction-by-Exchange-with-the-Mean submodel. Combustion of a 50% CO/50% H[sub 2] (by vol.) fuel premixed with air is considered, represented by 18 species and 43 reactions. In the limit of mixing frequency becoming small, the solutions tend to those of the plug flow as expected. NO and CO increase with mixing frequency. In the range of time scales relevant to turbulent combustion, NO increases by a factor of about 2 asmore » the mixing time becomes small enough to effect the concentration of oxyhydrogen radical while CO increases by over an order of magnitude. These variations agree qualitatively with experimental data from turbulent combustors. In-combustor stirring clearly plays a large role even in premixed combustion. The algorithm converges to the perfectly stirred reactor solution at large mixing frequencies. The partial equilibrium model is found to be reasonable for CO/H[sub 2] fuels int eh present range of conditions, and effects a computational speedup by a factor on the order of 100. Besides providing a useful combustion model, the PaSR provides a test-bed for mixing models, for simplified chemical schemes, and for algorithms intended for particle-tracking pdf transport models.« less