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Title: Reference natural gas flames at nominally autoignitive engine-relevant conditions

Abstract

Laminar natural gas flames are investigated at engine-relevant thermochemical conditions where the ignition delay time τ is short due to very high ambient temperatures and pressures. At these conditions, it is not possible to measure or calculate well-defined values for the laminar flame speed s l, laminar flame thickness δ l, and laminar flame time scale τ l = δ l / s l due to the explosive thermochemical state. The corresponding reference values, s R, δ R, and τ R = δ R / s R , that account for the effects of autoignition, are numerically estimated to investigate the enhancement of flame propagation, and the competition with autoignition that arises under nominally autoignitive conditions (characterised here by the number τ/τ R). Large values of τ/τ R indicate that autoignition is unimportant, values near or below unity indicate that flame propagation is not possible, and intermediate values indicate that a combination of both flame propagation and autoignition may be important, depending upon factors such as device geometry, turbulence, stratification, et cetera. The reference quantities are presented for a wide range of temperatures, equivalence ratios, pressures, and hydrogen concentrations, which includes conditions relevant to stationary gas turbine reheat burners and boosted spark ignition engines. It is demonstrated that the transition from flame propagation to autoignition is only dependent on residence time, when the results are non-dimensionalised by the reference values. The temporal evolution of the reference values are also reported for a modelled boosted SI engine. It is shown that the nominally autoignitive conditions enhance flame propagation, which may be an ameliorating factor for the onset of engine knock. The calculations are performed using a recently-developed, detailed 177 species mechanism for C0–C3 chemistry that is derived from theoretical chemistry and is suitable for a wide range of thermochemical conditions as it is not tuned or optimised for a particular operating condition.

Authors:
ORCiD logo [1];  [2]; ORCiD logo [3];  [3];  [1]
  1. Sandia National Lab. (SNL-CA), Livermore, CA (United States). Combustion Research Facility
  2. Univ. of Orléans (France). Lab. PRISME
  3. Argonne National Lab. (ANL), Argonne, IL (United States). Chemical Sciences and Engineering Division
Publication Date:
Research Org.:
Sandia National Lab. (SNL-CA), Livermore, CA (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1497648
Report Number(s):
SAND2017-13739J
Journal ID: ISSN 1540-7489; 672187
Grant/Contract Number:  
NA0003525; AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Proceedings of the Combustion Institute
Additional Journal Information:
Journal Volume: 37; Journal Issue: 2; Journal ID: ISSN 1540-7489
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
03 NATURAL GAS; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; natural gas; laminar flame speed; autoignition; engine-relevant conditions

Citation Formats

Krisman, Alex, Mounaïm-Rousselle, Christine, Sivaramakrishnan, Raghu, A. Miller, James, and H. Chen, Jacqueline. Reference natural gas flames at nominally autoignitive engine-relevant conditions. United States: N. p., 2018. Web. doi:10.1016/j.proci.2018.06.050.
Krisman, Alex, Mounaïm-Rousselle, Christine, Sivaramakrishnan, Raghu, A. Miller, James, & H. Chen, Jacqueline. Reference natural gas flames at nominally autoignitive engine-relevant conditions. United States. doi:10.1016/j.proci.2018.06.050.
Krisman, Alex, Mounaïm-Rousselle, Christine, Sivaramakrishnan, Raghu, A. Miller, James, and H. Chen, Jacqueline. Fri . "Reference natural gas flames at nominally autoignitive engine-relevant conditions". United States. doi:10.1016/j.proci.2018.06.050.
@article{osti_1497648,
title = {Reference natural gas flames at nominally autoignitive engine-relevant conditions},
author = {Krisman, Alex and Mounaïm-Rousselle, Christine and Sivaramakrishnan, Raghu and A. Miller, James and H. Chen, Jacqueline},
abstractNote = {Laminar natural gas flames are investigated at engine-relevant thermochemical conditions where the ignition delay time τ is short due to very high ambient temperatures and pressures. At these conditions, it is not possible to measure or calculate well-defined values for the laminar flame speed sl, laminar flame thickness δl, and laminar flame time scale τl=δl/sl due to the explosive thermochemical state. The corresponding reference values, sR, δR, and τR=δR/sR, that account for the effects of autoignition, are numerically estimated to investigate the enhancement of flame propagation, and the competition with autoignition that arises under nominally autoignitive conditions (characterised here by the number τ/τR). Large values of τ/τR indicate that autoignition is unimportant, values near or below unity indicate that flame propagation is not possible, and intermediate values indicate that a combination of both flame propagation and autoignition may be important, depending upon factors such as device geometry, turbulence, stratification, et cetera. The reference quantities are presented for a wide range of temperatures, equivalence ratios, pressures, and hydrogen concentrations, which includes conditions relevant to stationary gas turbine reheat burners and boosted spark ignition engines. It is demonstrated that the transition from flame propagation to autoignition is only dependent on residence time, when the results are non-dimensionalised by the reference values. The temporal evolution of the reference values are also reported for a modelled boosted SI engine. It is shown that the nominally autoignitive conditions enhance flame propagation, which may be an ameliorating factor for the onset of engine knock. The calculations are performed using a recently-developed, detailed 177 species mechanism for C0–C3 chemistry that is derived from theoretical chemistry and is suitable for a wide range of thermochemical conditions as it is not tuned or optimised for a particular operating condition.},
doi = {10.1016/j.proci.2018.06.050},
journal = {Proceedings of the Combustion Institute},
issn = {1540-7489},
number = 2,
volume = 37,
place = {United States},
year = {2018},
month = {11}
}

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