Reference natural gas flames at nominally autoignitive engine-relevant conditions

Journal Article · Fri Nov 02 00:00:00 EDT 2018 · Proceedings of the Combustion Institute

DOI:https://doi.org/10.1016/j.proci.2018.06.050· OSTI ID:1497648

Krisman, Alex ^[1]; Mounaïm-Rousselle, Christine ^[2]; Sivaramakrishnan, Raghu ^[3]; A. Miller, James ^[3]; H. Chen, Jacqueline ^[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

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 ${\tau }_l={\delta }_l/s_l$ due to the explosive thermochemical state. The corresponding reference values, s_R, δ_R, and ${\tau }_R={\delta }_R/s_R,$ 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.

• Research Organization: Sandia National Lab. (SNL-CA), Livermore, CA (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: NA0003525; AC02-06CH11357
• OSTI ID: 1497648
• Alternate ID(s): OSTI ID: 1513216; OSTI ID: 1637111
• Report Number(s): SAND2017--13739J; 672187
• Journal Information: Proceedings of the Combustion Institute, Journal Name: Proceedings of the Combustion Institute Journal Issue: 2 Vol. 37; ISSN 1540-7489
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
autoignition
engine-relevant conditions
laminar flame speed
natural gas