Structure and propagation of two-dimensional, partially premixed, laminar flames in diesel engine conditions

Journal Article · Thu Jul 12 00:00:00 EDT 2018 · Proceedings of the Combustion Institute

DOI:https://doi.org/10.1016/j.proci.2018.06.169· OSTI ID:1497650

Dalakoti, Deepak K. ^[1]; Krisman, Alex ^[2]; Savard, Bruno ^[1]; Wehrfritz, Armin ^[1]; Wang, Haiou ^[1]; Day, Marc S. ^[3]; Bell, John B. ^[3]; Hawkes, Evatt R. ^[4]

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1. Univ. of New South Wales, Sydney, NSW (Australia). School of Mechanical and Manufacturing Engineering
2. Sandia National Lab. (SNL-CA), Livermore, CA (United States). Combustion Research Facility
3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Center for Computational Sciences and Engineering
4. Univ. of New South Wales, Sydney, NSW (Australia). School of Mechanical and Manufacturing Engineering. School of Photovoltaic and Renewable Energy Engineering

We investigate here the influence of inflow velocity (V_in) and scalar dissipation rate (χ) on the flame structure and stabilisation mechanism of steady, laminar partially premixed n-dodecane edge flames stabilised on a convective mixing layer. Numerical simulations were performed for three different χ profiles and several V_in (V_in = 0.2 to 2.5m/s). The ambient thermochemical conditions were the same as the Engine Combustion Network’s (ECN) Spray A flame, which in turn represents conditions in a typical heavy duty diesel engine. The results of a combustion mode analysis of the simulations indicate that the flame structure and stabilisation mechanism depend on V_in and χ. For low V_in the flame is attached. Increasing V_in causes the high-temperature chemistry (HTC) flame to lift-off, while the low-temperature chemistry (LTC) flame is still attached. A unique speed S_R associated with this transition is defined as the velocity at which the lifted height has the maximum sensitivity to changes in Vin. This transition velocity is negatively correlated with χ. Near $V_{in}=S_R$ a tetrabrachial flame structure is observed consisting of a triple flame, stabilised by flame propagation into the products of an upstream LTC branch. Further increasing the inlet velocity changes the flame structure to a pentabrachial one, where an additional HTC ignition branch is observed upstream of the triple flame and ignition begins to contribute to the flame stabilisation. At large V_in, the LTC is eventually lifted, and the speed at which this transition occurs is insensitive to χ. Further increasing V_in increases the contribution of ignition to flame stabilisation until the flame is completely ignition stabilised. Flow divergence caused by the LTC branch reduces the χ at the HTC branches making the HTC more resilient to χ. The results are discussed in the context of identification of possible stabilisation modes in turbulent flames.

• Research Organization: Sandia National Lab. (SNL-CA), Livermore, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of New South Wales, Sydney, NSW (Australia)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Australian Research Council (ARC)
• Grant/Contract Number: NA0003525; AC02-05CH11231
• OSTI ID: 1497650
• Alternate ID(s): OSTI ID: 1694200
• Report Number(s): SAND2017--13725J; 672183
• 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

42 ENGINEERING
Spray A
cool flame
diesel engine
edge flame
lifted flame stabilisation