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

Abstract

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 i n = 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.

Authors:
 [1]; ORCiD logo [2];  [1]; ORCiD logo [1]; ORCiD logo [1];  [3];  [3];  [4]
  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
Publication Date:
Research Org.:
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 Org.:
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)
OSTI Identifier:
1497650
Report Number(s):
SAND2017-13725J
Journal ID: ISSN 1540-7489; 672183
Grant/Contract Number:  
NA0003525; AC02-05CH11231
Resource Type:
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:
42 ENGINEERING; lifted flame stabilisation; edge flame; cool flame; diesel engine; Spray A

Citation Formats

Dalakoti, Deepak K., Krisman, Alex, Savard, Bruno, Wehrfritz, Armin, Wang, Haiou, Day, Marc S., Bell, John B., and Hawkes, Evatt R. Structure and propagation of two-dimensional, partially premixed, laminar flames in diesel engine conditions. United States: N. p., 2018. Web. doi:10.1016/j.proci.2018.06.169.
Dalakoti, Deepak K., Krisman, Alex, Savard, Bruno, Wehrfritz, Armin, Wang, Haiou, Day, Marc S., Bell, John B., & Hawkes, Evatt R. Structure and propagation of two-dimensional, partially premixed, laminar flames in diesel engine conditions. United States. doi:10.1016/j.proci.2018.06.169.
Dalakoti, Deepak K., Krisman, Alex, Savard, Bruno, Wehrfritz, Armin, Wang, Haiou, Day, Marc S., Bell, John B., and Hawkes, Evatt R. Thu . "Structure and propagation of two-dimensional, partially premixed, laminar flames in diesel engine conditions". United States. doi:10.1016/j.proci.2018.06.169. https://www.osti.gov/servlets/purl/1497650.
@article{osti_1497650,
title = {Structure and propagation of two-dimensional, partially premixed, laminar flames in diesel engine conditions},
author = {Dalakoti, Deepak K. and Krisman, Alex and Savard, Bruno and Wehrfritz, Armin and Wang, Haiou and Day, Marc S. and Bell, John B. and Hawkes, Evatt R.},
abstractNote = {We investigate here the influence of inflow velocity (Vin) 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 Vin (Vin = 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 Vin and χ. For low Vin the flame is attached. Increasing Vin causes the high-temperature chemistry (HTC) flame to lift-off, while the low-temperature chemistry (LTC) flame is still attached. A unique speed SR 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 Vin=SR 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 Vin, the LTC is eventually lifted, and the speed at which this transition occurs is insensitive to χ. Further increasing Vin 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.},
doi = {10.1016/j.proci.2018.06.169},
journal = {Proceedings of the Combustion Institute},
number = 2,
volume = 37,
place = {United States},
year = {2018},
month = {7}
}

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