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Multiple-objective optimization of methanol/diesel dual-fuel engine at low loads : A comparison of reactivity controlled compression ignition (RCCI) and direct dual fuel stratification (DDFS) strategies

Li, Yaopeng LU ; Jia, Ming ; Xu, Leilei LU and Bai, Xue Song LU (2020) In Fuel 262.
Abstract

Reactivity controlled compression ignition (RCCI) engines suffer from low thermal efficiency at low loads due to the high hydrocarbon and carbon monoxide emissions. Correspondingly, a direct dual fuel stratification (DDFS) combustion mode is investigated by directly injecting methanol and diesel into cylinder. Multi-objective optimization and detailed comparison are first conducted for the two engine strategies. Compared to RCCI, the optimized DDFS case shows higher thermal efficiency, lower emissions, lower demand for the in-cylinder initial temperature, and higher potential of energy recovery. Different from the single-stage combustion in RCCI, DDFS shows a two-stage combustion, the second stage of which is owing to its near-top dead... (More)

Reactivity controlled compression ignition (RCCI) engines suffer from low thermal efficiency at low loads due to the high hydrocarbon and carbon monoxide emissions. Correspondingly, a direct dual fuel stratification (DDFS) combustion mode is investigated by directly injecting methanol and diesel into cylinder. Multi-objective optimization and detailed comparison are first conducted for the two engine strategies. Compared to RCCI, the optimized DDFS case shows higher thermal efficiency, lower emissions, lower demand for the in-cylinder initial temperature, and higher potential of energy recovery. Different from the single-stage combustion in RCCI, DDFS shows a two-stage combustion, the second stage of which is owing to its near-top dead center injection of methanol. Compared to RCCI, DDFS requires a lower initial temperature to retard combustion phasing, and a larger amount of exhaust gas recirculation rate to control nitrogen oxide and ringing intensity. The optimized methanol fraction and injection timings of diesel are similar for RCCI and DDFS, and they are determined in compromise of combustion efficiency and heat transfer loss. A large spray-included angle of diesel injector is preferable for RCCI to target diesel spray to the piston lip. In DDFS, a small spray-included angle of diesel injector is needed for more complete fuel oxidation, and a medium spray-included angle of methanol injector is required to avoid excessive heat transfer loss. Due to the non-sooting nature of methanol, DDFS produces as low soot emissions as RCCI. The present study shows that the co-optimization of operating parameters and fuel properties offers a promising approach to meet the more stringent regulation on efficiency and emission.

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author
organization
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Contribution to journal
publication status
published
subject
keywords
Co-optimization, Direct dual fuel stratification (DDFS), Dual-fuel direct injection, Hydrocarbon (HC) and carbon monoxide (CO) emissions, Methanol property, Reactivity controlled compression ignition (RCCI)
in
Fuel
volume
262
article number
116673
publisher
Elsevier
external identifiers
  • scopus:85075747912
ISSN
0016-2361
DOI
10.1016/j.fuel.2019.116673
language
English
LU publication?
yes
id
8ea8ca2a-25c6-4300-9000-4ead54512336
date added to LUP
2019-12-16 08:38:12
date last changed
2020-01-13 02:36:23
@article{8ea8ca2a-25c6-4300-9000-4ead54512336,
  abstract     = {<p>Reactivity controlled compression ignition (RCCI) engines suffer from low thermal efficiency at low loads due to the high hydrocarbon and carbon monoxide emissions. Correspondingly, a direct dual fuel stratification (DDFS) combustion mode is investigated by directly injecting methanol and diesel into cylinder. Multi-objective optimization and detailed comparison are first conducted for the two engine strategies. Compared to RCCI, the optimized DDFS case shows higher thermal efficiency, lower emissions, lower demand for the in-cylinder initial temperature, and higher potential of energy recovery. Different from the single-stage combustion in RCCI, DDFS shows a two-stage combustion, the second stage of which is owing to its near-top dead center injection of methanol. Compared to RCCI, DDFS requires a lower initial temperature to retard combustion phasing, and a larger amount of exhaust gas recirculation rate to control nitrogen oxide and ringing intensity. The optimized methanol fraction and injection timings of diesel are similar for RCCI and DDFS, and they are determined in compromise of combustion efficiency and heat transfer loss. A large spray-included angle of diesel injector is preferable for RCCI to target diesel spray to the piston lip. In DDFS, a small spray-included angle of diesel injector is needed for more complete fuel oxidation, and a medium spray-included angle of methanol injector is required to avoid excessive heat transfer loss. Due to the non-sooting nature of methanol, DDFS produces as low soot emissions as RCCI. The present study shows that the co-optimization of operating parameters and fuel properties offers a promising approach to meet the more stringent regulation on efficiency and emission.</p>},
  author       = {Li, Yaopeng and Jia, Ming and Xu, Leilei and Bai, Xue Song},
  issn         = {0016-2361},
  language     = {eng},
  publisher    = {Elsevier},
  series       = {Fuel},
  title        = {Multiple-objective optimization of methanol/diesel dual-fuel engine at low loads : A comparison of reactivity controlled compression ignition (RCCI) and direct dual fuel stratification (DDFS) strategies},
  url          = {http://dx.doi.org/10.1016/j.fuel.2019.116673},
  doi          = {10.1016/j.fuel.2019.116673},
  volume       = {262},
  year         = {2020},
}