Effects of molar expansion ratio of fuels on engine efficiency

Nguyen, Duc-Khanh; Szybist, James; Sileghem, Louis; Verhelst, Sebastian

doi:10.1016/j.fuel.2019.116743

Title: Effects of molar expansion ratio of fuels on engine efficiency

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Abstract

Fuel properties have a strong impact on the efficiency of internal combustion engines. Contrary to other physical and thermochemical fuel properties, the molar expansion ratio is normally ignored. Molar expansion ratio is the ratio of number of moles of the products to the reactants. In this work, the impact of the fuel’s molar expansion ratio on engine efficiency is investigated. Findings are based on simulations of a spark ignition engine using different fuels (standard fuels and user-defined fuels) and different dilution ratios. Simulations without heat transfer and friction were performed first. The combustion then takes place at top dead center with a very short combustion duration to approach the ideal Otto cycle. The heat transfer and friction were then added step by step. From this analysis, it could be concluded that the heat loss and friction work decrease as molar expansion ratio increases. The gross indicated and brake thermal efficiencies thus increase. User-defined fuels with different molar expansion ratio, but the same physical and thermochemical properties were then employed. The simulated results showed that the brake thermal efficiency increases by around 1.15% with an increase in molar expansion ratio of 0.02 compared to a fuel with a molar expansion ratiomore »« less

Authors:

Nguyen, Duc-Khanh ^[1];

^[2]; Sileghem, Louis ^[1]; Verhelst, Sebastian ^[3]

Ghent Univ., Ghent (Belgium)
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Ghent Univ., Ghent (Belgium); Lund Univ. (Sweden)

Publication Date:: 2020-03-01

Research Org.:: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:: USDOE Office of Energy Efficiency and Renewable Energy (EERE)

OSTI Identifier:: 1607051

Grant/Contract Number:: AC05-00OR22725

Resource Type:: Accepted Manuscript

Journal Name:: Fuel

Additional Journal Information:: Journal Volume: 263; Journal Issue: C; Journal ID: ISSN 0016-2361

Publisher:: Elsevier

Country of Publication:: United States

Language:: English

Subject:: 42 ENGINEERING; Molar expansion ratio; Fuel properties; Spark-ignition engines; Energy losses; Engine efficiency

Citation Formats


                    Nguyen, Duc-Khanh, Szybist, James, Sileghem, Louis, and Verhelst, Sebastian. Effects of molar expansion ratio of fuels on engine efficiency.  United States: N. p., 2020. 
Web.  doi:10.1016/j.fuel.2019.116743.

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                    Nguyen, Duc-Khanh, Szybist, James, Sileghem, Louis, & Verhelst, Sebastian. Effects of molar expansion ratio of fuels on engine efficiency.  United States.  https://doi.org/10.1016/j.fuel.2019.116743

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                    Nguyen, Duc-Khanh, Szybist, James, Sileghem, Louis, and Verhelst, Sebastian. Sun .  
"Effects of molar expansion ratio of fuels on engine efficiency".  United States.  https://doi.org/10.1016/j.fuel.2019.116743.  https://www.osti.gov/servlets/purl/1607051.

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@article{osti_1607051,

  title        = {Effects of molar expansion ratio of fuels on engine efficiency},

  author       = {Nguyen, Duc-Khanh and Szybist, James and Sileghem, Louis and Verhelst, Sebastian},

  abstractNote = {Fuel properties have a strong impact on the efficiency of internal combustion engines. Contrary to other physical and thermochemical fuel properties, the molar expansion ratio is normally ignored. Molar expansion ratio is the ratio of number of moles of the products to the reactants. In this work, the impact of the fuel’s molar expansion ratio on engine efficiency is investigated. Findings are based on simulations of a spark ignition engine using different fuels (standard fuels and user-defined fuels) and different dilution ratios. Simulations without heat transfer and friction were performed first. The combustion then takes place at top dead center with a very short combustion duration to approach the ideal Otto cycle. The heat transfer and friction were then added step by step. From this analysis, it could be concluded that the heat loss and friction work decrease as molar expansion ratio increases. The gross indicated and brake thermal efficiencies thus increase. User-defined fuels with different molar expansion ratio, but the same physical and thermochemical properties were then employed. The simulated results showed that the brake thermal efficiency increases by around 1.15% with an increase in molar expansion ratio of 0.02 compared to a fuel with a molar expansion ratio of unity. Lastly, the simulation was also done with air and exhaust gas recirculation dilution.},

  doi          = {10.1016/j.fuel.2019.116743},

  journal      = {Fuel},

  number       = C,

  volume       = 263,

  place        = {United States},

  year         = {2020},

  month        = {3}

}

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