International Journal of Automotive Technology

, Volume 16, Issue 5, pp 721–731 | Cite as

Effects of argon dilution on the thermal efficiency and exhaust emissions of a NG engine

  • W. F. Li
  • Z. C. Liu
  • J. TianEmail author
  • Z. S. Wang
  • Y. Xu


Argon (Ar) is the third most common gas in the Earth’s atmosphere. About 700,000 tonnes of Ar are produced worldwide every year. Ar is inexpensive since it occurs naturally in air, and is readily obtained as a byproduct of cryogenic air separation in the production of O2 and N2. To decrease NOx emissions and slightly improve the thermal efficiency, Ar has been used in ICE before. However, it appears that it was used only in diesel and gasoline engines. This paper presents the effects of Ar dilution on the thermal efficiency and NOx emissions of a 6-cylinder natural gas SI engine. Ar was added into the intake charge at fixed boundaries under 1450 rpm and 50% load. The results show that the thermal efficiency increases first and then decreases with NOx emissions being decreased significantly as the dilution ratio (DR) of Ar increases. The thermal efficiency peaks at 9.8% DR with NOx emissions being decreased by 31.1%. At the maximum DR (18.4%), the thermal efficiency decreases by 0.3% with NOx emissions being decreased by 64.0%. Furthermore, from comparative experimental results it can be concluded that Ar dilution is superior in maintaining higher thermal efficiencies than CO2 and N2 for NG engines.

Key Words

CNG engine Argon dilution Combustion Thermal efficiency NOx emissions 



air fuel ratio




brake mean effective pressure


before top-dead-centre


crank angle


compressed natural gas


carbon monoxide


carbon dioxide


cycle to cycle variations


specific heat capacity at constant pressure


heat capacity of mixture at constant pressure


specific heat capacity at constant volume


heat capacity of mixture at constant volume


dilution ratio


exhaust gas recirculation






internal combustion engine


manifold air pressure


mass flow controller


mass flow meter




natural gas


nitrogen oxides




pressure in the cylinder


parts per million


pump mean effective pressure


selective catalytic reduction


spark ignition


spark timing


temperature in the cylinder


total hydrocarbon


three-way catalyst


excess air ratio


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Copyright information

© The Korean Society of Automotive Engineers and Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • W. F. Li
    • 1
  • Z. C. Liu
    • 1
  • J. Tian
    • 1
    Email author
  • Z. S. Wang
    • 1
  • Y. Xu
    • 1
  1. 1.State Key Laboratory of Automotive Simulation and ControlJilin UniversityChangchunChina

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