A Computational Investigation of Diesel and Biodiesel Combustion and NOx Formation in a Light-Duty Compression Ignition Engine

Diesel and biodiesel combustion in a multi-cylinder light duty diesel engine were simulated during a closed cycle (from Intake Valve Closure (IVC) to EVO), using a commercial computational fluid dynamics (CFD) code, CONVERGE, coupled with detailed chemical kinetics. The computational domain was constructed based on engine geometry and compression ratio measurements. A skeletal n-heptane-based diesel mechanism developed by researchers at Chalmers University of Technology and a reduced biodiesel mechanism derived and validated by Luo and co-workers were applied to model the combustion chemistry. The biodiesel mechanism contains 89 species and 364 reactions and uses methyl decanoate, methyl-9-decenoate, and n-heptane as the surrogate fuel mixture. The Kelvin-Helmholtz and Rayleigh-Taylor (KH-RT) spray breakup model for diesel and biodiesel was calibrated to account for the differences in physical properties of the fuels which result in variations in atomization and spray development characteristics. The simulations were able to capture the experimentally observed pressure and apparent heat release rate trends for both the fuels over a range of engine loads (brake mean effective pressures (BMEPs) from 2.5 to 10 bar) and fuel injection timings (from 0 degrees BTDC to 10 degrees BTDC), thus validating the overall modeling approach as well as the chemical kinetic models of diesel and biodiesel surrogates. Moreover, quantitative NOx predictions for diesel combustion and qualitative NOx predictions for biodiesel combustion were obtained with the CFD simulations and the in-cylinder temperature trends were correlated to the NOx trends.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; References; Tables;
  • Pagination: 11p

Subject/Index Terms

Filing Info

  • Accession Number: 01605666
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jun 8 2016 4:26PM