The imposition of stringent motor vehicle emission standards combined with the recent demand for increased fuel economy have led to renewed interest in operating automobile engines with very lean mixtures. But, the potential for reduction of pollutants by lean combustion is lessened by increased hydrocarbon emissions. Unburned hydrocarbon formation due to wall flame quenching was studied in order to observe the wall flame quenching process, combustion processes, and flow characteristics in an engine under various conditions to obtain qualitative information for clarifying wall flame quenching mechanisms and to contribute to better design of engines to reduce hydrocarbon emissions. Effects of geometry, equivalence ratio, and ignition timing on the unburned hydrocarbon formation were examined. The experiments were conducted using a model spark ignition engine. Methane was used as the fuel. Initial conditions were at atmospheric pressure and at room temperature for all cases. Five pistons with different geometries were used in an attempt to examine the flow variations. The major results were: a quench layer was observed along the cylinder walls and its thickness was of the same order of magnitude as that of local thermal boundary layer; piston geometry and the intake process can drastically modify the flow characteristics in an engine; the rolled-up vortex plays an important role in generating wall turbulence and the process of exhausting unburned hydrocarbons; wall turbulence strongly affects the quenching process, increasing unburned hydrocarbons; and retarded ignition timing increased and unburned hydrocarbons. The main conclusions are that wall turbulence can significantly increase the effective quench layer thickness and that the key to minimizing wall flame quenching is to reduce turbulence generated near the engine cylinder walls.

  • Corporate Authors:

    University of California, Berkeley

    Lawrence Berkeley National Laboratory
    Berkeley, CA  United States  94720

    Department of Energy

    1000 Independence Avenue, SW
    Washington, DC  United States  20585
  • Authors:
    • Ishikawa, N
  • Publication Date: 1978-8

Media Info

  • Pagination: 106 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00318286
  • Record Type: Publication
  • Source Agency: National Technical Information Service
  • Report/Paper Numbers: Thesis
  • Contract Numbers: W-7405-ENG-48
  • Files: TRIS
  • Created Date: Sep 16 1981 12:00AM