PERFORMANCE OF A PLASMA JET IGNITER
The main advantage of jet igniters lies in their ability to provide distributed ignition sources that are capable of initiating and enhancing combustion in lean mixtures. This is achieved principally by two mechanisms, i.e., the provision of a high concentration of free radicals, enhancing ignition at lower temperatures, and of the extended highly turbulent igniting surface, yielding larger flame front areas and hence increased burning rates. Experimental and analytical procedures that were developed to determine the performance of a jet igniter with particular emphasis on the fluid mechanic effects are described. To de-emphasize the thermochemical effects, the plasma medium and energy were maintained without change for all the tests. Thus the only variables pertained just to the volume of the cylindrical plasma cavity and the area of the orifice discharging the jet. The results are based on high speed schlieren cinematography of the combustion process in a cylindrical bomb, and simultaneous pressure transducer measurements. The penetration depth is shown to be proportional to the square root of the characteristic length - the ratio of the volume of igniter cavity to its orifice area. The capability to ignite lean mixtures is demonstrated by the repeatibility of results attained with the use of methane-air mixtures at an equivalence ratio of 0.6, initially at atmospheric pressure and room temperature. Under these conditions the observed enhancement of the rate of combustion could be accounted for entirely by the fact that the flame surface was enlarged due to ignition by a highly turbulent jet. While the laminar burning velocity was well within the range reported in the literature, the corresponding turbulent burning velocity was about three times greater, the ratio between the two remaining nearly constant throughout the process.
- SAE automotive engineering congress and exposition, Detroit, MI, USA, 25 Feb 1980.
University of California, BerkeleyLawrence Berkeley National Laboratory
Berkeley, CA USA 94720
Department of Energy1000 Independence Avenue, SW
Washington, DC USA 20585
- Cetegen, B
- Teichman, K Y
- Weinberg, F J
- OPPENHEIM, A K
- Publication Date: 1980-1
- Pagination: 42 p.
- TRT Terms: Automobiles; Cinematography; Combustion; Ignition systems; Internal combustion engines; Kinetics; Lean fuel mixtures; Mathematical models; Methane; Performance; Temperature; Vehicle power plants
- Old TRIS Terms: Automobile engines; Combustion kinetics; Lean fuel engine; Plasma jets
- Subject Areas: Highways; Vehicles and Equipment; I96: Vehicle Operating Costs;
- Accession Number: 00318285
- Record Type: Publication
- Source Agency: National Technical Information Service
- Report/Paper Numbers: CONF-800202-3
- Contract Numbers: W-7405-ENG-48
- Files: TRIS
- Created Date: Sep 16 1981 12:00AM