The Potential for Reducing CO and NOx Emissions from an HCCI Engine Using H2O2 Addition 2003-01-3204
The effects of hydrogen peroxide addition on iso-octane/air Homogeneous Charge Compression Ignition (HCCI) combustion have been investigated analytically. Particular attention was focused on the predications involving homogeneous gas-phase kinetics. Use was made of Peters' iso-octane mechanism in CHEMKIN and convective heat transfer was included in the analyses. This enabled the influences that H2O2 addition has on species concentration and ignition promotion and hence exhaust emissions to be determined. It was found that both CO and NOx emission levels could be ameliorated. The former effect is considered to be a result of the decomposition of H2O2 into OH intermediate species and hence reducing the time to ignition and the onset of combustion. With regards to the potential for reducing NOx, it was found that addition of H2O2 could lead to a reduction in the inlet air temperature required for the fuel/air mixture to attain auto-ignition at/near top dead centre, thereby, depressing the average cycle temperature and increasing the cycle time spent below the normal threshold temperatures required for NOx formation.