The burned zone excess air ratio λd in the diffusion combustion process was analyzed using the two-zone model, and it was compared with the excess air ratio λf estimated using a steady diffusion flame model of the fuel spray. It is found that λd is dependent on the fuel spray penetration and ignition delay. If the premixed combustion fraction is less than 50%, the NO formation is minimally influenced by the excess air ratio during premixed combustion and is dependent on the excess air ratio λd which determines the maximum temperature during diffusion combustion. It is clarified by analysis of the two-zone model that the large reduction in NOx due to timing retard is mainly caused by decreases in both combustion temperature and combustion pressure, and the small reduction in NOx occurring when the nozzle-hole diameter is decreased, is due to a small decrease in combustion pressure resulting from a decrease in the heat release rate during premixed combustion.
|Number of pages||8|
|Journal||JSME International Journal, Series B: Fluids and Thermal Engineering|
|Publication status||Published - Aug 1996|
All Science Journal Classification (ASJC) codes
- Mechanical Engineering
- Physical and Theoretical Chemistry
- Fluid Flow and Transfer Processes