抄録
The characteristics of smokeless low temperature diesel combustion with various fuel-air mixing were systematically studied by engine tests with large quantities of cooled EGR and fuels of various cetane numbers, as well as by CFD simulation of the in-cylinder distributions of mixture concentrations and temperatures. The results show that in addition to combustion temperature, fuel-air mixing is also important for efficient, smokeless, and low-NO_x diesel combustion. Smokeless and low-NO_x diesel combustion can be established even with insufficient fuel-air mixing as long as the combustion temperature is sufficiently low, but at the expenses of very high UHC and CO emissions, and severe deterioration in the combustion efficiency. While smoke is influenced by combustion temperature, it depends strongly upon the premixing time from the end of fuel injection to the onset of ignition. When ignition occurs later than about 4℃A after the end of fuel injection at 1320 rpm, there is smokeless combustion regardless of fuel cetane number and fuel injection timing, and NO_x is suppressed to near zero levels by large quantities of cooled EGR.
