Abstract
To further understand the characteristics of smokeless low temperature diesel combustion, the effect of fuel cetane number on mixture formation and combustion characteristics of a single cylinder DI diesel engine was investigated using the engine experiments and CFD code. The results show that besides combustion temperature, fuel-air mixing is also vital to efficient smokeless and low NOx diesel combustion. Smokeless low NOx diesel combustion can be realized even with insufficient fuel-air mixing as long as the combustion temperature is sufficiently low. However lower temperature combustion causes very high THC and CO emissions, and severe deterioration in the combustion efficiency. When the ignition occurs later than about 4 °CA after the end of fuel injection, there is smokeless combustion regardless of fuel cetane number and injection timing and NOx is suppressed to near zero levels by large quantities of cooled EGR. Finally, the operating range of smokeless and ultra-low NOx diesel combustion with low compression ratio and low cetane number fuels are discussed.
