Effect of Injection Pressure and Engine Speed on Air/Fuel Mixing and Emissions in a Pre-Mixed Compression Ignited (PCI) Engine Using Diesel Fuel

PCI combustion of diesel fuel was accomplished in a direct-injected heavy-duty single-cylinder research engine. An impinging spray nozzle combined with a shallow bowl piston design offered a short air/fuel mixing time. Low HC and CO emissions were observed compared to fully premixed operation using n-heptane. A method for evaluating the air/fuel mixing process has been established by quantifying the in-cylinder air/fuel heterogeneity with the NOx emission. The results indicate that high injection pressure and engine speed are favorable for a fast mixing process. The injection pressure had a small impact on HC and CO emissions, while the engine speed had a larger impact. There were no correlation between air/fuel mixing time and HC and CO emissions.