Effects of Alternative Fuels and Intake Port Geometry on HSDI Diesel Engine Performance and Emissions

This research explored methods to reduce regulated emissions in a small-bore, direct-injection diesel engine. Swirl was used to influence mixing of the spray plumes, and alternative fuels were used to study the effects of oxygenated and water microemulsion diesel fuels on emissions. Air/fuel mixing enhancement was achieved in the running engine by blocking off a percentage of one of the two intake ports. The swirl was characterized at steady-state conditions with a flowbench and swirl meter. Swirl ratios of 1.85, 2.70, and 3.29 were studied in the engine tests at full load with engine speeds of 1303, 1757, and 1906 rev/min. Increased swirl was shown to have negative effects on emissions due to plume-to-plume interactions.

Blends of No. 2 diesel and biodiesel were used to investigate the presence of oxygen in the fuel and its effects on regulated emissions. Pure No. 2 diesel fuel, a 15% and a 30% biodiesel blend (by weight) were used. The effects were investigated at full load with engine speeds of 1303 and 1757 rev/min and a swirl ratio of 1.85. The results showed that the particulate emissions were reduced significantly with the use of oxygen in the fuel. A study was also performed using a water-diesel microemulsion fuel to assess the potential for additional NOx reduction of advanced fuels compared to a California Reference diesel fuel. The microemulsion contained 10% by volume, 20-30 nm diameter water droplets, and was run at part and full loads at 1757 rev/min. The results overall showed great reductions in regulated emissions, indicating that this new fuel concept holds significant promise for future applications.