Simultaneous Reductions in Diesel NOx and Smoke Emissions with Metallic Water Solution Directly Injected into the Combustion Chamber.

Abstract

The effects of several metallic salt water solutions on NOx and smoke reductions in a divided-chamber diesel engine were examined. The solutions were directly injected into the divided chamber independent of the fuel injection. Significant reductions in NOx and smoke were simultaneously achieved with alkali metallic solutions, especially with sodium salt solution. The optimum solution injection timing in terms of NOx and smoke reductions was just prior to the fuel injection. The NOx and smoke decreased with increasing amount of sodium salt solution, but excessive amounts of the solution resulted in saturation in the reductions of both emissions and the deposition of sodium compounds on the combustion chamber wall. The sodium salt solution reduced dry soot significantly, while total particulate matter increased with increase in the water-soluble fraction mainly composed of the sodium sulfate. The in-chamber gas sampling showed that NOx in the chamber was more reduced with sodium salt solution than with water, especially in later stages of combustion.