Multi-injection investigation of a high-volatility diesel in advanced compression ignition combustion for NO x control.

Traditional selective catalytic reduction aftertreatment technologies used to reduce N O x are very limited at exhaust temperatures below 175 ° C. Therefore, under these low engine load conditions, having effective in-cylinder control of N O x emissions is important. Previous work by the authors explored the effect of fuel physical properties on the ability to control N O x in-cylinder. That work was limited to one direct injection near top dead center. Modern diesel high-pressure fuel systems have the capability of five or more injections in one engine cycle. A higher-volatility diesel fuel and high amounts of exhaust gas recirculation to delay ignition could provide an opportunity for reduction in engine-out N O x through an increased level of fuel premixing. By appropriately timing multiple short injections, a more optimal distribution of fuel in-cylinder may be achieved, which could reduce N O x while maintaining an efficient combustion phasing. A computational fluid dynamics model previously validated against experimental data was used to explore several injection strategies with increased levels of fuel premixing to assess the potential trade-offs between N O x and CO/unburned hydrocarbon (UHC) emissions and thus reduce reliance on the aftertreatment system for N O x control. The results show that the devised injection strategies resulted in an increased level of fuel premixing. However, none of the attempted injection strategies resulted in significant N O x reductions, and all strategies showed a significant increase in CO and UHC emissions. [ABSTRACT FROM AUTHOR]