An investigation was performed on a direct injection diesel engine equipped with a gaseous injector to determine the effects of augmented mixing on emission characteristics. The gaseous injector introduced a jet of gas of particular composition in the cylinder during the latter portion of diesel combustion. This injector was controlled to inject the gas at specific engine timings and at various injection pressures.
Engine experiments were done on a LABECO/TACOM single cylinder, direct injected, 1.2 liter, four stroke diesel engine. This engine was operated at 1500 rpm at an equivalence ratio of 0.5 with simulated turbocharging. The fuel injection timing was changed for some cases to accommodate the gaseous injection.
Exhaust particulate emissions were measured with a mini-dilution tunnel. All other emissions data were measured on a REGA 7000 Real-Time Exhaust Gas Analyzer Fourier Transform Infrared (FT-IR) system.
Industrial grade nitrogen was injected at high pressures and at various crank angles to observe the nitrogen's effects on emissions under different operating conditions. For an advanced diesel fuel injection timing, particulate emissions decreased to a minimum then increased as the auxiliary nitrogen injection occurred later in the combustion period. For retarded fuel timing, the effects of gas jets of different nitrogen injection pressures were investigated. Again, a reduction in particulates was observed. Carbon dioxide was injected to investigate the effects of gas composition on soot oxidation. In this study, the carbon dioxide injection was detrimental to soot oxidation.
Additionally, quantitative analyses were performed on the gaseous jet outside of the engine to show the relationship between momentum introduced by the jet and its effect on turbulent mixing and emissions.