Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4990518 | Applied Thermal Engineering | 2017 | 12 Pages |
Abstract
Nitrogen oxides (NOx) and soot emissions are the most important pollutants from direct-injection diesel engines. In particular, soot formation and oxidation determine the net engine-out soot emissions. These phenomena are complex and competing processes during diesel combustion. Despite many researches implicate the mechanisms of soot formation with soot emissions, the enhancement of the late cycle soot oxidation is the dominant mechanism for a reduction of engine-out soot emissions. The mixing process and the in-cylinder bulk temperature are two important parameters in the development of soot oxidation process. The current research compares different engine strategies to enhance the late cycle mixing controlled combustion process and therefore enhance soot oxidation while maintaining similar gross indicated efficiency in a light-duty engine. For this purpose, a simplified methodology has been used, which analyzes the effect of mixing process and in-cylinder bulk gas temperature on soot oxidation during the late cycle combustion. For carrying out this research, theoretical and experimental tools were used. In particular, the experimental measurements were made in a single-cylinder direct-injection light-duty diesel engine varying the swirl ratio and the injection pattern as injection pressure, Start of Energizing (SoE), Energizing Time (ET) and number of injections events. To analyze soot emissions, the combustion luminosity was measured by an optoelectronic probe and the optical thickness parameter (KL) was evaluated by the two-color pyrometry method. The apparent combustion time (ACT-1) was used as mixing time tracer. Results show that an increase in swirl ratio implies an improvement on the mixing process and higher values of average bulk temperature during the late-cycle diffusion combustion. Both phenomena produce an enhancement in the soot oxidation process. In the lowest swirl ratio case, a suitable injection strategy based on multiple injections, provides similar results of soot oxidation process (and therefore, the emissions) as high swirl ratio case.
Keywords
Intake temperatureGIEEOCPOIIVCgross indicated efficiencyFSNEOIFWHMACTPOCCA50SOEEGRTDCGHGBMEPNOxEvoNitrogen oxidestinbrake mean effective pressureDirect-injectionAbsorptivitycrank angle degreeexhaust valve openparticulate matterRoHRcrank angle at 50% mass fraction burnedspectral intensityFilter Smoke NumberOptical thicknessCADLift-off lengthWavelengthIntake pressureEmissivityLOLtop dead centerInternal combustion enginesRate of heat releaseSwirl ratioend of combustionEnd Of InjectionPINGreenhouse gasesIce
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Fluid Flow and Transfer Processes
Authors
Jesús Benajes, Jaime MartÃn, Antonio GarcÃa, David Villalta, Alok Warey,