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High Efficiency Clean Combustion (HECC) strategies such as homogenous charge compression ignition (HCCI) and pre-mixed charge compression ignition (PCCI) offer much promise for the reduction of NOx and PM from diesel engines. While delivering low PM and low NOx, these combustion modes often produce much higher levels of CO and HC than conventional diesel combustion modes. In addition, partially oxygenated species such as formaldehyde (an MSAT) and other aldehydes increase with HECC modes. The higher levels of CO and HCs have the potential to compromise the performance of the catalytic aftertreatment, specifically at low load operating points. As HECC strategies become incorporated into vehicle calibrations, manufacturers need to avoid producing MSATs in higher quantities than found in conventional combustion modes. This paper describes research on two different HECC strategies, HCCI and PCCI.

Advanced combustion regimes such as homogeneous charge compression ignition (HCCI) and premixed charge compression ignition (PCCI) offer benefits of reduced nitrogen oxides (NOX) and particulate matter (PM) emissions. However, these combustion strategies often generate higher carbon monoxide (CO) and hydrocarbon (HC) emissions. In addition, aldehydes and ketone emissions can increase in these modes. In this study, the engine-out emissions of a compression-ignition engine operating in a fuel reactivity-controlled PCCI combustion mode using in-cylinder blending of gasoline and diesel fuel have been characterized. The work was performed on a 1.9-liter, 4-cylinder diesel engine outfitted with a port fuel injection system to deliver gasoline to the engine. The engine was operated at 2300 rpm and 4.2 bar brake mean effective pressure (BMEP) with the ratio of gasoline-to-diesel fuel that gave the highest engine efficiency and lowest emissions.

Reactivity Controlled Compression Ignition (RCCI) has demonstrated diesel-like or better brake thermal efficiency with significant reductions in nitrogen oxide (NOX) and particulate matter (PM) emissions. Hydrocarbon (HC) and carbon monoxide (CO) emission levels, on the other hand, are higher and similar to those of port-fuel-injected (PFI) gasoline engines. The higher HC and CO emissions combined with the lower exhaust temperatures during RCCI operation present a challenge for current exhaust aftertreatment technologies. The reduction of HC and CO emissions in a lean environment is typically achieved with an oxidation catalyst. In this work, several diesel oxidation catalysts (DOC) with different precious metal loadings were evaluated for effectiveness to control HC and CO emissions from RCCI combustion in a light-duty multi-cylinder engine operating on gasoline and diesel fuels.

Accurate knowledge of diesel particulate filter (DPF) particulate matter (PM) loading is critical for robust and efficient operation of the combined engine-exhaust aftertreatment system. Furthermore, upcoming on-board diagnostics regulations require on-board technologies to evaluate the status of the DPF. This work describes the application of radio frequency (RF) - based sensing techniques to accurately measure DPF particulate matter levels. A 1.9L GM turbo diesel engine and a DPF with an RF-sensor were studied. Direct comparisons between the RF measurement and conventional pressure-based methods were made. Further analysis of the particulate matter loading rates was obtained with a mass-based total PM emission measurement instrument (TEOM) and DPF gravimetric measurements.

New regulations requiring increases in vehicle fuel economy are challenging automotive manufacturers to identify fuel-efficient engines for future vehicles. Lean gasoline direct injection (GDI) engines offer significant increases in fuel efficiency over the more common stoichiometric GDI engines already in the marketplace. However, particulate matter (PM) emissions from lean GDI engines, particularly during stratified combustion modes, are problematic for lean GDI technology to meet U.S. Environmental Protection Agency Tier 3 and other future emission regulations. As such, the control of lean GDI PM with wall-flow filters, referred to as gasoline particulate filter (GPF) technology, is of interest. Since lean GDI PM chemistry and morphology differ from diesel PM (where more filtration experience exists), the functionality of GPFs needs to be studied to determine the operating conditions suitable for efficient PM removal.

Advanced diesel combustion regimes such as High Efficiency Clean Combustion (HECC) offer the benefits of reduced engine out NOx and particulate matter (PM) emissions. Lower PM emissions during advanced combustion reduce the demand on diesel particulate filters (DPFs) and can, thereby, reduce the fuel penalty associated with DPF regeneration. In this study, a SiC DPF was loaded and regenerated on a 1.7-liter 4-cylinder diesel engine operated in conventional and advanced combustion modes at different speed and load conditions. A diesel oxidation catalyst (DOC) and a lean NOx trap (LNT) were also installed in the exhaust stream. Five steady-state speed and load conditions were weighted to estimate Federal Test Procedure (FTP) fuel efficiency. The DPF was loaded using lean-rich cycling with frequencies that resulted in similar levels of NOx emissions downstream of the LNT.

This paper demonstrates the potential for fast absorption spectroscopy measurements in diesel-engine exhaust to track H2O concentration transients. Wavelength-agile absorption spectroscopy is an optical technique that measures broadband absorption spectra between 10 kHz and 100 MHz. From these measured spectra, gas temperature and absorber concentrations can be determined. We introduce a laser spectroscopy system for high speed (10 μs) diesel exhaust measurements in the presence of significant particulate matter. The sensor can be broadly applicable for understanding the dynamics of EGR distribution, cycle-to-cycle stability, cylinder-to-cylinder charge uniformity, and NOX regeneration strategies. The method precision is 10% and 5%, for individual 10-μs measurements and 2-ms averaged measurements, respectively. The sensitivity or detection limit of the measurement is 0.5% H2O.