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Selective Catalytic Reduction (SCR) catalysts used in Lean NOx Trap (LNT) - SCR exhaust aftertreatment systems typically encounter alternating oxidizing and reducing environments. Reducing conditions occur when diesel fuel is injected upstream of a reformer catalyst, generating high concentrations of hydrogen (H₂), carbon monoxide (CO), and hydrocarbons to deNOx the LNT. In this study, the functionality of an iron (Fe) zeolite SCR catalyst is explored with a bench top reactor during steady-state and cyclic transient SCR operation. Experiments to characterize the effect of an LNT deNOx event on SCR operation show that adding H₂ or CO only slightly changes SCR behavior with the primary contribution being an enhancement of nitrogen dioxide (NO₂) decomposition into nitric oxide (NO). Exposure of the catalyst to C₃H₆ (a surrogate for an actual exhaust HC mixture) leads to a significant decrease in NOx reduction capabilities of the catalyst.

The use of Compressed Natural Gas (CNG) has demonstrated the potential to decrease Particulate Matter (PM) and nitrogen oxide (NOx) emissions simultaneously when used in a dual-fuel application with diesel fuel functioning as the ignition source. However, some authors do find that NOx emissions can increase. One postulation is that the conflicting results in the literature may be due to the difference in composition of natural gas around the world. Therefore, in order to investigate if CNG composition influences combustion performance and emissions, four unique mixtures of CNG were tested (i.e., 87% to 96% methane) while minimizing the combined difference of the density, heating value, and constant pressure specific heat of each mixture. This was accomplished at moderate energy substitution ratios (up to 40%) in a single cylinder engine operating at various loads.

Particulate filters (PF) are a highly effective after-treatment device that reduces particulate matter emissions, a rising environmental concern in the automotive industry. However, accumulation of solid particles during the PF filtration process increases engine backpressure considerably, which can have a negative impact on engine efficiency, acoustics, and gaseous emissions. In this area, an accurate pressure drop model helps to better understand the effect of accumulated solid particles in the PF on engine backpressure, aiding in design and regeneration considerations without physical testing. These effects are further improved on board the vehicle using a single equation pressure drop model with a relatively low computational cost. This article presents a thorough history of PF pressure drop models and their advancements.

Recently, ozone addition has come under scrutiny as a means of controlling ignition timing for Low Temperature (LTC) combustion, which defeats the NOx-PM tradeoff using a highly dilute, homogeneous mixture. This is because ozone decomposes into atomic oxygen and hydroxyl radicals that influence the early phases of the ignition delay process. In order to understand ozone's influence on combustion better, this work analyzes the effects of ozone-assisted combustion for a single-cylinder, direct-injection Compression Ignition engine via a mechanical pump-line-nozzle fuel system and an electronically controlled common-rail fuel injection system. Experimental outcomes indicate a relatively small influence of ozone for the mechanical injection system with a comparably decreased effect for the common rail system.

Software packages including Argonne National Lab's Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model and the EPA's Motor Vehicle Emissions Simulation (MOVES) model are useful in analyzing the emission profiles of light-duty vehicles. In particular, GREET performs a detailed life cycle fuel energy and emissions analysis, while MOVES focuses on energy and emissions during vehicle operation. This study uses MOVES2010b in the creation of emission trends in order to predict future emissions regulations and the subsequent aftertreatment device areas of improvement required to meet these standards. A second objective was to create four time sheet tables in order to update the base vehicle operation emission profiles used in GREET. The simulation results depict the balance between nitrous oxide and hydrocarbon emissions, the dependency upon climate effects, and areas for potential improvement given recent engine design trends.

Utilizing a higher compression ratio in a Compression Ignition (CI) engine grants an obvious advantage of improved thermal efficiency. However, the resulting combustion temperatures promote dissociation ensuing in increased nitrogen oxide (NOx) emissions. Unfortunately, due to the inherent properties of CI combustion, it is difficult to achieve simultaneous reduction of NOx and particulate matter (PM) through conventional combustion methods. Taking a different route though accomplishing Homogeneous Charge Compression Ignition (HCCI) in CI engines will largely eliminate NOx and PM; however, combustion can result in a significant increase in hydrocarbon (HC) and carbon monoxide (CO) emissions due to the low volatility of diesel fuel. Hence, this work attempts another avenue of Low Temperature Combustion (LTC) by employing Pre-mixed Charge Compression Ignition (PCI) combustion on a comparatively higher compression ratio (21.2) single cylinder CI engine.

Biodiesel is a potential alternative to Ultra Low Sulfur Diesel (ULSD); however, it often suffers from increased fuel consumption in comparison to ULSD when injection timings and/or pressures are similar. To decrease fuel consumption, increasing biodiesel injection pressure has been found to mitigate the issues associated with its relatively high viscosity and lower energy content. When doing so, the literature indicates decreased emissions, albeit with potentially greater nitrogen oxide (NOx) emissions in contrast to ULSD. In order to better understand the trade-off between fuel consumption and NOx emissions, this study explores the influence of fuel injection pressure on ULSD, Waste Cooking Oil (WCO) biodiesel, and their blends in a single-cylinder compression ignition (CI) engine. In particular, fuel injection pressures and timings for WCO biodiesel and blended fuels are adjusted to attempt to mimic the in-cylinder pressure profile of operation using ULSD.

A timing sweep to correlate the location of Maximum Brake Torque (MBT) was completed on a single-cylinder, direct injected compression ignition engine that was recently upgraded to a high-pressure rail injection system for better engine control. This sweep included emissions monitoring for carbon dioxide, carbon monoxide, particulate matter, hydrocarbons, and oxides of nitrogen for the calibration of a heat release model, as well as the opportunity to relate MBT timing to brake-specific emissions production. The result of this timing sweep was a relatively linear correlation between injection delay and peak pressure timing. In addition, a number of other MBT timing methodologies were tested indicating their applicability for immediate feedback upon engine testing, particularly mass fraction burned correlations. Emissions were either strongly correlated to MBT timing (with emissions being minimized in the vicinity of MBT), or were completely independent of MBT.

Diesel Particulate Filters (DPFs) have become a required aftertreatment device for Compression Ignition engine exhaust cleanup of Particulate Matter (PM). Moreover, with the increased prevalence of Spark Ignition Direct Injection (SIDI) systems, discussions are currently underway regarding the need of Gasoline Particulate Filters to handle the PM emanating from their combustion process. In this area, the two-channel DPF model has been widely successful in predicting the temperature, pressure drop, and species conversion in these devices. Because of the need to simulate compressible flow through the channels and a porous wall, these models have a difficult time achieving real-time predictive results suitable for an Engine Control Unit (ECU). As a result, this effort describes the creation of a lumped DPF model intended for an ECU. Model formulation was based on the standard governing equations, but simplified in order to remove as much computational overhead as possible.

The growing presence of Spark Ignition Direct Injection (SIDI) engines along with the prevalence of direct injected Compression Ignition (CI) engines results in the requirement of Particulate Matter (PM) exhaust abatement. This occurs through the implementation of Gasoline Particulate Filters (GPFs) and Diesel Particulate Filters (DPFs). Modeling of GPFs and DPFs are analogous because of the similar flow patterns and wall flow PM capture methodology. Conventional modeling techniques include a two-channel (inlet/outlet) formulation that is applicable up to three-dimensions. However, the numerical stiffness that results from the need to couple the solution of these channels in compressible flow can result in relatively long run times. Previously, the author presented a lumped DPF model using dynamically incompressible flow intended for an Engine Control Unit (ECU) in order to generate a model that runs faster than real time using a high-level programming language.

Significant progress towards reducing diesel engine fuel consumption and emissions is possible through the simultaneous Waste Heat Recovery (WHR) and Particulate Matter (PM) filtration in a novel device described here as a Diesel Particulate Filter Heat Exchanger (DPFHX). This original device concept is based on the shell-and-tube heat exchanger geometry, where enlarged tubes contain DPF cores, allowing waste heat recovery from engine exhaust and allowing further energy capture from the exothermic PM regeneration event. The heat transferred to the working fluid on the shell side of the DPFHX becomes available for use in a secondary power cycle, which is an increasingly attractive method of boosting powertrain efficiency due to fuel savings of around 10 to 15%. Moreover, these fuel savings are proportional to the associated emissions reduction after a short warm-up period, with startup emissions relatively unchanged when implementing a WHR system.

In this paper, the available correlations proposed in the literature for the gas-side heat transfer in the intake and exhaust system of a spark-ignition internal combustion engine were surveyed. It was noticed that these only by empirically fitted constants. This similarity provided the impetus for the authors to explore if a universal correlation could be developed. Based on a scaling approach using microscales of turbulence, the authors have fixed the exponential factor on the Reynolds number and thus reduced the number of adjustable coefficients to just one; the latter can be determined from a least squares curve-fit of available experimental data. Using intake and exhaust side data, it was shown that the universal correlation The correlation coefficient of this proposed heat transfer model with all available experimental data is 0.845 for the intake side and 0.800 for the exhaust side.