Search Results

Transient exhaust emissions data were collected with a 4.9-L, V6 prototype diesel engine operated on an engine dynamometer using repetitive Highway Fuel Economy Tests (Hwy-FET). This procedure provided sufficient exhaust temperatures during transient operation to characterize the performance of an exhaust treatment system consisting of a diesel oxidation catalyst (DOC) followed by a hydrocarbon selective catalytic reduction (HC-SCR) system for NOx control under conditions typical of “real world”. The goal was to provide data needed for modeling the problem of hydrocarbon deactivation. Repetitive Hwy-FETs highlighted the effects of hydrocarbon deactivation over time. Stochastic Process Modeling showed that the observed catalyst deactivation was due mainly to a change in the reactivity of the catalyst and not to a change in the catalyst inlet conditions.

As part of a cooperative development program, six diesel fuels (a reference and five blends containing oxygenates) were evaluated under four steady-state conditions using a prototype 1.26-L 3-cylinder four-valve common-rail DI diesel engine. All of the fuels contained low sulfur (mostly < 5 ppm by mass), and they were chosen to determine the impacts of oxygenate volatility, concentration, and chemical type (paraffinic or aromatic) on exhaust emissions - with particular emphasis on particulate emissions. In addition to HC, CO, NOx and PM emissions measurements, emissions of the volatile portion of the PM and particle size were determined. Relative to the very low sulfur reference fuel, the oxygenated fuels reduced PM and NOx under some operating conditions, but produced little effect on either HC or CO emissions. Aliphatic oxygenates at 6 wt. percent oxygen in the reference fuel reduced simulated FTP PM emissions by 15 - 27 %.

The control of NOx emissions is the greatest technical challenge in meeting future emission regulations for diesel engines. In this work, a modal analysis was performed for developing an engine control strategy to take advantage of fuel properties to minimize engine-out NOx emissions. This work focused on the use of EGR to reduce NOx while counteracting anticipated PM increases by using oxygenated fuels. A DaimlerChrysler OM611 CIDI engine for light-duty vehicles was controlled with a SwRI Rapid Prototyping Electronic Control System. Engine mapping consisted of sweeping parameters of greatest NOx impact, starting with OEM injection timing (including pilot injection) and EGR. The engine control strategy consisted of increased EGR and simultaneous modulation of both main and pilot injection timing to minimize NOx and PM emission indexes with constraints based on the impact of the modulation on BSFC, Smoke, Boost and BSHC.

In the twenty-first century, exhaust emission control will remain a major technical challenge especially as additional pressures for fuel and energy conservation mount. To address these needs, a wide variety of engine and powertrain options must be considered. For many reasons, the piston engine will remain the predominant engine choice in the twenty-first century, especially for conventional and/or parallel hybrid drive trains. Emissions constraints favor the conventional port fuel-injected gasoline engine with 3-way exhaust catalyst, while energy conservation favors direct-injection gasoline and diesel engines. As a result of recent technological progress from a competitive European market, diesels, and most recently, direct-injection (DI) diesels now offer driveability and performance characteristics competitive with those of gasoline engines. In addition, DI diesels offer the highest fuel efficiency.

Previously we reported (SAE Paper 2005-01-0475) that emissions of toxicologically relevant compounds from an engine operating at low NOx conditions using Fischer-Tropsch fuel (FT100) were lower than those emissions from the engine using an ultra-low sulfur (15 PPM sulfur) diesel fuel (BP15). Those tests were performed at two operating modes: Mode 6 (4.2 bar BMEP, 2300 RPM) and Mode 11 (2.62 bar BMEP, 1500 RPM). We wanted to evaluate the effect on emissions of operating the engine at low power (near idle) in conjunction with the low NOx strategy. Specifically, we report on emissions of total hydrocarbon (HC), carbon monoxide (CO), NOx, particulates (PM), formaldehyde, acetaldehyde, benzene, 1,3-butadiene, gas phase polyaromatic hydrocarbons (PAH's) and particle phase PAH's from a DaimlerChrysler OM611 CIDI engine using a low NOx engine operating strategy at Mode 22 (1.0 bar BMEP and 1500 RPM).

A 1.3-L direct injection diesel engine was used in steady-state testing to determine the emissions performance of a matrix of ultra-low sulfur diesel fuels encompassing two types of sulfur removal and the use of fuel oxygenates. As expected, exhaust gas recirculation was the most effective technique for NOx reduction. With regard to fuel effects, an oxygenated diesel fuel produced with a conventional sulfur removal process reduced particulate emissions substantially, and these particulate reductions could be converted into NOx reductions by using higher levels of exhaust gas recirculation. On a simulated FTP, this oxygenated fuel simultaneously decreased NOx emissions by 30% and total particulate emissions by 50% compared to a baseline fuel.

A previous paper reported (SAE Paper 2002-01-2884) that it was possible to decrease mode-weighted NOx emissions compared to the OEM calibration with corresponding increases in particulate matter (PM) emissions. These PM emission increases were partially overcome with the use of oxygenated diesel fuel additives. We wanted to know if compounds of toxicological concern were emitted more or less using oxygenated diesel fuel additives that were used in conjunction with a modified engine operating strategy to lower engine-out NOx emissions. Emissions of toxicologically relevant compounds from fuels containing triproplyene glycol monomethyl ether and dibutyl maleate were the same or lower compared to a low sulfur fuel (15 ppm sulfur) even under engine operating conditions designed to lower engine-out NOx emissions.

A radioactive tracer technique was developed to determine the contribution of oil from an engine sump to exhaust particulate matter collected on a filter. The technique was applied to particulate emissions produced by an automotive diesel engine which was operated on an engine dynamometer over a range of steady-state conditions. The results indicated that from 1.5 to 25 mass percent of the particulate matter, depending on speed and load, consisted of material from the engine oil. The oil contribution to the extractable organic portion of the particulate matter ranged between 16 and 80 percent.

An apparatus was developed for the determination of the engine oil contribution to both total and extractable particulate exhaust emissions from diesel-powered vehicles during cyclic operation on a chassis dynamometer. For the five vehicles tested, the percentage of the total particulate material that was derived from engine oil ranged from 7 to 14%. Between 14 and 26% of the total particulate material was extractable with benzene-ethanol (80-20) solvent. Oil contributed from 30 to 55% of the extractables in most cases. Engine design and oil formulation generally appeared to have only small effects on the oil contribution to the particulate emissions. A 1982 model-year vehicle with a 1.8L engine was an exception, since its oil contribution to the total and especially to the extractable particulate emissions (14 and 95%, respectively) was significantly greater than for any of the other vehicles.

Exhaust emission and performance characteristics of a single-cylinder engine fueled with methanol are compared to those obtained either with gasoline or a methanol-water blend. Our measurements of engine efficiency and power, and CO and NOx emissions agree with trends established in the literature. Consequently, the emphasis is placed on organic emissions (unburned fuel including hydrocarbons, and aldehydes), an area in which there is no consensus in the literature. In all cases with methanol fueling, the unburned fuel (UBF) emissions were virtually all methanol as opposed to hydrocarbon compounds. Without special measures to overcome methanol's large heat of vaporization, UBF emissions were four times greater with methanol than those with gasoline. Similarly, aldehyde emissions were an order of magnitude greater with methanol.

A study was undertaken to determine the combined effect of methylcyclopentadienyl manganese tricarbonyl (MMT) fuel additive and exhaust gas recirculation (EGR) on particulate and oxides of nitrogen (NOx) emissions from a single-cylinder light-duty diesel engine. Further, the physical and chemical properties of the particulate material were determined to better understand MMT and EGR effects on these emissions. The results showed that EGR always decreased NOx emissions, and that MMT had no significant effect on them. In addition, EGR always increased particulate emissions, but MMT was effective in limiting this increase especially at high EGR levels.

The dioiefin content of unstable gasolines has been implicated in the restriction of multi-port fuel injectors by deposits. Vehicle tests of the effect of adding a diolefin mixture to a stable (olefinic) gasoline indicated that a deposit-producing gasoline resulted. Laboratory oxidation tests showed that addition of a “dienophile” to an unstable gasoline significantly reduced deposit formation, increased oxidation stability, and reduced gum formation. Additional vehicle tests with a dienophile-treated fuel showed that some injector deposits were reduced, but new deposits occurred in other areas of the fuel system. Apparently, diolefins can be a factor in producing plugged fuel injectors, but other fuel factors are also likely to play important roles whether diolefins are present or not.