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Exhaust temperature models are widely used in the automotive industry to estimate catalyst and exhaust gas temperatures and to protect the catalyst and other vehicle hardware against over-temperature conditions. Modeled exhaust temperatures rely on air, fuel, and spark measurements to make their estimate. Errors in any of these measurements can have a large impact on the accuracy of the model. Furthermore, air-fuel imbalances, air leaks, engine coolant temperature (ECT) or air charge temperature (ACT) inaccuracies, or any unforeseen source of heat entering the exhaust may have a large impact on the accuracy of the modeled estimate. Modern universal exhaust gas oxygen (UEGO) sensors have heaters with controllers to precisely regulate the oxygen sensing element temperature. These controllers are duty cycle based and supply more or less current to the heating element depending on the temperature of the surrounding exhaust gas.

During the course of emissions and fuel economy (FE) testing, vehicles that are calibrated to meet Tier 3 emissions requirements currently must demonstrate compliance on Tier 3 E10 fuel while maintaining emissions capability with Tier 2 E0 fuel used for FE label determination. Tier 3 emissions regulations prescribe lower sulfur E10 gasoline blends for the U.S. market. Tier 3 emissions test fuels specified by EPA are required to contain 9.54 volume % ethanol and 8-11 ppm sulfur content. EPA Tier 2 E0 test fuel has no ethanol and has nominal 30 ppm sulfur content. Under Tier 3 rules, Tier 2 E0 test fuel is still used to determine FE. Tier 3 calibrations can have difficulty meeting low Tier 3 emissions targets while testing with Tier 2 E0 fuel. Research has revealed that the primary cause of the high emissions is deactivation of the aftertreatment system due to sulfur accumulation on the catalysts.

A three-way catalytic converter (TWC) is an emissions control device, used to treat the exhaust gases in a gasoline engine. The conversion efficiency of the catalyst, however, drops with age or customer usage and needs to be monitored on-line to meet the on board diagnostics (OBD II) regulations. In this work, a non-intrusive catalyst monitor is developed to diagnose the track the remaining useful life of the catalyst based on measured in-vehicle signals. Using air mass and the air-fuel ratio (A/F) at the front (upstream) and rear (downstream) of the catalyst, the catalyst oxygen storage capacity is estimated. The catalyst capacity and operating exhaust temperature are used as an input features for developing a Support Vector Machine (SVM) algorithm based classifier to identify a threshold catalyst. In addition, the distance of the data points in hyperspace from the calibrated threshold plane is used to compute the remaining useful life left.

We have developed a revolutionary automotive catalyst that maintains high activity by the suppression of grain growth of precious metals. This catalyst contains Pd-perovskite crystal which has shown a capacity for self-regeneration of Pd in a cycle of solid solution and segregation in perovskite crystals [1, 2, 3, 4, 5 and 6]. We named this catalyst the “Intelligent Catalyst” and first commercialized it in the Japanese market in October 2002 [7, 8]. In this study, we investigated the activity of Pd at various temperatures to confirm that the self-regenerative mechanism worked well at low temperatures like those right after engine starting. We also examined the durability of perovskite structure at high temperatures and tested its catalytic activity after engine aging at high temperatures above 1000 °C up to 1100 °C. It is proved that the intelligent catalyst has both excellent activity and durability under practical conditions.

The use of urea-based selective catalytic reduction (SCR) is a promising method for achieving U.S. Tier 2 diesel emission standards for NOx. To meet the Tier 2 standards for Particulate Matter (PM), a catalyzed diesel particulate filter (CDPF) will likely be present and any ammonia (NH3) that is not consumed over an SCR catalyst would pass over the CDPF to make nitrous oxide (N2O) emissions and/or oxides of nitrogen (NOx), or exit the exhaust system as NH3. N2O is undesirable due to its high greenhouse gas potential, while NOx production from the slipped NH3 would reduce overall system NOx conversion efficiency. This paper reviews certain conditions where NH3 slip past an SCR system may be a concern, looks at what would happen to this slipped NH3 over a CDPF, and evaluates the performance of various supplier NH3 slip catalysts under varied space velocities, temperatures and concentrations of NH3 and NOx.

A laboratory aging study was performed on samples of a lean NOx trap with platinum group metal (PGM) loadings of 0.53, 1.06, 2.12, and 3.18 g/liter. The LNT samples were aged at inlet temperatures of 650°C, 750°C, 800°C, and 850°C behind samples of a three-way catalyst that were aged on a pulse-flame combustion reactor with a Ford-proprietary durability schedule representing 80,000 km of customer use. For all aging temperatures, higher PGM loadings were beneficial for low temperature NOx performance, attributable to an increase in the oxidation of NO to NO2. Conversely, lower PGM loadings were beneficial for high temperature NOx performance after aging at 650°C and 750°C, as higher loadings promoted the decomposition of the nitrates during lean operation and thereby decreased the NOx storage capability at high temperatures. Also, higher PGM loadings increased the OSC of the trap and thereby increased the purge requirements.

Selective Catalytic Reduction of NOx is a promising technology to enable diesel engines to meet certification under Tier 2 Bin 5 emissions requirements. SCR catalysts for vehicle use are typically zeolitic materials known to store both hydrocarbons and ammonia. Ammonia storage on the zeolite has a beneficial effect on NOx conversion; hydrocarbons however, compete with ammonia for storage sites and may also block access to the interior of the zeolites where the bulk of the catalytic processes take place. This paper presents the results of laboratory studies utilizing surrogate hydrocarbon species to simulate engine-out exhaust over catalysts formulated to operate in both low (≈175-500°C) and high temperature (≈250-600°C) regimes. The effects of hydrocarbon exposure of these individual species on the SCR reaction are examined and observations are made as to necessary conditions for the recovery of SCR activity.

Using local emissions measurements immediately downstream of a close-coupled catalyst, spatial variations in emissions have been analysed for close-coupled catalysts with different ageing histories. Comparison of the radial emissions profiles between a uniformly-aged (oven-aged) catalyst and two vehicle-aged parts suggests that the vehicle-aged parts have substantial variations in catalyst damage across the radius of the catalyst. The radial variations in damage were confirmed by bench reactor and post-mortem studies. The radial catalyst damage profiles inferred from engine-based evaluations of vehicle aged catalysts show broad correlation with high flow areas identified by CFD predictions and high temperature regions as measured during engine tests.

It is anticipated that future gasoline engines will have improved mechanical efficiency and consequently lower exhaust temperatures at low load conditions, although the exhaust temperatures at high load conditions are expected to remain the same or even increase due to the increasing use of downsized turbocharged engines. In 2014, a collaborative project was initiated at Ford Motor Company, Oak Ridge National Lab, and the University of Michigan to develop three-way catalysts with improved performance at low temperatures while maintaining the durability of current TWCs. This project is funded by the U.S. Department of Energy and is intended to show progress toward the USDRIVE target of 90% conversion of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) at 150 °C after high mileage aging. The testing protocols specified by the USDRIVE ACEC team for stoichiometric S-GDI engines were utilized during the evaluation of experimental catalysts at all three facilities.

In anticipation that future gasoline engines will have improved fuel efficiency and therefore lower exhaust temperatures during low load operation, a project was initiated in 2014 to develop three-way catalysts (TWC) with improved activity at lower temperatures while maintaining the durability of current TWCs. This project is a collaboration between Ford Motor Company, Oak Ridge National Laboratory, and the University of Michigan and is funded by the U.S. Department of Energy. The ultimate goal is to show progress towards the USDRIVE goal of 90% conversion of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) at 150°C after high mileage aging. A reactor was set up at Ford to follow the catalyst testing protocols established by the USDRIVE ACEC tech team for evaluating catalysts for stoichiometric gasoline direct-injection (S-GDI) engines; this protocol specifies a stoichiometric blend of CO/H2, NO, C3H6, C2H4, C3H8, O2, H2O, and CO2 for the evaluations.

A laboratory study was performed to assess the potential capability of TWC+LNT/SCR systems to satisfy the Tier 2, Bin 2 emission standards for lean-burn gasoline applications. It was assumed that the exhaust system would need a close-coupled (CC) TWC, an underbody (U/B) TWC, and a third U/B LNT/SCR converter to satisfy the emission standards on the FTP and US06 tests while allowing lean operation for improved fuel economy during select driving conditions. Target levels for HC, CO, and NOx during lean/rich cycling were established. Sizing studies were performed to determine the minimum LNT/SCR volume needed to satisfy the NOx target. The ability of the TWC to oxidize the HC during rich operation through steam reforming was crucial for satisfying the HC target.

Polymer electrolyte membrane fuel cell (PEFC) systems for fuel cell vehicles (FCVs) require both performance and durability. Carbon is the typical support material used for PEFC catalysts. However, hydrogen starvation at the anode causes high electrode potential states (e.g., 1.3 V with respect to the reversible hydrogen electrode) that result in severe carbon support corrosion. Serious damage to the carbon support due to hydrogen starvation can lead to irreversible performance loss in PEFC systems. To avoid such high electrode potentials, FCV PEFC systems often utilize cell voltage monitor systems (CVMs) that are expensive to use and install. Simplifying PEFC systems by removing these CVMs would help reduce costs, which is a vital part of popularizing FCVs. However, one precondition for removing CVMs is the adoption of a durable support material to replace carbon.

Three-way catalyst shows high performance under stoichiometric atmosphere. The CeO2-ZrO2 based materials (CZ) are added as a buffer of O2 concentration. To improve the catalyst performance the larger O2 storage capacity (OSC) are needed. Theoretically, the sulfur oxidation-reduction reaction moves oxygen 8 times larger than cerium. We focused on this phenomenon and synthesized Ln2O2SO4 as a new OSC material. The experimental result under model gas shows that the OSC of Ln2O2SO4 is 5 times lager than CZ.

Performance improvements were studied for the diesel particulate and NOx reduction system (DPNR), a system that simultaneously reduces NOx and Particulate Matter (PM) from diesel engine exhaust gas. The experimental system (hereinafter called the “dual DPNR”) consists of two DPNR catalysts arranged in parallel, each provided with an exhaust throttle valve downstream to control the exhaust gas flow to the catalyst, plus a fuel injector that precisely controls the air-fuel ratio and the catalyst bed temperature. The fuel injector is used to supply a rich mixture to the DPNR catalyst, and the flow of exhaust gas is switched between the two catalysts by operating the exhaust throttle valves alternately. Tests were conducted with the engine running at steady state. The results indicated that the NOx reduction performance dramatically improved and the loss of fuel economy from the NOx reduction reduced.

The development of an alternative oxygen reduction electrocatalyst to platinum based electrocatalysts is critical for practical use of the polymer electrolyte membrane fuel cell (PEMFC). Transition metal sulfide chalcogenides have recently been reported as a possible candidate for Pt replacement. Our work focused on chalcogenides composed of ruthenium, molybdenum, and sulfur (RuMoS). We elucidate the factors affecting electrocatalytic activity of carbon supported RuXMoY SZ catalyst. This was demonstrated through a correlation of oxygen reduction reaction (ORR) activity of the catalysts with structural changes resulting from designed changes in sulfur composition in the catalysts.

A new after-treatment system called DPNR (Diesel Particulate-NOx Reduction System) has been developed for simultaneous and continuous reduction of particulate matter (PM) and nitrogen oxides (NOx) in diesel exhaust gas. This system consists of both a new catalytic technology and a new diesel combustion technology which enables rich operating conditions in diesel engines. The catalytic converter for the DPNR has a newly developed porous ceramic structure coated with a NOx storage reduction catalyst. A fresh DPNR catalyst reduced more than 80 % of both PM and NOx. This paper describes the concept and performance of the system in detail. Especially, the details of the PM oxidation mechanism in DPNR are described.

A laboratory study was performed to assess the potential of using selective catalytic reduction (SCR) with NH3 to treat the NOx emissions from lean-burn gasoline engines. A primary concern was the potential for hot rich exhaust conditions on the vehicle, as such conditions could degrade the zeolite-based SCR catalysts being developed for automotive applications. Samples of an iron/zeolite formulation were aged for 34 hours behind samples of a three-way catalyst (TWC) on a pulse-flame combustion reactor using different A/F ratio schedules that exposed the catalysts to either continuously lean operation, mostly stoichiometric operation, or mostly rich operation. For each A/F ratio schedule, separate SCR samples were aged with inlet temperatures of 750°C, 800°C, or 850°C. The aged SCR samples were evaluated for NOx conversion at 25K hr-1 during lean temperature ramps with 500 ppm NO and NH3.

Over the past decade urea-based selective catalytic reduction (SCR) has become a leading aftertreatment solution to meet increasingly stringent Nitrogen oxide (NOx) emissions requirements in diesel powertrains. A common trend seen in modern SCR systems is the use of "split-brick" configurations where two SCR catalysts are placed in thermally distinct regions of the aftertreatment. One catalyst is close-coupled to the engine for fast light-off and another catalyst is positioned under-floor to improve performance at high space velocities. Typically, a single injector is located upstream of the first catalyst to provide the reductant necessary for efficient NOx reduction. This paper explores the potential benefit, in terms of improved NOx reduction, control of NH3 slip or reduced reductant consumption, of having independently actuated injectors in front of each catalyst.

In recent years, the EPA has implemented a requirement for monitoring the air fuel ratio balance in multi-cylinder engines such that those imbalances may not be so great as to cause the tailpipe emissions level to exceed 1.5 times the nominal emissions standard. Such imbalances may be the result of production fuel injector variation, contamination, leaks, or other malfunctions which cause the air or fuel rate to vary across the cylinders controlled by a single oxygen sensor. For many diagnostic systems that rely on the signal from the oxygen sensor, to achieve compliance to the new diagnostic standard, the sensor must see the signal from each cylinder equally. The aftertreatment system must also be robust to individual cylinder air fuel ratio variation. This paper introduces the concept of catalyst zone flow, a condition in which different cylinders of a multi-cylinder engine use different portions of the catalyst brick.

The details of Di-Air, a new NOx reduction system using continuous short pulse injections of hydrocarbons (HC) in front of a NOx storage and reduction (NSR) catalyst, have already been reported. This paper describes further studies into the deNOx mechanism, mainly from the standpoint of the contribution of HC and intermediates. In the process of a preliminary survey regarding HC oxidation behavior at the moment of injection, it was found that HC have unique advantages as a reductant. The addition of HC lead to the reduction or metallization of platinum group metals (PGM) while keeping the overall gas atmosphere in a lean state due to adsorbed HC. This causes local O₂ inhibition and generates reductive intermediate species such as R-NCO. Therefore, the specific benefits of HC were analyzed from the viewpoints of 1) the impact on the PGM state, 2) the characterization of intermediate species, and 3) Di-Air performance compared to other reductants.