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Technical Paper

Low Temperature SCR Catalysts Optimized for Cold-Start and Low-Load Engine Exhaust Conditions

2015-04-14
2015-01-1026
The main objective of this work is to develop a low-temperature SCR catalyst for the reduction of nitrogen oxides at cold start, low-idle and low-load conditions. A series of metal oxide- incorporated beta zeolite catalysts were prepared by adopting incipient wetness technique, cation-exchange, deposition-precipitation and other synthesis techniques. The resulting catalysts were characterized and tested for reduction of NOx in a fixed bed continuous flow quartz micro-reactor using ammonia as the reductant gas. Initial catalyst formulations have been exhibited good NOx reduction activity at low-temperatures. These catalyst formulations showed a maximum NOx conversion in the temperature range of 100 - 350°C. Besides, more experiments were performed with the aim of optimizing these formulations with respect to the metal atomic ratio, preparation method, active components and supported metal type.
Technical Paper

CFD Optimization of Exhaust Manifold for Large Diesel Engine Aftertreatment Systems

2011-09-13
2011-01-2199
To meet EPA Tier IV large diesel engine emission targets, intensive development efforts are necessary to achieve NOx reduction and Particulate Matter (PM) reduction targets [1]. With respect to NOx reduction, liquid urea is typically used as the reagent to react with NOx via SCR catalyst [2]. Regarding to PM reduction, additional heat is required to raise exhaust temperature to reach DPF active / passive regeneration performance window [3]. Typically the heat can be generated by external diesel burners which allow diesel liquid droplets to react directly with oxygen in the exhaust gas [4]. Alternatively the heat can be generated by catalytic burners which enable diesel vapor to react with oxygen via DOC catalyst mostly through surface reactions [5].
Technical Paper

A Dual - Reductant HC LNC Approach to Commercial Vehicle Tier 4 Final Solutions

2011-09-13
2011-01-2203
Stringent global emissions legislations demand effective NOx reduction strategies for both the engine as well as the aftertreatment. Diesel applications have previously applied Lean NOx Catalysts (LNCs) [1, 2], but their reduction efficiency and longevity have been far less than that of the competing ammonia-based SCR systems, such as urea [3]. A catalyst has been developed to significantly reduce NOx emissions, approaching 60% with ULSD and exceeding 95% with E85. Both thermal and sulfur aging are applied, as well as on-engine aging, illustrating resilient performance to accommodate necessary life requirements. A robust system is developed to introduce both ULSD from the vehicle's tank as well as E85 (up to 85% ethanol with the balance being gasoline) from a moderately sized supplemental tank, enabling extended mileage service intervals to replenish the reductant, as compared with urea, particularly when coupled with an engine-out based NOx reduction technology, such as EGR.
Technical Paper

DPF Regeneration Response: Coupling Various DPFs with a Thermal Regeneration Unit to Assess System Behaviors

2011-09-13
2011-01-2200
Diesel Particulate Filters (DPFs) have been successfully applied for several years to reduce Particulate Matter (PM) emissions from on-highway applications, and similar products are now also applied in off-highway markets and retrofit solutions. Most solutions are catalytically-based, necessitating minimum operating temperatures and demanding engine support strategies to reduce risks [1, 2, 3, 4, 5, 6, 7, 8]. An ignition-based thermal combustion device is applied with Cordierite and SiC filters, evaluating various DPF conditions, including effects of soot load, exhaust flow rates, catalytic coatings, and regeneration temperatures. System designs are described, including flow and temperature uniformity, as well as soot load distribution and thermal gradient response.
Technical Paper

SOLID SCR®: Demonstrating an Improved Approach to NOx Reduction via a Solid Reductant

2011-09-13
2011-01-2207
Stringent global emissions legislation demands effective NOx reduction strategies, particularly for the aftertreatment, and current typical liquid urea SCR systems achieve efficiencies greater than 90% [1]. However, with such high-performing systems comes the trade-off of requiring a tank of reductant (urea water solution) to be filled regularly, usually as soon as the fuel fillings or as far as oil changes. Advantages of solid reductants, particularly ammonium carbamate, include greater ammonia densities, enabling the reductant refill interval to be extended several multiples versus a given reductant volume of urea, or diesel exhaust fluid (DEF) [2]. An additional advantage is direct gaseous ammonia dosing, enabling reductant injection at lower exhaust temperatures to widen its operational coverage achieving greater emissions reduction potential [3], as well as eliminating deposits, reducing mixing lengths, and avoiding freeze/thaw risks and investments.
Technical Paper

Development of Urea SCR Systems for Large Diesel Engines

2011-09-13
2011-01-2204
EPA 2015 Tier IV emission requirements pose significant challenges to large diesel engine after treatment system development with respect to reducing exhaust emissions including HC, CO, NOx and Particulate Matter (PM). For a typical locomotive, marine or stationary generator engine with 8 to 20 cylinders and 2500 to 4500 BHP, the PM reduction target could be over 90% and NOx reduction target over 75% for a wide range of running conditions. Generally, HC, CO and PM reductions can be achieved by combining DOC, cDPF and active regeneration systems. NOx reduction can be achieved by injecting urea as an active reagent into the exhaust stream to allow NOx to react with ammonia per SCR catalysts, as the mainstream approach for on-highway truck applications.
Technical Paper

Investigation of Urea Deposits in Urea SCR Systems for Medium and Heavy Duty Trucks

2010-10-05
2010-01-1941
With increasing applications of urea SCR for NOx emission reduction, improving the system performance and durability has become a high priority. A typical urea SCR system includes a urea injector, injector housing, mixer, and appropriate pipe configurations to allow continuous urea injection into the exhaust stream and evaporation of urea solution into gaseous products. Continuous operation at various conditions with high NOx reduction is possible, but one problem that threatens the life and performance of these systems is urea deposit. When urea or its byproducts become deposited on the inner surfaces of the system including walls, mixers, injector housings and substrates it can create concerns of backpressure and material deteriorations. In addition, deposits as a waste of reagents can negatively affect engine operation, emissions performance and DEF economy. Urea deposit behavior is explored in terms of heat transfer, pipe geometry, injector layout and mixing mechanisms.
Technical Paper

Evaluation of Mixer Designs for Large Diesel Exhaust Aftertreatment Systems

2010-10-05
2010-01-1943
The presented work evaluates several mixer designs being considered for use in large Diesel exhaust aftertreatment systems. The mixers are placed upstream of a diesel oxidation catalyst (DOC) in the exhaust system, where a liquid hydrocarbon fuel is injected. DOC exothermic behaviour resulting from each mixer at different operating conditions is evaluated. A gas flow bench equipped with a XY-Table measurement system is used to determine gas velocity, temperature, and hydrocarbon species uniformity, as well as, pressure drop. Experimental mixer data obtained from a flow bench and an engine dynamometer are compared and discussed. The experimental methodology used in this study can be used to evaluate mixers via comprehensive testing.
Technical Paper

Optimization of a Urea SCR System for On-Highway Truck Applications

2010-10-05
2010-01-1938
In order to satisfy tightening global emissions regulations, diesel truck manufacturers are striving to meet increasingly stringent Oxides of Nitrogen (NOx) reduction standards. The majority of heavy duty diesel trucks have integrated urea SCR NOx abatement strategies. To this end, aftertreatment systems need to be properly engineered to achieve high conversion efficiencies. A EuroV intent urea SCR system is evaluated and failed to meet NOx conversion targets with severe urea deposit formation. Systematic enhancements of the design have been performed to enable it to meet targets, including emission reduction efficiency via improved reagent mixing, evaporation, distribution, back pressure, and removing of urea deposits. Multiple urea mixers, injector mounting positions and various system layouts are developed and evaluated, including both CFD analysis and full scale laboratory tests.
Technical Paper

Support Mat Test Equipment Artifact Identification and Elimination

2009-04-20
2009-01-0978
Monolithic emission control devices typically use a support mat material to provide mechanical support, mechanical isolation, and thermal insulation for ceramic monoliths. This material is similar to a felt, but made from ceramic fibers. Non-intumescent support mat materials contain only ceramic fibers and binder compounds, while intumescent support mats also contain vermiculite; a material that expands with the application of heat. The durability of the support mat is critical to the durability of the overall emission control components. In addition to many component validation methods that evaluate the durability of the entire system methods to evaluate the response and predict the durability of the support mat itself help provide important design information. This paper summarizes challenges and artifacts in support mat testing.
Technical Paper

Material Corrosion Investigations for Urea SCR Diesel Exhaust Systems

2009-10-06
2009-01-2883
New emissions standards for oxides of nitrogen (NOx) in on-road diesel vehicles are effective in 2010, and a common approach applies urea selective catalytic reduction (SCR). Urea is injected into the exhaust and decomposes to form ammonia, which chemically reacts with NOx as it passes through an SCR catalyst. Ammonia is corrosive and negatively affects typical stainless steels used in exhaust applications, but these corrosive impacts have not yet been quantified in an exhaust system. Two unique corrosion tests are performed on a number of various stainless steel samples, illustrating such performance concerns with 409, while offering alternatives with much better performance, including cost-effective options. The method applied is described, yielding performance criteria through appearance, weight loss, and corrosion pit depth.
Technical Paper

Evaluation of a DPF Regeneration System and DOC Performance Using Secondary Fuel Injection

2009-10-06
2009-01-2884
An active diesel particulate filter (DPF) regeneration system is evaluated, which applies secondary fuel injection (SFI) directly within the exhaust system upstream of a diesel oxidation catalyst (DOC). Diesel fuel is oxidized in the presence of a proprietary catalyst system, increasing exhaust gas temperatures in an efficient and controlled manner, even during low engine-out gas temperatures. The exotherms produced by secondary fuel injection (SFI) have been evaluated using two different DOC volumes and platinum catalyst loadings. DOC light-off temperatures were measured using SFI under steady-state conditions on an engine dynamometer. A ΔT method was used for the light-off temperature measurements – i.e., the minimum DOC inlet gas temperature at which the exothermic reaction increases the outlet gas temperature 20°C or greater than the inlet temperature.
Technical Paper

Mixer Development for Urea SCR Applications

2009-10-06
2009-01-2879
2010 and future EPA regulations introduce stringent Oxides of Nitrogen (NOx) reduction targets for diesel engines. Selective Catalytic Reduction (SCR) of NOx by Urea over catalyst has become one of the main solutions to achieve these aggressive reductions. As such, urea solution is injected into the exhaust gas, evaporated and decomposed to ammonia via mixing with the hot exhaust gas before passing through an SCR catalyst. Urea mixers, in this regard, are crucial to ensure successful evaporation and mixing since its liquid state poses significant barriers, especially at low temperature conditions that incur undesired deposits. Intensive efforts have been taken toward developing such urea mixers, and multiple criteria have been derived for them, mainly including NOx reduction efficiency and uniformity. In addition, mixers must also satisfy other requirements such as low pressure drop penalty, mechanical strength, material integrity, low cost, and manufacturability.
Technical Paper

Design Improvements of Urea SCR Mixing for Medium-Duty Trucks

2013-04-08
2013-01-1074
To meet the 2010 diesel engine emission regulations, an aftertreatment system was developed to reduce HC, CO, NOx and soot. In NOx reduction, a baseline SCR module was designed to include urea injector, mixing decomposition tube and SCR catalysts. However, it was found that the baseline decomposition tube had unacceptable urea mixing performance and severe deposit issues largely because of poor hardware design. The purpose of this article is to describe necessary development work to improve the baseline system to achieve desired mixing targets. To this end, an emissions Flow Lab and computational fluid dynamics were used as the main tools to evaluate urea mixing solutions. Given the complicated urea spray transport and limited packaging space, intensive efforts were taken to develop pre-injector pipe geometry, post-injector cone geometry, single mixer design modifications, and dual mixer design options.
Technical Paper

Passive Regeneration Response Characteristics of a DPF System

2013-04-08
2013-01-0520
This study investigates the passive regeneration behavior of diesel particulate filters (DPFS) with various PGM loadings under different engine operating conditions. Four wall-flow DPFs are used; one uncoated and three wash-coated with low, medium, and high PGM loadings, with and without an upstream diesel oxidation catalyst (DOC). DPFs with variable pre-soot loads are evaluated at two steady state temperatures (300°C and 400°C), as well as across three levels of transients based on the 13-mode ESC cycle. Passive regeneration rates are calculated based on pre and post soot gravimetric measurements along with accumulated soot mass rates for specified exhaust mass flow rates and temperatures. Results illustrate the effect of temperature, NO₂ content, and soot loading on passive regeneration without upstream DOCs or DPF wash coatings.
Technical Paper

Overview of Large Diesel Engine Aftertreatment System Development

2012-09-24
2012-01-1960
The introduction of stringent EPA 2015 regulations for locomotive / marine engines and IMO 2016 Tier III marine engines initiates the need to develop large diesel engine aftertreatment systems to drastically reduce emissions such as SOx, PM, NOx, unburned HC and CO. In essence, the aftertreatment systems must satisfy a comprehensive set of performance criteria with respect to back pressure, emission reduction efficiency, mixing, urea deposits, packaging, durability, cost and others. Given multiple development objectives, a systematic approach must be adopted with top-down structure that addresses top-level technical directions, mid-level subsystem layouts, and bottom-level component designs and implementations. This paper sets the objective to provide an overview of system development philosophy, and at the same time touch specific development scenarios as illustrations.
Technical Paper

Transient Performance of an HC LNC Aftertreatment System Applying Ethanol as the Reductant

2012-09-24
2012-01-1957
As emissions regulations around the world become more stringent, emerging markets are seeking alternative strategies that align with local infrastructures and conditions. A Lean NOx Catalyst (LNC) is developed that achieves up to 60% NOx reduction with ULSD as its reductant and ≻95% with ethanol-based fuel reductants. Opportunities exist in countries that already have an ethanol-based fuel infrastructure, such as Brazil, improving emissions reduction penetration rates without costs and complexities of establishing urea infrastructures. The LNC performance competes with urea SCR NOx reduction, catalyst volume, reductant consumption, and cost, plus it is proven to be durable, passing stationary test cycles and adequately recovering from sulfur poisoning. Controls are developed and applied on a 7.2L engine, an inline 6-cylinder non-EGR turbo diesel.
Technical Paper

Development of Low Temperature Selective Catalytic Reduction (SCR) Catalysts for Future Emissions Regulations

2014-04-01
2014-01-1520
A series of novel metal-oxide (TiO2, TiO2-SiO2)-supported Mn, Fe, Co, V, Cu and Ce catalysts were prepared by incipient wetness technique and investigated for the low-temperature selective catalytic reduction (SCR) of NOx with ammonia at industrial relevantly conditions. Among all the prepared catalysts, Cu/TiO2 showed superior de-NOx performance in the temperature range of 150-200 °C followed by Mn/TiO2 in the temperature range of 200-250 °C. The Ce/TiO2 catalyst exhibited a broad temperature window with notable de-NOx performance in the temperature regime of 250-350 °C. The phyico-chemical characterization results revealed that the activity enhancement was correlated with the properties of the support material. All the anatasetitania-supported catalysts (M/TiO2 (Hombikat)) demonstrated significantly high de-NOx performance above 150 °C.
Technical Paper

Clean EGR for Gasoline Engines – Innovative Approach to Efficiency Improvement and Emissions Reduction Simultaneously

2017-03-28
2017-01-0683
External Exhaust Gas Recirculation (EGR) has been used on diesel engines for decades and has also been used on gasoline engines in the past. It is recently reintroduced on gasoline engines to improve fuel economy at mid and high engine load conditions, where EGR can reduce throttling losses and fuel enrichment. Fuel enrichment causes fuel penalty and high soot particulates, as well as hydrocarbon (HC) emissions, all of which are limited by emissions regulations. Under stoichiometric conditions, gasoline engines can be operated at high EGR rates (> 20%), but more than diesel engines, its intake gas including external EGR needs extreme cooling (down to ~50°C) to gain the maximum fuel economy improvement. However, external EGR and its problems at low temperatures (fouling, corrosion & condensation) are well known.
Technical Paper

Data Analysis, Modeling, and Predictability of Automotive Events

2018-04-03
2018-01-0094
It is important to quantitatively characterize the automotive events in order to not only accurately interpret their past but also to reliably predict and forecast their short-term, medium-term, and even long-term future. In this paper, several automotive industry related events, i.e. vehicle safety, vehicle weight/HP ratio, the emissions of CO2, HC, CO, and NOx, are analyzed to find their general trends. Exponential and power law functions are used to empirically fit and quantitatively characterize these data with an emphasis on the two functions’ effectiveness in predictability. Finally, three empirical emission laws based on the historical HC, CO, and NOx data are proposed and the impact of these laws on emission control is discussed.
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