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Removal of NOx from Diesel Exhausts: The New “Enhanced NH3-SCR” Reaction

SAE International Journal of Fuels and Lubricants

Politecnico di Milano-Pio Forzatti, Isabella Nova, Enrico Tronconi
  • Journal Article
  • 2010-01-1181
Published 2010-04-12 by SAE International in United States
Ammonia/urea-SCR is a mature technology, applied worldwide for the control of NOx emissions in combustion exhausts from thermal power plants, cogeneration units, incinerators and stationary diesel engines and more recently also from mobile sources. However a greater DeNOx activity at low temperatures is desired in order to meet more and more restrictive legislations.In this paper we report transient and steady state data collected over commercial Fe-ZSM-5 and V₂O₅-WO₃/TiO₂ catalysts showing high NOx reduction efficiencies in the 200 - 350°C T-range when NO and ammonia react with nitrates, e.g., in the form of an aqueous solution of ammonium nitrate. Under such conditions a new reaction occurs, the so-called "Enhanced SCR" reaction, 2 NH₃ + 2 NO + NH₄NO₃ → 3 N₂ + 5 H₂O.Under the conditions of our experiments the new reaction resulted in total conversion both of the nitrates additives and of ammonia, when they were fed in sub-stoichiometric amounts: thus, the "Enhanced SCR" chemistry is also compatible with limitations on the ammonia slip.These results open new pathways for low-T NOx reduction, wherein the amount…
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Dedicated GTL Vehicle: A Calibration Optimization Study

SAE International Journal of Fuels and Lubricants

AUDI AG-Rene Van Doorn
FEV Motorentechnik GmbH-Michael Kind, Andreas Kolbeck, Matthias Lamping
  • Journal Article
  • 2010-01-0737
Published 2010-04-12 by SAE International in United States
GTL (Gas-To-Liquid) fuel is well known to improve tailpipe emissions when fuelling a conventional diesel vehicle, that is, one optimized to conventional fuel. This investigation assesses the additional potential for GTL fuel in a GTL-dedicated vehicle.This potential for GTL fuel was quantified in an EU 4 6-cylinder serial production engine. In the first stage, a comparison of engine performance was made of GTL fuel against conventional diesel, using identical engine calibrations. Next, adaptations enabled the full potential of GTL fuel within a dedicated calibration to be assessed. For this stage, two optimization goals were investigated: - Minimization of NOx emissions and - Minimization of fuel consumption.For each optimization the boundary condition was that emissions should be within the EU5 level. An additional constraint on the latter strategy required noise levels to remain within the baseline reference.Optimizing the calibration for GTL fuel led to further substantial reductions of regulated emissions, i.e., achieving EU 5 levels with a former EU 4 vehicle, as well as significantly reduced exhaust CO₂ emissions.The use of GTL fuel in combination with…
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Development and Validation of PCDD/F Testing Approaches for Mobile Source Engines over Transient and Steady-State Cycles

SAE International Journal of Fuels and Lubricants

Research & Development Cummins Emission Solutions-Z. Gerald Liu, Melissa Dettmann, Adam McDougall McNeilly, Niklas Schmidt, Nathan Ottinger, Michael Jeffery Delaney
  • Journal Article
  • 2010-01-1290
Published 2010-04-12 by SAE International in United States
Advances in aftertreatment technologies, such as Diesel Particulate Filters (DPF) and Selective Catalytic Reduction (SCR) catalysts, have responded to increasingly stringent PM and NO requirements for diesel engines. Potentially viable SCR materials include copper and iron zeolite, which possess high thermal durabilities and conversion efficiencies. However, concern exists over the metal-catalyzed synthesis of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), especially since typical SCR operating temperatures overlap with optimal PCDD/F formation from the de novo and precursor mechanisms. Due to the lack of standardized testing methodology for measuring PCDD/F emissions from mobile sources, this study adapted EPA methods 0023A and TO-9A from their original applications of industrial stack and ambient air sampling. The modifications detailed in this paper accommodated the measurement of PCDD/Fs from a dynamometer-controlled engine, addressing considerations such as temperature excursions, concentrated emissions, transient conditions, and engine vibrations. To validate the modified TO-9A approach, measurements were compared to the previously published results of an EPA-certified CVS tunnel for NO, CO₂, and PM emissions and a CRC study for PAHs and aromatics emissions. The…
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Potential of Cellulose-Derived Biofuels for Soot Free Diesel Combustion

SAE International Journal of Fuels and Lubricants

RWTH Aachen Univ.-Andreas Janssen, Stefan Pischinger, Martin Muether
  • Journal Article
  • 2010-01-0335
Published 2010-04-12 by SAE International in United States
Today's biofuels require large amounts of energy in the production process for the conversion from biomass into fuels with conventional properties. To reduce the amounts of energy needed, future fuels derived from biomass will have a molecular structure which is more similar to the respective feedstock.Butyl levulinate can be gained easily from levulinic acid which is produced by acid hydrolysis of cellulose. Thus, the Institute for Combustion Engines at RWTH Aachen University carried out a fuel investigation program to explore the potential of this biofuel compound, as a candidate for future compression ignition engines to reduce engine-out emissions while maintaining engine efficiency and an acceptable noise level.Previous investigations identified most desirable fuel properties like a reduced cetane number, an increased amount of oxygen content and a low boiling temperature for compression ignition engine conditions. Depending on the chain length, fuel compounds vary in cetane number and boiling temperature. Therefore different blends of butyl levulinate and n-tetradecane, a long-chain alkane, were investigated in this study.To gain knowledge about the combustion process with biofuels, experiments on a…
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Passive Ammonia SCR System for Lean-burn SIDI Engines

SAE International Journal of Fuels and Lubricants

General Motors Global R&D-Wei Li, Kevin L. Perry, Kushal Narayanaswamy, Chang Hwan Kim, Paul Najt
  • Journal Article
  • 2010-01-0366
Published 2010-04-12 by SAE International in United States
Lean-burn Spark Ignition Direct Injection (SIDI) engines offer potential fuel economy savings, however, lack of cost-effective lean NOx aftertreatment systems has hindered its broad application. Lean NO Trap (LNT) and Urea Selective Catalytic Reduction (SCR) technologies have been widely investigated as possible solutions, but they both have considerable drawbacks. LNT catalysts suffer from high Platinum Group Metals (PGM) cost, poor thermal durability, sulfur poisoning and active SO regeneration requirements. Urea SCR systems require a secondary fluid tank with an injection system, resulting in added system cost and complexity. Other concerns for urea SCR include potential freezing of the urea solution and the need for customers to periodically fill the urea reservoir. In this paper we report a low-cost, high efficiency concept that has the potential to be a key enabler for lean-burn gasoline engines. The aftertreatment system includes a close-coupled three-way catalytic converter (TWC) and one or more underfloor SCR catalysts. NH₃ is formed on the TWC during short periods of rich engine operations and the generated NH₃ is then stored on the underfloor SCR…
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Development of Exhaust and Evaporative Emissions Systems for Toyota THS II Plug-in Hybrid Electric Vehicle

SAE International Journal of Fuels and Lubricants

Toyota Motor Corp.-Naoya Takagi, Takashi Watanabe, Shunsuke Fushiki, Makoto Yamazaki, Shuichi Asou, Yuusaku Nishimura
  • Journal Article
  • 2010-01-0831
Published 2010-04-12 by SAE International in United States
Exhaust and evaporative emissions systems have been developed to match the characteristics and usage of the Toyota THS II plug-in hybrid electric vehicle (PHEV). Based on the commercially available Prius, the Toyota PHEV features an additional external charging function, which allows it to be driven as an electric vehicle (EV) in urban areas, and as an hybrid electric vehicle (HEV) in high-speed/high-load and long-distance driving situations.To reduce exhaust emissions, the conventional catalyst warm up control has been enhanced to achieve emissions performance that satisfies California's Super Ultra Low Emissions Vehicle (SULEV) standards in every state of battery charge. In addition, a heat insulating fuel vapor containment system (FVS) has been developed using a plastic fuel tank based on the assumption that such a system can reduce the diffusion of vapor inside the fuel tank and the release of fuel vapor in to the atmosphere to the maximum possible extent.As a result, these measures have enabled the mass-production of the world's first PHEV that satisfies California's SULEV and zero evaporative emissions standards.
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Why Cu- and Fe-Zeolite SCR Catalysts Behave Differently At Low Temperatures

SAE International Journal of Fuels and Lubricants

Cummins Inc.-Krishna Kamasamudram, Neal Currier, Tamas Szailer, Aleksey Yezerets
  • Journal Article
  • 2010-01-1182
Published 2010-04-12 by SAE International in United States
Cu- and Fe-zeolite SCR catalysts emerged in recent years as the primary candidates for meeting the increasingly stringent lean exhaust emission regulations, due to their outstanding activity and durability characteristics. It is commonly known that Cu-zeolite catalysts possess superior activity to Fe-zeolites, in particular at low temperatures and sub-optimal NO₂/NOx ratios. In this work, we elucidate some underlying mechanistic differences between these two classes of catalysts, first based on their NO oxidation abilities, and then based on the relative properties of the two types of exchanged metal sites. Finally, by using the ammonia coverage-dependent NOx performance, we illustrate that state-of-the-art Fe-zeolites can perform better under certain transient conditions than in steady-state.
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Influence of Cold Start and Ambient Temperatures on Greenhouse Gas (GHG) Emissions, Global Warming Potential (GWP) and Fuel Economy for SI Car Real World Driving

SAE International Journal of Fuels and Lubricants

Univ. of Leeds-Hu Li, Gordon E. Andrews, Dimitrios Savvidis
  • Journal Article
  • 2010-01-0477
Published 2010-04-12 by SAE International in United States
The transport sector is one of the major contributors to greenhouse gas emissions. This study investigated three greenhouse gases emitted from road transport using a probe vehicle: CO₂, N₂O and CH₄ emissions as a function of cold start and ambient temperatures. A real-world driving cycle has been developed at Leeds and referred as LU-BS, which has an urban free flow driving pattern. The test vehicle was driven on the same route by the same driver on different days with different ambient temperatures. All the journeys were started from cold. An in-vehicle FTIR emission measurement system was installed on a EURO2 emission compliance SI car for emissions measurement at a rate of 0.5 Hz. This emission measurement system was calibrated on a standard CVS measurement system and showed an excellent agreement on the CO₂ measurement with the CVS results. The N₂O and CH₄ were calibrated by calibration gas bottles. A MAX710 real-time in-vehicle fuel consumption measurement system was installed in the test vehicle and the real-time fuel consumption was then obtained. The Global Warming Potential (GWP)…
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An Adaptive Proportional Integral Control of a Urea Selective Catalytic Reduction System based on System Identification Models

SAE International Journal of Fuels and Lubricants

Ford Motor Co.-Ilya V. Kolmanovsky, Paul Laing, Dennis Reed
MIT-Chun Ong, Anuradha Annaswamy
  • Journal Article
  • 2010-01-1174
Published 2010-04-12 by SAE International in United States
For urea Selective Catalytic Reduction (SCR) systems, adaptive control is of interest to provide a capability of maintaining high NOx conversion efficiency and low ammonia slip in the presence of uncertainties in the system. In this paper, the dynamics of the urea SCR system are represented by a control-oriented model which is based on a linear transfer function, with parameters dependent on engine operating conditions. The parameters are identified from input-output data generated by a high fidelity full chemistry model of the urea SCR system. The use of the full chemistry model facilitated the representation of the dynamics of stored ammonia (not a directly measurable parameter) as well as post SCR NOx and ammonia slip.A closed-loop Proportional-plus-Integral (PI) controller was first designed using the estimate of stored ammonia as a feedback signal. The performance was evaluated using the full chemistry model, and was shown to result in a NOx conversion efficiency of over 95%, with a maximum NH₃-slip of less than 5 ppm. An adaptive PI controller was then designed and tested, and was shown…
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Particulate Matter Trapping and Oxidation on a Catalyst Membrane

SAE International Journal of Fuels and Lubricants

Tokyo Institute of Technology-Preechar Karin, Katsunori Hanamura
  • Journal Article
  • 2010-01-0808
Published 2010-04-12 by SAE International in United States
Particulate matter (PM) trapping and oxidation in regeneration on the surface of a diesel particulate catalyst-membrane filter (DPMFs) were investigated in detail using an all-in-focus optical microscope. The DPMF consists of two-layer sintered filters, where a SiC-nanoparticle membrane (made from a mixture of 80 nm and 500 nm powders) covers the surface of a conventional SiC filter. Using a visualization experiment, it was shown that PMs were trapped homogeneously along fine surface pores of the membrane's top surface, whereas in the regeneration process, the particulates in contact with the membrane may have been oxidized with some catalytic effect of the SiC nanoparticles. A soot cake was reacted continuously on the nanoparticles since pushed by a gas flow. The oxidation temperature of particulate trapped on the SiC-nanoparticle membrane was about 75 degrees lower than that on the conventional diesel particulate filters (DPF) without a catalyst. The activation energy of reaction on the nanoparticle membrane became lower than that on the conventional SiC-DPF without catalyst. Consequently, the SiC-nanoparticles membrane filters had some catalytic activity similar to that…
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