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Viewing 121 to 150 of 22747
2015-04-14
Journal Article
2015-01-1244
Luigi Teodosio, Vincenzo De Bellis, Fabio Bozza
Abstract It is well known that the downsizing philosophy allows the improvement of Brake Specific Fuel Consumption (BSFC) at part load operation for spark ignition engines. On the other hand, the BSFC is penalized at high/full load operation because of the knock occurrence and of further limitations on the Turbine Inlet Temperature (TIT). Knock control forces the adoption of a late combustion phasing, causing a deterioration of the thermodynamic efficiency, while TIT control requires enrichment of the Air-to-Fuel (A/F) ratio, with additional BSFC drawbacks. In this work, a promising technique, consisting of the introduction of a low-pressure cooled exhaust gas recirculation (EGR) system, is analyzed by means of a 1D numerical approach with reference to a downsized turbocharged SI engine. Proper “in-house developed” sub-models are used to describe the combustion process, turbulence phenomenon and the knock occurrence.
2015-04-14
Journal Article
2015-01-1253
Konstantinos Siokos, Rohit Koli, Robert Prucka, Jason Schwanke, Julia Miersch
Abstract The use of Low Pressure - Exhaust Gas Recirculation (EGR) is intended to allow displacement reduction in turbocharged gasoline engines and improve fuel economy. Low Pressure EGR designs have an advantage over High Pressure configurations since they interfere less with turbocharger efficiency and improve the uniformity of air-EGR mixing in the engine. In this research, Low Pressure (LP) cooled EGR is evaluated on a turbocharged direct injection gasoline engine with variable valve timing using both simulation and experimental results. First, a model-based calibration study is conducted using simulation tools to identify fuel efficiency gains of LP EGR over the base calibration. The main sources of the efficiency improvement are then quantified individually, focusing on part-load de-throttling of the engine, heat loss reduction, knock mitigation as well as decreased high-load fuel enrichment through exhaust temperature reduction.
2015-04-14
Technical Paper
2015-01-1250
Nisar Al-Hasan, Johannes Beer, Jan Ehrhard, Thomas Lorenz, Ludwig Stump
Abstract In the past few years the gasoline direct injection (GDI) downsizing approach was the dominating gasoline engine technology used to reduce CO2 emission and to guarantee excellent transient performance. Forecasts for the next several years indicate that the worldwide market share of GDI engines will grow further. By 2022 it is expected that the gasoline DI engine will be the most popular combustion engine for passenger car application. However in the future the gasoline engine will have to comply with more stringent emission and CO2 standards. The European legislation demands a fleet average CO2 emission of 95g/km latest by 2021. Therefore, CO2 emission improvement, without compromising driveability, is the major goal of powertrain development. The perspective of more stringent CO2 and emission legislation in highly loaded drive cycle necessitates major development efforts.
2015-04-14
Technical Paper
2015-01-1251
Fabien Redon, Arunandan Sharma, John Headley
Abstract In a recent paper, Opposed-Piston 2-Stroke Multi-Cylinder Engine Dynamometer Demonstration [1] published at the SAE SIAT in India in January 2015, Achates Power presented work related to the first ever opposed piston multi-cylinder engine fuel economy demonstration while meeting US 2010 emissions. The results showed that the research 4.9L three cylinder engine was able to achieve 43% brake thermal efficiency at the best point and almost 42% on average over the 12 modes of the SET cycle. The results from this test confirmed the modelling predictions and carved a very robust path to a 48% best BTE and 46.6% average over the cycle for a production design of this engine. With the steady state performance and emissions results achieved, it was time to explore other attributes.
2015-04-14
Technical Paper
2015-01-1264
Junseok Chang, Yoann Viollet, Abdullah Alzubail, Amir Faizal Naidu Abdul-Manan, Abdullah Al Arfaj
Abstract This paper explores the potential for reducing transport-related greenhouse gas (GHG) emissions by introducing high-efficiency spark-ignition engines with a dual-fuel injection system to customize the octane of the fuels based on real-time engine requirements. It is assumed that a vehicle was equipped with two fuel tanks and two injection systems; one port fuel injection and one direct injection line separately. Each tank carried low octane and high octane fuel so that real-time octane blending was occurred in the combustion chamber when needed (Octane On-Demand: OOD). A refinery naphtha was selected for low octane fuel (RON=61), because of its similarity to gasoline properties but a less processed, easier to produce without changing a refinery configuration. Three oxygenates were used for high octane knock-resistant fuels in a direct injection line: methanol, MTBE, and ETBE.
2015-04-14
Technical Paper
2015-01-0914
Ehsan Tootoonchi, Gerald Micklow
Abstract Understanding the physics and chemistry involved in diesel combustion, with its transient effects and the inhomogeneity of spray combustion is quite challenging. Great insight into the physics of the problem can be obtained when an in-cylinder computational analysis is used in conjunction with either an experimental program or through published experimental data. The main area to be investigated to obtain good combustion begins with the fuel injection process and the mean diameter of the fuel particle, injection pressure, drag coefficient, rate shaping etc. must be defined correctly. The increased NOx production and reduced power output found in engines running biodiesel in comparison to petrodiesel is believed to be related to the different fuel characteristics in comparison to petroleum based diesel. The fuel spray for biodiesel penetrates farther into the cylinder with a smaller cone angle. Also the fuel properties between biodiesel and petrodiesel are markedly different.
2015-04-14
Journal Article
2015-01-0892
Alastair Smith, Rod Williams
Abstract The formation of deposits within injector nozzle holes of common-rail injection fuel systems fitted to modern diesel cars can reduce and disrupt the flow of fuel into the combustion chamber. This disruption in fuel flow results in reduced or less efficient combustion and lower power output. Hence there is sustained interest across the automotive industry in studying these deposits, with the ultimate aim of controlling them. In this study, we describe the use of Scanning Electron Microscopy (SEM) imaging to characterise fuel injector hole deposits at intervals throughout an adaptation of the CEC Direct Injection Common Rail Diesel Engine Nozzle Coking Test, CEC F-98-08 (DW10B test)[1]. In addition, a similar adaptation of a previously published Shell vehicle test method [2] was employed to analyse fuel injector hole deposits from a fleet of Euro 5 vehicles.
2015-04-14
Journal Article
2015-01-0890
Barbara Graziano, Florian Kremer, Stefan Pischinger, Karl Alexander Heufer, Hans Rohs
Abstract The current and future restrictions on pollutant emissions from internal combustion engines require a holistic investigation of the abilities of alternative fuels to optimize the combustion process and ensure cleaner combustion. In this regard, the Tailor-made Fuels from Biomass (TMFB) Cluster at Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen University aims at designing production processes for biofuels as well as fuels optimal for use in internal combustion engines. The TMFB Cluster's scientific approach considers the molecular structure of the fuels as an additional degree of freedom for the optimization of both the production pathways and the combustion process of such novel biofuels. Thus, the model-based specification of target parameters is of the utmost importance to improve engine combustion performance and to send feedback information to the biofuel production process.
2015-04-14
Journal Article
2015-01-0902
Koichi Ashida, Hirofumi Maeda, Takashi Araki, Maki Hoshino, Koji Hiraya, Takao Izumi, Masayuki Yasuoka
Abstract To improve the fuel economy via high EGR, combustion stability is enhanced through the addition of hydrogen, with its high flame-speed in air-fuel mixture. So, in order to realize on-board hydrogen production we developed a fuel reformer which produces hydrogen rich gas. One of the main issues of the reformer engine is the effects of reformate gas components on combustion performance. To clarify the effect of reformate gas contents on combustion stability, chemical kinetic simulations and single-cylinder engine test, in which hydrogen, CO, methane and simulated gas were added to intake air, were executed. And it is confirmed that hydrogen additive rate is dominant on high EGR combustion. The other issue to realize the fuel reformer was the catalyst deterioration. Catalyst reforming and exposure test were carried out to understand the influence of actual exhaust gas on the catalyst performance.
2015-04-14
Journal Article
2015-01-0957
George Karavalakis, Daniel Short, Diep Vu, Robert Russell, Akua Asa-Awuku, Thomas Durbin
Abstract Biofuels, such as ethanol and butanol, have been the subject of significant political and scientific attention, owing to concerns about climate change, global energy security, and the decline of world oil resources that is aggravated by the continuous increase in the demand for fossil fuels. This study evaluated the potential emissions impacts of different alcohol blends on a fleet of modern gasoline vehicles. Testing was conducted on a fleet of nine vehicles with different combinations of ten fuel blends over the Federal Test Procedure and Unified Cycle. The vehicles ranged in model year from 2007-2014 and included four vehicles with port fuel injection (PFI) fueling and five vehicles with direct injection (DI) fueling.
2015-04-14
Journal Article
2015-01-0984
Yang Zheng, Mengmeng Li, Michael Harold, Dan Luss
Abstract Current NOx emission reduction systems, selective catalytic reduction (SCR) and NOx storage and reduction (NSR), function well after achieving their operation temperature (typically ca. 250 °C) but have unsatisfactory NOx conversion at lower exhaust temperatures encountered during cold start and low load operation. The reduced exhaust temperature of advanced diesel engines with higher fuel efficiency challenges the low-T NOx reduction. We report here a new concept of high low-T deNOx efficiency of up to 80% at a feed temperature of ca. 200 °C at relevant space velocities (70k h−1). It utilizes high-frequency hydrocarbon pulsing on a dual-layer LNT-SCR monolithic catalyst under lean conditions. This system has the potential to expand the operating temperature window of the conventional deNOx devices.
2015-04-14
Journal Article
2015-01-0991
Nathan Ottinger, Rebecca Veele, Yuanzhou Xi, Z. Gerald Liu
Abstract Lean-burn natural gas (NG) engines are used world-wide for both stationary power generation and mobile applications ranging from passenger cars to Class 8 line-haul trucks. With the recent introduction of hydraulic fracturing gas extraction technology and increasing availability of natural gas, these engines are receiving more attention. However, the reduction of unburned hydrocarbon emissions from lean-burn NG and dual-fuel (diesel and natural gas) engines is particularly challenging due to the stability of the predominant short-chain alkane species released (e.g., methane, ethane, and propane). Supported Pd-based oxidation catalysts are generally considered the most active materials for the complete oxidation of low molecular weight alkanes at temperatures typical of lean-burn NG exhaust. However, these catalysts rapidly degrade under realistic exhaust conditions with high water vapor concentrations and traces of sulfur.
2015-04-14
Journal Article
2015-01-0988
Fabien Ocampo, Virginie Harle, Naotaka Ohtake, Renaud Rohe, Barry W.L. Southward
Abstract The reduction of NOx to meet current diesel regulation standards has been achieved using two main technologies named NH3-SCR and LNT. In the forthcoming years, the implementation of new and colder test cycles such as “real driving emissions” (RDE), combined with CO2 targets (95 g/km is 2020 target in Europe) will require higher NOx storage capacity (NSC) in the low temperature region (120-350°C). On the other hand, lean-burn Gasoline vehicles, emitting exhaust gases at higher temperatures, will require improved NSC over a broader temperature range (200-500°C). Therefore, the development of more efficient NSC materials is an area of extensive study by original equipment manufacturers (OEMs), catalysts manufacturers, and raw materials suppliers. Today, ceria is a key component in the formulation of active NSC washcoats.
2015-04-14
Technical Paper
2015-01-1036
Lei Liu, Zhijun Li, Boxi Shen
Abstract Ensuring lower emissions and better economy (fuel economy and after-treatment economy) simultaneously is the pursuit of future engines. An EGR-LNT synergetic control system was applied to a modified lean-burn CA3GA2 gasoline engine. Results showed that the synergetic control system can achieve a better NOx reduction than sole EGR and sole LNT within a proper range of upstream EGR rate and without the penalty in fuel consumption. It also has the potential to save costly noble metals in LNT, but excessive or deficient upstream EGR would make the synergetic control system inefficiency. In order to guarantee the objectivity of the effect of EGR-LNT synergetic control system on NOx reduction, another modified lean-burn CA4GA5 gasoline engine was additionally tested.
2015-04-14
Journal Article
2015-01-1037
Colin L. Weeks, Dan R. Ibeling, Sonia Han, Lindsey Ludwig, Ponnaiyan Ayyappan
Abstract An aqueous urea solution is used as the source of ammonia for selective catalytic reduction (SCR) of NOx to reduce the emissions of NOx in the exhaust of diesel vehicles. However, the decomposition of urea into ammonia is not always complete, resulting in solid urea deposit formation in the decomposition tube or on the SCR catalyst. These solid deposits can impede the flow of the exhaust gases (and uniformity of NH3 supply) and reduce SCR catalyst performance over time. To minimize the formation of urea deposit and to meet EPA NOx emission regulations, it is important to understand the chemistry of formation or removal of the deposit in the decomposition tube and SCR catalyst. In this report, IR spectroscopy, UV-visible spectroscopy, thermogravimetric analysis and elemental analysis have been used to determine the chemical composition of the solid urea deposits formed by the thermal decomposition of urea.
2015-04-14
Journal Article
2015-01-1035
Yanxiang Yang, Bingqian Tan, Changwen Liu, Ping Zhang, Daguang Xi
Abstract A versatile liquid dosing device along with its metering theory, which can be applied to both SCR dosing system and DPF regeneration system of IC engine after-treatment system, is presented in this paper. The device is composed of a solenoid driven plunger pump, a nozzle and a pressure tube, and is pump-end controlled by PWM signals. Both electrically resistive and conductive liquids including DEF for SCR system, fuel for DPF regeneration, and gasoline for spark ignition engine, can be dispensed quantitatively with this device. A metering theory determining the liquid discharged per injection is developed by studying the system using a physical-mathematical model. The study shows that the liquid discharge can be well correlated with a measurable variable T3, which is associated with the net output energy. Experimental investigations verified that the metering results were independent of the state changes.
2015-04-14
Technical Paper
2015-01-1033
Raymond Conway, Sougato Chatterjee, Mojghan Naseri, Ceren Aydin
Abstract Selective Catalytic Reduction (SCR) catalysts have been demonstrated as an effective solution for controlling NOx emissions from diesel engines. Typical 2013 Heavy Duty Diesel emission control systems include a DOC upstream of a catalyzed soot filter (CSF) which is followed by urea injection and the SCR sub-assembly. There is a strong desire to further increase the NOx conversion capability of such systems, which would enable additional fuel economy savings by allowing engines to be calibrated to higher engine-out NOx levels. One potential approach is to replace the CSF with a diesel particulate filter coated with SCR catalysts (SCRF® technology, hereafter referred to as SCR-DPF) while keeping the flow-through SCR elements downstream, which essentially increases the SCR volume in the after-treatment assembly without affecting the overall packaging.
2015-04-14
Technical Paper
2015-01-1031
Nic van Vuuren, Gabriele Brizi, Giacomo Buitoni, Lucio Postrioti, Carmine Ungaro
Abstract The recent implementation of new rounds of stringent nitrogen oxides (NOx) emissions reduction legislation in Europe and North America is driving the expanded use of exhaust aftertreatment systems, including those that treat NOx under the high-oxygen conditions typical of lean-burn engines. One of the favored aftertreatment solutions is referred to as Selective Catalytic Reduction (SCR), which comprises a catalyst that facilitates the reactions of ammonia (NH3) with the exhaust nitrogen oxides (NOx). It is customary with these systems to generate the NH3 by injecting a liquid aqueous urea solution, typically at a 32% concentration of urea (CO(NH2)2). The solution is referred to as AUS-32, and is also known under its commercial name of AdBlue® in Europe, and DEF - Diesel Exhaust Fluid - in the USA. The urea solution is injected into the exhaust and transformed to NH3 by various mechanisms for the SCR reactions.
2015-04-14
Technical Paper
2015-01-1030
Ashok Kumar, Krishna Kamasamudram, Neal Currier, Aleksey Yezerets
Abstract The high global warming potential of nitrous oxide (N2O) led to its inclusion in the list of regulated greenhouse gas (GHG) pollutants [1, 2]. The mitigation of N2O on aftertreatment catalysts was shown to be ineffective as its formation and decomposition temperatures do not overlap. Therefore, the root causes for N2O formation were investigated to enable the catalyst architectures and controls development for minimizing its formation. In a typical heavy-duty diesel exhaust aftertreatment system based on selective catalytic reduction of NOx by ammonia derived from urea (SCR), the main contributors to tailpipe N2O are expected to be the undesired reaction between NOx and NH3 over SCR catalyst and NH3 slip in to ammonia slip catalyst (ASC), part of which gets oxidized to N2O.
2015-04-14
Journal Article
2015-01-1028
Paul Gaynor, Benjamin Reid, Graham Hargrave, Thomas Lockyer, Jonathan Wilson
Abstract In recent years urea selective catalytic reduction (SCR) has become the principal method of NOx abatement within heavy duty (HD) diesel exhaust systems; however, with upcoming applications demanding NOx reduction efficiencies of above 96 % on engines producing upwards of 10 g·kWh−1 NOx, future diesel exhaust fluid (DEF) dosing systems will be required to operate stably at significantly increased dosing rates. Developing a dosing system capable of meeting the increased performance requirements demands an improved understanding of how DEF sprays interact with changing exhaust flows. This study has investigated four production systems representing a diverse range of dosing strategies in order to determine how performance is influenced by spray structure and identify promising strategies for further development. The construction of an optically accessible hot-air flow rig has enabled visualisation of DEF injection into flows representative of HD diesel exhaust conditions.
2015-04-14
Technical Paper
2015-01-1045
Stephan Stadlbauer, Harald Waschl, Luigi del Re
Abstract The focus in the development of modern exhaust after treatment systems, like the Diesel Oxidation Catalyst (DOC), the Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR), is to increase on one hand the oxidation rates of Carbon monoxide (CO), HC (Hydro Carbons) and NO (Nitrogen Oxide) and on the other hand the reduction rates of Particulate Matter (PM) and the NOx emissions to fulfill the more and more restricting requirements of the exhaust emission legislation. The simplest, practical most relevant way to obtain such a dosing strategy of a SCR system is the use of a nonlinear map, which has to be determined by extensive calibration efforts. This feedforward action has the advantage of not requiring a downstream NOx sensor and can achieve high conversion efficiency under steady-state operating conditions for nominal systems.
2015-04-14
Technical Paper
2015-01-1044
Kiran C. Premchand, Krishnan Raghavan, John H. Johnson
Abstract Numerical models of aftertreatment devices are increasingly becoming indispensable tools in the development of aftertreatment systems that enable modern diesel engines to comply with exhaust emissions regulations while minimizing the cost and development time involved. Such a numerical model was developed at Michigan Technological University (MTU) [1] and demonstrated to be able to simulate the experimental data [2] in predicting the characteristic pressure drop and PM mass retained during passive oxidation [3] and active regeneration [4] of a catalyzed diesel particulate filter (CPF) on a Cummins ISL engine. One of the critical aspects of a calibrated numerical model is its usability - in other words, how useful is the model in predicting the pressure drop and the PM mass retained in another particulate filter on a different engine without the need for extensive recalibration.
2015-04-14
Journal Article
2015-01-1043
Xian Shi, Reinhard Seiser, Jyh-Yuan Chen, Robert Dibble, Robert Cattolica
Abstract Steady-state, transient and dithering characteristics of emission conversion efficiencies of three-way catalysts on natural gas IC engine were investigated experimentally on a single-cylinder CFR engine test bench. Steady-state runs were conducted as references for specific engine emission levels and corresponding catalyst capacities. The steady-state data showed that conversion of HC will be the major problem since conversion of HC was effective only for a very narrow range of exhaust mixture. Unsteady exploration runs with both lean-to-rich and rich-to-lean transitions were conducted. These results were interpreted with a time scale analysis, according to which a qualitative oxygen storage model was proposed featuring the difference between oxygen absorption and desorption rates on the palladium catalysts.
2015-04-14
Journal Article
2015-01-1042
Ralf Moos
Abstract The state of catalysts and filters plays a key role in automotive exhaust gas aftertreatment. The soot or ash loading of particulate filters, the oxygen loading degree of three-way catalysts, the amount of stored ammonia in SCR catalysts, or the NOx loading degree in NOx storage catalysts are important parameters. Today, they are determined indirectly and/or model-based, calibrated by gas sensors installed up- or downstream of the catalysts or by a differential pressure sensor. This contribution overviews a novel approach to determine directly the catalyst state by a microwave-based technique. For that purpose, the catalyst housing serves as a cavity resonator. As “sensing” element, one or two simple antennas are mounted in the catalyst canning. The electrical properties of the catalyst device, i.e., of the ceramic honeycomb incl. coating and storage material, can be measured.
2015-04-14
Technical Paper
2015-01-1038
Jinbiao Ning, Fengjun Yan
Abstract Using urea-based Selected Catalytic Reduction (SCR) systems is an effective way in diesel engine after-treatment systems to meet increasingly stringent emission regulations. The amount of urea injection is critical to achieve high NOx reduction efficiency and low ammonia slip and overdosing or under-dosing of urea injection need to be avoided. One of the difficulties in urea injection amount control lies in the accurate measurement/estimation of the urea injection mass. To effectively address this issue, this paper defined a correction factor for under-dosing or overdosing detection and correction and proposed two methods to identify the correction factor. The first method is based on urea pump model and line pressure. Through frequency analysis, the relation between the urea pump speed and power spectrum characteristics of the line pressure by using FFT method was revealed.
2015-04-14
Journal Article
2015-01-1017
Yuki Jin, Narimasa Shinoda, Yosuke Uesaka, Tatsuyuki Kuki, Masataka Yamashita, Hirofumi Sakamoto, Tasuku Matsumoto, Philipp Kattouah, Claus Dieter Vogt
Abstract Since the implementation of Euro 6 in September 2014, diesel engines are facing another drastic reduction of NOx emission limits from 180 to only 80 mg/km during NEDC and real driving emissions (RDE) are going to be monitored until limit values are enforced from September 2017. Considering also long term CO2 targets of 95 g/km beyond 2020, diesel engines must become cleaner and more efficient. However, there is a tradeoff between NOx and CO2 and, naturally, engine developers choose lower CO2 because NOx can be reduced by additional devices such as EGR or a catalytic converter. Lower CO2 engine calibration, unfortunately, leads to lower exhaust gas temperatures, which delays the activation of the catalytic converter. In order to overcome both problems, higher NOx engine out emission and lower exhaust gas temperatures, new aftertreatment systems will incorporate close-coupled DeNOx systems.
2015-04-14
Journal Article
2015-01-1004
Joseph R. Theis, Jeong Kim, Giovanni Cavataio
Abstract A laboratory study was performed to assess the potential capability of passive TWC+SCR systems to satisfy the Tier 2, Bin 2 emission standards for lean-burn gasoline applications. In this system, the TWC generates the NH3 for the SCR catalyst from the feedgas NOx during rich operation. Therefore, this approach benefits from high feedgas NOx during rich operation to generate high levels of NH3 quickly and low feedgas NOx during lean operation for a low rate of NH3 consumption. It was assumed that the exhaust system needed to include a close-coupled (CC) TWC, an underbody (U/B) TWC, and an U/B SCR converter to satisfy the emission standards during 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.
2015-04-14
Journal Article
2015-01-1006
Joseph R. Theis, Jeong Kim, Giovanni Cavataio
Abstract 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.
2015-04-14
Journal Article
2015-01-0998
Paul Mentink, Rob van den Nieuwenhof, Frank Kupper, Frank Willems, Dennis Kooijman
Abstract Heavy-duty diesel engines are used in different application areas, like long-haul, city distribution, dump truck and building and construction industry. For these wide variety of areas, the engine performance needs to comply with the real-world legislation limits and should simultaneously have a low fuel consumption and good drivability. Meeting these requirements takes substantial development and calibration effort, where an optimal fuel consumption for each application is not always met in practice. TNO's Integrated Emission Management (IEM) strategy, is able to deal with these variations in operating conditions, while meeting legislation limits and obtaining on-line cost optimization. Based on the actual state of the engine and aftertreatment, optimal air-path setpoints are computed, which balances EGR and SCR usage.
2015-04-14
Journal Article
2015-01-1002
Yuichiro Murata, Tomoko Morita, Katsuji Wada, Hiroshi Ohno
Abstract A new concept for trapping NOx and HC during cold start, the NOx Trap Three-Way Catalyst (N-TWC), is proposed. N-TWC adsorbs NOx at room temperature, and upon reaching activation temperature under suitable air-fuel ratio conditions, it reduces the adsorbed NOx. This allows a reduction in NOx emissions during cold start. N-TWC's reduction mechanism relies on NOx adsorption sites which are shown to be highly dispersed palladium on acid sites in the zeolite. Testing on an actual vehicle equipped with N-TWC confirmed that N-TWC is able to reduce emissions of NOx and HC during cold start, which is a challenge for conventional TWCs.
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