Criteria

Text:
Topic:
Display:

Results

Viewing 241 to 270 of 21945
2017-03-28
Technical Paper
2017-01-0992
Dereck Dasrath, Richard Frazee, Jeffrey Hwang, William Northrop
Abstract Partially premixed low temperature combustion (LTC) in diesel engines is a strategy for reducing soot and NOX formation, though it is accompanied by higher unburned hydrocarbon (UHC) emissions compared to conventional mixing-controlled diesel combustion. In this work, two independent methods of quantifying light UHC species from a diesel engine operating in early LTC (ELTC) modes were compared: Fourier transform infrared (FT-IR) spectroscopy and gas chromatography-mass spectroscopy (GC-MS). A sampling system was designed to capture and transfer exhaust samples for off-line GC-MS analysis, while the FT-IR sampled and quantified engine exhaust in real time. Three different ELTC modes with varying levels of exhaust gas recirculation (EGR) were implemented on a modern light-duty diesel engine. GC-MS and FT-IR concentrations were within 10 % for C2H2, C2H4, C2H6, and C2H4O. While C3H8 was identified and quantified by the FT-IR, it was not detected by the GCMS.
2017-03-28
Journal Article
2017-01-0994
Tim Nevius, Dario Rauker, Masanobu Akita, Yoshinori Otsuki, Scott Porter, Michael Akard
Abstract Direct measurement of dilution air volume in a Constant Volume emission sampling system may be used to calculate tailpipe exhaust volume, and the total dilution ratio in the CVS. A Remote Mixing Tee (RMT) often includes a subsonic venturi (SSV) flowmeter in series with the dilution air duct. The venturi meter results in a flow restriction and significant pressure drop in the dilution air pipe. An ultrasonic flow meter for a similar dilution air volume offers little flow restriction and negligible pressure drop in the air duct. In this investigation, an ultrasonic flow meter (UFM) replaces the subsonic venturi in a Remote Mixing Tee. The measurement uncertainty and accuracy of the UFM is determined by comparing the real time flow rates and integrated total dilution air volume from the UFM and the dilution air SSV in the RMT. Vehicle tests include FTP and NEDC test cycles with a 3.8L V6 reference vehicle.
2017-03-28
Journal Article
2017-01-0990
Carl Paulina, Dan McBryde, Mike Matthews
Abstract Track Road Load Derivations (RLDs) and subsequent load matching on test cell dynamometers has traditionally been conducted using vehicle coastdowns (CDs). Vehicle speed changes during these coastdowns are used to calculate the vehicle mechanical drag forces slowing vehicles when on the road. Track drag force, exerted on a vehicle, can also be quantified by holding a vehicle at a specific steady state speed and measuring the forces required to maintain that speed. This paper focuses on two methods to quantify speed dependent forces which a vehicle must work against when motoring. One method is the traditional coastdown method. The second reference method measures vehicle steady state speed forces necessary to propel the vehicle using both electric vehicle propulsion power flows and dynamometer measured forces. Track CDs require the vehicle to be placed in neutral.
2017-03-28
Technical Paper
2017-01-0991
Sunil Kumar Pathak, Yograj Singh, Vineet sood, Salim Abbasbhai Channiwala
Abstract Vehicles are tested in controlled and relatively narrow laboratory conditions to determine their type approval emission values and reference fuel consumption. Some studies have shown that real world driving emissions are much higher as compared to laboratory measurements. The difference was caused by two important factors, i.e. ambient conditions (temperature and altitude) and actual real-world driving cycles. For this reason, the European Commission had constituted a working group which developed a complementary Real-Driving Emissions (RDE) test procedure using the Portable Emissions Measurement Systems (PEMS). RDE test will verify gaseous pollutant and particle number emissions during a wide range of normal operating conditions on the road. In RDE test specific boundary conditions of the temperatures, classified as moderate (0 ≤Tamb < 30), Extended (low): -7 ≤Tamb < 0 and Extended (high): 30
2017-03-28
Technical Paper
2017-01-0997
Roberto Aliandro Varella, Gonçalo Duarte, Patricia Baptista, Luis Sousa, Pablo Mendoza Villafuerte
Abstract The gap between regulated emissions from vehicle certification procedures and real-world driving has become increasingly wider, particularly for nitrogen oxides (NOx). Even though stricter emission regulations have been implemented, NOx emissions are dependent on specific, short-duration driving events which are difficult to control, therefore high concentrations of these pollutants are still being measured in European cities. Under certification procedures, vehicle emissions compliance is evaluated through standards, recurring to driving cycles performed on chassis dynamometer under controlled laboratory conditions. Different countries use different standard cycles, with the US basing their certification cycle on FTP-75 and Europe using NEDC (Euro 5/6c)/WLTP (Euro 6d).
2017-03-28
Technical Paper
2017-01-0998
Kurtis James Irwin, Jonathan Stewart, Roy Douglas, Andrew Woods, Richard O’Shaughnessy, Andrew Pedlow, Rose Mary Stalker
Abstract Accelerated aging of automotive catalysts has become a routine process for the development of new catalytic formulations and for homologation of vehicle emissions. In the standard approach, catalyst samples are subjected to temperatures in excess of 800°C on a predefined test cycle and aged for precise timescales representative of certain vehicle mileage. The high temperature feed gas is traditionally provided by a large gasoline engine but, increasingly, alternative bench-aging techniques are being applied as these offer more precise control and considerable cost savings, as well as offering more development possibilities. In the past few years, emissions control of light duty vehicles has become increasingly prominent as more stringent emissions legislations require more complex after-treatment systems. Aging of the catalysts are not fully understood as they are subjected to many varying environments, including temperature and gas concentrations.
2017-03-28
Journal Article
2017-01-0995
Olle Berg, Lars-Gunnar Simonson
Abstract The Constant Volume Sampler (CVS) is often used to dilute automotive exhaust with ambient air for measurement of emissions from light duty vehicles. A CVS is traditionally equipped with Critical Flow Venturi (CFV) to control and measure total flow. If the CVS is equipped with a Smooth Approach Orifice (SAO) to measure dilution air flow, the exhaust flow of the vehicle can be calculated as the difference between dilution and total flow. Calibration of the CVS and SAO is routinely done using ambient air, but carbon dioxide (CO2) and water vapor in diluted exhaust have an influence on the flow through the CFV. In current US emission legislation the provisions to include water vapor is added. However, if this is done then the effect of carbon dioxide (CO2) in exhaust has not been considered. Further on, when using the CVS to measure exhaust flow, only the CFV will be affected by the diluted exhaust gas composition.
2017-03-28
Journal Article
2017-01-0996
Sebastian Gramstat, André Cserhati, Matthias Schroeder, Dmytro Lugovyy
Abstract Brake Particle Emission (BPE) is gaining considerable importance for the friction brake and automotive industry. So far no common approach or legislation for BPE characterization exists although many activities in this field have been started during the last years. Taking this into account, the authors carried out a joint measurement campaign to investigate a new approach regarding the sampling location using a brake dynamometer. During preliminary investigations the influence of the cooling air quality has been examined and a sampling point position validation has been carried out. At first the stabilization behavior for repeated test cycles and variations of volumetric air flow rates are analyzed. As a next step the role of volatile particle emissions is determined. Subsequently, the influence of load history and friction power is studied. Finally results in terms of the role of high temperature applications are presented.
2017-03-28
Technical Paper
2017-01-1001
Seyoung Kim, Kenji Kondo, Yoshinori Otsuki, Kazuhiko Haruta
Abstract An on-board solid particle number (PN) analyzer (OBS-ONE-PN) has been developed to measure PN concentrations in engine exhaust under real-driving conditions. Specification of OBS-ONE-PN is based on the recommendation in PEMS-PN draft. OBS-ONE-PN consists of primary diluter, heated transfer tube, heated catalytic stripper (CS), secondary dilutor and particle detector. Volatile fractions which is emitted from the automobile engine are removed by CS, and then only solid particles are counted by a condensation particle counter (CPC). Finally, the system provides results in number concentration. The detailed specifications relating to the OBS-ONE-PN performance such as dilution factor accuracy, volatile particle removal efficiency, overall detection efficiency and durability test results are described in this paper The OBS-ONE-PN is used to characterize PN emission from a gasoline vehicle.
2017-03-28
Technical Paper
2017-01-1002
Daisuke Tanaka, Ryo Uchida, Toru Noda, Andreas Kolbeck, Sebastian Henkel, Yannis Hardalupas, Alexander Taylor, Allen Aradi
Abstract The purpose of this work was to gain a fundamental understanding of which fuel property parameters are responsible for particulate emission characteristics, associated with key intermediate behavior in the engine cylinder such as the fuel film and insufficient mixing. Accordingly, engine tests were carried out using various fuels having different volatility and chemical compositions under different coolant temperature conditions. In addition, a fundamental spray and film visualization analysis was also conducted using a constant volume vessel, assuming the engine test conditions. As for the physical effects, the test results showed that a low volatility fuel displayed high particulate number (PN) emissions when the injection timing was advanced. The fundamental test clearly showed that the amount of fuel film on the impingement plate increased under such operating conditions with a low volatility fuel.
2017-03-28
Technical Paper
2017-01-0999
Yuanzhou Xi, Nathan Ottinger, Z. Gerald Liu
Abstract Natural gas powered vehicles are attractive in certain applications due to their lower emissions in general than conventional diesel engines and the low cost of natural gas. For stoichiometric natural gas engines, the aftertreatment system typically consists only of a three-way catalyst (TWC). However, increasingly stringent NOx and methane regulations challenge current TWC technologies. In this work, a catalyst reactor system with variable lean/rich switching capability was developed for evaluating TWCs for stoichiometric natural gas engines. The effect of varying frequency and duty-cycle during lean/rich gas switching experiments was measured with a hot-wire anemometer (HWA) due to its high sensitivity to gas thermal properties. A theoretical reactor gas dispersion model was then developed and validated with the HWA measurements. The model is capable of predicting the actual lean/rich gas exposure to the TWC under different testing conditions.
2017-03-28
Technical Paper
2017-01-1000
Jong Lee, Yu Zhang, Tom Tzanetakis, Michael Traver, Melanie Moses-DeBusk, John Storey, William Partridge, Michael Lance
Abstract Greenhouse gas regulations and global economic growth are expected to drive a future demand shift towards diesel fuel in the transportation sector. This may create a market opportunity for cost-effective fuels in the light distillate range if they can be burned as efficiently and cleanly as diesel fuel. In this study, the emission performance of a low cetane number, low research octane number naphtha (CN 34, RON 56) was examined on a production 6-cylinder heavy-duty on-highway truck engine and aftertreatment system. Using only production hardware, both the engine-out and tailpipe emissions were examined during the heavy-duty emission testing cycles using naphtha and ultra-low-sulfur diesel (ULSD) fuels. Without any modifications to the hardware and software, the tailpipe emissions were comparable when using either naphtha or ULSD on the heavy duty test cycles.
2017-03-28
Journal Article
2017-01-1005
Yizhou Zhang, Jaal Ghandhi, David Rothamer
Abstract The effect of direct-injected fuel on particle size distributions (PSDs) of particulate matter emitted from dual-fuel combustion strategies was investigated. The PSD data were acquired from a light-duty single-cylinder diesel engine operated using conventional diesel combustion (CDC) and two diesel/natural gas dual-fuel combustion strategies. Three different direct-injection (DI) fuels (diesel, 2,6,10-trimethyldodecane, and a primary reference fuel blend) and two different injector nozzles were studied. The DI fuels were chosen to have similar energy and ignition characteristics (heat of combustion and cetane number) but different physical and chemical properties (volatility, aromatics %, viscosity, density). The two nozzles (with different orifice diameter and spray angle) allowed a wide range in DI fuel quantity for the dual-fuel combustion strategies.
2017-03-28
Technical Paper
2017-01-1003
Ye Liu, Gang Lv, Chenyang Fan, Na Li, Xiaowei Wang
Abstract The evolution of surface functional groups (SFGs) and the graphitization degree of soot generated in premixed methane flames are studied and the correlation between them is discussed. Test soot samples were obtained from an optimized thermophoretic sampling system and probe sampling system. The SFGs of soot were determined by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) after removing the soluble impurities from the soot samples, while the graphitization degree of soot was characterized by Raman spectrum and electron energy loss spectroscopy (EELS). The results reveal that the number of aliphatic C-H groups and C=O groups shows an initial increase and then decrease in the sooting history. The large amount of aliphatic C-H groups and small amount of aromatic C-H groups in the early stage of the soot mass growth process indicate that aliphatic C-H groups make a major contribution to the early stage of soot mass growth.
2017-03-28
Technical Paper
2017-01-1006
Fadzli Ibrahim, Wan Mohd Faizal Wan Mahmood, Shahrir Abdullah, Mohd Radzi Abu Mansor
Abstract Application of computational method in studying soot formation and its characteristics has become more preferable in today’s automotive field. Current developments of computer programs with higher precision mathematical models enable simulation results to become closer to the real engine combustion phenomena. In the present study, investigation on soot has been performed using various soot models with different levels of complexity, from simple two-step Hiroyasu-NSC soot model to the detailed-kinetic soot model. Detailed soot models, Particulate Mimic (PM) which is based on methods of moment and Particulate Size Mimic (PSM) which is based on sectional method, are applied in this study. Result of soot mass from Hiroyasu-NSC model provides 120% error compare to experimental result, while both detailed models provide an acceptable error of 7%.
2017-03-28
Technical Paper
2017-01-1004
Jan Czerwinski, Pierre Comte, Norbert Heeb, Andreas Mayer, Volker Hensel
Abstract In the present paper some results of investigations of nanoparticles from five DI gasoline cars are represented. The measurements were performed at vehicle tailpipe and in CVS-tunnel. Moreover, five variants of “vehicle - GPF” were investigated. These results originate from the project GasOMeP (Gasoline Organic & Metal Particulates), which focused on metal-nanoparticles (including sub 20nm) from gasoline cars with different engine technologies. The PN-emission level of the investigated GDI cars in WLTC without GPF is in the same range of magnitude very near to the actual limit value of 6.0 × 1012 #/km. With the GPF’s with better filtration quality, it is possible to lower the emissions below the future limit value of 6.0 × 1011 #/km. There is no visible nuclei mode and the ultrafine particle concentrations below 10mm are insignificant. Some of the vehicles show at constant speed operation a periodical fluctuation of the NP-emissions, as an effect of the electronic control.
2017-03-28
Journal Article
2017-01-0911
Krishna Chilumukuru, Aniket Gupta, Michael Ruth, Michael Cunningham, Govindarajan Kothandaraman, Lasitha Cumaranatunge, Howard Hess
Abstract Future light duty vehicles in the United States are required to be certified on the FTP-75 cycle to meet Tier 3 or LEV III emission standards [1, 2]. The cold phase of this cycle is heavily weighted and mitigation of emissions during this phase is crucial to meet the low tail pipe emission targets [3, 4]. In this work, a novel aftertreatment architecture and controls to improve Nitrogen Oxides (NOx) and Hydrocarbon (HC) or Non Methane Organic gases (NMOG) conversion efficiencies at low temperatures is proposed. This includes a passive NOx & HC adsorber, termed the diesel Cold Start Concept (dCSC™) catalyst, followed by a Selective Catalytic Reduction catalyst on Filter (SCRF®) and an under-floor Selective Catalytic Reduction catalyst (SCR). The system utilizes a gaseous ammonia delivery system capable of dosing at two locations to maximize NOx conversion and minimize parasitic ammonia oxidation and ammonia slip.
2017-03-28
Technical Paper
2017-01-0912
Joel Op de Beeck, Scott Mccleary, Joshua Butler, Issam Djemili, Mihai Baja
Abstract Automotive SCR systems for diesel NOx reduction are dimensioned to reduce NOx efficiently in all driving conditions. In this regard the DEF storage and delivery system is developed to operate in a full range of temperatures, voltages, pressures, etc. To allow a control for optimal performance, sensors are added in the system (temperature, level, pressure sensor). Recently, a DEF quality sensor has been added to assure the correct concentration of urea in water in the onboard DEF tank. Now the question is raised how to assure that the DEF quality sensor is operating correctly and is giving an accurate indication of the liquid in the tank. The objective of this study is to define an independent method (PQD) to verify liquid quality, and challenge the signal generated by the DEF quality sensor. This study describes a possible method and the progress on its validation in various automotive driving conditions.
2017-03-28
Technical Paper
2017-01-0913
Evangelos Georgiadis, Toru Kudo, Olaf Herrmann, Ken Uchiyama, Juergen Hagen
Abstract In order to comply with emission regulation, reach their profitability targets and minimise the in-use cost of their vehicles, OEMs are seeking solutions to optimise their aftertreatment systems. For Selective Catalytic Reduction (SCR) system engineers, one of the most important challenges is to reduce the system's cost, while keeping its high level of NOx emission reduction performance. Ways to achieve this cost reduction include 1. using an engine out NOx estimation model instead of a NOx sensor upstream of the SDPF (DPF coated with SCR) catalyst and 2. eliminating the Ammonia Slip Catalyst (ASC) downstream of the SDPF catalyst. Achieving these challenging targets requires actions on the complete SCR system, from the optimisation of mixing and uniformity in the SDPF catalyst to the development of robust controls. To face these challenges, a novel exhaust reverse flow concept with a blade mixer was developed.
2017-03-28
Technical Paper
2017-01-0914
Mengchao Zhang
Abstract Since diesel engines have higher thermal efficiency, superior power capability and better fuel economy than gasoline engines, diesel engines are widely used in vehicles, construction machineries and agricultural machineries. However, they emit more hazardous pollutants than gasoline engines, especially particulate emissions, which have negative impacts on human’s health and air quality in cities. In order to meet future increasingly stringent regulations for particulate emissions, exhaust gas aftertreatment technologies for diesel engines are essential. Particulate emissions from a heavy-duty diesel engine which meets the China national V emission regulation were studied, and the engine was equipped with/without diesel oxidation catalyst (DOC), catalyzed diesel particulate filter (CDPF) and selective catalytic reduction (SCR). The fuel used in this article is ultra low sulfur diesel fuel whose sulfur content is less than 10 ppm.
2017-03-28
Technical Paper
2017-01-0915
Haomiao Zhang, Yuanzhou Xi, Changsheng Su, Z. Gerald Liu
Abstract Diesel exhaust fluid, DEF, (32.5 wt.% urea aqueous solution) is widely used as the NH3 source for selective catalytic reduction (SCR) of NOx in diesel aftertreatment systems. The transformation of sprayed liquid phase DEF droplets to gas phase NH3 is a complex physical and chemical process. Briefly, it experiences water vaporization, urea thermolysis/decomposition and hydrolysis. Depending on the DEF doser, decomposition reaction tube (DRT) design and operating conditions, incomplete decomposition of injected urea could lead to solid urea deposit formation in the diesel aftertreatment system. The formed deposits could lead to engine back pressure increase and DeNOx performance deterioration etc. The formed urea deposits could be further transformed to chemically more stable substances upon exposure to hot exhaust gas, therefore it is critical to understand this transformation process.
2017-03-28
Technical Paper
2017-01-0917
Go Hayashita, Motoki Ohtani, Keiichiro Aoki, Shuntaro Okazaki
Abstract Exhaust systems must satisfy a wide range of requirements, including lowering emissions to comply with future fuel economy and emissions regulations. To help meet these requirements, new emissions control systems have been developed today. In addition, since air-fuel ratio (hereafter, A/F) control has a major impact on emissions, a new two-A/F sensor system with A/F sensors provided both upstream and downstream of the catalyst was developed, incorporating an A/F control capable of further lowering emissions with greater robustness. This development identified the hysteresis characteristics of the O2 sensor downstream of the catalyst as an important factor affecting emissions during conventional A/F control. Subsequently, reaction analysis was carried out using sensor reaction models and by evaluating sensors under real-world operating conditions.
2017-03-28
Journal Article
2017-01-0918
Joseph R. Theis, Andrew Getsoian, Christine Lambert
Abstract 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.
2017-03-28
Journal Article
2017-01-0919
Takeru Yoshida, Hiromasa Suzuki, Yuki Aoki, Naohiro Hayashi, Kenichi Ito
Abstract Emission regulations in many countries and regions around the world are becoming stricter in reaction to the increasing awareness of environment protections, and it has now become necessary to improve the performance of catalytic converters to achieve these goals. A catalytic converter is composed of a catalytically active material coated onto a ceramic honeycomb-structured substrate. Honeycomb substrates play the role of ensuring intimate contact between the exhaust gas and the catalyst within the substrate’s flow channels. In recent years, high-load test cycles have been introduced which require increased robustness to maintain low emissions during the wide range of load changes. Therefore, it is extremely important to increase the probability of contact between the exhaust gas and catalyst.
2017-03-28
Journal Article
2017-01-0899
Paul Dekraker, John Kargul, Andrew Moskalik, Kevin Newman, Mark Doorlag, Daniel Barba
Abstract The Environmental Protection Agency’s (EPA’s) Advanced Light-Duty Powertrain and Hybrid Analysis (ALPHA) tool was created to estimate greenhouse gas (GHG) emissions from light-duty vehicles. ALPHA is a physics-based, forward-looking, full vehicle computer simulation capable of analyzing various vehicle types with different powertrain technologies, showing realistic vehicle behavior, and auditing of internal energy flows in the model. In preparation for the midterm evaluation (MTE) of the 2017-2025 light-duty GHG emissions rule, ALPHA has been updated utilizing newly acquired data from model year 2013-2016 engines and vehicles. Simulations conducted with ALPHA provide data on the effectiveness of various GHG reduction technologies, and reveal synergies that exist between technologies. The ALPHA model has been validated against a variety of vehicles with different powertrain configurations and GHG reduction technologies.
2017-03-28
Technical Paper
2017-01-0907
Timothy Johnson, Ameya Joshi
Abstract This review paper summarizes major and representative developments in vehicle engine efficiency and emissions regulations and technologies from 2016. The paper starts with the key regulatory developments in the field, including newly proposed European RDE (real driving emissions) particle number regulations, and Euro 6 type regulations for China and India in the 2020 timeframe. China will be tightening 30-40% relative to Euro 6 in 2023. The California heavy duty (HD) low-NOx regulation is advancing and the US EPA is anticipating developing a harmonized proposal for implementation in 2023+. The US also finalized the next round of HD GHG (greenhouse gas) regulations for 2021-27, requiring 5% engine CO2 reductions. LD (light duty) and HD engine technology continues showing marked improvements in engine efficiency. Key developments are summarized for gasoline and diesel engines to meet both the emerging criteria and greenhouse gas regulations.
2017-03-28
Technical Paper
2017-01-0908
Fanxu Meng, Asanga Wijesinghe, John Colvin, Carolyn LaFleur, Richard Haut
Abstract Natural gas (NG), which consists of mostly methane, can be co-combusted with diesel fuel in existing compression ignition engines through dual fuel technology with reasonable engine modifications. The removal of short-chain alkanes (e.g. CH4, C2H6 and C3H8) of a dual fuel (natural gas and diesel) engine raises a distinctive topic to the exhaust aftertreatment system (ATS). However, there are few studies reported based on tests with real engine exhaust. This present study focuses on the conversion of short-chain alkanes by Co, Ni and Cu/ZSM-5 catalysts, which are commonly used for oxidation/partial oxidation and reforming. These catalysts are tested with exhaust of a dual-fuel (natural gas and diesel) engine. The complicated and dynamic exhaust composition, determined by the engine loading and natural gas substitution, can result in different components in the exhaust and various conversions for species.
2017-03-28
Journal Article
2017-01-0909
Zhe Zhang, Mats Abom, Hans Boden, Mikael Karlsson, David Katoshevski
Abstract Air pollution caused by exhaust particulate matter (PM) from vehicular traffic is a major health issue. Increasingly strict regulations of vehicle emission have been introduced and efforts have been put on both the suppression of particulate formation inside the engine cylinders and the development of after-treatment technologies such as filters. With modern direct injected engines that produce a large number of really small sub-micron particles, the focus has increased even further and now also includes a number count. The problem of calculating particle trajectories in flow ducts like vehicle exhaust systems is challenging but important to further improve the technology. The interaction between particles and oscillating flows may lead to the formation of particle groups (regions where the particle concentration is increased), yielding a possibility of realizing particle agglomeration.
2017-03-28
Journal Article
2017-01-0910
Michiel Makkee, Yixiao Wang
Abstract We studied the mechanism of NO reduction as well as its selectivity and reactivity in the presence of excess O2. Results show that fuel injection and/or pretreatment are important for ceria catalyst reduction and carbon deposition on the catalyst surface. Oxygen defects of reduced ceria are the key sites for the reduction of NO into N2. The deposited carbon acts as a buffer reductant, i.e., the oxidation of carbon by lattice oxygen recreates oxygen defects to extend the NO reduction time interval. A small amount of NO showed a full conversion into only N2 both on the reduced Zr-La doped ceria and reduced Pt-Zr-La doped ceria. Only when the catalyst is oxidised NO is converted into NO2.
2017-03-28
Journal Article
2017-01-0581
Stephen C. Burke, Matthew Ratcliff, Robert McCormick, Robert Rhoads, Bret Windom
Abstract In some studies, a relationship has been observed between increasing ethanol content in gasoline and increased particulate matter (PM) emissions from vehicles equipped with spark ignition engines. The fundamental cause of the PM increase seen for moderate ethanol concentrations is not well understood. Ethanol features a greater heat of vaporization (HOV) than gasoline and also influences vaporization by altering the liquid and vapor composition throughout the distillation process. A droplet vaporization model was developed to explore ethanol’s effect on the evaporation of aromatic compounds known to be PM precursors. The evolving droplet composition is modeled as a distillation process, with non-ideal interactions between oxygenates and hydrocarbons accounted for using UNIFAC group contribution theory. Predicted composition and distillation curves were validated by experiments.
Viewing 241 to 270 of 21945