Exhaust Emission Control Research Articles

Low-temperature cold-start gaseous emissions of late technology passenger cars

The control of exhaust emissions from modern vehicles is primarily based on the use of after-treatment devices, typically consisting in different types of catalysts. The efficiency of catalytic systems however strictly depends on their temperature, achieving certain effectiveness in reducing emissions only above the light-off temperature. Moreover, the enrichment of the air/fuel mixture during cold-start engine operation, in order to compensate for the reduced fuel vaporization and elevated engine components friction, leads to incomplete fuel combustion. These two factors generally contribute to elevated emissions during cold-start operation, especially under low ambient temperatures. We investigated the gaseous emission performance of thirteen late technology vehicles over the New European Driving Cycle (NEDC), at 22°C and −7°C test cell temperatures. The test fleet included gasoline vehicles both Port Fuel Injection (PFI) and Gasoline Direct Injection (G-DI) as well as diesel vehicles, amongst which a fully Euro 6 compliant vehicle equipped with a Selective Catalytic Reduction (SCR) system.The test results showed that carbon monoxide (CO) and total hydrocarbon (HC) emissions of gasoline vehicles increased from 2.3 to 11.3 times at −7°C over the Urban Driving Cycle (UDC), remaining however below the current legislative limits by 45% and 65% respectively. Nitrogen oxides (NOx) emissions of gasoline vehicles at −7°C turned out to be either higher or lower than at 22°C, depending on the catalyst’s performance and engine injection strategy. Diesel vehicles without any NOx after-treatment system exhibited increased NOx emissions over both the UDC and Extra Urban Driving Cycle (EUDC) when tested at −7°C. The diesel car with the SCR system showed superior NOx performance only over the second half of the NEDC.

Bench Scale Experiments of Diesel Soot Oxidation Using Pr0.7Sr0.2K0.1MnO3 Perovskite Type Catalyst Coated on Ceramic Foam Filters

Potassium and strontium substituted praseodymium manganate type perovskite catalyst coated on ceramic foam filters have been studied for diesel particulate removal. The synthesized catalyst coated filter pieces have been characterized by using XRD, SEM and TG analysis, whereas their catalytic activity towards soot oxidation was tested using a bench scale facility with real diesel engine exhaust. The catalyst coated filters decrease the soot oxidation Tinitial value by 150 °C and Tfinal by 100 °C as compared to bare soot oxidation reaction, which can be considered as high activity under the actual conditions of diesel engine. The catalytic materials show good thermal stability, while their low cost will also add to their potential for practical applications. Although perovskites have been studied for laboratory evaluations of catalytic soot oxidation, present results further substantiate the possibility of using low-cost, supported, non-noble metal based catalysts for diesel exhaust emission control applications, especially for the cost-effective retrofitment of in-use vehicles with old generation engines.

Local Environment and Nature of Cu Active Sites in Zeolite-Based Catalysts for the Selective Catalytic Reduction of NOx

Cu-exchanged zeolites have demonstrated widespread use as catalyst materials in the abatement of NOx, especially from mobile sources. Recent studies focusing on Cu-exchanged zeolites with the CHA structure have demonstrated them to be excellent catalysts in the ammonia-assisted selective catalytic reduction (NH3-SCR) of NOx. Thorough characterization of these materials using state-of-the-art techniques has led to a significant improvement in the understanding of active sites present, which contributes toward a fundamental understanding of the catalytic processes and the rational design of new materials; however, the availability of multiple techniques at our disposal has led to various observations and conclusions on the nature of the active sites. This article begins with a brief introduction to exhaust emission control in the mobile sector, followed by an overview of hydrocarbon-SCR and NH3-SCR; the former technology having found common use in light duty passenger vehicles, whereas the latter are applied for medium (or heavy) duty vehicles, such as trucks and busses. This is followed by an overview of zeolite-based catalysts, especially for NH3-SCR reaction with a focus toward zeolites known to possess high activity. They include zeolites Y (FAU framework), ZSM-5 (MFI framework), SSZ-13 (CHA framework), and (briefly) zeolite Beta (BEA framework). A few common techniques used for the characterization of zeolites and the information that they bring to help determine the salient structural and mechanistic aspects of the NH3-SCR process are introduced. The combination and comparison of the information obtained from the approaches have resulted in an accurate elucidation of the local geometry and environment of Cu within zeolites, thus forming the active site. The article further focuses on three main aspects: (a) the crystallographic cation location of Cu within the structures as compared to results from techniques more sensitive to the local environment; (b) the interaction of Cu at these sites with reactant or probe molecules, which illustrates their (potential) mobility and accessibility; and (c) the proposed active sites within the zeolites ZSM-5, Y, and SSZ-13 as evident in literature. The discussion is focused toward the influence of the zeolite structure, from both a long-range perspective and that of the local structure around the active Cu species, on the thus formed active sites and their implications toward the NH3-SCR reaction.

Nanometric Scale Investigation of Phase Transformations in Advanced Steels for Automotive Application

The current trend toward producing lighter vehicles in the automotive industry is driven by the need to conform to the new exhaust emission control regulations. This objective presents a challenge to steel manufacturers. The difficulty lies in designing new alloys with an optimum strength/formability/cost balance for the various components. Here, the key to success lies in controlling the steel microstructure and especially the phase transformations at the smallest possible scale. Among the different alloying elements, light elements such as carbon and boron are of prime importance due to their major effects on the kinetics of phase transformations. Characterization tools combining high spatial and analytical resolution such as secondary ion mass spectrometry (SIMS) and field emission gun-transmission electron microscopy (TEM) were used. In this article, the examples presented are as follows. (1) Boron segregation and precipitation effects to control hardenability in martensitic steels. (2) Local carbon distribution in advanced high-strength steels, with a specific emphasis on martensite tempering. Links have been established between the boron and carbon distribution and the formability.

Durability/Reliability Analysis, Simulation, and Testing of a Thermal Regeneration Unit for Exhaust Emission Control Systems

Durability/Reliability Analysis, Simulation, and Testing of a Thermal Regeneration Unit for Exhaust Emission Control Systems

Conditions of NO2-production in catalyzed DPF-systems

NO2 is much more toxic than NO. Due to the use of oxidation catalysts and catalytic coatings in the exhaust gas systems in the last decades and due to the use of low sulphur fuels the average NO2-portion in exhaust gases of vehicles increases. Diesel oxidation catalysts (DOC) and Pt-containing DPF-coatings are generally used to support the regeneration of particle filters, which can be a source of strongly increased NO2-production. The present work shows some examples and summarizes the experiences in this matter elaborated at the Laboratories for IC-Engines & Exhaust Emissions Control (AFHB) of the University of Applied Sciences Biel-Bienne, Switzerland, during some research activities on engine dynamometers in the years 2010-2012. In general it can be stated: 1) with a Pt-coated catalyst (DOC), or with catalytic surface filter (CSF) there is a maximum of NO2/ NOx – ratio typically in the exhaust gas temperature range around 350 °C, 2) with higher Pt-content in the coating there is a higher potential for NO2-formation, 3) lower NO2-production appears with: higher spatial velocity, higher S-content in fuel and with DOC/DPF used and/or soot loaded, 4) in some cases of semi active regeneration systems, or with the use of RME conditions with higher NO2-rates can appear.

Frictional and heat transfer characteristics of flow in square porous tubes of wall-flow monoliths

In the 1D modeling of flow in the channels of wall-flow monoliths used in diesel particulate filters for engine exhaust emissions control, it is common to use friction coefficients and Nusselt numbers from idealized 2D/3D channel flows with zero wall flow. This practice implicitly makes the additional approximation that the actual velocity and scalar (temperature or species concentrations) profiles within the channels are little affected by nonzero wall flow. There is extensive related research in the filtration literature for the simpler geometries of circular tubes and parallel planes that exposes much more complex and interesting effects as the wall Reynolds number, Rew, increases. Here we extend these results to the 3D geometry of square channels appropriate for wall-flow monoliths. We solve for the fully developed laminar flow, and heat transfer, within long square channels with porous walls and uniform wall velocity. Results are generated for the appropriate parameter range applicable for the diesel particulate filter application which provide the corrected friction coefficients and Nusselt numbers for nonzero Rew. Furthermore, we confirm the observation, from prior work on the simpler geometries that there exists a limiting Rew beyond which there is no fully developed flow for the inlet channels (wall suction). Implications for modeling diesel particulate filters are discussed.

On-Road Measurement of Gas and Particle Phase Pollutant Emission Factors for Individual Heavy-Duty Diesel Trucks

Pollutant concentrations in the exhaust plumes of individual diesel trucks were measured at high time resolution in a highway tunnel in Oakland, CA, during July 2010. Emission factors for individual trucks were calculated using a carbon balance method, in which pollutants measured in each exhaust plume were normalized to measured concentrations of carbon dioxide. Pollutants considered here include nitric oxide, nitrogen dioxide (NO(2)), carbon monoxide, formaldehyde, ethene, and black carbon (BC), as well as optical properties of emitted particles. Fleet-average emission factors for oxides of nitrogen (NO(x)) and BC respectively decreased 30 ± 6 and 37 ± 10% relative to levels measured at the same location in 2006, whereas a 34 ± 18% increase in the average NO(2) emission factor was observed. Emissions distributions for all species were skewed with a small fraction of trucks contributing disproportionately to total emissions. For example, the dirtiest 10% of trucks emitted half of total NO(2) and BC emissions. Emission rates for NO(2) were found to be anticorrelated with all other species considered here, likely due to the use of catalyzed diesel particle filters to help control exhaust emissions. Absorption and scattering cross-section emission factors were used to calculate the aerosol single scattering albedo (SSA, at 532 nm) for individual truck exhaust plumes, which averaged 0.14 ± 0.03.

Exhaust emissions control and engine parameters optimization using artificial neural network virtual sensors for a hydrogen-powered vehicle

This paper presents an alternative tool for vehicle tuning applications by incorporating the use of artificial neural network (ANN) virtual sensors for a hydrogen-powered car. The objective of this study is to optimize simple engine process parameters to regulate the exhaust emissions. The engine process parameters (throttle position, lambda, ignition advance and injection angle) and the exhaust emission variables (CO, CO2, HC and NOx) form the basis of the virtual sensors. Experimental data were first obtained through a comprehensive experimental and tuning procedure for neural network training and validation. The optimization layer-by-layer neural network was used to construct two ANN virtual sensors; the engine and emissions models. The performance and accuracy of the proposed virtual sensors were found to be acceptable with the maximum predictive mean relative errors of 0.65%. With its accurate predictive capability, the virtual sensors were then employed and simulated as a measurement tool for vehicle tuning and optimization. Simulation results showed that the exhaust emissions can be regulated by optimizing simple engine process parameters. This study presents an alternative tool for vehicle tuning applications for a hydrogen-powered vehicle. In addition, this work also provided a tool to better understand the effects of various engine conditions on the exhaust emissions without the need for any vehicle modifications.

Size-Resolved Polycyclic Aromatic Hydrocarbon Emission Factors from On-Road Gasoline and Diesel Vehicles: Temperature Effect on the Nuclei-Mode

Motor vehicles are a major source of polycyclic aromatic hydrocarbon (PAH) emissions in urban areas. Motor vehicle emission control strategies have included improvements in engine design, exhaust emission control, and fuel reformulation. Therefore, an updated assessment of the effects of the shifts in fuels and vehicle technologies on PAH vehicular emission factors (EFs) is needed. We have evaluated the effects of ambient temperature on the size-resolved EFs of nine US EPA Priority Pollutant PAH, down to 10 nm diameter, from on-road California gasoline light-duty vehicles with spark ignition (SI) and heavy-duty diesels with compression ignition (CI) in summer 2004 and winter 2005. During the winter, for the target PAH with the lowest subcooled equilibrium vapor pressure --benzo[a]pyrene, benzo[ghi]perylene, and indeno[1,2,3-cd]pyrene-- the mass in the nucleation mode, defined here as particles with dp <32 nm, ranged between 14 and 38% for SI vehicles and 29 and 64% for CI vehicles. Our observations of the effect of temperature on the mass of PAH in the nucleation mode are similar to the observed effect of temperature on the number concentration of diesel exhaust particles in the nucleation mode in a previous report.

Control of Exhaust Emissions from Copper Coated Gasohol Run Two Stroke Spark Ignition Engine with Catalytic Converter

The major pollutants emitted from spark ignition (SI) engine are carbon mono oxide (CO) and un-burnt hydrocarbons (UBHC). If the engine is run with alcohol, aldehydes have to be checked also. These are hazardous and cause health problems to human beings but also have impact on environment. Hence control of these pollutants call for immediate attention. Copper of thickness 300 microns is coated over piston crown, and indie portion of cylinder liner and cylinder head of the spark ignition engine. Investigations have been carried out for controlling pollutants from two strokes, 2.2 kW brake power at the rated speed of 3000 rpm, copper coated spark ignition engine fitted with catalytic converter with different catalysts such as sponge iron and manganese ore run with gasohol (blend of 20% ethanol and 80% gasoline by volume). The influence of parameters of catalytic converter (such as void ratio, mass of catalyst, airflow rate, temperature of injected air) and parameters of engine (such as brake power and equivalence ratio) on these emissions are studied. A microprocessor-based analyzer is used for the measurement of CO/UBHC in the exhaust of the engine. Aldehydes are measured by DNPH (dinitrophenyl hydrazine) method. Catalytic parameters are found to show strong influence on reduction of the pollutants in the exhaust. Copper coated spark ignition engine (CCE) with gasohol operation reduced the exhaust emissions considerably when compared to conventional engine (CE) with pure gasoline operation.

Nanotechnology for Pollution Reduction

Abstract Nanotechnology is regarded as the next great scientific/industrial revolution due to the possibility of designing nanostructured materials that possess novel electronic, optical, magnetic, and catalytic properties. Nanomaterials could potentially be applied in pollution control, catalysis, water remediation, clean energy. Nanocatalysis is a phenomenon of significant research and important practical applications in a variety of fields such as materials, environmental and atmospheric sciences. Low-temperature catalytic oxidation of carbon monoxide (CO) is one of the most important problems in pollution since even small exposures to CO (ppm) can be lethal. Nanophase metal and metal oxide catalysts, with controlled particle size, high surface area, and more densely populated unsaturated surface coordination sites, could potentially provide significantly improved catalytic performance over conventional catalysts. It is therefore, expected that nanoparticle catalysts would show high catalytic activity for the low temperature oxidation of CO than bulk materials. Noble metals are well known oxidation catalysts with high activity and stability, even in the presence of moisture and sulfur compounds, and they are usually used in gas exhaust emissions control. The high cost of precious metals and their sensitivity to sulfur poisoning motivated re-searchers to search for new catalysts. Alloying is a phenomenon that can either improve the catalytic properties of the original single-metal catalysts for CO oxidation. Recently, we reported the effect of support on the catatalytic activity of Au catalyst. We have prepared metallic and bimetallic nanocatalysts on different supports using differ-ent synthesis methods. The catalytic activity of each catalyst was carried out by using a flow tube reactor coupled to an infrared detector. Our results indicate that unsupported AuCu alloy shows higher activity than Au or Cu alone. These results attributed to the formation of CuO within the bimetallic nanoparticles, which improves the catalytic activity of Au-Cu alloy nanoparticle. On the other hand, Au nanoparticles supported on CeO2 exhibit higher catalytic activity than Cu, CuO, and AuCu alloy supported on CeO2. These results attributed to the strong interaction of Au with CeO2.

Gold Catalysts, Along with Catalyzed HC Traps: Low Temperature Exhaust Emission Control

The demand of stringent environmental laws on exhaust emission and the manufacturers' growing desire to cut down the total cost of the catalytic converter by employing lesser amounts of precious elements, needs for the development of improved catalytic exhaust treatment devices. Till now the converters in practice consist of Pt group metals as catalysts, which inherently have very high light-off temperatures for CO oxidation, around 150°C to 300®C [1], which in turn is the major pollutant of the exhaust emissions. This is where Au particles exhibit their importance, accounting to their inherent property to stimulate the oxidation reactions at even below room temperature. This article discusses the exhaust treatment device developed by Moroz et al., with Au nanoparticles as the prime component and explains why it is better than the other patented methods used for the purpose. Brief comparisons are made between these patents. Also discussed are the factors stimulating low temperature CO oxidation on Au catalyst, the reaction mechanism and how it is different from that on Pt group metals, and the use of catalysed HC trap to reduce the HC inhibition of catalytic activity.

Control of noise and exhaust emissions from dual fuel engines

An experimental investigation has been carried out to examine the effects of adding water vapor to the intake air of a dual fuel engine on the performance, combustion noise, and emission of CO, HC gases, and smoke opacity. Dual fuel engine is a diesel engine using a small amount (5%) of liquid diesel fuel as a pilot fuel and burns a liquefied petroleum gas as the main fuel. The addition of water vapor to the combustion chamber of a diesel engine has known effects on reducing the dangerous emission of nitrogen oxides. Yet it is not currently clear for the dual fuel engine how much the sacrifice is of engine performance, noise, and other exhaust emissions. Experimental procedures conducted using a Ricardo diesel version variable compression research engine are discussed. Results from testing dual fuel engine with varying the added water vapor to fuel ratios and other design and operating parameters are presented and discussed. The addition of water vapor to the intake air affected the performance, combustion noise, and exhaust emissions.

Impact of Oxygen Enriched Air Intake on the Exhaust of a Single Cylinder Diesel Engine

Problem statement: The objective of the research is to investigate the effect of using oxygen enriched air on Diesel engine exhaust emission. Approach: In the present experimental work a computerized Single cylinder Diesel engine with data acquisition system was used to study the effects of oxygen enriched air intake on Exhaust emissions. Engine test has been carried out in the above said engine for different loads and Exhaust Emissions like CO, CO2, NOx and HC with respect to different percentage of oxygen enrichment were discussed. Results and Conclusion: Increasing the oxygen content with the air leads to faster burn rates and the ability to control Exhaust Emissions. Added oxygen in the combustion air offers more potential for burning diesel. Oxy-fuel combustion reduces the volume of flue gases and reduces the effects of green house effect also.

The new generation of the Audi 3.0 L V6 TDI engine

The new 3.0 I V6 TDI engine with four valves per cylinder, piezo injectors, common rail fuel injection system, turbocharging with variable turbine geometry (VTG), swirl action control and dual coolant circuit with intelligent thermal management and integrated exhaust gas recirculation (EGR) cooling develops — depending on the intended application — between 150 kW and 184 kW and has a maximum torque of between 400 Nm and 550 Nm. It complies with Euro 5 exhaust emission limits and has very low CO2 emissions. In the following thermodynamics, application and exhaust emission control of the new engine are described. The first part of the article in MTZ 10 already depicted the design and the mechanics of the new engine.

Preparation and characterization of catalytic thin films for exhaust emission control

In this study, we explored the possibility of the preparation of a catalytic system for reduction of nitrogen oxides based on alumina and zirconia thin films electrochemically deposited on stainless steel, silver being chosen as an active phase. The composition and structure of the Ag loaded Al2O3/SS and ZrO2/SS films were characterized by SEM, XPS, and XRD. It was established that the electrochemical deposition leads to the formation of an active phase of isolated particles of metal silver with a mean size of several μm. The catalysts were tested in the reaction of selective catalytic reduction of NO x with C8H18 in an excess of oxygen. A higher catalytic activity was found with Ag/ZrO2/SS, the optimum working temperature for both samples being 380 °C.

Application of Rare Earth Modified Zr-based Ceria-Zirconia Solid Solution in Three-Way Catalyst for Automotive Emission Control

Automotive exhaust emission is a major cause of air pollution. Three-way catalyst (TWC) which can eliminate CO, HC (hydrocarbons), and NO(x) simultaneously has been used to control exhaust emissions. Ceria-zirconia is a key component in TWC and most researchers pay attention to Ceria-Zirconia (Ce-rich) solid solution. The research presented in this paper is focused on the intrinsic structure of Ceria-Zirconia (Zr-based) solid solution and its application in TWC. A series of Ce(0.2)Zr(0.8)O(2) modified with rare earths (La, Nd, Pr, Sm, and Y) have been prepared by coprecipitation method combined with supercritical drying technique. All samples showed single tetragonal solid solution, indicating that the rare earth ion inserted into the lattice structure completely, and an approximately linearly relationship between lattice parameter a and the ionic radius of doped rare earth was observed. The catalytic performances of corresponding Pd-only catalysts were investigated in simulated exhaust gas. The presence of La, Nd, and Pr was favorable to the catalytic activity and wide air/fuel operation window. The relationship between the intrinsic structure of the Zr-based ceria-zirconia solid solution and catalytic activity was discussed in detail, which has some reference value for catalyst design and application.

Transport impacts on atmosphere and climate: Land transport

Emissions from land transport, and from road transport in particular, have significant impacts on the atmosphere and on climate change. This assessment gives an overview of past, present and future emissions from land transport, of their impacts on the atmospheric composition and air quality, on human health and climate change and on options for mitigation. In the past vehicle exhaust emission control has successfully reduced emissions of nitrogen oxides, carbon monoxide, volatile organic compounds and particulate matter. This contributed to improved air quality and reduced health impacts in industrialised countries. In developing countries however, pollutant emissions have been growing strongly, adversely affecting many populations. In addition, ozone and particulate matter change the radiative balance and hence contribute to global warming on shorter time scales. Latest knowledge on the magnitude of land transport's impact on global warming is reviewed here. In the future, road transport's emissions of these pollutants are expected to stagnate and then decrease globally. This will then help to improve the air quality notably in developing countries. On the contrary, emissions of carbon dioxide and of halocarbons from mobile air conditioners have been globally increasing and are further expected to grow. Consequently, road transport's impact on climate is gaining in importance. The expected efficiency improvements of vehicles and the introduction of biofuels will not be sufficient to offset the expected strong growth in both, passenger and freight transportation. Technical measures could offer a significant reduction potential, but strong interventions would be needed as markets do not initiate the necessary changes. Further reductions would need a resolute expansion of low-carbon fuels, a tripling of vehicle fuel efficiency and a stagnation in absolute transport volumes. Land transport will remain a key sector in climate change mitigation during the next decades.

NOx Trap Catalyst Technologies and Exhaust Emission Control to Expand Lean Burn Operation for Gasoline Engine Application

NOx Trap Catalyst Technologies and Exhaust Emission Control to Expand Lean Burn Operation for Gasoline Engine Application