Impact of Cold Climates on Vehicle Emissions: The Cold Start Air Toxics Pulse

This project measured cold start emissions from four vehicles in winter using fast response instrumentation to accurately measure the time variation of the cold start emission pulse. Seventeen successful tests were conducted over a temperature range of -4°C to 10°C in winter 2015 at the Washington State University campus. Vehicle cold starts are thought to be a significant source of air toxic compounds in cold winter environments due to the rapid increase in mass emission rates with decreasing temperature. We used a proton transfer reaction mass spectrometer for high time resolution measurement of the emissions the air toxic compounds benzene, formaldehyde, acetaldehyde, in addition to toluene and C2-alkylbenzenes. Measured molar emission ratios relative to toluene in the cold start pulse were compared with cold start emission profiles for E10 fueled vehicles used in the EPA MOVES2014 model. We found that the measured acetaldehyde-to-toluene emission ratio was about a factor of 8 greater than the emission ratio used in MOVES2014. Measured formaldehyde-to-toluene emission ratios were a factor of 5 greater. Our study suggests that emission of the air toxics acetaldehyde and, likely, formaldehyde is significantly underestimated in wintertime by the MOVES2014 model

Modeling of an automotive exhaust gas converter at low temperature aiming at control application

The LEV/ULEV emission standards pose challenging problems on automotive exhaust gas treatment. This increases the need for good catalytic converter models, which can be applied for control. A dynamic converter model was made on the basis of first principles, accounting for the accumulation of mass in the bulk gas phase, in pores of the washcoat and on the catalytic surface, as well as for the energy accumulation in the gas and solid phase. The basis for the model is the elementary step kinetics of the individual global reactions. The main purpose of the model is to describe the low temperature behavior of the converter, when the majority of the emissions occur. The light-off process is analyzed in detail with different inputs. The biggest improvement occurs when secondary air is injected in front of the converter. The converter model is also coupled with a simple SI engine model to investigate the dynamic behavior of the whole system.</p

Formation of nitrous oxide over Pt-Pd oxidation catalysts: Secondary emissions by interaction of hydrocarbons and nitric oxide

The interaction of hydrocarbons (HC) and nitric oxide (NO) over noble metal catalysts for exhaust gas after-treatment of lean-operated combustion engines can lead to secondary emissions, namely the formation of nitrous oxide (N$_2$O), which is a strong greenhouse gas calling for N$_2$O reduction concepts. By means of a series of light-off tests over state-of-the-art Pt-Pd oxidation catalysts, this study identifies the most critical catalyst operation regimes that should be avoided in order to minimize N$_2$O levels. Especially unsaturated HCs react with NO to form significant amounts of N$_2$O between 150 °C and 350 °C; an increasing HC/NOx ratio generally promotes N$_2$O formation, whereas the NO oxidation reaction is increasingly inhibited. Since low space velocities and fast catalyst heating allow for minimizing N$_2$O levels, active heating of catalytic converters during cold start and phases of low exhaust gas temperatures may efficiently reduce the formation of N$_2$O in real-world applications

Catalytic Converters for Vehicle Exhaust: Fundamental Aspects and Technology Overview for Newcomers to the Field

This works aims to provide an understanding on basic chemical kinetics pertaining to three-way catalytic (TWC) converters from an educational perspective, aimed at those novel readers in this field. Rate of reactions and its factors are explained, showcasing that the chosen catalyst is the main factor affecting the overall rate of reaction. Furthermore, this overview revisit insights of the catalytic converter structure and the environmental issues that come along with it. Lastly, the chemical and physical properties of the reactants and products-pollutant and less-toxic gases—are discussed, in order to gather a better understanding of the reactants and products that enters a catalytic converter

Transient Flow Uniformity Evolution in Realistic Exhaust Gas Aftertreatment Systems using 3D-CFD

To precisely control a vehicle powertrain to minimize emissions, accurate and detailed models are needed to capture the spatio-temporal variability of the variables of interest. The aim of this work is to analyze flow and temperature fields in a geometrically realistic —\ua0and thus complex\ua0— exhaust gas aftertreatment system under transient conditions. The spatio-temporal response of these fields to upstream step changes is predicted using three-dimensional unsteady Reynolds-averaged Navier-Stokes (URANS) κ- ω simulations where the catalytic converter is described as a porous medium. A catalytic converter geometry with a 90∘-bend and a partially dead volume is used to demonstrate the effects of time-resolved flow maldistribution on the profiles of velocity and temperature. Two sets of transient simulations in terms of step changes in velocity and temperature are performed. Uniformity indices are used to characterize the distribution and variability of the different catalyst channels under transient conditions. The evolution of the uniformity indices as functions of time and axial distance into the catalyst are calculated at different cross-sectional planes. The results show that the evolution of the temperature uniformity is rate controlling, continuously modulating the otherwise much faster flow uniformity response via the fluid properties. The temperature uniformity time scale is determined by the balance of flow, thermal inertia, and the heat losses from the system. The interplay between pressure drop and heat losses governs the transition to the new steady state in uniformity. These types of transient simulations and analyses can contribute essential information when developing reduced-order engineering models to represent the spatio-temporal variability in exhaust aftertreatment systems, in particular during rapid events such as cold start

The Market-based Lead Phasedown

The U.S. lead phasedown was effective in meeting its environmental objectives, and did so more quickly with the allowance of permit banking. The marketable lead permit system was highly costeffective, saving hundreds of millions of dollars relative to comparable policies not allowing trading or banking. Estimates suggest that transaction costs brought about only a modest reduction in program efficiency. The market-based nature of the program also provided incentives for more efficient adoption of new lead-removing technology, relative to a uniform standard. Distributionally, it is likely that the program was actually more responsive to the cost concerns of small refiners than a similar uniform standard would have been. The flexibility of the program likely increased the amount of violations, however, and added an unexpected monitoring and enforcement burden. On the other hand, one of the efficiency advantages of the incentive-based program is that it provided opportunities for unanticipated means of cost-effective compliance.lead phasedown, gasoline, tradable permit, market-based policy, technology adoption

Particulate airborne impurities

The cumulative effects of air pollutants are of principal concern in research on environmental protection in Sweden. Post-industrial society has imposed many limits on emitted air pollutants, yet the number of reports on the negative effects from them is increasing, largely due to human activity in the form of industrial emissions and increased traffic flows. Rising concerns over the health effects from airborne particulate matter (PM) stem from in vitro, in vivo, and cohort studies revealing effects of mostly negative nature. Full insight into the health effects from PM can only be achieved through practical investigation of the mode of toxicity from distinct types of particles and requires techniques for their identification, monitoring, and the production of model fractions for health studies. To this effect, comprehensive collection and chemical analysis of particulates at the origin of emission was performed in order to provide clearer insight into the nature of the particulates at exposure and add detail to aid risk assessment. Methods of capturing particles and analyzing their chemical nature were devised using scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). Furthermore, taking the approach of in vitro cytotoxicity testing, nanoparticles of types typical to automotive emissions, were synthesized and extensively characterized using SEM-EDS, X-ray diffraction (XRD), transmission electron microscopy (TEM),dynamic light scattering (DLS), and nanoparticle tracking analysis (NTA). The produced model magnetite and palladium nanoparticles were found to induce toxicity in human pulmonary epithelial cells (A549 and PBEC) as well as impact severely on immunological and renal cells (221 B- and 293T-cells) in a dose-dependent manner

Review of thermal management of catalytic converters to decrease engine emissions during cold start and warm up

Catalytic converters mitigate carbon monoxide, hydrocarbon, nitrogen oxides and particulate matter emissions from internal combustion engines, and allow meeting the increasingly stringent emission regulations. However, catalytic converters experience light-off issues during cold start and warm up. This paper reviews the literature on the thermal management of catalysts, which aims to significantly reduce the light-off time and emission concentrations through appropriate heating methods. In particular, methods based on the control of engine parameters are easily implementable, as they do not require extra heating devices. They present good performance in terms of catalyst light-off time reduction, but bring high fuel penalties, caused by the heat loss and unburnt fuel. Other thermal management methods, such as those based on burners, reformers and electrically heated catalysts, involve the installation of additional devices, but allow flexibility in the location and intensity of the heat injection, which can effectively reduce the heat loss in the tailpipe. Heat storage materials decrease catalyst light-off time, emission concentrations and fuel consumption, but they are not effective if the engine remains switched off for long periods of time. The main recommendation of this survey is that integrated and more advanced thermal management control strategies should be developed to reduce light-off time without significant energy penalty

Automotive air pollution : issues and options for developing countries

Air pollution constitutes an ominous threat to human health and welfare. Its adverse effects are pervasive and may be disaggregated at three levels: (a) local, confined to urban and industrial centers; (b) regional, pertaining to transboundary transport of pollutants; and (c) global, related to build up of greenhouse gases. These effects have been observed globally but the characteristics and scale of the air pollution problem in developing countries are not known; nor has the problem been researched and evaluated to the same extent as in industrialized countries. Air pollution, however, can no longer be regarded as a local or a regional issue as it has global repercussions in terms of the greenhouse effect and depletion of the ozone layer. This paper discusses the contribution of motorized land transport to air pollution problems, with special reference to developing countries. It assesses the adverse effects of air pollution from transport sources, primarily motor vehicles, and reviews possible approaches to bring about improvements. The paper identifies key issues and research needs related to land transport and air pollution in developing countriesTransport and Environment,Environmental Economics&Policies,Montreal Protocol,Energy and Environment,Roads&Highways