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This review paper summarizes major developments in vehicular emissions regulations and technologies (light-duty, heavy-duty, gasoline, diesel) in 2012. First, the paper covers the key regulatory developments in the field, including finalized criteria pollutant tightening in California; and in Europe, the development of real-world driving emissions (RDE) standards. The US finalized LD (light-duty) greenhouse gas (GHG) regulation for 2017-25. The paper then gives a brief, high-level overview of key developments in LD and HD engine technology, covering both gasoline and diesel. Marked improvements in engine efficiency are summarized for gasoline and diesel engines to meet both the emerging NOx and GHG regulations. HD engines are just starting to demonstrate 50% brake thermal efficiency. NOx control technologies are then summarized, including SCR (selective catalytic reduction) with ammonia, and hydrocarbon-based approaches.

This paper examines the relative thermal shock requirements for ceramic catalysts in underbody vs. close-coupled positions. The higher operating temperature in the latter position may imply higher coefficient of thermal expansion and higher thermal stresses, depending on substrate/washcoat interaction, than those for underbody position. An analysis of thermal stresses, using relevant physical properties and temperature gradients, is presented for both close-coupled and underbody catalysts. Three different high temperature close-coupled catalysts, employing advanced ceramic substrates with 600/3, 600/4 and 900/2 cell structure, and an underbody catalyst with 400/6.5 standard ceramic substrate are examined. Such an analysis is valuable for designing the optimum aspect ratio (length/diameter) and packaging system, which will minimize thermal and mechanical stresses over the desired lifetime of 120K vehicle miles.

Sub-23nm particles emission from the light-duty vehicle is widely discussed now and possible to be counted into the next stage emission legislation, such as Euro7. In this article, 16 China6 gasoline vehicles were tested over the WLTC and two surrogate RDE lab cycles for particulate number (PN) emission, the difference between PN23 (particle size >23nm) and PN10 (particle size>10nm) emission was analyzed. Testing results showed that the average PN10 emission increased 59% compared to PN23, which will bring great challenges for those vehicles to meet the future regulation requirement if sub-23nm particle is counted. The sub-23nm particles emission was proportional to the PN23 particles emission and generated mostly from the cold start or the transient engine conditions with rich combustion. Compared to the proposal of Euro 7, PN10 emission from some tested vehicles will need further two orders of magnitude reduction.

In order to effectively use CAE to meet wind noise NVH targets, it is important to understand the main wind noise transfer paths. Testing confirmation of these paths by means of acoustic wind tunnel test is expensive and not always available. An on-road test procedure including a “windowing” method (using barriers) was developed to measure wind noise contribution at important higher frequencies through the main transfer paths, which were shown by test to be the glasses at a typical operating condition in which wind noise was dominant. The test data was used to correlate a full-vehicle SEA (Statistical Energy Analysis) model that placed emphasis on the glass properties, main noise transfer paths, and interior acoustic spaces while simplifying all other transmission paths. A method for generating wind noise loads was developed using measured glass vibration data, exterior pressure data, and interior acoustic data.

Driven by the worldwide automotive emission regulations, ceramic substrates were developed to serve as catalyst support. Since the introduction of Standard wall substrates in 1974, substrates with thinner walls and higher cell densities have been developed to meet the tighter emission requirements; Worldwide, the amount of Thinwall and Ultrathinwall substrates in series applications is increasing continuously. The properties of the substrates determine their performance regarding pressure drop, heat-up and conversion efficiency. These properties are analyzed, as well as the packaging process for Thinwall and Ultrathinwall substrates; A new packaging technique with lower pressure load is described.

Diesel particulate filters are expected to be used on most passenger car applications designed to meet coming European emission standards, EU5 and EU6. Similar expectations hold for systems designed to meet US Tier 2 Bin 5 standards. Among the various products oxide filter materials, such as cordierite and aluminum titanate, are gaining growing interest due to their unique properties. Besides the intrinsic robustness of the filter products a well designed operating strategy is required for the successful use of filters. The operating strategy is comprised of two elements: the soot estimation and the regeneration strategy. In this paper the second element is discussed in detail by means of theoretical considerations as well as dedicated engine bench experiments. The impact the key operating variables, soot load, exhaust mass flow, oxygen content and temperature, have on the conditions inside the filter are discussed.

Over the past decade, regulations for mobile source emissions have become more stringent thus, requiring advances in emissions systems to comply with the new standards. For the popular diesel powered passenger cars particularly in Europe, diesel particulate filters (DPFs) have been integrated to control particulate matter (PM) emissions. Corning Incorporated has developed a new proprietary aluminum titanate-based material for filter use in passenger car diesel applications. Aluminum titanate (hereafter referred to as AT) filters were launched commercially in the fall of 2005 and have been equipped on more than several hundred thousand European passenger vehicles. Due to their outstanding durability, filtration efficiency and pressure drop attributes, AT filters are an excellent fit for demanding applications in passenger cars. Extensive testing was conducted on engine to evaluate the survivability and long-term thermo-mechanical durability of AT filters.

A concern has been expressed regarding the durability of the ceramic thin wall and ultra-thin wall substrates under severe thermal and mechanical conditions. Damage that might result from these conditions would most likely lead to a reduction in catalyst performance. One of the potential damage mechanisms for automotive catalysts is erosion resulting from the impingement of particles onto the front face of the catalyst system. A basic study of the particulate erosion phenomenon of cellular ceramic substrates was undertaken in order to determine, in a controlled setting, the substrate, particulate, and flow conditions that might bring this damage about. This report will discuss a room temperature study of the effects of particle size, particle density, gas flow rate, cellular part orientation, and cellular design parameters on the erosion of ceramic substrates.

With the introduction of a stringent particulate number (PN) limit and real driving emission (RDE) requirements, gasoline particulate filters (GPF) are widely adopted for gasoline engines in Europe and China. The filter collects soot and ash. Like in diesel applications, the collected soot will continuously burn under favorable exhaust conditions. However, at extreme conditions, there could be large amounts of soot build-up, which may induce a highly exothermal event, potentially damaging the filter. Thus, it is important to understand what drives the over-heating in application, and develop counter measures. In this study, an on-vehicle fuel cut (FC) testing procedure was developed. The testing was conducted on two vehicles, one gasoline direct injection (GDI) vehicle and one multiple port injection (MPI) vehicle, with different exhaust systems designs (a close coupled GPF and an under floor GPF) and catalyst coating levels (bare and heavily coated GPFs).

Diesel particulate filters (DPF) have become a standard aftertreatment component for a majority of current on-road/non-road diesel engines used in the US and Europe. The upcoming Stage V emissions regulations in Europe will make DPFs a standard component for emissions reductions for non-road engines. The tightening in NOx emissions standard has resulted in the use of selective catalytic reduction (SCR) technology for NOx reduction and as a result the general trend in engine technology as of today is towards a higher engine-out NOx/PM ratio enabling passive regeneration of the DPF. The novel filter concept discussed in this paper is optimized for low pressure drop, high filtration efficiency, and low thermal mass for optimized regeneration and fast heat-up, therefore reducing CO2 implications for the DPF operation.

As demand for wall-flow Diesel particulate filters (DPF) increases, accurate predictions of DPF behavior, and in particular of the accumulated soot mass, under a wide range of operating conditions become important. This effort is currently hampered by a lack of a systematic knowledge of the accumulated particulate deposit microstructural properties. In this work, an experimental and theoretical study of the growth process of soot cakes in honeycomb ceramic filters is presented. Particular features of the present work are the application of first- principles measurement and simulation methodology for accurate determination of soot cake packing density and permeability, and their systematic dependence on the filter operating conditions represented by the Peclet number for mass transfer. The proposed measurement methodology has been also validated using various filters on different Diesel engines.

In this study quantitative techniques were established to assess the low temperature durability of commercially available mat systems. A new low temperature dynamic resistive thermal exposure (LT-RTE) test method was developed. The mats were evaluated in thermal cycling with maximum substrate skin temperatures from 280°C to 450°C. Results indicate that at low use temperatures the residual shear strength of the mat fell to ∼5-15KPa following 280°C cycling. Under the same LT-RTE exposure conditions an equivalent mat system, following thermal preconditioning to 500°C for 3 hours, possessed a residual shear strength of ∼30KPa. An alternative mat system with a lower shot content fiber was also evaluated, following the same thermal preconditioning previously described. This alternative mat was found to exhibit substantially higher residual shear strengths following LT-RTE aging. A residual shear strength of ∼95KPa was observed for this alternative mat following 280°C LT-RTE aging.

This paper provides elastic analysis of compressive stresses in the matrix and skin regions of automotive substrates during 3D- and 2D-isostatic strength testing. The matrix region is treated as transversely isotropic material and the skin region as isotropic material, each with their independent elastic properties. Such a solution helps quantify load sharing by the matrix and skin regions which, in turn, affect compressive stresses in each region. The analysis shows that the tangential compressive stresses in the skin and matrix differ significantly at the interface due to high stiffness ratio of skin versus matrix. The resulting strain in the skin is more severe for thin and ultrathin wall substrates and may lead to localized bending of interfacial cells thereby inducing premature failure. Methods to reduce compressive strain in both the matrix and skin without affecting performance-related advantages are discussed.

Engine laboratory tests were conducted to assess the impact of B20 biodiesel on the performance of cordierite diesel particulate filters (DPFs). Test fuels included 20% soy based methyl ester blended into ultra low sulfur diesel fuel, and two ULSD on-road market fuels. B20 has a higher cetane number, boiling point and oxygen content than typical on-road diesel fuels. A comparative study was performed using a model year 2007 medium duty diesel truck engine. The aftertreatment system included a diesel oxidation catalyst (DOC) followed by a cordierite wall flow DPF. A laboratory-grade supplemental fuel doser was used in the exhaust stream for precise regeneration of the DPF. Tests revealed that the fuel dosing rate was higher and DOC fuel conversion efficiency was poorer for the B20 fuel during low exhaust temperature regenerations. The slip of B20 fuel past the DOC was shown to produce significantly higher exotherms in the DPF during regeneration.

The impact of ultra thinwall catalysts on TIER2 emission performance, packaging and total system cost was evaluated. The primary focus was to compare ultra-thinwall and thinwall cell configurations (400/3, 400/4, 600/2, 600/3, 600/3 hex, 900/2, and 1200/2) with a baseline 600/4 at constant substrate volume, washcoat and PGM loading. Other areas investigated included the evaluation of decreasing catalyst volume while maintaining constant or increased mass transfer capabilities while holding washcoat and PGM loadings constant. The emissions impact of varying washcoat and PGM loading was measured on specific substrates, including a comparison of square to hex cell. Backpressure for each configuration was calculated with the Corning substrate pressure drop modeling tool. Converters were rapid aged on dynamometers reflecting approximately a 50,000 mile aged performance. Emission testing was completed using the FTP test cycle.

India is the world’s largest two-wheeler (2Wh) market. With the proportion of its middle class rapidly rising, 2Wh sales and the resulting emissions, are expected to grow exponentially. The decision to leap-frog from BSIV to BSVI emission norms shows India’s commitment to clean up its atmosphere. As of now, the regulation mandates Gaseous Pollutant (CO, HC, NOx) emission limits for all 2Whs and a particulate limit (PM & PN) for 2Whs powered by Direct Injection (DI) engines. Most of the 2Whs manufactured in India are powered by gasoline engines using the Port Fuel Injection (PFI) technology, and hence by definition particulate emission limits do not apply to them. Particulates when inhaled - especially of the ultrafine sizes capable of entering the blood stream - pose a serious health risk. This was the primary motivation to investigate the particulate emission levels of the 2Whs, which as on date, do not come under the purview of BSVI regulation.

High emission performance standards and precious metals costs have pushed the catalytic substrate toward high cell density and thin wall, such as the 600/4, 600/3 and 900/2 products. Due to the inherently lower mechanical strength of these products, coupled with a shift from underbody to close-coupled placement, a concern was expressed that the severe thermal and mechanical conditions may cause structural damage to the substrate, which in turn could impact the catalyst performance. One source of reduced performance during use is the loss of catalyst due to erosion. A previous study1 indicated that the existence of particulate in an air-stream could cause substrate erosion. However, it was not clear if other factors could contribute to or accelerate the erosion process. In order to address this question, experiments were performed to examine the influence of high velocity flow, temperature, impingement angle, particulate characteristics, and coating effect on erosion.

A previous paper reported (SAE Paper 2002-01-2884) that it was possible to decrease mode-weighted NOx emissions compared to the OEM calibration with corresponding increases in particulate matter (PM) emissions. These PM emission increases were partially overcome with the use of oxygenated diesel fuel additives. We wanted to know if compounds of toxicological concern were emitted more or less using oxygenated diesel fuel additives that were used in conjunction with a modified engine operating strategy to lower engine-out NOx emissions. Emissions of toxicologically relevant compounds from fuels containing triproplyene glycol monomethyl ether and dibutyl maleate were the same or lower compared to a low sulfur fuel (15 ppm sulfur) even under engine operating conditions designed to lower engine-out NOx emissions.

It has been reported that particulate emissions from diesel vehicles could be associated with damaging human health, global warming and a reduction in air quality. These particles cover a very large size range, typically 3 to 10 000 nm. Filters in the vehicle exhaust systems can substantially reduce particulate emissions but until very recently it was not possible to directly characterise actual on-road emissions from a vehicle. This paper presents the first study of the effect of filter systems on the particulate emissions of a heavy-duty diesel vehicle during real-world driving. The presence of sulfur in the fuel and in the engine lubricant can lead to significant emissions of sulfate particles < 30 nm in size (nanoparticles).

This paper describes a study of ternary V2O5/WO3/TiO2 SCR catalysts coated on standard Celcor® and new highly porous cordierite substrates. At temperatures below 275°C, where NOx conversion is kinetically limited, high catalyst loadings are required to achieve high conversion efficiencies. In principle there are two ways to achieve high catalyst loadings: 1. On standard Celcor® substrates the washcoat thickness can be increased. 2. With new highly porous substrates a high amount of washcoat can be deposited in the walls. Various catalyst loadings varying from 120g/l to 540 g/l were washcoated on both standard Celcor® and new high porosity cordierite substrates with standard coating techniques. Simulated laboratory testing of these samples showed that high catalyst loadings improved both low temperature conversion efficiency and high temperature ammonia storage capacity and consequently increased the overall conversion efficiency.