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The design of a canned ceramic oval converter, 77mm by 146.8mm, is described along with subsequent demonstration of its high temperature (1050°C) durability. A new mat deterioration phenomenon was recognized, and will be described. The mat deterioration results from sintering of the vermiculite and glass fiber structure when exposed to temperatures greater than approximately 1000°C. Due to the extremely high temperature experienced in the supporting mat of an oval converter exposed to 1050°C, an alternative mat configuration was utilized to eliminate potential mat sintering. An inner layer of non-intumescent mat (1500g/m2) was used in conjunction with an outer layer of intumescent mat (3100g/m2). The inner mat provided sufficient thermal protection to the outer intumescent mat, maintaining considerable holding pressure on the ceramic substrate. A tourniquet closure technique was developed to uniformly compress a hybrid mat system around the entire perimeter of the oval converter.

Driven mainly by tightening of regulations, advance diesel emission control technologies are rapidly advancing. This paper will review the field with the intent of highlighting representative studies that illustrate the state-of-the-art. First, the author makes estimates of the emission control efficiency targets for heavy and light duty applications. Given the emerging significance of ultrafines to health, and to emission control technologies, an overview of the significant developments in ultrafine particulate science is provided, followed by an assessment of filter technology. Major deNOx catalyst developments, in addition to SCR and LNT progress is described. Finally, system integration examples are provided. In general, progress is impressive and studies have demonstrated that high-efficiency systems are within reach in all sectors highway vehicle sectors. Engines are making impressive gains, and will increase the options for emission control.

Significant particulate emission reductions of diesel engines can be achieved using diesel particulate filters (DPFs). Ceramic wall flow filters with a PM efficiency of >90% have proven to be effective components in emission control. The challenge for the application lies with the development and adaptation of a reliable regeneration strategy. The main focus is emission efficiency over the legally required durability periods, as well as over the useful vehicle life. It will be shown, that new DPF systems are characterized by a high degree of integration with the engine management system, to allow for initiation of the regeneration and its control for optimum DPF protection. Using selected cases, the optimum combination and tuning will be demonstrated for successful regenerations, taking into account DPF properties.

Current trends in automotive emissions control have tended towards reduced mass substrates for improved light-off performance coupled with a reduction in PGM levels. This trend has led to increasingly thinner walls in the substrates and increased open frontal areas, with a potential of reducing the overall mechanical strength of the substrate relative to the thicker walled lower cell density supports. This change in demand driven technology has also led to developments, at times costly, in the processing of the catalytic converter system. Changes in mat materials, handling technology and coating variables are only a few sources of overall increased system costs. Corning has introduced the Celcor® XS™ product to the market which significantly increases the strength of thin and ultra thin walled substrates.

The tightening of emissions regulations has required changes in many areas of vehicle systems, including calibration strategies, catalytic converter strategies and exhaust configurations. Engine calibration strategies can be engineered to complement the performance parameters of the converter. Knowledge of the precise window of converter performance for different substrates can therefore provide guidance in targeting engine calibration strategies as well as selecting compatible converter systems within calibration constraints. In a previous paper [5], we explored the effect of thermal mass on emissions performance in the context of the FTP. This paper expands on the previous work and explores the effect of the aging cycle and thermal mass differences on CO-NOx crossover and light-off profiles. This analysis provides a tool to assist in design by defining a window of performance in the converter to be used in matching to a window of operation in the calibration.

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.

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).

Characterization of diesel particulate filters requires test methods that permit rapid and accurate assessment of important performance requirements. The operation of the filter is comprised of two primary functions, particle filtering and filter soot regeneration. One challenge facing implementation of diesel filter technology lies with the difficult process of regenerating the filter after accumulating a full complement of soot. This paper will primarily focus on laboratory bench testing methods developed to study the regeneration characteristics of filters under a variety of test conditions. To rapidly assess the performance of many filters it was important to develop laboratory techniques that approximate engine exposure conditions. A simulated soot loading process and a well-controlled regeneration test method were developed.

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.

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.

Compositions in the mixed strontium/calcium feldspar ([Sr/Ca]O·Al2O3·2SiO2) - aluminum titanate (Al2O3·TiO2) system have been investigated as alternative materials for the diesel particulate filter (DPF) application. A key attribute of these compositions is their low coefficient of thermal expansion (CTE). Samples have been prepared with porosities of >50% having average pore sizes of between 12 and 16μm. The superior thermal shock resistance, increased resistance to ash attack, and high volumetric heat capacity of these materials, coupled with monolithic fabrication, provide certain advantages over currently available silicon carbide products. In addition, based on testing done so far aluminum titanate-based filters have demonstrated chemical durability and comparable pressure drop (both bare and catalyzed) to current, commercially available, silicon carbide products.

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).

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.

Increasingly stringent vehicle emissions legislation is being introduced throughout the world, regulating the allowed levels of particulate matter emitted from vehicle tailpipes. The regulation may prove challenging for gasoline vehicles equipped with modern gasoline direct injection (GDI) technology, owing to their increased levels of particulate matter production. It is expected that gasoline particulate filters (GPFs) will soon be fitted to most vehicles sold in China and Europe, allowing for carbonaceous particulate matter to be effectively captured. However, GPFs will also capture and accumulate non-combustible inorganic ash within them, mainly derived from engine oil. Studies exist to demonstrate the impact of such ash on GPF and vehicle performance, but these commonly make use of accelerated ash loading methods, which themselves introduce significant variation.

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.

Information on transport mechanisms in a Diesel Particulate Filter (DPF) provides crucial insight into the filter performance. Extensive experimental work has been pursued to modify, customize and validate a model yielding accurate predictions of a ceramic wall-flow DPF pressure drop. The model accounts, not only for the major pressure drop components due to flow through porous walls but also, for viscous losses due to channel plugs, flow contraction and expansion due to flow entering and exiting the trap and also for flow secondary inertial effects near the porous walls. Experimental data were collected on a matrix of filters covering change in filter diameter and length, cell density and wall thickness and for a wide range of flow rates. The model yields accurate predictions of DPF pressure drop with no particulate loading and, with adequate adjustment, it is also capable of making predictions of pressure drop for filters lightly-loaded with particulates.