Search Results

The maximum use temperature of a diesel particulate filter is often thought to be limited only by the melting point of the filter material itself. This paper suggests that the maximum practical use temperature for filters is limited not by the intrinsic filter melting temperature, but by the temperature at which the metal oxide ash collected from the engine exhaust sinters and adheres to the filter wall, or the temperature at which the filter undergoes eutectic melting by reaction with the ash. Ash sintering and adherence without reaction with the filter material may result in loss of filter permeability and a permanent pressure drop increase. Chemical reactions between the ash and the filter can result either in pinholes through the walls, which compromise filtration efficiency, or glazing on the surface of the walls, which increases back pressure.

This review covers some of the major advances pertaining to reducing tailpipe emissions of greenhouse gases and criteria pollutants. Discussed are both new and upcoming regulations, and technologies being developed for improving engines and after-treatment systems. There is clearly a focus on reducing greenhouse gas emissions in major countries, implemented through ambitious CO2 and electrification targets. Several mature IC engine (ICE) technologies are reviewed which promise to deliver double digit reductions in CO2 emissions. We cover some of these in detail, including gasoline compression ignition, pre-chamber combustion, water injection, and cylinder deactivation. Electrification of the powertrain and synergistic gains with advanced engine technologies are examined. The case is made for the need for cradle-to-grave analyses when evaluating various powertrain choices, and highlight the role hybrids can play in achieving significant and immediate CO2 reductions.

The stringent emissions legislation has necessitated advances in the catalytic converter system comprising the substrate, washcoat technology, catalyst formulation and packaging design. These advances are focused on reducing light-off emissions at lower temperature or shorter time, increasing FTP efficiency, reducing back pressure and meeting the mechanical and thermal durability requirements over 100,000 vehicle miles. This paper reviews the role of cordierite ceramic substrate and how its design can help meet the stringent emissions legislation. In particular, it compares the effect of cell geometry and size on performance parameters like geometric surface area, open frontal area, hydraulic diameter, thermal mass, heat transfer factor, mechanical integrity factor and thermal integrity factor - all of which have a bearing on emissions, back pressure and durability. The properties of advanced cell configurations like hexagon are compared with those of standard square cell.

New test methods were developed to characterize the high temperature durability of intumescent mats that are used to mount ceramic catalyst supports in stainless steel cans. The key attribute of these tests is the use of an electric resistance heating method to maintain a temperature gradient through the thickness of the mat when a cyclic or constant shear stress is applied to the mat interface. These tests are simple to perform and do not require expensive equipment or highly skilled operators. Using these new test methods, the durability of ceramic preconverters mounted with 4070 gm/m2 intumescent mat was studied. The results of these tests indicate that a preconverter package with 4070 gm/m2 intumescent mat can perform satisfactorily in the close-coupled application where temperatures exceed 900°C. The mat performance can be quantified in terms of applied stress and test temperature by utilizing the experimental methods described in the present study.

An In-line hydrocarbon (HC) adsorber system was developed to reduce cold start HC emissions. The system comprises a first catalyst, adsorber unit, and a second catalyst for oxidation of desorbed HC. During cold start, exhaust gas is directed to the hydrocarbon adsorber using a fluidic flow diverter unit without any mechanical moving parts in the exhaust system. After the first catalyst lights off, the diverter is shut off and the major portion of the exhaust gas then flows directly to the second catalyst without heating the adsorber unit. After the second catalyst reaches light-off temperature additional air was added to oxidize the desorbed HC. The system attributes: NMHC emissions in ULEV range Straight line axial flow Reliable design Limited back pressure penalty The system was tested on a 3.8L U.S. vehicle.

In this paper we discuss a continuum modeling approach to obtain a 2-dimensional description of the behavior of a wall flow diesel particulate filter (DPF) during heat -up. The model is used to solve for the spatial and temporal gradients of temperature observed in a DPF during the heat-up process. Laboratory scale experiments were conducted with filters of nominal length 6″ and diameters 2″ and 5.66″ to study the effect of operating conditions such as filter inlet temperatures and flow rate on different DPF materials. The validation studies show that the simulation results agree well with the experimental data. The validated model is used to make predictions of heat-up behavior and relate material properties and filter geometry to observed trends. The results of the model as applied to various DPF geometries and operating conditions are presented and the behavior of filters of varying thermal conductivity is also elucidated.

The key technology developments reported at SAE conferences in 1999 that pertain to gasoline vehicle emission control are summarized in this report. Covered are integrated solutions, catalysts and substrates, fuel sulfur tolerance and effects, particulate emissions, direct injection spark ignition engine emissions, canning methods, and evaporative emissions.

Motorcycle exhaust emission standards throughout the world are becoming more stringent. Emission control systems utilizing the catalytic converter are already in production in Taiwan for 2-stroke engine motorcycles. Catalysts designed for 2-stroke engines encounter a more severe exhaust environment than do those designed for 4-stroke engines. The two aspects of increased severity are the higher temperatures and higher stresses due to engine vibrations. Precious metal catalysts have been designed to operate in the thermal environment of 2-stroke engines and such catalysts have been successfully applied to both metal and ceramic substrates. However, until now, only the metal substrate catalysts have been utilized in motorcycle application. Ceramic based catalysts have not been considered because the mounting material that holds the catalyst substrate in place did not have enough durability to withstand the thermal/vibrational forces encountered in 2-stroke engine exhaust.

With Bharat Stage VI (BSVI) regulations on the horizon [3],[4]tighter particulate matter (PM) regulations will require the use of wall flow diesel particulate filters for on-road heavy duty (HD) diesel engines in India. The Indian HD vehicle market is very cost sensitive, especially with the majority of engine displacement being less than 7L [5] therefore, after treatment cost plays a significant role in design of the system. Robust wall flow diesel particulate filter solutions with the ability to deliver high filtration requirements required for particle number regulations can be designed in a cost-efficient manner. In this paper advanced design for diesel particulate filters with pressure drop, ash capacity, regeneration, and filtration performance are discussed. Corning’s asymmetric cell technology (ACT) was created to improve ash capacity and reduce pressure drop and has the potential to downsize up to 45%.

The regulative environment is poised for ultra-low emissions in the 2024+ time frame with ultra-low NOx proposals from CARB and PN PEMS testing requirements from EU. GHG emissions limits are getting tighter in the next few years along with extended full useful life (FUL) requirements. Diesel Particulate Filters (DPF) will be an integral part of all diesel exhaust aftertreatment systems for the next several years and will need advanced technology solutions to meet the challenges above, without compromising on high performance requirements, namely, low lifetime pressure drop, high filtration efficiency, high durability (extended FUL), increased service intervals or lifetime filter solutions (high ash storage capacity). This paper discusses the primary challenges associated with meeting these future demands and possible technological solutions to address them.

The emission and flow restriction characteristics of three different ceramic substrates with varying wall thickness and cell density (400 cpsi/6.5 mil, 600/4.3, and 600/3.5) are compared. These 106mm diameter substrates were catalyzed with similar amounts of washcoat and fabricated into catalytic converters having a total volume of 2.0 liters. A Pd/Rh catalyst technology was applied at a concentration of 6.65 g/l and a ratio of 20/1. Three sets of converters (two of each type) were aged for 100 hours on an engine dynamometer stand. After aging, the FTP performance of these converters were evaluated on an auto-driver FTP stand using a 2.4L, four-cylinder prototype engine and on a 2.4L, four-cylinder prototype vehicle. A third set of unaged converters was used for cold flow restriction measurements and vehicle acceleration tests.