Search Results

A typical automotive catalytic converter is constructed with a ceramic substrate and a steel shell. Due to a mismatch in coefficients of thermal expansion, the steel shell will expand away from the ceramic substrate at high temperatures. The gap between the substrate and shell is usually filled with a fiber composite material referred to as “mat.” Mat materials are compressed during assembly and must maintain an adequate pressure around the substrate under extreme temperature conditions. The container deformation measurement procedure is used to determine catalytic converter shell expansion during and after a period of hot catalytic converter operation. This procedure is useful in determining the potential physical durability of a catalytic converter system, and involves measuring converter shell expansion as a function of inlet temperature. A post-test dimensional measurement is used to determine permanent container deformation.

An increasing number of passenger vehicle exhaust systems incorporate catalytic converters that are “close-coupled” to the exhaust manifold to further reduce the quantity of cold-start emissions and increase overall catalyst conversion efficiencies. In general, close-coupled catalytic converters are not necessarily subjected to higher inlet exhaust temperatures than conventional underbody catalytic converters. To establish a foundation of on-vehicle temperature data, several passenger vehicles with close-coupled catalytic converters were studied while operating on a chassis dynamometer. Converter temperatures were measured over a variety of vehicle test conditions, including accelerations and extended steady-state speeds for several throttle positions, at both zero- and four-percent simulated road grades.

A Coordinating Research Council sponsored test program was conducted to determine the effects of diesel fuel properties on emissions from two heavy-duty diesel engines designed to meet EPA emission requirements for 1994. Results for a prototype 1994 DDC Series 60 were reported in SAE Paper 941020. This paper reports the results from a prototype 1994 Navistar DTA-466 engine equipped with an exhaust catalyst. A set of ten fuels having specific variations in cetane number, aromatics, and oxygen were used to study effects of these fuel properties on emissions. Using glycol diether compounds as an oxygenated additive, selected diesel fuels were treated to obtain 2 and 4 mass percent oxygen. Cetane number was increased for selected fuels using a cetane improver. Emissions were measured during transient FTP operation of the Navistar engine tuned for a nominal 5 g/hp-hr NOx, then repeated using a 4 g/hp-hr NOx calibration.

As stringent emission regulations further constrain engine manufacturers by tightening both NOx and particulate emission limits, a knowledge of fuel effects becomes more important than ever. Among the fuel properties that affect heavy-duty diesel engine emissions, cetane number can be very important. Part of the CRC-APRAC VE-10 Project was developed to quantify the effects of cetane number on NOx and other emissions from a prototype 1998 Detroit Diesel Series 60. Three fuels with different natural cetane number (41, 45, 52) were treated with several levels and types of cetane improvers to study a range of cetane number from 40 to 60. Statistical analysis was used to define how regulated emissions from this prototype 1998 engine decreased with chemically-induced cetane number increase. Variation of HC, CO, NOx, and PM were modeled using a combination of a fuel's naturally-occurring cetane number and its total cetane number obtained with cetane improver.

Several studies have investigated the effects of diesel fuel properties on heavy-duty engine emissions. The objective of this CRC-sponsored test program was to determine the effects of oxygenated diesel fuel, and to further investigate the effects of cetane number and aromatic content on emissions from a heavy-duty engine set to obtain transient NOx emissions below 5 and then 4 g/hp-hr. A fuel set was developed with controlled variations in cetane number, aromatics, and oxygen to superette their effects on emissions. Ignition improver was used to increase cetane number of several fuels. Oxygenated diesel fuel was achieved by adding a “glyme” compound to selected fuels to obtain 2 and 4 mass percent oxygen concentrations. With these fuels, emissions were measured over the EPA transient FTP using a prototype 1994 DDC Series 60 tuned for 5 and then 4 g/hp-hr NOx. No exhaust aftertreatment device was used on this engine.