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A unique validation method is proposed for mount designs of Lean NOx Traps (LNT's), in which characteristic curves of failure points as functions of thermal cycles and vibration amplitudes are generated. LNT's are one of the several new types of emissions control devices applied to Diesel Exhaust Systems, and they reduce the amount of NOx through chemical adsorption. Desulfation must occur nearly every hour, which involves raising the inlet gas temperature of the LNT to around 700°C to “burn off” sulfur from the catalyst, which otherwise would decrease its catalytic activity. This temperature is held for several minutes, and its cyclic occurrence has a negative effect on the long-term performance of the support mat, a major component of its mount design. As substrate temperatures increase, shell temperatures do as well, and thermal growth differences between the ceramic substrate and metallic shell cause the gap between them, which is filled by the support mat, to increase.

Non-round substrates are often applied in exhaust applications with limited packaging space, including commercial vehicles, and the shape of their metallic shells are often designed to be similar, but enlarged to accommodate the layer of support mat. This gap is often planned to be constant around its perimeter, but measured data indicates this rarely occurs. This study evaluates a particular oval converter mount design and applies a unique method to couple finite-element modeling with support mat response characteristics to predict non-round shell shapes, planning for uneven gap distributions. This method allows for increased awareness of acceptable mount designs, as well as improved manufacturing and durability performance, which becomes even more important within commercial vehicle design applications, subject to larger substrate sizes, increased backpressures, and extended mileage requirements.

In order to scientifically approach the design of mounting systems for substrates in emissions control systems, it is essential to characterize the behavior of the involved materials, particularly the support mat. Manufacturing processes and various in-field conditions impact the long term performance of the support mat, and life-long emissions performance is critically dependent on its ability to retain the substrate throughout the intended life. Therefore, to ensure product robustness, the behavior during operation of all available support mats must be appropriately characterized to determine the technical layout in specific applications. This paper addresses three common characterization tests, developed internally and externally. Additionally, equipment improvements to minimize artifacts in test results as well as the development of a new mat test for manufacturing methods are addressed.