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The characterization of the thermal and vibration environment of the exhaust systems of three modern day diesel engines, with displacements ranging from 1.9 liter to 12.7 liter, was carried out to support the development of exhaust after treatment components. Tri-axial accelerometer and in pipe thermocouple measurements were recorded at several locations along the exhaust systems during vehicle acceleration and steady driving conditions up to 70 mph. The vehicles were loaded to various gross weight configurations to provide a wide range of engine load conditions. Narrow band and octave band vibration power spectral densities are presented and conclusions are drawn as to the spectral content of the exhaust vibration environment and its distribution along the exhaust system. Temperature time histories during vehicle acceleration runs are likewise presented to indicate expected peak exhaust temperatures.

Wall-flow filter technology has been used for many years to remove particulate emissions from a select number of diesel engine exhaust systems. Significant implementation of diesel particulate filters will require the definition of regeneration strategies that permit the filters to be regularly and durably purged of accumulated non-volatile particulates. This paper will examine the laboratory-bench characterization of filter responses to the wide variety of input conditions to which they may be exposed in practice. The lab-bench filter characterization will be done as a function of generic independent variables such as flow rate, inlet temperature, oxygen content and soot loading. The testing will be conducted on uncatalyzed filters for this preliminary study. The characterization approach will examine such dependent variables as completeness of regeneration and maximum exotherm temperatures.

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.

More stringent emissions regulations, space limitations for catalytic converters in modern automotive applications, and new engine technologies constitute design challenges for today's engineers. In that context high cell density thinwall and ultrathinwall ceramic substrates have been designed into advanced catalytic converters. Whereas the majority of these substrates have a square cell geometry, a potential for further emissions improvement has been predicted for hexagonal cell structures. In order to verify these predictions, a ceramic substrate has been developed combining the features of high cell density, ultrathin cell walls, and hexagonal cell structure. Based on modeling data, the actual cell density and wall thickness of the hexagonal cell substrate will be defined. The performance of that substrate will be assessed by comparing experimental emissions results using two modern Volkswagen engines.

Quantitative in-use pressure measurements were taken from packaging ceramic substrates with the SoftMountSM technology and two more traditional technologies, stuffing and tourniquet. Each technology was assessed using four separate mat materials. Mat selection enhanced the application of the SoftMountSM technology through the reduced pressures applied to the substrate during packaging. High temperature and low temperature thermal cycling studies were performed on the canned converters for the three packaging technologies so that an evaluation could be made of converter durability. The SoftMountSM packaging technology yielded the lowest pressures of all the processes studied, regardless of mat type. The laminar hybrid mat evaluated yielded the best combination of pressure and durability performance. Low temperature residual shear strengths following thermal cycling of the converters showed good correlation between the SoftMountSM technology and the stuffing method.

Mat material durability data in the form of fragility curves were generated in a critical temperature region for three intumescent mat materials considered for low temperature converter applications. The mat materials were tested in a tourniquet wrap converter configuration employing a cylindrical ceramic substrate. Prior to developing durability data for these mat materials, the test items were subjected to various environmental thermal and/or vibration aging conditions. Mat material fragility data were generated in terms of the dynamic force required to impose prescribed differential motion between the can and substrate, thereby, subjecting the mat material to a dynamic shearing like that expected during resonant excitation. As expected, it was found that the mat material capacity to resist shearing deformation decreased when the test samples were subjected to 36 hours of low temperature thermal cyclic aging.

Application of new ultra-thinwall ceramic substrate technology to many new vehicle exhaust emission applications has lead to an interest in better understanding the pressures to which substrates are exposed during packaging operations. A recently identified thin film load cell technology has permitted a more analytical evaluation of pressure distributions that develop during ceramic substrate packaging. The optimum configuration of this technique for studying canning operations will be investigated as part of the study. In addition to identifying the characteristic pressure distributions created during canning processes, the impact of various process parameters on this distribution was also investigated.

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.

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.

A bench scale thermal cycling device was designed and constructed to expose large numbers of converters to simulated automobile cycling conditions. Ceramic catalytic converter systems exposed to this thermal cycling technique were observed to experience equivalent or more severe aging, depending on the aging temperature, than isothermal exposures. Cyclic thermal exposures were examined for two mat basis weights. Each mat was examined at two gap bulk densities. Change in converter residual shear strength, as a function of accumulated thermal cycles, was observed to follow a logarithmic relationship. Results of thermal cyclic engine exposures showed a strong correlation with laboratory bench studies.