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Conventional catalytic converter developments driven by trial and error attempts by experts who successfully employ heuristics (a set of empirical rules gained through time and experience) will not be able to meet the current demanding needs. The cost and time involved in testing every catalytic converter mandates new approaches aimed at improving efficiency and reducing development lead time. Computational tools such as HeatCad, P-Cat, CatHeat, WAVE, Computational Fluid Dynamics (CFD), Finite Element Analysis (FEA) and Monte-Carlo simulation are sequentially applied to design, optimize and manufacture catalytic converter. Heatcad analysis provides the way to identify thermal management issues and to optimize runner lengths and material thickness of the manifold, and downpipes. P-Cat is used to estimate back pressure due to substrates, washcoat, end cones, and inlet/outlet pipes. CatHeat analysis is used to predict the temperature profile across the converter.

Advanced substrate design, efficient washcoat/catalyst formulation and robust packaging are critical elements to assure performance and durability of catalytic converters and diesel particulate filters. Radial seals, axial seals and L-seals made of knitted wiremesh are used with conventional mounting systems to provide compressible and durable support cushions for catalyst and filter substrates. Axial and radial mounting forces of the seals are optimized by material type, seal density, wiremesh strand, wiremesh surface profile (flat or round), wiremesh surface characteristics, wiremesh temper, thermal impacts, and wiremesh geometry. Compression characteristics of stainless steel alloy A286 tremendously increase (>20%) during heat treatment as precipitation and hardening occurs. Compression force tends to stabilize during cycling, retaining a residual force. Radial seals provide radial mounting pressure and mat erosion protection.

Computer aided engineering is used to design, develop, optimize and manufacture catalytic converter. Heatcad, a transient heat transfer analysis is used to simulate the temperature response in the exhaust system to locate the catalytic converter to achieve maximum performance. Heatcad analysis provides the easy way to identify thermal management issues and to design and optimize the runner lengths and material thicknesses of the manifold, and downpipes. P-Cat is used to estimate back pressure due to substrates, end cones, and inlet/outlet pipes. Catheat, a one dimentional heat transfer tool is used to identify the converter insulation to maintain the required external skin temperature. Computational Fluid Dynamics (CFD) analysis, a powerful means of simulating complex fluid flow situations in the exhaust system, is used to optimize the converter inlet and outlet cones and the downpipes to obtain uniform exhaust gas flow to achieve maximum converter performance and reduce mat erosion.

Typically, the maximum converter skin temperature occurs when the catalytic converter is in the cool down process after the engine is shut-off. This phenomenon is called temperature soaking. This paper proposes a numerical method to simulate this process. The converter skin temperatures vs. time are predicted for the converter cool down process. The soaking phenomenon is observed and the maximum temperature is determined. Temperatures are also predicted for the exhaust gas, substrate, mounting mat and shell of the converter assembly. The numerical results are validated with measurements, and an acceptable correlation is achieved. This study focuses on converters with ceramic substrates; however, this methodology can also be used for converters with metallic substrates.

Fluid flow, temperature prediction, thermal response and light-off behavior of the catalytic converter were investigated using Computational Fluid Dynamics (CFD), combined with a conjugate heat transfer and a chemical reaction model. There are two objectives in this study: one to predict the maximum operation temperature for appropriate materials selection; and the other, to develop a numerical model which can be adjusted to reflect changes in the catalyst/washcoat formulation to accurately predict effects on the flow, temperature and light-off behavior. Temperature distributions were calculated for exhaust gas, catalyzed substrate, mounting mat and converter skin. Converter shell skin temperature was obtained for different mat materials. By changing reactant mass concentrations and noble metal loading, the converter light-off behavior, thermal response and temperature distributions were changed.

Automotive exhaust system components are exposed to many types of vibrations, from simple sinusoidal to maximum random excitations. Computer-Aided engineering (CAE) plays an inevitable role in design and validation of hot vibration shaker assembly. Key Life Test (KLT), an accelerated hot vibration durability test, is established to demonstrate the robustness of a catalytic converter. The conditions are chosen such a way that the parts which passes key life test will always pass in the field, whereas the parts which fail in the key life test need not necessarily fail in the field. The hot end system and the test assembly should survive in these aggressive targeted conditions. The test fixture should be much more robust than the components that it should not fail even if the components fail. This paper reveals the computational methodology adopted to address the design, development and validation of the test assembly.

Generation of discretization with prescribed element sizes are adapted to the geometry. From the rules of thumb, for a complicated geometry it is important to select the reasonable element order, shapes and size for accurate results. In order to that, this paper describes the influence of elemental algorithm of the catalytic converter mounting brackets. Brackets are main source of mounting of various systems mainly intake and exhaust in the engine. In hot end exhaust system, a bracket design plays a vital role because it has to withstand heavy structural vibrations without isolation combined with thermal loads. Bracket design and stiffness determines the whole catalytic converter system's rigidity. So, here discretization of converter brackets by linear and parabolic elements is studied with different elements types and compared.

A stochastic simulation based on the Monte-Carlo method was developed to study the effect of substrate, mounting mat and converter shell dimensional tolerances on the converter manufacturing process. Results for a stuffed converter with nominal gap bulk density (GBD) 1.00 g/cm3 show an asymmetric probability density function ranging from 0.90 to 1.13 g/cm3. Destructive and non-destructive GBD measurements on oval and round production converters show close correlation with the Monte-Carlo model. Several manufacturing options offering tighter GBD control based on component sorting and matching are described. Improvements ranging from 28% and 64% in GBD control are possible.