Search Results

Gasket materials are utilized for various different types of high temperature testing to prevent leaking at bolted joints. In particular, the automotive test services field uses flanged-gasket bolted exhaust joints to provide a convenient method for installation & removal of exhaust components like catalytic converters for aging, performance testing, etc. Recent improvements in the catalyst aging methods require flanged-gasket joints that can withstand exhaust temperatures as high as 1200°C. Gasket materials previously used in these applications like the graphite based gasket materials have exhibited physical breakdowns, severe leakage, and general thermal failures under these extreme temperatures. In order to prevent these leaks, metal-reinforced gasket materials in a number of configurations were introduced to these extreme temperature environments to evaluate their robustness to these temperatures.

Close-coupled or manifold catalysts have been extensively employed to reduce emissions during cold start by achieving quick catalyst light-off. These catalysts must have good thermal durability, high intrinsic light-off activity and high HC/CO/NOx conversions at high temperature and flow conditions. A number of studies have been dedicated to engine control, manifold design and converter optimization to reduce cold start emissions. The current paper focuses on the effect of catalyst design parameters and their performance response to different engine operating conditions. Key design parameters such as catalyst formulation (CeO2 vs. non CeO2), precious metal loading and composition (Pd vs. Pd/Rh), washcoat loading, catalyst thermal mass, substrate properties and key application (in use) parameters such as catalyst aging, exhaust A/F ratio, A/F ratio modulation, exhaust temperature, temperature rise rate and exhaust flow rate were studied on engine dynamometers in a systematic manner.

FTP and ECE + EUDC emissions are measured from six converters having similar restriction and platinum group metals on two 1999 prototype engines/calibrations. A 2.2L four cylinder prototype vehicle is used to measure FTP emissions and an auto-driver dynamometer with a prototype 2.4L four cylinder engine is used to determine the ECE + EUDC emissions. The catalytic converters use various combinations of 400/3.5 (400cpsi/3.5mil wall), 400/4.5, 400/6.5, 600/3.5, 600/4.5, and 900/2.5 ceramic substrates in order to meet a restriction target and to maximize converter geometric surface area. Total catalyst volume of the converters varies from 1.9 to 0.82 liters. Catalyst frontal area varies from 68 cm2 to 88 cm2. Five of the six converters use two catalyst bricks. The front catalyst brick uses either a three-way Pd washcoat technology containing ceria or a non-ceria Pd washcoat technology. Pd loadings are 0.1 troy oz. of Pd.

Design of automotive catalytic converters is a complex process involving the optimization of many physical and chemical variables. Often, simple characteristics such as geometric surface area and space velocity are used to compare alternative designs. Unfortunately, these parameters do not account for all of the relative variables affecting emissions performance. The effectiveness-Ntu methodology, developed for heat exchanger design, can be extended to catalytic converter design through the heat and mass transfer analogy. This technique allows comparisons to include all physical variables affecting emissions performance. This paper presents Ntu-based, catalyst performance criteria for steady state and transient emissions and exhaust flow restriction. The theoretical analysis includes the effects of washcoat on cell geometry and, subsequently, on heat/mass-transfer performance.