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Technical Paper

Interference between Engine Bay Flow and External Aerodynamics of Road Vehicles

This study focus on the aerodynamic influence of the engine bay packaging, with special emphasis on the density of packaging and its effect on cooling and exterior flow. For the study, numerical and experimental methods where combined to exploit the advantages of each method. The geometry used for the study was a model of Volvo S60 sedan type passenger car, carrying a detailed representation of the cooling package, engine bay and underbody area. In the study it was found that there is an influence on the exterior aerodynamics of the vehicle with respect to the packaging of the engine bay. Furthermore, it is shown that by evacuating a large amount of the cooling air through the wheel houses a reduction in drag can be achieved.
Technical Paper

Galvanically Induced Atmospheric Corrosion on Magnesium Alloys: A Designed Experiment Evaluated by Extreme Value Statistics and Conventional Techniques

Galvanic corrosion of high purity die cast magnesium alloys AM50 and AZ91 was examined in accelerated atmospheric corrosion testing according to Volvo STD 1027,1375 for 6 weeks involving cycling of the relative humidity between 90% and 45% in combination with intermittent immersion in one of two NaCl-solutions (0.3% or 1.0%). The exposures were performed at two different CO2 levels; 0.01% and 0.3%. The initial general corrosion rate of the AM50 alloy is 50-100% higher than that of AZ91 depending on surface preparation. The corrosion weight loss of both materials depends linearly on salt load in the investigated range. CO2 has a moderate accelerating effect, being higher with decreased salt load. Extreme value analysis was used to evaluate the deepest pit distribution around the perimeter of mounted bolts in panels of AZ91 and AM50. Quite contrary to the general corrosion results, AZ91 showed 30% deeper pits than AM50.
Technical Paper

Stone Impact Damage to Automotive Paint Finishes: Impact Induced Corrosion in Painted Pre-Coated Sheet Steels

Electrochemical Impedance Spectroscopy (EIS) and Thermal Wave Imaging (TWI) are complementary techniques which can be used to detect and estimate Impact Induced Corrosion (IIC) at the metal-polymer interface. This paper describes the use of the above techniques to detect Impact Induced Corrosion in a variety of pre-coated and painted sheet steels. It has been possible to show, that IIC is a threshold phenomenon and depends on the type of galvanized coating. Evaluation of IIC, using a high performance indoor accelerated test and preliminary data from the proving grounds are presented in this paper.
Technical Paper

Deterioration of Three-Way Automotive Catalysts, Part II - Oxygen Storage Capacity at Exhaust Conditions

Catalysts aged under different on-road conditions were analysed with respect to their conversion of CO and HC at step changes of the synthetic exhaust gas composition. Time resolved diode laser spectroscopy and fast response FID analysis were used to characterise the catalyst response to transient changes of CO and hydrocarbons in the exhaust gas. The oxygen storage capacity was monitored at various conditions; flow rate, catalyst temperature, previous exposure to oxidizing or reducing atmosphere and amplitude of the perturbation. The technique appeared to provide a sensitive probe for analysis of the dynamic oxygen storage capacity of new and aged catalysts at exhaust like conditions. The results correlate well with the transient emission performance during vehicle tests. Further, surface characterization using SEM/EDS and XPS techniques indicated that phosphate formation was the most probable cause of deactivation.