• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.6
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• pp.669-676
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• 2014

A three-way catalyst substrate for domestic passenger car satisfies the design criteria for exhaust gas exchange and pressure drop but does not have satisfactory thermal fatigue performance. Prefracture faults in this three-way catalyst substrate has often been discovered in vehicle repair or vehicle inspection facilities. This paper presents a thermal fatigue performance estimation method for a three-way catalyst substrate using a probabilistic strength reduction factor model. This method is superior to the thermal fatigue performance estimation method for a three-way catalyst substrate that uses a deterministic strength model.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.9
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• pp.58-66
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• 2010

This study examines thermal safety on three-way catalyst that dominates 70 % among whole exhaust gas purification device in 2003. Three-way catalyst durability in the Korea requires 5 years/80,000 km in 1988 but require 10 years/120,000 km after 2002. Three-way catalyst durability in the USA requires 7 years/120,000 km but require 10 years/160,000 km after 2004. Three-way catalyst maintains high temperature in interior domain but maintains low temperature on outside surface. Therefore this device shows tensile stress on outside surface. Temperature distribution of three-way catalyst was acquired by thermal flow analysis for predicted thermal flow parameter. Thermal stress analysis for three-way catalysis was performed based on this temperature distribution. Thermal safety of three-way catalyst was estimated by power law dynamic fatigue life estimation and strength reduction methods for thermal stress.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.7
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• pp.101-108
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• 2010

Domestic three-way catalyst satisfies exhaust gas conversion efficiency or pressure drop etc. but doesn't satisfy thermal durability. Thermal stress analysis for three-way catalyst was performed based on experimental temperature distribution. Thermal safety of three-way catalyst was estimated by safety factor. Aspect ratio variable had the most significant effect on thermal stress. Thickness variable had the least significant effect on thermal stress. Optimal conditions for premature failure prevention of three-way catalyst were as follows : (1) aspect ratio of three-way catalyst : 0.6:1 (2) 2.84mm thick (3) silicon nitride. The safety of Taguchi-optimized three-way catalyst were 4.7 times higher than that of existent three-way catalyst.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6106-6113
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• 2013

Automotive three-way catalyst substrate has a cordierite ceramic honeycomb structure. The substrate in the high engine speed range doesn't satisfy the design fatigue life due to the low mechanical properties of cordierite ceramic. SiC ceramic has higher mechanical properties than cordierite ceramic. If the automotive three-way catalyst substrate is made from the SiC ceramic honeycomb structure, the substrate can be prevented from premature failure. In this study, the mechanical properties of SiC ceramic honeycomb substrate were estimated by FEA. The FEA results indicated that the MOR and elastic modulus for the SiC ceramic honeycomb substrate was much higher than those for the cordierite ceramic honeycomb substrate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3035-3043
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• 2015

This study evaluates the thermal structural safety of the three-way catalyst(TWC) substrate for domestic passenger cars. Thermal-fluid boundary conditions on the TWC substrate were determined by D-optimal DOE. The thermal stresses on the TWC substrate were calculated by the temperature distribution obtained from the CFD results. The safety factors of the TWC substrate were determined by statistical strength and stress distributions and estimated to be 0.275. The thermal stresses for TWC substrate exceeded the strength of the material. Therefore, it is necessary to redesign the TWC substrate because it has much shorter service life than design life.

• International Journal of Fluid Machinery and Systems
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• v.5 no.3
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• pp.134-142
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• 2012

The competition to deliver ultra-low emitting vehicles at a reasonable cost is driving the automotive industry to invest significant manpower and test laboratory resources in the design optimization of increasingly complex exhaust after-treatment systems. Optimization can no longer be based on traditional approaches, which are intensive in hardware use and laboratory testing. The CFD is in high demand for the analysis and design in order to reduce developing cost and time consuming in experiments. This paper describes the development of a comprehensive practical model based on experiments for simulating the performance of automotive three-way catalytic converters, which are employed to reduce engine exhaust emissions. An experiment is conducted to measure species concentrations before and after catalytic converter for different loads on engine. The model simulates the emission system behavior by using an exhaust system heat conservation and catalyst chemical kinetic sub-model. CFD simulation is used to study the performance of automotive catalytic converter. The substrate is modeled as a porous media in FLUENT and the standard k-e model is used for turbulence. The flow pattern is changed from axial to radial by changing the substrate model inside the catalytic converter and the flow distribution and the conversion efficiency of CO, HC and NOx are achieved first, and the predictions are in good agreement with the experimental measurements. It is found that the conversion from axial to radial flow makes the catalytic converter more efficient. These studies help to understand better the performance of the catalytic converter in order to optimize the converter design.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.2
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• pp.48-54
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• 2002

Since photocatalysts are activated by lights of UV wavelengths, plasma is alternatively used as a light source for a photocatalytic reactor. Light intensity generated by plasma is proportional to the surface area of catalytic material, and this, in many practical applications, is prescribed by the geometry of a plasma generator. Thus, it is crucial to increase the surface area far sufficient light intensity for photocatalytic reaction. For example, in a pack-bed type reactor, multitudes of beads are used as a substrate in order to increase the surface area. Honeycomb monolith type substrate, which has very good surface area to volume ratio, has been difficult to apply plasma as a light source due to the fact that light penetration depth through the honeycomb monolith was too short to cover sufficient area, thus resulting in poor intensity for photocatalytic reaction. In this study, nonthermal plasma generation through a photocatalytic reactor of honeycomb monolith substrate is investigated to lengthen this short penetration depth. The ceramic honeycomb monolith substrate used in this study has the same length as a three way catalyst used fur automotive applications, and it is shown that sufficient light intensity for photocatalytic reaction can also be obtained with honeycomb monolith type reactor.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.2
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• pp.129-138
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• 2010

Technical ceramics, due to their unique physical properties, are excellent candidate materials for engineering applications involving extreme thermal and chemical environments. When ceramics are rapidly cooled, they receive thermal shock. The thermal shock parameter is defined as the critical temperature difference. The critical temperature difference for ceramic parts is influenced by its size, the convective heat transfer coefficient, etc. The thermal shock for a component is analyzed by using the transient thermal stress. If the transient thermal stress exceeds the modulus of rupture (MOR), cracking by thermal shock is initiated. The critical temperature difference for water is less than the critical temperature difference for air. The three-way catalyst substrate used in this study has an adequate performance against thermal shock because its radial and axial temperature differences existed below the critical temperature differences.