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Thermal-fluid Coupling Analysis of Manifold Catalytic Converter of Engine

Author: BaiJie
Tutor: YanFuWu；LiuZhiEn
School: Wuhan University of Technology
Course: Power Machinery and Engineering
Keywords: Gasoline engine Manifold catalytic converter heat-fluid coupling
CLC: U464.134.4
Type: Master's thesis
Year: 2011
Downloads: 153
Quote: 3
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Abstract

With the improvement of modernization and the development of transportation industry, the number of vehicles has increased sharply in the cities. People pay more attention on air pollution and stringent vehicle discharge standards have been carried out. In China the Section IV stage of GB 18352.3 -2005 light vehicle standard has came into effect on July 1,2010, which strictly restricted the automotive cold boot emission. To meet the new standard, manifold catalytic converter is used. It is installed closer to the cylinder and make the catalytic converter quickly pre-catalyst to reach the ignition temperature used high-temperature exhaust gas, thus it can greatly improve the conversion efficiency and reduce emissions. Currently, the manifold catalytic converter flow field distribution, heat transfer distribution and heat stress distribution calculation has become a major research topic in the design of catalytic converter.In this paper a certain manifold catalytic converter model was built and calculated. The flow field distribution, velocity field distribution temperature field distribution and heat stress distribution were analyzed. An optimization design for the manifold catalytic converter was proposed and the two models were compared.First, this paper introduced the advantages of manifold catalytic converters, design method and research status at home and abroad, and then outlined the basic theory involved in the simulation of the manifold catalytic converter by the computational fluid dynamics (CFD) method, which including the mass conservation equation, momentum equation, energy conservation equation and heat transfer equation. The focus put on porous media model of the carrier region and the heat stress equation solved by the finite volume equation and derived porous medium viscous resistance and inertial resistance formulas. Last, the finite volume method and the finite element method were compared. All these lay a theoretical foundation for heat-fluid coupling simulation of the manifold catalytic converter.Next, used software STAR-CCM + to simulate the heat-fluid coupling steady state of the manifold catalytic converter. The main task was that the manifold catalytic converter meshed and analyzed the physical model which three-dimensional model was put into STAR-CCM + software. The pressure field, velocity field, temperature field, thermal stress distribution in the 5000r/min conditions were researched. The internal flow field Characteristics and solid thermal stress characteristics of the manifold catalytic converter were analyzed and the pressure drop and the reasons of heat stress were studied. The mean of speed coefficient andυmax/υmean of the middle section of manifold catalytic converter carrier were 0.915 and 1.14, all fall within the ideal region. The mean of pressure losses was 14.4 kPa and the sensor was not in the catalytic converter front cover areas which the eddy is easy to form. But the floating rate of pressure losses charged relatively, the temperature distribution was very uneven throughout the exhaust manifold and exhaust manifold area larger thermal stress. Its structure can be modified.Then, improved the design based on the original manifold catalytic converter model, compared the difference of pressure field, velocity field, temperature field, thermal stress of the two-type catalytic converter manifold, and then made unsteady simulation for the modified model The results showed that the modified model performance had been improved and the results were satisfactory.The end, summarized the work in this paper and discussed the follow-up work outlook.

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