This is how the additives in leaded gasoline pollute the catalyst. The lead in leaded gasoline will also contaminate the catalyst. It will cover the entire surface of the catalyst and make the catalytic reaction impossible. Therefore, unleaded gasoline must be used. In order to reduce resistance, the ternary purifier is designed into an oval or cylindrical shape. The metal shell, ceramic carrier and thermal expansion pad are assembled together for welding. The main function of the package is to hold the catalyst carrier in the presence of the exhaust system vibration and gas pressure.
A. Half-shell purifier. The metal shell is welded by two elliptical half shells, a catalyst carrier and a gasket.
B. Roll-type purifier. The metal shell is formed by rolling and welding a metal plate, a catalyst carrier and a gasket.
The main technological process of the upper and lower shells is cutting-drawing-secondary drawing-flanging, forming-trimming. The temperature at which the waste gas conversion rate reaches 50% is called the activation temperature, which is generally around 200-250°C. In order to reach the activation temperature as soon as possible after a cold start, it is necessary to try to ensure that the exhaust gas enters the purifier as far as possible to minimize heat loss. The down pipe connecting the engine exhaust manifold and the purifier adopts double-layer air isolation, which can reduce heat dissipation and speed up starting. The bent down pipe can be filled with sand or frozen with water.
According to the displacement, it can be designed as a single-channel exhaust system or a dual-channel exhaust system. The main factors affecting the life of the purifier: a. Lead, magnesium and other elements poison the precious metals in the catalyst. b. Overheating. This is caused by the sintering of the active layer composition at a high temperature higher than 800-1000°C. The ideal temperature is 400-800℃. c. Mechanical damage. This is caused by the cracking of the shell caused by metal fatigue and the vibration of the ceramic carrier. d. Particles block the exhaust passage.
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