All modern car exhaust systems include a catalytic converter. This device is designed to reduce the level of emissions of harmful substances with exhaust gases into the atmosphere. The catalytic converter is used both on diesel power units and on gasoline ones. Install it either immediately behind the exhaust manifold, or directly in front of the muffler. The exhaust gas converter consists of a carrier unit, thermal insulation, housing.
Device
The carrier block is considered the main element. It is made from refractory ceramics. The design of such a block consists of a large number of longitudinal cells, which significantly increase the area of contact with exhaust gases. Their surface is covered with special catalyst substances (palladium, platinum and rhodium). Thanks to these elements, chemical reactions are accelerated.
Palladium and platinum are oxidation catalysts. They ensure the oxidation of hydrocarbons and, accordingly, contribute to their conversion into carbon monoxide, carbon dioxide and water vapor. And rhodium isrecovery catalyst. It is used to reduce nitrogen oxides to harmless nitrogen. It turns out that three types of catalysts reduce the content of three different harmful substances in the exhaust gases. Therefore, such a device is called a three-way catalytic converter.
The storage unit is housed in a metal case. Between them is a thermal insulation layer. The catalytic converter contains an oxygen sensor.
Effective operation of the device in question is achieved at a temperature of 300o Celsius, in which case about 90 percent of harmful substances are retained (for this, the catalytic converter is installed immediately after the exhaust manifold).
Features
Catalysts are quite effective in reducing the toxicity of exhaust gases and at the same time practically do not affect engine power and fuel consumption. In the presence of this device, the back pressure will slightly increase, as a result of which the power unit of the car loses 2-3 liters. With. Theoretically, an exhaust gas catalyst can last forever, because precious metals are not consumed during chemical reactions. However, as practice shows, the service life of these devices has its limit.
For example, one of the common reasons for the failure of converters is the fragile ceramics of the cells, which, from a sharp shock (if the car hits at speed, hits a pothole or even strikes the catalyst body on something -or) may be destroyed, which leads to the failure of the said device. Now converters have begun to appear, in which instead of ceramics there is a metal monolith. They are more resistant to damage. Another cause of catalytic converter failure is fuel. Leaded gasoline is rich in tetraethyl lead, which "s alts" the surface of the cells. As a result, all reactions stop. The next enemy of the catalyst is the wrong composition of the fuel. So, a mixture containing an increased amount of hydrocarbons simply ruins the device, and a mixture that is too poor causes a sharp overheating, which can lead to the destruction of the monolith. No less dangerous are sudden changes in temperature, for example, when a car drives into a puddle. It may also damage the ceramic.
In general, the catalytic converter, like any other mechanism, is affected by operating conditions.
