|
|
 printable version
Catalyst
Catalyst
| 1 - the case;
2 - consolidation;
3 - honeycomb catalyst |
Elements included in the catalyst and products exiting from the catalyst
All vehicles are installed catalysts to reduce the amount of harmful substances emitted into the atmosphere with the exhaust gases.
Catalytic exhaust gas has a stainless steel, welded to which are attached the inlet and outlet cones to the nozzles and mounting flanges and also Heat Reflector holding the ceramic liner. The entire internal volume of the housing occupied by the porous ceramic monolith fixed rings or stainless steel mesh. The structure of the monolith is a conventional filter, but the entire inner and outer surface of pores in contact with the gases covered with very thin molecular layer of an alloy which contains platinum, rhodium and palladium. The porous monolith is a large area of the surface covered with this alloy from very expensive metals, which mainly determines a high price catalyst.
In the catalyst reaction occurs, resulting in potentially harmful hydrocarbon and carbon monoxide in the exhaust gas are converted into harmless gases and water vapor.
The engine emits the exhaust gases together with the products of complete (water vapor H 2 O, N 2, nitrogen, etc.) and incomplete (carbon monoxide CO, as well as C n H m, nitric oxide NO X) combustion. The total number of components that are contained in these gases exceed a few hundred, and most of them are harmful to human health.
Exhaust gases permeating through the porous monolith surface, firstly, heat it, and secondly, dookislyayutsya. Obtained from CO 2 CO, i.e. carbon dioxide is nontoxic, C n H m in several stages proceeds in CO 2 and H 2 O, NO x is converted to molecular N 2, contained in normal air and in water. In short, the catalyst occur fairly complex chemical reactions due to the high temperature and the presence of a special covering from expensive metals.
The main positive effect of the catalyst - full neutralization of three components - CO, C n H m, NO X - in which the exhaust gases more than other harmful substances. And it is achieved not only due to the presence of platinum, rhodium and palladium. Plays an important role temperature, kept within the boundaries of 300-800 ?� C. If it is reduced to 250 ?� C, chemical neutralization of CO, C n H m, NO X, despite the presence of metal catalysts, do not occur. A temperature of about 900 ?� C begins to melt and break the catalyst film.
Gasoline engines
In all models with the catalyst system of the fuel supply of the closed type, i.e. based on the signal from the oxygen sensor mounted in the exhaust system, the control unit constantly optimizes the composition of air-fuel mixture. Depending on the content of oxygen in the exhaust gas oxygen sensor induces a voltage of 0.1 V (high content of oxygen, a poor mix) to 0.9 V (low oxygen content, rich mixture). Based on these data, the engine control unit changes the opening of the fuel injector and changes the ratio of fuel in the fuel-air mixture. Metric ratio of the fuel mixture in which it occurs, and complete combustion of the exhaust gases are no harmful substances - is 14.7 weight parts of air to 1 part of fuel.
The catalyst operates efficiently at temperatures of 300 ?� C to 800 ?� C.
Diesel engines
On vehicles with diesel engine exhaust emission produced by unregulated oxidising catalytic converter.
Reducing the percentage of nitrogen oxides in the exhaust gas of the diesel engine is achieved by installing on the car system of repeated burning of the fulfilled gases (EGR). The EGR valve of exhaust gas recirculation is installed in the exhaust system and the knee is controlled by a vacuum controller. EGR valve in a warm engine directs a portion of the exhaust gases in the combustion chamber of the engine, resulting in reduced temperature and thus decreases the percentage of nitrogen oxides in exhaust gases.
Operation of cars with catalytic converter
Catalyst - a reliable and simple device that does not need any maintenance, but there are some facts that the owner must know to maximize the life of the catalyst.
Do not use unleaded gasoline in a car equipped with a catalyst, as the lead covers the precious metals in the lattice of the catalyst, reducing the efficiency of their conversion and ultimately will damage the catalyst.
Always keep the ignition and fuel system in good order.
If the engine misfires are observed, do not operate the vehicle until repaired.
If the engine warning lamp will light up the motor control, you must immediately contact the station maintenance. If there is damage to the engine control, apart from the increase in fuel consumption and reduce the dynamic characteristics of the engine can be damaged catalyst.
Do not start the engine by towing.
Do not turn off the ignition at high engine speeds.
Do not use additives in fuel and engine oil, as additives may contain substances that could damage the catalyst.
Do not use the car, unless the exhaust pipe is visible trail of blue smoke.
After stopping the engine exhaust system long time continues to emit large amounts of heat, so you should avoid parking on the grass and dry leaves. Remember that the catalyst is fragile, so avoid shock when removing the catalyst or the exhaust system.
The catalyst used on well adjusted car should serve between 100 and 160 thousand kilometers of the car.
|
|
