The particulate filter - what is it? Regeneration of particulate filter
Cars, namely their exhaust fumes,represent a great threat to the environment. Therefore, automakers began to equip their machines with different catalysts. And if on cars with gasoline engines it is just so called, then on diesel engines - it is a soot filter. What is this element? What is its structure and operating principle? About all this and not only - later in our article.
Appointment
The diesel particulate filter is designed forpurification of exhaust gases from soot particles. Using this element in the exhaust system can reduce the carbon black content by 95 percent. The latter is formed due to incomplete combustion of fuel.
Where to use
What kind of car is the diesel particulate filter put on? "Volkswagen", "Audi", "Mercedes". This is a partial list of cars that are completed with this element. On passenger cars the diesel particulate filter has been installed since 2000, with the application of environmental standards "Euro-2" and higher. In the European Union countries, the availability of this catalyst is mandatory from 2011, even on passenger cars.
Location:
Where is the particulate filter? "Mercedes" and many European-made cars have the same catalyst arrangement. It is just behind the exhaust manifold. This location is due to the fact that it is at this point that the temperature of the gases reaches its maximum.
The device and the principle of operation
The main element of the particulate filter is ceramicmatrix. It is made of silicon carbide. The same material is used on catalysts of gasoline engines. The matrix is placed in a metal filter housing and has a mesh structure with alternately closed cells. The lateral part of the element is porous. It acts as a filter. The cells of the catalyst matrix are square.
Stages of filtration
Filtering and regeneration - according to this principleeach particulate filter operates. What it is? Filtration is the process by which the soot particles are captured and further sedimented on the walls. The larger they are, the easier it is for the catalyst to work. However, the exhaust gases have a small percentage of fine carbon black, up to 1 μm in size. They represent the greatest threat to the environment and the human respiratory tract.
Also note that in time a particulate filter("Renault Master TDI" - not an exception) is hammered, and he needs a replacement. But due to the high cost (from $ 400), Russian car owners "cut" it out of the "brains" of the computer and put in its place a "spacer" - a metal pipe of the same diameter.
Passive Regeneration of Particulate Filter
This operation is carried out at the expense of hightemperatures (from 500 degrees Celsius). That's why the catalyst is installed immediately behind the exhaust manifold. Penetrating into the diesel particulate filter, exhaust gases (namely, nitrogen compounds) react with oxygen, so that nitrogen dioxide is formed. The latter, when combined with soot, is converted to oxide and carbon monoxide. The last two components, reacting with oxygen, are split into nitrogen dioxide and carbon dioxide. This is the process of filtering the exhaust gases on a diesel car.
In certain engine operating modes, the collection of soot can be inefficient. She walks calmly through the cells to the outside. In this case, the active regeneration of the particulate filter is activated.
Active
This treatment consists in forcing a rise in the temperature of the exhaust gases. It happens all in a short period of time. There are several ways to force a temperature rise:
- Later fuel injection.
- Heating of gases by microwaves.
- Fuel injection in front of diesel particulate filter.
- Installing the electric heater.
The design of the neutralizer is constantly being improved, and now the most popular type is a filter with catalytic coating and an input system for fuel additives. Let's look at them in more detail.
Catalytic particulate filter
What is this element? This filter is used on cars of the Volkswagen family. The principle of operation includes active and passive regeneration.
In the latter case, processing takes place at the expense ofcontinuous oxidation of soot due to the catalyst - platinum, through which gases pass. The operating temperature is from 300 to 500 degrees Celsius. The active process occurs at a higher temperature of 650 degrees Celsius.
This involves a number of managerssensors. This is an air mass meter, sensors for the inlet and outlet temperature of the exhaust gas, as well as the pressure in which the particulate filter operates. What does it give? All received data are processed via the computer, as a result of which the control unit either gives a signal for a later fuel injection or reduces the air supply to the chamber. In this way, the temperature of the exhaust gases is significantly increased, and they react with the catalytic elements.
Filter with additive system
This catalyst was developed by Frenchengineers and is installed on cars "Peugeot", "Citroen", as well as on "Fordy" and "Toyota". Another name for the particulate filter is FAP. The essence of the work is quite simple. The system contains an additive with a catalytic converter (cerium), which is added to the fuel and contributes to a change in the combustion temperature of soot (about 500 degrees Celsius). However, at low loads it is difficult to achieve, therefore forced regeneration is connected to work. The additive itself is stored in a separate container (4-5 liters).
Its resource is about 100 thousand kilometersand is equal to the service life of the filter itself. In the tank, this additive is fed by an electric pump. It is dosed at each refueling of an electronic control unit. The main drawback of using this system - when burning cesium settles on the walls in the form of ash, which strongly clogs the filter. Therefore, it has such a short service life.
How to extend the service life?
Since soot burns out at high temperaturestemperatures, the lifetime of the filter depends directly on the frequency of its burns. Thus, the more often this operation occurs, the less the resource of the element.
How to determine clogging?
The symptoms of a clogged filter are easy to recognize. This is a weak draft, smoke from the exhaust pipe, over-consumption of fuel. Usually in the section such elements look exactly like in the photo below.
In this case, we urgently need to take measures - replace it with a new one (which our car owners are unlikely to follow) or remove it from the system.
Conclusion
So, we found out what thediesel catalyst. As you can see, this device perfectly fights with cleaning soot. However, all good things disappear when the time for replacement comes. The cost of the new element is about 50-80 thousand rubles.
