Particulate filters. Purpose, device, principle of operation

The introduction of new standards for the environmental safety of cars forces manufacturers to develop increasingly sophisticated technologies that allow their products to comply with regulations. Such aspirations are due to the emergence of whole engine families, which are characterized by low emissions of processed products. Work is also being done in other areas. So, in 2004 there was a diesel particulate filter, which minimizes the amount of harmful emissions. Although by the time of its appearance it was not so widely in demand, the developers continued to develop the idea, and nowadays, according to the Euro-5 standard, the presence of this device in the construction of the car is mandatory.

Why do I need a particulate filter?

Devices of this type are the means for post-treatment of exhaust gases. It should be noted at once that diesel particulate filters are used exclusively in diesel engines. In gasoline aggregates, their analogue is a catalyst. The main task of the installation is to remove toxic substances from the exhaust. Such processing of gases makes cars more environmentally friendly. Filters can be different in design, but all of them fulfill the task of reducing the soot content in exhausts by 80%.

Unfortunately, the performance of this function entails a lot of other problems, most of which are related to the maintenance of the filter itself. As the gases are processed, the device becomes dirty and requires cleaning. In extreme cases, the particulate filters are removed, and new post-treatment components are installed in their place.

Filter device

The unit is located behind the catalytic converter. Some filter variations also allow for its structural alignment with the oxidation catalyst. In such cases, it is located behind the exhaust manifold, where the maximum temperature of the gases is noted. The main component is the matrix, located in a metal casing. In standard models, it is made of silicon carbide, which is characterized by a cellular structure with channels of small cross section. Actually, the porous structure of the side walls in these channels and ensures the performance of cleaning. It is important to note that diesel particulate filter is only part of a whole range of devices and systems involved in the work process. This group also includes temperature sensors, a power unit, an on-board computer, a turbocharger, etc. It is another matter that the filter performs the final cleaning function and therefore can be considered as a key link, since it realizes the physical detention of harmful elements.

Principle of operation

The whole process can be divided into two stages - direct filtration and regeneration of soot. In the first stage, the soot particles are trapped, and then they settle on the filter walls. In this regard, the most problematic are small particles up to 1 μm in size, since their light weight interferes with the retention. Although the share of such elements represents only 5% of the total, they are the most dangerous for humans. However, modern particulate filters can effectively cope with the processing of such particles. The second stage consists in the regeneration of the settled elements. The fact is that their accumulation in large volumes not only harms the filter itself, but also reduces the engine power, since an obstacle is formed for the passage of subsequent gases. In this regard, measures for cleaning soot devices are an obligatory part in the maintenance of the car.

Passive filter cleaning

This type of cleaning is realized due to the influence of high temperatures of exhaust gases, which can reach 600 ° C. Another type of passive method of regeneration is the addition of various additives to the fuel, which ensure efficient combustion of soot. In this case, there is also an effect of temperature, but at a level of 400-500 ° C. Tracking the modes of thermal exposure allows a diesel particulate filter sensor that monitors and some engine performance parameters. However, under certain operating conditions of the car, passive filtration is useless or completely impossible.

Active filter cleaning

This is a compulsory approach to cleaning the filter, which is based on a special increase in the temperature regime in the environment of the exhaust gases. The soot accumulating in the process of maintaining such conditions gradually burns out. The main thing in active cleaning is the ways by which high temperature is reached. Among the most common methods are late fuel injection, diesel injection at the exhaust stroke and heating by microwaves. In some cases, the soot filter is also cleaned by an electric heater. The device can be installed next to the cleaning device, but before that you should carefully consider the configuration of the placement of its components. Management of active recovery is also carried out with the participation of sensors - in particular, devices for measuring pressure and temperature are used.

How do I remove a particulate filter?

Despite the use of modern cleaning systems, filters of this type sooner or later begin to interfere with the operation of the engine. This is expressed in clusters of carbon black, which are not removed by the methods provided. An exit from such situations can be the dismantling of the device. And this event is carried out in two stages. First of all, a mechanical operation is performed, during which the particulate filter is dismantled. The price of this procedure varies from 7 to 12 thousand rubles. By the way, the installation of a new filter is estimated at 30-40 thousand rubles. Therefore, only a few are resolved for a complete upgrade of the cleaning system. The second stage consists in software removal of the device by reflashing the engine control unit.

Conclusion

Developers of environmental standards for cars, of course, take care of the future of mankind and seek to orient manufacturers in the most humane directions in terms of impact on nature. The final product of the development of one of these areas was diesel particulate filters, which reduce harmful influence on the ecological situation. At the same time, the motorists themselves received a lot of problems together with the new installation. It is enough to note the necessity of regularly monitoring the efficiency of filter regeneration. In case of insufficient self-cleaning of the device, the car owner has no choice but to remove this unit or replace it with a new filter. But in both cases, the costs will be inevitable.