Diesel particulate filter: What is it, and What are its types?

A diesel particulate filter is a device that traps the fine materials from the exhaust of diesel engines. The trapping process uses either an inertial or passive method to trap these particles and reduce their emissions into the air.

Diesel particulate filters, dpf filter, are used to reduce vehicle emissions linked with the increasing prevalence of respiratory diseases. In addition, diesel engines can be up to 30% more fuel-efficient than gasoline counterparts because they produce lower carbon dioxide and nitrogen oxide emissions per mile driven.

For a filter to work efficiently, it must contain an adequate amount of a porous substrate. The porosity is dependent on the type, size, and shape of pore openings in the filter media.

There are several types of diesel particulate filters, including wall-flow after-treatment devices (WFA), cyclone collection traps (CCT), and regenerative thermal oxidation systems (RTO).

A) Wall-flow after-treatment device (WFA)

Wall-flow after-treatment device (WFA) is the most common type of diesel particulate filter in use today. A WFA uses a porous substrate to trap the fine particles. The material is collected by centrifugal force and heat because of high-speed airflow at the outlet port during normal vehicle operation.

B) Cyclone collection trap (CCT)

A cyclone collection trap (CCT) consists of several stages to remove soot particles from the exhaust gas. The first stage uses an inertial method that separates large amounts of dust by centrifugal force, creating a vortex chamber surrounding the filter. The second stage uses an inertial method to separate smaller soot particles using centrifugal force, creating a vortex surrounding the filter. The third and final step of CCT is called thermal oxidation, which injects air into the diesel particulate trap at high temperatures. This causes oxygen molecules in the air to bind with carbon monoxide, hydrogen, and hydrocarbons compounds in the exhaust.

C) Regenerative thermal oxidation system (RTO)

A regenerative thermal oxidation system (RTO) uses heat from the engine to oxidize carbon monoxide into carbon dioxide inside a diesel particulate filter.  There are two types of RTO, passive and active. In the case of a passive system, there is no outside oxygen source or fuel injection during regeneration, while a dynamic system uses external air for combustion.

In summary, diesel particulate filters are becoming more popular due to their ability to reduce air pollution. They are used in both new and existing vehicles for this purpose but must be replaced when full of accumulated particles or after reaching a certain number of miles driven.

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