Exhaust gas from diesel engines contains solids known as diesel particulate matter, which are hazardous to health.
This particulate matter is largely comprised of carbon, but also contains hydrocarbons and a certain amount of metallic particles as a result of engine wear and the burning of lubricating oil. The role of a diesel particulate filter is to separate these from the exhaust gas stream.
However, the amount of particulate matter produced by even a modern diesel engine is quite significant, so the challenge is to prevent the filter from becoming blocked.
One option is to simply throw the filter element away when it is dirty, and use of such disposable filters is still widespread although there are now better alternatives available. If an exhaust needs to be filtered on a long-term basis, then a means of periodically cleaning the filter must be found. This cleaning process is referred to as ‘regeneration’ and can either be done with the filter in situ (on-board regeneration) or after it has been removed from the engine (off-board regeneration).
Fortunately diesel particulate matter can be made to burn given the right conditions, producing mainly harmless carbon dioxide and water vapour as a result, so nearly all strategies for cleaning diesel particulate filters rely on burning (or oxidation) for their effectiveness. Filters designed for on-board regeneration can either have this process initiated manually or automatically. Manual regeneration is better for very small engines as it avoids a lot of complexity. Automatic regeneration works well on most mobile applications but doesn’t meet the reliability standards for critical applications such as hospital generators. For these critical applications a filter system incorporating a by-pass is required.
We provide a ‘dpf selection guide‘ to help users to choose the most suitable filter for their application.