What is a Diesel Particulate Filter ?

Active regeneration of diesel particulate filters is performed when exhaust temperatures are too low for passive regeneration to occur. The most common method for accomplishing this is by raising the exhaust temperature to levels where regeneration can occur. There are two basic approaches for performing this operation   Increasing combustion temperature through engine management; or, In-situ heating of the exhaust stream   Increasing exhaust temperature by raising the combustion chamber temperature is accomplished using various engine management methods. These types of methods require precise knowledge of engine parameters, access to the engine control unit, and performing changes to engine hardware and control. Because of this, the engine management approach is performed by OEM businesses that have direct access and control over their engine design. Among the methods used are late or post-injection of fuel into the combustion chamber, changes to the turbo boost, by-passing turbo intercooling, changes to the EGR valve, throttling, and retarded injection timing. All of these methods can raise the exhaust temperature, but also have negative impacts in the way of lower fuel economy, decreased engine power, increased engine emissions, and increased engine wear. Post-injection (late cycle injection) in particular causes increased engine wear by diluting the engine oil film with fuel. Some of the other methods also decrease available oxygen in the exhaust, which impacts the soot oxidizing ability of the particulate filter. Lastly, much of the heat generated by increasing the combustion chamber temperature is lost to engine coolant and engine components, thus decreasing fuel economy.       The alternative to engine management is heating the exhaust stream directly. One such method is to heat the exhaust via electric heaters; however this method affects fuel economy in much the same way as engine management. To generate power for the heaters, the engine has to increase power delivery – the increased power delivery increases fuel consumption and some of the generated energy is lost to engine coolant and surrounding components (not unlike the heat losses observed in heat generation through engine management). Another method is to heat the exhaust by injecting diesel fuel directly into the exhaust stream then using a catalytic oxidizer to combust the fuel and increase exhaust temperature. This method is the most efficient for increasing exhaust temperature and can have anywhere from 35% to 50% less impact on fuel economy. This method also minimizes engine wear since no changes to the engine performance, either through engine management or increased power generation, is required. For retrofit programs this is also the simpler and less costly approach.         1 | 2 | 3 | 4 | 5 | 6