Particulate Filter :
A particulate filter is used to collect the PM generated by combustion. Often called a particulate trap, it does just that - traps the PM. As more and more material is collected, backpressures increase and the filter must be cleaned. The filter cleans itself by oxidizing the material in a process called regeneration. A separate muffler is typically not needed, as the particulate filter adequately silences the exhaust.
Cleaning of the particulate filter is accomplished by regeneration. Regeneration of the filter cleans it of PM by converting it to NO and H2O.The temperature within the filter must be at a certain level to make this happen. Regeneration can happen passively, actively or a combination of both. Passive regeneration is accomplished through the use of a catalyst and requires a minimum exhaust temperature to make the reaction happen. Active regeneration is done by adding heat through the use of a burner in the exhaust. A small amount of fuel can also be injected across a catalyst, raising the temperature and oxidizing the PM. All this happens while the engine is running and results in no loss of production.
Just like the on-road particulate trap, ash is generated through the burning of small amounts of engine oil. Ash cannot be oxidized and therefore it collects and the trap will have to be cleaned at regular intervals. The use of low ash oils and advancements in engine oil control technology help to greatly reduce the need for ash cleaning.
Cooled Exhaust Gas Recirculation (EGR)
Cooled EGR is very effective at lowering combustion temperatures, therefore reducing NOx. Controlled amounts of exhaust gas are routed through a cooler and routed back into the engine mixing with the fresh air in the cylinder. The process reduces the oxygen concentration and lowers the combustion temperature. The amount of EGR varies from mild to massive.
Air Handling and Turbo Charging
Turbo charging is part of the emissions design equation and results in the capability to deliver the optimum pressure in the intake and exhaust manifolds. This makes it possible to tailor the EGR flow back to the inlet manifold and also have optimum performance and fuel economy. Wastegated and Variable Geometry Turbo (VGT) options allow specific tuning based on performance requirements. V-ACT (Volvo Advanced Combustion Technology) continues to evolve, enhancing fuel injection and air handling, along with a new generation of engine management systems with greater speed and precision.