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.

Regeneration:

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.

SCR

To get the significant reduction in NOx for Tier 4b, we will see some different approaches in the market. One of the solutions to NOx reduction is Selective Catalytic Reduction (SCR). SCR technology utilizes an additive called Diesel Emission Fluid (DEF) which is a non-toxic liquid (urea) currently produced and used in agriculture, food and cosmetics. DEF is injected into a catalytic converter which converts the NOx to harmless Nitrogen. If SCR technology is chosen, distribution of the additive will already be well established in the on-highway market due to the majority of engine manufactures introducing it in 2010.

Construction equipment requires specific engine performance characteristics. Volvo Construction Equipment has long recognized this, tailoring engine technology to optimize all aspects of machine operation and ownership. Other Volvo Group companies will ultimately choose the right technology from the vast array of tools in our tool box to optimize engines to meet their customer needs and the demands to meet the ever increasing environmental challenges.

How will we get there and meet our customer’s needs?

Off-road regulations lag on-road regulations, by about four years in recent times. 2007 on-road saw the implementation of diesel particulate filters and ULSD. We on the off-road side will likely see the same type of technology make the transfer to off-road beginning in 2011 for engines 175 hp (130 kW) and above.

Similarly, on-road will see further emission reduction and new technology introduced in 2010. Off-road is poised to see another round of emissions reductions for Tier 4b in 2014. We will carefully evaluate all technology to access its fit in off-road applications.

Volvo is a leading global manufacturer of engines for both on-road and off-road. This positions us incredibly well to transfer our vast experiences and technologies already developed, tested and productionized in the global on-road sector and apply it to our off-road development. Top competitors cannot offer this level of experience. Let’s talk about some of the technology.

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