Torbati, R., Pidria, M., Cerciello, G., and Rodonò, D., "A Fully Integrated Partial Flow Filter with a Specialized and Unique Engine Management System to Meet Tier 4 Emission Legislations," SAE Technical Paper 2013-01-2462, 2013, doi:10.4271/2013-01-2462.
Partial flow filters (PFF) are devices that can capture particulate matter (PM) for a period of time sufficient for its catalytic oxidation. The filter consists of alternating layers of corrugated metal foil and porous sintered metal fleece which captures the particulates. The captured particles are then re-generated passively by nitrogen dioxide (NO2) produced by the oxidation of NO on a diesel oxidation catalyst (DOC) placed before the filter. The filter's robust design and the ability to operate without any maintenance, i.e. no vehicle downtime, have led to an increasing demand for both heavy duty (HD) and light duty (LD) retrofit applications worldwide. Unlike diesel particulate filter (DPF), the PFF will not plug once filled with soot to its maximum capacity in the absence of passive regeneration (low load and low exhaust temperature conditions). Instead, the PM conversion efficiency will gradually decrease, allowing PM emissions to pass through. In order to comply with even more strict Tier 4 emission regulations, it is crucial for the aftertreatment system to guarantee a reliable operation under all possible engine conditions, avoiding phenomena such as break-through or blow offs of PM. Non-road diesel vehicles with extremely wide range of applications and engine operating conditions will inevitably impose high demands on such aftertreatment systems.A specialized and unique engine management system was designed and optimized for off road applications that will maintain efficiency even in the worst-case scenario such as prolonged idling and low-load operations. In fact, under such conditions, when the exhaust gas temperature is not high enough to ensure high soot abatement efficiency, the engine switches to an exhaust temperature management mode in order to recover the initial high PFF filtration efficiency. In this way, the system can be fully flexible and adaptable towards all application and operating conditions and thus suitable to be installed on all vehicle categories.The paper outlines a solution to meet Tier 4 final PM emission limits for engines with power output below 56 kW for industrial machinery using a PFF rather than the conventional DPF system. The paper gives an overview on how the engine and the PFF can be integrated and optimized in order to ensure that high filtration efficiency is always maintained.