Diesel Particulate Filter Cleaning Effectiveness: Estimated Ash Loading, Quantified Particulate Removal, and Post-cleaning Filter Pressure Drop

Abstract

Diesel particulate filters (DPFs) are porous ceramic wall-flow devices utilized in diesel exhaust systems to capture particulate matter. DPFs require intermittent on-board regeneration to combust the soot component of particulate matter in order to lower engine back pressure. In addition, proper DPF maintenance requires removal from the vehicle every 100,000–200,000 miles for off-board cleaning to remove the accumulated inorganic ash component of particulate matter. In this study, the capability to quantify off-board DPF cleaning effectiveness was assessed by measuring particulate removal effectiveness and back pressure relief. DPFs were selected from vehicles with the same DPF manufacturer so as to eliminate DPF sizing as a variable. A total of 34 DPFs were removed from on-road heavy-duty diesel vehicles with mostly highway miles with low idle time and were cleaned using pneumatic air cleaning, thermal calcination, and wet cleaning processes. The cleaning processes were used alone, and in series. DPF cleaning effectiveness was evaluated by quantifying particulate removal by weight loss and by measuring DPF back pressure both before and after each process step. The estimated ash exposure values for DPFs in the study were compared with total particulate matter removed from cleaning. The results indicate that back pressure does not provide a complete quantification for off-board cleaning effectiveness, as back pressure may be decreased while DPFs may still retain significant levels of ash.