Microscale Study of Ash Accumulation Process in DPF Walls Using the Diesel Exhaust Filtration Analysis (DEFA) System

The Diesel Exhaust Filtration Analysis (DEFA) system, developed at the University of Wisconsin – Madison Engine Research Center (ERC), was used to study diesel particulate filters at the micro scale level. Previous measurements using the system have shown that there is a considerable effect of ash accumulation on the filter permeability evolution. Also the pressure drop and loading history are dependent on the number of times a filter had been filled and regenerated. The current investigation of the ash accumulation process has been done to understand its impact on the filter wall permeability over multiple loadings. Three different PM loading conditions were tested over four consecutive loading/regeneration cycles. The pressure history and particle breakthrough for each subsequent loading and regeneration has been recorded. The measurements examine the ash penetration and accumulation for the different operating conditions and for the different number of loadings and regenerations. The results show that the PM deposition mechanism has a significant impact on the ash accumulation process especially within the filter walls. The ash deposition process appears to have a distinct wall loading stage followed by ash membrane formation.