Locally resolved in-situ detection of the soot loading in diesel particulate filters

In order to meet the emission legislation, in today's diesel cars diesel particulate filters (DPFs) have to be installed. Soot is filtered in the pores of ceramic wall-flow filters, but to avoid clogging, DPFs must be regenerated. By increasing the exhaust temperature, sorbed soot is burned off. An efficient control strategy depends on the knowledge of the amount and the location of soot inside the DPF. We present initial tests of a novel method to measure directly the soot load inside a filter. By electrically connecting single walls of the ceramic filter, a resistance measurement is possible. Soot particles form conductive paths inside the DPF channels. The measured values depend on the amount of soot stored inside the filter. In a special setup, we prepared connections over the lateral axis of a DPF. It is possible to get an insight view of a DPF, e.g., one clearly sees how soot trapping starts at the outlet side of the filter.