An Investigative Study of Sudden Pressure Increase Phenomenon Across the DPF 2014-01-1516

Diesel particulate filter (DPF) is a widely used emission control device on diesel vehicles. The DPF captures the particulate matter coming from the engine exhaust and periodically burns the collected soot via the regeneration process. There are various trigger mechanisms for this regeneration, such as distance, time, fuel and simulation. Another method widely used in the industry is the pressure drop across the filter.During calibration, relation between the pressure sensor reading and soot mass in the filter is established. This methodology is highly effective in successful DPF operation as pressure sensor is a live signal that can account for any changes in engine performance over time or any unforeseen hardware failures.On the other hand, any erroneous feedback from the sensor can lead to inaccurate soot mass prediction causing unnecessary regenerations or even needless DPF plugging concerns. A similar phenomenon was observed on certain vehicles where the DPF pressure reading jumped inexplicably leading to DPF plugging concerns.Extensive research and testing was carried out to understand this mysterious phenomenon starting with the usual hardware suspects such as pressure sensor, pressure lines, DPF substrate and washcoat etc. When none of these could be identified as the root cause, same drive cycles that caused this occurrence were tested on vehicles and dynamometer along with the environmental conditions and destructive testing was conducted on the filters.Results indicated a remarkable phenomenon was occurring inside the DPF channels. Under certain driving conditions the soot inside the DPF channels collapsed causing sudden restriction and an abrupt increase in pressure across the DPF. This paper discusses the fascinating journey of how the conditions necessary for this pressure jump to occur were discovered and how some of the hardware design changes could mitigate the sudden pressure increase phenomenon, increasing the DPF robustness.