A Method for Reducing Ash Volume in Wall-Flow Diesel Particulate Filters : Water Injection as a Service Tool to Improve Fuel Consumption and Particulate Filter Service Life

Sammanfattning: In order to meet today’s environmental standards, diesel vehicles must capture the soot and ash emitted from the engine in what is known as a diesel particulate filter (DPF). The continual ash loading of this filter and subsequent exhaust backpressure, increase in fuel consumption, etc. is seen as an unavoidable expense. Replacing the DPF is time consuming and costly, representing significant lost profits to the vehicle owner. However, by reducing the volume of ash in the DPF, the pressure drop and fuel penalty can be curtailed while simultaneously increasing filter life. The thesis paper has presented a study intended to select the ideal method for reducing DPF ash volume in the context of system level integration on a Scania truck. By following an adaptation of the TRIZ method, this work has selected an ideal solution for improving DPF performance. A brief study of two experimental methods for ash volume reduction is presented. From this study, awide-ranging concept generation phase was undertaken to evaluate the ways these methods could be implemented on a vehicle. Through collaboration with industry experts at Scania, a system of criteria was established to select the most promising concept. One concept was chosen for demonstration: water injection into the DPF through a sensor hole in the silencer housing. The proposed injection strategy is such that when the vehicle comes in for scheduled maintenance, this water injection tool can be used to improve vehicle performance and reduce filter changes. In keeping with the criteria and design constraints, this solution eliminates the complication of additional vehicle components, while still effectively reducing ash volume. An initial prototype and subsequent on-vehicle testing is presented which demonstrates that wetting the DPF in this manner is a viable means of reducing ash volume. The result of this test shows that this method can reduce DPF backpressure from ash by 60% after just 3 minutes of water injection. From these results, suggestion for future improvement to the performance and ergonomics of the injection tool is presented.