Catching Ash : Methodology for ash accumulation in diesel particulate filters

Abstract: The diesel particulate filter captures particulate matter that is produced in the diesel engine. A small fraction of particulate matter is comprised by ash forming matter. When the combustible fraction of particulate matter is removed from the filter, the ash, which is incombustible, remains. The accumulation of ash in the diesel particulate filter increases fuel consumption and shortens the lifetime of the filter. The study of ash accumulation in filters is mostly dependent on field tests; an expensive and time-consuming process. To establish a more economical testing method, both in terms of time and cost, the accumulation of ash in the filter has to be accelerated. Hence, a literature study to determine the important parameters affecting ash formation and deposition pattern has been performed and the results are presented in this thesis. Moreover, a design proposition for an accelerating ash accumulation test rig is presented. The rig design allows for the control of exhaust gas temperature and velocity, soot production rate and morphology, intervals between regeneration as well as position and method of ash forming matter introduction. A burner is used for the production of soot and ash, and the exhaust gases are guided to the filter by a blower placed downstream the filter. The blower compensates for the pressure drop, allowing the gas flow to be constant. For a more precise temperature control, a heater is placed before the inlet of the filter. The different ash production methods that can be tested are the injection of oil in the burner’s flame, the injection of oil in the gas stream, and the use of fuel doped with oil. By replacing the burner with a particle feeder, the rig can also fill the filter with ash; artificial, or collected from actual filters. Additionally, a set of considerations is provided to enable the accurate component specifications/ characterisation. The design is following a modular concept, i.e. the components’ position can change to accommodate various research goals.