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Filtration of soft particles

Time: Fri 2021-10-08 10.00

Location:, Stockholm (English)

Subject area: Machine Design

Doctoral student: Botond Csontos , Förbränningsmotorteknik

Opponent: Dr Jim Barker,

Supervisor: Andreas Cronhjort, Maskinkonstruktion (Inst.); Hanna Bernemyr,


The transportation industry relies heavily on fossil fuels, a dependency that isnot sustainable for the future. The easiest way to change this dynamics is to userenewable fuels, such as biodiesel or hydrotreated vegetable oils, which can be usedas drop-in fuel or blends, without engine modifications. However, when differentfuels are mixed, unwanted precipitation may occur. The precipitates produced bythis process are referred to as soft particles. These soft particles have previouslybeen pinpointed to cause fuel system problems such as nozzle fouling, internal dieselinjector deposits or even fuel filter plugging. These problems will eventually allcause deterioration of engine performance, higher fuel consumption and increasedemissions.This thesis aims to evaluate the possibility for providing a solution to theproblems caused by soft particles through advanced fuel filtration. In order to do so,an initial study was done to investigate the effect of metal carboxylates on nozzlefouling through engine tests. In these tests, fuel solubility and nozzle geometry wereinvestigated. To understand the challenges in filtration, a detailed analysis wasdone on plugged fuel filters. This study helps to better understand the compositionof the soft particles. Following these initial studies, efforts were made to replicatesoft particles under laboratory conditions, resulting in a method to synthesise softparticles through the degradation of fuel. Finally, a custom-built small-scale fuelfilter rig was developed, in order to test different fuel filters. Using the fuel filter rig,the potential of currently available fuel filters was evaluated. The materials of thefuel filters were also analysed. Finally, alternative filtration methods were evaluatedfor vehicle applications such as membrane filters and adsorption filters.As a result of these efforts, a mechanism for continuous injector deposit build-upand removal was proposed. Soft particles were identified as a mixture of insolubleorganic contamination. Particular attention was given to calcium soaps with polargroups at both ends of the molecule, specifically calcium methyl azelate. A gaschromatography mass spectroscopy method was developed to quantify this soaptype. The experiments on the filtration rig showed that the fuel filters with glassmicrofibre in their upstream layer proved to be slightly beneficial for soft particleremoval. From the perspective of alternative filtration methods, an adsorption filterproved to be of great interest for further studies in vehicle applications.