A methodology was developed to dissect diesel particulate filters to study the time effect of loading for two different fuels: ULSD and a biodiesel blend. Filters loaded with soot from a diesel engine for exposure times of 1, 2, 5 and 10 hours were fractured and samples of filter substrates were analyzed using Raman spectroscopy and scanning electron microscopy. Observations revealed the sharp rise in pressure drop to be attributable to the clogging of the pores in the channel wall, leading to the formation of a pore-bridge. Cross sectional imaging of wall sections revealed this pore-bridge to be shallow, with significant particulate depositions limited to the first quarter of the depth of the filter walls. Images revealed increasingly dense deposits and the formation of coarse particles and soot cakes. Raman spectroscopy revealed no significant graphitization of the soot cake. The dissection methodology exhibits significant potential for future studies on DPFs.

A methodology was developed to dissect diesel particulate filters to study the time effect of loading for two different fuels: ULSD and a biodiesel blend. Filters loaded with soot from a diesel engine for exposure times of 1, 2, 5 and 10 hours were fractured and samples of filter substrates were analyzed using Raman spectroscopy and scanning electron microscopy. Observations revealed the sharp rise in pressure drop to be attributable to the clogging of the pores in the channel wall, leading to the formation of a pore-bridge. Cross sectional imaging of wall sections revealed this pore-bridge to be shallow, with significant particulate depositions limited to the first quarter of the depth of the filter walls. Images revealed increasingly dense deposits and the formation of coarse particles and soot cakes. Raman spectroscopy revealed no significant graphitization of the soot cake. The dissection methodology exhibits significant potential for future studies on DPFs.

The European emission standard is an EU directive which describes what emission limits car manufactures are required to meet. In order to meet these requirements car manufacturers use different techniques and components. In a modern diesel automobile a Diesel Particulate Filter (DPF) is used to gather soot from the exhausts. As soot accumulates in the DPF, the back pressure increases and the capability to hold more soot decreases. Therefore the DPF continuously needs to get rid of the stored soot. The soot is removed through a process called regeneration. In order to optimize when to perform regeneration, it is vital to know the amount of soot in the filter. A method for estimating the soot mass in a DPF using a radio frequency-based sensor has been developed. The sensor that has been studied is the Accusolve soot sensor from General Electric. A parameter study has been performed to evaluate the parameters that affects the sensor’s output. Parameters that have been studied include positioning of the sensor, temperature in the DPF, flow rate through the DPF and distribution of soot in the DPF. Different models for estimation of soot mass in the DPF has been developed and analyzed. An uncertainty caused by removing the coaxial cable connectors when weighing the DPF has been identified and methods for minimizing this uncertainty has been presented. Results show that the sensor output is sensitive to temperature, soot distribution and position, and also show some sensitivity to the flow rate. An ARX model, with only one state, is proposed to estimate the soot mass in the DPF, since it gives the best prediction of soot mass and showed good resistance to bias errors and noise in all the input signals.

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Exhaust emissions in a vehicle has to flow through an exhaust aftertreatment in a diesel vehicle. In a diesel engine, the exhaust emissions are treated with Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF), and Selective Catalytic Reduction (SCR). Every engine produces a different kind of soot depending on the drive cycle. In this thesis, a study was made on the soot oxidation in DPF so as to reduce the net fuel consumption and hence optimising the engine.This project focuses on DPF, where the soot and ash are trapped on the walls of the filter when the emissions flow through the DPF. Over a period of time, the soot accumulates and causes the pressure inside the filter to increase. To reduce the backpressure due to soot accumulation, soot has to be removed from the filter which is done by a regeneration process in which soot is oxidized. To understand the soot oxidation in the DPF, we study the chemical kinetics of the soot.The soot reacts with NO2, O2, and N2 in a Thermogravimetric Analysis (TGA) instrument, in isothermal conditions. Two soot samples, SORT-1 and FORCED 360 were analyzed with TGA, the rate equations were derived from using Arrhenius type kinetics and the data was processed by MATLAB. The rate at which the soot is oxidized by NO2 and O2 for SORT-1 is higher than for FORCED 360. This trend is observed similarly when both the soot samples react with only O2. When soot oxidation reaction takes place with O2 and NO2 they require a lower temperature of 250 °C-400 °C than compared to samples reacting with only O2 with a temperature of 350 °C - 500 °C. To understand the conditions that affect soot oxidation, the concentration of oxygen was varied and it was found that at higher oxygen concentration the soot oxidized is almost constant. Then soot kinetics were analysed by finding the rate of the reaction, the order of the reaction, and finally the activation energy. The order of the reaction for FORCED 360 and SORT-1 vary and slope of the graph, logarithm of reaction constant vs logarithm of mass shows a non-linearity in the former due to the slower rate of the reaction in SORT-1 than in FORCED 360. The activation energy was found to be 39.3 kJ/mol for SORT-1 and FORCED 360 is 60.8 kJ/mol. / Avgasutsläpp i ett fordon måste strömma genom avgasefterbehandling i ett dieselfordon. I en dieselmotor behandlas avgasutsläppen med dieseloxidationskatalysator (DOC), dieselpartikelfilter (DPF) och selektiv katalytisk reduktion (SCR). Varje motor producerar olika typer av sot beroende på körcykeln. I denna avhandling gjordes en undersökning av sotoxidationen i DPF för att minska nettobränsleförbrukningen och därmed optimera motorn. Detta projekt fokuserar på DPF, där sot och aska fångas på filterväggarna när utsläppen flyter genom dieselpartikelfiltret. Under en tidsperiod ackumuleras sot och får trycket inuti filtret att öka. För att minska mottrycket på grund av sotansamling måste sot avlägsnas från filtret, vilket görs genom en regenereringsprocess där sot oxideras. För att förstå sotoxidationen i DPF studerar vi sotens kemiska kinetik. Sotet reagerar med NO2, O2 och N2 i ett instrument för termogravimetrisk analys (TGA) under isotermiska förhållanden. Två sotprover, SORT-1 och FORCED 360 analyserades med TGA, hastighetsekvationerna härleddes från användning av Arrhenius-typskinetik och data bearbetades av MATLAB. Den hastighet med vilken sot oxideras av NO2 och O2 för SORT-1 är högre än för FORCED 360. Denna trend observeras på liknande sätt när båda sotproverna reagerar med endast O2. När reaktion genom sotoxidation äger rum med O2 och NO2 kräver de en lägre temperatur på 250 ° C - 400 ° C än jämfört med prover som bara reagerar med O2 med en temperatur på 350 ° C - 500 ° C. För att förstå de förhållanden som påverkar sotoxidation varierades syrekoncentrationen och det visade sig att vid högre syrekoncentration var sotet oxiderat nästan konstant. Därefter analyserades sotkinetiken genom att hitta reaktionshastigheten, reaktionsordningen och slutligen aktiveringsenergin. Reaktionsordningen för FORCED 360 och SORT-1 varierar och lutningen i diagrammet, logaritmen för reaktionskonstanten mot logaritmen av massan visar en icke-linjäritet i den tidigare på grund av den långsammare reaktionshastigheten i SORT-1 än i FORCED 360. Aktiveringsenergin konstaterades vara 39,3 kJ / mol för SORT-1 och för FORCED 360, 60,8 kJ / mol.

Diesel particulate matter (PM) produced from Ultra Low Sulfur Diesel (ULSD), Soy-derived B20 and Animal fat-derived B20 was collected at two engine operating conditions. Gravimetric analysis showed the PM emissions to depend on both fuel and engine operating condition. B20 fuels exhibited higher PM emissions at low load conditions, but lower PM emissions under high load conditions. The differences between the operating conditions were less significant for B20 fuels than for ULSD. Elemental Carbon analysis revealed the B20 PM to contain greater proportions of organic carbon, which may improve diesel particulate filter (DPF) regeneration. Finally, TEM images showed considerable differences between ULSD and B20 soot at low engine loads. The B20 soot displayed a more disordered arrangement of graphene layers. At higher loads, the differences are subtle, but the B20 PM still displayed a more amorphous structure. There was little difference between the Soy and Animal fat-derived B20 soot.