In recent decades much effort has gone into reducing particle emissions in the exhaust gases of heavy-duty diesel engines. Engine development has now reached the stage where it is worth to put heavy focus on the contribution of lubricating oil to particulate emissions in order to further reduce these emissions. A literature study demonstrates that the cylinder system is usually the largest source of oil-related particles. Oil consumption in the cylinder can be divided into throw-off effects when inertia forces act on the piston, piston rings and oil; evaporation from hot surfaces; reverse blow-by when gas pressure drives the oil consumption; and top land scraping when oil is scraped off the cylinder liner. The pressure between the compression rings strongly affects the stability and position of the upper compression ring as well as the oil consumption caused by the reverse blow-by. A method to measure the inter-ring pressure was developed and evaluated. The measurements showed that cycle-to-cycle variations were small, but that the inter-ring pressure varied over time. Calculations with AVL Excite Piston and Rings confirmed that ring gap positions can have a major influence on the inter-ring pressure. The measured particle size and number distributions at motoring conditions show interesting and unexpected results. The high number of particles with a diameter of around 100 nm was greatly reduced when the temperature in the diluter was increased. The mean number particle diameter decreased until 10 nm and then became stable independent of further temperature increase. Other authors have found that the small particles (nucleation mode) are reduced and the larger particles (accumulation mode) are more or less unaffected when exhaust gases are heated up and diluted. / QC 20101112

Indiana University-Purdue University Indianapolis (IUPUI) / Stringent regulatory requirements and modern diesel engine technologies have engaged automotive manufacturers and researchers in accurately predicting and controlling diesel engine-out emissions. As a result, engine control systems have become more complex and opaquer, increasing the development time and costs. To address this challenge, Model-based control methods are an effective way to deal with the criticality of the system study and controls. And physics-based combustion engine modeling is a key to achieve it. This thesis focuses on development and validation of a physics-based model for both engine and emissions using model-based design tools from MATLAB & Simulink. Engine model equipped with exhaust gas circulation and variable geometry turbine is adopted from the previously done work which was then integrated with the combustion and emission model that predicts the heat release rates and NOx emission from engine. Combustion model is designed based on the mass fraction burnt from CA10 to CA90 and then NOx predicted using the extended Zeldovich mechanism. The engine models are tuned for both steady state and dynamics test points to account for engine operating range from the performance data. Various engine and combustion parameters are estimated using parameter estimation toolbox from MATLAB and Simulink by applying the least squared solver to minimize the error between measured and estimated variables. This model is validated against the virtual engine model developed in GT-power for Cummins 6.7L turbo diesel engine. To account for the harmonization of the testing cycles to save engine development time globally, a world harmonized stationary cycle (WHSC) is used for the validation. Sub-systems are validated individually as well as in a loop with a complete model for WHSC. Engine model validation showed promising accuracy of more than 88.4 percent on average for the desired parameters required for the NOx prediction. NOx estimation is accurate for the cycle except the warm-up and cool-down phase. However, NOx prediction during these phases is limited due to actual NOx measured data for tuning the model for real-time NOx estimation. Results are summarized at the end to compare the trend of NOx estimation from the developed combustion and emission model to show the accuracy of in-cylinder parameters and required for the NOx estimation.

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. / Ett dieselpartikelfilter fångar partiklar som genereras vid förbränningen i en dieselmotor. En bråkdel av partiklarna består av askbildande material. När den brännbara delen avlägsnas från filtret återstår enbart aska (som inte är brännbar). Ackumuleringen av aska i ett dieselpartikelfilter ökar bränslekonsumtionen och förkortar filtrets livslängd. Studier av askackumulering i dieselpartikelfilter är främst beroende av fälttester, vilket är både kostsamt och tidsintensivt. För att ta fram en mer ekonomisk testmetod, både avseende tid och kostnad, måste askackumuleringen i filtret kunna accelereras. Således genomfördes en litteraturstudie för att fastställa vilka testparametrar som främst påverkar askbildning och depositionsmönster i filter. I enlighet med den målsättningen har arbeten från ett flertal forskare utvärderats och sammanställts till ett designförslag för en testrigg för accelererande askackumulering. Den föreslagna testriggen medger kontroll av avgastemperatur och flöde, sotbildning, sotmorfologi, regenereringsintervall samt hur det askproducerande materialet introduceras. En brännare används för produktion av sot och aska, varefter avgaserna leds till filtret med hjälp av en fläkt. Fläkten motverkar tryckgradienten mellan in- och utloppet,vilket medger ett konstant gasflöde. För en mer precis temperaturkontroll kan en värmare placeras framför filtrets inlopp. Askproduktionsmetoder som kan testas är oljeinjektion ibrännarens flamma, oljeinjektion i gasflödet och slutligen oljeberikat bränsle. Genom att byta en brännare mot en partikelmatare kan riggen även fylla filtret med aska; artificiellt skapad eller alternativt samlad från faktiska filter. Utöver detta presenteras en serie frågeställningar som bör tas i beaktande för att möjliggöra bra specifikation av de ingående komponenterna och -karakterisering. Den föreslagna testriggen är designad utifrån ett modulkoncept, vilket innebär att komponenternas inbördes konfigurering kan varieras för att möjliggöra olika typerav tester och forskningsmål. / Aska

This degree project is focused on the study of the tumble and the swirlmotions, which develop during the intake stroke, inside a cylinder of a Dieselengine.Nowadays, the reduction of fuel consumption and emissions is a primaryaspect for automotive companies, including Scania. Then, an efficient combustionprocess is required, and a fundamental role is played by tumble andswirl motion.These motions have been studied by means of the Particle Image Velocimetry(PIV) technique. In particular, two different cylinder head designshave been investigated, focusing on the structures present in the flow andtheir evolutions inside the cylinder. Finally, these results have been comparedwith LES results, in order to validate the latest. Analysing the swirl motion, it has been possible to identify three mainregions, along the cylinder, characterized by different vortex structures. Inaddition, the velocity field into the entire cylinder volume has been extractedby means of a three-dimensional three-component reconstruction.

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