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Modeling and Evaluation of the Olshammar engine. A simulation based approach of a five-stroke turbocharged engine using Siemens Amesim.
(2025) Hansson, Wilhelm; Åberg, Fredrik
Internal combustion engines (ICEs) have been used since the 19th century and remain relevant as of 2025, although the field faces major challenges. The future of ICEs will heavily rely on new inventions and technological advancements. This thesis addresses one such invention: the Olshammar engine, a five-stroke engine concept featuring a lowpressure exhaust cylinder. The purpose of this study is to examine how the Olshammar engine performs in comparison to a conventional four-stroke engine. There are several software tools available for modeling and simulating ICEs, and in this study, Siemens Amesim was used. Initially, a two-cylinder petrol baseline engine was modeled and optimized, providing the reference for modeling the Olshammar engine. The results show that the Olshammar engine reduces brake-specific fuel consumption (BSFC) across the operating range of 2000–5000 rpm, with the largest improvement at 3000 rpm, where BSFC is reduced by approximately 4 %. This corresponds to a fuel conversion efficiency of ηf = 35.2% compared to ηf = 33.7% for the baseline engine. Furthermore, the simulations indicate that the improvement in BSFC can be attributed to the power contribution from the exhaust cylinder, resulting from the recovery of expansion work. Additional assessment of key parameters contributing to performance improvements suggests that tuning the exhaust cylinder offset relative to the combustion cylinders, as well as adjusting the bore-to-stroke ratio, can further enhance overall performance. Siemens Amesim proved to be a well-suited tool for ICE modeling, to the extent that it could replace GTPower in the ICE course at Chalmers in the future. Finally, the findings of this study demonstrate how the design and optimization of the Olshammar engine contribute to improved fuel efficiency compared to conventional four-stroke designs.
Analys och implementering av EMI-reducerande tekniker i DC/DC-omvandlare
(2025) Bälter, Kevin
As electronic systems become increasingly compact and efficient, the demands on
electromagnetic compatibility (EMC) continue to rise. DC-DC converters are a common
source of electromagnetic interference (EMI) in many applications, particularly in automotive
and industrial environments. This study aims to analyze and implement techniques to reduce
conducted EMI in a buck converter. While the requirements defined in the CISPR 25 standard
serve as a reference, meeting the standard was not an explicit objective of this work.
Through simulations in LTspice and practical measurements in an EMC chamber, several
filtering solutions were evaluated, including π-filters, common-mode (CM) and differential mode (DM) filters, as well as complementary techniques such as RC filters, ferrite beads, and
increased input capacitance. The results show that the π-filter provided the most consistent
attenuation across a wide frequency range (150 kHz–80 MHz), while the CM filter performed
better at higher frequencies. The best overall EMI performance was achieved using a
combination of a π-filter, increased input capacitance (320 µF), and a ferrite bead.
The study also demonstrates that filter placement, grounding quality, and parasitic
characteristics of components significantly affect performance. Finally, suggestions for further
improvement are discussed, including the implementation of spread spectrum techniques and
alternative CM filter designs to achieve improved low-frequency suppression.
Analysis of Electric Conductivity Variance in the Insulation of HVDC Cables
(2025) Bhaumik, Palash
Power cables with insulation based on cross-linked polyethylene (XLPE) are used
in high voltage direct current (HVDC) onshore and offshore power grids to transmit
large amounts of electric energy over long distances. One of the important aspects
to be considered when designing the insulation system of such cables is the
variation of the electric conductivity of the insulation material in radial direction
between the energized conductor and grounded screen. Since the conductivity
of XLPE is dependent on electric field strength and temperature, predicting its
actual changes in the cable is challenging and typically is done based on some
empirical formulas. These, however, do not take into account the effect of the
diffusion of impurities and byproducts introduced into the material during the
manufacturing process on conductivity variations.
In the thesis, the electric conductivity of XLPE was measured using material samples
taken from continuous peelings of the insulation of a real cable. This allowed
for examining its field and temperature dependencies at different distances from
the conductor, i.e. at different contents of byproducts. The experimentally obtained
material properties were further utilized as input for a computer model,
which was developed to analyze the dynamics of space charge accumulation and
corresponding electric field in the cable. The results outlined in the thesis are
essential for improving the design rules for HVDC cables to ensure their reliable
and safe operation.
Screening Life Cycle Assessment of Upscaling Structural Battery Composite Production
(2025) Balaji, Suveer
Structural batteries are composite materials which incorporate lithium-ion battery
(LIB) cells to bear mechanical loads as well as receive and release electrical energy.
This multi-functionality of structural batteries helps to reduce weight significantly
as separate entities for structural support and energy storage are not required unlike
in the case of conventional battery technologies. The structural battery is seeing
growing demand in transportation systems, consumer electronics and biomedical
applications. However, the structural battery technology is currently being implemented
only at laboratory scale. The measures and challenges associated with
physically scaling structural battery composite production are uncertain.
This study focuses on evaluating environmental impacts when considering scenarios
related to physically scaling the production of structural battery composites (SBC)
from laboratory scale to pilot scale using screening life cycle assessment (LCA). The
scenarios in relation to varying electrolyte to epoxy resin composition of SBC were
built, developed and analyzed in this study.
The results from modelling of scenarios showed considerable increase in climate
change impacts, ecotoxicity (terrestrial) impacts, ozone depletion, ionising radiation
and water use impacts when structural battery composite production was physically
scaled from laboratory to pilot scale. The environmental hotspots determined from
the study were the use of carbon fibers, production of certain structural electrolyte
constituents, consumption of electricity in production processes as well as electrolyte
infusion and curing processes. The report also explains the gaps in research and recommendations
for future research in relation to scaling SBC production to minimize
environmental impacts associated with these processes.
Single particle characterisation of lipidbased nanoparticles using automated Raman trapping analysis
(2025) Palmgren, Lukas
Liposomes are self-assembled lipid structures comprising a lipid membrane bilayer encapsulating an aqueous core. They have for a long time been acknowledged as appropriate delivery vectors for the delivery of both hydrophobic and hydrophilic cargo. However, they are not able to achieve active targeting of specific cells or tissues. Extracellular vesicles (EVs) are lipid membrane-bound vesicles ranging in diameter from 10s to 1000s of nm which are produced by almost all cells in the body. They have shown effective targeting ability and are innately biocompatible. However, they are heterogeneous and hard to purify in large enough amounts for use in drug delivery. It has been suggested that designing liposomes, which can
mimic extracellular vesicles, might overcome these issues and allow better drug delivery vectors to be designed. In this thesis, a protocol to characterize liposomes on the single particle level was developed, using a single particle automated Raman trapping analysis (SPARTA) instrument which combines Raman spectrometry with optical trapping. As a model system, liposomes of varying lipids with varying degrees of cholesterol were studied, since high cholesterol content has often been reported for extracellular vesicles. This leads to the report having two goals, the first being to optimize and learn SPARTA in order to study particle on a single particle level, with a high throughput. The second goal was to characterize the efficiency of cholesterol encapsulation at high mol % and investigate how cholesterol affects the phase behavior of particles on the single particle level using SPARTA as the main method.
Large unilamellar vesicles were formulated using three different phospholipids DPPC, POPC and DOPC. The difference between the three lipids are the amount of double bond unsaturations on the lipid tails; DPPC have zero, POPC have 1 and DOPC have 2. These three phospholipids were used to formulate vesicles with different amounts of cholesterol ranging from 0-70 mol % cholesterol for each lipid. The different compositions were then studied primarily using SPARTA with verification of lipid phase behavior using small and wide angle X-ray scattering (SAXS/WAXS) as a complimentary method. To experimentally determine maximum encapsulation of cholesterol into DPPC, POPC and DOPC liposomes, liposomes with compositions
ranging from 40-70 mol % cholesterol were also analyzed using 1H − NMR.
Initial experiments allowed the concentration range for single particle measurements to be determined. It was also shown that the particles studied in this thesis were homogeneous in composition, since only the signal intensity decreased upon increasing dilution. Next, it was shown that SPARTA can be used effectively to show cholesterol saturation which was confirmed by proton NMR, and double bond ratio and conformational order which were corroborated with SAXS/WAXS measurements. WAXS also showed formation of cholesterol crystals at higher cholesterol amount. SAXS/WAXS also allowed changes in D-spacing for specific lipid mixtures to be characterized with increased cholesterol. Together, these results showcase the
possibles to characterise lipid vesicles on the single particle level using Raman spectroscopy, and specifically, how the effect of cholesterol on lipid phase behavior can be quantified on a single particle level. The findings here on these model systems allow us to better apply single particle automated Raman trapping analysis to study more complex, biological samples.