The increased concentration of greenhouse gases in theatmosphere, in particular CO2, is changing the Earth’s climate. Accordingto the Kyoto protocol, where the international community agreedon binding emission targets, developed countries are committedto reduce their greenhouse gas emissions. The increased use ofbiomass in energy systems is an important strategy to reduce CO2emissions. The purpose of this thesis has been toanalyse the opportunities for Sweden to further reduce CO2emissions in the energy system, by rationallyutilising woody biomass energy. The characteristics of currentcommercially operating biofuel-based CHP plants in Sweden aresurveyed and systematically presented. A consistent andtransparent comprehensive reference base for system comparisonsis given. Furthermore, the fuel effectiveness and contributionto CO2reduction is calculated. The governmentalsubsidies of the CHP plants’investment, expressed as costof specific CO2reduction, appears to be low. The competitiveness of biomass-fuelled energy production inrelation to fossil-based production with carbon capture isanalysed, showing that the biomass-fuelled systems provide acompetitive option, in terms of cost of electricity andefficiencies. The remaining Swedish woody biofuel potential ofat least 100 PJ/yr is principally available in regions with abiomass surplus. Transportation is therefore required to enableits utilisation in a further national and international market.Refining the biofuel feedstock to pellets, or even furtherrefining to motor fuels (DME, methanol or ethanol) or power,could facilitate this transport. Different options for fuelrefining are studied and compared. The entire fuel chain, fromfuel feedstock to end users, is considered and CO2emissions are quantified. Substituting fuelpellets for coal appears to be the most costeffectivealternative and shows the largest CO2reduction per energy unit biofuel. Motor fuelsappear more costly and give about half the CO2reduction. Transportation of the upgraded biofuelpellets is highly feasible from CO2emissions point of view and does not constitute ahindrance for further utilisation, i.e. the pellets can betransported over long distances efficiently with only limitedemissions of CO2. Bioenergy utilisation has additional features forenvironmental improvement, apart from the CO2aspect. Waste heat from biofuel-based CHP can becost-effectively used in conjunction with sewage treatment. Theincoming sewage water to the nitrification process can bepreheated with the waste heat, and thereby substantiallyenhance the nitrification and the reduction of ammoniumnitrogen during the winter season. <b>Keywords:</b>CO2reduction, energy system, biofuel, CHP, refining,fuel pellets, ethanol, methanol, DME, fuel substitution, sewagewater, nitrification.

<p>The increased concentration of greenhouse gases in theatmosphere, in particular CO₂, is changing the Earth’s climate. Accordingto the Kyoto protocol, where the international community agreedon binding emission targets, developed countries are committedto reduce their greenhouse gas emissions. The increased use ofbiomass in energy systems is an important strategy to reduce CO₂emissions. The purpose of this thesis has been toanalyse the opportunities for Sweden to further reduce CO₂emissions in the energy system, by rationallyutilising woody biomass energy. The characteristics of currentcommercially operating biofuel-based CHP plants in Sweden aresurveyed and systematically presented. A consistent andtransparent comprehensive reference base for system comparisonsis given. Furthermore, the fuel effectiveness and contributionto CO₂reduction is calculated. The governmentalsubsidies of the CHP plants’investment, expressed as costof specific CO₂reduction, appears to be low.</p><p>The competitiveness of biomass-fuelled energy production inrelation to fossil-based production with carbon capture isanalysed, showing that the biomass-fuelled systems provide acompetitive option, in terms of cost of electricity andefficiencies. The remaining Swedish woody biofuel potential ofat least 100 PJ/yr is principally available in regions with abiomass surplus. Transportation is therefore required to enableits utilisation in a further national and international market.Refining the biofuel feedstock to pellets, or even furtherrefining to motor fuels (DME, methanol or ethanol) or power,could facilitate this transport. Different options for fuelrefining are studied and compared. The entire fuel chain, fromfuel feedstock to end users, is considered and CO₂emissions are quantified. Substituting fuelpellets for coal appears to be the most costeffectivealternative and shows the largest CO₂reduction per energy unit biofuel. Motor fuelsappear more costly and give about half the CO₂reduction. Transportation of the upgraded biofuelpellets is highly feasible from CO₂emissions point of view and does not constitute ahindrance for further utilisation, i.e. the pellets can betransported over long distances efficiently with only limitedemissions of CO₂.</p><p>Bioenergy utilisation has additional features forenvironmental improvement, apart from the CO₂aspect. Waste heat from biofuel-based CHP can becost-effectively used in conjunction with sewage treatment. Theincoming sewage water to the nitrification process can bepreheated with the waste heat, and thereby substantiallyenhance the nitrification and the reduction of ammoniumnitrogen during the winter season.</p><p><b>Keywords:</b>CO₂reduction, energy system, biofuel, CHP, refining,fuel pellets, ethanol, methanol, DME, fuel substitution, sewagewater, nitrification.</p>

Controlled auto-ignition (CAI), also known as HCCI combustion in a gasoline engine has been extensively researched due to their potential of improved engine efficiency and low NOx emission. However, the combustion timing and the phasing of conventional CAI combustion depend on the in-cylinder condition, such as temperature and combustible mixture strength and thus cannot be directly controlled. In this study, direct DME (Dimethyl Ether) injection was adopted to increase the ignitability of premixed gasoline/air charge and to trigger the auto ignition of premixed charge. Re-breathing valve strategies were used to obtain hot internal EGR to eliminate a need of intake heating. Firstly, the pilot valve opening event, including its opening and closing timing, valve lift and dwell duration between the main valve event, was analysed by the WAVE simulation. Based on the analysis a re-breathing cam lobe was manufactured and installed on a Ricardo E6 engine to achieve the intake rebreathing and exhaust rebreathing operations. The intake re-breathing was realised by the pilot intake valve opening during the exhaust stroke and the exhaust re-breathing was achieved by the secondary exhaust valve opening during the intake stroke. Effects of the pilot intake valve open timing, 2nd DME injection timing, split DME injection ratio, air/fuel ratio and compression ratio were examined during the intake rebreathing operation. Then the performance and emission characteristics of DME assisted gasoline CAI combustion were examined during the exhaust re-breathing operation. Finally, results of the intake and exhaust re-rebreathing operations were compared to the conventional SI operation. The experimental study found that both the intake and the exhaust re-breathing operations provided enough heat to initiate DME assisted gasoline CAI combustion. The direct DME injection enabled to control the start of combustion and phasing. The quantity of the first DME injection showed greater effect than its timing, whereas the injection timing of 2nd DME injection had more dominant effect than its quantity. The exhaust re-breathing strategy provided stratified and hotter internal EGR that does not impact negatively on the volumetric efficiency because exhaust gas was re-breathed from the exhaust port during the intake stroke. High load of both CAI and SI baseline operations were limited by knocking combustion and their low load were limited by incomplete combustion. Exhaust re-breathing operation extended substantially the operational range of the DME assisted gasoline CAI combustion. Extremely low NOx emissions were obtained by DME/gasoline CAI operations. Most importantly, the exhaust rebreathing method produced dramatically improved overall efficiency of 43% compared to 28% of SI operation at a typical part-load operation of 4.0-5.0bar IMEP. It was also found that slightly improved efficiency and the extended operation range could be obtained by 33%:67% split DME injection ratio at higher load, while 67%:33% split DME injection ratio at lower load.

This thesis studies algorithms to estimate an aircraft’s position with different information from various radio stations. Because aircrafts both civilian and military are heavily dependant on GNSS signals, it can be interfered from hostile sources. The aircraft shall then be able to navigate without the GNSS signals. This thesis focuses on three radio navigation systems, DME,VOR and TACAN. With the measurements from these three radio stations and measurements from the inertial navigation system one can estimate a position with an estimation filter. In this thesis two types of filters will be used, the linear Kalman filter and the Extended Kalman filter. The linear Kalman filter will be used when converting the TACAN measurements to a pseudo position and the Extended Kalman filter will be used for the DME,VOR and TACAN measurements. The results shows that the converted TACAN measurements and TACAN measurements estimates very well in both north and east direction. When using only DME measurements the filter estimates the position fairly well in the direction towards the station and poorly in the orthogonal direction. For the VOR measurements the filter estimates the position quite poorly in the direction of the radio station and well in the orthogonal direction. In conclusion the converted TACAN measurement and TACAN measurement algorithm can be used for navigation purposes by its own measurements. However, the DME and VOR measurement algorithms need to be combined or using multiple stations at different locations to get better estimates in both directions. All of the filter could use some better tuning to get the optimal filter, but it is not necessary.

Autoignition and oxidation of two Methane (CH4) and Dimethyl Ether (CH3OCH3 or DME) mixtures in air were studied in shock tubes over a wide range of equivalence ratios at elevated temperatures and pressures. These experiments were conducted in the reflected shock region with pressures ranging from 0.8 to 35.7 atmospheres, temperatures ranging from 913 to 1650 K, and equivalence ratios of 2.0, 1.0, 0.5, and 0.3. Ignition delay times were obtained from shock-tube endwall pressure traces for fuel mixtures of CH4/CH3OCH3 in ratios of 80/20 percent volume and 60/40 percent volume, respectively. Close examination of the data revealed that energy release from the mixture is occurring in the time between the arrival of the incident shock wave and the ignition event. An adjustment scheme for temperature and pressure was devised to account for this energy release and its effect on the ignition of the mixture. Two separate ignition delay correlations were developed for these pressure- and temperature-adjusted data. These correlations estimate ignition delay from known temperature, pressure, and species mole fractions of methane, dimethyl ether, and air (0.21 O2 + 0.79 N2). The first correlation was developed for ignition delay occurring at temperatures greater than or equal to 1175 K and pressures ranging from 0.8 to 35.3 atm. The second correlation was developed for ignition delay occurring at temperatures less than or equal to 1175 K and pressures ranging from 18.5 to 40.0 atm. Overall good agreement was found to exist between the two correlations and the data of these experiments. Findings of these experiments also include that with pressures at or below ten atm, increased concentrations of dimethyl ether will consistently produce faster ignition times. At pressures greater than ten atmospheres it is possible for fuel rich mixtures with lower concentrations of dimethyl ether to give the fastest ignition times. This work represents the most thorough shock tube investigation for oxidation of methane with high concentration levels of dimethyl ether at gas turbine engine relevant temperatures and pressures. The findings of this study should serve as a validation for detailed chemical kinetics mechanisms.

Currently extensive research on alternative fuels is being conducted due to their increasing demand to reduce greenhouse emissions. One renewable fuel studied in this work is dimethyl ether (DME) blended with propane(C3H8) as a potential mixture for heavy-duty engines used in semi-trucks. The blend has the potential to drastically reduce particulate and greenhouse gas emissions compared to a conventional diesel engine operating under similar conditions. To develop the use of mixture, one must conduct detailed conceptual and simulation studies before progressing to detail studies in CFD, engine modifications, and live testing. For simulations, accurate high-fidelity chemical kinetic models are necessary. However, the validity of the chemical kinetic mechanism for operating conditions of a heavy-duty mixing-controlled compression (MCCI) engine was widely unknown until recent work presented here and published. In this work, we studied the ignition of DME and propane blends in a shock tube under MCCI engine conditions. Ignition delay time (IDT) gathered behind the reflected shock for DME-propane mixtures for heavy-duty compression ignition (CI) engine parameters. Testing was conducted for undiluted varieties spanning from temperatures of 700 to 1100 K at pressures ranging from 55 to 84 bar for various blends (100% CH3OCH3, 100% C3H8, 60% CH3OCH3/ 40% C3H8) of DME and propane were combusted in synthetic air (21% O2/ 79% N2). Several experiments were conducted at higher pressures (90-120 bar) to improve the model performance and accuracy. The ignition delay times (IDTs) were compared to recent mechanisms, including Aramco3.0, NUIG, and Dames et al. A common trend among the mechanisms was overpredicted experimental IDTs. Further studies were conducted by a sensitivity analysis using the Dames et al. model, and critical reactions sensitive to IDTs of DME-propane mixture near 60 bar are outlined. Chemical analysis was conducted on the NTC region to explain chemical kinetics which is critical for developing MCCI heavy duty engines.

<p>The awareness of the effect emissions have on the environment and climate has risen in the last decades. This has caused strict regulations of greenhouse gas emissions. Greenhouse gases cause global warming which may have devastating environmental effects. Most of the fuels commercially available today are fossil fuels. There are two major effects of using fuels with fossil origin; the source will eventually drain and the usage results in an increase of greenhouse gases in the atmosphere. Fuels that are created from a renewable feedstock are often referred to as alternative fuels and under ideal conditions they are greenhouse gas neutral, meaning that the same amount of greenhouse gases is released during combustion as the source of the fuel have absorbed during its growth period. This evaluation method is known as a well-to-wheel analysis which besides emissions also evaluates energy efficiencies during both the production and the combustion phases.</p><p>By evaluating results of well-to-wheel analyses along with fuel properties and engine concept characteristics, this report presents which driving scenario that is suitable for different powertrain configurations. For example, vehicles operating in high populated areas, as cities, have a driving scenario that includes low velocities and multiple stops while vehicles in low populated areas often travel long distances in higher speeds. This implies that different powertrains are suitable in different regions. By matching favorable properties of a certain powertrain to the properties important to the actual driving scenario this report evolves a fuel infrastructure that is suitable in Sweden.</p>

The awareness of the effect emissions have on the environment and climate has risen in the last decades. This has caused strict regulations of greenhouse gas emissions. Greenhouse gases cause global warming which may have devastating environmental effects. Most of the fuels commercially available today are fossil fuels. There are two major effects of using fuels with fossil origin; the source will eventually drain and the usage results in an increase of greenhouse gases in the atmosphere. Fuels that are created from a renewable feedstock are often referred to as alternative fuels and under ideal conditions they are greenhouse gas neutral, meaning that the same amount of greenhouse gases is released during combustion as the source of the fuel have absorbed during its growth period. This evaluation method is known as a well-to-wheel analysis which besides emissions also evaluates energy efficiencies during both the production and the combustion phases. By evaluating results of well-to-wheel analyses along with fuel properties and engine concept characteristics, this report presents which driving scenario that is suitable for different powertrain configurations. For example, vehicles operating in high populated areas, as cities, have a driving scenario that includes low velocities and multiple stops while vehicles in low populated areas often travel long distances in higher speeds. This implies that different powertrains are suitable in different regions. By matching favorable properties of a certain powertrain to the properties important to the actual driving scenario this report evolves a fuel infrastructure that is suitable in Sweden.

This dissertation develops a systematic targeting method based on the C-H-O ternary diagram for the conceptual design of gasification-based biorefineries. The approach is applied using dimethyl ether (DME) as case study. A stoichiometric equilibrium model is presented for calculation of the C-H-O chemical equilibria to evaluate and predict equilibrium syngas composition, operating temperature, type and amount of oxidant required in biomass gasification. Overall atomic species balances are developed and process targets are plotted on the C-H-O ternary diagram. Sustainability metrics are incorporated to provide useful insights into the efficiency of biorefinery process targets. It was found that syngas at 1200 and 1500 K is predominantly H2 and CO. Moreover, DME biorefineries have two main process targets, based on the indirect and direct synthesis routes. Gasification at 1200 K and 1 atm. using H2O/CO2 = 2.642 (w/w) and H2O/CH4 = 1.645 (w/w) achieved syngas composition targets for the direct and indirect methods respectively. Comparatively, the integrated biorefinery based on indirect route was more efficient, producing 1.903 ton of DME per ton of biomass feedstock. The process is 100% carbon-efficient and recycles 1.025 tons of H2O. / Civil and Chemical Engineering / M. Tech. (Chemical Engineering)

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