<p> In order to investigate possible negative effects of endurance training on muscle strength and power, 10 healthy young men underwent 10 weeks of endurance training. Subjects trained unilaterally on a cycle ergometer so that their opposite leg served as a control. Training consisted of 30 min per day for 3 days per week and progressed to 60 min per day for 5 days per week by the seventh week of training. This volume of endurance training exceeds the upper limits of that normally performed by athletes who compete in power sports. The exercise intensity was initially ~75% of pre-training maximum power output and was increased over time to maintain a training heart rate of 140-160 beats per minute. Endurance, strength, and power variables were assessed in each leg before and after the training period. Measurements included electrically stimulated twitch characteristics of the quadriceps, single-leg V̇O2peak and lactate threshold (Tlac), single-leg take-off vertical jump power indices from a force platform, and maximal leg press strength at a low-(60°/s) and high-velocity (300°/s). Needle biopsies were taken from the quadriceps femoris before and after the training period, and analyzed for fibre-type proportions, fibre area, oxidative enzyme activity and capillary density. Post-training, subjects increased leg V̇O2peak (7%) and Tlac in the trained leg. Leg press strength was unaffected by training. Vertical jump power was not impaired nor were evoked twitches. Following training, there was a decrease in % type IIb and an increase in % type IIa fibres (p<0.05). There were no significant changes in fibre area. Percent fibre area increased for type I and IIa and decreased for type IIb fibres in the trained leg (p<0.05). These data indicate that a 10-week endurance-training program increases aerobic power but does not impair muscle strength or power.</p> / Thesis / Master of Science (MSc)

There has been an ever-increasing demand for power generation, which is predicted to grow as society becomes more advanced. However, tradition fossil fuels are beginning to deplete, and there is a great necessity for alternative fuel sources that will bridge the gap between energy production and consumption. To decrease the high demand alternative fuel sources are gaining in popularity. The supercritical carbon dioxide Brayton power cycle has been proposed as a possible cycle for nuclear and concentrated solar power generation. Two main advantages of having supercritical carbon dioxide are the large property variations and component size associated with power cycle. Forced convection heat transfer of supercritical carbon dioxide in printed circuit heat exchanger geometries were investigated in the following study using a finite volume framework and the FLUENT 12.1 code. The geometries of interest were: non- chamfered zig-zag, chamfered zig-zag, and air foil. Flow through the three geometries was in the horizontal orientation and subject to a heating mode operation. A range of testing conditions were explored, including operating pressures between 7.5 to 10.2 MPa with the mass flux ranging from 326 to 762 kg/m2-s. Due to the turbulent nature of this problem, the k−E with enhanced wall treatment and shear stress transport k−ω turbulence models were considered. With this addition a total of 54 simulations were performed. Results indicated that there was an increase in the heat transfer coefficient as the supercritical carbon dioxide reached the pseudocritical temperature, conversely as there was an increase in operating pressure, the heat transfer coefficient decreased. Nevertheless, this increase near the pseudocritical temperature was due to a sharp increase in the specific heat. Mass flux effects indicated that there was an increase in heat transfer as the mass flux was increased. This was due to the increase in Reynolds number near the pseudocritical temperature. Next, pressure losses were investigated for the three geometries. The non-chamfered zig-zag channel had the greatest pressure loss associated with it, while the air foil channel had the least. Based on the results, the ratio of the friction factor to heat transfer for the non-chamfered and chamfered zig-zag geometries were approximately 2.65 and 1.57 times higher than for the air foil, thus leading to the idea that the air foil channel may be best suited for practical applications. Finally, the simulation results were compared to experimental data and existing correlations. Many existing correlations failed to accurately predict the magnitude of heat transfer, although they exhibited a similar trend. A new correlation was developed for the zig-zag geometries based on the numerical data obtained during this investigation and published experimental data. The new correlation is able to predict the maximum heat transfer coefficient within 12.4%.

This master’s thesis analyses Kalina cycle, a power cycle where ammonia – water solution is used as a working fluid. The first part of this study introduces us to the Kalina cycle, presents its advantages and disadvantages, characteristics of the working fluid and its applications. Second section concerns with the method of cycle design and describes the calculation model made in this thesis. The calculation model is attached in a separate .XLSM file. The third part shows calculation of the cycle for given parameters, determination of cycle efficiency and main proportions of the thermal turbine. In the conclusion are the interpretations of the calculations results.

Internal combustion engines (ICEs) are essential for the welfare of today’s human civilization yet they contribute to almost 10% of the global CO2 emissions. Reducing the carbon footprint of the ICEs can be achieved by either increasing the engine efficiency to reduce fuel consumption or the utilization of carbon-neutral fuels. This dissertation aims to investigate the effect of the oxidizer composition on the efficiency and performance of the homogenous charge compression ignition (HCCI) engine. It also aims to study the behavior of hydrogen in HCCI engines. The experiments are conducted using a Cooperative Fuel Research (CFR) engine. The study also involves using chemical kinetics simulations to estimate the ignition delay time of hydrogen which is relevant to the HCCI mode of combustion. The results suggest that the specific heat ratio of the oxidizer does not significantly affect the HCCI engine efficiency. On the fuel side, hydrogen showed high sensitivity to engine running conditions due to the lack of negative temperature coefficient (NTC).

No description available.

Šiuo darbu siekta išanalizuoti, kaip Kinijos santykinės galios ir vaidmens tendencijų JAV atžvilgiu pasiskirstymas gali lemti įtampą – konfliktą ar taikų sambūvį sistemoje tarp JAV ir Kinijos. Tyrimui taikyta galios ciklo teorija, besiremianti „bendrosios pusiausvyros koncepcija“. Pagrindinis teorijos argumentas teigia, kad stabilumas priklauo nuo dviejų pagrindinių veiksnių: a) ar stiprėjančios valstybės didėjanti santykinė galia yra atsveriama kitų sistemos didižiųjų valstybių santykine galia – t.y. nelemia kritinio taško, lūžio, šiuo atveju sistemos lyderio - JAV, santykinės galios cikle sistemos atžvilgiu; b) ar egzistuoja stiprėjančios valstybės santykinės galios ir santykinio vaidmens ciklų suderinamumas, valstybės su kuria galimos įtampos, atžvilgiu. Siekiant atlikti kiekybinį santykinės galios ir santykinio vaidmens tyrimą, formalus galios ciklo modelis kiek pakoreguotas, pakeičiant santykinės galios operacionalizaciją ir į modelį įtraukiant kiekybinį santykinio vaidmens matavimą. Būtent kiekybinis vaidmens matavimas leido iki galo išpildyti galios ciklo teorijos argumentus, patikrinti tyrimo teiginius bei atmesti abi darbe keltas hipotezes. Įgyvendinus darbe keliamus uždavinius ir pasiekus darbo tikslą, galimos tokios pagrindinės empyrinio tyrimo išvados ir teorinės darbo implikacijos: Akademinėje literatūroje dominuojanti absoliučiais skaičiais vertinama Kinijos galia jau dabartiniu momentu kuria Kinijos galios saugumizavimą ir jos kaip didžiausios grėsmės sistemai... [toliau žr. visą tekstą] / The master thesis ”Shifting Nexus of China-US Power and Role: Power Cycle Theory Application” seeks to analyze how a shifting nexus of China-US relative power and role cycles could cause a tense or peaceful transformation of the system. The research expands more traditional explanations about China’s rise of power and it’s implications to the transformation of the international system. The research is based on power cycle theory developed by Charles Doran and applied for the analysis of the Great Wars in history. The main founding principle of power cycle theory is empirically proved and statistically significant correlation of the critical points in the relative to the system power cycle of growing state and conflicts. It is only one but not sufficient condition for the growing power to start a war as power cycle theory argues. So, in the ”moment of truth” or when a critical point in the relative to the system power cycle of growing state happens, the main condition for the tension or a peaceful international system transition is the nexus of relative to the dominant state power and role cycles of the growing state and the alignment or misbalance between them. Before the power cycle theory to the case of China’s growth and its cause to the international system is applied, some methodological improvements of theory are made: the operationalisation of relative power index is changed and the term “relative role” is operationalised in order to measure it quantitative. A... [to full text]

A combined cycle gas/steam power plant combines a gas turbine (topping cycle) with a steam power plant (bottoming cycle) through the use of a heat recovery steam generator. It uses the hot exhaust of the gas turbine to produce steam which is used to generate additional power in the steam power plant. The aim of this study is to establish the different bottoming cycle performances in terms of the main parameters of heat recovery steam generator and steam cycle for a chosen gas turbine cycle. First of all / for a single steam power cycle, effect of main cycle parameters on cycle performance are analyzed based on first law of thermodynamics. Also, case of existence of a reheater section in a steam cycle is evaluated. For a given gas turbine cycle, three different bottoming cycle configurations are chosen and parametric analysis are carried out based on energy analysis to see the effects of main cycle parameters on cycle performance. These are single pressure cycle, single pressure cycle with supplementary firing and dual pressure cycle. Also, effect of adding a single reheat to single pressure HRSG is evaluated. In single pressure cycle, HRSG generates steam at one pressure level. In dual pressure cycle, HRSG generates steam at two different pressure levels. i.e. high pressure and low pressure. In single pressure cycle with supplementary firing excess oxygen in exhaust gas is fired before entering HRSG by additional fuel input. So, temperature of exhaust gas entering the HRSG rises. Second law analysis is performed to able to see exergy distribution throughout the bottoming plant / furthermore second law efficiency values are obtained for single and dual pressure bottoming cycle configurations as well as basic steam power cycle with and without reheat. It is shown that maximum lost work due to irreversibility is in HRSG for a bottoming cycle in a single pressure gas / steam combined power plant and in boiler for a steam cycle alone. Comparing this with the single pressure cycle shows how the dual pressure cycle makes better use of the exhaust gas in the HRSG that dual pressure combined cycle has highest efficiency values and lost work due to irreversibility in -most significant component- HRSG can be lowered. And also it is shown that by extending the idea of reheat the moisture content is reduced and improvement in the performance is possible for high main steam pressures. Another observation is that supplementary firing increases the steam turbine output compared to the cycle without supplementary firing. The efficiency rises slightly for HP steam pressures higher than 14 MPa at HRSG exit, because the increased steam production also results in increased mass flows removing more energy from the exhaust gas.

There has been renewed significance for innovative energy conversion technologies, particularly the heat recovery-to-power technologies for sustainable power generation from renewable energies and waste heat. This is due to the increasing concern over high demand for electricity, energy shortage, global warming and thermal pollution. Among the innovative heat recovery-to- power technologies, the proposed trilateral flash cycle (TFC) is a promising option, which presents a great potential for development. Unlike the Rankine cycles, the TFC starts the working fluid expansion from the saturated liquid condition rather than the saturated, superheated or supercritical vapour phase, bypassing the isothermal boiling phase. The challenges associated with the need to establish system design basis and facilitate system configuration design-supporting analysis from proof-of-concept towards a market-ready TFC technology are significant. Thus, there is a great need for research to improve the understanding of its operation, behaviour and performance. The objective of this study is to develop and establish simulation tools of the TFCs for improving the understanding of their operation, physics of performance metrics and to evaluate novel system configurations for low-grade heat recovery-to-power generation. This study examined modelling and process simulation of the TFC engines in order to evaluate their performance metrics, predictions for guiding system design and parameters estimations. A detailed thermodynamic analysis, performance optimization and parametric analysis of the cycles were conducted, and their optimized performance metrics compared. These were aimed at evaluating the effects of the key parameters on system performances and to improve the understanding of the performance behaviour. Four distinct system configurations of the TFC, comprising the simple TFC, TFC with IHE, reheat TFC and TFC with feed fluid-heating (or regenerative TFC) were examined. Steady-state steady-flow models of the TFC power plants, corresponding to their thermodynamic processes were thermodynamically modelled and implemented using engineering equation solver (ESS). These models were used to determine the optimum synthesis/ design parameters of the cycles and to evaluate their performance metrics, at the subcritical operating conditions and design criteria. Thus, they can be valuable tools in the preliminary prototype system design of the power plants. The results depict that the thermal efficiencies of the simple TFC, TFC with IHE, reheat TFC and regenerative TFC employing n-pentane are 11.85 - 21.97%, 12.32 - 23.91%, 11.86 - 22.07% and 12.01 - 22.9% respectively over the cycle high temperature limit of 393 - 473 K. These suggest that the integration of an IHE, fluid-feed heating and reheating in optimized design of the TFC engine enhanced the heat exchange efficiencies and system performances. The effects of varying the expander inlet pressure at the cycle high temperature and expander isentropic efficiency on performance metrics of the cycles were significant. They have assisted in selecting the optimum-operating limits for the maximum performance metrics. The thermal efficiencies of all the cycles increased as the inlet pressures increased from 2 - 3 MPa and increased as the expander isentropic efficiencies increased from 50 - 100%, while their exergy efficiencies increased. This is due to increased net work outputs that suggest optimal value of pressure ratios between the expander inlets and their outlets. A comprehensive evaluation depicted that the TFC with IHE attained the best performance metrics among the cycles. This is followed by the regenerative TFC whereas the simple TFC and reheat TFC have the lowest at the same subcritical operating conditions. The results presented show that the performance metrics of the cycles depend on the system configuration, and the operating conditions of the cycles, heat source and heat sink. The results also illustrate how system configuration design and sizing might be altered for improved performance and experimental measurements for preliminary prototype development.

There has been renewed significance for innovative energy conversion technologies, particularly the heat recovery-to-power technologies for sustainable power generation from renewable energies and waste heat. This is due to the increasing concern over high demand for electricity, energy shortage, global warming and thermal pollution. Among the innovative heat recovery-to- power technologies, the proposed trilateral flash cycle (TFC) is a promising option, which presents a great potential for development. Unlike the Rankine cycles, the TFC starts the working fluid expansion from the saturated liquid condition rather than the saturated, superheated or supercritical vapour phase, bypassing the isothermal boiling phase. The challenges associated with the need to establish system design basis and facilitate system configuration design-supporting analysis from proof-of-concept towards a market-ready TFC technology are significant. Thus, there is a great need for research to improve the understanding of its operation, behaviour and performance. The objective of this study is to develop and establish simulation tools of the TFCs for improving the understanding of their operation, physics of performance metrics and to evaluate novel system configurations for low-grade heat recovery-to-power generation. This study examined modelling and process simulation of the TFC engines in order to evaluate their performance metrics, predictions for guiding system design and parameters estimations. A detailed thermodynamic analysis, performance optimization and parametric analysis of the cycles were conducted, and their optimized performance metrics compared. These were aimed at evaluating the effects of the key parameters on system performances and to improve the understanding of the performance behaviour. Four distinct system configurations of the TFC, comprising the simple TFC, TFC with IHE, reheat TFC and TFC with feed fluid-heating (or regenerative TFC) were examined. Steady-state steady-flow models of the TFC power plants, corresponding to their thermodynamic processes were thermodynamically modelled and implemented using engineering equation solver (ESS). These models were used to determine the optimum synthesis/ design parameters of the cycles and to evaluate their performance metrics, at the subcritical operating conditions and design criteria. Thus, they can be valuable tools in the preliminary prototype system design of the power plants. The results depict that the thermal efficiencies of the simple TFC, TFC with IHE, reheat TFC and regenerative TFC employing n-pentane are 11.85 - 21.97%, 12.32 - 23.91%, 11.86 - 22.07% and 12.01 - 22.9% respectively over the cycle high temperature limit of 393 - 473 K. These suggest that the integration of an IHE, fluid-feed heating and reheating in optimized design of the TFC engine enhanced the heat exchange efficiencies and system performances. The effects of varying the expander inlet pressure at the cycle high temperature and expander isentropic efficiency on performance metrics of the cycles were significant. They have assisted in selecting the optimum-operating limits for the maximum performance metrics. The thermal efficiencies of all the cycles increased as the inlet pressures increased from 2 - 3 MPa and increased as the expander isentropic efficiencies increased from 50 - 100%, while their exergy efficiencies increased. This is due to increased net work outputs that suggest optimal value of pressure ratios between the expander inlets and their outlets. A comprehensive evaluation depicted that the TFC with IHE attained the best performance metrics among the cycles. This is followed by the regenerative TFC whereas the simple TFC and reheat TFC have the lowest at the same subcritical operating conditions. The results presented show that the performance metrics of the cycles depend on the system configuration, and the operating conditions of the cycles, heat source and heat sink. The results also illustrate how system configuration design and sizing might be altered for improved performance and experimental measurements for preliminary prototype development.

The world demand for electrical power increasescontinuously, requiring efficient and low-cost methods forpower generation. This thesis investigates two advanced powercycles with mixtures as the working fluid: the Kalina cycle,alternatively called the ammonia-water cycle, and theevaporative gas turbine cycle. These cycles have the potentialof improved performance regarding electrical efficiency,specific power output, specific investment cost and cost ofelectricity compared with the conventional technology, sincethe mixture working fluids enable efficient energyrecovery. This thesis shows that the ammonia-water cycle has a betterthermodynamic performance than the steam Rankine cycle as abottoming process for natural gas-fired gas and gas-dieselengines, since the majority of the ammonia-water cycleconfigurations investigated generated more power than steamcycles. The best ammonia-water cycle produced approximately40-50 % more power than a single-pressure steam cycle and 20-24% more power than a dual-pressure steam cycle. The investmentcost for an ammonia-water bottoming cycle is probably higherthan for a steam cycle; however, the specific investment costmay be lower due to the higher power output. A comparison between combined cycles with ammonia-waterbottoming processes and evaporative gas turbine cycles showedthat the ammonia-water cycle could recover the exhaust gasenergy of a high pressure ratio gas turbine more efficientlythan a part-flow evaporative gas turbine cycle. For a mediumpressure ratio gas turbine, the situation was the opposite,except when a complex ammonia-water cycle configuration withreheat was used. An exergy analysis showed that evaporativecycles with part-flow humidification could recover energy asefficiently as, or more efficiently than, full-flow cycles. Aneconomic analysis confirmed that the specific investment costfor part-flow cycles was lower than for full-flow cycles, sincepart-flow humidification reduces the heat exchanger area andhumidification tower volume. In addition, the part-flow cycleshad lower or similar costs of electricity compared with thefull-flow cycles. Compared with combined cycles, the part-flowevaporative cycles had significantly lower total and specificinvestment costs and lower or almost equal costs ofelectricity; thus, part-flow evaporative cycles could competewith the combined cycle for mid-size power generation. <b>Keywords:</b>power cycle, mixture working fluid, Kalinacycle, ammonia-water mixture, reciprocating internal combustionengine, bottoming cycle, gas turbine, evaporative gas turbine,air-water mixture, exergy