The Optimisation of the Draft Tube of a Hydro Power Plant at Off-Design Conditions

Several possible methods of increasing the efficiency and power of hydro power plants by improving the flow passages are investigated in this stydy. The theoretical background of diffuser design and its application to the optimisation of hydraulic turbine draft tubes is presented in the first part of this study. Several draft tube modernisation projects that have been carried out recently are discussed. Also, a method of increasing the efficiency of the draft tube by injecting a high velocity jet into the boundary layer is presented. Methods of increasing the head of a hydro power plant by using an ejector or a jet pump are discussed in the second part of this work. The theoretical principles of various ejector and jet pump types are presented and four different methods of calculating them are examined in more detail. A self-made computer code is used to calculate the gain in the head for two example power plants. Suitable ejector installations for the example plants are also discussed. The efficiency of the ejector power was found to be in the range 6 - 15 % for conventional head increasers, and 30 % for the jet pump at its optimum operating point. In practice, it is impossible to install an optimised jet pump with a 30 % efficiency into the draft tube as this would considerabely reduce the efficiency of the draft tube at normal operating conditions. This demonstrates, however, the potential for improvement which lies in conventional head increaser technology. This study is based on previous publications and on published test results. No actual laboratory measurements were made for this study. Certain aspects of modelling the flow in the draft tube using computational fluid dynamics are discussed in the final part of this work. The draft tube inlet velocity field is a vital boundary condition for such a calculation. Several previously measured velocity fields that have successfully been utilised in such flow calculations are presented herein.

Supplier Energy Audits in Thermal Power Plants

This master’s thesis handles an operating model for an electric equipment supplier conducted sale oriented energy audit for pumping, fan and other motor applications at power plants. The study goes through the largest factors affecting internal electricity use at a power plant, finds an energy audit –like approach for the basis of information gathering and presents the information needed for conducting the analysis. The model is tested in practice at a kraft recovery boiler of a chemical pulping mill. Targets chosen represent some of the largest electric motor applications in the boiler itself and in its fuel handling. The energy saving potential of the chosen targets is calculated by simulating the energy consumption of the alternatives for controlling the targets, and thereafter combining the information with the volume flow duration curve. Results of the research are somewhat divaricated, as all the information needed is not available in the automation system. Some of the targets could be simulated and their energy saving potential calculated quite easily. At some of the targets chosen the monitoring was not sufficient enough for this and additional measurements would have been needed to base the calculations on. In traditional energy audits, energy efficiency of pump and fan applications is not necessarily examined. This means that there are good possibilities for developing the now presented targeted energy audit procedure basis further.

Process intensification: From optimised flow patterns to microprocess technology

This thesis is focused on process intensification. Several significant problems and applications of this theme are covered. Process intensification is nowadays one of the most popular trends in chemical engineering and attempts have been made to develop a general, systematic methodology for intensification. This seems, however, to be very difficult, because intensified processes are often based on creativity and novel ideas. Monolith reactors and microreactors are successful examples of process intensification. They are usually multichannel devices in which a proper feed technique is important for creating even fluid distribution into the channels. Two different feed techniques were tested for monoliths. In the first technique a shower method was implemented by means of perforated plates. The second technique was a dispersion method using static mixers. Both techniques offered stable operation and uniform fluid distribution. The dispersion method enabled a wider operational range in terms of liquid superficial velocity. Using dispersion method, a volumetric gas-liquid mass transfer coefficient of 2 s-1 was reached. Flow patterns play a significant role in terms of the mixing performance of micromixers. Although the geometry of a T-mixer is simple, channel configurations and dimensions had a clear effect on mixing efficiency. The flow in the microchannel was laminar, but the formation of vortices promoted mixing in micro T-mixers. The generation of vortices was dependent on the channel dimensions, configurations and flow rate. Microreactors offer a high ratio of surface area to volume. Surface forces and interactions between fluids and surfaces are, therefore, often dominant factors. In certain cases, the interactions can be effectively utilised. Different wetting properties of solid materials (PTFE and stainless steel) were applied in the separation of immiscible liquid phases. A micro-scale plate coalescer with hydrophilic and hydrophobic surfaces was used for the continuous separation of organic and aqueous phases. Complete phase separation occurred in less than 20 seconds, whereas the separation time by settling exceeded 30 min. Fluid flows can be also intensified in suitable conditions. By adding certain additives into turbulent fluid flow, it was possible to reduce friction (drag) by 40 %. Drag reduction decreases frictional pressure drop in pipelines which leads to remarkable energy savings and decreases the size or number of pumping facilities required, e.g., in oil transport pipes. Process intensification enables operation often under more optimal conditions. The consequent cost savings from reduced use of raw materials and reduced waste lead to greater economic benefits in processing.

Formal Power Analysis of Systems-on-Chip

The design methods and languages targeted to modern System-on-Chip designs are facing tremendous pressure of the ever-increasing complexity, power, and speed requirements. To estimate any of these three metrics, there is a trade-off between accuracy and abstraction level of detail in which a system under design is analyzed. The more detailed the description, the more accurate the simulation will be, but, on the other hand, the more time consuming it will be. Moreover, a designer wants to make decisions as early as possible in the design flow to avoid costly design backtracking. To answer the challenges posed upon System-on-chip designs, this thesis introduces a formal, power aware framework, its development methods, and methods to constraint and analyze power consumption of the system under design. This thesis discusses on power analysis of synchronous and asynchronous systems not forgetting the communication aspects of these systems. The presented framework is built upon the Timed Action System formalism, which offer an environment to analyze and constraint the functional and temporal behavior of the system at high abstraction level. Furthermore, due to the complexity of System-on-Chip designs, the possibility to abstract unnecessary implementation details at higher abstraction levels is an essential part of the introduced design framework. With the encapsulation and abstraction techniques incorporated with the procedure based communication allows a designer to use the presented power aware framework in modeling these large scale systems. The introduced techniques also enable one to subdivide the development of communication and computation into own tasks. This property is taken into account in the power analysis part as well. Furthermore, the presented framework is developed in a way that it can be used throughout the design project. In other words, a designer is able to model and analyze systems from an abstract specification down to an implementable specification.

The Regulation of Skeletal and Cardiac Muscle Blood Flow in Humans. Studies by positron emission tomography with special reference to exercise, adenosine and nitric oxide

Virtually every cell and organ in the human body is dependent on a proper oxygen supply. This is taken care of by the cardiovascular system that supplies tissues with oxygen precisely according to their metabolic needs. Physical exercise is one of the most demanding challenges the human circulatory system can face. During exercise skeletal muscle blood flow can easily increase some 20-fold and its proper distribution to and within muscles is of importance for optimal oxygen delivery. The local regulation of skeletal muscle blood flow during exercise remains little understood, but adenosine and nitric oxide may take part in this process. In addition to acute exercise, long-term vigorous physical conditioning also induces changes in the cardiovasculature, which leads to improved maximal physical performance. The changes are largely central, such as structural and functional changes in the heart. The function and reserve of the heart’s own vasculature can be studied by adenosine infusion, which according to animal studies evokes vasodilation via it’s a_2A receptors. This has, however, never been addressed in humans in vivo and also studies in endurance athletes have shown inconsistent results regarding the effects of sport training on myocardial blood flow. This study was performed on healthy young adults and endurance athletes and local skeletal and cardiac muscle blod flow was measured by positron emission tomography. In the heart, myocardial blood flow reserve and adenosine A_2A receptor density, and in skeletal muscle, oxygen extraction and consumption was also measured. The role of adenosine in the control of skeletal muscle blood flow during exercise, and its vasodilator effects, were addressed by infusing competitive inhibitors and adenosine into the femoral artery. The formation of skeletal muscle nitric oxide was also inhibited by a drug, with and without prostanoid blockade. As a result and conclusion, it can be said that skeletal muscle blood flow heterogeneity decreases with increasing exercise intensity most likely due to increased vascular unit recruitment, but exercise hyperemia is a very complex phenomenon that cannot be mimicked by pharmacological infusions, and no single regulator factor (e.g. adenosine or nitric oxide) accounts for a significant part of exercise-induced muscle hyperemia. However, in the present study it was observed for the first time in humans that nitric oxide is not only important regulator of the basal level of muscle blood flow, but also oxygen consumption, and together with prostanoids affects muscle blood flow and oxygen consumption during exercise. Finally, even vigorous endurance training does not seem to lead to supranormal myocardial blood flow reserve, and also other receptors than A_2A mediate the vasodilator effects of adenosine. In respect to cardiac work, atheletes heart seems to be luxuriously perfused at rest, which may result from reduced oxygen extraction or impaired efficiency due to pronouncedly enhanced myocardial mass developed to excel in strenuous exercise.

Estimation of existing cable systems in generator-busbar unit and choice the optimal solution for its modernization

The aim of this master’s thesis is to develop an algorithm to calculate the cable network for heat and power station CHGRES. This algorithm includes important aspect which has an influence on the cable network reliability. Moreover, according to developed algorithm, the optimal solution for modernization cable system from economical and technical point of view was obtained. The conditions of existing cable lines show that replacement is necessary. Otherwise, the fault situation would happen. In this case company would loss not only money but also its prestige. As a solution, XLPE single core cables are more profitable than other types of cable considered in this work. Moreover, it is presented the dependence of value of short circuit current on number of 10/110 kV transformers connected in parallel between main grid and considered 10 kV busbar and how it affects on final decision. Furthermore, the losses of company in power (capacity) market due to fault situation are presented. These losses are commensurable with investment to replace existing cable system.

Numerical modelling of small supersonic axial flow turbines

Supersonic axial turbine stages typically exhibit lower efficiencies than subsonic axial turbine stages. One reason for the lower efficiency is the occurrence of shock waves. With higher pressure ratios the flow inside the turbine becomes relatively easily supersonic if there is only one turbine stage. Supersonic axial turbines can be designed in smaller physical size compared to subsonic axial turbines of same power. This makes them good candidates for turbochargers in large diesel engines, where space can be a limiting factor. Also the production costs are lower for a supersonic axial turbine stage than for two subsonic stages. Since supersonic axial turbines are typically low reaction turbines, they also create lower axial forces to be compensated with bearings compared to high reaction turbines. The effect of changing the stator-rotor axial gap in a small high (rotational) speed supersonic axial flow turbine is studied in design and off-design conditions. Also the effect of using pulsatile mass flow at the supersonic stator inlet is studied. Five axial gaps (axial space between stator and rotor) are modeled using threedimensional computational fluid dynamics at the design and three axial gaps at the off-design conditions. Numerical reliability is studied in three independent studies. An additional measurement is made with the design turbine geometry at intermediate off-design conditions and is used to increase the reliability of the modelling. All numerical modelling is made with the Navier-Stokes solver Finflo employing Chien’s k ¡ ² turbulence model. The modelling of the turbine at the design and off-design conditions shows that the total-to-static efficiency of the turbine decreases when the axial gap is increased in both design and off-design conditions. The efficiency drops almost linearily at the off-design conditions, whereas the efficiency drop accelerates with increasing axial gap at the design conditions. The modelling of the turbine stator with pulsatile inlet flow reveals that the mass flow pulsation amplitude is decreased at the stator throat. The stator efficiency and pressure ratio have sinusoidal shapes as a function of time. A hysteresis-like behaviour is detected for stator efficiency and pressure ratio as a function of inlet mass flow, over one pulse period. This behaviour arises from the pulsatile inlet flow. It is important to have the smallest possible axial gap in the studied turbine type in order to maximize the efficiency. The results for the whole turbine can also be applied to some extent in similar turbines operating for example in space rocket engines. The use of a supersonic stator in a pulsatile inlet flow is shown to be possible.

Performance of high power fibre laser cutting of thick-section steel and mediumsection aluminium

Cutting of thick section stainless steel and mild steel, and medium section aluminium using the high power ytterbium fibre laser has been experimentally investigated in this study. Theoretical models of the laser power requirement for cutting of a metal workpiece and the melt removal rate were also developed. The calculated laser power requirement was correlated to the laser power used for the cutting of 10 mm stainless steel workpiece and 15 mm mild steel workpiece using the ytterbium fibre laser and the CO2 laser. Nitrogen assist gas was used for cutting of stainless steel and oxygen was used for mild steel cutting. It was found that the incident laser power required for cutting at a given cutting speed was lower for fibre laser cutting than for CO2 laser cutting indicating a higher absorptivity of the fibre laser beam by the workpiece and higher melting efficiency for the fibre laser beam than for the CO2 laser beam. The difficulty in achieving an efficient melt removal during high speed cutting of the 15 mmmild steel workpiece with oxygen assist gas using the ytterbium fibre laser can be attributed to the high melting efficiency of the ytterbium fibre laser. The calculated melt flow velocity and melt film thickness correlated well with the location of the boundary layer separation point on the 10 mm stainless steel cut edges. An increase in the melt film thickness caused by deceleration of the melt particles in the boundary layer by the viscous shear forces results in the flow separation. The melt flow velocity increases with an increase in assist gas pressure and cut kerf width resulting in a reduction in the melt film thickness and the boundary layer separation point moves closer to the bottom cut edge. The cut edge quality was examined by visual inspection of the cut samples and measurement of the cut kerf width, boundary layer separation point, cut edge squareness (perpendicularity) deviation, and cut edge surface roughness as output quality factors. Different regions of cut edge quality in 10 mm stainless steel and 4 mm aluminium workpieces were defined for different combinations of cutting speed and laserpower.Optimization of processing parameters for a high cut edge quality in 10 mmstainless steel was demonstrated

Methods and Models for Accelerating Dynamic Simulation of Fluid Power Circuits

The objective of this dissertation is to improve the dynamic simulation of fluid power circuits. A fluid power circuit is a typical way to implement power transmission in mobile working machines, e.g. cranes, excavators etc. Dynamic simulation is an essential tool in developing controllability and energy-efficient solutions for mobile machines. Efficient dynamic simulation is the basic requirement for the real-time simulation. In the real-time simulation of fluid power circuits there exist numerical problems due to the software and methods used for modelling and integration. A simulation model of a fluid power circuit is typically created using differential and algebraic equations. Efficient numerical methods are required since differential equations must be solved in real time. Unfortunately, simulation software packages offer only a limited selection of numerical solvers. Numerical problems cause noise to the results, which in many cases leads the simulation run to fail. Mathematically the fluid power circuit models are stiff systems of ordinary differential equations. Numerical solution of the stiff systems can be improved by two alternative approaches. The first is to develop numerical solvers suitable for solving stiff systems. The second is to decrease the model stiffness itself by introducing models and algorithms that either decrease the highest eigenvalues or neglect them by introducing steady-state solutions of the stiff parts of the models. The thesis proposes novel methods using the latter approach. The study aims to develop practical methods usable in dynamic simulation of fluid power circuits using explicit fixed-step integration algorithms. In this thesis, twomechanisms whichmake the systemstiff are studied. These are the pressure drop approaching zero in the turbulent orifice model and the volume approaching zero in the equation of pressure build-up. These are the critical areas to which alternative methods for modelling and numerical simulation are proposed. Generally, in hydraulic power transmission systems the orifice flow is clearly in the turbulent area. The flow becomes laminar as the pressure drop over the orifice approaches zero only in rare situations. These are e.g. when a valve is closed, or an actuator is driven against an end stopper, or external force makes actuator to switch its direction during operation. This means that in terms of accuracy, the description of laminar flow is not necessary. But, unfortunately, when a purely turbulent description of the orifice is used, numerical problems occur when the pressure drop comes close to zero since the first derivative of flow with respect to the pressure drop approaches infinity when the pressure drop approaches zero. Furthermore, the second derivative becomes discontinuous, which causes numerical noise and an infinitely small integration step when a variable step integrator is used. A numerically efficient model for the orifice flow is proposed using a cubic spline function to describe the flow in the laminar and transition areas. Parameters for the cubic spline function are selected such that its first derivative is equal to the first derivative of the pure turbulent orifice flow model in the boundary condition. In the dynamic simulation of fluid power circuits, a tradeoff exists between accuracy and calculation speed. This investigation is made for the two-regime flow orifice model. Especially inside of many types of valves, as well as between them, there exist very small volumes. The integration of pressures in small fluid volumes causes numerical problems in fluid power circuit simulation. Particularly in realtime simulation, these numerical problems are a great weakness. The system stiffness approaches infinity as the fluid volume approaches zero. If fixed step explicit algorithms for solving ordinary differential equations (ODE) are used, the system stability would easily be lost when integrating pressures in small volumes. To solve the problem caused by small fluid volumes, a pseudo-dynamic solver is proposed. Instead of integration of the pressure in a small volume, the pressure is solved as a steady-state pressure created in a separate cascade loop by numerical integration. The hydraulic capacitance V/Be of the parts of the circuit whose pressures are solved by the pseudo-dynamic method should be orders of magnitude smaller than that of those partswhose pressures are integrated. The key advantage of this novel method is that the numerical problems caused by the small volumes are completely avoided. Also, the method is freely applicable regardless of the integration routine applied. The superiority of both above-mentioned methods is that they are suited for use together with the semi-empirical modelling method which necessarily does not require any geometrical data of the valves and actuators to be modelled. In this modelling method, most of the needed component information can be taken from the manufacturer’s nominal graphs. This thesis introduces the methods and shows several numerical examples to demonstrate how the proposed methods improve the dynamic simulation of various hydraulic circuits.

Design of marine generators for alternative diesel-electric power systems

This study compares different electric propulsion systems. Results of the analysis of all the advantages and disadvantages of the different propulsion systems are given. This thesis estimates possibilities to apply different diesel-electric propulsion concepts for different vessel types. Small and medium size vessel’s power ranges are studied. The optimal delivery system is chosen. This choice is made on the base of detailed study of the concepts, electrical equipment market and comparison of mass, volume and efficiency parameters. In this thesis three marine generators are designed. They are: salient pole synchronous generator and two permanent magnet synchronous generators. Their electrical, dimensional, cost and efficiency parameters are compared. To understand all the benefits diagrams with these parameters are prepared. Possible benefits and money savings are estimated. As the result the advantages, disadvantages and boundary conditions for the permanent magnet synchronous generator application in marine electric-power systems are found out.

Two-phase flow measurements with spacer grid in a rod bundle geometry

Heat transfer effectiveness in nuclear rod bundles is of great importance to nuclear reactor safety and economics. An important design parameter is the Critical Heat Flux (CHF), which limits the transferred heat from the fuel to the coolant. The CHF is determined by flow behaviour, especially the turbulence created inside the fuel rod bundle. Adiabatic experiments can be used to characterize the flow behaviour separately from the heat transfer phenomena in diabatic flow. To enhance the turbulence, mixing vanes are attached to spacer grids, which hold the rods in place. The vanes either make the flow swirl around a single sub-channel or induce cross-mixing between adjacent sub-channels. In adiabatic two-phase conditions an important phenomenon that can be investigated is the effect of the spacer on canceling the lift force, which collects the small bubbles to the rod surfaces leading to decreased CHF in diabatic conditions and thus limits the reactor power. Computational Fluid Dynamics (CFD) can be used to simulate the flow numerically and to test how different spacer configurations affect the flow. Experimental data is needed to validate and verify the used CFD models. Especially the modeling of turbulence is challenging even for single-phase flow inside the complex sub-channel geometry. In two-phase flow other factors such as bubble dynamics further complicate the modeling. To investigate the spacer grid effect on two-phase flow, and to provide further experimental data for CFD validation, a series of experiments was run on an adiabatic sub-channel flow loop using a duct-type spacer grid with different configurations. Utilizing the wire-mesh sensor technology, the facility gives high resolution experimental data in both time and space. The experimental results indicate that the duct-type spacer grid is less effective in canceling the lift force effect than the egg-crate type spacer tested earlier.

Simulation of wind powered hydraulic heating system

The objective of this master’s thesis was to design and simulate a wind powered hydraulic heating system that can operate independently in remote places where the use of electricity is not possible. Components for the system were to be selected in such a way that the conditions for manufacture, use and economic viability are the as good as possible. Savonius rotor was chosen for wind turbine, due to its low cut in speed and robust design. Savonius rotor produces kinetic energy in wide wind speed range and it can withstand high wind gusts. Radial piston pump was chosen for the flow source of the hydraulic heater. Pump type was selected due to its characteristics in low rotation speeds and high efficiency. Volume flow from the pump is passed through the throttle orifice. Pressure drop over the orifice causes the hydraulic oil to heat up and, thus, creating thermal energy. Thermal energy in the oil is led to radiator where it conducts heat to the environment. The hydraulic heating system was simulated. For this purpose a mathematical models of chosen components were created. In simulation wind data gathered by Finnish meteorological institute for 167 hours was used as input. The highest produced power was achieved by changing the orifice diameter so that the rotor tip speed ratio follows the power curve. This is not possible to achieve without using electricity. Thus, for the orifice diameter only one, the optimal value was defined. Results from the simulation were compared with investment calculations. Different parameters effecting the investment profitability were altered in sensitivity analyses in order to define the points of investment profitability. Investment was found to be profitable only with high average wind speeds.

Kaukolämpöverkon käytön optimointi

Tämän diplomityön tarkoituksena on selvittää mahdollisuuksia Kotkan Energia Oy:n kaukolämpöverkon ja aivan erityisesti sen käytön kehittämiseen. Kaukolämmön optimaalinen toimittaminen on tasapainoilua kaukolämpöveden virtausten ja lämpötilojen välillä. Kaukolämpöverkon käyttöä voidaan parantaa laskemalla syötettävän kaukolämpöveden menolämpötilaa muu tuotanto ja asiakkaiden tarpeet huomioiden. Lämpötiloja laskiessa verkon oikein ajoitettu varaaminen muuttuu entistä tärkeämmäksi tekijäksi, koska sen avulla voidaan vähentää varatehon käyttöä. Alhaisempi menolämpötila laskee kaukolämpöverkon lämpöhäviöitä, mutta lisää kaukolämpöveden virtausta kuluttajien tehontarpeen pysyessä vakiona. Välipumppauksen käyttö sekä matalammat paine-erot laskevat pumppaushäviöitä, mutta työssä tehtyjen havaintojen perusteella selvästi suurin vaikutus kustannuksiin on lämpöhäviöillä. Laitoskäytöstä vastaavat operaattorit ohjaavat myös kaukolämpöverkon käyttöä, mikä tekee heidän toiminnastaan kriittisen tärkeää kaukolämpöverkon käytön optimoinnin kannalta. Kaukolämpöakku havaittiin myös kannattavaksi investoinniksi, joka samalla vähentäisi tuotannon riippuvuutta operaattorien päätöksistä.

Lightweight, liquid-cooled, direct-drive generator for highpower wind turbines: motivation, concept, and performance

Thesis: A liquid-cooled, direct-drive, permanent-magnet, synchronous generator with helical, double-layer, non-overlapping windings formed from a copper conductor with a coaxial internal coolant conduit offers an excellent combination of attributes to reliably provide economic wind power for the coming generation of wind turbines with power ratings between 5 and 20MW. A generator based on the liquid-cooled architecture proposed here will be reliable and cost effective. Its smaller size and mass will reduce build, transport, and installation costs. Summary: Converting wind energy into electricity and transmitting it to an electrical power grid to supply consumers is a relatively new and rapidly developing method of electricity generation. In the most recent decade, the increase in wind energy’s share of overall energy production has been remarkable. Thousands of land-based and offshore wind turbines have been commissioned around the globe, and thousands more are being planned. The technologies have evolved rapidly and are continuing to evolve, and wind turbine sizes and power ratings are continually increasing. Many of the newer wind turbine designs feature drivetrains based on Direct-Drive, Permanent-Magnet, Synchronous Generators (DD-PMSGs). Being low-speed high-torque machines, the diameters of air-cooled DD-PMSGs become very large to generate higher levels of power. The largest direct-drive wind turbine generator in operation today, rated just below 8MW, is 12m in diameter and approximately 220 tonne. To generate higher powers, traditional DD-PMSGs would need to become extraordinarily large. A 15MW air-cooled direct-drive generator would be of colossal size and tremendous mass and no longer economically viable. One alternative to increasing diameter is instead to increase torque density. In a permanent magnet machine, this is best done by increasing the linear current density of the stator windings. However, greater linear current density results in more Joule heating, and the additional heat cannot be removed practically using a traditional air-cooling approach. Direct liquid cooling is more effective, and when applied directly to the stator windings, higher linear current densities can be sustained leading to substantial increases in torque density. The higher torque density, in turn, makes possible significant reductions in DD-PMSG size. Over the past five years, a multidisciplinary team of researchers has applied a holistic approach to explore the application of liquid cooling to permanent-magnet wind turbine generator design. The approach has considered wind energy markets and the economics of wind power, system reliability, electromagnetic behaviors and design, thermal design and performance, mechanical architecture and behaviors, and the performance modeling of installed wind turbines. This dissertation is based on seven publications that chronicle the work. The primary outcomes are the proposal of a novel generator architecture, a multidisciplinary set of analyses to predict the behaviors, and experimentation to demonstrate some of the key principles and validate the analyses. The proposed generator concept is a direct-drive, surface-magnet, synchronous generator with fractional-slot, duplex-helical, double-layer, non-overlapping windings formed from a copper conductor with a coaxial internal coolant conduit to accommodate liquid coolant flow. The novel liquid-cooling architecture is referred to as LC DD-PMSG. The first of the seven publications summarized in this dissertation discusses the technological and economic benefits and limitations of DD-PMSGs as applied to wind energy. The second publication addresses the long-term reliability of the proposed LC DD-PMSG design. Publication 3 examines the machine’s electromagnetic design, and Publication 4 introduces an optimization tool developed to quickly define basic machine parameters. The static and harmonic behaviors of the stator and rotor wheel structures are the subject of Publication 5. And finally, Publications 6 and 7 examine steady-state and transient thermal behaviors. There have been a number of ancillary concrete outcomes associated with the work including the following. X Intellectual Property (IP) for direct liquid cooling of stator windings via an embedded coaxial coolant conduit, IP for a lightweight wheel structure for lowspeed, high-torque electrical machinery, and IP for numerous other details of the LC DD-PMSG design X Analytical demonstrations of the equivalent reliability of the LC DD-PMSG; validated electromagnetic, thermal, structural, and dynamic prediction models; and an analytical demonstration of the superior partial load efficiency and annual energy output of an LC DD-PMSG design X A set of LC DD-PMSG design guidelines and an analytical tool to establish optimal geometries quickly and early on X Proposed 8 MW LC DD-PMSG concepts for both inner and outer rotor configurations Furthermore, three technologies introduced could be relevant across a broader spectrum of applications. 1) The cost optimization methodology developed as part of this work could be further improved to produce a simple tool to establish base geometries for various electromagnetic machine types. 2) The layered sheet-steel element construction technology used for the LC DD-PMSG stator and rotor wheel structures has potential for a wide range of applications. And finally, 3) the direct liquid-cooling technology could be beneficial in higher speed electromotive applications such as vehicular electric drives.

Optimization of a dynamic district heating power plant

The purpose of this Thesis is to find the most optimal heat recovery solution for Wärtsilä’s dynamic district heating power plant considering Germany energy markets as in Germany government pays subsidies for CHP plants in order to increase its share of domestic power production to 25 % by 2020. Different heat recovery connections have been simulated dozens to be able to determine the most efficient heat recovery connections. The purpose is also to study feasibility of different heat recovery connections in the dynamic district heating power plant in the Germany markets thus taking into consideration the day ahead electricity prices, district heating network temperatures and CHP subsidies accordingly. The auxiliary cooling, dynamical operation and cost efficiency of the power plant is also investigated.