Modelling of a Hydrogen Catalytic Recombiner for Nuclear Power Plant Containment Studies; Case: Siemens FR90/1-150 Recombiner in TONUS OD Code

Ydinvoimalaitokset on suunniteltu ja rakennettu niin, että niillä on kyky selviytyä erilaisista käyttöhäiriöistä ja onnettomuuksista ilman laitoksen vahingoittumista sekä väestön ja ympäristön vaarantumista. On erittäin epätodennäköistä, että ydinvoimalaitosonnettomuus etenee reaktorisydämen vaurioitumiseen asti, minkä seurauksena sydänmateriaalien hapettuminen voi tuottaa vetyä. Jäädytyspiirin rikkoutumisen myötä vety saattaa kulkeutua ydinvoimalaitoksen suojarakennukseen, jossa se voi muodostaa palavan seoksen ilman hapen kanssa ja palaa tai jopa räjähtää. Vetypalosta aiheutuvat lämpötila- ja painekuormitukset vaarantavat suojarakennuksen eheyden ja suojarakennuksen sisällä olevien turvajärjestelmien toimivuuden, joten tehokas ja luotettava vedynhallintajärjestelmä on tarpeellinen. Passiivisia autokatalyyttisiä vetyrekombinaattoreita käytetäänyhä useammissa Euroopan ydinvoimaitoksissa vedynhallintaan. Nämä rekombinaattorit poistavat vetyä katalyyttisellä reaktiolla vedyn reagoidessa katalyytin pinnalla hapen kanssa muodostaen vesihöyryä. Rekombinaattorit ovat täysin passiivisiaeivätkä tarvitse ulkoista energiaa tai operaattoritoimintaa käynnistyäkseen taitoimiakseen. Rekombinaattoreiden käyttäytymisen tutkimisellatähdätään niiden toimivuuden selvittämiseen kaikissa mahdollisissa onnettomuustilanteissa, niiden suunnittelun optimoimiseen sekä niiden optimaalisen lukumäärän ja sijainnin määrittämiseen suojarakennuksessa. Suojarakennuksen mallintamiseen käytetään joko keskiarvoistavia ohjelmia (Lumped parameter (LP) code), moniulotteisia virtausmalliohjelmia (Computational Fluid Dynamics, CFD) tai näiden yhdistelmiä. Rekombinaattoreiden mallintaminen on toteutettu näissä ohjelmissa joko kokeellisella, teoreettisella tai yleisellä (eng. Global Approach) mallilla. Tämä diplomityö sisältää tulokset TONUS OD-ohjelman sisältämän Siemens FR90/1-150 rekombinaattorin mallin vedynkulutuksen tarkistuslaskuista ja TONUS OD-ohjelmalla suoritettujen laskujen tulokset Siemens rekombinaattoreiden vuorovaikutuksista. TONUS on CEA:n (Commissariat à 1'En¬ergie Atomique) kehittämä LP (OD) ja CFD -vetyanalyysiohjelma, jota käytetään vedyn jakautumisen, palamisenja detonaation mallintamiseen. TONUS:sta käytetään myös vedynpoiston mallintamiseen passiivisilla autokatalyyttisillä rekombinaattoreilla. Vedynkulutukseen vaikuttavat tekijät eroteltiin ja tutkittiin yksi kerrallaan. Rekombinaattoreiden vuorovaikutuksia tutkittaessa samaan tilavuuteen sijoitettiin eri kokoisia ja eri lukumäärä rekombinaattoreita. Siemens rekombinaattorimalli TONUS OD-ohjelmassa laskee vedynkulutuksen kuten oletettiin ja tulokset vahvistavat TONUS OD-ohjelman fysikaalisen laskennan luotettavuuden. Mahdollisia paikallisia jakautumia tutkitussa tilavuudessa ei voitu havaita LP-ohjelmalla, koska se käyttäälaskennassa suureiden tilavuuskeskiarvoja. Paikallisten jakautumien tutkintaan tarvitaan CFD -laskentaohjelma.

Modelling of changes in electricity end-use and their impacts on electricity distribution

The electricity distribution sector will face significant changes in the future. Increasing reliability demands will call for major network investments. At the same time, electricity end-use is undergoing profound changes. The changes include future energy technologies and other advances in the field. New technologies such as microgeneration and electric vehicles will have different kinds of impacts on electricity distribution network loads. In addition, smart metering provides more accurate electricity consumption data and opportunities to develop sophisticated load modelling and forecasting approaches. Thus, there are both demands and opportunities to develop a new type of long-term forecasting methodology for electricity distribution. The work concentrates on the technical and economic perspectives of electricity distribution. The doctoral dissertation proposes a methodology to forecast electricity consumption in the distribution networks. The forecasting process consists of a spatial analysis, clustering, end-use modelling, scenarios and simulation methods, and the load forecasts are based on the application of automatic meter reading (AMR) data. The developed long-term forecasting process produces power-based load forecasts. By applying these results, it is possible to forecast the impacts of changes on electrical energy in the network, and further, on the distribution system operator’s revenue. These results are applicable to distribution network and business planning. This doctoral dissertation includes a case study, which tests the forecasting process in practice. For the case study, the most prominent future energy technologies are chosen, and their impacts on the electrical energy and power on the network are analysed. The most relevant topics related to changes in the operating environment, namely energy efficiency, microgeneration, electric vehicles, energy storages and demand response, are discussed in more detail. The study shows that changes in electricity end-use may have radical impacts both on electrical energy and power in the distribution networks and on the distribution revenue. These changes will probably pose challenges for distribution system operators. The study suggests solutions for the distribution system operators on how they can prepare for the changing conditions. It is concluded that a new type of load forecasting methodology is needed, because the previous methods are no longer able to produce adequate forecasts.

Modelling of vegetative filter strips in catchment scale erosin control

Selostus: Valuma-aluetason mallisovellus suojakaistojen käytöstä eroosion torjunnassa

Numerical Modelling of Combustion and Emission Formation in a Diesel Engine with Different Fuel Injection Characteristics

Päästöjen vähentäminen on ollut viime vuosina tärkeässä osassa polttomoottoreita kehitettäessä.Monet viralliset tahot asettavat uusia tiukempia päästörajoituksia. Päästörajatovat tyypillisesti olleet tiukimmat autoteollisuuden valmistamille pienille nopeakäyntisille diesel-moottoreille, mutta viime aikoina paineita on kohdistunut myös suurempiin keskinopeisiin ja hidaskäyntisiin diesel-moottoreihin. Päästörajat ovat erilaisia riippuen moottorin tyypistä, käytetystä polttoaineesta ja paikasta missä moottoria käytetään johtuen erilaisista paikallisista laeista ja asetuksista. Eniten huomiota diesel-moottorin päästöissä täytyy kohdistaa typen oksideihin, savun muodostukseen sekä partikkeleihin. Laskennallisen virtausmekaniikan (CFD) avulla on hyvät mahdollisuudet tutkia diesel-moottorin sylinterissä tapahtuvia ilmiöitä palamisen aikana. CFD on hyödyllinen työkalu arvioitaessa moottorin suorituskykyä ja päästöjen muodostumista. CFD:llä on mahdollista testata erilaisten parametrien ja geometrioiden vaikutusta ilman kalliita moottorinkoeajoja. CFD:tä voidaan käyttää myös opetustarkoituksessa lisäämään paloprosessin tuntemusta. Tulevaisuudessa palamissimuloinnit CFD:llä tulevat epäilemättä olemaan tärkeä osa moottorin kehityksessä. Tässä diplomityössä on tehty palamissimuloinnit kahteen erilaisilla poittoaineenruiskutuslaitteistoilla varustettuun Wärtsilän keskinopeaan diesel-moottoriin. W46 moottorin ruiskutuslaitteisto on perinteinen mekaanisesti ohjattu pumppusuutin ja W46-CR moottorissa on elektronisesti ohjattu 'common rail' ruiskutuslaitteisto. Näiden moottorien ja käytössä olevien ruiskutusprofiilien lisäksi on simuloinneilla testattu erilaisia uusia ruiskutusprofiileja, jotta erityyppisten profiilien hyvät ja huonot ominaisuudet tulisivat selville. Matalalla kuormalla kiinnostuksen kohteena on nokipäästöjen muodostus ja täydellä kuormalla NOx-päästöjen muodostus ja polttoaineen kulutus. Simulointien tulokset osoittivat, että noen muodostusta matalalla kuormalla voidaan selvästi vähentää monivaiheisella ruiskutuksella, jossa yksi ruiskutusjakso jaetaan kahteen tai useampaan jaksoon. Erityisen tehokas noen vähentämisessä vaikuttaa olevan ns. jälkiruiskutus (post injection). Matalat NOx-päästöt ja hyvä polttoaineen kulutus täydellä kuormalla on mahdollista saavuttaaasteittain nostettavalla ruiskutusnopeudella.

Object-Oriented Modelling of Multilayer Networks

Tämä diplomityökuuluu tietoliikenneverkkojen suunnittelun tutkimukseen ja pohjimmiltaan kohdistuu verkon mallintamiseen. Tietoliikenneverkkojen suunnittelu on monimutkainen ja vaativa ongelma, joka sisältää mutkikkaita ja aikaa vieviä tehtäviä. Tämä diplomityö esittelee ”monikerroksisen verkkomallin”, jonka tarkoitus on auttaa verkon suunnittelijoita selviytymään ongelmien monimutkaisuudesta ja vähentää verkkojen suunnitteluun kuluvaa aikaa. Monikerroksinen verkkomalli perustuu yleisille objekteille, jotka ovat yhteisiä kaikille tietoliikenneverkoille. Tämä tekee mallista soveltuvan mielivaltaisille verkoille, välittämättä verkkokohtaisista ominaisuuksista tai verkon toteutuksessa käytetyistä teknologioista. Malli määrittelee tarkan terminologian ja käyttää kolmea käsitettä: verkon jakaminen tasoihin (plane separation), kerrosten muodostaminen (layering) ja osittaminen (partitioning). Nämä käsitteet kuvataan yksityiskohtaisesti tässä työssä. Monikerroksisen verkkomallin sisäinen rakenne ja toiminnallisuus ovat määritelty käyttäen Unified Modelling Language (UML) -notaatiota. Tämä työ esittelee mallin use case- , paketti- ja luokkakaaviot. Diplomityö esittelee myös tulokset, jotka on saatu vertailemalla monikerroksista verkkomallia muihin verkkomalleihin. Tulokset osoittavat, että monikerroksisella verkkomallilla on etuja muihin malleihin verrattuna.

Visual Measurement and Modelling of Tool Wear in Rough Turning

Huolimatta korkeasta automaatioasteesta sorvausteollisuudessa, muutama keskeinen ongelma estää sorvauksen täydellisen automatisoinnin. Yksi näistä ongelmista on työkalun kuluminen. Tämä työ keskittyy toteuttamaan automaattisen järjestelmän kulumisen, erityisesti viistekulumisen, mittaukseen konenäön avulla. Kulumisen mittausjärjestelmä poistaa manuaalisen mittauksen tarpeen ja minimoi ajan, joka käytetään työkalun kulumisen mittaukseen. Mittauksen lisäksi tutkitaan kulumisen mallinnusta sekä ennustamista. Automaattinen mittausjärjestelmä sijoitettiin sorvin sisälle ja järjestelmä integroitiin onnistuneesti ulkopuolisten järjestelmien kanssa. Tehdyt kokeet osoittivat, että mittausjärjestelmä kykenee mittaamaan työkalun kulumisen järjestelmän oikeassa ympäristössä. Mittausjärjestelmä pystyy myös kestämään häiriöitä, jotka ovat konenäköjärjestelmille yleisiä. Työkalun kulumista mallinnusta tutkittiin useilla eri menetelmillä. Näihin kuuluivat muiden muassa neuroverkot ja tukivektoriregressio. Kokeet osoittivat, että tutkitut mallit pystyivät ennustamaan työkalun kulumisasteen käytetyn ajan perusteella. Parhaan tuloksen antoivat neuroverkot Bayesiläisellä regularisoinnilla.

Modelling of North-West Russian market behavior considering technical restrictions of transmission grid

Nowadays the Finnish-Russian electric energy interaction is carried out through the back-to-back DC Vyborg substation and several power plants working synchronously with Finnish power system. Constant amount of energy flows in one direction — from Russia to Finland. But the process of electricity market development in Russian energy system makes the new possibilities of electrical cooperation available. The goal of master's thesis is to analyze the current state and possible evolution trends of North-West Russian system in relation with future possible change in power flow between Russia and Finland. The research is done by modelling the market of North-West Russia and examination of technical grid restrictions. The operational market models of North-West region of Russia for the years 2008 and 2015 were created during the research process. The description of prepared market models together with modelling results and their analysis are shown in the work. The description of power flow study process and results are also presented.

The evaluation of hazardous gas components caused by the thermal degradation of plant oils and animal fats

Neste Oil has introduced plant oils and animal fats for the production of NExBTL renewable diesel, and these raw materials differ from the conventional mineral based oils. One subject of new raw materials study is thermal degradation, or in another name pyrolysis, of these organic oils and fats. The aim of this master’s thesis is to increase knowledge on thermal degradation of these new raw materials, and to identify possible gaseous harmful thermal degradation compounds. Another aim is to de-termine the health and environmental hazards of identified compounds. One objective is also to examine the formation possibilities of hazardous compounds in the produc-tion of NExBTL-diesel. Plant oils and animal fats consist mostly of triglycerides. Pyrolysis of triglycerides is a complex phenomenon, and many degradation products can be formed. Based on the literature studies, 13 hazardous degradation products were identified, one of which was acrolein. This compound is very toxic and dangerous to the environment. Own pyrolysis experiments were carried out with rapeseed and palm oils, and with a mix-ture of palm oil and animal fat. At least 12 hazardous compounds, including acrolein, were analysed from the gas phase. According to the experiments, the factors which influence on acrolein formation are the time of the experiment, the sphere (air/hydrogen) in which the experiment is carried out, and the characteristics of the used oil. The production of NExBTL-diesel is not based on pyrolysis. This is why thermal degradation is possible only when abnormal process conditions prevail.

Ultrafine grinding of FGD and phosphogypsum with an attrition bead mill and a jet mill : optimisation and modelling of grinding and mill comparison

Fine powders of minerals are used commonly in the paper and paint industry, and for ceramics. Research for utilizing of different waste materials in these applications is environmentally important. In this work, the ultrafine grinding of two waste gypsum materials, namely FGD (Flue Gas Desulphurisation) gypsum and phosphogypsum from a phosphoric acid plant, with the attrition bead mill and with the jet mill has been studied. The ' objective of this research was to test the suitability of the attrition bead mill and of the jet mill to produce gypsum powders with a particle size of a few microns. The grinding conditions were optimised by studying the influences of different operational grinding parameters on the grinding rate and on the energy consumption of the process in order to achieve a product fineness such as that required in the paper industry with as low energy consumption as possible. Based on experimental results, the most influential parameters in the attrition grinding were found to be the bead size, the stirrer type, and the stirring speed. The best conditions, based on the product fineness and specific energy consumption of grinding, for the attrition grinding process is to grind the material with small grinding beads and a high rotational speed of the stirrer. Also, by using some suitable grinding additive, a finer product is achieved with a lower energy consumption. In jet mill grinding the most influential parameters were the feed rate, the volumetric flow rate of the grinding air, and the height of the internal classification tube. The optimised condition for the jet is to grind with a small feed rate and with a large rate of volumetric flow rate of grinding air when the inside tube is low. The finer product with a larger rate of production was achieved with the attrition bead mill than with the jet mill, thus the attrition grinding is better for the ultrafine grinding of gypsum than the jet grinding. Finally the suitability of the population balance model for simulation of grinding processes has been studied with different S , B , and C functions. A new S function for the modelling of an attrition mill and a new C function for the modelling of a jet mill were developed. The suitability of the selected models with the developed grinding functions was tested by curve fitting the particle size distributions of the grinding products and then comparing the fitted size distributions to the measured particle sizes. According to the simulation results, the models are suitable for the estimation and simulation of the studied grinding processes.

Modelling of the PWR PACTEL vertical steam generator with the TRACE code

The behavior of the nuclear power plants must be known in all operational situations. Thermal hydraulics computer applications are used to simulate the behavior of the plants. The computer applications must be validated before they can be used reliably. The simulation results are compared against the experimental results. In this thesis a model of the PWR PACTEL steam generator was prepared with the TRAC/RELAP Advanced Computational Engine computer application. The simulation results can be compared against the results of the Advanced Process Simulator analysis software in future. Development of the model of the PWR PACTEL vertical steam generator is introduced in this thesis. Loss of feedwater transient simulation examples were carried out with the model.

Thermal modelling of semiconductor switches in three-level Neutral Point Clamped Medium Voltage DTC-inverter

The aim of this thesis is to investigate the thermal loading of medium voltage three-level NPC inverter’s semiconductor IGCT switches in different operation points. The objective is to reach both a fairly accurate off-line simulation program and also so simple a simulation model that its implementation into an embedded system could be reasonable in practice and a real time use should become feasible. Active loading limitation of the inverter can be realized with a thermal model which is practical in a real time use. Determining of the component heating has been divided into two parts; defining of component losses and establishing the structure of a thermal network. Basics of both parts are clarified. The simulation environment is Matlab-Simulink. Two different models are constructed – a more accurate one and a simplified one. Potential simplifications are clarified with the help of the first one. Simplifications are included in the latter model and the functionalities of both models are compared. When increasing the calculation time step a decreased number of considered components and time constants of the thermal network can be used in the simplified model. Heating of a switching component is dependent on its topological position and inverter’s operation point. The output frequency of the converter defines mainly which one of the switching components is – because of its losses and heating – the performance limiting component of the converter. Comparison of results given by different thermal models demonstrates that with larger time steps, describing of fast occurring switching losses becomes difficult. Generally articles and papers dealing with this subject are written for two-level inverters. Also inverters which apply direct torque control (DTC) are investigated rarely from the heating point of view. Hence, this thesis completes the former material.

Demographic Modelling of Human Population Growth

This work presents models and methods that have been used in producing forecasts of population growth. The work is intended to emphasize the reliability bounds of the model forecasts. Leslie model and various versions of logistic population models are presented. References to literature and several studies are given. A lot of relevant methodology has been developed in biological sciences. The Leslie modelling approach involves the use of current trends in mortality,fertility, migration and emigration. The model treats population divided in age groups and the model is given as a recursive system. Other group of models is based on straightforward extrapolation of census data. Trajectories of simple exponential growth function and logistic models are used to produce the forecast. The work presents the basics of Leslie type modelling and the logistic models, including multi- parameter logistic functions. The latter model is also analysed from model reliability point of view. Bayesian approach and MCMC method are used to create error bounds of the model predictions.

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.

Towards input/output-free modelling of linear infinite-dimensional systems in continuous time

This dissertation describes a networking approach to infinite-dimensional systems theory, where there is a minimal distinction between inputs and outputs. We introduce and study two closely related classes of systems, namely the state/signal systems and the port-Hamiltonian systems, and describe how they relate to each other. Some basic theory for these two classes of systems and the interconnections of such systems is provided. The main emphasis lies on passive and conservative systems, and the theoretical concepts are illustrated using the example of a lossless transfer line. Much remains to be done in this field and we point to some directions for future studies as well.