The aim of this thesis is to increase engine efficiency by studying the flow structures created in an engine cylinder during the intake phase and the effect of the subsequent compression. The invention of the combustion engine has enabled three centuries of economic growth fueled by energy stored as hydrocarbons. However, during the latter part of the twentieth century negative consequences on health and environment of the combustion engine were observed. In order to reduce emissions without increasing fuel consumption, improved knowledge of all physical processes occurring in the engine are necessary. The aim of this thesis is to increase the understanding of the flow prior to combustion, which can lead to reduced engine emissions and fuel consumption. Intake flow structures are studied using large eddy simulations and experiments on a steady swirl test rig. Flow acceleration was observed to reduce the swirl coefficient, and higher swirl coefficient was found during valve closing as compared to during valve opening. This implies that the rotation is stronger during the later part of the intake then what has been previously assumed. In addition, the computations show that the volume above the valves has a profound effect on the swirl created during the intake. To take this into account a novel way of calculating the swirl number was suggested. This approach gives a lower swirl number as compared to the commonly used Thien methodology. The effects of compression are studied using simulations of predefined flow structures undergoing compression. The peak turbulence levels were found to be increasing with tumble number and decreasing with swirl. It was noted that compression increased the turbulent fluctuations in the cylinder axis leading to anisotropic turbulence and that a small tilt angle was observed to have a significant effect on swirl homogeneity at top dead center.  In this thesis, a new methodology was proposed and validated for calculation of in-cylinder turbulence for a flat piston. The results of the thesis enhance the understanding of the dynamic effects encountered during intake as well recognizing that a small tumble component has a strong effect on the flow structures prior to combustion. These results can be used to improve the simplified computational methods used to optimize the engine. / <p>QC 20150420</p>

By using the children's own thoughts and stories this theses aim to investigate and illustrate the phenomenon of rough and tumble play and its existence among five year olds in preschool.     The formulations of the questions are: What do children consider as rough and tumble play? - and what characterise that? From without a perspective of rough and tumble play, which kinds of rough and tumble play do the children play in preschool? - and how do those characterise? What makes rough and tumble play possible and accepted for the children to play in preschool? In this thesis I have investigated the questions above by interviewing 11 five years olds about how they consider rough and tumble play in preschool. From without Birgitta Knutsdotter Olofsson's and Torben Hangaard Rasmussen's view about play and rough and tumble play I created a perspective of rough and tumble play, which I used for analyzing the empirics. With rough and tumble play I mean games or plays that includes wrestling, hitting, kicking, pushing, chasing, running or/and the use of weapons against other human beings or other visualized beings or/and human beings. The conclusions are that children has many different opinions of what rough and tumble play is. Depends on who you are asking you will get a different perspective. The conclusions also shows that rough and tumble play can exist, not just by its self, but also in interplay with other kinds of games and plays. The children are using different strategies to make the rough and tumble play fit the restrictions put on by the educators in the preschool.

Uppsatsens syfte är att undersöka 4-5åringars meningsskapande och uppfattning om fysisk lek i förskolan. Utifrån empiri baserad på deltagande observationer och intervjuer tolkas resultatet med barndomssociologisk utgångspunkt och undersöker hur agens görs i en kategori av lek som ofta övervakas, begränsas och undviks i förskolan – fysisk lek. Empirin inrymmer deltagande i, observerande av, samtal om, reflekterande kring och planerande av fysisk lek såväl inom- som utomhus. Resultatet presenteras utifrån jagalek och visar att pedagoger med fysisk kapacitet värdesätts för ökad spänning och utmaningen samt att barn har kollektiva och individuella strategier för att möjliggöra fysisk lek efter egna önskemål. Ett ytterligare resultat visar på att barn har strategier att tilldela och reducerar vuxnas makt i lek. Det behövs mer forskning om fysisk lek, dels då det saknas begrepp som gör den talbar och dels utifrån dess marginaliserade position inom lekforskningen.

<p>Two-stroke, opposed piston engines have gained recent attention for their improved thermal efficiency relative to the conventional inline or V-configuration. One advantage of two-stroke, opposed piston engines is a reduction in heat losses since there is no cylinder head. Another advantage is improved gas exchange via uniflow scavenging since the exhaust and intake ports may be located near bottom dead center of the exhaust and intake pistons, respectively. One challenge with the design of two-stroke engines is promoting turbulence within the cylinder. Turbulence is important for mixing air and fuel in the cylinder and for increasing flame speed during combustion. </p> <p>This work investigates the flow and turbulence through two-stroke, opposed piston engines using computational fluid dynamics (CFD). Specifically, the role of intake manifold and intake port geometry on turbulence within the cylinder was investigated by systematically modifying the engine geometry. Turbulence was then quantified using three metrics: circulation around the cylinder axis (swirl), circulation normal to the cylinder axis (tumble), and volume average turbulent kinetic energy (TKE) within the cylinder.</p> Increasing the swirl angle from 0 degrees to 10 degrees increased the in-cylinder swirl by a factor of 3. Increasing the swirl angle also increased the volume average TKE by a range of 7.6% to 36.5% across the three cylinders of the engine. A reverse tilt angle of 15 degrees increased tumble circulation near the piston face but decreased tumble circulation by a factor of 3 near the center of the cylinder. The next step for research on this would be to apply more geometric manipulations to the manifold of the swirl engine design to balance the mass flow rate for each port. Following the redesign of the manifold the next step is to perform a dynamic CFD test to verify the mass flow has been balanced under a dynamic scenario.

Syftet med denna intervjustudie var att undersöka fritidshemslärarens förståelse av och inställning till fenomenet bråklek. Studien avsåg även att ta reda på vilka faktorer som kan vara avgörande för denna inställning till bråkleken. Bråkleken beskrivs i studien som en grupporienterad och pedagogisk lekpraktik sett utifrån ett sociokulturellt perspektiv där analysmetoden av de svar som gavs av de fem respondenterna i studien baserades i fenomenografisk förhållningsätt.  Resultatet av studiens indikerar att inställningen bland de tillfrågade fritidshemsläraren att tillåta bråklek i skolverksamheten, är något större än inställningen att motverka den. Vidare förefaller det finnas ett samband mellan fritidshemslärarens inställning och förståelse till bråkleken och tiden som denne spenderat i yrket. Det framstår också som att manliga lärare som deltagit i studien tenderar att vara något mer tillåtande till bråkleken än kvinnliga lärare.

The purpose of this study is to look at how different preschool educators define Rough and Tumble Play (RTP). We want to examine through empirical studies-what approach educators have when confronted with RTP, how they acknowledge these games and what role educators consider they have when acknowledging these games. We also want to look at if educators work actively with RTP, if preschools have active discussions about RTP or a more preventative approach with the play. Our methods are semi structured qualitative interviews with educators from different preschools around the Stockholm district. The aim of our semi structured qualitative questions are to be able to ask follow-up questions for a broader perspective of the respondents perception. We used sound recordings of the respondents answers and transcribed it into a text format to be able to analyse it.   The studies we looked at are Scandinavian and international studies that examined what RTP is, what benefits it might have for children and if there are any disadvantages to children engaging in a more aggressive form of RTP.  Our results show that how research and RTP is perceived in practice varies. While studies and research point more towards different benefits for children engaging in RTP, our respondents do not perceive it as a real play but more as a dangerous activity that might eventually physically harm the children. The respondents also expressed worries for children who have difficulty interpreting social codes and engaging in RTP and also what values are encouraged if RTP is allowed in preschools.

This degree project is focused on the study of the tumble and the swirlmotions, which develop during the intake stroke, inside a cylinder of a Dieselengine.Nowadays, the reduction of fuel consumption and emissions is a primaryaspect for automotive companies, including Scania. Then, an efficient combustionprocess is required, and a fundamental role is played by tumble andswirl motion.These motions have been studied by means of the Particle Image Velocimetry(PIV) technique. In particular, two different cylinder head designshave been investigated, focusing on the structures present in the flow andtheir evolutions inside the cylinder. Finally, these results have been comparedwith LES results, in order to validate the latest. Analysing the swirl motion, it has been possible to identify three mainregions, along the cylinder, characterized by different vortex structures. Inaddition, the velocity field into the entire cylinder volume has been extractedby means of a three-dimensional three-component reconstruction.

Leken anses vara en viktig del av barnkulturen och det framhålls i både förskolans läroplan och forskning om hur leken är en betydelsefull del av barns utveckling och lärande. Bråklekar är en del av barnens lek och uppkommer vardagligen i förskolans verksamhet. Hur pedagoger bemöter och hanterar bråklekar kan variera vilket gjorde att vi intresserade oss för hur pedagoger förhåller sig till bråklekar i förskolan. Syftet med den här studien är att studera hur pedagoger förhåller sig till och hanterar bråklekar i förskolan. Frågeställningar som kommer besvaras är vad bråklekar är och hur de kommer till uttryck samt hur pedagogers förhållningssätt till bråklekar ser ut. Vi har valt att utgå ifrån en kvalitativ metod och utfört deltagande observationer samt intervjuer för att undersöka pedagogers förhållningssätt till bråklekar i förskolan. Resultatet i studien visar på att pedagogers förhållningssätt till bråklekar i förskolan är varierande och kan bero på pedagogers olika erfarenheter, kunskaper och intressen. Vi har kommit fram till att pedagoger har svårt för att arbeta med bråklekar i förskolan eftersom bråklekar är mindre omtyckta av föräldrar, pedagoger och samhället. Anledningen till att bråklekar uppkommer kan bero på att barnen får för lite stimulering och att miljön saknar utrymme inomhus på förskolan. Under utomhusobservationer upptäcktes att mindre konflikter uppstod och att pedagogerna tillät mer fysiska lekar jämfört med inomhus. / Playing is considered an important part of children's culture, and it is emphasized in both the pre-school curriculum and research on how play is an important part of children's development and learning. Rough and tumble is a part of children's play and occur everyday in pre-school activities. How pedagogues handle and deal with rough and tumble play can vary, which made us interested in how pedagogues relate to rough and tumble play in preschool. The purpose of this research is to study how pedagogues relate to and handle rough and tumble play in pre-school. Questions that will be answered are what rough and tumble is, how it looks like and how pedagogues approach to rough and tumble play. We have chosen to base our study on a qualitative method and conducted observations as well as interviews to investigate pedagogues approaches to rough and tumble play in pre-schools. The result of the study shows that pedagogues approach to rough and tumble play in pre-school is varied and may depend on pedagogues different experiences, knowledges and interests. We have come to the conclusion that pedagogues are struggling to work with rough and tumble play in preschool, because it is less popular with parents, educators and society. The reason for why rough and tumble play occur may be due to the fact that the children get too little stimulation and that the environment lacks space indoors at the preschool. During outdoor observations we discovered that less conflicts occurred and that the pedagogues allowed more physical play than indoors.

Com o crescente aumento dos problemas ambientais relacionados à emissão de poluentes, normas cada vez mais rigorosas estão sendo implementadas para diminuir a emissão de gases nocivos provenientes da queima de hidrocarbonetos em motores de combustão interna. Um importante fator que influencia na geração de gases poluentes em motores é o comportamento do escoamento no cilindro, desde o início da admissão até a fase de combustão. O presente trabalho realiza um estudo numérico com validação experimental do escoamento no motor Honda GX35, considerando diversas aberturas de válvula fixas e diferenças de pressão para gerar o escoamento. A validação da metodologia numérica é realizada através da comparação dos resultados do coeficiente de descarga para todas as aberturas de válvula utilizadas. A medição da vazão de ar na metodologia experimental é realizada com um anemômetro de filme quente de aplicação automotiva, calibrado para as condições do teste. Já a metodologia numérica utiliza dois modelos de turbulência, k-ω SST e k-ε standard. Os resultados numéricos apresentaram boa concordância com os experimentais para ambos os modelos adotados, quanto ao coeficiente de descarga. Entretanto, a diferença de comportamento do escoamento no interior do cilindro é elevada, pois o modelo k-ω SST é capaz de captar a oscilação transiente do jato que se forma na saída da válvula, inexistente no k-ε standard. O comportamento transiente causa uma significativa variação da vorticidade média em um plano perpendicular ao cilindro, com o escoamento trocando de direção principal de rotação em alguns instantes. Dados numéricos médios e de variação ao longo do tempo para swirl e tumble também são apresentados e discutidos. Ao analisar a oscilação da vazão mássica na fronteira de saída do domínio, frequências de aproximadamente 1300 Hz são captadas. Tais frequências são confrontadas com resultados experimentais obtidos pelo presente grupo de pesquisa para medições de oscilação de pressão no coletor de admissão do mesmo motor. O desvio percentual relativo para a frequência de oscilação é de 0,3%, o que demonstra a correta predição, tanto do fenômeno de desprendimento de vórtice quanto do coeficiente de descarga obtido através do modelo de turbulência k-ω SST. / With the increasing environmental problems concerning pollutant emissions, stringent standards have been applied in order to decrease harmful gases produced by the hydrocarbons combustion in internal combustion engines. The flow behaviour within the cylinder is an important factor that affects the emission’s formation in engines, since the intake stroke until the combustion. This work performs a numerical study with experimental validation of fluid flow at Honda GX35 engine, considering different fixed valve lifts and suction pressures to generate the flow. The validation of the numerical methodology is made through the discharge coefficient and flow pattern comparisons for all valve lifts utilized. The mass flow rate in the intake system is measured with an automotive hot film anemometer, calibrated for the test’s conditions. Regarding the computational solution for the turbulent air flow, two turbulence models were utilized: SST k-ω and k-ε standard. Although the numerical results presented a good agreement with the experimental data concerning the discharge coeficient, the flow pattern comparisons presented a high discrepancy among the models utilized. The SST k-ω model is capable to capture the transient behaviour of the jet formed in the valve exit, constituting the main difference between them. The transient oscillation causes a significant difference of mean vorticity in a cylinder section plane, with the bulk flow changing its main rotation along the time. The averaged and transient numerical data of swirl and tumble are presented and discussed. In the frequency analysis of the numerical mass flow rate oscillations, obtained at the outlet boundary, presented an average value about 1300 Hz. Such frequencies, when compared with experimental results obtained by the present research group for the pulsating pressure waves into the intake duct of the same engine, had a relative percentage deviation of 0.3%. The agreement between the results using the SST k-ω model reveals the correct prediction of vortex shedding frequency and discharge coefficient.

Made available in DSpace on 2015-05-14T12:42:59Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1980865 bytes, checksum: cc644ccfc2740ded432fde6ea3bf2de3 (MD5) Previous issue date: 2011-03-17 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This study deals with a very common phenomenon of the manuscripts writing in the past centuries; the abbreviation. Although it seems that this is a phenomenon that results from continued use of the computer or an immediate trend of globalized era, this research, from the perspective of discursive traditions and language of the text, will show that this is a characteristic of the current time about writing manuscripts, and it is mainly a written tradition of priestly and goes forward to the idea of paper economy, widespread idea on the studies of medieval writing. For the analysis of the information, it was assembled a corpus collected from a main Church in the city of Mossoró, composed by several books, which the first one was analyzed, corresponing to the period of the nineteenth century. As theoretical basis it was used Coseriu (1979), Oesterreicher (2002), Kabatek (2006), the analysis was amde under the theory of Traditions Discursive and under the textual language in which it is considered that all texts are made based on a previous text and existing features of the model can be preserved or not, depending on the needs either of the author or the moment. This study arose from the need of drawing a profile of writing in the nineteenth and twentieth centuries in the town of Mossoró. From the results we can state that the writing of tumble books reflects on the historical context in which the spelling did not follow a pattern. According to that, writing was based on the tradition of Portuguese models, which somehow made the abbreviations remain over a long time in the texts of the colonial era. / Este trabalho trata de um dos fenômenos bastante comum da escrita dos manuscritos dos séculos passados; a abreviação. Embora se pense que esse é um fenômeno decorrente do uso contínuo do computador ou uma tendência imediatista da era globalizada, esta pesquisa, sob o olhar das Tradições Discursivas e da linguística do texto, vai mostrar que essa é uma característica corrente da escrita da época dos manuscritos, e é principalmente uma tradição da escrita sacerdotal e vai de encontro à ideia de abreviação por economia de papel, ideia bastante difundida em estudos da escrita medieval. Para a análise de dados, foi montado um corpus coletado da Igreja Matriz na cidade de Mossoró, composto por vários livros de Tombo, dos quais só se analisou o primeiro, o qual corresponde ao período do século XIX. Como base teórica utilizou-se Coseriu (1979), Oesterreicher (2002), Kabatek (2006), a análise foi feita sob a teoria das Tradições Discursivas e da linguística textual nas quais se considera que todos os textos são produzidos tendo em base um texto já existente e características do modelo podem ser preservadas ou não dependendo da necessidade do autor ou do momento. Esse estudo nasceu da necessidade de traçar um perfil da escrita dos séculos XIX e XX da cidade de Mossoró. Dos resultados podemos apontar que a escrita dos livros de tombo reflete o contexto histórico em que a ortografia não seguia um padrão. Com isso a escrita baseava-se na tradição dos modelos portugueses, o que de certa forma, fez com que as abreviaturas permanecem ao longo de muito tempo nos textos da época colonial.