A Numerical and Experimental Assessment of the Use of a Turbine Utilizing Splitter Blades for an Automotive Variable Geometry Turbocharger

Automotive manufacturers require improved part load engine performance to further improve fuel economy. For a swing vane VGS (Variable Geometry Stator) turbine this means a more closed stator vane, to deal with the low MFRs (Mass Flow Rates), high PRs (Pressure Ratios) and low rotor rotational speeds. During these conditions the turbine is operating at low velocity ratios. As more energy is available at high pressure ratios and during lower turbocharger rotational speeds, a turbine which is efficient at these conditions is desirable. Another key aspect for automotive manufacturers is engine responsiveness. High inertia designs result in “turbo lag” which means an increased time before the target boost pressure is reached. Therefore, designs with improved performance at low velocity ratios, reduced inertia or an increased swallowing capacity are the current targets for turbocharger manufacturers.

To try to meet these design targets a CFD (Computational Fluid Dynamics) study was performed on a turbine wheel using splitter blades. A number of parameters were investigated. These included splitter blade merdional length, blade number and blade angle distribution.

The numerical study was performed on a scaled automotive VGS. Three different stator vane positions have been analysed. A single passage CFD model was developed and used to provide information on the flow features affecting performance in both the stator vanes and turbine.

Following the CFD investigation the design with the best compromise in terms of performance, inertia and increased MFP (Mass Flow Parameter) was selected for manufacture and testing. Tests were performed on a scaled, low temperature turbine test rig. The aerodynamic flow path of the gas stand was the same as that investigated during the CFD. The test results revealed a design which had similar performance at the closed stator vane positions when compared to the baseline wheel. At the maximum MFR stator vane condition a drop of −0.6% pts in efficiency was seen. However, 5.5% increase in MFP was obtained with the additional benefit of a drop in rotor inertia of 3.7%, compared to the baseline wheel.

An Investigation Into Improving Off-Design Performance in a Turbocharger Turbine Utilizing Non-Radial Blading

Off-design performance now plays a vital role in the design decisions made for automotive turbocharger turbines. Of particular interest is extracting more energy at high pressure ratios and lower rotational speeds. In this region of operation the U/C value will be low and the rotor will experience high values of positive incidence at the inlet. The positive incidence causes flow to separate on the suction surface and produces high blade loading at inlet, which drives tip leakage. A CFD analysis has been carried out on a number of automotive turbines utilizing non-radial fibred blading. To help improve secondary flows yet meet stress requirements a number of designs have been investigated. The inlet blade angle has been modified in a number of ways. Firstly, the blading has been adjusted as to provide a constant back swept angle in the span wise direction. Using the results of the constant back swept blading studies, the back swept blade angle was then varied in the span wise direction. In addition to this, in an attempt to avoid an increase in stress, the effect of varying the leading edge profile of the blade was investigated. It has been seen that off-design performance is improved by implementing back swept blading at the inlet. Varying the inlet angle in the span wise direction provided more freedom for meeting stress requirements and reduces the negative impact on blade performance at the design point. The blade leading edge profile was seen to offer small improvements during off-design operation with minimal effects on stress within the rotor. However, due to the more pointed nature of the leading edge, the rotor was less tolerant to flow misalignment at the design point.

A Numerical Study of the Flow Fields in a Highly Off-Design Variable Geometry Turbine

Conventionally, radial turbines have almost exclusively used radially fibred blades. While issues of mechanical integrity are paramount, there may be opportunities for improving turbine efficiency through a 3D blade design without exceeding mechanical limits. Off-design performance and understanding of the secondary flow structures now plays a vital role in the design decisions made for automotive turbocharger turbines. Of particular interest is extracting more energy at high pressure ratios and lower rotational speeds. Operating in this region means the rotor will experience high values of positive incidence at the inlet. A CFD analysis has been carried out on a scaled automotive turbine utilizing a swing vane stator system. To date no open literature exists on the flow structures present in a standard VGT system. Investigations were carried out on a 90 mm diameter rotor with the stator vane at the maximum, minimum and 25% mass flow rate positions. In addition stator vane endwall clearance existed at the hub side. From investigation of the internal flow fields of the baseline rotor, a number of areas that could be optimized in the future with three dimensional blading were identified. The blade loading and tip leakage flow near inlet play a significant role in the flow development further downstream at all stator vane positions. It was found that tip leakage flow and flow separation at off-design conditions could be reduced by employing back swept blading and redistributing the blade loading. This could potentially reduce the extent of the secondary flow structures found in the present study.

Split Converter-Fed SRM Drive for Flexible Charging in EV/HEV Applications

Electric vehicles (EVs) and hybrid EVs are the way forward for green transportation and for establishing low-carbon economy. This paper presents a split converter-fed four-phase switched reluctance motor (SRM) drive to realize flexible integrated charging functions (dc and ac sources). The machine is featured with a central-tapped winding node, eight stator slots, and six rotor poles (8/6). In the driving mode, the developed topology has the same characteristics as the traditional asymmetric bridge topology but better fault tolerance. The proposed system supports battery energy balance and on-board dc and ac charging. When connecting with an ac power grid, the proposed topology has a merit of the multilevel converter; the charging current control can be achieved by the improved hysteresis control. The energy flow between the two batteries is balanced by the hysteresis control based on their state-of-charge conditions. Simulation results in MATLAB/Simulink and experiments on a 150-W prototype SRM validate the effectiveness of the proposed technologies, which may provide a solution to EV charging issues associated with significant infrastructure requirements.

Estudo aerodinâmico e estrutural de um autogiro

O trabalho apresentado teve como principal objetivo a caracterização dos problemas aerodinâmicos e estruturais a serem observados no projeto de um Autogiro. Numa primeira etapa do trabalho, alguns conceitos básicos dos princípios da aerodinâmica que gera forças durante o voo destas aeronaves são delineadas. Numa segunda parte os componentes integrantes de um autogiro são modelados, onde alguns serão examinados por elementos finitos. Seguidamente foi realizado um cálculo á sustentação da asa, de modo a que o autogiro consiga levantar voo. Posteriormente, realizaram-se cálculos em algumas ligações aparafusadas, que se consideraram ser mais importantes para a intensidade das forças. Este cálculo teve como o objetivo, determinar se as ligações aparafusadas respeitam o critério de segurança. Finalmente, executou-se uma análise em elementos finitos na estrutura e no rotor, de maneira a avaliar o comportamento em termos da distribuição de tensões. Nesta etapa final também foi realizada uma análise às vibrações do autogiro, determinando as frequências naturais na estrutura e asa do rotor.

Non-linear analysis of piezolaminated structures

In the recent years the study of smart structures has attracted significant researchers, due to their potential benefits in a wide range of applications, such as shape control, vibration suppression, noise attenuation and damage detection. The applications in aerospace industry are of great relevance, such as in active control of airplane wings, helicopter blade rotor, space antenna. The use of smart materials, such as piezoelectric materials, in the form of layers or patches embedded and/or surface bonded on laminated composite structures, can provide structures that combine the superior mechanical properties of composite materials and the capability to sense and adapt their static and dynamic response, becoming adaptive structures. The piezoelectric materials have the property of generate electrical charge under mechanical load or deformation, and the reverse, applying an electrical field to the material results in mechanical strain or stresses.

Planung und Ausführung wärmeschutztechnischer Verbesserungen bei Altbauten

Im Bericht werden Maßnahmen zur wärmeschutztechnischen Verbesserung von Altbauten untersucht, u.a. Kerndämmung und innenliegende Dämmung, Wärmedämmung von Kellerdecken, Geschoßdecken, Steil- und Flachdächern, alten Fenstern und sonstiger Bauteile.

Drucktrennen sprödharter Werkstoffe

Drucktrennen ist ein Verfahren zum spanlosen Trennen zylindrischer oder prismatischer Bauteile durch in einem Teilbereich der Mantelfläche auf das Werkstück wirkenden Fluidhochdruck. In der vorliegenden Arbeit werden die Wirkzusammenhänge zwischen der Bearbeitung sprödharter zylindrischer Werkstücke und den resultierenden Oberflächen- und Randzoneneigenschaften theoretisch analysiert und die Ergebnisse mit denen experimenteller Untersuchungen verglichen. Der Fluidhochdruck bewirkt einen hauptsächlich von der Werkstückgeometrie und dem Aufbau der für die Versuchsdurchführung entwickelten Trennkammer abhängigen Spannungszustand des Werkstücks. Gleichzeitig dringt das Trennmedium in Oberflächenanrisse ein und ruft dort lokale Zugspannungen im Bereich der Rißspitze hervor. Erreicht der Fluiddruck einen vom Spannungszustand und der Rißlänge abhängigen kritischen Wert, so wird die Bruchzähigkeit des Werkstoffs überschritten und ein Sprödbruch des Werkstücks ausgelöst. Durch gezielt eingebrachte Kerben kann der Ort der Trennung exakt vorgegeben werden. Die Werkstücktrennung erfolgt senkrecht zur Richtung der größten Hauptspannung, welche stets ungefähr parallel zur Werkstückmittelachse orientiert ist. Um eine völlig ebene Bruchfläche zu erreichen, muß eine Ankerbung in Kammermitte erfolgen und das Werkstück absolut symmetrisch zur Trennfläche ausgerichtet sein. Der vom nachdrängenden Fluid vorangetriebene Bruch wird durch Druckspannungen in bestimmten Bereichen des belasteten Bauteils gehemmt. Die Bruchgeschwindigkeit ist demzufolge in der Regel so niedrig, daß für amorphe und einkristalline Werkstoffe keine Bruchverzweigung erfolgt. Dadurch ist beispielsweise für optisches Glas und einkristallines Silizium die Herstellung spiegelglatter Oberflächen möglich. Die Trennflächen vielkristalliner Werkstoffe weisen dagegen eine geringe Oberflächengüte auf, da der Energieüberschuß im Bereich der Rißspitze nicht ausreicht, um einen transkristallinen Sprödbruch voranzutreiben, sondern stets erhebliche interkristalline Bruchanteile vorliegen.

Étude CFD des effets du désalignement et du cisaillement sur les performances et le chargement des hydroliennes

Le développement des hydroliennes se base souvent sur des conditions d'écoulement idéalisées qui ne reflètent pas entièrement le courant présent sur un site réel. Dans cette optique, ce mémoire investigue l'effet d'un écoulement non aligné ou cisaillé sur les performances et le chargement de deux types d'hydrolienne : les hydroliennes à rotor axial (HRA) et à aile oscillante (HAO). Cette étude est réalisée à l'aide de simulations numériques et les résultats démontrent que pour les deux types d'hydrolienne, le désalignement produit une réduction de la puissance et de la traînée, tandis que le cisaillement n'a qu'un effet de second ordre sur ces derniers. Le chargement additionnel sur la structure de support causé par des conditions d'écoulement non idéal est aussi similaire pour les deux technologies. Le désalignement et le cisaillement affectent cependant plus significativement le chargement en fatigue des pales de l'HRA que celui de l'aile de l'HAO.

Fungal contamination in two Portuguese wastewater treatment plants

The presence of filamentous fungi was detected in wastewater and air collected at wastewater treatment plants (WWTP) from several European countries. The aim of the present study was to assess fungal contamination in two WWTP operating in Lisbon. In addition, particulate matter (PM) contamination data was analyzed. To apply conventional methods, air samples from the two plants were collected through impaction using an air sampler with a velocity air rate of 140 L/min. Surfaces samples were collected by swabbing the surfaces of the same indoor sites. All collected samples were incubated at 27°C for 5 to 7 d. After lab processing and incubation of collected samples, quantitative and qualitative results were obtained with identification of the isolated fungal species. For molecular methods, air samples of 250 L were also collected using the impinger method at 300 L/min airflow rate. Samples were collected into 10 ml sterile phosphate-buffered saline with 0.05% Triton X-100, and the collection liquid was subsequently used for DNA extraction. Molecular identification of Aspergillus fumigatus and Stachybotrys chartarum was achieved by real-time polymerase chain reaction (RT-PCR) using the Rotor-Gene 6000 qPCR Detection System (Corbett). Assessment of PM was also conducted with portable direct-reading equipment (Lighthouse, model 3016 IAQ). Particles concentration measurement was performed at five different sizes: PM0.5, PM1, PM2.5, PM5, and PM10. Sixteen different fungal species were detected in indoor air in a total of 5400 isolates in both plants. Penicillium sp. was the most frequently isolated fungal genus (58.9%), followed by Aspergillus sp. (21.2%) and Acremonium sp. (8.2%), in the total underground area. In a partially underground plant, Penicillium sp. (39.5%) was also the most frequently isolated, also followed by Aspergillus sp. (38.7%) and Acremonium sp. (9.7%). Using RT-PCR, only A. fumigatus was detected in air samples collected, and only from partial underground plant. Stachybotrys chartarum was not detected in any of the samples analyzed. The distribution of particle sizes showed the same tendency in both plants; however, the partially underground plant presented higher levels of contamination, except for PM2.5. Fungal contamination assessment is crucial to evaluating the potential health risks to exposed workers in these settings. In order to achieve an evaluation of potential health risks to exposed workers, it is essential to combine conventional and molecular methods for fungal detection. Protective measures to minimize worker exposure to fungi need to be adopted since wastewater is the predominant internal fungal source in this setting.

Diagnóstico de avarias em máquinas rotativas utilizando a análise de órbitas

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Mecânica Perfil Manutenção e Produção

Avaliação do potencial eólico para geração de energia eléctrica

Trabalho Final de Mestrado para a obtenção do grau de Mestre em Engenharia Mecânica /Energia

Estudo da turbina de Tesla visando a sua aplicação em sistemas de geração de energia elétrica descentralizada

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Mecânica

On-line system for faults detection in induction motors based on PCA

Dissertation to obtain the degree of Master in Electrical and Computer Engineering

Otimização de um sistema online de deteção de falhas em motores de indução

Dissertação para obtenção do Grau de Mestre em Engenharia Eletrotécnica e de Computadores