<p>The objectives of this investigation were to experimentally and numerically assess the performance of a ball bearing supported turbocharger (TC). Turbochargers are mechanical devices used to improve the efficiency of modern engines. Using ball bearings improves the TC efficiency, and represents one of many evolving high-speed applications for ball bearings.</p> <p>The experimental objectives of this investigation were to design and develop a turbocharger test rig (TTR) to measure the shaft whirl of the rotating assembly and the axial and frictional loads experienced by the bearing cartridge. The TTR contains a ball bearing TC which was instrumented and operated under a variety of test conditions including rotational speeds up to 55,000 rpm. In order to measure the axial loads on the compressor and turbine sides, customized sensors were designed, fabricated and integrated into the TC housing. The anti-rotation (AR) pin, which normally prevents the bearing cartridge from rotating, was replaced with a custom-made sensor to measure frictional losses in the bearing cartridge.  These sensors were designed to minimally affect the operation of the TC. Proximity probes were initially installed on the compressor side and later on the turbine side to monitor shaft whirl using targets attached to the ends of the impellers. An assembly to record axial shaft motion with a proximity probe was also developed. Axial load and motion results indicated that the compressor side bears most of the axial load. As the backpressure or the speed of the TC increased the axial load also increased. Frictional measurements from the AR pin sensor demonstrated low power losses in the ball bearing cartridge. For certain shaft speed ranges, the data from the sensors illustrated periodic trends in response to subsynchronous whirl of the shaft.</p> <p>The numerical modeling objectives of this investigation were to characterize the dynamics of the ball bearing supported TC. In this TC, the compressor, turbine and shaft are supported by a bearing cartridge composed of back-to-back angular contact ball bearings. The cartridge is supported by squeeze film dampers (SFDs) and is prevented from rotation by the AR pin. To achieve the objectives, first an equivalent bearing model was developed to investigate the bearing dynamics and whirl of the TC rotating assembly. The TC bearing cartridge was modeled with a single deep groove ball bearing (DGBB) using the discrete element method. The SFD which supports the bearing was modeled with a bilinear spring and damper. A DGBB was used because it can support axial load in both directions. This model was then extended to include a flexible shaft represented by tetrahedral finite elements and supported by an ACBB cartridge. After this model was used to reproduce the whirl from the test rig, the bearing internal geometry and SFD properties were adjusted to determine their effect on shaft whirl. Wear and damage criteria were also developed to evaluate the simulation results. The best simulation result was obtained with a small clearance in the bearing and with a stiffer SFD. The clearance was necessary as the shaft and bearing deform at high speeds, preloading the bearing.</p> <p>The best simulation result was found to have reduced sliding and limited variation in contact force, which should lead to reduced friction and improved overall life. This study demonstrates the importance of taking the bearing system into account while designing a TC or other high speed mechanical system, as the bearing and SFD properties can have a significant impact on the system performance.</p>

No description available.

Le présent travail concerne l'étude du décollement de coin de compresseurs par des investigations expérimentaux sur le banc d'essai subsonique grille d'aubes situé au LMFA (Re = 3.8 x 105, M = 0,12, profil NACA 65-009). Habituellement, cette particulière séparation tridimensionnelle a lieu dans le coin entre l'aubage et la paroi du moyeu des rangées d'aubes, également dans les stators et les rotors.Les performances de l’étage sont ainsi dégradées à cause des pertes de charge et du blocage conséquent à la séparation de l’écoulement. Bien que les caractéristiques stationnaires sont bien connues par la littérature, uniquement des récentes études expérimentales avancées combinées aux améliorations de simulations numériques, telles que URANS et LES, ont permis de découvrir le comportement très instable du décollement de coin. Des études préalables sur le même banc d'essai ont rapporté un comportement intermittent du décollement, appelé comportement bimodal. Dans la présente thèse de doctorat, il est montré que le comportement bimodal correspond à deux états spécifiques du champ fluide: une séparation fermée, presque supprimée, et une séparation ouverte caractérisée par un blocage massif. Il est clair que cette commutation bimodale du décollement de coin apparaissant dans une machine réelle pourrait avoir un impact fortement déstabilisant. En utilisant la méthode de mesure PIV haute vitesse couplée à des mesures de pression résolues en temps sur la surface de l'aubage, l'écoulement d'un canal inter-aube a été étudié pour deux différentes incidences. Les mesures PIV fournissent pour la première fois des visualisations résolues en temps et étendues à toute la section de l'aubage de la variation bimodale du décollement. L'interaction des grandes structures aléatoires de la couche limite à l'amont avec le bord d'attaque de l'aubage déstabilise le front du décollement et agrandit la région de recirculation. Une séparation ainsi massive persiste jusqu'à ce que le blocage dans le canal inter-aube provoque la rupture des plus grandes structures constituant la zone de recirculation. Successivement le débit recommence à accélérer et la séparation est presque supprimée. Cette dynamique coïncide avec le régime d'écoulement hautement instationnaire et apériodique des diffuseurs, appelé large transitory stall, caractérisé par des grandes amplitudes d'énergie dans la gamme des basses fréquences du spectre. Des moyennes conditionnelles de pression et la décomposition orthogonale modale (POD) des champs de vitesse ont été appliquées pour montrer l'effet rétroactif du blocage induit par la séparation ouverte sur l'angle local au bord d'attaque. Ces résultats supportent l’hypothèse d'une instabilité auto-entretenue causée par la diffusion imposée dans le stator. En fin, des mesures de pression totale résolues en temps ont été effectuées en utilisant des capteurs à haute réponse en fréquence, situés à la même position dans les différents canaux adjacents. La cohérence et la linéarité de l'angle de phase trouvée entre les capteurs confirment que l'instabilité du décollement peut se propager d'un canal a l'autre, en analogie avec les perturbations tournantes (rotating instabilities) apparaissant dans les bancs d'essai annulaires. Ceci montre pour la première fois que, même dans une grille d'aubes linéaire de compresseur, l'instabilité intrinsèque du décollement de coin peut déclencher la propagation d'instabilités. / The present work focuses on the study of the corner separation phenomenon in compressors carried out by experimental investigations on a subsonic linear cascade test rig (Re=3.8x105, M=0.12, blade profile NACA 65-009). Usually, this particular three-dimensional separation takes place in the corner between the blade and the endwall of compressor rows, mostly at hub, both in stators and rotors.Its main features are high total pressure losses and blockage of the flow, with consequent impacts on the efficiency. Whereas time averaged characteristics are well known from the past, only recent advanced experimental studies and improvements of numerical simulations, such as URANS and LES, have permitted to uncover the highly unsteady behavior of corner separation in compressors. Precedent studies on the same test rig have reported an intermittent unsteady behavior of corner separation, called bimodal behavior. In the present thesis it is shown that the bimodal behavior corresponds to two specific states of the flow: a closed separation, almost suppressed, and an open separation characterized by massive blockage and losses. Clearly hub-separation bimodal switches appearing in a real machine could have a first order detrimental effect on the stability of the flow in the compressor. By using high speed PIV coupled with unsteady pressure measurements on the surface of the blade the flow in a single blade passage has been investigated for different incidences. The PIV measurements provide, for the first time, time-resolved flow visualizations of the size switch of the separation with an extended field of view covering the entire blade section. The interaction of random large structures of the incoming boundary layer with the blade is found to be a predominant element that destabilizes the separation boundary and enlarges the recirculation region. Such a massive separation persists until the blockage in the passage causes the breakdown of the largest structures in the aft part of the blade, reestablishing the closed separation state. Such dynamics coincide with the aperiodic intermittent flow regime of diffusers, called transitory stall regime, and the associated Fourier spectra show the largest energy amplitudes in the low frequency range. Conditional ensemble averages of pressure and proper orthogonal decomposition (POD) of velocity fields have been applied to show the feedback effect of the blockage of the separation on the flow angle around the blade leading edge. These results draw the picture of a self-sustained instability caused by the diffusion imposed by the inter-blade passage. To answer the question about the interaction between adjacent corner separations, time-resolved total pressure measurements have been carried out by using high frequency response sensors positioned in bimodal points of multiple passages. The coherent propagation velocity and the linearity of the phase angle found between the signals confirm that the unsteadiness of the separation can propagate in pitch-wise direction. It is interesting to underline that equivalent elements characterize rotating disturbances appearing in annular test rigs. This finally shows that, even in an isolated stator blade row, the intrinsic unsteadiness of corner separation can start the propagation of instabilities. It is the first time that such a propagation effect is observed in a linear compressor cascade.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / With the globalization and the competitiveness in all the levels of the industrial sector, the final product quality search became higher. On the other hand, energy saving became another important factor in modern industry. The consumption of electric energy in the industrial sector represents 45.5% of the total consumption of the country. The motor force represents most of this consumption, arriving to be superior of 80% in the textile, paper and cellulose sectors. This work presents two strategies of control, auto-adjustable PID and fuzzy controller, the objectives are a better final product quality and the energy saving. Ventilation and compression industrials process are used in this work. An analysis of limit cyclesâ presence through the descriptive function of the fuzzy controller is carried through, providing a previously validation of fuzzy controllerâs parameters by simulations, saving time in the adjust phase. Set-point changes are easily made and on-line, still the process is running, in the two considered controllers. Comparisons of energy consumption are made between the conventional strategies and the two strategies considered in this work. / Com a globalizaÃÃo e a competitividade em todos os nÃveis do setor industrial, a qualidade do produto final se tornou de importÃncia crescente. Por outro lado, a conservaÃÃo de energia no setor industrial se tornou outro fator importante na indÃstria moderna. O consumo de energia elÃtrica do setor industrial representa 45,5% do consumo total do paÃs. A forÃa motriz representa a maior parte deste consumo, chegando a ser superior a 80% nos setores tÃxtil, de papel e celulose. Este trabalho apresenta duas estratÃgias de controle, PID auto-ajustÃvel e controlador nebuloso, e tÃm como objetivos tanto a qualidade do produto final quanto a eficiÃncia energÃtica. SÃo utilizados processos de ventilaÃÃo e de compressÃo em escala industriais. Uma anÃlise da presenÃa dos ciclos limites atravÃs da funÃÃo descritiva do controlador nebuloso à realizada, de forma que os parÃmetros do controlador nebuloso podem ser previamente validados atravÃs de simulaÃÃes, poupando tempo na fase de ajuste dos parÃmentros do controlador. MudanÃas de set-point sÃo facilmente realizadas de forma online e sem que o funcionamento do processo seja descontinuado, nos dois controladores propostos. ComparaÃÃes quanto ao consumo de energia sÃo realizadas usando as estratÃgias de controle convencionais e as proposta neste trabalho.

Magistro baigiamajame darbe nagrinėjami vėdinimo įrenginiai su integruotais šilumos siurbliais. Darbe atliekama tokios rūšies įrenginių literatūros apžvalga. Apžvelgiami šilumos siurblio komponentai, darantys didžiausią įtaką jo darbui. Darbo metu atlikti įrenginių projektavimo ir konstravimo darbai. Pateikiamos projektavimo rekomendacijos. Lyginami skirtingi kompresorių galios moduliacijos principai. Nagrinėjami įrenginių darbo režimai, kylančios problemos eksploatacijos metu, ieškomi problemų sprendimų būdai. Pateikiamos kintamo sukimosi greičio kompresorių galių moduliacijos ribos. Atliekamos energinė ir ekserginė analizės pagal eksperimentinio bandymo duomenis. Nustatomi realūs termodinaminio efektyvumo ir naudingumo koeficientai. Jautrumo analizės metu atliekami elektrinio šildytuvo efektyvumo ir naudingumo skaičiavimai. Pateikiami rezultatai, išvados ir rekomendacijos tokios rūšies įrenginių tobulinimui ir tolimesniam vystymui. Darbo apimtis – 94 psl. teksto be priedų, 66 iliustr., 7 lent., 43 bibliografiniai šaltiniai. / Master's thesis examines air handling units with integrated air source heat pumps. Literature review about this type of units was carried out. An overview of mostly important heat pump‘s components are given. Thesis was an opportunity to design, construct and analyze these units. Different heat pump‘s operation modes examined and main issues turned out. Based on experimental data variable speed compressor's capacity modulation results defined. Moist air thermodynamic calculations have been made and air handling unit with integrated air source heat pump experimental energy and exergy efficiency was defined. Sensitivity evaluation changing heat pump with electric heater carried out. The main recommendation provided for units designing and further development. Thesis consist of 94 p. text without appendixes, 66 pictures, 7 tables, 43 bibliographical entries.

The main purpose of this master’s thesis is description of the current technology of compressed air production in the grounds of Třinecké Železárny, a.s. (TZ). Compressed air for companies in the TZ area is manufactured and distributed by company Energetika Třinec, a.s. (ET). The part of the thesis is the preparation and execution of measurement including evaluation of specific energy consumption for production of compressed air by compressors of ET company. In conclusion there is proposed the possibility of substitution of compressors including the economic evaluation.

Le comportement dynamique des turbomachines industrielles doit respecter des critères émis par les normes internationales et les utilisateurs. Les rotors flexibles sont sensibles à la distribution de balourd, et sont soumis aux excitations aérodynamiques de leur environnement. Usuellement, les contrôleurs utilisés peinent à délivrer le niveau d’exigence demandé, par conséquent les propriétés mécaniques des paliers magnétiques sont fortement dépendantes de celles des rotors. L’objectif de ce mémoire est d’analyser le comportement dynamique des compresseurs centrifuges afin de proposer une stratégie de contrôle innovante. D’abord, chaque palier est considéré comme une entité a part entière en couplant ses deux axes d’action. Le comportement dynamique du rotor est exprimé dans le repère polaire. Par ailleurs, la logique floue, qui utilise un modèle de pensée proche du raisonnement humain, applique des actions correctives en fonction du comportement dynamique global du rotor. Ainsi, l’utilisation couplée de ces deux approches créé une synergie permettant d’agir sur le système de manière ciblée. Le contrôleur dissipe l’énergie cinétique du rotor lors du franchissement de vitesses critiques afin d’atténuer la réponse au balourd, ou augmente la raideur du palier lors de vibrations transitoires ou asynchrones afin de réduire la trajectoire du rotor. Le faible amortissement structurel du rotor le rend sensible au phénomène de « spillover » (l’énergie de contrôle affecte les modes de fréquence élevée). Or, la logique floue ne peut pas gérer ce phénomène. Ainsi, un contrôleur PID sous-jacent est utilisé pour maîtriser la stabilité des modes hautes fréquences. Au final, le contrôleur flou polaire permet d’obtenir des marges de performances entre les capacités de cet asservissement et le cahier des charges. Ces marges sont utilisées pour trois objectifs : le respect des spécifications, l’amélioration du comportement subsynchrone, et enfin la simplification et la standardisation du contrôleur sous-jacent nommé ici SPID. Ce contrôleur est tel que ses caractéristiques, dans la plage de fréquence utile, sont indépendantes du rotor pour une application donnée. Enfin, la stratégie développée est évaluée avec des simulations numériques et des essais expérimentaux. D’abord, le modèle numérique est validé, puis le contrôleur est appliqué à un banc d’essais académique. Le comportement est stable et robuste. Il présente des performances supérieures au PID augmenté fourni avec le banc, que ce soit pour la réponse au balourd, ou pour la réponse à des excitations subsynchrones. Finalement, la démarche est appliquée à un compresseur industriel. Les simulations montrent que le comportement est proche de celui exigé pour des machines sur paliers classiques. L’optimisation de l’approche et l’automatisation de la conception pourraient conduire à la standardisation des paliers magnétiques actifs. / The dynamic behaviour of large turbomachinery should satisfy stringent requirements dictated by international standards and final users. Their flexible rotor is sensitive to the unbalance distribution and subjected to particular excitations coming from the industrial process. Usually, the performance margins between the requirements and the classical controller capabilities are small. Consequently, the magnetic bearing characteristics depend on the rotor geometry. Designing such controllers is difficult and time consuming. The objective of this thesis is to investigate the dynamic behaviour of supercritical centrifugal compressors in order to propose a new control strategy. First, each bearing is considered as one entity by coupling its two axes of action. The introduction of polar quantities permits a better observation of the rotor dynamic behaviour. In addition, by using logic close to human being reasoning, the fuzzy logic modulates the action forces as a function of the global dynamic behaviour. The coupling of the two approaches is an efficient way to apply targeted corrective actions. This controller attenuates the unbalance vibration when crossing critical speeds by applying damping forces, or increases the stiffness during transient or asynchronous excitations in order to limit the maximum displacement reached. As their structural damping is low, flexible rotors are very sensitive to spillover effect, which cannot be managed by fuzzy controllers. Consequently, an underlying PID is necessary. This hand-synthesized controller has high frequency characteristics tuned in order to ensure stability and robustness for each rotor. Compared to a classical approach, the polar fuzzy controller enables to increase the performance margins. These margins are used to fulfil three objectives: the achievement of standards requirements, the improvement of the subsynchronous behaviour, and the simplification and the standardization of the PID controller that we called SPID. This SPID is designed for a given application, such that the bearing characteristics on the operating frequency range are always the same. The control strategy is assessed numerically and experimentally. First, the numerical model is validated with experimental tests. Then, the controller developed is applied to an academic test rig. The controller is stable and robust. It exhibits performance superior to the augmented PID supplied with the test rig for both unbalance response and response to subsynchronous excitations. Finally, the control of an industrial compressor is assessed numerically. The results obtained are close to the standards requirements used for classical bearings. The optimization of the approach and the utilization of an automatic tuning algorithm for high frequency characteristics could lead to the standardization of Active Magnetic Bearings.

<p>The objective of this research was to develop stability enhancing design features for aeroengine centrifugal compressors. The motivation for this research is based on climate change and fuel-efficiency concerns, which call for improvements in achievable pressure ratios and surge margins. Specifically, this research aimed to develop diffuser recirculation channels and provide more insight into their design space. These channels are passive casing treatments in the diffuser and have been successfully demonstrated to improve stage surge margin. Diffuser recirculation channels are secondary flow paths that connect an opening near the diffuser inlet to one further down in the passage. Flow is recirculated by relieving the static pressure differential between the two openings. The basic design concept of these features is to add blockage upstream of the diffuser inlet, reducing the amount of diffusion in the vaneless space. In addition, channel geometries can be optimized to specifically target adverse flow properties, such as high incidence on the diffuser vane leading edge.</p> <p><br></p> <p>This design development was purely computational and served as the first approach to implementation of these features in a future generation of the Centrifugal Stage for Aerodynamic Research (CSTAR) at the Purdue Compressor Research Lab. Design development consisted of a computational design study, which quantified the effects of changing diffuser recirculation channel geometries on stage stability and performance metrics. Moreover, the CFD model for this future configuration of CSTAR was created and served as the baseline comparison for design iterations. The design study was comprised of controlled variation of channel geometry parameters and iterative solving of those cases in unsteady full stage single passage CFD models. Further design optimization studies were completed on specific down-selected recirculation channel geometry configurations. In total, 16 unsteady CFD cases with varied geometry configurations and 43 steady models were solved. Once a final optimized design was confirmed, a pressure characteristic at 100 % corrected design speed was generated. Compared to the baseline speed line, the implementation of diffuser recirculation channels resulted in a more gradual numerical surge and apparent numerical surge margin enhancement. Furthermore, the variation in incidence at the diffuser vane leading edge near the shroud was significantly reduced with diffuser recirculation. For the baseline compressor, incidence grew by about 70 degrees from the design aerodynamic loading to numerical surge at that location. However, flow stabilization due to diffuser 16 recirculation resulted in a change of approximately 2 degrees through that range. In conclusion, a first approach design recommendation for diffuser recirculation channels is CSTAR was generated through computational studies. Using this recommendation, diffusers with this recirculation channel design can be manufactured and tested for experimental concept validation.  </p>