Letteratura scientifica selezionata sul tema "Rotating ventilator"
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Articoli di riviste sul tema "Rotating ventilator"
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Renz, Andreas, Julian Praß, Johannes Weber e Stefan Becker. "Experimental Investigation of a Friction Ventilator". Advanced Engineering Forum 19 (ottobre 2016): 43–49. http://dx.doi.org/10.4028/www.scientific.net/aef.19.43.
Testo completoAbstract (sommario):
Standard decentralized ventilation systems typically consist of two ventilators for inlet and exhaust air and a heat exchanger for the heat recovery. A recently developed device, a so called friction ventilator, combines these three elements into a single functional element. The ventilator consists of circular plates which are rotating centrally in between the inlet and the outlet duct of a ventilation system and generate a countercurrent flow in the two ducts. Furthermore, the discs act as a rotating heat exchanger between the two air flows. To increase understanding of the energy transfer from the rotating discs to the flow an experimental investigation on the effect of different rotor geometries was conducted. The study showed an interesting influence of the hub diameter on the characteristic curves with a higher pressure difference for an increase in diameter. The results of the heat recovery measurement however were only mildly affected by the hub geometry. Here the distance between the discs, the rotational speed of the discs and the volumetric flow seemed to have the greatest effect on heat recovery.
2
Wu, Juan, Ziming Kou e Jing Liu. "The Acoustical Behavior of Contra-Rotating Fan". Mathematical Problems in Engineering 2018 (2018): 1–8. http://dx.doi.org/10.1155/2018/3739067.
Testo completoAbstract (sommario):
The noise produced by a contra-rotating ventilator can cause injury to humans. Therefore, it is important to reduce noise caused by ventilators. In this study, the Ffowcs Williams and Hawkings (FW-H) model was used to simulate the acoustics of four different axial impeller spacing points based on the unsteady flow field through a FBD No. 8.0 contra-rotating ventilator. Experiments were conducted to verify the correctness of the numerical model. Meanwhile, the Variable Frequency Drive (VFD) drives the two motors of 55 kW to give the impellers different speeds to distinguish different conditions. The results showed that the main noise source of the ventilator was the two rotating impellers and the area between them. For the same axial space, the noise decreased with the increase of flow rate and then decreased. And the amplitude of the discrete pulse increased gradually. It can be concluded that the vortex acoustics decreased gradually with the increase of flow rate and the rotating acoustics were the major contributor. With the axial distance increasing, the noise caused by the two impellers was weak, and the frequencies of sound pressure level moved toward medium- and low-frequency bands gradually. The suitable axial space could reduce noise and improve the working environment.
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Ma, Zhong Fei, Peng Gang Jin e Feng Zhao. "Test on Characteristics of the High-Pressure Secondary Rotary Water Gas Jet Ventilation". Advanced Materials Research 594-597 (novembre 2012): 2167–70. http://dx.doi.org/10.4028/www.scientific.net/amr.594-597.2167.
Testo completoAbstract (sommario):
In order to reduce the concentration of explosive gas, experimental research was carried out on the high pressure secondary rotating water jet ventilation characteristic, and the principle of high pressure secondary rotating water jet ventilation was analyzed. Experiments of the relationship between pressure and the suction air flow characteristics were carried out with different structure of jet pipe, different structure of nozzles, different throat in high pressure single rotating water jet ventilation, and the secondary rotating ventilation characteristic were tested with different guide vane angle. The results show that the air-sucking quantity approximatively increased with water pressure in accordance with parabola in the high press secondary rotating water jet ventilator, the air-sucking quantity of different structure of jet pipe was not same, the air-sucking quantity was significantly greater than that of swirl nozzle, the secondary rotary ventilation acts on the larger range.
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Rashid, D. M. H., e N. A. Ahmed. "Study of Aerodynamic Forces on a Rotating Wind Driven Ventilator". Wind Engineering 27, n. 1 (febbraio 2003): 63–72. http://dx.doi.org/10.1260/030952403321833770.
Testo completoAbstract (sommario):
A wind driven ventilator is a simple, cost-effective and environmentally-friendly device that can improve comfort and the working environment. Unfortunately very little is known about the complex flow field associated with the operation of this device. A wind tunnel investigation of the flow associated with a rotating wind ventilator was, therefore, carried out at the aerodynamic laboratory of the University of New South Wales within the Reynolds number range of 1.1 times 105 to 5.5 times 105. An attempt was also made to study some of the important features associated with operation of a rotating wind ventilator using a simple model of a stationary and a spinning cylinder. The results were encouraging and several flow features were identified for future improvement in the performance of a wind ventilator.
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Szabó, Ferenc János, e Ágnes Várkuliné Szarka. "Finite Element Study of Rotating Elements of a Ventilator". International Review of Mechanical Engineering (IREME) 13, n. 6 (30 giugno 2019): 326. http://dx.doi.org/10.15866/ireme.v13i6.17145.
Testo completo
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Farahani. "Simulation of Airflow and Aerodynamic Forces Acting on a Rotating Turbine Ventilator". American Journal of Engineering and Applied Sciences 3, n. 1 (1 gennaio 2010): 159–70. http://dx.doi.org/10.3844/ajeassp.2010.159.170.
Testo completo
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HE, Qiudong. "Analyses on Blade Fracture of Contra-rotating Axial Fan for Mine Local Ventilator and Its Improvement Measures". Journal of Mechanical Engineering 47, n. 24 (2011): 122. http://dx.doi.org/10.3901/jme.2011.24.122.
Testo completo
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Cho, Dong-Hyun. "A Study on the Improvement of Efficiency of Heat Transfer on the Heat Recovery Ventilator with Rotating Porous Disk". Journal of Fisheries and Marine Sciences Education 26, n. 6 (31 dicembre 2014): 1352–57. http://dx.doi.org/10.13000/jfmse.2014.26.6.1352.
Testo completo
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Goto, Takahisa, Hayato Saito, Yoshinori Nakata, Shoichi Uezono, Fumito Ichinose, Masanori Uchiyama e Shigeho Morita. "Effects of Xenon on the Performance of Various Respiratory Flowmeters". Anesthesiology 90, n. 2 (1 febbraio 1999): 555–63. http://dx.doi.org/10.1097/00000542-199902000-00032.
Testo completoAbstract (sommario):
Background The anesthetic gas xenon has distinctly different physical properties compared with air, nitrous oxide, or oxygen. This led us to predict that xenon would affect the performance of commercially available flowmeters. Methods Flow was generated by an anesthesia ventilator connected to a lung simulator via a semiclosed breathing circuit. With the system filled with air or with various concentrations of xenon or nitrous oxide in a balance of oxygen, the tidal volume was measured with two rotating vanes, a Pitot tube, a variable-orifice flowmeter, and two constant-temperature hot-wire flowmeters. Results Although xenon minimally affected both rotating vane flowmeters, it caused the Pitot tube and the variable-orifice flowmeters to overread in proportion to the square root of the density of the gas mixture used (xenon is 4.6 times more dense than air). In contrast, the hot-wire anemometers underread with xenon; for example, their readings in the presence of 45% and 70% xenon were less than 10% of those displayed when air was used. Nitrous oxide minimally affected all the flowmeters except the variable-orifice device. The Pitot flowmeter was also affected, but only when its gas analyzer port was open to the ambient air so that it no longer corrected its readings for changes in gas composition. In these cases, nitrous oxide produced overreadings in the same manner as did xenon. Conclusion Among the four types of flowmeters studied, only the rotating-vane type is sufficiently accurate for use during anesthesia with xenon.
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Shen, Luke Y., Stephen D. Helmer, Jennifer Huang, Gerayu Niyakorn e R. Stephen Smith. "“Shift Work” Improves Survival and Reduces Intensive Care Unit Use in Seriously Injured Patients". American Surgeon 73, n. 2 (febbraio 2007): 185–91. http://dx.doi.org/10.1177/000313480707300220.
Testo completoAbstract (sommario):
We assessed whether a trauma service model with an emphasis on continuity of care by using “shift work” will improve trauma outcomes and cost. This was a case-control cohort study that took place at a university-affiliated Level I trauma center. All patients (n = 4283) evaluated for traumatic injuries between May 1, 2002 and April 30, 2004 were included. During Period I (May 1, 2002 to April 30, 2003), a rotating off-service team provided initial management between 5:00 PM and 7:00 AM. The “day team” provided all other care and was responsible for continuity of care. In Period II (May 1, 2003 to April 30, 2004), a dedicated trauma service consisting of two resident teams evaluated all injured patients. Variables included hospital and intensive care unit length of stay (LOS), mechanical ventilation requirements, hospital mortality, and hospital care costs. Demographics and injury mechanism for both periods were similar, but Injury Severity Score (ISS) in Period II was greater (ISS, 8.2% vs 7.2%, P < 0.0001; ISS > 15, 18.5% vs 15.4%). In the more severely injured (ISS > 15), patients in Period II had shorter hospital LOS (8.6 vs 9.7 days, P = 0.98), a shorter ICU LOS (5.5 vs 7.7 days, P = 0.039), shorter mechanical ventilator requirements (5.5 vs 7.7 days, P = 0.32), improved hospital mortality rate (19.9% vs 26.8%, P = 0.029), and decreased hospital costs ($19,146 vs $21,274, P = 0.36). On multivariate analysis, factors affecting mortality and LOS included age, initial vital signs, injury type, and ISS. Overall, the two trauma service models resulted in similar outcomes. Although multivariate analysis revealed that treatment period did not affect mortality, our study revealed improved patient survival and reduction in LOS and cost for the severely injured in Period II.
Tesi sul tema "Rotating ventilator"
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Rashid, Dewan Md Harunur Mechanical & Manufacturing Engineering Faculty of Engineering UNSW. "Wake survey behind a rotating ventilator". Awarded by:University of New South Wales. School of Mechanical and Manufacturing Engineering, 2002. http://handle.unsw.edu.au/1959.4/19076.
Testo completoAbstract (sommario):
With environmental concern growing in both affluent and developing countries, roof top ventilators, a form of natural ventilation requiring only wind energy to ensure quality air circulation and comfort is becoming a considered choice of many households and industries. Unfortunately, however, many of these ventilators have evolved through trial and error and the flow physics associated with these ventilators is barely understood. The present experimental project was, therefore, undertaken as part of UNSW- Industry collaboration program funded under an Australian Research Council Grant to explore whether the aerodynamics forces acting on these ventilators during their operation could be obtained. A commercial roof top ventilator supplied by industry was, therefore, tested in an open jet wind tunnel of the University of New South Wales and the results are presented in this thesis. A novel feature of this project is the examination of the suitability of ???the three dimensional wake traverse??? technique to the wake of rotating ventilator. This technique has so far been applied with limited success to the wake of lifting bodies of fixed wing configuration only. In the absence of adequate data in the literature on rotating ventilator, the aerodynamics force components obtained by this technique have been compared against force balance measurements. The results show that the wake traverse technique is capable of determining lift and total drag forces associated with the ventilator flow during its operation from the pressure and velocity information gathered downstream of a ventilator in its wake. Generally, from these data, the technique also allows isolation of the profile and induced components of the drag force. However, from the induced drag value, while it is possible to determine the lift force, it is however, found that a more accurate value of lift force can be evaluated using axial vorticity formulation. The availability of the above technique which does not require measurements on the test specimen itself, will aid in providing a cost efficient investigation of the aerodynamic forces and consequently the performance of a roof top ventilator.
2
Wang, Juan. "Experimental study of two counter rotating axial flow fans". Thesis, Paris, ENSAM, 2014. http://www.theses.fr/2014ENAM0024/document.
Testo completoAbstract (sommario):
RESUME : Les machines axiales à rotors contrarotatifs subsoniques sont une bonne solution pour les industries où de fortes élévations de pressions et d'efficacités sont nécessaires sans augmenter le diamètre ou la vitesse de rotation des rotors. Néanmoins, le comportement des CRS et les paramètres impactant ses performances ne sont pas encore totalement compris. Cette thèse mène une investigation expérimentale sur la performance et les paramètres influents sur un étage contrarotatif. La technique de design et les méthodes de mesure sont repris sur une thèse précédente réalisée au laboratoire Dynfluid (Arts et métiers ParisTech). Trois étages contrarotatifs ont été fabriqués (JW1, JW2 et JW3) et testés sur le banc d'essai normalisé AERO2FANS. Ces machines ont été conçues pour avoir le même point de fonctionnement mais avec une répartition de charge différente. Les résultats expérimentaux se concentrent dans un premier temps sur JW1. Les grandeurs physiques regardées sont l'efficacité globale et l'élévation de pression statique pour juger de la performance globale de la machine. La fluctuation de pression pariétale et le champ de vitesse sont aussi mesurés. L'impact du changement de rapport de vitesse ou la distance entre les deux rotors sur la machine JW1 a été étudiée grâce aux grandeurs physiques décrits précédemment. Enfin dans une dernière partie, les trois machines sont comparées toujours grâce aux grandeurs physiques définies précédemmentABSTRACT : The counter rotating subsonic axial flow fans could be a good solution for applications where the highly improved static pressure and efficiency are required without the increase of rotational speed and fan diameter. However, the mechanisms of high performance CRS and parameters influences are not well understood nowadays. This thesis is an experimental investigation of the performance and parameter studies of two counter rotatingaxial flow ducted fans. The design and measurement methods are based on the previous research work in Laboratory Dynfluid (Arts et Métiers ParisTech). Three Counter Rotating Stages (CRS) (named JW1, JW2 and JW3) are developed and tested on a normalized test bench (AERO2FANS). These systems have same design point and differ by the distribution of loading as well as the ratio of angular velocity between the Front Rotor (FR) and Rear Rotor (RR). The first part of results focus on the JW1. The overall performance is obtained by the experimental results of the static pressure rise and static efficiency, as well as the wall pressure fluctuations recorded by a microphone on the casing wall. The parameter study is conducted to investigate the effects of the axial distance and the ratio of angular velocity between the FR and RR on the global performance and flow fields measured by Laser Doppler Velocimetry (LDV).The last part of the work is devoted to analyze the differences of the three CRS with different distribution of work, in terms of the global performance and flow features
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Tucker, Brandon Raye. "Reducing the incidence of ventilator-associated pneumonia with selected positional strategies". Honors in the Major Thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1512.
Testo completoAbstract (sommario):
This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.Bachelors
Nursing
Nursing
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Ho, Pui-yee, e 何佩兒. "Continuous lateral rotation therapy in preventing pulmonary complications in mechanically ventilated patients: an evidence-based guideline". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48335356.
Testo completoAbstract (sommario):
Immobility is one of the factors associated with the accumulation of respiratory secretion in mechanically ventilated patients. Placing patients in a semi-recumbent position between 30° and 45° and frequent manual turning in every two hours are the standard ventilator nursing care practice adopted worldwide. However, the prevalence of pulmonary complications remains high. The use of continuous lateral rotation therapy (CLRT) to improve drainage of secretion within the lung and the lower airways was proposed and has been investigated in numerous studies.
The purposes of this dissertation are (1) to perform a comprehensive systematic review for a critical appraisal of the current evidence on the use of CLRT to prevent pulmonary complications in mechanically ventilated patients, (2) to develop an evidence-based guideline and to assess the implementation potential, and (3) to develop an implementation and evaluation plan for translating the guideline to an adult intensive care unit (ICU) of a teaching hospital in Hong Kong.
In order to identify studies that compared CLRT with the standard care, four electronic databases, including CINAHL Plus, Medline, British Nursing Index and PubMed, were searched. 94 studies were identified and eight of them met the inclusion criteria. These studies included one randomized controlled trial (RCT), two non-randomized controlled clinical trials, one pretest-posttest clinical trial and four retrospective cohort studies. The quality of these reviewed studies was assessed by using the appraisal instruments of the Scottish Intercollegiate Guidelines Network. Four of the reviewed studies were graded as high quality. No major adverse patient outcome was reported. Instead, beneficial patient outcomes that reached statistical significance were consistently reported in the CLRT group. There were reductions in ventilator-associated pneumonia (VAP), atelectasis, duration of mechanical ventilation and length of stay. However, its effect on health care cost and mortality was inconclusive.
The implementation potential, in terms of the transferability, feasibility, and the cost-benefit ratio, was considered as high in the target setting. Based on the synthesized finding, a CLRT guideline is developed and is proposed to translate into practice. The implementation plan includes a communication plan with stakeholders and a pilot test. The guideline will be revised after the trial run of the proposed innovation for one and a half months. A full-scale controlled trial using a quasi-experimental design will be conducted. The primary outcome is to evaluate whether there is a reduction in the prevalence of VAP after the use of CLRT. According to previous studies, the use of CLRT can lead to a 49% reduction in VAP. The proposed innovation will be considered as clinical effective when similar observation is obtained.published_or_final_version
Nursing Studies
Master
Master of Nursing
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Azzam, Tarik. "Aérodynamique et contrôle de l'écoulement de jeu dans un ventilateur axial obtenu par rotomoulage". Thesis, Paris, ENSAM, 2018. http://www.theses.fr/2018ENAM0080/document.
Testo completoAbstract (sommario):
Aujourd’hui, la fabrication des turbomachines est conditionnée par des normes de plus en plus restrictives. L'enjeu industriel pour les chercheurs est d'envisager des solutions optimales visant à réduire les sources de perte d'énergie, d'instabilité et du bruit, en particulier l'écoulement de jeu (débit de fuite). Des actions préliminaires ont été élaborées à Arts & Métiers ParisTech sur le rotomoulage du ventilateur axial de refroidissement d'automobile. L'idée de ce travail est d'utiliser la forme creuse induite par le rotomoulage afin de l'exploiter dans le controle de l'écoulement de jeu radial par soufflage rotatif. Pour cela, la virole comporte des trous d'injection orientés de façon à réduire simultanément le débit de fuite et le couple. Dans ce travail, trois parties ont été traité. La première concerne la réalisation du ventilateur par rotomoulage. La deuxième concerne l'étude expérimentale menée dans le banc d'essai ISO 5801. Cette étude comporte la réalisation d'un montage dédié au contrôle par soufflage rotatif, la métrologie menée pour la détermination des performances globales et la caractérisation de la vitesse axiale du sillage proche. La troisième partie traite la modélisation numérique des conditions expérimentales rentables ensuite l'extrapolation du travail vers des taux d'injection importants. Pour ce dernier, on arrive à annuler le débit de fuite avec un gain considérable du couple mettant ainsi le ventilateur en autorotationNowadays, the manufacture of turbomachinery is conditioned by more and more restrictive rules. The industrial challenge for researchers has to consider optimal solutions to reduce sources of energy loss, instability and noise, particularly the tip clearance flow (leakage flow rate). Preliminary actions have been developed at Arts & ParisTech on rotational molding process used for the automobile cooling axial fan. The idea of this work is to use the hollow shape induced by rotational molding process in order to exploit it in the control of tip clearance flow through rotary steady air injection. For this, the shroud ring is composed of injection holes oriented in such away to reduce both of leakage flow rate and the torque. In this work, the thesis focuses on three parts. The first concerns the build of the fan by rotational molding process. The second concerns the experimental study carried out in the ISO 5801 test bench. This study involves the realization of drive system dedicated to rotary steady air injection, metrology for performance determination and the characterization of the near wake axial velocity. The third part deals with the numerical modeling of efficient experimental conditions, then the extrapolation of work towards high injection rates. For this latter, it is possible to cancel leakage flow rate with a considerable gain of the torque thus putting the fan in autorotation
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Grasso, Gabriele. "Development of hybrid methods for the computation of tonal and broadband fan noise source and propagation". Thèse, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/11790.
Testo completoAbstract (sommario):
Ces travaux de doctorat portent sur la réduction du bruit d'origine aérodynamique émis
par les ventilateurs et les doublets d'hélices contra-rotatifs. La méthodologie proposée
consiste à intégrer des méthodes rapides et précises de prédiction des niveaux sonores
dans le processus de conception. Cette thématique a vu son intérêt augmenter depuis que
l'Union Européenne a restreint les limites d'exposition au bruit en milieu de travail et
dans les zones habitées à proximité des aéroports.
Parmi les méthodes numériques employées en aéroacoustique, les méthodes hybrides de
prédiction du bruit sont considérées comme particulièrement appropriées pour la conception
automatisée du fait de leur coût modéré en temps de calcul. Ces méthodes séparent
la résolution de l'écoulement aérodynamique de celle de la génération du bruit et de sa
propagation en champ lointain. L'écoulement aérodynamique est obtenu par simulation
numérique, tandis que l'acoustique est traitée par méthodes analytiques. Ces méthodes
analytiques développées et validées pour déterminer le bruit d'un profil aérodynamique
placé dans un écoulement turbulent seront étendues pour traiter le réponse acoustique de
pales en rotation.
Ces travaux se concentrent sur deux configurations de ventilateurs basses vitesses. La première configuration traitée est le doublet d'hélices contra-rotatif de 4.2m de diamètre de la
soufflerie L-1 de l'Institut von Karman (VKI). Ce système permet d'étudier le phénomène
de bruit tonal et à large bande dû à l'impact des sillages turbulents, générés par l'hélice
amont, sur l'hélice aval. La deuxième configuration traitée est un ventilateur à quatre pales
du CETIAT (France) installé seul dans un large plenum. Ce système permet d'étudier le
bruit propre ou bruit de bord de fuite causé par l'interaction des tourbillons générés par
l'écoulement autour de la pale avec le bord de fuite de la pale. Pour cette configuration,
des données expérimentales sont rendues disponibles dans le cadre d'un projet commun
entre le VKI et le CETIAT. Les méthodes hybrides sont développées et mises en oeuvre
pour ces deux mécanismes de bruit présents dans les deux configurations de ventilateur.
L'objectif de ces travaux de thèse est d'employer les méthodes hybrides ainsi calibrées et
validées pour réaliser l'optimisation du doublet d'hélices contra-rotatif de la soufflerie L-1.
Le coeur de ces travaux portera sur l'extension des méthodes hybrides pour la prédiction
du bruit d'un profil dans un écoulement turbulent uniforme au cas du bruit tonal et à large
bande d'interaction de sillages et du bruit à large bande de bord de fuite dans des ventilateurs
basses vitesses. Il sera montré qu'il est possible de déterminer le spectre de bruit de
manière rapide et précise en s'appuyant sur la connaissance du champ aérodynamique dont
les quantités seront extraites de simulations numériques stationnaires (RANS) pour alimenter
la formulation analytique retenue. Cette dernière doit être adaptée au mécanisme
de bruit étudié, à savoir l'interaction d'une pale de ventilateur avec un sillage ou celle du
bord de fuite avec la turbulence qui s'est développé le long de la pale. Les deux mécanismes
de bruit sont d'abord modélisés avec des fonctions analytiques qui sont calibrés avec les
données des simulations numériques. Les modèles de sources de bruit ainsi que les estimations finales de spectre de bruit sont comparées aux données expérimentales disponibles et
à des simulations directes. Enfin la méthodologie retenue est mise en oeuvre dans le cadre
de l'optimisation du doublet d'hélices L-1 au moyen d'un algorithme génétique. L'étude
détaillée de la sensibilité des paramètres et des contraintes de l'optimisation apporte un
nouveau regard sur l'optimisation multi-objectif efficacité-bruit qui sera de plus en plus
utilisée pour la conception de turbomachine dans le futur.Abstract : The context of this thesis is the reduction of noise emitted by ventilation fans and aeronautical counter-rotating open rotors, which will be achieved by implementing fast and accurate noise prediction methods in the design process. The interest towards this subject has increased since the European Union enforced lower limits of exposure to noise in work environments and also to environmental noise in the proximity of airports. In the field of computational aeroacoustics, hybrid methods for noise prediction are considered particularly suitable for use in an automated design procedure due to their low computational cost. In fact they split the description of the flow field, which is made by computational fluid dynamics, from the quantification of the source of noise and of its propagation, obtained by using analytic formulations. Such analytic methods have already been used successfully for the prediction of the noise emitted by an airfoil placed in a turbulent flow; it is therefore natural to try to extend their applicability to the case of rotating blades. Two application cases have been chosen for this thesis. The first one is the 4.2 m diameter counter-rotating fan of the von Karman Institute (VKI) L1 low-speed wind tunnel, which is used to study the phenomenon of wake-interaction tonal and broadband noise. The second application case is a four-bladed low-speed ventilation fan in which the dominant source of noise is the trailing-edge or self-noise caused by the turbulent eddies passing over the trailing-edge of the blade. In this case, an experimental database has been made available by CETIAT, France, in the framework of a collaborative project with VKI. The final step of the project will be to use the prediction codes developed for both the noise phenomena in the geometric optimization of the L1 counter-rotating fan. The fundamental question that will be addressed in the thesis is how to extend the hybrid CFD-analytic methods to predict noise from an airfoil in a uniform turbulent flow to the case of tonal and broadband wake-interaction noise and trailing-edge broadband noise in low-speed fans. It will be shown that it is possible to provide a fast and reasonably accurate prediction of the spectrum of noise emitted by low-speed fans by extracting flow data from Reynolds Averaged Navier-Stokes (RANS) simulations and using them as input to Amiet's analytic formulation, provided that this has been carefully adapted to the studied noise generation phenomenon, i.e. the interaction of the leading-edge of a fan blade with an incoming wake or of the trailing-edge with the turbulent boundary layer over the blade surface. Concerning the methodology, both noise generation mechanisms will first be modeled with analytic functions, then the necessary flow field input will be extracted from RANS simulations and the models will be validated with respect to experimental data, whenever possible, or to higher fidelity simulations. The last step of the project is the application of these noise prediction methods to the shape optimization of the L-1 fan blades by means of a genetic algorithm. The sensitivity analysis of the design parameters and of the constraints used in the optimization process provides a new perspective on the multi-objective efficiency-noise optimization approach which will be increasingly used in turbomachinery design in the future.
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Bergh, Alison. "The effect of passive thoracic flexion-rotation movement on the total static compliance of the respiratory system and respiratory responses in ventilated patients". Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/408.
Testo completo
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Sanchez, Marc. "Etude des extracteurs d'air hybrides éoliens : conception de géométries et analyse des écoulements". Thesis, Perpignan, 2015. http://www.theses.fr/2015PERP0040/document.
Testo completoAbstract (sommario):
Ce travail de thèse concerne l'étude d'extracteurs d'air hybrides éoliens. Il se décompose en des investigations amont et appliquées. Dans la partie amont, des simulations fines ont été effectuées en conduite carrée avec et sans rotation, pour des nombres de Reynolds turbulents de l'ordre de 600, afin d'analyser l'impact de la rotation sur la turbulence. Elles ont montré que la rotation rompt la symétrie de l'écoulement. La partie appliquée est dédiée à la conception d'une nouvelle géométrie d'extracteur d'air. Cette géométrie a été proposée à partir de l'analyse de simulations RANS. Ses performances ont été confirmées par des mesures expérimentales sur banc d'essais. Les tests en soufflerie d'un système de captage d'énergie éolienne, conçu pour l'extracteur, ont mis en évidence son adéquation au régime de fonctionnement de l'extracteur. Les essais expérimentaux de l'extracteur complet, montrent que le système de captage apporte une part significative de l'énergie. Des essais en soufflerie ont permis d'observer le comportement global de l'extracteurThis PhD work concerns the study of hybrid air extractors. It is composed of upstream and applied investigations. In the upstream part, fine simulations are realized in square duct flow with and without rotation to analyse the impact of rotation on turbulence. It is found that rotation removes symmetry property of the flow with turbulent Reynolds number of 600. The applied part is dedicated to the conception of a new air extractor geometry. This geometry is proposed from the analyse of RANS simulations. Its performances are confirmed by experimental measurements on test rig. Wind tunnel tests of a wind power capturing system, designed for the extractor, show a good adequation to the operating regime of the extractor. Experimental investigations on the complete air extractor, show the wind power capturing system brings a significant part of the energy. Wind tunnel tests allow to observe the complete air extractor behaviour
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Kuldavletova, Olga. "L'intégration multisensorielle fonctionnelle et la plasticité des réflexes vestibulaires Vestibulo-sympathetic Reflex in Patients With Bilateral Vestibular Loss Influence of Graviceptor Stimulation Initiated by Off-Vertical Axis Rotation on Ventilation Effect of self-motion perception on autonomic control Vestibulo-Ocular Responses, Visual Field Dependence, and Motion Sickness in Aerobatic Pilots". Thesis, Normandie, 2020. http://www.theses.fr/2020NORMC405.
Testo completoAbstract (sommario):
L’objectif de ce travail de thèse était d’évaluer le rôle du système vestibulaire dans l’homéostasie en relation avec l’orientation.Nous avons évalué les réponses vestibulaires (1) dans une population normale pour évaluer le niveau d’implication des différents systèmes sensoriels dans la régulation cardiovasculaire et respiratoire et (2) dans des populations présentant des informations vestibulaires perturbées : soit des patients avec un déficit vestibulaire bilatéral soit des pilotes de voltiges aérienne.Les résultats indiquent que les informations vestibulaires et celles des gravicepteurs du tronc s’associent pour réguler la réponse respiratoire lors de la rotation à axe incliné selon la gravité (RAIG). La contribution respective des récepteurs vestibulaires et des gravicepteurs dans cette réponse varie en fonction des individus. Une autre étude a testé l’hypothèse selon laquelle la modulation de la réponse cardio-vasculaire par le système vestibulaire peut être influencée par les informations visuelles pendant la RAIG. Les résultats préliminaires de cette étude ont montré que la stimulation RAIG a un effet sur les valeurs moyennes des paramètres cardio-vasculaires. L'effet modulateur de la RAIG sur la pression artérielle a également été démontré. Cette modulation de réponse, et plus particulièrement la phase, variait entre les individus, ce qui peut indiquer la nature neuronale de la modulation observée. Un effet de la stimulation visuelle sur la modulation semble être également présent, mais une analyse plus approfondie est nécessaire pour confirmer ce résultat. Dans une autre étude, il s’est avéré que des patients présentant une déficience vestibulaire bilatérale avaient la même réponse cardio-vasculaire aux changements de position de la tête pendant le protocole « head down neck flexion » que les sujets témoins. Ces résultats indiquent que cette reconstruction du réflexe vestibulo-sympathique semble provenir de sources sensorielles autres que labyrinthiques. Enfin, nous avons étudié les pilotes de voltige aérienne comme modèle de sujets subissant des stimulations vestibulaires intenses et inhabituelles. Nous n'avons pas observé l’habituation vestibulaire attendue lors d’explorations fonctionnelles vestibulaires (RAIG et échelon de vitesse) en comparaison avec des sujets témoins, en revanche les pilotes étaient moins sensibles au mal des transports. Nous suggérons que les pilotes ne développent pas d'habituation vestibulaire comme attendu car ils ont besoin des réponses vestibulaires préservées et non altérées pour maintenir une performance optimum lors des activités de voltige aérienne.Nous concluons que pour générer des réponses en lien avec l’orientation, le système nerveux central intègre les signaux vestibulaires et non-vestibulaires et est sujet à un certain niveau de plasticité en conditions sensorielles altérées. Ce traitement multisensoriel est régulé individuellement, avec un poids variable des informations vestibulaires, en fonction de l'état sensoriel et des exigences liées à l’activitéThe aim of this thesis was to specify the role of the vestibular system in the orientation-related homeostasis. We evaluated vestibular responses to changes in orientation in space (1) in normal population to reveal in what proportion different sensory systems are implicated in the generation of the cardio-vascular and respiratory responses, and (2) in populations with altered vestibular afference: bilateral vestibular loss patients and aerobatic pilots.The results indicated that the vestibular system cooperates with trunk graviceptors to evoke respiratory response to changes in orientation during Off-Vertical Axis Rotation protocol (OVAR). The contribution of each sensory source was found to vary between individuals. Another study tested the hypothesis that the vestibular modulation of cardio-vascular parameters can be influenced by visual input during OVAR. Preliminary results from this study have demonstrated that the OVAR stimulation has an effect on the mean cardio-vascular parameters. The modulatory effect of OVAR on the arterial pressure has also been shown. The phases of modulation were varying between individuals which can indicate the neural nature of the observed modulation. The effect of visual stimulation on modulation has been detected, however further analysis is required. In another study, subjects presenting bilateral vestibular loss were shown to have the same cardio-vascular response to changes in the position of the head during Head-Down-Neck-Flexion protocol (HDNF) as normals. This reconstruction of the vestibulo-sympathetic reflex in human seems to originate from the sensory sources other than labyrinthine. Finally, we studied aerobatic pilots as humans experiencing intense and unusual vestibular stimulations. We have not revealed the expected vestibular habituation in the study using the OVAR and EVAR (Earth-Vertical Axis Rotation) stimulations, but were significantly less susceptible to motion sickness. We suggest that the pilots do not develop habituation, as they require unsuppressed responses for a better performance.We conclude that to generate the orientation-related responses, the Central Nervous System integrates the vestibular and non-vestibular signals and is subject to plastic changes in altered sensory conditions, if the response needs to be changed or restored. This multisensory processing is individually tuned, with the variable portion of vestibular impact in this processing, depending on activities, sensory state and the requirements to the response
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Rashid, Dewan Md Harunur. "Wake survey behind a rotating ventilator /". 2002. http://www.library.unsw.edu.au/~thesis/adt-NUN/public/adt-NUN20031013.125434/index.html.
Testo completoCapitoli di libri sul tema "Rotating ventilator"
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Liu, Rong-hua, Yong-jun Li, Peng-fei Wang, Wei Shu e Shang-xu Gou. "Influence of the Ratio of the Blowing and Sucking Flow on the Wall-Rotating Circulating Airflow in Fully Mechanized Excavation Face". In Proceedings of the 11th International Mine Ventilation Congress, 49–57. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-13-1420-9_5.
Testo completo
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M., Kannan. "Experimental Procedure for Rotating Ventilated Disk". In Flow Measurement. InTech, 2012. http://dx.doi.org/10.5772/38086.
Testo completoAtti di convegni sul tema "Rotating ventilator"
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Keshavarz, Seyed Ali, Mazyar Salmanzadeh e Goodarz Ahmadi. "Computational Modeling of Particulate Pollutant Transport in a Ventilated Room in the Presence of Two Heated Breathing and Rotating Manikins". In ASME 2017 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fedsm2017-69102.
Testo completoAbstract (sommario):
Recently, attention has been given to indoor air quality due to its serious health concerns. Clearly the dispersion of pollutant is directly affected by the airflow patterns. The airflow in indoor environment is the results of a combination of several factors. In the present study, the effects of thermal plume and respiration on the indoor air quality in a ventilated cubicle were investigated using an unsteady computational modeling approach. The person-to-person contaminant transports in a ventilated room with mixing and displacement ventilation systems were studied. The effects of rotational motion of the heated manikins were also analyzed. Simulation results showed that in the cases which rotational motion was included, the human thermal plume and associated particle transport were significantly distorted. The distortion was more noticeable for the displacement ventilation system. Also it was found that the displacement ventilation system lowered the risk of person-to-person transmission in an office space in comparison with the mixing ventilation system. On the other hand the mixing system was shown to be more effective compared to the displacement ventilation in removing the particles and pollutant that entered the room through the inlet air diffuser.
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Ivensky, V., e T. May. "355. Unique Rotating Local Exhaust Ventilation System". In AIHce 2000. AIHA, 2000. http://dx.doi.org/10.3320/1.2763704.
Testo completo
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Liu, Pin, Yingzi Jin, Yanping Wang, Hongyu Qian e Li Zhang. "Study on the Aerodynamic Performance of Small Axial Flow Counter-Rotating Fans". In ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-06091.
Testo completoAbstract (sommario):
Small axial flow fans are used as cooling components for computers, electronic equipments and other electronic components. With the increasing power of electrical equipment, the demand for lower noise and higher ventilation of cooling fans to improve heat transfer effects is also increasing. Traditional methods of improving ventilation by raising the fan’s rotation speed causes a decrease in efficiency and an increase in noise. The researchers have found that higher pressure, ventilation and efficiency can be achieved in a small space by counter-rotating fans than single fans. In this paper, 3D simulation has been done on flow field of counter-rotating fans for heat exchange, and the method of large eddy simulation (LES) and FW-H acoustic model have been used to simulate the distribution of noise field. The frequency spectrum from different sound sources has been analyzed, and the optimal ranges of the distance and gap between rotors have been determined. All that will provide a theoretical basis for researches on their characteristics and structure design.
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Himei, Kohei, e Hajime Yamaguchi. "Numerical Study on Performance of Surface Piercing Propeller using RANS Approach". In SNAME 13th International Conference on Fast Sea Transportation. SNAME, 2015. http://dx.doi.org/10.5957/fast-2015-044.
Testo completoAbstract (sommario):
Surface Piercing Propeller (SPP) can achieve high propulsive efficiency on high-speed vessels planing to reduce the frictional resistance of hull. It has the characteristic blade section and works partially submerged condition. The blades repeat entry to and exit from the water free surface and the suction sides and trailing edge of blades are exposed to ventilated cavitation while they are under the water. And interface near SPP is severely deformed by the high rotating blades. This working condition of SPP, therefore, makes it hard that propeller open characteristics are estimated with high reliability. Because SPP is unusual propeller having above difficulty of the performance estimation, the studies for SPP are few compared with large sized propellers for merchant ships. Although the various model tests had been carried out to understand the physical phenomena around various SPPs and their effects on propeller performances, they were not universal approach with standardized test conditions and propeller shape, as mentioned in 23th ITTC report and recommendation (2002). In applying the conventional calculation based on potential theory to SPP, there are many difficulties to model the physical phenomena theoretically. In calculations by Furuya (1984, 1985), thickness of blade and ventilated cavitation were non-consideration, and it was assumed that the suction side of the blade was fully ventilated in the water. In calculations by Young and Kinnas (2001), the interface deformation near SPP was not modeled theoretically. Therefore, they attributed the difference from experimental results to the effect of incompleteness of numerical modeling. On the other hand, CFD analysis can treat the effects of physical phenomena including thick ventilated cavitation and the sharp deformation of interface around SPP. In addition, the characteristic blade shape is modeled accurately without the geometric limitation in CFD. In this paper, typical SPP with experimental results open to the public is analyzed by CFD-RANS approach using Volume of Fluid (VOF) method based on interface-capturing algorithm at wide range of propeller advance coefficient J. Regarding propeller open characteristics, the 6-component force/moment fluctuations by blade rotations, and ventilation patterns, analyses results are compared with measured values. Moreover, the results of simulations in various Froude numbers and Weber numbers are evaluated whether their effects were negligible when they are sufficiently high, in the same manner as the results found by the other’s experimental studies (Shiba, 1953; Brandt, 1973).
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Abbaszadeh, Morteza, Parvin Nikpour Parizi e Ramin Taheri. "A Novel Approach to Design Reversible Counter Rotating Propeller Fans". In ASME 2012 Gas Turbine India Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gtindia2012-9657.
Testo completoAbstract (sommario):
Because of their high performance and unique abilities like producing none-rotating wake, Counter Rotating Propellers (C.R.P.) are being used in many advanced propulsion or ventilation systems. But due to complicated design procedure of C.R.P. fans up to now it was not possible to apply the concept in reversible systems. For the first time in this research, a new method presented to design a reversible counter rotating propeller system. This method is based on designing a basic C.R.P. by a reliable edition of blade element theory to achieve maximum performance in main rotating course and then to optimize it in order to have almost same performance in reverse rotating course. After expressing concepts of the method, a basic model is designed to ensure the capability of the presented scheme. Design outcome was a Reversible C.R.P. (R.C.R.P) system with 0.5 meter in diameter and cross section of NACA2412 airfoil. This model is evaluated by using R.S.M. turbulence method through ANSYS Fluent commercial software package. Evaluation results showed that system has efficiency of 0.85 in main course and 0.78 in reverse course by which a good performance for a small size reversible system can be captured.
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Chow, W. K., N. Cai e Y. Gao. "Numerical Study of Internal Fire Whirls in a Kitchen With Ceiling Vents". In ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ht2013-17103.
Testo completoAbstract (sommario):
The characteristics of flame rotation induced by a fire at the top of kitchen stove were studied numerically with Computational Fluid Dynamics (CFD). Four cases with different locations of fire sources and vents were set up; simulations of swirling air flow and temperature distributions in the kitchen room were carried out. Ventilation by ceiling vents was identified as the necessary condition for internal fire whirl. Recommendations on the design of kitchen ventilation system were made.
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Taniyama, Yoshihiro, Yasuo Kabata, Yoshio Hashidate, Kazunori Shioda e Hitoshi Katayama. "Improvement of Ventilation Analysis in Turbine Generator". In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-80132.
Testo completoAbstract (sommario):
Most of large electric rotating machines, for example, the generator and the motor adopt the cooling type that the coolant gas such as hydrogen and air is circulated inside. To improve the performance of the machine and the competitiveness of the product, development of cooling technology such as efficient and effective ventilation of coolant gas becomes important. In addition, it is also important to calculate the coolant gas distribution with high accuracy. This is because it is necessary to cancel the increase in the heat density by it. In this study, a new cooling design system for the turbine generator is developed, where calculation accuracy of the coolant gas distribution is developed and calculation time is reduced. The following shows the outline of this technical approach: 1) Development of a method of the fluid network system analysis that satisfy continuous condition and pressure condition in each branch, and considers divergence loss on branch point and convergence loss on joint point by the one dimensional transient fluid analysis. 2) A pressure loss database such as divergence loss on branch point and convergence loss on joint point reflects knowledge by the elemental experiment and 3D-CFD. In this paper, a basic code of the fluid network system analysis is introduced and verified by a one-slot ventilation model with half axial length of actual stator core.
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Cyrus, Vaclav, Jiri Pelnar e Jan Cyrus. "Reversing of Axial Flow Fans for Ventilation". In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-46062.
Testo completoAbstract (sommario):
Changing the flow direction in fans is frequently required in emergency situations in traffic tunnels, chemical plants and mines ventilation. Reverse flow in axial flow fan is often achieved using two methods: a) Changing direction of fan rotation and turning the stator vanes (Method I). b) Turning / resetting rotor blades during fan rotation (Method II). The required volume flow rate at flow reversal is usually at least 60% valid for normal fan working point. The motivation of the present paper is to compare the aerodynamic performance and 3D flow mechanism in fan stage at flow reversal carried out by the two methods above. In our paper conditions of the flow reversal are discussed. Theoretical relations are derived for both methods using fundamental equations valid for internal aerodynamics of axial flow compressors and fans. Parameters of three fan axial stages were measured on a 600 diameter test rig at standard and reverse conditions. The investigated fan ventilation stages had a design flow coefficient of 0.35 to 0.40 and pressure coefficient of 0.30. Flow field measurements were carried out with the use of 5-hole pressure probes in the stage planes. The blade rows flow mechanism at the standard and reverse conditions is described using test data obtained for both flow reversal methods. The flow simulation results were also used. It has been found in our investigations that moderate aerodynamic loading of the ventilation fans has better aerodynamic performance during flow reversal if Method II is used. Fan designers and users making the final decision relating to the selection of the flow reversal method should also include the reliability and cost of the reverse fan design with blade turning mechanism.
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Hagesteijn, Gerco, Karola van der Meij e Cornel Thill. "Distributed Propulsion: A Novel Concept for Inland Vessels". In ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-41845.
Testo completoAbstract (sommario):
In the drive to reduce the fuel consumption of inland vessels, one of the main limitations, the risk of propeller ventilation was investigated. The aim was to reduce the resistance of the vessel, while at the same time an acceptable margin against propeller ventilation had to be assured. A typical inland vessel has up to two high loaded relative large propellers, with tip regions in the lighter loading condition above the water line. To eliminate the risk of propeller ventilation, these ships often have inbuilt shape features such as tunnels and skirts, only having the intention to avoid air being drawn by the rotating propeller. These devices however have a noticeable own resistance, imposing a mortgage to the ship’s total resistance. Current design practice for these devices is that as long as you cannot quantify a risk, take care of a sufficient safety margin. With the research done within the EU-funded STREAMLINE project new insights were gained into the prediction of air suction. As a result, the margin against ventilation could be reduced which resulted into a large reduction of the resistance of the vessel. Reducing the high loading of propellers means to gain efficiency with at the same time reducing the risk of propeller ventilation as the suction by the propeller(s) can be decreased as well. This leads to the idea of a “distributed thrust” concept (DTC). Within STREAMLINE DST developed a sample case for such a novel design with six thrusters, with the aim to reduce ventilation against zero and to achieve maximal performance improvements. The measurements were carried out in MARIN’s Depressurized Wave Basin (DWB). These tests were carried out with a 1:10 scale ship model, in sailing condition, and depressurized conditions. In this way, the correct representation of cavitation and possible ventilation bubbles and vortices is ensured, resulting in a correct physical behavior. At the same time synchronized high speed video recordings were made to acquire insight in the occurring phenomena. Within the project CFD calculations were carried out, aimed at characterizing the performance, loads, cavitation nuisance and ventilation risk in full-scale operating conditions. Validation of these calculations was done using the towing tank results.
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Megerle, Benjamin, Timothy Stephen Rice, Ivan McBean e Peter Ott. "Numerical and Experimental Investigation of the Aerodynamic Excitation of a Model Low-Pressure Steam Turbine Stage Operating Under Low Volume Flow". In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68384.
Testo completoAbstract (sommario):
The diversification of power generation methods within existing power networks has increased the requirement for operational flexibility of plants employing steam turbines. This has led to the situation where steam turbines may operate at very low volume flow conditions for extended periods of time. Under operating conditions where the volume flow through the last stage moving blades (LSMBs) of a low-pressure (LP) steam turbine falls below a certain limit, energy is returned to the working fluid rather than being extracted. This so-called “ventilation” phenomenon produces non-synchronous aerodynamic excitation, which has the potential to lead to high dynamic blade loading. The aerodynamic excitation is often the result of a rotating phenomenon, with similarities to rotating stall, which is well known in compressors. Detailed unsteady pressure measurements have been performed in a single stage model steam turbine operated with air under ventilation conditions. Detailed analysis revealed that the rotating excitation mechanism observed in operating steam turbines, is reproduced in the model turbine. 3D CFD has been applied to simulate the unsteady flow in the air model turbine. The numerical model consists of the single stage modeled as a full annulus, as well as the axial-radial diffuser. An unsteady CFD analysis has been performed for sufficient rotor revolutions such that the flow is globally periodic. It has been shown that the simulation reproduces well the characteristics of the phenomenon observed in the tests. The detailed insight into the flow field allows the drawing of conclusions as to the nature of the excitation mechanism. One result is that the LSMB tip clearance flow is found to have very little or no effect on the characteristics of mechanism for the case studied.