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Simulation the axial-flow fans and its performance evaluation.Kang, Tsang-Chou 30 July 2002 (has links)
This thesis studies to simulate the axial flow fans by using the CFD software. Designing two geometries types of axial flow fans which had different twist angles and the same contour¡]70¡Ñ70¡Ñ15 mm¡^with the Joukowski airfoil; then, defining the boundaries shapes identical with the experimental instrument.
In the part of numerical calculation, varying the rotation speed ¡]rpm¡^,volume flow rate¡]CFM¡^and seven types of turbulence models to simulate the flow fields and evaluate the axial flow fans performance curves. Utilizing the comparison of the experimental and simulate results to provide the appropriate turbulent models to periodic the performance curve precisely.
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Etude expérimentale de l'écoulement et de l'interaction entre deux rotors contrarotatifs subsoniques / Experimental study of the flow and the interaction in-between subsonic counterrotating axial-flow fansNouri, Hussain 18 December 2012 (has links)
Le développement de machines à forte vitesse spécifique et de taille réduite en régime subsonique suscite actuellement une forte demande dans de nombreux domaines industriels. Les machins à rotors contrarotatifs largement étudiées en aéronautique constituent une alternative efficace aux machines conventionnelles offrant de nombreux avantages : réduction de la vitesse de rotation, de l'encombrement radial et une grande flexibilité d'utilisation. Cependant, leur utilisation dans des applications subsoniques courantes nécessite une meilleure compréhension de leur fonctionnement et notamment de l'interaction inter-rotors pour mieux les concevoir. Ce travail a pour objectif d'étudier et de caractériser expérimentalement un étage contrarotatif fonctionnant en conduit, conçu avec le code de conception et d'analyse pour rotor et rotor-stator, MFT auquel on a implémenté une méthode de conception simple et rapide pour dessiner le rotor aval. On analyse en particulier l'effet de la distance axiale entre les rotors et l'effet du rapport de leur vitesse. Il met en évidence une nette amélioration des caractéristiques et du rendement global par rapport à une machine conventionnelle. Par ailleurs, plusieurs aspects de l'interaction entre les rotors sont constatés à travers des mesures locales à proximité des rotors. Le présent mémoire s'articule autour de quatre parties : conception d'un étage rotor-stator et d'un étage contrarotatif ; conception du dispositif expérimental normalisé, AERO²FANS pour les mesures de performances globales et locales instationnaires ; caractérisation et comparaison des deux étages et validation de la conception de MFT; enfin, étude des effets de la distance axiale et du rapport des vitesses sur les performances globales et locales. / Recently, the need for smaller axial fans with high specific speeds lead to the design of counter-rotating axial fans. The design of this kind of machines, which have promising aerodynamic performances, suffers from a lack of knowledge about their aerodynamics. Counter-rotating rotors, widely studied in aeronautics, are an effective alternative to conventional machines and offer many advantages: rotation ratio and diameter reduction, and high flexibility in use. However, a better understanding of their working and of the rotors interaction is required to enhance their design and to make them widely integrated in current applications. This experimental research work investigates on a ducted counter-rotating stage designed with a home code, MFT based on an inverse design method for rotors and rotor-stator stages, and to which a rapid and simple method is implemented to design the rear rotor. The study focuses on the effects of the rotation ratio and on the axial spacing between rotors. It highlights several aspects of the rotors interaction through global performance and local unsteady measurements. This dissertation is organized in four parts: rotor-stator and rotor-rotor stages design; design of the experimental facility, AERO²FANS allowing global performance and local unsteady measurements; comparison between the two stages and design validation; investigation on the effects of the rotation ratio and the axial spacing on the global and the local performances.
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Simultaneous measurement of air flow conditions and resultant blade and gearbox loading at large-scale cooling system fansMuiyser, Jacques 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Axial flow fans used in large-scale air-cooled steam condensers (ACSCs) may operate
under distorted inflow conditions. These conditions occur due to the prevailing wind
conditions, the presence of buildings, and the location of the fan within the ACSC. Fans
located on the periphery of the ACSC are affected the most due to their exposure to
strong winds and the inner fans drawing in air past them. Distorted inflow conditions
cause varying fan blade and gearbox loading conditions.
The purpose of the investigation was to simultaneously measure the inlet air flow
and the resultant blade and gearbox loading conditions of a single fan located on the
periphery of a large-scale ACSC. Inlet and heat exchanger bundle outlet air flow velocities
were measured using a combination of ultrasonic and propeller anemometers while
blade loading was measured with strain gauges attached at the neck of the specific blade
being monitored. Strain gauges were also attached to the low-speed fan shaft to measure
gearbox loading.
Measurements were recorded over a period of 8 days where it was found that increased
wind resulted in increased air flow in the axial direction of the fan, which then
caused a reduction in average blade loading. This was due to a decreased static pressure
rise over the fan. The fan blade was found to vibrate at its own natural frequency of
6 Hz when excited by the variable aerodynamic loading. The aerodynamic loading was
extracted from the measured data and was found to correlate well with previous experimental
work performed by Bredell et al. (2006a). Shaft bending stresses and torque were
found to oscillate at the fan’s rotational frequency of 2Hz with a large torque exerted on
the shaft during fan start-up. / AFRIKAANSE OPSOMMING: Aksiaalvloeiwaaiers wat by groot lugverkoelde stoomkondensors gebruik word, werk
dikwels onder verwronge inlaat lugvloei toestande wat geskied as gevolg van heersende
winde, die teenwoordigheid van geboue en die posisie van die waaier in die kondensor.
Waaiers wat geleë is op die rand van die kondensor word die meeste beïnvloed as gevolg
van blootstelling aan die sterk winde en dwarsvloei wat deur die binneste waaiers geïnduseer
word. Verwronge inlaat lugvloei veroorsaak gevolglik variërende waaierlem en
ratkas belastingstoestande.
Die doel van hierdie ondersoek was om terselfdetyd die inlaat lugvloei asook waaierlem
en ratkas belastingstoestande van ’n enkele waaier wat op die rand van ’n grootskaalse
lugverkoelde stoomkondensor geleë is, te meet. Waaier inlaat en warmteruiler
uitlaat lugvloei snelhede is gemeet met ’n kombinasie van ultrasoniese- en skroefwindsnelheidsmeters
terwyl die lem en ratkas belastings gemeet is met rekstrokies.
Metings is oor ’n tydperk van 8 dae geneem. Die bevindinge toon dat ’n toename
in windsnelheid ’n toename in aksiale lugvloei tempo, deur die waaier veroorsaak. ’n
Afname in die gemiddelde lembelasting is waargeneem as gevolg van ’n afname in die
waaier statiese druk. Daar is ontdek dat die waaierlem teen ’n natuurlike frekwensie van
6 Hz vibreer wanneer dit opgewek word deur die wisselende aerodinamiese belasting.
Die aerodinamiese belasting is verkry uit die gemete data en vergelyk goed met die numeriese
werk van Bredell et al. (2006a). Daar is ook bevind dat waaier-as buigspannings
en wringkragte ossileer teen die waaier se rotasiefrekwensie van 2Hz met ’n groot wringkrag
wat op die as uitgeoefen word wanneer die waaier aangeskakel word.
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Die invloed van versteurde inlaatvloeipatrone op aksiaalwaaiersVisser, J. G. J. 12 1900 (has links)
Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. / Thesis (MEng)--Stellenbosch University, 1990. / ENGLISH ABSTRACT: The causes of disturbances in the flow patterns at the
inlets of axial flow fans that are used in mechanical draft
cooling towers and the effects of these disturbances on the
fans, were investigated.
A scale model of a part of a mechanical draft cooling tower
used at a power station was built for the purpose of this
study. In the cooling tower the axial flow fans are
arranged in a matrix configuration. It was noted from the
scale model that the boundary fan was subjected to the
worst inlet disturbances and this had an adverse effect on
the flow it produced. Geometric alterations like the use
of guide vanes and rounded inlets improved the flow through
the boundary fan considerably. It was found that the
performance of the fans is a function of the number of fans
used and the elevation of the fans.
Several tests to determine the performance of the cooling
tower confirmed the results obtained from the experiments
on the scale model. It was also found that the speed and
direction of the prevailing wind have a significant effect
on the cooling tower.
Experiments to investigate the effects of cross-flow at the
inlet of a fan indicated an increased flow through the fan
at low cross-flow velocities and that the flow decreased at
high cross-flow velocities. / AFRIKAANSE OPSOMMING: Die invloed en oorsake van versteurde inlaatvloeipatrone op
aksiaalwaaiers wat in meganiese-trek koeltorings gebruik
word is ondersoek.
'n Skaaimodel van 'n deel van 'n meganiese-trek koeltoring
wat by 'n kragstasie gebruik word is gebou vir die doel van
die studie. Die aksiaalwaaiers wat in die koeltoring
gebruik word is in 'n matrikskonfigurasie gerangskik.
Vanaf die skaalmodel is waargeneem dat die randwaaier die
ergste versteuring by die inlaat ervaar, en gevolglik
minder vloei as die res van die waaiers in die opstelling
lewer. Die vloei deur die randwaaier is verbeter deur
verskillende geometriese wysigings soos leilemme en
inlaatafrondings aan te bring. Daar is gevind dat die
werking van die waaiers in die opstelling 'n funksie van
die hoeveelheid waaiers asook die grondvryhoogte is.
Om die werking van die koeltoring te bepaal is verskillende
toetse daarop uitgevoer. Die resultate het die geldigheid
van die skaalmodel bevestig. Daar is ook gevind dat die
heersende windsterkte en rigting 'n definitiewe invloed op
die koeltoring uitoefen.
Die invloed van 'n dwarsvloei by die inlaat van 'n enkele
waaier is ook eksperimenteel ondersoek. Die resultate toon
dat daar 'n vermeerdering in vloei deur die waaier by lae
dwarsvloeisnelhede plaasvind. Hoë dwarsvloeisnelhede
veroorsaak egter 'n vermindering in vloei.
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