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.
iii
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/71805 |
| Date | 12 1900 |
| Creators | Muiyser, Jacques |
| Contributors | Els, D. N. J., Van der Spuy, S. J., Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 113 p. : ill. |
| Rights | Stellenbosch University |
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