Thesis (PhD (Mechanical and Mechatronic Engineering)--University of Stellenbosch, 1990.ENGLISH ABSTRACT: The ultimate goal of this project is to ensure a better understanding of the governing
mechanisms present when flow distorting components are installed in close proximity of
an axial flow fan.
The effect of different parameters on the operation of axial flow fans is investigated. These
parameters are divided into flow enhancing and flow reduction effects. The performance
of an axial flow fan can be enhanced by changing the tip clearance, by adding a solid
disc to the hub of the fan or by varying the number of fan blades. Flow reductions are
caused by components such as inlet grids, walkways and their supporting structures, heat
exchangers and windwalls.
The effects of flow enhancing components are measured and compared to the results of
other authors. The sensitivity of these effects to parameters such as the type of fan rotor
and the specific system in which the rotor is installed is highlighted.
The system effect (the interaction between the fan rotor and flow resistances in close
proximity of each other) of individual components, as well as the combination of different
components, is predicted both theoretically and experimentally. These predictions are
compared to measured data relevant to the components in an installation where the system
effects are present. The results are correlated to the kinetic energy flux coefficient of the
flow at different locations within the installation.
Experimental data obtained from a full scale unit (inlet shroud diameter of 9,216 m) are
used to compare to scaled data from the model (inlet shroud diameter of 1,542 m). The
hub to tip ratio of the axial flow fans investigated is 0,15.
The most important conclusions are that the performance of the type of axial flow fan
under investigation can be improved by reducing its tip clearance and by installing a solid
disc to the downstream side of the rotor. An increase in the number of blades of the fan
leads to only marginal improvements in the fan performance. The overall performance of
the system can also be improved by removing some of the flow resisting components, or
by changing their relative positions. All these conclusions are based on the assumption
that the power input to the fan rotor remains constant.AFRIKAANSE OPSOMMING: Die uiteindelike doel van hierdie projek is om te verseker dat die beherende meganismes wat
teenwoordig is wanneer vloeiversteurende komponente in die nabyheid van 'n aksiaalwaaier
geinstalleer word, beter verstaan word.
Die effek van verskillende parameters op die werkverrigting van aksiaalwaaiers word ondersoek.
Hierdie parameters word verdeel in vloeiverbeterings- en vloeiverminderingseffekte.
Die werkverrigting van 'n aksiaalwaaier kan verbeter word deur die lempuntspeling te verstel,
deur 'n soliede skyf aan die naaf van die waaierrotor te installeer, of deur die aantal
lemme te verander. Die vloeiverminderings word veroorsaak deur inlaatsiwwe, loopvlakke
en hul ondersteuningsstrukture, warmteruilers en windwande.
Die effekte van vloeiverbeteringskomponente word gemeet en vergelyk met die resultate
van ander outeurs. Die sensitiwiteit van hierdie effekte op parameters soos die tipe rotor
en die spesifieke stelsel waarin die rotor geinstalleer is, word uitgelig.
Die stelseleffek (die interaksie tussen die rotor van die waaier en vloei weerstande wat
naby mekaar geinstalleer is) van individuele, sowel as 'n kombinasie van verskillende
komponente, word teoreties en eksperimenteel voorspel. Hierdie voorspellings word dan
vergelyk met eksperimentele data wat van toepassing is op die komponente in 'n installasie
waar stelseleffekte voorkom. Die resultate word gekoppel aan die kinetiese energievloedkoeffisient
van die vloei by verskillende posisies binne die installasie.
Eksperimentele data, verkry vanaf 'n volskaaleenheid (inlaatmondstukdiameter van 9,216 m),
word met die geskaleerde data van die model (inlaatmondstukdiameter van 1,542 m) vcrgelyk.
Die naaf- tot hulsverhouding van die aksiaalwaaiers wat ondersoek word is 0,15.
Die belangrikste gevolgtrekkings is dat die werkverrigting van die tipe aksiaalwaaier wat
ondersoek word verbeter kan word deur die lempuntspeling te verminder en deur 'n soliede
skyf te installeer by die stroomaf kant van die rotor. 'n Toename in die aantal lemme
van die waaier lei slegs tot marginale verbeterings in die werkverrigting van die waaier.
Die totale werkverrigting van die stesel kan ook verbeter word deur sommige vloeiweerstandskomponente
te verwyder, of deur hulle relatiewe posisies te verander. Al hierdie gevolgtrekkings is gebasseer op die aanname dat die drywingsinset na die waaierrotor konstant
bly.260 leaves printed single pages, preliminary pages i-xxi and numbered pages Chapter 1/1.1-1.3, Chapter 2/2.1-2.17, Chapter 3/3.1.1-3.10, Chapter 4/4.1-4.18, Chapter 5/5.1-5.3, References pages R.1-R.7, Appendix A pages A.1-A.34, Appendix B pages B.1-B.34, Appendix C pages C.1-C.26, Appendix D pages D.1-D.16, Appendix E pages E.1-E.30, Appendix F pages F.1-F.39. Includes bibliography, list of tables, figures and symbols
