Thesis (MScEng)--Stellenbosch University, 2006. / ENGLISH ABSTRACT: The Stellenbosch University Compressor Code (SUCC) has been developed for the purpose
of predicting the performance of axial flow compressors by means of axisymmetric inviscid
throughflow methods with boundary layer blockage and empirical blade row loss models.
This thesis describes the process of the implementation and verification of a number of stall
prediction criteria in the SUCC. In addition, it was considered desirable to determine how
certain factors influence the accuracy of the stall prediction criteria, namely the nature of
the computational grid, the choice of throughflow method used, and the use of a boundary
layer blockage model and a radial mixing model. The stall prediction criteria implemented
were the di®usion factor limit criterion, de Haller's criterion, Aungier's blade row criterion,
Aungier's boundary layer separation criterion, Dunham's, Aungier's and the static-to-static
stability criteria. The compressors used as test cases were the Rofanco 3-stage low speed
compressor, the NACA 10-stage subsonic compressor, and the NACA 5-stage and 8-stage
transonic compressors. Accurate boundary layer blockage modelling was found to be of great
importance in the prediction of the onset of stall, and that the matrix throughflow Method
provided slightly better accuracy than the streamline curvature method as implemented in
the SUCC by the author. The ideal computational grid was found to have many streamlines
and a small number of quasi-orthogonals which do not occur inside blade rows. Radial mixing
modelling improved the stability of both the matrix throughflow and streamline curvature
methods without significantly affecting the accuracy of the stall prediction criteria. De
Haller's criterion was over-conservative in estimating the stall line for transonic conditions,
but more useful in subsonic conditions. Aungier's blade row criterion provided accurate
results on all but the Rofanco compressor. The diffusion factor criterion provided over-
optimistic predictions on all machines, but was less inaccurate than de Haller's criterion
on the NACA 5-stage transsonic machine near design conditions. The stability methods
performed uniformly and equally badly, supporting the claims of other researchers that they
are of limited usefulness with throughflow simulations. Aungier's boundary layer separation
method failed to predict stall entirely, although this could reflect a shortcoming of the
boundary layer blockage model. / AFRIKAANSE OPSOMMING: Die Stellenbosch University Compressor Code (SUCC) is ontwikkel om die prestasie van aksiaalvloei kompressors te voorspel met behulp van aksisimmetriese nie-viskeuse deurvloeimetodes met grenslaagblokkasie en empiriese modelle vir die verliese binne lemrye. Hierdie tesis
beskryf die proses waarmee sekere staakvoorspellingsmetodes in die SUCC geïmplementeer
en geverifieer is. Dit was ook nodig om die effek van sekere faktore, naamlik die vorm
van die berekeningsrooster, die keuse van deurvloeimetode en die gebruik van `n grenslaagblokkasiemodel en radiale vloeivermengingsmodel op die akuraatheid van die staakvoorspellingsmetodes te bepaal. Die staakvoorspellingsmetodes wat geïmplementeer is, is die
diffusie faktor beperking metode, de Haller se metode, Aungier se lemrymetode, Aungier
se grenslaagmetode en die Dunham, Aungier en die statiese-tot-statiese stabiliteitsmetodes.
Die kompressors wat gebruik is om die metodes te toets is die Rofanco 3-stadium lae-spoed
kompressor, die NACA 10-stadium subsoniese kompressor en die NACA 5- en 8-stadium
transsoniese kompressors. Daar is vasgestel dat akkurate grenslaagblokkasie modelle van
groot belang was om `n akkurate aanduiding van die begin van staking te voorspel, en dat,
vir die SUCC, die Matriks Deurvloei Metode oor die algemeen 'n bietjie meer akkuraat as die
Stroomlyn Kromming Metode is. Daar is ook vasgestel dat die beste berekeningsrooster een
is wat baie stroomlyne, en die kleinste moontlike getal quasi-ortogonale het, wat nie binne
lemrye geplaas mag word nie. Die numeriese stabiliteit van beide die Matriks Deurvloei
en die Stroomlyn Kromming Metode verbeter deur gebruik te maak van radiale vloeivermengingsmodelle, sonder om die akkuraatheid van voorspellings te benadeel. De Haller
se metode was oorkonserwatief waar dit gebruik is om die staak-lyn vir transsoniese vloei
toestande, maar meer nuttig in die subsoniese vloei gebied. Aungier se lemrymetode het
akkurate resultate gelewer vir alle kompressors getoets, behalwe die Rofanco. Die diffusie
faktor metode was oor die algemeen minder akuraat as Aungier se metode, maar meer akkuraat as de Haller se metode vir transsoniese toestande. Die stabiliteitsmetodes het almal ewe
swak gevaar. Dit stem ooreen met die bevindings van vorige navorsing, wat bewys het dat
hierdie metodes nie toepaslik is vir simulasies wat deurvloeimetodes gebruik nie. Aungier se
grenslaagmetode het ook baie swak gevaar. Waarskynlik is dit as gevolg van tekortkomings
in die grenslaagblokkasiemodel.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/18702 |
| Date | 03 1900 |
| Creators | Gill, Andrew |
| Contributors | Von Backstrom, T. W., Thiart, G. D., University Stellenbosch. 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 | English |
| Type | Thesis |
| Format | 113 p. : ill. |
| Rights | Stellenbosch University |
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