The deceleration of flowing fluids, or diffusion as it is widely known, is a process of primary importance, whereby some of the kinetic energy is converted into static pressure rise. Hence, in the case of subsonic flows, the area of a diffusing passage increases in the direction of the flow. Most commonly used diffuser configurations are: conical, annular, rectangular and radial. The rectangular shape is used widely in vaned diffuser systems for centrifugal compressors. In general, fluid motion in diffusing passages takes place against an adverse pressure gradient, and unless great care is taken in the design of these passages, the growth of boundary layer and its ultimate separation may seriously upset the performance of the diffuser system. From the point of view of the fundamental physics of fluid motion, the study of diffusing flows is indeed very interesting. Therefore, it has attracted the attention of many investigators, and a great deal of literature has been published on the performance of commonly used diffuser configurations. However, the available performance prediction techniques are either far from being reliable, or they are limited to specific geometry and fluid conditions. In the case of rectangular diffusers, there are other aspects which do not appear to have been fully investigated, for example: (i) Interdependence of the geometrical parameters, operating conditions and the performance of rectangular diffusers on the basis of a suitable theoretical model. (ii) Correlation between the principal dimensions of the compressor and the geometry of the diffuser channels. The aim of this research was to study these aspects. Full description of the aims is given in Chapter 1. Chapter 2 gives a comprehensive survey of the published literature and a statement of the justification of the aims. Chapters 3,4 and 5 describe the theoretical development for a parametric study, flow analysis and performance analysis respectively. The results of the theoretical studies and the comparisons between the predicted and experimental performance data are discussed in Chapter 6. The conclusions and suggestions for further work are given in Chapter 7. The performance prediction method and the correlation between the relevant dimensions of the compressor and the diffuser geometry are believed to be novel. It is submitted that they should make a significant contribution to the design methodology for centrifugal compressors in general, and for two-dimensional diffusers in particular.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:237125 |
| Date | January 1982 |
| Creators | Al-Modafar, M. M. H. |
| Publisher | University of Hertfordshire |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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