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Active suppression of aerodynamic instabilities in centrifugal compressors
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Fleeter, Sanfor |
| Organization | The National Aeronautics and Space Administration (NASA) |
| Copyright Year | 1994 |
| Abstract | The operating range of a compressor is bounded by the surge and choke lines on a performance map. The barrier posed by the surge line is of particular interest due to its proximity to the maximum efficiency points of the compressor. Namely, the surge line separates the regions of stable and unstable compressor operation. As a result, adequate surge margin from the operating line must be provided, resulting in the machine not operating at maximum efficiency. The term ''surge line'' on the performance map is somewhat misleading because surge is only one of the possible unsteady flow phenomena that occur when the surge line is reached. In general, two flow instability modes exist; rotating stall and surge. Rotating stall is an instability local to the compressor. It is characterized by a circumferential nonuniform flow deficit, with one or more stall cells propagating around the compressor circumference at a fraction of impeller speed, typically from 10 to 30. In fully developed rotating stall, the overall flow through the compressor is constant in time, with the stall cells redistributing the flow around the annulus. The formation of these rotating stall cells is surmized to result from an axisymmetric flow instability, with small circumferential nonuniformities growing into finite amplitude disturbances. In centrifugal machines, rotating stall is often subdivided into impeller stall and diffuser stall to differentiate where the effect of the distorted flow is strongest. In contrast to rotating stall, surge is a global instability which involves an oscillation of the overall flow. Mild surge refers to a low amplitude, global oscillation of the mass flow through the compression system without any flow reversal occurring. Mild surge often precedes deep surge, which takes the form of a more violent oscillation, with the mass flow through the system reversing over a portion of the surge cycle. Surge is a phenomena of the entire compression system, consisting of the compressor and the system into which it discharges. The frequencies of surge are set by the system geometry rather than by that of the individual components. The frequencies are therefore independent of impeller speed and tend to be much lower than those of rotating stall. |
| File Size | 355195 |
| File Format | |
| Alternate Webpage(s) | http://www.archive.org/details/nasa_techdoc_19970040808 |
| Archival Resource Key | ark:/13960/t3611x208 |
| Language | English |
| Publisher Date | 1994-12-01 |
| Publisher Institution | Glenn Research Center |
| Access Restriction | Open |
| Subject Keyword | Distributed Processing Learning Research Facilities Internets World Wide Web Education Video Tapes Cd-rom Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
