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Improving the performance of centrifugal compressors by flow recirculation
Author(s): Seyed Abolfazl Moussavi
Keywords: Centrifugal compressor, Flow injection, Surge, Performance map, Incidence loss
The impeller of a centrifugal compressor is traditionally designed using some formula for only one design point which makes it less efficient in all other situations. This is especially important for compressors not experiencing a constant working condition. To improve the performance at low mass flow rates and retard the surge, an innovative concept is introduced for a centrifugal compressor. The system injects pressurized air at the compressor inlet to improve the flow field. With better incidence angle, related losses at off design conditions are minimized and the surge is delayed. This system is designed, modeled and justified for providing an optimal flow pattern. Its implementation on a compressor shows increase of efficiency at low mass flow rates. It also improves flow pattern in impeller passages and decreases the blade loading near surge condition. It is also shown that the swirl generator system which can be fed up from the compressor volute or diffuser, widens the compressor performance map by retarding the surge margin.