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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. In this method pressurized air is injected 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 adjusted for providing an optimal flow pattern at the inlet. Its implementation on a compressor has shown an increase of efficiency at low mass flow rates. It has also improved flow pattern in impeller passages and decreased the blade loading near surge condition. It is also shown that the swirl generator system can be fed up from the compressor volute or diffuser, and thus widening the compressor performance map by retarding the surge margin.

Design and optimization of centrifugal compressors, based on main blades configuration of impeller have been vastly discussed in open literature, but less researches have addressed splitters. In this research, the impeller of a commercial turbocharger compressor is investigated. Here, profiles of main blades are not changed while the effect of changing the configuration of splitters is studied. An optimization study is performed to find the best configuration using genetic algorithm over a complete operating curve of the compressor. CFD codes with experimental support are used to predict the compressor performance. Quantumetric tests beside destructive analysis of two impellers are implemented for material identification and selection which is necessary for manufacturing. After taking into account structural considerations and approving the safety by numerical simulation, the new impeller is manufactured using 5 axis CNC machine. Non destructive tests are performed for identification of any structural defects. The new impeller is then mounted on a turbocharger shaft and tested experimentally in a wide range of operating conditions, which leads to a design having 2.3% improvement in efficiency. This is an important achievement in all applications of centrifugal compressors, especially in turbochargers.