A MODEL FOR NUMERICAL SIMULATION OF VARIABLE STATOR AXIAL FLOW COMPRESSORS

Axial flow compressors are usually found in gas turbines, both for aero and industrial applications due to their higher flow capacity, pressure ratio and efficiency when compared to the centrifugal counterpart. Due to the wide range of ambient conditions at which the gas turbines are required to work, compressor designers have to foresee its performance capability and possible points of malfunction. To explore all points of actual compressor operation it is required extensively and time-consuming tests, in addition to high costs. To cut time and costs, numerical simulations have been employed extensively, through simple to more complex mathematical models. Capability to predict the compressor map is required at the beginning, since is the map characteristics an indication of the success of the designed compressor. At design point compressor efficiency is optimized due to the alignment of flow with blade passage areas. At off-design point the flow misalignment at the various rows causes losses to increase sharply, therefore decreasing pressure ratio and efficiency. To bring the flow to alignment with the blade passages it is required to re-stagger the blades. To avoid mechanical complexities it is generally accepted to re-stagger only the stators. This work deals with a numerical approach to the simulation of an axial flow compressor equipped with variable stators. Improvement to the compressor performance is demonstrated with calculated compressor maps for different blade staggers, using a specially developed computer program to simulate virtually any axial flow compressor having variable stators.