Numerical investigation of the potential of multi-row optimization of an axial compressor stage with a tandem vane stator

In the published literature, there are a few examples of axial compressors designed with tandem vanes, aimed to increase the maximum loading of the machine. It appears that the advantages of employing tandem vanes are overruled by additional problems arising in real compressor applications. Phenomena such as the increase in endwall and secondary losses prevent tandem vanes from being widely employed in current commercial engine designs. In this work, the airfoil geometries of the IGV, rotor, and the shrouded tandem stator of a highly loaded axial compressor stage are improved in a combined optimization, using the potential of this configuration in a one-and-a-half-stage environment. The redesigned compressor stage shows performance improvements in the total pressure ratio of each vane and isentropic efficiency of the one-and-a-half-stage. The optimized stage is extended to the three-and-a-half-stage configuration of the machine, confirming and extending the benefits of the optimized geometries with an increase in stage work coefficient of 3% and in stage isentropic efficiency of up to 0.76%. Starting from these results, the authors widen the content of this work to provide a better understanding and a solid background in the design of axial compressor stages with tandem vanes, highlighting their potential benefits in multi-stage environments.