Mechanical design of an experimental aspirated compressor

Abstract

In this thesis, the design and construction of a low speed, aspirated fan stage is described. The design intent of this stage is to increase the work per blade row by control of the boundary layers within the flowpath. The low speed fan stage is designed to produce a pressure ratio of 1.5 at a tip speed of 700 ft/s. Any boundary layer that could limit the performance of the stage is controlled by suction at the location just upstream of the strong deceleration of the free stream. The blade boundary layer was the primary focus of the aspiration scheme, but the endwall boundary layers are also treated. Implementation and design strategies for endwall and blade boundary layer removal are presented along with a description of the stage assembly and construction. Suction passages milled within the suction surface of the blades in conjunction with cover plates provide a suction flowpath for blade boundary layer fluid removal through a tip shroud on the rotor. Endwall boundary layer removal also plays a large part in the design of the complete aspirated stage. Slots are positioned just upstream of both the rotor and stator tip shrouds for endwall boundary layer removal. The hub endwall boundary layer is also suctioned immediately upstream of the stator.