Aerodynamic design of an aspirated counter-rotating compressor

Abstract

A primary goal in compressor design for jet engines is the reduction of size and weight. This can be achieved by increasing the work output per stage, thereby reducing the required number of stages. In this thesis, the aerodynamic design of a high speed compressor that produces a pressure ratio of 9.1:1 in only two stages (rather than the typical six or seven) is presented. This is accomplished by employing blade aspiration in conjunction with rotor counter-rotation. Aspiration has been shown to make feasible significantly increased blade loading and counter-rotation provides a means of taking full advantage of this potential throughout a multistage compressor. The aspirated counter-rotating compressor was designed using a one-dimensional stage analysis program coupled with an axisymmetric throughflow code and a quasi-three- dimensional cascade code for blade design. The design of each stage focused on maximizing pressure ratio within diffusion factor and relative inlet Mach number (i.e. shock loss) constraints. The exit angle of the first stator was optimized to maximize the pressure ratio of the counter-rotating (second) rotor. The blade design code MISES allowed for each feature of the blade sections, including aspiration, to be precisely designed for the predicted conditions. To improve the process of designing blades with MISES, extensive analysis of previously designed high-speed aspirated blades was performed to identify the relationships between various blade features.