This paper presents the experimental results of an advanced concept transonic compressor stage with a splittered rotor and a downstream variable geometry tandem stator. Two blisks make up the stator, with the first containing the upstream blades and the second the downstream. The downstream row is fixed while the upstream row is able to rotate about the machine axis. This was found to be a very simple and robust method of adjusting the geometry as it had only one moving part in contrast to the complex mechanisms required to move individual blades within a traditional row. Five different relative positions between the forward and aft blade rows were experimentally investigated in order to find the ideal stator positions for different operating conditions of an engine. It was found that the peak efficiency, maximum flow rate and maximum flow range of the entire stage could be adjusted by moving the single upstream stator blisk. This variable tandem stator configuration could thus eliminate the need for inlet guide vanes (IGV’s) with variable flaps in the first compressor stage, which are typically found in many military engines. This removal of a blade row could lead to lighter and less complex engine. The variable stator concept may also be applicable to the high pressure stages during startup where a high mass flow rate would reduce the need for bleed systems. Results over a wide speed range from subsonic to transonic are presented and the geometry is available upon request as a test case.

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