University research on problems relating to axial flow compressors is generally limited to low speeds (tip Mach numbers < 0.4). Experiments at higher speeds are conducted, but these experiments are generally conducted in large government or industry facilities. As the state of the industry for axial compressors advances (current tip Mach numbers > 1.0), the applicability and utility of low speed experimental results are becoming less clear.
Recent interest in the use of active flow control technologies in turbomachinery is putting further strain on the capabilities of universities to conduct relevant research. In order to test, refine, understand, and prove a particular flow control technology for axial compressors, it is necessary to conduct studies at high speeds (tip Mach numbers on the order of 1.0).
Currently, the only way to accomplish this is to develop the flow control technology in low speed machines and attempt to prove the technology at high speed in a government facility. Because of the high costs and risk associated with these types of experiments, few technologies ever reach this stage of testing, and even when they do, most studies are limited to simply determining whether or not the system works at high speeds. There is little chance for refining the technology and even less chance of studying the fundamental physics of the system in the compressible regime.
In an attempt to bridge the gap between low speed research and high speed proof-of-concept experiments, the Center for Flow Physics and Control (FlowPAC) at the Department of Aerospace and Mechanical Engineering of the University of Notre Dame has designed a transonic machine capable of fundamental physics experiments in the compressible operating regime. The machine will also be capable of proving flow control technologies at tip mach numbers close to the speeds of modern axial compressors. By developing flow control systems at this facility, the likelihood of successful tests in more capable government machines will be increased, and, just as importantly, the researchers will be able to obtain a depth of understanding of the operation of these technologies that has not been possible before.
The first stage operated in the ND TAC facility is ND Stage 01. The compressor has a design total pressure ratio of 1.55 at a corrected mass flow rate of 9.97 kg/s (22 lbm/s). The design corrected shaft speed is 14684 RPM and the design tip speed is 352 m/s (1153 ft/s). The stage has a tip diameter of 0.457 m (18 in) and an inlet hub to tip ratio of 0.75. The tip relative Mach number at design speed is 1.27. The blading consists of inlet guide vanes followed by a rotor and stator row. Efforts were made to ensure that the blade design is comparable to that found in the early HPC stages of the current generation of aero-gas turbine engines. Performance predictions for ND Stage 01 can be measured, as well as, pressure characteristics. To view the ND TAC core with ND Stage 01 installed, click here.
For more detailed information on the facility and ND Stage 01, see A Transonic Axial Compressor Facility for Fundamental Research and Flow Control Development by Cameron et al. 2006 .