Design of a small pressure chamber to evaluate probe calibrations at varying Reynolds numbers

The Chair of Turbomachinery and Flight Propulsion (LTF) at the Technical University of Munich (TUM) operates a wind tunnel for probe calibration (Caljet). This paper describes the design and the validation process of a pressure chamber. The pressure chamber is used to calibrate probes for turbomachinery applications at comparable conditions to a 3.5-stages axial compressor test rig. This allows the study of Reynolds number and Mach number effects individually. The pressure chamber is designed as an additional component for the Caljet to enable probe calibration at higher mass flow densities and higher Reynolds numbers. Therefore, the original free stream jet is encased by this chamber, nevertheless the outlet of the calibration wind tunnel remains open to the environment. After a first pre-design study, numerical simulations are carried out to confirm expected flow conditions in the measurement area. Ansys Fluent is used for RANS simulations with air modeled as compressible gas. The numerical results are validated with experimental investigations that simultaneously provide a deeper understanding of the flow behavior. Therefore, a five-hole probe, a hot-wire probe, and a Fast Response Aerodynamic Probe are utilized. It is shown that the capability of the jet meets the expectations and can be used for the calibration of hot-wire probes at conditions comparable to a state-of-the-art 3.5-stages axial compressor.