We present the design, construction and initial experimental validation of the Northwestern Polytechnical University Taylor–Couette (NPU-TC) apparatus, specifically developed to explore turbulent Taylor–Couette flows under conditions relevant to ultra-high-speed rotating machinery. The apparatus features an inner cylinder capable of rotating at speed of up to 10 000 rpm, corresponding to a Taylor number Ta = 6. 4 10⁸, with an exceptionally narrow annular gap of 2. 8 mm, yielding a radius ratio () of 0. 98. Axial-scanning particle image velocimetry is employed here for the first time in air-based TC flows at such extreme conditions, which enables detailed velocity measurements without intrusive disturbances. Our velocity measurements demonstrate the absence of large-scale coherent flow structures, indicating a transition into the ultimate turbulence regime characterised by very thin boundary layers and nearly uniform velocity distributions in the bulk region. The NPU–TC apparatus thus represents a significant advance in experimental capabilities, providing critical insights into turbulent flow behaviour in high-speed rotating machinery.
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