Aerodynamic characteristic of limited micro-scale Taylor–Couette flow at hyper-rotate speed

To pursue improvements in the power-to-weight ratio, cost-effectiveness ratio, and reliability in the energy industry, rotating machinery has been developed with higher rotational speeds and smaller sizes, resulting in complex aerodynamic behavior of the rotational shearing flow between rotator and stator. This study reports experimental measurements of the aerodynamic characteristics of a limited micro-scale Taylor–Couette flow (TC flow) at hyper-rotational speeds for the first time. The maximum rotational speed and eccentricity ratio are 6.0 × 104 rpm and 0.8, respectively, and the minimum average clearance height is 100 μm. The static pressure of the shearing flow is measured using a high-response micro-manometer. A large eddy simulation has been employed to unveil flow fields of the gas film between the stator and the rotator. The results show that the micrometer-scale clearance height and end leakage due to limited length dominate the micro-scale Taylor–Couette flow. Decreasing the scale of the clearance height reduces the angular distance between the peak and bottom pressures compared to that observed in the TC flow with a large-scale clearance. Furthermore, ambient pressure cannot fully permeate into central section of the eccentric Taylor–Couette flow with a micrometer-scale clearance and end leakage, and the pressure upstream near the region the minimum size of clearance decreases along the axial end. Owing to the difference in the constraint degree at both ends along the axial direction, the peak value occurs near the region of Z/L = −0.32. The maximum pressure of the limited micro-scale Taylor–Couette flow increases with increasing rotational speed and eccentricity ratio, whereas it decreases with increasing clearance height. Within the scope of the parameters in this study, the maximum pressure is 0.025 MPa. Decreasing the size of gas film restrains the instability of the shearing flow, whereas increasing the rotational speed strengthens the turbulence. In this study, the shearing flow at the middle section (Z/L = 0) is in a nearly laminar state at δ < 0.012, whereas it is highly turbulent near the end of the clearance and in the ambient environment. The end leakage induces additional axial flow, which is conspicuous at a large eccentricity ratio. At hyper-rotational speeds, the micro-scale Taylor–Couette flow with end leakage exhibits distinctive patterns that have never been reported in classic Taylor–Couette flows with large clearances. This work of this study is significant because it can provide theoretical guidance and technical support for the design of actual dynamic pressure gas bearings and floating ring sealing flow.