Abstract
The tip clearance has an important effect on the performance of an engine compressor. While the impact of tip clearance on a concentric compressor has been widely explored in previous research, the flow field distribution of an eccentric compressor has only been minimally explored. Both the steady and unsteady computational fluid dynamics (CFD) methods have been widely used in the studies of concentric axial-compressors, and they have similar simulation results in terms of flow field. However, they have been rarely applied to axial-compressors with non-uniform tip clearance to investigate their flow field. In this paper, ANSYS CFX is used as CFD software, and both steady and unsteady CFD methods are applied to study a single rotor of ROTOR67 to investigate the compressor characteristic line and flow field under different eccentricity conditions. The results show that non-uniform tip clearance creates a non-uniform flow field at the inlet and tip regions over the whole operating range. The circumferential position where the flow coefficient and the axial velocity are the smallest occurs at a position close to the maximum tip clearance and is located on the side deviating toward the direction of rotation of the rotor. Compared with steady CFD, unsteady CFD has better predictive capability for the flow field distribution in axial compressors with non-uniform tip clearance.
Highlights
A lot of experiments and numerical simulation show that tip clearance plays an important role [1,2,3] in the performance and stability of axial compressors
The non-uniform tip clearance can be described by ε = ε(θ), where ε is the tip clearance and θ is the circumferential coordinate; the second type is the dynamic non-uniform tip clearance, mainly due to the difference in blade height or the rotor swirling motion caused by Alford force and vibration force, as shown in Figure 2.The non-uniform blade height and swirling
The multi-stage axial flow compressor is essentially an unsteady flow, but in engineering, the characteristic line is often calculated by a steady computational fluid dynamics (CFD) method
Summary
A lot of experiments and numerical simulation show that tip clearance plays an important role [1,2,3] in the performance and stability of axial compressors. A large number of published literature studies are based on axial compressors with uniform tip clearance, which may not fully reveal the true physical laws. Non-uniform tip clearance is inevitable in the production, processing, assembly and long-term use of axial flow compressors. The common forms of non-uniform tip clearance can be divided into two categories [4]. The non-uniform tip clearance can be described by ε = ε(θ), where ε is the tip clearance and θ is the circumferential coordinate; the second type is the dynamic non-uniform tip clearance, mainly due to the difference in blade height or the rotor swirling motion caused by Alford force and vibration force, as shown in Figure 2.The non-uniform blade height and swirling
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