关键词: S弯进气道, 离心压气机, 部件耦合, 流动畸变, 特性修正

Abstract: The internal flow within an S-shaped inlet is primarily governed by the geometric contour. Under the dual-bend configuration, a distorted exit flow field characterized by high-speed flow on the upper side, low-speed flow on the lower side, and counter-rotating vortex structures is formed, which exhibits strong coupling effects with downstream components. In this paper, standalone and coupled simulations are conducted for a subsonic S-shaped inlet and a centrifugal compressor. By comparing the performance parameters and flow field structures under different operating conditions, it is found that the suction effect of the downstream compressor and the geometric interference of the guide cone lead to a disruption in the symmetry of the total pressure distribution at the interface, although the calculated total pressure recovery coefficient of the inlet shows a slight increase. Upstream inlet distortion generally degrades compressor performance. At the design rotational speed, the blocked mass flow rate decreases under coupled conditions, while the isentropic efficiency and total pressure ratio at the peak efficiency point decrease, and the mass flow rate at the near-stall point increases, resulting in a reduced stable operating margin. The distorted flow field affects the inlet pre-swirl and velocity distribution, thereby inducing flow separation within the compressor flow passages. This is the main reason for the reduction in compressor efficiency, pressure ratio, and stable operating range. Based on the coupling mechanism between the two components and the observed performance trends, a method is proposed to decompose the swirling vortex flow field under the assumption of parallel compressors. By weighting the characteristics of sub-compressors, a correction to the overall compressor characteristics is achieved. The effectiveness of this method is validated by comparing the predicted results with actual full-annulus distortion calculation data at 80% and 100% rotational speeds.

Key words: S-shaped intake, centrifugal compressor, component coupling, flow distortion, characteristic modification