S弯进气道内部流动受几何型面主导，在双弯折结构下形成具有上侧高速、下侧低速分层特征及对涡结构的出口畸变流场，与下游部件存在较强的耦合效应。本文针对亚声速S弯进气道与离心压气机开展部件独立和耦合仿真，对比分析不同工况下的性能参数与流场结构发现，下游压气机的抽吸效应与导流锥的几何干涉，会导致交界面处总压分布对称性被破坏，但进气道总压恢复系数计算略有提升；上游进气畸变会导致压气机性能普遍恶化，在设计转速下，耦合工况的阻塞流量下降，最高效率点等熵效率与总压比降低，且近失速点流量增大，稳定工作裕度减小。畸变流场影响进口预旋、流速分布，进而造成压气机流道内的流动分离，是其致压气机效率、压比下降，稳定工作范围缩小的主要原因。结合两部件耦合机制和性能影响规律，提出了基于平行压气机假设分解旋流对涡流场，以子压气机特性加权方式实现压气机特性修正，并通过80%转速下与100%转速下真实全周畸变计算数据与拟合得到的数据进行对比，验证了该方法的有效性。
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.
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