At present, micro air vehicles (MAVs) are being popularized in both military and civilian fields and are playing an increasingly important role. The flapping wing organism shows its advantages of high aerodynamic efficiency, quick action, and stable hover during flight. In this paper, by studying flapping wing insects, a new type of flapping wing aircraft was proposed, and a mechanical structure model and control system with variable rotating orbit radius were designed. When the rotating radius changed, the chip controlled the rotation of the variable rail motor and then changed the position of the displacement slider from the rotation center, which was finally represented by the change in the flapping amplitude of the flapping wing through the transmission mechanism. According to the designed mechanical structure, the coordinate system was established, and the expression was derived. At the same time, XFlow was used to carry out fluid simulation tests. Through the benchmark experiment, the fluid simulation test of the variable amplitude of the two wings, and the fluid simulation test of the amplitude of the variable single wing, the corresponding conclusions were obtained, and the rationality and feasibility of the variable-amplitude flapping wing aircraft model were verified. It provided data support for follow-up research and prototype production.

Partial surge is a type of instability inception in transonic compressors and occurs in the form of axisymmetric low-frequency disturbances localized in the hub region. Previous studies illustrate that the frequency of partial surge is set by the Helmholtz frequency of the entire system, which motivates to propose a hypothesis that the system response performs an important role in the formation of partial surge. For further verification, a series of experiments are conducted to explore the link between the propagating of the partial surge and the system feedback in this study. In the first case, an additional test point is set on the wall of the plenum to detect the system response. Combining the flow behaviors inside the plenum with the disturbances in the rotor tip and stator hub/tip regions, the effects of the system feedback on the occurrence of the continuous disturbances and the rotating stall cells are illustrated. In the second case, a screen is mounted at the compressor outlet to prevent positive feedback from the plenum. The experimental results demonstrate that in the absence of system feedback, it is the occurrence of spike-type stall inception that leads to the flow instability instead of that of partial surge. In addition, three flow phenomena in the second case are discussed, including the occurrence of the single pulse, the unstable process during the stall evolution and the switch of instability inception.