The Design For Variable Camber Inlet Guide Vanes On CDFS And Research For Enhancing Compressor Stability By Tip Injection

As a key part of the core driven fan stage(CDFS), vari able camber inlet guide vanes must be steadily operated at two different operation modes: single bypass mode and double bypass mode. Considering the design indicators of CDFS at two different operation modes, the designing method was presented to devise the variable camber inlet guide vanes with the wide range of flow turning angles under the requirement of low loss. As a result, the designed variable camber inlet guide vanes design which were in good agreement with the design indicators were validated by the cascade experiment. In addition, the effect of the bowed stator vane on the stability enhancement of tip injection was further explored by performing an experiment on a two-stage low-speed axial compressor, which is conducive to the hybrid research of stability enhancement of tip injection and three-dimensional blade design in the future.Firstly, to design the fundamental blade profiles for the variable camber inlet guide vanes, a corresponding modeling program of the two-dimensional blade profile was presented to regulate easily the maximum deflection position, the maximum thickness and its position, and camber angle, etc. Then, the relationship between the geometric parameters and the aerodynamic performances of cascade are analyzed combining the business computing software. The results show that the deviation angle and minimal loss is related to the camber angle for the same maximum deflection position and they have more intensely enhanced with the increasing of maximum deflection positio n under a large camber angle. Moreover, the different flow turning angles are corresponding to the different optimal fundamental blade profiles.Secondly, on the basis of the fundamental blade profile design, the influences of the slotted shapes and design points on the performance of the variable camber inlet guide vanes were studied by the numerical simulation. The results show that the use of Coanda molded surface in the design of slotted shape can effectively enhance the wall attachment performance of the leakage flow and suppress the development of the boundary layer behind the slotted position. Moreover, the Coanda molded surface can make more a half of the loss to be reduce d than the conventional circle shape at the large flow turning angles. Additionally, the selection of the design point has a significant effect on the performance of the variable camber inlet guide vane when the outlet flow angles of variable camber inlet guide vane are varied in a wide range. Furthermore, our designed variable cambe r inlet guide vanes are in good agreement with the design indicators of CDFS at the single and double bypass modes validated by the cascade experiment and three-dimensional simulation of CDFS.Finally, an experiment on a two-stage low-speed axial compressor was carried out to explore the stability enhancement of tip injection and the compressor internal flow field for both bowed and straight stator blades. The experimental results show that the stability enhancement of tip injection for the compressor with bowed blades is more significant than that of the compressor with straight stator blades. The reason of causing this phenomenon is that the tip injection can improve the quality of flow field in the tip region and the modal wave concentrates mainly on the blade tip at the process of compressor stall when the straight stator blades on the first stage are replaced by the bowed blades. The increase of stable margin is up to 10.1% at 0.03% of relative jet flux.