Numerical Study Of The Effect With Straight And Bowed Stator In Different Axial Gaps

The development of higher efficiency and larger thrust-weight ratio of aeroengine has put a further demand on the aerodynamic performance of compressor component. The method improving the compressor's aeroperformance by changes of geometrical shape among flow passage will be promising. Based on this understanding, the method of 3-D numerical simulation is adopted to investigate the two stages of a low speed compressor in the dissertation, and it was by means of changing the type of stators(straight blade and positive dihedral blade) and varying the axial gap between rotor and stator to realize the changes of geometrical shape among flow passage through the research.Firstly,the performance of the two original axial gap compressors which used straight stator and the positive dihedral stator was investigated. The result shows that the shaft work of the compressor with positive dihedral stator is less than the compressor with straight stator, and the reducing of the shaft work is a positive element for the efficiency rising, and it also proved that positive dihedral stator weakened the potential flow interference. The efficiency of the compressor with positive dihedral stator is all higher than that with straight stator at all working conditions in different degree, and the positive dihedral stator also increases the stall margin of the compressor. However, comparing to the straight stator the positive dihedral stator reduced the turning angel of the air flow and the mass flow rate of the compressor. The positive dihedral stator changed the static pressure distribution on the surface of blade, and it establishs the C-type pressure distribution on the suction surface, which means that the static pressure near end wall is higher than that far from the end wall in radial direction. Thus, the boundary layer fluid would move to middle region of blade under the psid, which could restrain the boundary layer fluid's accumulation on the blade surface near end wall effectively.This dissertation establishes two methods which also be investigated with straight stator and positive dihedral stator to reduce the axial gap based on original axial gap. The result shows that reducing the axial gap increased the torque, and that proved that small axial gap strengthen the potential flow interference. Smaller axial gap is helpful to improve the aerodynamic performance of compressor. however, it will worsen the aerodynamic performance of a compressor if the axial gap is too small, such as it reduce a compressor's stall margin. This also proved that there is a certain axial gap with which a compressor can achieve optimal aerodynamic performance. Further, the performance of the compresspor works at the near stall condition is the most sensitive to axial gap varying, the maximum flow rate condition is the least one, and the design condition take the middle place. Comparing to the compressor with positive dihedral stator, the compressor with straight stator is sensitive to axial gap varying.