Numeric Investigation Of Using Endwall Fences In Annual Cascade Of Transonic Compressor

For affect crosswise and spanwise flow directly, fence technique achieve great success in controlling secondary flow. In order to enhance the reliability, validity and universality of fence technique application, it is necessary to investigate its mechanism, and then to develop new methods for controlling secondary flow.In this paper, a detailed numerical simulation has been carried out for the transonic compressor cascade composed of CDA (controlled diffusion airfoils) straight blades equipped with fences on the endwall at zero incidence. For fence itself, there are several different profile parameters, such as length, height, pitchwise location, spanwise location for fence on the endwall. By means of the analysis, the optimum length, height, thickness, pitchwise or spanwise location of the fence are obtained for controlling secondary flow. In addition, demonstrate the accuracy of the numerical method and calculative results by comparing calculative results with some experimental data.In subsonic cascade, the fence which is equipped on different pitchwise location and with different height decreases secondary flow differently. The fence prevents the crosswise flow and the pressure side branch of the horseshoe vortex from moving towards the suction surface near the endwall of the cascade. With endwall fence, the passage vortex involves two vortices, P₁ and P₂. P₁ forms between the pressure surface and the fence and P₂ forms between the fence and the suction surface, these two vortices are much weaker than the passage vortex in the usual cascade. Numerical results show that the fences, with 2mm height and the length of 75 percent axial chord, are most effective when they are located 20 percent of pitch far from the pressure surface of the blade.Mach number increased imports, the horizontal movement of more strong, Cascade flow becomes more complex, more serious separation phenomenon. Numerical results show that the fences, 5mm height are most effective, with the increase of import Mach number, the best heigh is also increasing. The length of 75 percent axial chord, when they are located 20 percent of pitch far from the pressure surface of the blade, are still most effective.In the flow of the installation of different length, different combinations of axial location of the fences, which q0.5 + h0.5 programme for the best combination. That is, inλ= 0.2 installed near the leading edge with a length of 0.5 in the long arc, and inλ= 0.8 installed the near trailing edge with a length of 0.5 in the long arc, is the best combination.