Flow separation is a major parameter affecting the compressor performance. It reduces the compressor efficiency, limits static pressure rise capability and contributes to instability in compressors. In applied research, there is a lack of understanding of the nature and mechanism of the three-dimensional (3-D) flow separation in the axial compressor especially on the juncture of the endwall and blade corner region. In the present study, the 3-D flow field in an axial compressor cascade has been studied experimentally as well as numerically.
For the experimental study part, a linear compressor cascade has been installed in an open loop wind tunnel. The experimental data was acquired for a Reynolds number Rec = 2.98 × 105 based on the blade chord and the inlet flow conditions. The total pressure loss progress through the blade passage has been measured by using calibrated five and seven-hole pressure probes connected to ATX sensor module data acquisition system. The static pressure distribution on the endwall has been measured employing static pressure taps connected to digital micromanometers. To investigate the loss mechanism through the cascade, the total pressure loss coefficient has been calculated from the measured data.
The computational fluid dynamics (CFD) study of the flow field was performed to gain a better understanding of the flow features. Two turbulence models, Spalart-Allmaras (S-A) and shear stress transport SST (k-ω) were used. From both parts of study, the flow field development and total pressure loss progress through the cascade have been investigated and compared. Moreover, the received data demonstrated a good agreement between the experimental and computational results. The predicted flow streamlines by numerical calculations showed regions characterized by flow separation and recirculation zones that could be used to enhance the understanding of the loss mechanism in compressor cascades. All measurements taken by 5-hole and 7-hole pressure probes have been analyzed and compared. It was found that their readings were almost the same and there are no excellences for using 7-hole probe. Furthermore S-A turbulence model calculations showed more consistencies with experimental results than SST (k-ω) model. |
