Prof. Dr. Hesham Mohamed El-Batsh :: Publications:

The flow in turbomachines is three-dimensional and complex due to the existence of flow vortices which are generated by the deflection of the flow through the blade channels. If the tip clearance exists, the flow field becomes more complex due to tip leakage. In this study the flow field was investigated experimentally and numerically. The experimental study was carried out by using a calibrated five-hole probe. The measurements were performed at different planes through the blade axial chord. These planes were placed upstream of the blades, through the blade channels and downstream of the blades. The measurements were performed for different tip clearance gaps. The three-dimensional flow was also obtained by solving Reynolds Averaged Navier Stokes equations. The eddy viscosity was calculated by using Shear Stress Transport (SST) k-ω turbulence model. It was found that the leakage flow rolls up due to the pressure difference between the blade pressure surface and the blade suction surface and interacts with the passage vortex forming the tip leakage vortex. The numerical technique used here could predict the shape of the passage vortex and the tip leakage vortex with good agreement with the experimental measurement. The experimentally measured and the numerically calculated losses were used to examine previous published correlations of tip leakage loss. Recommendations are given for the most accurate tip leakage loss correlations.