Pressure recovery of axial flow turbine draft tube with inlet swirl

• Main Authors: Augusto, Gerardo L., Culaba, Alvin B., Gan Lim, Laurence A., Maglaya, Archie B., Piseth, Sok
• Format: text
• Published: Animo Repository 2015
• Subjects: Axial flow; Draft tubes; Mechanical Engineering
• Online Access: https://animorepository.dlsu.edu.ph/faculty_research/12014
• Institution: De La Salle University

This study presents the numerical and experimental investigations of flow behavior in an axial flow turbine draft tube model with cross-section changing from annular to rectangular. Forced vortex type of tangential velocity was introduced upstream of diffuser inlet with Reynolds number of 40,000 and different rotational rates of 0.0, 0.168, 0.336 and 0.504. In this study, air was used as a working substance instead of water. I-type hot-wire probe and pressure transducers were used to determine the velocity components and mean wall pressure coefficients in each test cross-section, respectively. To further verify the experimental results, ANSYS Fluent software was also used to obtain the velocity profiles in each test cross-section of turbine draft tube. Numerical results were compared with experimental data and have found some degree of similarities with dimensionless velocity profiles at diffuser inlet and momentum flux ratio. Improvement of diffuser performance at a moderate inlet swirl was achieved as compared with that obtained from non-swirling inlet flow. Further increase of inlet swirl was found to deteriorate the pressure recovery due to the onset of vortex breakdown.