Numerical simulation and experimental study of energy dissipation in a bidirectional axial extended tubular pump with different blade angles

Bidirectional axial extended tubular pumps (BAETPs) are used in low-head pumping stations. This work used both experiments and numerical simulation to investigate the energy dissipation of BAETPs with various blade angles (the blade angle significantly impacts energy loss). Results show that the impeller produces the highest entropy compared with the other pump components. At blade angles of 0°, −2°, and −4°, the unit produces an entropy of 262, 197, and 144 W/K. As the blade angle increases, the ratio of entropy production in the impeller to the total entropy production of the pump steadily rises, the same ratio for the guide vane remains constant at 25%, and the ratio for the S-shaped elbow decreases sharply. Turbulent entropy production rate in the impeller is primarily concentrated in the blade inlet and outlet. Wall entropy production rate in the impeller is focused on the inlet edge of the impeller blade and tip clearance. High entropy production rate (HEPR) occurs at the blade tail due to the rotation of impeller and tip clearance leakage at the area between the impeller and guide vane. Inside the guide vane, the highest entropy production occurs at the guide vane outlet. The HEPR zone on the suction surface of the guide vane is curved and shifts gradually toward the center of the guide vane passage.