Impact of Impeller Stagger Angles on Pressure Fluctuation for a Double-Suction Centrifugal Pump

Chinese Journal of Mechanical Engineering, Feb 2018

Pressure fluctuation may cause high amplitude of vibration of double-suction centrifugal pumps, but the impact of impeller stagger angles is still not well understood. In this paper, pressure fluctuation experiments are carried out for five impeller configurations with different stagger angles by using the same test rig system. Results show that the stagger angles exert negligible effects on the characteristics of head and efficiency. The distributions of pressure fluctuations are relatively uniform along the suction chamber wall, and the maximum pressure fluctuation amplitude is reached near the suction inlet tongue region. The pressure fluctuation characteristics are affected largely by impeller rotation, whose dominant frequencies include impeller rotation frequency and its harmonic frequencies, and half blade passage frequency. The stagger angle exerts a small effect on the pressure fluctuations in the suction chamber while a great effect on the pressure fluctuation in volute casing, especially on the aspect of decreasing the amplitude on blade passage frequency. Among the tested cases, the distribution of pressure fluctuations in the volute becomes more uniform than the other impeller configurations and the level of pressure fluctuation may be reduced by up to 50% when the impeller stagger angle is close to 24° or 36°. The impeller structure pattern needs to be taken into consideration during the design period, and the halfway staggered impeller is strongly recommended.

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Impact of Impeller Stagger Angles on Pressure Fluctuation for a Double-Suction Centrifugal Pump

Fu et al. Chin. J. Mech. Eng. Impact of Impeller Stagger Angles on Pressure Fluctuation for a Double-Suction Centrifugal Pump Da‑Chun Fu 0 3 FuJ‑un Wang 0 2 3 PeiJ‑ian Zhou 1 Ruo‑Fu Xiao 0 2 3 Zhi‑Feng Yao 0 2 3 0 College of Water Resources and Civil Engineering, China Agricultural University , Beijing 100083 , China 1 College of Mechanical Engineering, Zhejiang University of Technology , Hangzhou 310014 , China 2 Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System, China Agri‐ cultural University , Beijing 100083 , China 3 College of Water Resources and Civil Engineering , China Agricultural Uni‐ versity, Beijing 100083 , China Pressure fluctuation may cause high amplitude of vibration of double‑ suction centrifugal pumps, but the impact of impeller stagger angles is still not well understood. In this paper, pressure fluctuation experiments are carried out for five impeller configurations with different stagger angles by using the same test rig system. Results show that the stagger angles exert negligible effects on the characteristics of head and efficiency. The distributions of pressure fluctuations are relatively uniform along the suction chamber wall, and the maximum pressure fluctuation amplitude is reached near the suction inlet tongue region. The pressure fluctuation characteristics are affected largely by impeller rotation, whose dominant frequencies include impeller rotation frequency and its harmonic frequencies, and half blade passage frequency. The stagger angle exerts a small effect on the pressure fluctuations in the suction chamber while a great effect on the pressure fluctuation in volute casing, especially on the aspect of decreasing the amplitude on blade passage frequency. Among the tested cases, the distribution of pressure fluctuations in the volute becomes more uniform than the other impeller configurations and the level of pressure fluctuation may be reduced by up to 50% when the impeller stagger angle is close to 24° or 36°. The impeller structure pattern needs to be taken into consideration during the design period, and the halfway staggered impeller is strongly recommended. Double‑ suction centrifugal pump; Impeller stagger angle; Pressure fluctuation; Frequency spectra analysis 1 Introduction Double-suction centrifugal pumps are widely used in various fields, such as water diversion, farm irrigation, urban water supply, and process industry. The flow rate of a double-suction centrifugal pump is about twice as much as a single-suction centrifugal pump with the same diameter, and the axial force of the former pump is theoretically balanced [ 1 ]. In long-distance water diversion projects or high lift irrigations, double-suction centrifugal pumps are playing increasingly important roles, and the scales of which are becoming much larger. For instance, the impeller diameter of a double-suction centrifugal pump in Huinanzhuang pumping station in China reaches 1.75 m, and its single installation power is 7500 kW [ 2 ]. The internal flow in a double-suction centrifugal pump is extremely complex, especially under off-design operating conditions [ 3 ]. The 3D asymmetric flow pattern in the volute, the fluid dynamics of rotor–stator interaction, the secondary flow, and the cavitation phenomenon induce large pressure fluctuations [ 4, 5 ]. Periodic pressure fluctuation may force the impeller or volute to vibrate, and resonance may occur when the frequency of pressure fluctuation approaches the natural frequency of pump components. The energy of pressure fluctuations propagates in fluids at the speed of sound, which is harmful and unacceptable to the pump and environment. Furthermore, the lowest static pressure during fluctuation may lead to cavitations [ 6, 7 ]. Adverse operating conditions may be detected by observing the pressure fluctuations generated by a pump, which could provide evidence of inadequate suction conditions [ 8 ]. Several studies have characterized the pressure fluctuation of centrifugal pumps through experimental investigations, theoretical analysis, and numerical simulations [ 9, 10 ]. Chu et  al. [ 11, 12 ] tested a single centrifugal pump; built relationships among unsteady flow, pressure fluctuation, and noise; and inspected the interaction effect between the impeller and the volute. This study showed that the impeller–volute tongue interaction and the asymmetric outflow from the impeller are the two main sources of high-level pressure fluctuations. When the gap between the impeller and the volute tongue is less than 20% of the impeller radius, the amplitude of pressure fluctuation noticeably decreases as the gap increases. Stel et  al. [ 13 ] has recently presented a numerical investigation of fluid flow in a centrifugal impeller with a vaned diffuser. Significant levels of turbulence and blade-oriented effects are revealed at different flow rates. Pei et al. [ 14 ] found the optimizati (...truncated)


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Da-Chun Fu, Fu-Jun Wang, Pei-Jian Zhou, Ruo-Fu Xiao, Zhi-Feng Yao. Impact of Impeller Stagger Angles on Pressure Fluctuation for a Double-Suction Centrifugal Pump, Chinese Journal of Mechanical Engineering, 2018, pp. 10, Volume 31, Issue 1, DOI: 10.1186/s10033-018-0203-z