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)