Abstract: Numerical simulations of three-dimensional unsteady flows were carried out to investigate
pressure fluctuations in the passages of a tubular pump system with S-shaped shaft extension in different
operating conditions by using the code CFX and comparing with experiments on scale model. Pressure
fluctuations at 21 locations of measurement in inlet and outlet passages were obtained and analyzed in time
and frequency domains for three typical working conditions of different flow rates. At the exit of inlet
passage, the pressure fluctuations show a frequency dominated by the rotation speed of impeller and the
blade numbers, and their amplitudes decrease gradually from wall to hub. And these amplitudes decrease
with flow coefficient in the range from 0.368 to 0.552. The amplitude of average pressure coefficient at the
inlet of elbow tube that is one part of outlet passage, is very close to that in middle part of outlet passage,
with a difference less than 0.0005. The fluctuating amplitudes in outlet passage are smaller than those at
the exit of inlet passage. Under influence of the circulation at guide vane outlet, the dominant frequencies
at different locations of measurements in a fixed working condition vary in a great extent, and those at a
fixed location vary slightly with flow rate.