Pressure fluctuation characteristics in the pressurization unit of a multiphase pump

The tip clearance induces the tip leakage vortex(TLV),which has a great impact on the pressure fluctuation characteristics of the multiphase pump.To investigate the effect of the tip clearance on the pressure fluctuations,based on the Reynolds time-averaged Navier-Stokes equation and the shear stress transfer(SST)k-ωturbulence model,the three-dimensional turbulent flow in the pump is numerically simulated for different tip clearances in the water and gas-liquid two-phase cases by using the ANSYS CFX software and the results are verified with experimental data.It is shown the greater pressure fluctuation intensity corresponds with the TLV both in the water and gas-liquid two-phase cases.In the meantime,the location of the maximum pressure fluctuation intensity is related to the tip clearance size.In addition,for different tip clearances,the pressure fluctuation intensity with the rotor and stator interaction(RSI)is relatively larger.The difference is that when R_(tc)=1.5 mm,the pressure fluctuation intensity near the impeller middle point is also relatively larger.On the whole,the pressure fluctuation intensity in the gas-liquid two-phase case is larger than that in the water case.Furthermore,the gas causes the frequency of the high-amplitude pressure fluctuation in the impeller and the diffuser to be shifted from 7 f_(n)(f_(n) denotes impeller rotational frequency)and 3 f_(n) to the low-frequency region,respectively.The pressure fluctuations at the blade-passing frequency(BPF)and the multiple BPFs gradually disappear.Meanwhile,the amplitude at the dominant frequency in the gas-liquid two-phase case is at least one order of magnitude smaller than that in the water case,and the peak-to-peak value of the pressure fluctuation is also much smaller.

Investigation on subsurface vortices within a closed pump intake under different pressure conditions

An experimental study to investigate various features of subsurface vortices and their evolutions inside a closed pump intake under different pressure conditions at free surface,and to analyze the influence of a pipe bell with different mean axial velocities at the same water level on flow patterns is presented.For all cases,three different flow regimes are closely observed:various side-wall attached,back-wall attached and submerged vortices structures,and their evolutions are subject to the free-surface pressure for a critical flow rate,the number and strength of all these vortex rise as the absolute value of the pressure increases for a higher flow rate,for a lower flow rate,whether the side-wall vortices occur or not is related closely to the pressure magnitude,and there are no vortices for lower absolute pressure values,the number and the strength of the side-wall vortices increase as the absolute pressure values increase.Besides,based on statistical analyses,the side-wall vortex probability on the right side along the stream-wise direction is much higher than that on the opposite side for all operation cases,particularly single vortex probability,and the back-wall vortex probabilities are quite higher with values of more than 90%,meanwhile,the multi-vortices probability is much higher than that of the single-vortex.The captured vortices have been qualitatively classified into different“vortex zones”:no vortex zones and vortex zones including transition,single-and multi-vortex.The Reynolds number and the absolute value pressure are the most important parameters which influence the existence and the number of these vortices,and the increase of the two parameters reduces the no vortex transition zone and causes bigger difference in the back-wall and side-wall vortex zones.