In order to explore the characteristics of pressure pulsation signals and energy distribution of water flow at the guide vane considering impeller–guide vane interaction. The numerical simulation of the vertical axial flow pump device's steady and unsteady three-dimensional flow fields was carried out. The Hilbert–Huang method was used to conduct empirical mode decomposition decomposition and Hilbert spectrum analysis of pressure pulsation signal at each monitoring point in the inlet and outlet regions of the guide vane. The results show: Under the condition of 0.3 Qbep, the internal pressure of the guide vane is obviously affected by the impeller, and there are large block-shaped vortex structures in the guide vane. Under the operating conditions of 1.0 Qbep and 1.2 Qbep, the size of the pressure area in the guide vane is basically not affected by the impeller, and the vortex structures in the guide vane are concentrated near the outlet of the guide vanes, and there are long strip-shaped vortex structures at the edge of the guide vane. The size and number of vortex structures decrease with the increase in flow rate. The pressure pulsation signal at the inlet of the guide vane is affected by the rotation of the impeller and exhibits good periodicity, with the main frequency centered around 146 Hz, and the energy ratio of the main frequency is up to 97.7%. There are low-frequency signals below 100 Hz and high-frequency signals fluctuating around 146 Hz in all three flow conditions. When the flow rate increases, the fluctuation amplitude of the high-frequency signal increases. The flow rate has a significant impact on the water flow at the outlet of the guide vane. At 0.3 Qbep, its frequency is distributed in the range of 0–500 Hz, mainly concentrated in the area below 400 Hz. At 1.0 Qbep, the frequency of pressure pulsation is distributed below 250 Hz after the guiding function of the guide vane. At 1.2 Qbep, the water flow is mainly controlled by the rotation of the impeller, and after the energy recovery of the guide vane, its main frequency is still concentrated around 150 Hz, which is 337.2% and 268.5% of 0.3 Qbep and 1.0 Qbep. Under the working condition of 0.3 Qbep, the proportion of intrinsic mode function energy corresponding to the dominant frequency at the center of the guide vane inlet is as high as 95.9%, and the proportion of intrinsic mode function energy corresponding to the dominant frequency at the shroud side and hub side of the guide vane is rather low. If the flow rate rises from 0.3 Qbep to 1.2 Qbep, the proportion of intrinsic mode function energy increases by more than 42%. Under the working conditions of 0.3 Qbep and 1.0 Qbep, the main frequency of pressure pulsation signal of water flow at the guide vane outlet is less affected by the impeller and the corresponding energy proportion is low. Under the working condition of 1.2 Qbep, the main frequency of pressure pulsation signal is 4 times the rotational frequency and the corresponding energy proportion is higher than 60%.
The unsteady three‐dimensional numerical simulation calculation of the vertical axial flow pump device is performed based on CFD to examine the pressure pulsation and energy distribution features of the water flow within the siphon outlet conduit (SOC) under the hydraulic coupling of the pump and the flow conduit. The pressure pulsation signals (PPS) of monitoring points are decomposed using the Hilbert–Huang approach via empirical mode decomposition (EMD) and Hilbert spectrum analysis. The results show that the PPS of monitoring points of the SOC has no obvious periodicity. The low‐frequency range below 20 Hz serves as the primary frequency, and the energy ratio of the high‐frequency signal above 700 Hz is less than 1%. Under the condition of a small flow rate 0.3Qbep, there is obvious high‐frequency pulsation above 500 Hz at the inlet of the upstream section of the SOC, and there are periodic components distributed around 200 Hz. The energy of the pressure pulsation is primarily focused in the low‐frequency range below 40 Hz at the SOC outlet section. The PPS at the top and bottom monitoring points of the hump section are consistent, and the pressure pulsation energy (PPE) is mainly concentrated in the low frequency below 40 Hz. In both the big flow condition (1.2Qbep) and the optimal flow condition (1.0Qbep), the PPE of the monitoring points at the top of the hump section is distributed in the middle and low‐frequency band below 40 Hz, and the energy of monitoring points at the bottom of the hump section is concentrated in the low‐frequency band below 20 Hz, accounting for more than 70%. When the flow rate increases from 0.3Qbep to 1.2Qbep, the peak value of the pressure pulsation coefficient at the main frequency of each monitoring point at the top of the hump section changes little, and the peak value of the pressure pulsation coefficient at the main frequency of each monitoring point at the bottom increases first and then decreases. From the upstream section to the hump section of the SOC, the average frequency of each intrinsic mode function (IMF) of the PPS under different flow conditions shows an overall increasing trend. From the hump section of the SOC to its outlet, the average frequency of each IMF of the PPS decreases under the conditions of 1.0Qbep and 1.2Qbep, and there is no obvious change under the condition of 0.3Qbep.
In order to clarify the non-constant flow characteristics of the impeller and bulb body of the submersible tubular electric pump device, the entire flow rate conduit of the pump device is numerically calculated using the numerical simulation method, focusing on the analysis of the non-constant flow field characteristics of the guide vane body and bulb body and the time–frequency variation law of the pressure pulsation, and the results of the physical model testing confirm the validity of the numerical simulation. The findings demonstrate that the impeller of a submersible tubular electric pump is mostly responsible for the impeller’s inlet pressure pulsation, and the number of impeller blades to the number of peaks and valleys is consistent. Under the high flow rate condition of 1.2 Qd, the pressure fluctuation in the impeller inlet, between the impeller and the guide vane is small, and the main frequency is located at three times the rotational frequency, and the pressure pulsation at the outlet of the guide vane body has no obvious pattern and small amplitude. As the flow rate increases, the peak value of pressure pulsation at each monitoring point in the characteristic section of the pump device gradually decreases. The pressure pulsation peak value varies widely, ranging from 0.058 to 0.15, at each monitoring location of the impeller inlet. The peak value of pressure pulsation at each monitoring point of the impeller outlet fluctuates less due to the change of flow rate. The size and scale of the omega vortex structure in the guide vane body at different moments of the same cycle is small, and the number of vortex structures from the guide vane body inlet to the outlet direction shows a gradual increase in the trend; with a rise in flow rate, there is a tendency for the velocity and deflection angle of the guide vane body outlet and bulb body outlet surface to decrease.
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