Tubular Pump Research Articles

Vibration Prediction and Evaluation System of the Pumping Station Based on ARIMA–ANFIS–WOA Hybrid Model and D-S Evidence Theory

Research on the vibration response prediction and safety early warning is of great significance to the operation and management of pumping station engineering. In the current research, a hybrid prediction method was proposed to predict vibration responses of the pumping station based on a single model of autoregressive integrated moving average (ARIMA), a combined model of the adaptive network-based fuzzy inference system (ANFIS) and whale optimization algorithm (WOA). The performance of the developed models was studied based on the effective stress vibration data of the blades in a shaft tubular pumping station. Then, the D-S evidence theory was adopted to perform safety early warning of the operation state by integrating the displacement, velocity, acceleration and stress indicators of the vibration responses of the pumping station. The research results show that the proposed prediction model ARIMA–ANFIS–WOA exhibited better accuracy in obtaining both linear and nonlinear characteristics of vibration data than the single prediction model and hybrid model with different optimization algorithms. The D-S evidence fusion results quantitatively demonstrate the safe operation state of the pumping station. This research could provide a scientific basis for the real-time analysis and processing of data in pumping station operation and maintenance systems.

Study of Energy Loss Characteristics of a Shaft Tubular Pump Device Based on the Entropy Production Method.

The unstable flow of a shaft tubular pump device (STPD) leads to energy loss, thereby reducing its efficiency. The aim of this study is to investigate the distribution pattern of energy loss in STPDs. This paper reveals that the two components with the highest proportion of energy loss are the impeller and the outlet passage. Furthermore, turbulent entropy production is the primary cause of energy loss. Due to the wall effect, the energy loss in the impeller mainly occurs near the hub and shroud. Additionally, the presence of a tip leakage vortex near the shroud further contributes to the energy loss in the region near the shroud. This results in the energy loss proportion exceeding 40% in the region with a volume fraction of 14% near the shroud. In the outlet passage, the energy loss mainly occurs in the front region, with a volume fraction of 30%, and the energy loss in this part accounts for more than 65%. Finally, this study reveals the locations of the vortex in the STPD under different flow-rate conditions, and when the distribution of energy loss is visualized, it is found that the energy loss occurs high in the vortex regions.

Leakage Flow Characteristics in Blade Tip of Shaft Tubular Pump

The shaft tubular pump device is widely used in various water diversion projects because of its ultra-low head and large flow characteristics. Due to the tip clearance between the blade and the shroud, it is easy to cause hydraulic mechanical performance changes, induced vibration, and noise, which seriously affects the safe and stable operation of the pump. Steady and unsteady three-dimensional flow field numerical simulations of a shaft tubular pump device were carried out using computational fluid dynamics to investigate the impeller flow properties of the device under various flow conditions, including the tip clearance leakage flow (TCLF) and change rule of pressure pulsation. The TCLF, vortex morphology evolution, and pressure pulsation properties of the impeller tip clearance were analyzed. The results show that with an increase in the flow rate, the influence of the tip clearance size on the tip clearance flow decreases, the TCLF decreases, and the axial velocity of the water flow at the tip clearance increases. When the flow rate increases, the swirling strength of the tip leakage vortex decreases, and the distance between the tip leakage vortex and the suction surface of the blade increases. With the increase in flow rate, the pressure pulsation amplitude at the tip clearance increases first and then decreases. The focus of this study is to analyze the variation of tip clearance flow field and pressure pulsation under multiple working conditions, aiming to provide some help for improving the performance of the pump device and ensuring its safe operation.

Pressure polarization oscillation in large-scale bulb tubular pump

Hydraulic consistency between a prototype pump and its hydraulic model is generally considered to be satisfied, that is, the energy performance and the flow structures conform to the similarity law. However, such hydraulic consistency may not always exist in actual engineering projects. Head change and vibration enhancement in large-scale bulb tubular pumps are exhibited, but the reason for this inconsistency is still unclear. In this article, a case study was performed for the South-to-North Water Diversion Project in China, and the pressure characteristics in the impeller were explored under the optimal condition. An interesting new phenomenon, pressure polarization oscillation, is found. Its most important feature is the constant difference in average pressure values among axisymmetric blades, that is, the blades with axisymmetric structures exhibit large-amplitude pressure oscillations around different average pressure values, and one revolution is equivalent to one rotating cycle due to the failure of hydraulic consistency. Further in-depth analysis reveals that pressure oscillations are realized by the adjustment of the resultant force between the Coriolis force and the potential rothalpy gradient to fluid motions under the sinusoidal disturbance of gravity, and its action path presents a hysteresis loop with the impeller rotating. This adjustment mode leads to a special conversion between the gravity potential energy, pressure energy, and the kinetic energy, and, thus, the hydrostatic pressure difference at the initial phase cannot be fully eliminated; the pressure transition between the sides along and against the gravity is inconsistent. This finding suggests that the difference induced by the hydraulic inconsistency should be considered if the conventional similarity conversion is applied to large-scale tubular pumps.

Numerical Analysis of Energy Loss in Stall Zone for Full Tubular Pump Based on Entropy Generation Theory

As a low-head and non-drive pump, the head reduction and stall advance are the key factors that restrict the popularization and application of the full tubular pump (FTP). In this paper, the shear stress transport (SST) k-ω turbulence model is used for the numerical calculation of the FTP. Additionally, based on the entropy generation theory, the energy loss and main distribution zones of the FTP under all working conditions are analyzed, and the mechanism of inducing its stall advance is explored. By comparison, we found that there is little difference between the numerical simulation results and the model test. Turbulence entropy generation has a high proportion under small flow conditions, which is mainly reflected in the outlet flow separation zone of the suction surface of the impeller blade, the guide vane inlet zone where inlet deviation exists, and the trailing edge of the guide vane where the flow separation exists. Compared with the axial flow pump (AFP), when the flow rate decreases, the clearance reflow between the stator and rotor induces the deterioration of the flow at the impeller inlet, and the turbulent entropy generation in the impeller channel increases rapidly, making the FTP enter the stall zone ahead of time. The clearance backflow affects the flow pattern of the inlet pipe, making the turbulence entropy generation in the outlet area of the inlet pipe increase. The total entropy generation in the stator–rotor region is little affected by the pump flow conditions, and it is mainly affected by different stator–rotor backflow clearance dimensions. This study can provide a reference for exploring the energy loss of the FTP and revealing its stall characteristics.

Analysis of internal flow characteristics and entropy generation of low head bulb tubular pump

To study the internal flow characteristics and energy characteristics of a large bulb perfusion pump. Based on the CFX software of the ANSYS platform, the steady calculation of the three-dimensional model of the pump device is carried out. The numerical simulation results obtained by SST k-ω and RNG k-ε turbulence models are compared with the experimental results. Finally, SST k-ω is selected for subsequent calculation. With the help of the flow line diagram and turbulent kinetic energy table of the whole flow channel of the pump device, the flow components of the pump device under different working conditions are analyzed, and the pressure and velocity distribution at the impeller and guide vane are analyzed by pressure cloud diagram and velocity cloud diagram. It is found that there are three high-pressure areas in the impeller and guide vane section, and the high-pressure regions are mainly distributed in the middle of the impeller channel. As the head decreases, the pressure at the impeller and guide vane positions decreases gradually, and the flow rate increases. Based on the entropy production principle, the wall entropy production and the distribution of mainstream entropy production at the impeller and guide vane parts are analyzed.

Numerical investigation on the mechanism of impeller hub corner separation flow and induced energy loss in the bulb tubular pump

Numerical investigation on the mechanism of impeller hub corner separation flow and induced energy loss in the bulb tubular pump

Flow Characteristics and Optimization Design of the Stator–Rotor Cavity of the Full Tubular Pump

The full tubular pump device is taken as the research object in this article. This research method adopts the numerical simulation technology based on the SST (Shear-Stress-Transport) k-ω turbulence model to explore the internal flow characteristics of the stator–rotor cavity of the full tubular pump and optimize the stator–rotor clearance structure. The research shows that under the design conditions, compared with the axial flow pump, the torque increases by 47.91 N·m at the stator–rotor cavity structure and the efficiency decreases by about 20%. The torque at the rotor clearance of the full tubular pump accounts for about 50% of the torque at the rotor. Since there is a large area of backflow on both sides of the cavity, and there is a vortex structure on the inlet side of the cavity, it shows that the rotor structure and its area greatly affect the operating efficiency of the pump device. With the reduction in the rotor force area, the clearance length, and the outer diameter of the disc, the operating efficiency of the pump device gradually increases. Under the design conditions, the optimized model has a maximum efficiency increase of 14.04% and the torque at the cavity rotor is reduced by 39.25 N·m. The results show that the operating efficiency of the full tubular pump is closely related to its rotor structure area, and the force area of the rotor structure needs to be controlled in the actual design process.

Investigation on the Effect of the Shaft Transition Form on the Inflow Pattern and Hydrodynamic Characteristics of the Pre-Shaft Tubular Pump Device

The shaft tubular pump device is widely used in low head pumping stations in plain areas. The N-S equation and the SST k-ω turbulence model are adopted. Then, the investigation on the influence of the shaft transition form on the inflow pattern and hydrodynamic characteristics of the pre-shaft tubular pump device is carried out. By designing three transition forms of shafts, different inflow patterns are provided for the tubular pump device. The characteristic parameters of the shafts and external and internal flow characteristics of the pumping device under different inflow patterns are compared and analyzed. Finally, the optimal transition form is selected for model tests, and unsteady pressure pulsation characteristics are studied. The results show that the flow pattern in the inlet passage of each case is relatively uniform and smooth, and the range of the high-efficiency zone of the pump device is roughly within 0.9Qd–1.2Qd. The energy loss and the weighted average angle on the outlet of each case are similar. The axial velocity distribution uniformity on the impeller inlet of case 1 is better than that of the other cases. The numerical simulation results are consistent with the experimental results, and the numerical simulation method is reliable. Under the design condition, the pressure pulsation amplitude at the impeller inlet is the largest. It gradually increases from the hub to the shroud. The main frequency of pressure pulsation is the blade frequency. The pressure pulsation amplitude at the impeller outlet decreases from the hub to the shroud. The main frequency is not constant due to the rotor–stator interaction between the impeller and the guide vane. The outcome will be beneficial to the design and optimization of the shaft tubular pump device, which is helpful for broadening the corresponding theory and applying it to the actual project.

Numerical study of the energy loss in the bulb tubular pump system focusing on the off-design conditions based on combined energy analysis methods

The unsteady flow characteristics of the low-head bulb tubular pump highly affects the operation efficiency and stability of the whole system. The purpose of this paper is to investigate the dominating loss area in a typical tubular pump using the combined energy analysis methods. The transient multi-condition flow through the pump system is simulated based on N–S equation integrating SST k-ω model. The power loss characteristics of each flow passage component are analyzed in terms of total pressure variation, entropy production and energy balance equation. The turbulent entropy generation power (PSD') in the entropy production and the turbulent kinetic energy production (PL3) of the energy balance equation are the primary source of power loss, indicating that the fully developed turbulent flow tends to generate considerable loss in the pump system, followed by the power loss of solid wall (PSW and PLW). The distribution of power loss in the impeller and diffuser was comprehensively exhibited and it was found that the undesirable flow patterns are mainly caused by blades and walls. The rim region in impeller domain with volume fraction of 15% induces the energy loss of approximately 45% due to the presence of solid wall and tip leakage vortex (TLV). Furthermore, the individual grid volume is considered to better locate and visualize regions with our great interest, and a number of typical vortex structures are identified under several flow rates showing that the positive attack angle is more likely to caused flow instability and energy loss at low flow rate condition.

Numerical Simulation Analysis on Hydraulic Optimization of the Integrated Pump Gate

Based on the Reynolds time mean N-S equation and standard k-ε turbulence model and using Computational Fluid Dynamics technology, this study aims to integrate the brake pump to carry out numerical simulation. Through the adoption of different arrangements of impending height and spacing, the hydraulic characteristics of the full tubular pump unit are analyzed. The two-dimensional streamline, velocity and pressure distribution, and three-dimensional streamline, axial velocity and vorticity distribution of the front pool of each scheme are displayed. The results show that the recommended pump installation height is 0.8 Dd, the maximum limit value of the pump station design specification; in the dual-pump mode, the recommended pump spacing is 2.00 Ds.

Analysis of Transient Characteristics of Submersible Tubular Pump During Runaway Transition

In order to study the transient characteristics of the submersible tubular pump in the process of power failure, the 6DOF model was used to carry out three unsteady numerical values for the whole flow channel of the pump. The results show that the calculation results of the 6DOF model based on the fourth-order multi-point Adams–Moulton formula are in better agreement with the experimental results than the first-order format to predict the impeller motion. When the unit is powered off, the speed and flow of the pump device decrease rapidly with time. At the maximum head 3.41 m, when the unit enters the runaway condition, the speed is about −1.88 times the initial speed and the flow rate is about −1.98 times the initial flow. The axial force and radial force of the impeller increase alternately, and compared with the normal operating condition, the radial force is significantly increased. In the process of the pump device changing from forward flow to reverse flow, the internal flow state of the pump device is relatively chaotic, and there are a large number of vortices in the flow channel, which is easy to cause structural vibration. Before reaching the runaway state, a large number of vortices also appear inside the impeller and guide vane, causing flow blockage, especially when the flow rate is zero. At the same time, the reverse flow impact causes the local pressure on the blade surface to increase, which threatens the stability of the blade structure. The pressure at the impeller inlet, impeller outlet, and guide vane outlet monitoring points is the largest near zero flow, and the smallest during runaway. The main frequency of the pressure pulsation in the pump device is the blade pass frequency (fBRF) and its harmonics (2fBRF, 3fBRF, 5fBRF, etc.), and the pressure pulsation intensity increases with the increase of the impeller speed. The results of this study provide a theoretical reference for the operation of the submersible tubular pump to ensure the safety and stability of the pumping station.

Numerical Simulation of Internal Flow Characteristics and Pressure Fluctuation in Deceleration Process of Bulb Tubular Pump

In order to explore the change in internal and external characteristics and the pressure fluctuation of the large bulb tubular pump unit during deceleration, a transient and steady three-dimensional (3D) numerical simulation is executed, based on the standard k-ε turbulence model and the change in boundary conditions such as flow rate. Finally, the pressure fluctuation data are analyzed by the wavelet method. There is a good agreement between the experimental data and numerical simulation results. During the deceleration process of the unit, the head decreases linearly while the efficiency remains stable. Meanwhile, the shock phenomenon and hysteresis effect appear before and after the unit head deceleration. Although there are vortex and backflow in the outlet conduit during deceleration, the pressure distribution on the suction surface of the impeller blades changes uniformly and significantly. The pressure fluctuation changes on the inlet surface of the impeller are more obvious during the deceleration: the closer to the hub, the greater the pressure, and this change decreases with decreasing radius. The fluctuation energy is mainly concentrated in the high-frequency region of 100–120 Hz and decreases uniformly with the deceleration of the rotational speed. This paper provides a reference for the energy utilization and safe operation of the water pump unit in adjusting speeds with variable frequency.

Unsteady Simulation of the Internal Flow in a Tubular Pump Considering Tip-Leakage Flow

Tip-leakage vortex is a commonly-seen phenomenon in tubular pump runners because there will be always gap between blade and pump shroud. In the operation process, the tip-leakage vortex is unstably varying. Pressure in the vortex core is relatively low and may induce cavitation in extreme conditions. The operation stability will be strongly impacted. As an effective tool, computational fluid dynamics (CFD) can be used in predicting the vortical flow in pumps. In this study, unsteady CFD simulation is conducted with the visualization of tip-leakage vortex using the Q criterion. The design-load condition is mainly studied. The temporal characters, their frequency domain features and their spatial distributions are fully analysed. This study will help understanding the tip-leakage vortical flow in the tubular pump and enhance the operation stability of low-head pumping stations.

Comparison of the Hydraulic Performance and Pressure Pulsation Characteristics of Shaft Tubular Pump Device under Multiple Working Conditions

For pumping station projects in plain areas, shaft tubular pump devices are often used due to the low head. In actual operation, the common working range of the pump device is generally 0.8 Qbep~1.2 Qbep. Therefore, it is of great significance to study the hydraulic performance and pressure pulsation characteristics of the pump device in the working range. In this study, the hydraulic performance of a shaft pump device was tested by a model test, and the internal flow and pressure pulsation characteristics were analyzed by numerical simulation. The results obtained from the model test and numerical simulation were in general agreement, indicating that the numerical results were reliable. The results show that the inlet passage has a good flow pattern in the working range, which may offer a favorable flow state for the impeller. When Q = 0.8 Qbep, the flow in the impeller and guide vane was chaotic, the guide vane had a poor adjustment function on flow direction, and the flow in the outlet passage presented in a spiral motion. When Q = 1.0 and 1.2 Qbep, the flow in the impeller and guide vane was ordered, and the spiral flow in the outlet passage improved. In the working range, the pressure pulsation was similar. The main frequency at the impeller inlet and outlet was consistent with the blade passing frequency. For the same flow rate condition, the amplitude rose from hub to shroud and declined from impeller inlet to outlet. In addition, the amplitude decreased with an increasing flow rate.

Comparison of Energy Performance of Shaft Tubular Pump Device at Two Guide Vane Inlet Angles

In order to improve the pump device efficiency of the frequent operating condition of the extra-low head pumping station, the energy performance of the front-positioned shaft tubular pump device at two guide vane inlet angles has been researched. Based on the function of the guide vane in the pump device, the guide vane blades are divided into three parts: the inlet section, the middle section, and the outlet section. Combining numerical simulation and model tests, the energy performance of the pump device with the inlet section angle adjusted to 0° and −12° were studied and compared, respectively. The research results indicate that the inlet section angle of the guide vane has a significant effect on the energy performance of the pump device. When the guide vane inlet section is adjusted clockwise, the pump device efficiency of the optimal operating point—while the efficiency of the pump device at a low head and large discharge that deviate from the optimal operating point—will be improved. The farther the working condition deviates from the optimal operating point, the greater the influence. Within the scope of the working conditions studied in this paper, the pump device efficiency of the optimal operating point is reduced by about 2%, and the pump device efficiency in the low head and high flow conditions is increased by 5% at the maximum. Adjusting the inlet section angle of the guide vane, the flow pattern in the guide vane will be improved, and the hydraulic loss of the guide vane will be decreased, thus the pump device efficiency is increased. The numerical calculation results of the energy performance agree with the model test results; the maximum error of the pump device efficiency is less than 7%. Adjusting the angle of the inlet section of the guide vane has great significance to the hydraulic design and engineering application of the extra-low head pump device.

Experimental and Numerical Study on the Hydraulic Characteristics of an S-Type Bidirectional Shaft Tubular Pump

In order to study the characteristics of a bidirectional shaft tubular pump with S-type symmetric airfoil blades, a prototype model was designed, manufactured, and tested. The energy characteristics, cavitation characteristics, and runaway characteristics of the pump were obtained under forward and reverse operating conditions for five different blade angles. Based on the basic equations of the pump and the inlet and outlet velocity triangles, combined with model tests and numerical simulations, the hydraulic performance of the pump was extensively analyzed and evaluated. In addition, semi-empirical equations for reverse efficiency and runaway characteristics were proposed. The dynamic pressure-drop coefficients were introduced to compare the cavitation performance under different flow rates in forward and reverse operations. The results reveal that the efficiency of the pump in reverse operation is greater than that of forward operation only under a very small flow rate. While the cavitation performance of the bidirectional pump in the two operating modes is almost the same, the runaway speed and backflow rate in forward operation are considerably greater than those of reverse operation. The results provide an important reference for the safe and stable operation of bidirectional shaft tubular pumps.

Mechanical property analysis of shaft tubular pump rotor with different blade angle based on fluid-structure interaction

Abstract Shaft tubular pump is widely used in large and medium-sized pumping stations with ultra-low head. But occasionally the blade cracks or even breaks, which seriously restricts the safe and stable operation of the pump station. In order to obtain the mechanical properties of the pump rotor with different blade installation angles, the fluid-structure interaction numerical simulation method is applied to analyze the structure of the pump rotor. Based on the SST k-ω model and the structured grid of the whole flow field, the three-dimensional numerical simulation of the internal flow field of the pump device is carried out by using CFX, and the reliability of the simulation is verified by model test. Then, the static analysis and modal analysis of the pump rotor structure under different working conditions are carried out by using Workbench. From the results, it can be found that the axial force increases with the increase of blade installation angle at a same flow rate. And at a same flow rate, the maximum deformation and equivalent stress increases with the increase of the blade installation angle. Finally, the change of the blade installation angle mainly affects the third and sixth order frequency which are only showed as blade vibration. Therefore, all of these results indicate that the blade installation angle has obvious influence on the mechanical property of the rotor of shaft tubular pump.

Experiment on Influence of Blade Angle on Hydraulic Characteristics of the Shaft Tubular Pumping Device

In order to understand the influence of blade angle on the hydraulic characteristics of a shaft tubular pumping device, the energy characteristics, cavitation characteristics, runaway characteristics, and pressure pulsation of the tubular pumping device under different blade angles were studied by a model test. Comparing the efficiency of the best efficiency point of the pumping device under different blade angles, it can be seen that when the blade angle is +4°, the efficiency of the best efficiency point of the pumping device is the lowest, 74.10%. When the blade angle is −4°, the efficiency of the best efficiency point of the pumping device is the highest, 79.75%. Comparing the cavitation characteristics of the pumping device under different blade angles, it can be seen that when the blade angle is −4°, the overall cavitation performance of the pumping device is the best. When the design head point is deviated, the NPSHav (Net positive suction head available) of the pump will increase. At the same blade angle, the runaway speed increases with the increase in head. The runaway speed of the prototype pump decreases with the increase in blade angle. When the blade angle is −6°, the runaway speed of the prototype pump is the largest, which is not conducive to the safe operation of the pumping station. When the blade angle is −4°, the variation law of pressure pulsation is small, and there is no abnormal pulsation. The tubular pumping device has satisfactory hydraulic performance, high efficiency, cavitation, and runaway characteristics. Therefore, the shaft tubular pumping device has wide application prospects under ultra-low head, and we recommend prioritizing it in low-head pumping stations.

Flow Loss Analysis and Optimal Design of a Diving Tubular Pump

As important parts of underground water conveyance equipment, diving tubular pumps are widely used in various fields related to the national economy. Research and development of submersible pumps with better performance have become green goals that need to be achieved urgently in low-carbon development. This paper provides an effective approach for the enhancement of the performance of a diving tubular pump by adopting computational fluid dynamics, one-dimensional theory, and response surface methodology. First, the flow loss characteristics of the pump under several flow rate conditions are analyzed by entropy production theory, and then the impeller and guide vanes are redesigned using the traditional one-dimensional theory. Then, the surface response experimental method is used to improve pump hydraulic efficiency. The streamline angle (A) of the front cover of the impeller blade, the placement angle (B) of the middle streamline inlet, and the placement angle (C) of the rear cover flowline inlet are the response variables to optimize the design parameters of the diving tubular pump. Results show that wall entropy production and turbulent kinetic energy entropy production play the leading role in the internal flow loss of the diving tubular pump, while viscous entropy production can be ignored. The flow loss inside the impeller is mainly concentrated at the inlet and the outlet of the impeller blade, and the flow loss inside the guide vane is mainly concentrated in the area near the guide vane and the entrance of the guide vane. A, B, and C are all significant factors that affect efficiency. The order of the influencing factors from strong to weak is as follows: A2 (p = 0.000) > C (p = 0.007) = A × B (p = 0.007) > B (p = 0.023) > B2 (p = 0.066) > A × C (p = 0.094) > A (p = 0.162) > C2 (p = 0.386) > A × B (p = 0.421). The best combination of response variables after surface response test design is A = 9°, B = 31°, and C = 36°. After optimization, the pump efficiency and the head of the model pump are increased by 32.99% and 18.71%, respectively, under the design flow rate. The optimized model pump is subjected to tests, and the test data and the simulation data are in good agreement, which proves the feasibility of using the surface response method to optimize the design of the model pump.