Suction Pipe Research Articles

Cavitation preventation in centrifugal pumps using ANSYS

In this paper, a computational fluid dynamic (CFD) model was developed to assess cavitation phenomenon and its local effects on a centrifugal pump. The model included the temperature of the fluid, rotational velocity, and geometric configuration of the suction. The model was validated using the pump characteristics curves of the manufacturer with an error of 5%. Also, the minimum pressure contours and the vapor volume fraction were plotted. These contours show the pump boundary conditions (temperature and angular velocity) before cavitation occurs. Thus, the impeller zone where the cavitation phenomenon is more susceptible to occurrence was identified. In addition, this analysis determined characteristic parameters such as the limit on fluid temperature, the limiting angular velocity of the pump and the ratio between the diameters of the suction pipe and the pump inlet diameter. The proposed methodology is aimed as a reference for the study of local operating parameters to avoid cavitation in various types of hydraulic pumps.

Теоретические основы расчёта системы ввода органических удобрений во всасывающие трубопроводы насосных станций при удобрительных поливах сельскохозяйственных культур

Purpose: to substantiate theoretically the calculation of the system for introducing organic fertilizers into the suction pipelines of pumping stations during fertilizing irrigation of agricultural crops. Materials and methods. The foundations of calculating the system of introducing organic fertilizers into the suction pipelines of pumping stations during fertilizing irrigation are developed on the basis of literary sources and authors’ research. If there is a composition of nutrients in the manure of cattle (CM), horse, pig or sheep for the planned harvest of the adopted crop, the one-time and annual application amounts for the most toxic element – nitrogen are calculated. It is indicated that in case of a deficiency of nutrients for phosphorus and potassium, an additional calculation for the mineral fertilizers introduction is carried out. Results. An example of calculating the annual amount of irrigation mixture for corn for silage when removing nutrients with an accepted harvest of green mass of 500 q/ha is provided. The calculation is determined by: application rate, cubic meters/ha; nitrogen content in the application rate, kg/ha; the annual volume of the irrigation mixture, with a nitrogen content of 0.15 %. In the example, the calculation is performed for the possible presence of fertilizers in cattle drains according to two variants of technological schemes: without using a mixer, when introducing fertilizers from the storage tank directly into the suction pipeline; using a mixer, when introducing fertilizers from the storage tank into the suction pipe of the mixer. For the calculation, the initial data of hydraulic parameters are given, the consumption of cattle manure with a humidity of 92–95 % is taken as the main calculation parameter. Conclusions: the developed theoretical calculation of the system for introducing organic fertilizers into the suction pipelines of pumping stations allows determining the rate of one-time and annual fertilizer application and determining the hydraulic parameters of the fertilizer input system without a jet mixer.

荞麦旋风分离清选的参数分析与试验研究

Based on the material characteristics of buckwheat, the cyclone separation and cleaning test bench were designed. The cleaning rate and loss rate of the buckwheat separation and cleaning by the influencing factors of the investigation were studied through single factor and orthogonal tests. The single-factor test results show that the cyclone separation and cleaning performance is better when the speed range of the suction fan is 800~1200 r/min, the speed range of the feeding fan is 600~1200 r/min, and the length range of the suction pipe is 100~250 mm. The regression equation model of the cleaning rate and loss rate was constructed, and the response surface analysis of the test influencing factors and their interaction was carried out. The results show that the speed of the suction fan has the most significant influence on the cleaning rate and loss rate, followed by the speed of the feeding fan and the length of the suction pipe in the separation cylinder has the least effect. By optimizing and solving multi-objective parameters of the regression equation model, reasonable experimental parameters are obtained. The appropriate speed of the suction fan is 1055 r/min, the appropriate speed of the feeding fan is 600 r/min, and the proper length of the suction pipe in the separation cylinder is 175 mm. The cleaning rate and the loss rate of the cyclone separation and cleaning system were 94.78% and 1.67%, respectively.

Stability Analysis of Cavitation Surge in Hydraulic System Considering Response Delay of Cavitating Pump

Cavitation surge is a system instability caused by mutual interference between cavitation and a hydraulic system. A stability analysis for the cavitation surge was performed based on the unsteady characteristics of the cavitating pump, that is, the response delay of the pressure rise against the suction and discharge flow and suction pressure oscillations. Ordinary differential equations were derived from linear unsteady momentum and continuity equations, and the simplified-derived ordinary differential equations clearly show the onset criteria of stability and dynamic instabilities. The relatively short discharge and large suction pipe loss had a stabilizing effect on the cavitation surge. The positive quasi-steady suction and discharge flow gains as well as the negative quasi-steady suction pressure gain cause surge instability. The phase advance of the pressure rise against the flow and pressure oscillations also leads to surge instability.

Experimental study of an asymmetric valveless pump to elucidate insights into strategies for pediatric extravascular flow augmentation

Asymmetric pumping is a sub-category of valveless pumping in which a flexible tube is rhythmically compressed in the transverse symmetry plane. Due to the resulting asymmetry between the suction and discharge pipes, a net pumping head is achieved. Asymmetric pumping is regarded as one of the main mechanisms responsible for the Liebau effect in addition to impedance pumping. However, there remains a paucity of research surrounding the governing parameters of asymmetric pumping. Here, we conducted an experimental study of the performance of an asymmetric pump, with an aim to assess its potential for extravascular flow augmentation. A custom flexible latex tube and experimental platform were developed for this purpose. We tested various tube thicknesses and pinching frequencies. Our results demonstrate that the performance is within the range of physiological requirements for pediatric circulatory devices (~ 1 L/min and < 30 mmHg). We conclude that due to the absence of reverse flow and its mechanical simplicity, pure asymmetric pumping is promising for selected cardiovascular applications with less complexity than other valveless techniques.

Fluidic Thrust, Propulsion, Vector Control of Supersonic Jets by Flow Entrainment and the Coanda Effect

Thrust, propulsion, vector control of supersonic jets has been applied to jet and rocket engines, ejectors, and other many devices. In general, there are two approaches to this type of control, namely mechanical moving systems and fluidic thrust vector control systems without moving parts, with mechanical moving systems being the most common. However, generally speaking, these systems are very complicated, and more simple methods and devices are desired. In this study, an extremely simple method for the thrust vector control of a supersonic jet by a fluidic Coanda nozzle (FC-nozzle) using the entrainment of the surrounding fluid and Coanda effect is newly proposed. The FC-nozzle consists of a pipe nozzle (Pi-nozzle), spacer, and linearly expanded Coanda nozzle (Co-nozzle) with eight suction pipes (Su-pipes) installed to surround the jet from the Pi-nozzle. The jet from the Pi-nozzle flows straight with the entrainment flow of the surrounding fluid. When some Su-pipes are closed, the pressure between the jet and Co-nozzle wall decreases, and subsequently, the jet deflects to the closed side of the Su-pipe and reattaches to the wall by the Coanda effect. The flow characteristics and deflection characteristics of the supersonic jet from the FC-nozzle are examined by the visualized flow pattern using the Schlieren method and measurements of the velocity distribution. As a result, it is shown that by changing the number of Su-pipes and the locations at which they are closed, the deflection angle and circumferential position of the jet from the Pi-nozzle can be easily controlled.

Flow Characteristics and Anti-Vortex in a Pump Station with Laterally Asymmetric Inflow

In a laterally asymmetric intake pumping station, the flow direction in the forebay is not consistent with flow in the intake channel. Thus, the adverse flow patterns, such as bias flow, large-scale vortex and asymmetric flow occur frequently in the forebay and sump. Based on the Reynolds-averaged Navier-Stokes (RANS) equation and the RNG k-ε turbulence model, a recent flow pattern in a laterally asymmetric intake pumping station was numerically simulated and analyzed, and effective vortex elimination measures were proposed. For the original scheme, seriously biased flow combined with large-scale vortices were observed in the forebay and several vortices occurred in the sump. To suppress the clash inflow in the south and north intake channel, the “straight diversion pier + curved wing wall” and “straight diversion pier + curved wing wall + V-shaped diversion pier” were installed separately. The” symmetrical 川-shaped diversion pier” and “symmetrical 川-shaped diversion pier + circular column” was utilized to eliminate the bias flow and large-scale vortices in the forebay. Finally, the “three- sectional diversion pier”, “three- sectional diversion pier + triangle column” and “three- sectional diversion pier + triangle column + straight back baffle” was applied to decrease the vortex and asymmetric flow near the suction pipe of the sump. By attaching the rectification measure schemes in the intake channel and the forebay, the bias flow and large-scale vortex in the forebay were suppressed to varying degrees. The schemes significantly reduced the recirculation coefficient and greatly reduced the recirculation volume. By utilizing the vortex elimination measures in the sump, the vortex and asymmetric flow basically disappeared, the velocity distribution tended to become more uniform, and the flow rate distinction of each pump was smaller. The outcome can be used to provide a reference and basis for the improvement of flow pattern in similar laterally asymmetric intake pump stations.

Forecasting the energy characteristics of a reversible hydraulic machine for a head up to 250 m

BACKGROUND: At present, in the pressure zone of 50650 m for pumped storage power plants, hydroelectric units with classic single-stage radial-axial reversible hydraulic machines, which have a relatively simple design of the impeller and cylindrical guide vane, have received the most widespread energy performance, but are relatively quiet, large-sized and metal-intensive hydraulic machines. Numerical research and design of this type of machines are given special attention. The current trend is the design of flow parts based on numerical simulation of the flow. The most well-known commercial software products that implement finite volume numerical simulations are Ansys Fluent, Ansys CFX, StarCD, Numeca, Flow Vision and CADRUN. In the work under consideration, the calculations were performed using the Ansys CFX software package version 2021R1. Today, due to the lack of numerical capacity, the task of developing and using a technique that will allow obtaining an acceptable result with optimal time spent on data preparation and computational studies remains an urgent task.&#x0D; AIMS: The aim of the work was to present an economical methodology for numerical simulation of energy characteristics.&#x0D; METHODS: The methodology consists in describing the problem statement, the computational grids used, and the assumptions made for the optimal use of computing resources without a significant loss in the accuracy of the results.&#x0D; Object of computational research: The presented article investigates the flow part of a radial-axial pump-turbine designed for application to a maximum head of up to 250 m.&#x0D; RESULTS: Numerical modeling of power characteristics of on-pump and turbine modes is performed. A brief description of the problem statement, computational grids used, and assumptions made is given. A comparison of calculation results with experimental data of model tests is presented. The comparison results are presented in the relative form for the main parameters: pressure, efficiency, reduced rotational speed and flow rate.&#x0D; CONCLUSIONS: It is recommended to use SST model of turbulence in a stationary statement in order to predict the power characteristics of pump-turbines. The use of economical block-structured grids, as well as the performing of calculations only in the region of one blade of the guide vanes, one impeller blade and a suction pipe with the use of preliminary results of calculations in a spiral chamber allow using computational resources optimally without significant loss of accuracy of the results.

Experimental study on vibration characteristics of salt cavern leaching tubing for underground natural gas storage

Leaching tubing is an important tool for building underground gas storage. Its reliability and stability directly affect the building process. However, buckling deformation or fracture often occurs in leaching tubing due to severe vibration. In order to study the vibration characteristics of leaching tubing, a large experimental system is designed. Modal analysis is performed to examine characteristics of leaching tubing. The result of research shows that pressure pulsation of internal turbulence primarily induces the vibration of leaching tubing. Vibration response frequency of leaching tubing is similar to the turbulence pressure pulsation frequency. Meanwhile, amplitude at the bottom and middle of center tube is large. These locations are the risk points of vibration failure and need more attention. Furthermore, the response frequency and amplitude of center tube in reverse circulation are greater than those in direct circulation. Excessive vibration of center tube can be avoided by limiting water injection flow rate and two-port distance. The research results can provide some reference for construction engineers of gas storage and vibration researchers of suction pipe and discharge pipe.

A novel active deep-sea low-damage pressure-retaining organisms sampler

Capturing less damaged organisms samples is the basis for research on the biological communities, living environments, biological life compositions, and biological tissue structures of organisms livinin the deep seabed. The hadal snailfish is pressure-tolerant, cold-tolerant, and easily damaged. This research used a hydraulic suction macro-biological pressure-retaining sampler (HSMPS) to capture less damaged hadal snailfish samples via pumping. As the hadal snailfish is sucked into the macro-organism pressure-maintaining sampler, it inevitably collides with the suction pipe in the diversion area (SPDA) and the inner wall of the pressure-maintaining cylinder in the pressure-maintaining area (PCPA). Therefore, a finite element analysis model of a hadal snailfish with a real geometric shape was constructed by obtaining the material mechanical properties of different parts of the fish on the seabed through static compression tests, and the dynamic modeling and response analysis of the hadal snailfish during the capture process was carried out. Moreover, the dynamic response changes of the stress, strain and acceleration of various tissues and organs of the hadal snailfish during the capture process were determined, thereby providing technical support for the research and development of marine biological sampling equipment.

Design and Manufacture of Machine for Removing Ceratophyllum Demersum and Other Plankton in Rivers

Ceratophyllum plant covers most waterways, including lined channels and trenches. This plant causes a loss in the amount of runoff, velocity of water in the channels, and reduces the drainage rates. This research aims to design and manufacture a machine to clean the water intake outlet for the filtering station of Karbala drinking water by removing plankton, Ceratophyllum plant and algae, and throw these impurities out by means of adding catchers to the machine. As a result of gathering of these floating plants during runoff, it around water surrounding channels intake that were went to suction pumps, so that the channels are blocked. That is why, the workers would be frequently getting down to the river for cleaning after shutdown of the pumps. After studying the topic and coming up with an idea, according to which the design and technology drawings of the machine and determining the location where the device will be tested after implementation at different speeds (30, 60, and 100 m/min.). Three types of catchers (holders) of Ceratophyllum Plant and other Plankton were used. It was obtained that the cross-sectional area of the flow of the machine is greater than that of the suction pipe of the water purification station. The best linear speed for this machine was 30 m/min, which removes impurities by 2.2m3.

Numerical Simulation of Gas–Liquid Two-Phase Flow CFD–PBM Model in a Micro–Nanobubble Generator

A micro–nanobubble generator is the most critical component of micro–nano flotation equipment. Understanding the bubble generation characteristics in the generator plays a vital role in optimizing the performance of the device and improving the flotation of fine-grained minerals. In this study, to explore the generation and evolution of bubbles in the micro–nanobubble generator of a cyclonic jet flotation cell, the flow field parameters of the gas–liquid two-phase flow inside the generator were solved using CFD–PBM combined with Luo’s population balance model. The internal bubble size was in the range of 0.99 μm to 140 μm. After the gas entered the generator from the suction pipe, it mainly moved in the center of the tube, and the diameter of the bubbles was relatively large at this time. With the bubble movement, large bubbles in the center were broken into small bubbles and then moved toward the periphery of the tube. Thereafter, the smaller-diameter bubbles gathered and formed large-diameter bubbles. The average diameter of the generated bubbles gradually increased from approximately 30 to 110 μm.

Investigation of suction pressure pulsation prediction of rotary compressor with total variation diminishing scheme and one-dimensional accumulator model

The suction pressure pulsation plays a significant role in rotary compressor performance, so employing gas dynamic model for simulation is critical for compressor performance prediction and structure design. Comparing with the conventional Lax-wendroff two-step (LW2) scheme which has been usually utilized with good behaviors of speed and stability, this paper adopted the total variation diminishing scheme with higher convergence speed and less dispersion. And the common zero-dimensional model for the accumulator is updated to a one-dimensional model achieving more accurate pressure results at the suction pipe inlet. The simulation results of instantaneous pressure are also compared with experimental measured data under different conditions. The Pearson Correlation Coefficient of simulated pressure curves are all higher than 0.9 and the relative errors of predicted performance are almost all less than 5%, which indicates better agreement on pressure pulsation simulation and performance prediction.

Application of gated conduits for fertigation in irrigation systems

Abstract Fertigation involves dissolving fertilizer in irrigation water, and requires uniform water distribution and fertilization. A gated conduit can be used to inject liquid fertilizers or chemicals into a pressurized irrigation system. When the conduit gate is partially opened, a vacuum draws the fluid from the suction pipe into the conduit. An experimental study was conducted to investigate the fluid-injection ratio of gated conduits, which was shown to be high. The density and viscosity of the fluid were the most important parameters affecting the fluid-injection ratio. That ratio increased with increasing Froude number. It decreased as the gate opening proportion increased and with increasing conduit length. A design formula related to the Froude number, and the fluid's density and viscosity is presented to enable estimation of the fluid-injection ratio.

Removal of sediment through hydro-suction revisited: An extensive review of the hydro-suctioning method, widely used for sediment removal from the water bodies

Abstract Hydro-suctioning is used to remove the deposited sediment from water bodies. A suction pipe is placed on/above/below the sediment bed, and deposited sediment is removed using suction. The sediment movement during hydro-suction, flow pattern, temporal sediment concentration, and scour profile are reviewed extensively and summarized in this paper. It is seen that the sediment removal initiates due to lift forces and continues further due to a change in flow field that creates sediment resuspension. The sediment removal ceases if the suction inlet reaches a distance, i.e., critical suction inlet depth. Within this critical zone, when the hydro-suction initiates, sediment just below the suction pipe is first removed, leading to the maximum scour depth, i.e., below the sediment bed level. In this process, sediment from sides of the scour hole is hydrodynamically dragged towards the center, where it gets deposited, and a hump is formed at the center. At equilibrium, the sediment removal ceases. This paper discusses the equations predicting scour profile and critical inlet depth. It is seen that the research work dealing with the standardization of hydro-suction for fixation of suction pipe diameter, suction inlet depth, discharge, etc. is in quite a primitive stage and needs urgent attention.

Physical model setup and tests on cooling circulation water pumping intake system

Abstract The thermal power plant built by the Taiwan power company intends to use multiple cooling circulation water intake systems to introduce seawater from adjacent sea areas. The water in the front pool of the water inlet is introduced into the pump chamber through the large pump in the circulating water pump sump. The primary function of the pump chamber is to provide a stable and uniform flow condition before the large pump sucks in the seawater. When the hydro-dynamic conditions outside the pumping station are not ideal, and the inflow is relatively unstable, the pumping chamber can provide a buffer space for rectification. In addition, when the flow field near the suction intake of a large pump can maintain a certain degree of stability in space and time, it can reduce the frequency and intensity of the vortex or other harmful factors caused by the flow field. Moreover, a pump sump flow field can also maintain the pump's working efficiency, reducing vibration and maintenance costs. Although the relevant design standards such as the Hydraulic Institute (H.I.) standard in the United States or the British Hydromechanics Research Association (B.H.R.A.) standard in the United Kingdom can be consulted for different types of pumping room geometric layout planning and design recommendations. However, most design references are obtained from the boundary conditions of general cases. Therefore, these design criteria indicate that when the pump room geometry and flow conditions have special considerations or detail design, physical model tests should be conducted to verify it or correct the layout according to the model test results. Because the fluid mechanisms involved in the relevant research are complex, the current theoretical or numerical models are not enough to fully simulate flow fields. Therefore, it is necessary to conduct a physical model test based on the feasibility model scale. Based on the similarity theory to scale down prototype structures, the flow mechanism of preliminary design is reproduced, and the revised plan is also verified in the physical model to satisfy the project objectives. The qualitative flow field visualization method was used to observe the free surface vortex, subsurface vortices, and the swirl angle in the suction pipe under different layout schemes at each physical test case. The tested results show that the flow pattern and vortex strength are both acceptable with designed anti-vortex devices.

A new approach to measure gas holdup in industrial flotation Machines. Part III: Industrial prototype design and assessment

• An industrial gas holdup sensor prototype was validated in a 250 m 3 flotation cell at Los Pelambres. • A weakly dependence of sensoŕs discharge coefficient to Reynolds number was observed. • Gas holdup predictions were largely insensitive to errors in the anticipated pulp kinematic viscosity. • Submersible sensor provided robust accurate gas holdup measurement over long periods of time. An industrial gas holdup sensor was designed, constructed, and its performance assessed on a 250 m 3 self-aerated Wemco cell at Los Pelambres concentrator. The submersible sensor comprised a ceramic-liner IP68 magnetic flowmeter assembled to a stainless steel gas exclusion cell, which resembles an inverted truncated cone. The gas exclusion cell was designed to avoid low-velocity sections where particles could settle. When the sensor device is vertically immersed in an aerated pulp a continuous downward flow of pulp without bubbles is induced through it. A remotely installed processing unit converts the flow velocity signal, provided by the magnetic meter, into a gas holdup signal, by applying Bernoullís equation to the induced flow. The ideal velocity in the Bernoullís equation is obtained by multiplying the measured velocity and the discharge coefficient. The discharge coefficient was found to be fairly constant over a wide range of Reynolds numbers. Gas holdup measurements were compared against those obtained by sampling a fixed volume of aerated pulp using the JK Tech Air Holdup Probe. These tests were conducted on different days over nine months to allow for the pulp properties to change. Gas holdup changes in the flotation machine were achieved by restricting the air intake to the cell by placing a stainless steel cap on top of the air suction pipe. Short and long-term testing demonstrated the sensoŕs capability to provide reliable and accurate continuous-time gas holdup measurements for industrial flotation machines.

Characteristic Equation and Reflection Models of Air Column Resonant Surge

Fundamental models of air column resonant surge are proposed. It is assumed that the flow in the suction pipe is incompressible but the effects of compressibility and pipe friction are taken into account in the discharge pipe. The characteristic equation is derived and the differences of onset condition and frequency from those of extended Helmholtz resonant surge are discussed. A reflection model considering the wave reflections at the compressor and throttle is also proposed to obtain better understanding. The results of characteristic equation and reflection models agree nicely. The results are validated by comparisons with experiments.

自由界面渦による気相巻き込み現象の定量評価

On the gas-liquid interface of a sodium-cooled fast reactor, gas (bubble) entrainment can be caused by free surface vortices, which may result in, e.g. disturbance in core power. Therefore, it is important to develop an evaluation model to predict accurately the entrained gas flow rate for the prevention of such undesirable phenomena. In the previous studies, simple gas entrainment experiments have been conducted, in which, typically, the gas entrainment is caused by free surface vortex in an upper-tank and the entrained gas is separated from liquid in a lower-tank which is connected with the upper-tank by a suction pipe. The entrained gas flow rate had been measured while the liquid flow parameters, e.g. liquid level or flow rate, are changed. However, the influence of the pressure difference between the upper and lower tanks had not been focused on those studies. In this study, to measure accurate the entrained gas flow rate, a simple gas entrainment experiment is conducted with focusing on the effect of the pressure difference between upper and lower tanks. The pressure difference between upper and lower tanks are controlled by changing the gas pressure in the lower-tank. As a result, it is confirmed that the entrained gas flow rate increases with increasing the pressure difference between upper and lower tanks. By the visualization of the two-phase flow in the suction pipe, it is also observed that the pressure drop in the suction pipe increases with the increase in the entrained gas flow rate when intermittent liquid plug is generated in the two-phase flow.

Stress and Pressure Pulsation Analysis of Low Temperature Compressor Piping System in LNG Vaporizing Station

LNG (Liquefied Natural Gas) vaporizing stations are usually built in the cities and towns, and the BOG (Boiled Off Gas) pressurizing system is a very important element. In the pressurizing system, the severe vibration of the low-temperature reciprocating compressor may lead to a failure of the pipeline system and the equipment. Therefore, this paper analyzes the stress and pressure pulsation of the BOG compressor piping system in the LNG vaporizing station. The beam model was used to establish the pipe model. The static, harmonic and modal analysis were carried out based on the plane-wave theory and the pressure-fluctuation theory, and the influence factors of support spacing, the settlement of the fulcrum foundation, pipe pressure and elbow angle were analyzed. The main conclusions are as follows: (1) the unbalanced excited force caused by pressure pulsation greatly affects the stress of the exhaust pipe and compressor outlet pipe, and has less influence on the stress of the suction pipe and compressor inlet pipe; (2) although unbalanced excited force is generated in the elbow, it also has an impact on the straight pipe stress; (3) adding an expansion joint to the pipe of the BOG compressor can effectively reduce the stress of the pipe its the displacement, and can increase the flexibility of the pipe.