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Open AccessArticle

Comparative Analysis of the Hydrodynamic Performance of Arc and Linear Flapping Hydrofoils

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Processes 2023, 11(5), 1579; https://doi.org/10.3390/pr11051579 - 22 May 2023

Viewed by 297

Abstract

In order to improve the hydrodynamic performance of flapping hydrofoils and solve the problem of insufficient hydrodynamic force in plain river network areas, in this study, we consider the more realistic swing of fish tails and propose an arc flapping method, the coupled [...] Read more.

In order to improve the hydrodynamic performance of flapping hydrofoils and solve the problem of insufficient hydrodynamic force in plain river network areas, in this study, we consider the more realistic swing of fish tails and propose an arc flapping method, the coupled motion of which has three degrees of freedom: heave, pitch, and lateral displacement. Two flapping methods, positive arcs and negative arcs, were derived on the basis of the lateral displacement direction. By using the finite volume method (FVM) and overlapping grid technology, a numerical simulation was conducted to compare and analyze the pumping performance of three types of flapping hydrofoil, namely, linear, positive arcs, and negative arcs, in order to further provide guidance for the structural optimization of bionic pumping devices. The results showed that the wake vortex structures of the three flapping modes all had anti-Kármán vortex streets, but the wake vortex of linear flapping deflected upward, and the wake vortex of positive arc flapping tended to be further away in the flow field. In one cycle, thrust was always generated by the positive arc flapping hydrofoil and the linear flapping hydrofoil, but the thrust coefficient curve of the positive arc flapping hydrofoil was more stable than that of the linear flapping hydrofoil, and the peak value was reduced by 46.5%. In addition, under the conditions of a flow rate of 750

L \cdot s^{- 1}

and an average head of 0.006 m, the pumping efficiency of the positive arc flapping hydrofoil reached 35%, thus showing better pumping performance than the traditional linear flapping hydrofoil under conditions with ultra-low head. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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Open AccessArticle

Optimal Design of Perforated Diversion Wall Based on Comprehensive Evaluation Indicator and Response Surface Method: A Case Study

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Processes 2023, 11(5), 1539; https://doi.org/10.3390/pr11051539 - 17 May 2023

Viewed by 270

Abstract

To investigate the impact of parameters of diversion wall holes on the flow state in the forebay of a combined sluice-pumping station project and optimize the relevant parameters, a total of 50 numerical simulations based on the CFD technique were performed, adopting the [...] Read more.

To investigate the impact of parameters of diversion wall holes on the flow state in the forebay of a combined sluice-pumping station project and optimize the relevant parameters, a total of 50 numerical simulations based on the CFD technique were performed, adopting the design of orthogonal experiments with 25 schemes under self-draining conditions and pumping conditions, respectively. For synthesizing flow state evaluation indicators under self-draining and pumping conditions, the variation coefficient method was used, and the results were analyzed through the response surface method. Thus, the relationship between the parameters of the diversion wall holes and the comprehensive evaluation indicator was established. The steepest ascent method was used to obtain the optimal parameters, and the results showed that the optimized holes can balance the flow state under self-draining and pumping conditions in the combined sluice-pumping station project. Compared to the case with the diversion wall unperforated, the uniformity of axial velocity distribution in the 6# inlet channel and 7# sluice chamber increased by 6.6% and 5.2%, respectively, and the maximum transverse velocity decreased from 0.32 m/s to 0.21 m/s, with a fall of 34.4%. This study provides reference and technical support for the hydraulic characteristic analysis, optimization design and rectifying measures selection of the combined sluice-pumping station project. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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Open AccessArticle

Vibration Characteristics of Concrete Pump Trucks with Multiple Postures and Multiple Conditions Based on the Secondary Development of HyperWorks

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Processes 2023, 11(5), 1483; https://doi.org/10.3390/pr11051483 - 13 May 2023

Viewed by 287

Abstract

Due to the excitation generated by the periodically alternate pumping of dual-hydraulic cylinders, vibration of concrete pump trucks (CPT) occurs. Excessive boom vibration will seriously affect the service life and operation safety of CPT. At the same time, the long boom structure of [...] Read more.

Due to the excitation generated by the periodically alternate pumping of dual-hydraulic cylinders, vibration of concrete pump trucks (CPT) occurs. Excessive boom vibration will seriously affect the service life and operation safety of CPT. At the same time, the long boom structure of a CPT makes it very sensitive to the posture and pumping conditions, which directly affect the vibration characteristics of CPT in different postures and different working conditions. This paper establishes a finite element model of a type of CPT. Through force analysis of concrete in the straight pipe and elbow pipe during the pumping and reversing stages, an excitation model of the conveying pipe is established. Based on the secondary development of HyperWorks, a finite element model of CPT with multiple postures is built, and the dynamic response under multiple conditions is analyzed. Finally, the accuracy of the finite element model of CPT and the excitation model of the conveying pipe is verified by experiment. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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Open AccessArticle

Study on Flow Characteristics of Hydraulic Suction of Seabed Ore Particles

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Processes 2023, 11(5), 1376; https://doi.org/10.3390/pr11051376 - 02 May 2023

Viewed by 575

Abstract

Efficient and environmentally friendly ore collecting operation requires that the ore collecting head can provide just enough suction to start the ore particles in different working conditions. In this work, computational fluid dynamics and discrete element method (CFD-DEM) is used to simulate the [...] Read more.

Efficient and environmentally friendly ore collecting operation requires that the ore collecting head can provide just enough suction to start the ore particles in different working conditions. In this work, computational fluid dynamics and discrete element method (CFD-DEM) is used to simulate the hydraulic suction process of ore particles. After analyzing the pressure and velocity characteristics of the flow field, the effects of different suction velocities on the lateral displacement offset, drag coefficient C_d and Reynolds number Re_p of particles are studied. It is determined that the lifting force is caused by the different flow velocities of the upper and lower flow fields; particle start-up time and the lateral offset are inversely proportional to suction speed. When h/d ≥ 2.25, the vertical force on particles is no longer affected by h/d. When S/d = 2.5, F_Z decreases to 0 N; when h/d increases from 1.5 to 1.75, F_Z decreases by nearly half. Three empirical equations for F_Z represented by D/d, h/d, and S/d are obtained. After integrating the above three equations, the functional relationship of F_Z with D/d, h/d and S/d is finally obtained within a certain range. The errors of the equations are within 6%. The particle stress characteristics obtained in this paper can be applied to the establishment of ore collecting performance prediction model and provide data support for the research and development of intelligent ore collecting equipment. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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Open AccessArticle

Layering Vibration Transfer Path Analysis of a Flexible Supported Gear System Based on the Vibration Power Flow Theory

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Processes 2023, 11(4), 1233; https://doi.org/10.3390/pr11041233 - 16 Apr 2023

Viewed by 423

Abstract

In the marine gear system, the vibration of gears is transmitted to the ship foundation through shafts, bearings, housing, and isolators, and then the underwater noise is generated. Analyzing the vibration transfer properties and identifying the critical path can provide guidance to the [...] Read more.

In the marine gear system, the vibration of gears is transmitted to the ship foundation through shafts, bearings, housing, and isolators, and then the underwater noise is generated. Analyzing the vibration transfer properties and identifying the critical path can provide guidance to the low-noise design of the gear system. In this paper, a coupled gear-housing-foundation dynamic model is proposed for a flexible supported gear system, in which the flexibility of each subsystem and the coupling relationship between them are taken into account. The transferring process of gear vibration is divided into different layers between gears, shafts, bearings, housing, isolators, and ship foundation. Based on the vibration power flow (VPF) theory, detailed layering vibration transfer path analyses of the gear isolation coupled system are carried out for both location path and direction path, and the main paths are identified in a broad speed range. The results indicate that though the gear vibration transferred to the foundation attenuate layer by layer, there may be reverse VPF in some special location path and direction path under resonance conditions. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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Open AccessFeature PaperArticle

Analysis of Inner Flow in a Multi-Stage Double-Suction Centrifugal Pump Using the Detached Eddy Simulation Method

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Processes 2023, 11(4), 1026; https://doi.org/10.3390/pr11041026 - 28 Mar 2023

Cited by 1 | Viewed by 466

Abstract

In order to analyze the inner flow in a multi-stage double-suction centrifugal pump, which is regarded as a common way of knowing the current characteristics of the pump and as the basis of optimization for better performance, a numerical simulation considering the velocity [...] Read more.

In order to analyze the inner flow in a multi-stage double-suction centrifugal pump, which is regarded as a common way of knowing the current characteristics of the pump and as the basis of optimization for better performance, a numerical simulation considering the velocity field distribution characteristics and pressure fluctuation propagation law using the detached eddy simulation method was conducted. Additionally, the principle of entropy generation was put to use to quantify and compare the energy loss of different components. The results reveal that the existence of unstable flow structures in the first-stage impeller and a large number of vortical structures in the back-channel result in reduced operational efficiency of the pump. Furthermore, the pressure fluctuation intensity reaches its maximum with 0.15 at the blade trailing edge, which propagates to the tongue region of the forward flow channel and the double-volute under the low rates condition. Additionally, the main frequency of the monitoring points in the inter-stage flow channel and volute is basically located at a frequency of 198.667 Hz, which is twice the blade frequency. Consequently, the wall entropy production accounting for nearly 25% cannot be ignored and that the loss mainly occurs in the double-volute and the inter-stage flow channel due to the occurrence of irregular flow in the above components with more than 50%. The outcomes of this research present a valuable point of reference for the optimization of structural design in multistage turbomachines with various applications. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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Open AccessArticle

Liquid Loading of Horizontal Gas Wells in Changbei Gas Field

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Processes 2023, 11(1), 134; https://doi.org/10.3390/pr11010134 - 02 Jan 2023

Cited by 1 | Viewed by 934

Abstract

The Changbei gas field, which initially exhibited high gas-production performance, is dominated by large-displacement horizontal wells. With the decrease in reservoir pressure, the liquid loading in the gas well is currently severe, and production has been rapidly decreasing. Thus, recognizing the gas-well liquid [...] Read more.

The Changbei gas field, which initially exhibited high gas-production performance, is dominated by large-displacement horizontal wells. With the decrease in reservoir pressure, the liquid loading in the gas well is currently severe, and production has been rapidly decreasing. Thus, recognizing the gas-well liquid loading to maintain stable gas-well production is necessary. A method was established to identify the water source of the liquid loading in the Changbei gas field. First, formation water and condensate water were identified based on the mineralization of the recovered water and the mass concentration of Cl⁻ and K⁺ + Na⁺, and then the condensate content of the water produced in the gas well was qualitatively evaluated. The water–gas ratio curve for the gas well was plotted to determine whether the produced water was edge-bottom water, pore water, or condensate. Then a method was established to distinguish the start time of liquid loading in the gas well using a curve depicting a decrease in production; the method was also used to estimate the depth of the gas well where liquid loading occurs, according to the bottomhole pressure. First, based on the available production data, the Arps decline model was applied to fit the production curve for the entire production phase; the resulting curve was compared with the actual production curve of the gas well, and the two curves diverged when fluid accumulation began in the gas well. Finally, the liquid-loading depth of the gas well was estimated based on the bottomhole pressure. This method can be used to determine the fluid accumulation and calculate the liquid-loading depth of gas wells with unconnected oil jackets. The analysis revealed that in the Changbei gas field, condensate was the type of water primarily produced in 35 gas wells, accounting for 62.5% of the total number of gas wells. Edge-bottom water was the type of water primarily produced in 16 gas wells, accounting for 28.6% of the total number of gas wells. In the remainder of the gas wells, pore water was the water primarily produced; the calculations of accumulation time and accumulation volume of typical gas wells in the block revealed that some gas wells started to accumulate liquid after 45–50 months, and the amount of accumulation could reach several tens of meters, while others were in good production condition. The method established in this paper could enhance our understanding of liquid loading in gas wells in the Changbei gas field and lay a foundation for the development of gas-well deliquification techniques. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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Open AccessArticle

Analysis of the Flow Field at the Tip of an Axial Flow Compressor during Rotating Stall Process Based on the POD Method

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Processes 2023, 11(1), 69; https://doi.org/10.3390/pr11010069 - 27 Dec 2022

Cited by 1 | Viewed by 1360

Abstract

Rotating stalls are one of the most dangerous phenomena to be avoided in the designing and operating of axial flow compressors. An understanding of the evolution of the flow characteristics around the rotor tip region is important to study the process of stall [...] Read more.

Rotating stalls are one of the most dangerous phenomena to be avoided in the designing and operating of axial flow compressors. An understanding of the evolution of the flow characteristics around the rotor tip region is important to study the process of stall development. In this paper, some critical characteristics of the stall-related structures, which could not be observed by the traditional analysis methods, are understood by using the proper orthogonal decomposition (POD) method. The detailed unsteady flow fields in a typical transonic axial flow compressor during the stall process are obtained by the validated numerical simulation. Thereafter, the proper orthogonal decomposition method, as a method for model reduction and decomposition, is adopted to extract the flow characteristics from the numerical results of the stall process. It is found that the flow characteristics during the stall process can be well decomposed by the POD method. The pre-stall POD results show that the important flow features can be extracted and revealed in the low-order modes, which are not obvious in the original flow field. When the stall cells are formed and developed, the flow characteristics are gradually determined by the modes, which are related to the features of the stall cells. When the compressor is operated under stable stall conditions, the low-order POD modes are composed of a series of harmonic modes, which are sinusoid-like in space and time with the frequency of the stall cell rotation. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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Open AccessArticle

Velocity String Drainage Technology for Horizontal Gas Wells in Changbei

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Processes 2022, 10(12), 2640; https://doi.org/10.3390/pr10122640 - 08 Dec 2022

Cited by 1 | Viewed by 651

Abstract

The Changbei gas field is dominated by wells with large horizontal displacement, which have exhibited high gas production performance at an early stage of development. With the decrease in reservoir pressure, the liquid loading in the gas well is relatively high and gas [...] Read more.

The Changbei gas field is dominated by wells with large horizontal displacement, which have exhibited high gas production performance at an early stage of development. With the decrease in reservoir pressure, the liquid loading in the gas well is relatively high and gas production rapidly decreases. Therefore, suitable drainage measures are required to maintain stable gas production. Based on the characteristics of the unconnected oil jacket of gas wells in Changbei, a velocity string was used for drainage. A critical liquid-carrying model was established to determine the location of liquid loading in horizontal gas wells in Changbei. First, the coefficients of the liquid-carrying model were determined through theoretical analysis of the characteristics of the gas well formation. Then, the depth setting of the velocity string was analyzed. The critical liquid-carrying model was employed to calculate the liquid-carrying flow rate of each section; the calculated flow rates were compared with the actual flow rates to determine whether fluid accumulation occurred in each section of the gas well. Thereafter, with the help of the oil and casing position, the suitable setting position of the velocity string was determined. The formation fluid was driven from the tubing into the casing owing to the increase in the overflow area, based on the principle of reducer fluid mechanics. The fluid velocity in the larger overflow cross-section decreased, thereby reducing the drainage capacity of the gas well and resulting in liquid loading. Finally, a timing analysis was performed. After the formation pressure decreased, the well production and flow rate changes were analyzed by placing two velocity strings of different sizes at different wellhead pressures in the gas well with fluid accumulation. The results indicated that although the velocity string was set at a position suitable for fluid drainage, fluid accumulation still occurred after a production period, thus necessitating replacement deliquification. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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Open AccessArticle

Investigation on the Influence of Flow Passage Structure on the Performance of Bionic Pumps

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Processes 2022, 10(12), 2569; https://doi.org/10.3390/pr10122569 - 02 Dec 2022

Cited by 1 | Viewed by 695

Abstract

The flapping hydrofoil bionic pump drives the hydrofoil to make simple harmonic motion and completes one-way water pumping in the flow passage. As a new pump device that can realize ultra-low head water delivery, the flapping hydrofoil device can effectively enrich the drainage [...] Read more.

The flapping hydrofoil bionic pump drives the hydrofoil to make simple harmonic motion and completes one-way water pumping in the flow passage. As a new pump device that can realize ultra-low head water delivery, the flapping hydrofoil device can effectively enrich the drainage methods of plain rivers and improve water delivery efficiency, and the passage structure is the key factor of ultra-low head devices. In this paper, the two-dimensional flow passage models are established, and the flapping of the airfoil is realized by using the dynamic grid technology. Based on the continuity equation, k-ε turbulence model, and Reynolds time-averaged equation, the flapping hydrofoil device is simulated by transient calculation. The hydraulic performance characteristics of various passages with different widths, such as square passages, micro-arc passages, and convergent–divergent passages, are calculated and simulated. The results show that, under the fixed motion parameters, the narrower the passage width, the higher the outlet velocity, lift, and efficiency of the device, the lower the flow rate. The contraction–expansion pipe can effectively improve the efficiency and flow rate of the device, and, before the wake is stable, the longer the contraction section the better the lifting effect. However, the micro-arc pipeline will affect the formation of a double-row anti-Karman vortex street, resulting in greater energy loss and in its hydraulic performance being inferior to that of the square passage. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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Open AccessArticle

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

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Processes 2022, 10(11), 2398; https://doi.org/10.3390/pr10112398 - 14 Nov 2022

Cited by 1 | Viewed by 670

Abstract

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. [...] Read more.

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. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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Open AccessArticle

Investigation of Flow-Induced Noise Characteristics in the Oblique Flow Pump

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Processes 2022, 10(11), 2221; https://doi.org/10.3390/pr10112221 - 28 Oct 2022

Viewed by 549

Abstract

An oblique flow pump is widely used in farmland irrigation and drainage, water transfer projects, thermal power generation, and other fields. However, unstable flow factors in the oblique flow pump easily lead to pump vibration and noise. To improve the stability of pump [...] Read more.

An oblique flow pump is widely used in farmland irrigation and drainage, water transfer projects, thermal power generation, and other fields. However, unstable flow factors in the oblique flow pump easily lead to pump vibration and noise. To improve the stability of pump operation and optimize the operating environment, it is necessary to study the flow-induced noise characteristics of oblique flow pumps. In this paper, CFD and noise simulation software are used to calculate the flow field and sound field of the oblique flow pump. The internal flow characteristics and flow-induced noise characteristics of the oblique flow pump were studied. The results show that when the flow rate of the oblique flow pump deviates from the optimal operating point, especially in the small flow rate, due to the phenomena of backflow and flow separation, more high-energy vortices are produced in the flow channel, and the vortices are distributed in a wide area, which will cause greater flow-induced noise. It is found that with the increase in flow rate, the sound pressure level of flow noise in the inlet channel gradually decreases, the sound pressure level in the guide vane region first decreases and then increases, and the sound pressure level is the lowest at 1.0Q. Generally speaking, the noise sound pressure level in the outlet channel region of the pump also gradually decreases. In addition, at the blade frequency, the radiated noise of the oblique flow pump can show dipole characteristics under various flow conditions, and the radiation level of sound pressure increases with the increase in flow rate. This paper can provide a theoretical basis for the mechanism research and control strategy of flow-induced noise in oblique flow pumps. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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Open AccessFeature PaperArticle

Entropy Production Evaluation within a Prototype Pump-Turbine Operated in Pump Mode for a Wide Range of Flow Conditions

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Processes 2022, 10(10), 2058; https://doi.org/10.3390/pr10102058 - 12 Oct 2022

Cited by 1 | Viewed by 671

Abstract

Inside the pump-turbine, energy is irreversibly lost due to turbulent pulsations in the high Reynolds number zone and actions of viscous forces close to the wall. The conventional differential pressure method cannot obtain specific details of the hydraulic loss within the machine’s flow [...] Read more.

Inside the pump-turbine, energy is irreversibly lost due to turbulent pulsations in the high Reynolds number zone and actions of viscous forces close to the wall. The conventional differential pressure method cannot obtain specific details of the hydraulic loss within the machine’s flow passages; on the other hand, the entropy production method can provide accurate information on the location of irreversible losses and the spatial distribution of energy dissipation. Therefore, based on the entropy production theory, this study investigates the composition and distribution of hydraulic losses under different flow conditions for a prototype pump-turbine in pump mode. Study results indicated that total hydraulic losses significantly decreased, then slowly increased with an increase in flow rate. The entropy production rate caused by turbulence dissipation (EPTD), direct dissipation (EPDD), and wall shear stress (EPWS) displayed the same variation patterns as that of total hydraulic losses, with EPTD and EPDD being the most dominating. The location of hydraulic loss within the pump-turbine’s flow domain strongly depended on flow conditions. High hydraulic losses primarily occurred in the guide vanes (GV) and draft tube under low flow rates. Under high flow conditions, however, high hydraulic losses were mostly concentrated in the stay vanes (SV), spiral casing, and GV. Hydraulic losses at low flow rates were primarily caused by flow separation within the GV flow channels, vortices in the vaneless region, and inlet flow impacts on the runner blade’s leading edge. On the other hand, large vortices within the GV and SV flow channels, GV wake flow, and unsteady flow at the spiral casing were the main contributors to hydraulic loss under high flow conditions. EPDD was mainly caused by strain rate, so it was closer to the main vortex regions, whereas EPTD was affected by turbulence intensity and had a wider distribution range in the unsteady flow. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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Open AccessArticle

Transient Characteristics of Three-Dimensional Flow in a Centrifugal Impeller Perturbed by Simple Pre-Swirl Inflow

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Ze Wang

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Wei Zhang

Processes 2022, 10(10), 2007; https://doi.org/10.3390/pr10102007 - 05 Oct 2022

Viewed by 704

Abstract

The pre-swirl inflow generated by guide vanes could improve the hydrodynamic performances of centrifugal pumps as long as the inflow matches the patterns of internal flow of the impeller. In this work, we present a numerical investigation on the internal flow in a [...] Read more.

The pre-swirl inflow generated by guide vanes could improve the hydrodynamic performances of centrifugal pumps as long as the inflow matches the patterns of internal flow of the impeller. In this work, we present a numerical investigation on the internal flow in a centrifugal impeller subjected to inflow artificially constructed with simple pre-swirling; unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations are performed at the designed flow rate with five values of rotating velocity of the inflow, i.e., U_rot/U_ref = −0.5, −0.3, 0.0, 0.3 and 0.5, where U_rot and U_ref denote the rotating and normal velocity component at the entrance of the inflow tube, respectively. The primary objective of this work is to reveal the three-dimensional characteristics of internal flow of the impeller as influenced by the superimposed pre-swirl inflow, and to identify the propagation of inflow within the impeller. The numerical data are presented and analyzed in terms of the streamline fields, the distributions of various velocity components along the circumferential and axial directions, the pressure distribution and limiting streamlines on the surfaces of a blade. Numerical results reveal that separation occurs around the leading edge of the blades and occasionally at the trailing edge, and the internal flow is more uniform in the central region of the channels. A noticeable fluctuation of both radial and circumferential velocities is observed at the outlet of the impeller as it is subjected to counter-rotating inflow, and the greatest fluctuation is close to the hub instead of the middle channel and shroud as for the co-rotating inflow. The boundary layer flow of suction surface is more sensitive to the inflow; occasional small-scale separation bubble occurs on the suction surface around the leading edge for some blades, and reattachment of separated flow is reduced for the counter-rotating inflow. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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Open AccessArticle

The Optimal Operation of Parallel Pumping Stations for Inter-Basin Water Transfer Based on the Multi-Objective Optimization of a Single Pumping Station

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Yi Gong

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Bowen Zhu

Processes 2022, 10(10), 1935; https://doi.org/10.3390/pr10101935 - 26 Sep 2022

Cited by 2 | Viewed by 739

Abstract

A nonlinear mathematical model for the optimal operation of a parallel pumping station group was established with the objective of minimizing the operation costs of the station group considering the target quantity of water extraction and flow unevenness between units of each station [...] Read more.

A nonlinear mathematical model for the optimal operation of a parallel pumping station group was established with the objective of minimizing the operation costs of the station group considering the target quantity of water extraction and flow unevenness between units of each station as constraints. The original model is decomposed into several sub-models with a single station multi-objective optimization operation with the target water lifting capacity of a single pump station as the coordinating variable. This constructed model was solved using a large-scale system decomposition dynamic programming aggregation method based on sub-system multi-objective genetic algorithm optimization. Taking the Jiangdu parallel pumping station group in the Chinese East Route of the South-to-North Water Diversion Project as a case study, the results show that under the condition of 80% water lifting load of parallel stations and 7.8 m daily average lift, the unit water lifting cost of the optimal operation of each station decreases by 4.81%, 4.81%, 19.83% and 11.06% compared with the constant speed operation at the specified angle. The unevenness of the flow of each station is 2.16 m³/s, 2.16 m³/s, 0.60 m³/s and 14.10 m³/s. The erosion of the outlet pool is small. This article provides theoretical reference for the optimal operation of the same type of large-scale inter-basin water transfer parallel pumping station groups. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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Open AccessArticle

Design and Development of Explosion-Proof Cavity of Hydraulic System Power Unit Applied in Explosion-Proof Area

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Processes 2022, 10(9), 1824; https://doi.org/10.3390/pr10091824 - 09 Sep 2022

Viewed by 894

Abstract

The construction machinery and vehicles, especially the explosion-proof and explosion-isolation ability of the vehicles are playing an increasingly important role in the complex and unpredictable emergency rescue field. In this paper, the explosion-proof housing of hydraulic system power unit applied in engineering machinery [...] Read more.

The construction machinery and vehicles, especially the explosion-proof and explosion-isolation ability of the vehicles are playing an increasingly important role in the complex and unpredictable emergency rescue field. In this paper, the explosion-proof housing of hydraulic system power unit applied in engineering machinery is investigated, wherein the power unit includes motor, power supply and control element. Motor-driven hydraulic pump provides the necessary power for the hydraulic system. The gas explosion process, basic parameters, flame acceleration mechanism and the theory model of gas explosion in finite space are analyzed. Relevant mathematical models of the experimental gas explosion for explosion-proof cavity are established. Furthermore, the models are analyzed by numerical method. We simulate the dynamic process of explosion by software. The analysis, examination and simulation of structural strength are conducted on the explosion-proof cavity according to the maximum explosion pressure obtained from the simulation results. The reasonable design parameters satisfying the explosion-proof requirements are obtained. The explosion-proof cavity which is processed according to the design parameters is tested. The explosion-proof performance is verified by analyzing the experimental results. According to the test standard, the impact test, thermal test, pressure test, overpressure test and propagation test under internal ignition for the cavity are conducted. The results show that the pressure test coincides with the simulation results. The remaining test results also satisfy the experimental purpose. The reasonableness of the design of the explosion-proof cavity is verified, which can meet the actual requirements of the equipment. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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Review of Flow-Matching Technology for Hydraulic Systems

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Processes 2022, 10(12), 2482; https://doi.org/10.3390/pr10122482 - 23 Nov 2022

Cited by 2 | Viewed by 1268

Abstract

The flow-matching problem of hydraulic systems is an important factor affecting the working performance and energy saving of hydraulic systems. According to the different flow-matching mechanisms, the flow-matching technology of hydraulic systems can be divided into three categories: positive flow-control technology, negative flow-control [...] Read more.

The flow-matching problem of hydraulic systems is an important factor affecting the working performance and energy saving of hydraulic systems. According to the different flow-matching mechanisms, the flow-matching technology of hydraulic systems can be divided into three categories: positive flow-control technology, negative flow-control technology, and load-sensitive control technology. In this paper, the working mechanism of flow-matching technology and the cause of energy loss are analyzed, and the research results of flow matching are introduced from two aspects of energy saving and consumption reduction and system performance improvement. In the direction of energy saving and consumption reduction, the purposes of energy saving and consumption reduction are achieved by means of multi-way valve commutation, independent inlet and outlet control, parallel replacement of shuttle valve by a cylinder piston rod controlled by pilot pressure, change of hydraulic resistance of a pressure compensating valve, improvement of the power regulation range of a hydraulic pump, and potential energy recovery. In the direction of system performance, by means of flow-forecasting system pressure change, applying flow unsaturation real-time control idea, and combining electronic control technology with load-sensitive technology, the pressure drop during transmission process and the transmission signal lag are reduced, the speed regulation interval is enlarged, fine-tuning characteristics are improved, and the response speed is increased. The research results indicate that improving the structure and the control strategy of hydraulic systems and improving the flow-matching degree of a system to achieve global matching will be a future development trend. Full article

(This article belongs to the Special Issue Advanced Simulation and Experiment Methods of Flow Instability in Hydraulic Machinery)

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