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21 pages, 19174 KiB

Open AccessArticle

A Parameter Sensitivity Analysis of Hydropower Units under Full Operating Conditions Considering Turbine Nonlinearity

by Dong Liu, Xinxu Wei, Jingjing Zhang, Xiao Hu and Lihong Zhang

Sustainability 2023, 15(15), 11691; https://doi.org/10.3390/su151511691 - 28 Jul 2023

Cited by 1 | Viewed by 1147

Abstract

A parameter sensitivity analysis is an important part of the stability study of hydro turbine regulation systems, which helps operators to deepen their understanding of the characteristics and connections among the various parts of these systems. Considering that large hydropower stations undertake an [...] Read more.

A parameter sensitivity analysis is an important part of the stability study of hydro turbine regulation systems, which helps operators to deepen their understanding of the characteristics and connections among the various parts of these systems. Considering that large hydropower stations undertake an essential regulation task in the power grid, the safety and stability of their operation cannot be ignored. To this end, taking a unit in a giant hydropower station in China as an example, a hydraulic–mechanical–electrical coupling model of the hydraulic turbine regulation system is established. A comprehensive parameter sensitivity indicator and parameter sensitivity analysis framework are proposed. On this basis, the sensitivity of the main system variables to parameter changes under full operating conditions is investigated by considering two different control modes of the unit (i.e., corresponding to different grid types). The results show that the sensitivity of the system state to the mechanical parameters of the generator is the highest in the power control mode, while the sensitivity to the electrical parameters of the generator and excitation system is higher in the frequency control mode. The sensitivity of the system with these key parameters also shows different patterns of change with a change in the unit operating conditions. The relevant findings can provide some theoretical guidance for the operation of hydropower stations and help to reduce the risk of system instability. Full article

(This article belongs to the Special Issue Ocean and Hydropower)

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17 pages, 5601 KiB

Open AccessArticle

Numerical Study of the Internal Fluid Dynamics of Draft Tube in Seawater Pumped Storage Hydropower Plant

by Jianyong Hu, Qingbo Wang, Zhenzhu Meng, Hongge Song, Bowen Chen and Hui Shen

Sustainability 2023, 15(10), 8327; https://doi.org/10.3390/su15108327 - 19 May 2023

Cited by 3 | Viewed by 1449

Abstract

Pumped storage hydropower plants are renewable energy systems that are effective in saving energy and solving electricity peak-on shortage. Seawater pumped storage hydropower plants are a novel type of pumped storage hydropower plant specifically supplying electric power for ocean islands with the support [...] Read more.

Pumped storage hydropower plants are renewable energy systems that are effective in saving energy and solving electricity peak-on shortage. Seawater pumped storage hydropower plants are a novel type of pumped storage hydropower plant specifically supplying electric power for ocean islands with the support of solar energy and wind energy. Compared with traditional pumped storage hydropower plants that are constructed on the mainland, seawater pumped storage hydropower plants should take the influence of the complex marine environment, such as extreme waves and winds, into consideration. Taking the characteristics of waves near islands in the East China Sea as an example, we explored the transient hydraulic characteristics in the draft tube of a pump turbine under wave disturbance using a sliding grid interface and the detached eddy simulation (DES) turbulence model. By analyzing the characteristics of unsteady flow in the draft tube, the vortex characteristics under the Q criterion, the frequency characteristics of the pressure pulsation, the evolution law of the internal fluid, and the propagation law of the pressure pulsation were explored. For the situation without wave disturbance, an obvious eccentric vortex in the straight cone section of the draft tube was observed in the case where the opening of the guide vane was small. With the increase in the opening of the guide vane, the eccentric vortex gradually dissipated. For the situation with wave disturbance, the main frequency of the draft tube equaled the frequency of the wave disturbance, the maximum pressure pulsation at the selected monitoring points increased 5 to 15 times, and the superposition of the wave pressure pulsation signals and the draft tube pressure pulsation produced more low-frequency, high-amplitude pressure pulsation signals. Even though the pressure pulsation frequency spectrum varied a lot, the frequency domain of the pressure pulsation without wave disturbance still existed. In addition, the wave disturbance merely varied with the pressure of the draft tube. The influence of wave disturbance on the pressure distribution in the draft tube was relatively small. The results can provide a reference for the operation of seawater pumped storage hydropower plants. Full article

(This article belongs to the Special Issue Ocean and Hydropower)

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18 pages, 10288 KiB

Open AccessArticle

Design and Test for a New Type of Permanent Magnet Synchronous Generator Applied in Tidal Current Energy System

by Yuxiang Zhao, Caixia Mo, Wanqiang Zhu, Jianmei Chen, Baigong Wu, Xiao Zhang, Xueming Zhang and Liwei Chen

Sustainability 2023, 15(9), 7378; https://doi.org/10.3390/su15097378 - 28 Apr 2023

Cited by 1 | Viewed by 1873

Abstract

This article takes a 120 W direct-drive permanent magnet synchronous generator (PMSG) for tidal current energy as the research object, with the aim of starting at low flow velocity, low voltage regulation, and high sealing performance. The research was conducted on the design [...] Read more.

This article takes a 120 W direct-drive permanent magnet synchronous generator (PMSG) for tidal current energy as the research object, with the aim of starting at low flow velocity, low voltage regulation, and high sealing performance. The research was conducted on the design method of the generator, and the parameter calculation formula is modified based on the structural characteristics of the generator. The design scheme is simulated using the finite element method, and the voltage regulation is optimized using evolutionary algorithm. A prototype was manufactured based on the optimized scheme, and drag experiments and sealing tests were conducted. After that, the generator and impeller were assembled, and water tank drag experiments were conducted. The experimental results verified the reliability of the motor design method in this paper. Full article

(This article belongs to the Special Issue Ocean and Hydropower)

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14 pages, 1790 KiB

Open AccessArticle

Comparative Evaluation of the Immersed-Solid Method for Simulating the Flow Field around Hydrofoil

by Zilong Hu, Di Zhu, Ruofu Xiao and Ran Tao

Sustainability 2023, 15(4), 3493; https://doi.org/10.3390/su15043493 - 14 Feb 2023

Cited by 4 | Viewed by 1851

Abstract

The wall boundary is important in computational-fluid-dynamics simulations. If extremely small leakage, changing leakage or a moving body exists in the simulation case, the difficulty in meshing and solving near-wall flow increases. The immersed-solid method, which inserts a rigid, solid body into the [...] Read more.

The wall boundary is important in computational-fluid-dynamics simulations. If extremely small leakage, changing leakage or a moving body exists in the simulation case, the difficulty in meshing and solving near-wall flow increases. The immersed-solid method, which inserts a rigid, solid body into the entire fluid domain, was a choice to solve the wall-boundary-solution problems mentioned above, without considering mesh deformation. The purpose of this paper is to verify the effectiveness of the immersed-solid method in the simulation of extremely small leakage, changing leakage or a moving body, and to provide a theoretical basis for the use of the submerged-solid method in engineering. In this study, the NACA0015 hydrofoil was used to check the hydrodynamic characteristics in using the immersed-solid method. The comparative study was conducted at the incidence angle of 8 degrees and a Reynolds number of 5.0 × 10⁵, by using the immersed-solid and traditional no-slip-wall boundary. The results show that the flow striking and separation with pressure rise and drop can be correctly captured using an immersed-solid setup with boundary tracking. However, the accuracy of pressure and velocity field using the immersed-solid method was insufficient. The turbulence-kinetic energy was much higher around the immersed-solid foil body. Generally, the immersed-solid method can qualitatively predict the correct hydrodynamic characteristics. Its convergence ability is better, and it can save approximately 20% of CPU time, even if the grid density is 4.39 times of the traditional no-slip wall. Therefore, the immersed-solid method can be a good choice for engineering-flow cases with complex wall problems. Full article

(This article belongs to the Special Issue Ocean and Hydropower)

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23 pages, 8933 KiB

Open AccessArticle

Finite Element Analysis of Different Infill Patterns for 3D Printed Tidal Turbine Blade

by Glecelyn M. Galvez, Karl Andrie M. Olivar, Francis Rey G. Tolentino, Louis Angelo M. Danao and Binoe E. Abuan

Sustainability 2023, 15(1), 713; https://doi.org/10.3390/su15010713 - 30 Dec 2022

Cited by 4 | Viewed by 3562

Abstract

The fabrication route for tidal turbine blades has been compounded with the appearance of additive manufacturing; with the use of infill patterns, improvement of mechanical strength and material reduction for 3D printed parts can be obtained. Through finite element analysis and three-point bend [...] Read more.

The fabrication route for tidal turbine blades has been compounded with the appearance of additive manufacturing; with the use of infill patterns, improvement of mechanical strength and material reduction for 3D printed parts can be obtained. Through finite element analysis and three-point bend tests, the optimal infill lattice pattern, and the viability of the shell–infill turbine blade model as an alternative to the conventional shell-spar model was determined. Out of a selection of infills, the best infill pattern was determined as the hexagonal infill pattern oriented in-plane. A representative volume element was modeled in ANSYS Material Designer, resulting in the homogenized properties of the in-plane hexagonal lattice. After validation, the homogenized properties were applied to the tidal turbine blade. The shell–infill model was based on the volume of the final shell-spar model which had a blade deflection of 9.720% of the blade length. The difference in the deflection between the homogenized infill and the spar cross-section was 0.00125% with a maximum stress of 170.3 MPa which was within the tensile strength and flexure strength of the carbon fiber with onyx base material. Conclusively, the homogenized infill was determined as a suitable alternative to the spar cross-section. The best orientation of the infill relative to the horizontal orientation of the blade was 0 degrees; however, the lack of trend made it inconclusive whether 0 degrees was the absolute optimal infill orientation. Full article

(This article belongs to the Special Issue Ocean and Hydropower)

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25 pages, 3315 KiB

Open AccessArticle

Estimating Future Costs of Emerging Wave Energy Technologies

by Pablo Ruiz-Minguela, Donald R. Noble, Vincenzo Nava, Shona Pennock, Jesus M. Blanco and Henry Jeffrey

Sustainability 2023, 15(1), 215; https://doi.org/10.3390/su15010215 - 23 Dec 2022

Cited by 7 | Viewed by 3179

Abstract

The development of new renewable energy technologies is generally perceived as a critical factor in the fight against climate change. However, significant difficulties arise when estimating the future performance and costs of nascent technologies such as wave energy. Robust methods to estimate the [...] Read more.

The development of new renewable energy technologies is generally perceived as a critical factor in the fight against climate change. However, significant difficulties arise when estimating the future performance and costs of nascent technologies such as wave energy. Robust methods to estimate the commercial costs that emerging technologies may reach in the future are needed to inform decision-making. The aim of this paper is to increase the clarity, consistency, and utility of future cost estimates for emerging wave energy technologies. It proposes a novel three-step method: (1) using a combination of existing bottom-up and top-down approaches to derive the current cost breakdown; (2) assigning uncertainty ranges, depending on the estimation reliability then used, to derive the first-of-a-kind cost of the commercial technology; and (3) applying component-based learning rates to produce the LCOE of a mature technology using the upper bound from (2) to account for optimism bias. This novel method counters the human propensity toward over-optimism. Compared with state-of-the-art direct estimation approaches, it provides a tool that can be used to explore uncertainties and focus attention on the accuracy of cost estimates and potential learning from the early stage of technology development. Moreover, this approach delivers useful information to identify remaining technology challenges, concentrate innovation efforts, and collect evidence through testing activities. Full article

(This article belongs to the Special Issue Ocean and Hydropower)

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15 pages, 4634 KiB

Open AccessArticle

Numerical Analysis and Experimental Study of Unsteady Flow Characteristics in an Ultra-Low Specific Speed Centrifugal Pump

by Yangyang Wei, Yuhui Shi, Weidong Shi and Bo Pan

Sustainability 2022, 14(24), 16909; https://doi.org/10.3390/su142416909 - 16 Dec 2022

Cited by 3 | Viewed by 1928

Abstract

Low specific speed centrifugal pumps are widely used in urban water supply, agricultural irrigation, petrochemical and other fields due to their small flow rate and high head. Therefore, the study of unsteady flow characteristics plays a vital role in its safe and stable [...] Read more.

Low specific speed centrifugal pumps are widely used in urban water supply, agricultural irrigation, petrochemical and other fields due to their small flow rate and high head. Therefore, the study of unsteady flow characteristics plays a vital role in its safe and stable operation. In this paper, numerical simulation and experimental methods are used to explore the unsteady performance of the pump. The results show that the fluctuations of the external characteristic such as head, shaft power and energy loss are due to the periodic disturbance of the flow field of pump. But the transient performance of shaft power and head shows different changing trends due to different influencing factors. In this paper, the transient process of hydraulic performance is divided into three stages according to the causes and characteristics of hydraulic fluctuations. Most of the hydraulic losses occur inside the impeller, so the impeller flow field determines the level of time average hydraulic performance. Although the hydraulic loss of the spiral case is small, it is greatly affected by the rotor-stator interaction, which affects the strength of the hydraulic fluctuation. This study is of great significance to the mechanism of rotor-stator interaction and the stable operation of low specific speed centrifugal pumps. Full article

(This article belongs to the Special Issue Ocean and Hydropower)

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17 pages, 7312 KiB

Open AccessArticle

The Effects of Meridian Surface Shape on the Pressure Pulsation of a Multi-Stage Electric Submersible Pump

by Danyang Du, Yong Han, Yu Xiao, Lu Yang and Xuanwei Shi

Sustainability 2022, 14(22), 14950; https://doi.org/10.3390/su142214950 - 11 Nov 2022

Viewed by 1278

Abstract

The influence mechanism of the internal pressure fluctuation propagation law of multi-stage submersible electric pump (ESP) is still unclear, which has been a major problem restricting the stable exploitation of deep-sea oil and gas. In order to investigate the effect of different meridian [...] Read more.

The influence mechanism of the internal pressure fluctuation propagation law of multi-stage submersible electric pump (ESP) is still unclear, which has been a major problem restricting the stable exploitation of deep-sea oil and gas. In order to investigate the effect of different meridian profiles on the pressure pulsation characteristics of three-stage submersible electric pumps, the unsteady Reynolds-averaged Navier–Stokes (URANS) method is used to numerically investigate it. The results show that the lower the pressure pulsation amplitude in the pump caused by the meridional shape that is more in line with the flow law, has a positive effect on the operation stability. The change of the shape of the meridian greatly affects the pressure pulsation law in the secondary and final pumps. The rotor–stator interaction causes the pressure pulsation amplitude of the monitoring point in the middle of the pump chamber to reach a peak value. By using continuous wavelet transform analysis, it is found that the regularity of 1–2 times frequency conversion is complicated due to multiple pulsation sources and low frequency propagation coupling between stages. At 3–6 times frequency, it is basically close to the pulsation rule of the blade frequency. The above research provides a basis for improving the operation stability of the ESP. Full article

(This article belongs to the Special Issue Ocean and Hydropower)

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18 pages, 3282 KiB

Open AccessArticle

Effect of Mooring Parameters on Dynamic Responses of a Semi-Submersible Floating Offshore Wind Turbine

by Baolong Liu and Jianxing Yu

Sustainability 2022, 14(21), 14012; https://doi.org/10.3390/su142114012 - 27 Oct 2022

Cited by 4 | Viewed by 2423

Abstract

Based on a new semi-submersible floating offshore wind turbine (FOWT), a coupling aero-hydro-flexible model was established to study its dynamic behaviors, as well as the corresponding mooring system, under complicated sea scenarios. The aerodynamic load, the wave load, the current load, and the [...] Read more.

Based on a new semi-submersible floating offshore wind turbine (FOWT), a coupling aero-hydro-flexible model was established to study its dynamic behaviors, as well as the corresponding mooring system, under complicated sea scenarios. The aerodynamic load, the wave load, the current load, and the mooring load were taken into consideration. To further investigate the influence of the mooring parameters on the floating system, the diameter and the total length of mooring lines, which are the most critical parameters in mooring line design, were chosen to be analyzed. Particularly, five diameters and seven lengths were adopted to establish the FOWT mooring system, and a time-domain simulation was carried out for each cases. Based on the numerical simulations, their influences on the mooring system stiffness and the dynamic responses of FOWT were studied. The results show that the diameter has little influence on the static shape of the mooring line. The mooring system stiffness can be effectively increased by reducing the length and increasing the diameter of mooring lines. Moreover, the surge motion of floating foundation can be effectively controlled by increasing the mooring line diameter and decreasing mooring line length under the rated sea scenario. From this aspect, the dynamic response features of the FOWTs could be improved. Full article

(This article belongs to the Special Issue Ocean and Hydropower)

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17 pages, 8440 KiB

Open AccessArticle

Turbulence Characteristics in the Mixing Layer of a Submerged Cavitating Jet at High Reynolds Numbers

by Yongfei Yang, Gaowei Wang, Weidong Shi, Wei Li, Leilei Ji and Hongliang Wang

Sustainability 2022, 14(19), 11963; https://doi.org/10.3390/su141911963 - 22 Sep 2022

Cited by 5 | Viewed by 1457

Abstract

In this paper, unsteady and time-averaged turbulence characteristics in a submerged cavitating jet with a high Reynolds number are studied using large eddy simulation. The simulation is validated by comparing the vapor distribution using CFD and a high-speed photography experiment. The results indicate [...] Read more.

In this paper, unsteady and time-averaged turbulence characteristics in a submerged cavitating jet with a high Reynolds number are studied using large eddy simulation. The simulation is validated by comparing the vapor distribution using CFD and a high-speed photography experiment. The results indicate that the currently used numerical method can predict the evolution of the cavitation cloud in the jet accurately. The instantaneous and time-averaged flow fields of the submerged jet with three different cavitation numbers are studied. Comparing the frequency spectral of jets with different cavitation numbers, it is found that, for a fixed location, the frequency increases with the decrease in the cavitation number. Comparing the vorticity distribution at different streamwise locations, the instability process of the ring-shapes vortexes is revealed. Comparing the shape of the cavitation cloud and the vortexes in the jet finds that their spatial distribution and the temporal evolution are similar, indicating that the dynamic characteristics of the vortex and the cavitation affect each other. For the currently investigated cavitating jets, the Reynolds number increases with the decrease in the cavitation number. However, the spreading rate is lower for the jet with higher Reynolds numbers here. This is means that the momentum exchange between the jet and submerging water is reduced by the cavitation phenomenon. Full article

(This article belongs to the Special Issue Ocean and Hydropower)

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16 pages, 4350 KiB

Open AccessArticle

Hydraulic Oscillation Analysis of the Hydropower Station with an Equivalent Circuit-Based Hydraulic Impedance Scheme

by Shuangqing Yan, Yang Zheng, Jinbao Chen and Yousong Shi

Sustainability 2022, 14(18), 11410; https://doi.org/10.3390/su141811410 - 12 Sep 2022

Cited by 4 | Viewed by 1633

Abstract

The concept of hydraulic impedance is widely used for periodic or oscillating flow scenarios in applied hydraulic transients. This paper proposes an equivalent circuit-based discrete hydraulic impedance model for the hydraulic system of the power station. The equivalent hydraulic circuit is established by [...] Read more.

The concept of hydraulic impedance is widely used for periodic or oscillating flow scenarios in applied hydraulic transients. This paper proposes an equivalent circuit-based discrete hydraulic impedance model for the hydraulic system of the power station. The equivalent hydraulic circuit is established by an analogy between the water hammer wave propagation in pressurized pipes and the electromagnetic wave propagation in conductors. The discrete hydraulic impedance at a given location is obtained by calculating the total specific impedance of the series and parallel circuits from one end to the other. In addition, the numerical solution process to obtain the natural frequencies of the system via the proposed model is designed in detail. Furthermore, oscillation characteristics of the pipelines in the hydropower station are investigated. The variation trends of the decay coefficients of different orders of oscillation of the system and the influence of turbine impedance on the oscillation frequencies are discussed, respectively. Full article

(This article belongs to the Special Issue Ocean and Hydropower)

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15 pages, 3465 KiB

Open AccessArticle

Improved Neural Network Algorithm Based Flow Characteristic Curve Fitting for Hydraulic Turbines

by Hong Pan, Chenyang Hang, Fang Feng, Yuan Zheng and Fang Li

Sustainability 2022, 14(17), 10757; https://doi.org/10.3390/su141710757 - 29 Aug 2022

Cited by 5 | Viewed by 1424

Abstract

One of the most important characteristic curves in the economic operation of hydropower plants is the turbine flow characteristic curve, which illustrates the law of fluctuation between the characteristic parameters of the turbine under various operating situations. This article proposes an IPSO-LSTM-based refinement [...] Read more.

One of the most important characteristic curves in the economic operation of hydropower plants is the turbine flow characteristic curve, which illustrates the law of fluctuation between the characteristic parameters of the turbine under various operating situations. This article proposes an IPSO-LSTM-based refinement method for fitting the turbine flow characteristic curve using deep learning methods, and verifies the effectiveness of the method by comparison to solve the problem that traditional mathematical fitting methods are difficult to meet the requirements of today’s many complex working conditions. Firstly, a deep LSTM network model is established based on the input and output quantities, and then the IPSO method is used to find the optimum number of neurons, the learning rate and the maximum number of iterations of the LSTM units in the network model and other key parameters to determine the relevant training parameters. The results show that the model can effectively improve the accuracy of fitting and predicting the turbine flow characteristics, which is of great significance to the study of the economic operation of hydropower plants and the non-linear characteristics of the turbine. Full article

(This article belongs to the Special Issue Ocean and Hydropower)

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30 pages, 10657 KiB

Open AccessArticle

Multi-Objective Optimization of Back-to-Back Starting for Pumped Storage Plants under Low Water Head Conditions Based on the Refined Model

by Chen Feng, Guilin Li, Yuan Zheng, Daqing Zhou and Zijun Mai

Sustainability 2022, 14(16), 10289; https://doi.org/10.3390/su141610289 - 18 Aug 2022

Cited by 2 | Viewed by 1667

Abstract

Pumped storage plants (PSP) must switch frequently between various working conditions. Moreover, PSPs can fall easily into an S-shaped zone under low water head conditions, especially during back-to-back starting (BTBS), which reduces the stability and safety of unit operation. In this paper, a [...] Read more.

Pumped storage plants (PSP) must switch frequently between various working conditions. Moreover, PSPs can fall easily into an S-shaped zone under low water head conditions, especially during back-to-back starting (BTBS), which reduces the stability and safety of unit operation. In this paper, a nonlinear PSP model for BTBS is established by combining an electrical subsystem with a refined hydraulic-mechanical subsystem. The influences of the hydraulic, mechanical, and electrical factors on the BTBS process are investigated quantitatively. Choosing the speed overshoot and speed stable time as the optimization objectives, and considering a variety of constraints, the multi-objective particle swarm optimization (MOPSO) algorithm is introduced to study and optimize two typical startup strategies. The results show that: (1) The parameters of a hydraulic-mechanical-electrical system have a significant impact on BTBS process, and the most unfavorable working condition corresponds to the lowest water head; (2) In the control schemes, a novel constant excitation voltage strategy is proposed based on the multi-objective optimization scheme. Compared with the constant excitation current strategy or single-objective, the optimization strategy proposed can considerably improve the speed overshoot and the speed stable time by at least 68.27% and 3.22% under the worst working conditions. (3) It is further verified that the problem of trapping in the S-shaped region under various working conditions may be avoided by the obtained optimal control scheme. The results give prominence to the effectiveness of the proposed optimization strategy for maintaining the safety and stabilization of PSP operation. Full article

(This article belongs to the Special Issue Ocean and Hydropower)

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20 pages, 4208 KiB

Open AccessArticle

Optimal Configuration of Electrochemical Energy Storage for Renewable Energy Accommodation Based on Operation Strategy of Pumped Storage Hydro

by Linjun Shi, Fan Yang, Yang Li, Tao Zheng, Feng Wu and Kwang Y. Lee

Sustainability 2022, 14(15), 9713; https://doi.org/10.3390/su14159713 - 7 Aug 2022

Cited by 3 | Viewed by 1632

Abstract

Due to the volatility of renewable energy resources (RES) and the lag of power grid construction, grid integration of large-scale RES will lead to the curtailment of wind and photovoltaic power. Pumped storage hydro (PSH) and electrochemical energy storage (EES), as common energy [...] Read more.

Due to the volatility of renewable energy resources (RES) and the lag of power grid construction, grid integration of large-scale RES will lead to the curtailment of wind and photovoltaic power. Pumped storage hydro (PSH) and electrochemical energy storage (EES), as common energy storage, have unique advantages in accommodating renewable energy. This paper studies the optimal configuration of EES considering the optimal operation strategy of PSH, reducing the curtailment of wind and photovoltaic power in the power grid through the cooperative work of PSH and EES. First, based on the curtailment of RES, with the goal of improving the accommodation of RES, a combined operation optimization model of PSH and EES is proposed. Then, an optimal configuration method of EES capacity is proposed to meet the power curtailment rate in the power grid. Finally, the simulation is carried out in the actual power grid and the CPLEX solver is used to solve the optimization, and the rationality and economy of the optimization are analyzed and discussed. The simulation results show that, based on the combined operation of PSH and EES, by rationally configuring the capacity of EES, the desired power curtailment rate of the power grid can be achieved, and the necessity of configuring variable speed units is verified. Full article

(This article belongs to the Special Issue Ocean and Hydropower)

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13 pages, 5240 KiB

Open AccessArticle

Research on Flow Field Characteristics in Water Jet Nozzle and Surface Damage Caused by Target Impact

by Qinghong Zhang, Zhouhao Shi, Weidong Shi, Zhanshan Xie, Linwei Tan and Yongfei Yang

Sustainability 2022, 14(15), 9074; https://doi.org/10.3390/su14159074 - 25 Jul 2022

Cited by 6 | Viewed by 1988

Abstract

As a new processing method, water jet processing technology has risen rapidly due to its wide range of applications, no pollution, and zero discharge. In this paper, the flow characteristics and failure characteristics of ultra-high-pressure gas-liquid jet in the range of 300 MPa [...] Read more.

As a new processing method, water jet processing technology has risen rapidly due to its wide range of applications, no pollution, and zero discharge. In this paper, the flow characteristics and failure characteristics of ultra-high-pressure gas-liquid jet in the range of 300 MPa are analyzed by numerical calculation. The research conclusion shows that the jet atomization diffusion is caused by the friction between the liquid medium and the surrounding gas, the mixed flow of broken water droplets and cavitation. The jet diffusion process is essentially the energy exchange process between the jet in the core area and the turbulent flow in the atomization area. The distribution of the turbulent kinetic energy in the atomization area can determine the degree of jet diffusion and the rate of energy decay. The water jet impacted the surface of the target to form a crater-like annular erosion pit. With the increase of the impact pressure, the deformation showed an overall increasing trend, and the increasing trend increased significantly. The central depression of the erosion area is caused by the damage of the material by the stagnation pressure in the core area. The flow characteristics of gas-liquid flow in the process of formation and diffusion in the high-pressure water jet nozzle are explored from the microscopic point of view, and it also provides a theoretical basis for equipment optimization in engineering. Full article

(This article belongs to the Special Issue Ocean and Hydropower)

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10 pages, 3424 KiB

Open AccessTechnical Note

Variation Characteristics of Hydrodynamic Coefficients of Two-Dimensional Rectangular Moonpool Resonance under Sway Motion

by Zhouhao Zhang, Hongsheng Zhang, Yuxin Wang and Yu Zhang

Sustainability 2022, 14(23), 15952; https://doi.org/10.3390/su142315952 - 30 Nov 2022

Viewed by 1244

Abstract

The phenomenon of sudden changes in hydrodynamic coefficients cannot be neglected when the resonance of a two-dimensional rectangular moonpool occurs; however, it may not be meaningful to discuss the detailed values of hydrodynamic coefficients when the resonance occurs. The analytical solution of the [...] Read more.

The phenomenon of sudden changes in hydrodynamic coefficients cannot be neglected when the resonance of a two-dimensional rectangular moonpool occurs; however, it may not be meaningful to discuss the detailed values of hydrodynamic coefficients when the resonance occurs. The analytical solution of the hydrodynamic coefficients of a two-dimensional rectangular moonpool under sway motion derived based on the linear potential flow theory is first improved. The improved analytical results and the results with the far-field method are then compared and verified. The results show that the hydrodynamic coefficients of a two-dimensional rectangular moonpool under sway motion change suddenly at the second resonant frequency, which was not found in the original analytical solution of damping coefficient. Full article

(This article belongs to the Special Issue Ocean and Hydropower)

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