Turbine Mode Research Articles

Modes of operation of network pumps with shielded asynchronous motors in small irrigation systems with artificial pressure

The paper proposes a scheme and describes the operating modes of pumping equipment for a finely dispersed irrigation system with artificial pressure for the operating ranges of the performance of sprinklers in terms of flow. For the accepted ratio, which determines the kinetic energy of a drop per unit area, the law of drop motion in air under the action of gravity is obtained. The above network diagram in the process of regulation provides water supply for irrigation, taking into account the measured values of the sprinkler performance over time. Regulation using a centrifugal pump with a shielded asynchronous motor of the current values of water flow in the distribution pipeline connected to the sprinkler provides the technical possibility of implementing the mode corresponding to the inverted (turbine) mode of operation of the pump. The transfer of the engine to the generator mode of operation, allows you to get an autonomous three-phase source of electrical energy for the system’s own needs.

Improved Prediction Model and Utilization of Pump as Turbine for Excess Power Saving from Large Pumping System in Saudi Arabia

The throttling process is frequently encountered in many industrial practices utilizing Pressure Reducing Valves (PRVs). This process is typically used to control pressure and flow in pipeline networks. The practice of utilizing PRVs is considered simple and cheap in terms of installation cost and control. It dissipates the excess fluid energy that can be used for other purposes. This paper studies the feasibility of utilizing the Pump as Turbine (PAT) concept to partially recover the excess power dissipated from PRVs located at the discharge lines of refined product shipping pumps at one of the hydrocarbon distribution facilities in Saudi Arabia. Multiple PAT installation layouts have been studied to achieve this goal, selecting the optimum option to maximize the power recovery. The final selection of PAT was conducted to achieve a reasonable payback period. A new method for predicting the pump performance in reverse mode was developed depending on the manufacturer’s pump performance curves. The comparison of the proposed model with experimental data and previous models for three modes of operation reveals that the proposed model in this paper’s results either have the minimum deviation or the second minimum deviation out of all models. In the case of flow ratio prediction, the predicted deviation is merely 3.83%, −1.14%, and 1.35% in three modes of operation. For power prediction, the proposed model is the best and the only reliable model out of all with the least deviation of −7.48%, 0.07%, and −3.16% in three modes of operation. The economic analysis reveals the Capital Payback Time (CPP) for five optimum PATs is around 5 years. The new method was also validated against previous models showing more precise performance prediction of multistage centrifugal pumps running in turbine mode.

Optimization of a Management Algorithm for an Innovative System of Automatic Switching between Two Photovoltaic and Wind Turbine Modes for an Ecological Production of Green Energy

Today, renewable energy and energy efficiency are key to limiting global warming and preventing the dangerous effects of climate change. The biggest problem with conventional solar and wind turbine systems is the intermittency of electrical power generation. Even if these two energy sources can be complementary, the space occupied by these hybrid systems remains very important. This work proposes an improved management algorithm for a patented transformable photovoltaic-wind system, which mainly uses two flexible photovoltaic panels which are automatically deformed by an electromechanical system from the planar shape to the semi-cylindrical shape of the Savonius wind turbine blades. When weather conditions change, this system switches to eco-friendly photovoltaic (PV) or wind turbine (WT) mode, allowing a good total power generation from two solar power sources or wind turbine power. The contribution brought for this work relates to the realization and the improvement of the management algorithm to determine a better change to the mode PV or the mode WT. The operation test was simulated in 8760 hours for the year 2021. This developed algorithm allows several theoretical calculations of the power produced from solar radiation and wind speed data, thereafter the algorithm compare and determines the overall power and selects the optimal PV or WT mode. In this study, the overall power generated by the invented system produces more electricity per hour, the power Pt increases by 75.55% compared to the power Pwt, and also the power Pt increases by 68.15% compared to Pvp power.

Enhanced affinity law for centrifugal pumps at variable speed

The paper presents a novel approach for analytical representation of specific energy E and torque T curves versus discharge Q and speed N, for centrifugal pumps operated at variable speed both in pump and turbine mode. An enhanced polynomial expression valid for both E(Q,N ) and T(Q,N) is introduced and validated against experimental data.

Energy performance evaluation of an axial-flow pump as turbine under conventional and reverse operating modes based on an energy loss intensity model

As a low-cost scheme for small-scale hydropower generation, pump as turbines (PATs) are used at different hydrosites around the world. Nevertheless, a big number of recently conducted studies on PAT performance have mainly focused on the centrifugal type, despite the fact that the axial-flow type has a comparatively large flow capacity, thus disposing of higher power density. Therefore, this article seeks to investigate the flow dynamics of an axial-flow PAT and associated energy loss characteristics, under both pump and turbine operating modes. It adopts the numerical simulation method and uses entropy production theory to propose an energy loss intensity model in the cylindrical coordinate system, which quantitatively gives the spatial variation pattern for energy losses in pump and turbine operating modes. In addition, the correlation between energy loss and flow instability is deeply analyzed, where the energy characteristics in pump and turbine modes are quantitatively evaluated. It is shown that the energy loss within the impeller and the guide vane flow fields, for both operating modes, is mainly because of the turbulent entropy production. The proportion of direct entropy production and wall entropy production is found to be relatively small. The velocity gradient, flow vorticity, turbulence intensity, and energy losses within the flow passages of the axial-flow PAT have been closely related. However, owing to the difference in PAT operating modes, there is a significant difference in the location of energy losses. The unstable flow phenomena, such as the impact at the blade inlet, flow deviation at the blade outlet, flow separation, back-flow, and vortex, are the main reasons for entropy production. This study serves as a reference for the design, optimization, and application of axial-flow PATs.

Hydrodynamic optimization of pump-turbine runner

The paper suggests the approach to automatic CFD-based optimization of the pump-turbine runner. An in-house 3D flow solver CADRUN is used for the solution of steady-state RANS equations and evaluation of objective functions in representative operating points of turbine and pump operating regimes. Both efficiency and cavitation characteristics are taken into account. Two approaches have been considered, resulting in 4- and 3-objective shape optimization problems. These problems were solved using multi-objective genetic algorithm. It was shown that the obtained optimized runners feature increased efficiency both in turbine and pump mode with cavitation performance, similar to that of the initial runner.

Effect of 3D Shape of Pump-Turbine Runner Blade on Flow Characteristics in Turbine Mode

The effect of blade spatial profiling with the help of tangential blade lean of Francis pump-turbine runner with heads up to 200 m on the flow structure and energy characteristics was numerically investigated. A flow part model of Francis pump-turbine of the Dniester pumped storage plant was adopted as original version. Two new blade systems were designed, which differed from the original version by mutual position of cross-sections in tangential direction: with positive and negative lean, while the shape of the cross-sections themselves remained unchanged. Modeling of the viscous incompressible flow in calculation domain, which contains one channel of the guide vane and the runner, for three variants of flow parts, was performed using the IPMFlow software based on numerical integration of the Reynolds equations with an additional term containing artificial compressibility. To take into account the turbulent effects, the SST differential two-parameter turbulence model of Menter is applied. Numerical integration of the equations is carried out using an implicit quasi-monotonic Godunov scheme of second order accuracy in space and time. The study was carried out for models with runner diameter of 350 mm in a wide range of guide vane openings at reduced rotation frequencies corresponding to the minimal, design and maximal heads of the station. A comparison of pressure fields and velocity vectors in the runners, pressure graphs on runner blades, distribution of velocity components at inlet to a draft tube, and efficiency of three variants of flow parts are presented. It was concluded that calculation domain with the new RK5217M2 runner with negative tangential lean has the best characteristics. An experimental study of three runners on a hydrodynamic stand are planned

Pressure pulsation reduction in the draft tube of pump turbine in turbine mode based on optimization design of runner blade trailing edge profile

Reversible pump turbine plays an important role in pumped storage technology. Its pressure pulsation performance also directly affects the stability and efficiency of unit operation. In this paper, under the conditions of multiple guide vane openings and multiple heads for a pump-turbine unit, based on the reasonable runner blade geometric deconstruction, a parameter control method of runner blade trailing edge is proposed. The Genetic Algorithm combined with Fuzzy Logic (GA-FL) is used as the optimization strategy. After optimization iteration, the optimized runner blade trailing edge shape corresponding to minimum value of pressure pulsation intensity is obtained. In addition, numerical simulation calculation and test verification are carried out for the initial and optimized units, the results are all in good agreement. The results show that the unit efficiency is slightly improved and the relative pressure pulsation intensity in draft tube is significantly reduced. Especially in the case of small guide vane opening, the pressure pulsation performance of optimized unit meets the actual engineering standards.

Numerical simulation of performance of traveling wave pump-turbine at different wave speeds in pumping mode

Fish swim by flexing their bodies and energy is transferred from the fish to the water. And the plate which imitates traveling wave motion of fish can absorb the energy of fluid under certain motion parameters. By arranging the traveling wave plate in a vertical rectangular flow channel, the flow mode is changed from external flow mode to internal flow mode. This internal flow device is called traveling wave pump-turbine, and it can operate in both pumping mode and turbine mode. The traveling wave plate is simplified into a two-dimensional plate, and the model of the traveling wave pump-turbine is established. The numerical simulation method is used to study its performance characteristics at different wave speeds when it is in pumping mode. The results show that: although it operates in pumping mode by changing the volume of the working chamber, it can output stable mass flow rate. With the increase of wave speed, the volumetric efficiency increases gradually, the time-averaged efficiency first increases and then decreases, and the maximum time-averaged efficiency can reach 0.9. The instantaneous pressure and power are relatively stable when the wave speed is low, while they fluctuate more sharply with the increase of wave speed.

Experimental study of a centrifugal pump operating as a hydraulic turbine

An experimental investigation of centrifugal pump has been carried out to study its characteristics in pump and turbine mode operation (PAT). The correlation between pump and PAT performance is a major problem. Several methods have been developed to predict the best efficiency of pumps running as turbines, but their results are not in good coincidence with experimental data for all pumps. Fluid dynamic behavior of PAT changes appreciably, in relation to its localized and distributed hydraulic losses, velocity profiles and pressures at homologous points. It is not possible to infer the behavior of a PAT using similarity parameters from pump mode performance; very large errors are made. This paper presents the experimental parameters of the operating of a PAT with specific number low. In order to determine the pump’s characteristic as turbine, we used a closed-circuit experimental setup in which the admission pressure head was realized with another pump and the correlation between the diameter of the PAT and the specific number for three different ranges of flow was determined. This is based on an experimental database on a centrifugal pump of specific number 17 .80 [RPM, m3 /s, m] in bothrotation modes and for a speed range of rotation between 250 and 2500 RPM. All required parameters were measured to achieve complete characteristic curves of the reverse pump. The functional characterization showed curves of the hydraulic machine in the turbine mode with variation of operating parameters, such as rotation speeds, heights, and flow rates. With the results obtained, the comparatives made allowed observing the influence of these variations on the performance of the PATs. Curves obtained allowed inferring the behavior in turbine mode from pump mode parameters. Values obtained from the derived correlations showed good match with experimental results.

Simplified complex-valued modal model for operating wind turbines through aerodynamic decoupling and multi-blade coordinate transformation

An efficient modelling methodology for steady-state operating wind turbines is proposed, combining aerodynamic decoupling, multi-blade coordinate transformation, and modal reduction. This leads to a complex-valued, reduced-order modal model for prediction of dynamic responses of the tower-rotor-blade wind turbine system, considering rotor rotation, blade flexibility, and vibration coupling between rotor and tower. A fully coupled finite element model was first developed, with aerodynamic forces linearised and expressed as a viscous aerodynamic damping matrix. A time-invariant state space model is formed using multi-blade coordinate transformation, allowing standard modal analysis. The complex-valued eigenvalues and mode shapes were obtained, and it is shown that the operating wind turbine modes exhibit a combination of tower and blade vibrations. Various degrees of modal reduction are applied to the state space model to obtain a modal model with fewer degrees of freedom, whose performance was evaluated in the time and frequency domain for operating wind turbines in normal condition. The displacement and stress responses are in close agreement with those of the fully coupled model with the first 21 modes included. The model already performs well with 8 modes considered to capture relevant fundamental frequency peaks. This allows significantly reduced computational effort and can be particularly beneficial for fatigue prediction, reliability analysis, and structural identification.

Hydraulic loss analysis in a pump-turbine with special emphasis on local rigid vortex and shear

Since the pump as turbine is increasingly employed in energy storage, improving efficiency in both pump and turbine modes is required for economic benefits. This study aims to analyze vortex flow characteristics and vortex control methods in both modes to reduce hydraulic loss. In this paper, a delayed detached eddy simulation was applied in a low specific speed pump-turbine. Based on the entropy production analysis and vorticity binary decomposition in the local vortices, the results show that the local shear is the leading cause of hydraulic loss instead of the existence of vortices. The average wake loss can be 1.6 times higher than the loss in jet regions in pump mode, but there is little difference in the distribution of shear and vortices in the wake flow in turbine mode. The local loss caused by the rotor–stator interaction with a tongue effect at blade passing frequency is up to threefold over the loss without a tongue effect in both modes. Reducing shear and ratio of shear to rigid vorticity of the local vortices via modification in the volute tongue angle to suppress the tongue effect can be an effective way to decrease hydraulic loss in both modes.

Bypass Control strategy of a Pump as Turbine in a Water Distribution Network for energy recovery

Water Distribution Networks (WDNs) are subject to leakages due to pipes aging, resulting in water and pressure losses. These issues are solved by installing Pressure Reduction Valves (PRVs) to decrease the pressure in WDNs. Depending on the application, PRVs can waste large amount of energy, hence the substitution of PRVs with Pumps used as Turbines (PaTs) can be a good compromise in terms of economic and technical aspects to reduce leakages and recover energy. Currently the share of PaT is not yet fully developed due to the certain technical challenges yet to be addressed, as providing an affordable control strategy closer to the real working conditions in a WDN. Hence, more experimental activities are required. For these reasons, in this work an experimental campaign was carried with the aim to investigate the behavior of a PaT according to a possible layout that could be embedded into a WDN. Firstly, the machine was characterized both in pump and turbine modes. Moreover, the machine working conditions limits have been analysed in terms of runaway and blocked-rotor curves. Then, turbine tests were carried out at constant speed with a typical hydraulic control scheme by means of a PRV installed in series to the PaT and a second one installed on a bypass. As a result, this analysis highlighted the feasibility to recover a consistent amount of hydraulic energy otherwise wasted under typical WDN daily pressure and flow rate patterns, with promising results in terms of the operating point control of the machine.

Design optimization of an AUV for performing depth control maneuver

A methodology for optimizing the inertial characteristics, propeller, battery capacity and PID (Proportional Integral Derivative) controller for propeller of an Autonomous Underwater Vehicle (AUV) is proposed in this paper. The AUV is launched at high speed in horizontal orientation, thereafter it pitches bow down and finally hovers at a particular desired water depth. The study involves both positively and negatively buoyant AUV. Four quadrant propeller open water model and quaternion are incorporated in the Maneuvering Modeling Group (MMG) type maneuvering model to make it suitable for 7 degree of freedom (DoF) dynamics. The bow down orientation is performed due to the inertial characteristics of the AUV, while the depth control maneuvering of the AUV is carried out by using PID controller for propeller revolutions. A cost function is proposed in terms of energy consumed and the distance traveled by AUV during the desired maneuver. The numeral value of cost function can be computed by carrying out numerical simulations. The numerical simulations can estimate when the AUV's propeller works in turbine mode. This information is useful for protecting the electric/electronic components of the AUV.

Flow-Induced Vibration of Non-Rotating Structures of a High-Head Pump-Turbine during Start-Up in Turbine Mode

Pumped storage-power plants play an extremely important role in the modern smart grid due to their irreplaceable advantages in load peak-valley regulation, frequency modulation, and phase modulation. The number of start-stops per day of pump-turbine units is therefore also increasing. During the start-up transient process in turbine mode, the complex flow in runner passage, crown and band chambers, and seal labyrinth is able to induce severe vibration of non-rotating structures such as head cover, stay-ring, and pose a threat to the safe operation of the pump-turbine unit. In this article, the flow-induced vibration of the structures of a pump-turbine unit during its start-up process in turbine mode is studied. In the first place, this investigation establishes a three-dimensional model of the full flow passage and carries out a full three-dimensional CFD calculation based on one-dimensional pipeline calculation results for the start-up transient process. In the next place, by applying the fluid–structure interaction calculation method, the finite element analysis of non-rotating components of the pump-turbine unit is carried out. The flow-induced stresses and deformations of head cover, stay-ring, etc., are obtained and analyzed. The results reveal that the maximum deformation of the non-rotating structures is located at the inner edge of the head cover while the maximum stress appears at the trailing edge fillet of a stay vane. In summary, the dynamic stress of the non-rotating structures changes largely during the start-up process. The stress is strongly related to the axial thrust caused by the fluid flow. The achieved results can provide guidance for further fatigue life assessment of non-rotating structures and contribute to the structural safety design of pump-turbine units.

Analysis of two-phase flow in cavitation condition of pump-turbine based on dynamic mode decomposition method in turbine mode

Cavitation is an inevitable and important problem in the design, manufacture and operation of pump-turbine. The research on cavitation of pump-turbine is mainly focused in the pump mode, but the cavitation characteristics of turbine mode are also very important. Traditional research methods are unable to dig a large amount of research data in cavitation flow. Therefore, the dynamic mode decomposition (DMD) method is used in this study to investigate the incipient cavitation and critical cavitation of a model pump-turbine. The results show that the DMD method can accurately extract the characteristics of the runner in pump mode under cavitation conditions. The development of cavitation makes the mode decomposition of the two-phase flow field and the reconstruction of the low order modes significantly different. DMD method is more suitable for signals with clear frequency and simple mean value and pulsation. The development of cavitation makes the reconstruction of low order modes change obviously, from the inception cavitation condition of first waveform reconstruction and then mean-value reconstruction to the critical cavitation condition of first mean-value reconstruction and then waveform reconstruction. It provides a new research idea for cavitation research of pump-turbine.

Study on energy conversion characteristics and pressure fluctuation interference characteristics between two stage impellers of the pump as turbine

The process pump as turbine (PPAT) is an important infrastructure in chemical and oil refining process. When it operates in pump mode, it can provide high-pressure energy for chemical and oil refining system, and when it operates in turbine mode, it can recover the high-pressure energy from the oil medium. The operation stability of PPAT directly affects the normal operation and production of chemical and oil refining process. In this paper, the velocity slip characteristics of the PPAT in turbine mode and pump mode were studied, and the unsteady operation characteristics and the energy conversion and distribution mechanism of the first-stage impeller and second-stage impeller in pump mode were mainly studied, the pulsation amplitude frequency characteristics and induction mechanism of flow passage components under different flow conditions in pump mode are analyzed. The results show that PPAT has an efficiency peak in both pump mode and turbine mode, and the efficiency zone is significantly wider and the velocity slip loss is smaller in turbine mode; In turbine mode, with the increase of flow, the velocity slip loss of the first-stage impeller is larger than that of the second-stage impeller; In the pump mode, the velocity slip loss of the first-stage impeller is greater under the conditions of minimum flow and maximum flow, the pressure fluctuation in the PPAT is mainly distributed in the first stage diffuser and the second stage diffuser. The main factor causing the pressure fluctuation in the PPAT is the dynamic and static interference effect between the first-stage impeller and the first-stage diffuser.

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.
 AIMS: The aim of the work was to present an economical methodology for numerical simulation of energy characteristics.
 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.
 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.
 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.
 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 investigations and 3D simulations by the overset grid method on twin-screw machines in both pump and turbine mode

Twin-screw pumps due to their particular capabilities, offer u nique b enefits in comparison to other types of pumps. They can also recover wasted energy from the fluid system when run in a reversed way, i.e., in turbine mode. In this study, the possibility of benefiting twin-screw machines instead of conventional control valves in order to recover energy is investigated. Flow physics and energy recovery are analyzed experimentally and by 3D flow simulations in both, pump and turbine mode. Pump and turbine characteristics under different operating points are experimentally measured for low and high viscous fluids, i.e., water and oil, respectively. It is observed that for higher viscosity the dependency of volume flow rate on the pressure difference imposed on the pump is reduced. This observation indicates the significant effect of viscosity on the gap flow. Based on a simulation method by means of overset grid technique, unsteady 3D flow simulations with a high grid quality and a high spatial resolution particularly in gap regions in terms of y + < 1 are conducted and results are validated against experiments. The profound assessment of gap flow based on the simulation results shows that for highly viscous fluids such a soil, the rotational speed of spindles as well as the direction of rotation have a significant effect on gap flow characteristics and consequently on the pump and turbine performance. From the experiments, it is clarified that with a lower rotational speed of spindles and a higher pressure difference, a higher amount of energy up to about 50% of the fluid energy in the piping system can be recovered instead of being dissipated by a conventional control valve.

Optimization of geometric parameters of hydraulic turbine runner in turbine mode based on the orthogonal test method and CFD

The hydraulic turbine in turbine mode (TMHT) with ultra-low specific speed is a new type of energy recovery device for recovering energy stored in the high-pressure fluid. In order to solve the problem of insufficient consideration of runner geometric parameter optimization, this paper proposes an optimization strategy (OT-CFD), which is based on the orthogonal test method and computational fluid dynamics (CFD), to optimize the performance of the TMHT runner. Firstly, the orthogonal test schemes are established with 5 levels of runner inlet diameter, outlet diameter, inlet height, blade inlet angle, and blade number. Then 25 three-dimensional models of two-stage TMHT containing flow passage components such as Francis runner are built. Further, the internal flow characteristics and energy characteristics of TMHT are calculated and then verified by the real machine test. By comparing the numerical simulation results, the design schemes of runner geometry parameters corresponding to the highest head (H) and the highest efficiency (η) are determined, respectively. On this basis, the optimization effect of runner geometry parameters is analyzed by numerical simulation based on CFD. In conclusion, the inlet angle is the most important factor affecting the efficiency, and the runner inlet diameter is the most important factor affecting the water head. Compared with the comparison scheme, the optimal η scheme has a more stable flow pattern, which provides an efficiency increase of 10.9%, a water head increase of 26.75 m, and a power increase of 646.32kW, greatly reduces the energy loss in the process of residual pressure recovery; the optimal H scheme has an efficiency increase of 2.61%, but more stable and regular flow pattern. More importantly, the optimal water head scheme, which has a water head increase of 185.53 m and a power increase of 1518.3kW, greatly increases the capacity of recovering the water head.