Pump Mode Research Articles

Development and validation of an AI-Driven model for the La Rance tidal barrage: A generalisable case study

In this work, an AI-Driven (autonomous) model representation of the La Rance tidal barrage was developed using novel parametrisation and Deep Reinforcement Learning (DRL) techniques. Our model results were validated with experimental measurements, yielding the first Tidal Range Structure (TRS) model validated against a constructed tidal barrage and made available to academics. In order to proper model La Rance, parametrisation methodologies were developed for simulating (i) turbines (in pumping and power generation modes), (ii) transition ramp functions (for opening and closing hydraulic structures) and (iii) equivalent lagoon wetted area. Furthermore, an updated DRL method was implemented for optimising the operation of the hydraulic structures that compose La Rance. The achieved objective of this work was to verify the capabilities of an AI-Driven TRS model to appropriately predict (i) turbine power and (ii) lagoon water level variations. In addition, the observed operational strategy and yearly energy output of our AI-Driven model appeared to be comparable with those reported for the La Rance tidal barrage. The outcomes of this work (developed methodologies and DRL implementations) are generalisable and can be applied to other TRS projects. Furthermore, this work provided insights which allow for more realistic simulation of TRS operation, enabled through our AI-Driven model.

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.

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.

Mathematical model of a cavity pump installation for separate-alternate operation of reservoirs

A mathematical model is developed for the separate-alternate operation of two layers by a screw pumping unit equipped with an electrovalve for switching between development objects. The model is based on the equation for the balance of fluid volumes flowing from the formation into the well, pumped out by the pump and accumulating in the well. Changes in bottomhole pressure, fluid inflow from reservoirs, pump feed in pumping and accumulation modes for the upper and lower reservoirs are analyzed at different rotational speeds of a screw rod pump. The model can be used to estimate the duration of the cycles of the upper and lower layers in the design of separate-alternate modes of screw rod installations. Keywords: simultaneous-separate mode, separate-alternate mode, screw pump, bottomhole pressure, inflow from the reservoir, feed. dpepelyaev@tehproekt.perm.ru, karbon@tatais.ru, urazakk@mail.ru

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.

Squeezed Light Generation in Three-Channel Nonlinear Coupler with Second-Harmonic Generation and Frequency Mismatch

Squeezed states of light in a three-channel nonlinear coupler with second-order nonlinearity using the phase space method and the analytical perturbative method is reported in this paper. The system is studied under the frequency mismatch condition, where the frequencies of the pump mode are not common. The effect of frequency mismatch on the generated squeezed states is investigated. We have found that the frequency mismatch does significantly affect the behavior of the generated squeezed states only at higher values of linear coupling between the waveguides. By increasing the frequency mismatch, the squeezing pattern also evolves from a collapses-revivals-like squeezing into a constant oscillation.

Piston Wear Detection and Feature Selection Based on Vibration Signals Using the Improved Spare Support Vector Machine for Axial Piston Pumps.

A piston wear fault is a major failure mode of axial piston pumps, which may decrease their volumetric efficiency and service life. Although fault detection based on machine learning theory can achieve high accuracy, the performance mainly depends on the detection model and feature selection. Feature selection in learning has recently emerged as a crucial issue. Therefore, piston wear detection and feature selection are essential and urgent. In this paper, we propose a vibration signal-based methodology using the improved spare support vector machine, which can integrate the feature selection into the piston wear detection learning process. Forty features are defined to capture the piston wear signature in the time domain, frequency domain, and time-frequency domain. The relevance and impact of sparsity in 40 features are illustrated through the single and multiple statistical feature analysis. Model performance is assessed and the sparse features are discovered. The maximum model testing and training accuracy are 97.50% and 96.60%, respectively. Spare features s10, s12, Ew(8), x7, Ee(5), and Ee(4) are selected and validated. Results show that the proposed methodology is applicable for piston wear detection and feature selection, with high model accuracy and good feature sparsity.

Modeling of a ring-core trench-assisted few-mode BDFA for seven-mode signal gain equalization.

In this paper, a ring-core trench-assisted few-mode bismuth-doped fiber amplifier (BDFA) is simulated on the basis of the three-energy level. The fiber is designed to support four modes of signal group transmission for practical considerations, including LP01, LP11, LP21, and LP31. The results suggest that (1) it is possible to obtain gain equalization of the three signal groups by using the LP21 mode pump independently, where the maximum difference in modal gain (MAX DMG) is about 0.9dB, except for the LP31 mode signal; (2) by combining the LP01 and LP31 mode pumps, the average gain of the groups increases by 14%, and the MAX DMG decreases by nearly 60% (3.8 to 1.5dB) compared to the LP01 pump alone; and (3) with the same combination of mode pumps, the ring-core BDFA (1.5dB) achieves better gain equalization than the single-core BDFA (2.8dB). The analysis is informative for the future development of a multimode BDFA.

Regulation of the mammalian-brain V-ATPase through ultraslow mode-switching.

Vacuolar-type adenosine triphosphatases (V-ATPases)1-3 are electrogenic rotary mechanoenzymes structurally related to F-type ATP synthases4,5. They hydrolyse ATP to establish electrochemical proton gradients for a plethora of cellular processes1,3. In neurons, the loading of all neurotransmitters into synaptic vesicles is energized by about one V-ATPase molecule per synaptic vesicle6,7. To shed light on this bona fide single-molecule biological process, we investigated electrogenic proton-pumping by single mammalian-brain V-ATPases in single synaptic vesicles. Here we show that V-ATPases do not pump continuously in time, as suggested by observing the rotation of bacterial homologues8 and assuming strict ATP-proton coupling. Instead, they stochastically switch between three ultralong-lived modes: proton-pumping, inactive and proton-leaky. Notably, direct observation of pumping revealed that physiologically relevant concentrations of ATP do not regulate the intrinsic pumping rate. ATP regulates V-ATPase activity through the switching probability of the proton-pumping mode. By contrast, electrochemical proton gradients regulate the pumping rate and the switching of the pumping and inactive modes. A direct consequence of mode-switching is all-or-none stochastic fluctuations in the electrochemical gradient of synaptic vesicles that would be expected to introduce stochasticity in proton-driven secondary active loading of neurotransmitters and may thus have important implications for neurotransmission. This work reveals and emphasizes the mechanistic and biological importance of ultraslow mode-switching.

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.

Numerical Investigation of the Flow Regime in the Vanes and the Torsional Self-Excited Vibration of Guide Vane in the Pump Mode of a Reversible Pump-Turbine

Guide vanes (GVs) are installed between the runner and the stay vanes for flow guidance and discharge regulation in reversible pump-turbines. The unstable torsional self-excited vibration of the guide vane (GV) may occur when running at small guide vane opening angles during the transient operations involving pump flow. In addition, the double-stage radial vanes may induce complex flow in the vanes and influence the stability of torsional self-excited vibration of the guide vane. In this study, numerical simulations were conducted at small guide vane opening angles in pump mode for two different guide vanes based on the three-dimensional computational fluid dynamics (CFD) method. The flow regime with a deflection was formed on the trailing edge with a circle in the vaneless region that rotated reversely against the runner rotation when operating at smaller guide vane opening angles for both of the two guide vanes. Based on this, the coupling simulations based on the CFD method with a single-degree-of-freedom (1DOF) oscillator were carried out under these operating conditions. Two flow types were formed at small opening angles when adopting different inlet boundary conditions. The results showed the flow regime with a deflection on the trailing edge may aggravate the instability of torsional vibration when applied as an initial flow field. Moreover, the vibration instability of the torsional self-excitation for two guide vanes was analyzed, showing that modifying the profile of guide vane airfoil is an efficient and reliable approach for weakening the torsional vibration instability.

1.5 μm passively Q-switched self frequency conversion optical parametric oscillator based on Nd3+ doped MgO:PPLN with the multi-focus end-face coupling pumping mode

A 1.5 μm passively Q-switched self frequency conversion optical parametric oscillator based on Nd3+ doped MgO:PPLN with the multi-focus end-face coupling pumping mode is reported. The reason for the generation of dual-wavelength fundamental frequency laser is explained by Nd:MgO:PPLN laser characteristics and energy level theory, and a multi-focus pumping thermal model is established to numerically simulate the temperature field distribution under different pumping injection modes. Compared with the traditional single-focus pumping mode, the multi-focus coupling pumping mode effectively disperses the thermal effect of the Nd:MgO:PPLN crystal, the oscillation of the σ-polarized 1093 nm laser is suppressed, the single-wavelength output of the π-polarized 1084 nm laser is realized. Thereby the more efficient 1514 nm signal light is obtained. In the experiment, the 1514 nm signal light with an average output power of 183 mW is obtained when the repetition frequency is 5.4 kHz, the pulse width is 6.8 ns and the pulse energy is 34 μJ in the double-focus pumping mode. In the triple-focus pumping mode, the 1514 nm signal light with an average output power of 165 mW is obtained when the repetition frequency is 5.6 kHz, the pulse width is 7.2 ns and the pulse energy is 30 μJ. Overall evaluation of the experimental effects of the two kinds of pumping modes shows that the double-focus pumping mode is superior to the triple-focus pumping mode.

Investigation on the hump region generation mechanism of pump mode in low-head pumped hydro-storage unit

The pump mode of the low-head pumped hydrostorage unit (pump-turbine) may operate in the hump region under extreme conditions due to the influence of water level variation, and the resulting energy conversion instability will seriously threaten the safety of the unit. However, the generation mechanism of the hump region is still not sufficiently understood, which is mainly due to two reasons: the dominant unstable flow structures that induce the formation of the hump region have not been uniformly recognized, and the influence of the dominant unstable flow structures on the impeller's working capacity has not been effectively revealed. In this study, experiments and numerical simulations were carried out on the low-head pumped hydrostorage unit in the pump mode, and the following results were obtained. It is found that the dominant unstable flow structures that induce the formation of the hump region are the leading edge backflow on the blade inlet shroud side and the horn-like vortex on the blade outlet hub side. The leading edge backflow reduces the blade loading and limits the impeller's working capacity, and the horn-like vortex increases the blade loading and increases the impeller's working capacity. The analysis revealed that the formation of the hump region is the result of the mutual restriction of the horn-like vortex and the leading edge backflow.

Lagrangian wavelet analysis of turbulence modulation in particle–liquid mixing flows

A new experimental–theoretical framework has been developed to investigate turbulence and turbulence modulation in a two-phase multicomponent particle–liquid flow in a mechanically agitated vessel. A discrete wavelet transform is used to decompose long-term three-dimensional Lagrangian trajectories of flow phases, acquired by a technique of positron emission particle tracking, into their deterministic and stochastic sub-trajectories. The sub-trajectories are then used to construct the different-scale local velocity and turbulent kinetic energy (TKE) fields of the two-phase flow. The effects of the particle size and size distribution mode (mono, binary, and polydisperse), particle concentration, impeller agitation speed, and pumping mode on turbulence intensity are investigated. Amongst these factors, the particle size, impeller pumping mode, and particle size distribution mode have a significant impact on liquid turbulence. The presence of large particles enhances liquid turbulence and broadens the region in the vessel characterized by high local TKE values. Results also show that a down-pumping pitched-blade turbine generates significantly greater local maxima in the TKE field, which tend to be more localized in the impeller discharge stream. In addition, binary or polydisperse suspensions containing higher fractions of larger particles produce higher turbulence intensities in the carrier phase. The detailed information obtained on the turbulence intensity is crucial for better understanding of the dynamics of particle–liquid flows inside mixing vessels to aid the rational design of these units.

Numerical Investigation on Torsional Mode Self-Excited Vibration of Guide Vane in a Reversible Pump-Turbine during Pump Mode’s Starting Up

In reversible pump-turbines, guide vane vibrations are considered to have potentially severe consequences of noise and structural damage. Unstable torsional mode self-excited vibrations of guide vanes have been reported at small guide vane openings during transient operations involving pump flow, such as pump starting and closing processes. In this study, coupling simulations were carried out under different operating conditions based on the unsteady computational fluid dynamics (CFD) method with a single-degree-of-freedom (1DOF) oscillator. The results show that the operating conditions, including the initial opening angle and the pressure difference between the runner side and the stay vane side, significantly affect the instability of guide vane torsional mode self-excited vibration. Energy-based analysis indicates that the positive cumulative work done by total hydraulic torque is responsible for unstable torsional mode self-excited vibration. Furthermore, the relatively small phase difference between total hydraulic torque and guide vane angular velocity, and the positive feedback between vibration amplitude and energy accumulation, are considered to be the root causes that eventually induce unstable self-excited vibrations under the operating conditions of small opening angles and high pressure differences.

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.

A compact design for an electric driven hydraulic gear machine capable of multiple quadrant operation

This paper presents an innovative design of an integrated electro-hydraulic (EH) flow generation unit able to operate in multiple quadrants. The proposed unit is composed of a hydraulic machine which can operate in either pumping or motoring mode, and an electric machine, which can operate as electric motor or generator. The adopted morphological integration of the two unit fulfills the goals of maximizing compactness, power to weight ratio, energy efficiency and quietness. The design results from a numerical optimization procedure that includes detailed simulation of both the electric machine and the hydraulic machine, using simulation tools previously developed by the authors, but combined for the first time in this work. After describing the optimization procedure, the paper focuses on the design integration aspects of the novel unit. A 9 kW prototype of the integrated unit was also fabricated and tested to verify its performance. Tests results show a measured overall energy efficiency up to 69%, demonstrating the potentials of the proposed concept, despite some limitations present in the first prototypes which could be addressed in future design refinements.

Transient simulation of the rapid guide vane adjustment under constant head of pump turbine in pump mode

In order to understand the flow mechanism of pump turbine during the rapid guide vane adjustment (RGVA), the shear stress transition (SST) k-ω turbulence model was used for transient simulation. The dynamic mesh technique was used to simulate the closing process of the guide vane. Combined with the verification of grid independence and the validation of experimental results, the variations of performance parameters (head, flow, torque), entropy production rate and pressure pulsation were calculated. And this process can be basically divided into three stages, including the preparation stage before the guide vane closing (Stage I), the guide vane closing stage (Stage II) and the completion stage of the guide vane closing (Stage III). The numerical simulation results showed that the performance parameters were varying in the form of exponential function during RGVA. The variation trend of the torque of each guide vane in the Stage II is basically the same, but the pulsation intensity in Stage III is different. In the Stage II, the guide vane is the component with the largest change in hydraulic loss, rising by about 362.5 %. The high energy dispersion sites are filling the flow passages of the guide vanes and the static vanes. The position with high pressure pulsation amplitude in the vaneless region also shifted, and the offset angle was 2–3°. The composition and evolution of the vortex structure in the vaneless region and the flow passage are determined by the Q-criterion. These structures, including horseshoe vortex and spanwise vortex, are the main reasons for the increase of pressure pulsation amplitude.

Optimizing the coupling efficiency of spontaneous parametric down-conversion photon pairs into single-mode fibers

Both correlated-mode coupling efficiency and photon pair flux (brightness) of spontaneous parametric down-conversion (SPDC) coupled into single-mode fibers are key parameters for various quantum information science applications. We present an experimental investigation on the optimization of the correlated-mode coupling efficiency and the brightness of frequency-degenerated SPDC photon pairs into single-mode optical fibers. Using photon pairs generated from a type-I phase-matched bulk $\ensuremath{\beta}$-barium borate crystal pumped by a continuous-wave laser, we carefully evaluated both the correlated-mode coupling efficiency and the brightness of SPDC light coupled to a single-mode optical fiber, while continuously changing the focusing of the pump and collection modes, experimenting with Rayleigh lengths from 3 to 280 (for the pump) and 0.2 to 20 (for the collection) times the crystal length. The measured data suggest that the correlated-mode coupling efficiency can be close to unity for any pump focus, however, the optimal Rayleigh length of the collection mode depends on the pump focus parameter, and the brightness can be increased by tightening the pump focus, provided that the Rayleigh length of the collection mode is precisely adjusted. A maximal correlated-mode coupling efficiency of $99.0\ifmmode\pm\else\textpm\fi{}1.3%$ was experimentally achieved. These results will be useful for photonic quantum science and technology using SPDC sources with high heralding efficiencies.