Pumping Conditions Research Articles

Kohn-Sham-Proca equations for ultrafast exciton dynamics

A longstanding problem in time-dependent density functional theory has been the absence of a functional able to capture excitonic physics under laser pump conditions. Here we introduce a scheme of coupled Kohn-Sham and Proca equations in a pump-probe setup that we show (i) produces linear-response excitonic effects in the weak pump regime in excellent agreement with experiment, but also (ii) captures excitonic physics in the highly nonlinear regime of ultrafast strong laser pumping. In particular ”bleaching” (i.e., reduction) of the excitonic weight and the appearance of excitonic side bands is demonstrated. The approach is a procedural functional—the Kohn-Sham and Proca equations are simultaneously time propagated—allowing the straightforward inclusion of, for example, lattice and spin degrees of freedom into excitonic physics. The functional is shown to have universal applicability to a wide range of materials, and we also establish a relation between the parameters used in the functional and the exciton Bohr radii of the materials. Published by the American Physical Society 2025

Study on evolution characteristics of energy dissipation and vortex in pump-turbine during load rejection transition process

The widespread adoption of intermittent wind and solar energy sources disrupts the stability of power grids, necessitating frequent load rejection processes for pump-turbine. This jeopardizes the stability of pump-turbine units. To investigate the operating behavior of pump-turbine units during load rejection, this study focuses on a Francis reversible pump-turbine. Employing the results from a one-dimensional characteristic line method as boundary conditions, three-dimensional numerical simulations are conducted. The entropy production theory was employed to quantify energy loss in different components, including direct dissipation, turbulent dissipation, and wall shear stress. And the pressure load curves of runner blades at different spans are extracted. The flow characteristics, entropy production losses, and pressure loads within the passage are analyzed at various moments during the load rejection process. Results demonstrate that when a unit undergoes load rejection, it repeatedly transitions into and out of the S-characteristic region. The flow state within the passage is most unfavorable under reverse pump conditions, with the entropy production loss reaching its maximum value of 339 160 W/K. When the unit's rotational speed increased beyond 1.1nd, the unit's water thrust and torque underwent drastic changes. Moreover, the pressure load undergoes significant variations under runaway conditions, with the pressure load difference among various blades reaching up to 33 000 kPa. These findings provide a scientific basis for ensuring the safe and reliable operation of pump-turbine units during load rejection processes.

Machine learning based sucker rod pump fault diagnosis using motor power curve

Relevance. The complexity of monitoring and diagnosing the condition of underground structural elements of sucker rod pumping units and large economic losses when operating this equipment with defects not identified in a timely manner. Aim. Development of methods for detecting faults in a sucker rod pump that do not require the involvement of highly qualified personnel for diagnosis, using information that is easily available on the surface. Methods. Machine learning methods (Decision tree method, K-nearest neighbors method, Support vector machine, Naive Bayes classifier) using motor power curves. Results and conclusions. The paper demonstrates the possibility of detecting faults in a sucker rod pump based on machine learning methods. The study was carried out on the basis of a developed simulation model of a sucker rod pump, used to reproduce motor power curves, taking into account the impact of the features of various equipment operation scenarios. Being the fundamental energy source for the oil production, motor power is directly related to the real-time operating condition of the oil well, and the motor power curve is a reliable source with the ability to increase the efficiency of sucker rod pump diagnostic. To train the machine learning classifiers and evaluate their performance accuracy, a number of characteristics were used, obtained from motor power curves for six different pump operating states. Namely, operating coefficients were calculated, representing the ratio of the power integral at each of the four stages of the installation operating cycle to the power integral for the entire cycle. The results show that the considered approach allows for high accuracy in diagnosing the operating conditions of a sucker rod pump. The classifier based on the decision tree method showed the highest efficiency among the four studied classifiers in identifying all six types of faults (95.8%), and the support vector machine method showed as well very high efficiency (90.3%).

Site-Specific Hydrogeological Characterization for Radiological Safety: Integrating Groundwater Dynamics and Transport

The radiological impact of radionuclide transport via groundwater pathways at the Wolsong Low- and Intermediate-Level Waste (LILW) Disposal Center was estimated by considering site-specific characteristics, including hydrogeology, geochemistry, and land use. Human intrusion scenarios, such as groundwater well development, were analyzed to evaluate potential pumping volumes and radionuclide migration pathways. Particular attention was given to the hydrological and geochemical aspects of radionuclide transport, with a focus on local aquifer heterogeneity, flow dynamics, and interactions with engineered barriers and surrounding rock formations that delay radionuclide migration through sorption and other retention mechanisms. Sorption coefficients (Kd), calibrated using site-specific geochemical data, were incorporated to ensure realistic modeling of radionuclide behavior. A hierarchical approach integrating scenario screening, particle tracking techniques, and mass transfer modeling was employed. Numerical simulations using FEFLOW ver. 7.3 and GoldSim ver. 14.0 software provided insights into near-field and far-field transport phenomena under well pumping conditions. The results revealed distinct spatial flux behaviors, where carbon-14 (14C) dominated near-field flux due to its high inventory, while technetium-99 (99Tc) emerged as the primary dose contributor in the far-field flux, owing to its anionic nature and limited sorption capacity. Additionally, under high-pH conditions near concrete barriers, cellulose degradation into isosaccharinic acid was identified, enhancing radionuclide mobility through complex formation. These findings underscore the importance of site-specific sorption and speciation parameters in safety assessment and highlight the need for accurate geochemical modeling to optimize waste placement and ensure long-term disposal safety. The outcomes provide valuable insights for optimizing waste placement and contribute to the development of evidence-based safety strategies for long-term performance assessment.

Hydraulic oscillations and stability testing of a novel shaft coaxial surge chamber with small load disturbances in pumped storage power stations

Surge chambers play a critical role in moderating oscillations in pumped storage power stations after load disturbances. Owing to the high costs, increased risks, and extended construction times associated with conventional surge chambers (CSCs), we proposed a shaft coaxial surge chamber (SCSC) as an alternative, which was otherwise a compact, economical, and construction-friendly structural configuration. The present study aimed to investigate the hydraulic oscillations, stability, and flow characteristics of an SCSC compared to a CSC under disturbance conditions. Physical models of both types of surge chambers were developed and validated. The results indicated that the novel SCSC system could maintain stability before and after disturbances; its hydraulic fluctuations were slightly higher than those of the CSC, particularly under pumping conditions. During the disturbance, the water level fluctuation amplitudes in the SCSC were at least 1.43 and 2.24 times those of the CSC under different working conditions with 10% flow disturbance. As the disturbance frequency increased, the stability of the SCSC approached that of the CSC. Moreover, a new discharge coefficient range of 0.9–1.2 for the SCSC was proposed, increasing the conventional standard values by 1.5 times. In conclusion, the higher discharge coefficient and unstable flow patterns in the connecting pipe are critical mechanisms that influence the hydraulic oscillations of the SCSC. These findings provide valuable theoretical guidance for practical applications.

Optimization of design parameters and operation conditions of solar-air source heat pump coupled system for rural buildings in cold and severe cold regions

Integrating solar energy utilization into air source heat pump heating systems can effectively cut down on energy consumption. However, the complexity of coupled systems poses a challenge to system performance optimization. In this paper, a solar-air source heat pump coupled system designed for heating in cold (Beijing) and severe cold (Changchun) regions is developed and analyzed by TRNSYS software. Response surface methodology (RSM) is employed to establish regression models for different performance indicators, and then the non-dominated sorting genetic algorithm-II (NSGA-II) is adopted to solve the multi-objective optimization of interactive performance parameters through Pareto optimal solution set. The regression models of the performance indicators, i.e., the energy consumption (P), the solar energy assurance rate (Ar) and the ratio of heating supply from solar energy storage tank to building load (Hs), are found to be closely related to the area of solar collectors (A) and the volumes of storage tanks (Vl for solar collector loop and Vs for ASHP loop). The obtained Pareto set successfully balances the optimal values of interactive performance indicators. In cold regions, P, Ar, Hs of the coupled system can be improved respectively by 31.79%, 33.00% and 40.07% compared to the single air source heat pump system. While in severe cold regions, these improvements are 16.25%, 15.35% and 28.38%, respectively. The design method and optimization procedure of this study provide a basis for the optimization of the solar and auxiliary heat source coupled heating systems.

Residential heat pump and air conditioning systems with propane (R290) refrigerant: Technology review and future perspectives

Residential heat pump and air conditioning systems with propane (R290) refrigerant: Technology review and future perspectives

Tunable Continuous-Wave Terahertz Generator based on Difference Frequency Generation with DAST Crystal

Terahertz (THz) wave has been widely investigated recently due to the perspective of reflecting fingerprint characteristic of samples. As a promising method, THz technology has attracted great interests in various applications, especially in biological imaging, environmental monitoring, non-destructive evaluation, spectroscopy and molecular analysis. To reveal the intramolecular vibration/rotation information of various compound, of which linewidth of absorption lines typically in GHz or even MHz range, THz wave with wide tunability, narrow-linewidth, high frequency accuracy as well as high power stability is required. Currently, the linewidth with GHz level and low SNR at higher frequency still restrict its further applications in reveal intramolecular information. In this paper, the thermal distribution characteristics of DAST crystals based on diamond substrates under continuous laser pumping conditions were theoretically studied by COMSOL Multiphysics, and the effectiveness of diamond substrates in dissipating heat from DAST crystals was experimentally verified. Then, a narrow linewidth and tunable continuous-wave terahertz source with organic crystal has been demonstrated. Two narrow-linewidth CW fiber lasers were used as the pump sources for difference frequency generation. The terahertz wave can be continuously tunable in the range of 1.1-3 THz. The maximum output power of 3.39 nW was obtained at 2.493 THz. The power fluctuation in 30 minutes was measured to be 2.19%. In addition, the generated THz wave has a high polarization extinction ratio of 9.44 dB. Using this CW-THz source for high-precision spectral detection of air with different humidity, the results correspond well with the gas absorption spectral lines in the Hitran database, proving that the CW-THz source has narrow linewidth, high frequency accuracy and stability. Therefore, it could promote the practical prospect of tunable CW-THz source, which will have good potential in THz high-precision spectroscopic detection and multispectral imaging.

Pipeline and Rotating Pump Condition Monitoring Based on Sound Vibration Feature-Level Fusion

The rotating pump of pipelines are susceptible to damage based on extended operations in a complex environment of high temperature and high pressure, which leads to abnormal vibrations and noises. Currently, the method for detecting the conditions of pipelines and rotating pumps primarily involves identifying their abnormal sounds and vibrations. Due to complex background noise, the performance of condition monitoring is unsatisfactory. To overcome this issue, a pipeline and rotating pump condition monitoring method is proposed by extracting and fusing sound and vibration features in different ways. Firstly, a hand-crafted feature set is established from two aspects of sound and vibration. Moreover, a convolutional neural network (CNN)-derived feature set is established based on a one-dimensional CNN (1D CNN). For the hand-crafted and CNN-derived feature sets, a feature selection method is presented for significant features by ranking features according to their importance, which is calculated by ReliefF and the random forest score. Finally, pipeline and rotating pump condition monitoring is applied by fusing the significant sound and vibration features at the feature level. According to the sound and vibration signals obtained from the experimental platform, the proposed method was evaluated, showing an average accuracy of 93.27% for different conditions. The effectiveness and superiority of the proposed method are manifested through comparison and ablation experiments.

Reconfigurable entanglement distribution network based on pump management of a spontaneous four-wave mixing source.

Leveraging the unique properties of quantum entanglement, quantum entanglement distribution networks support multiple quantum information applications and are essential to the development of quantum networks. However, practical implementation poses fundamental challenges to network scalability and flexibility. Here, we propose a reconfigurable entanglement distribution network scheme based on tunable multipump excitation of a spontaneous four-wave mixing (SFWM) source and a time-sharing method. We characterize the two-photon correlation under different pump conditions to demonstrate the effect of pump degenerate and pump nondegenerate SFWM processes on the two-photon correlation and its tunability. Then, as a benchmark application, a 10-user fully connected quantum key distribution network is established in a time-sharing way with triple pump lights. Our results provide a promising networking scheme for large-scale entanglement distribution networks owing to its scalability, functionality, and reconfigurability.

Numerical Study on the Potential Enhancement of Organic Terahertz Sources through Tilted Pulse Front Pumping

Organic crystals offer promising potential for THz generation, but face limitations in wavelength tunability and damage threshold. By applying tilted pulse‐front pumping to organic crystals an additional degree of freedom is introduced into the pumping conditions enabling a wider range of pumping wavelengths without compromising phase matching. Additionally, the lifespan of organic materials can be extended by using longer pumping wavelength and eliminate lower‐order multi‐photon absorption, allowing for higher pumping intensity without significant free‐carrier absorption, thus increasing the damage threshold. Simulations predict significant improvement for four out of six investigated crystals when tilted pulse‐front pumping is applied. By using volume phase holographic grating one can achieve pulse‐front tilt in organic crystals in collinear geometry with high diffraction efficiency. Design parameters are also presented.

Pressure characteristics and force analysis of pump turbine in variable-pressure outlet pump mode

A nonstationary numerical simulation was performed on the outlet pressure stabilization and periodic variable-pressure condition of a pump turbine model in the pumping condition. The objective was to dissect the flow mechanism and force characteristics of components within the outlet variable-pressure pumping condition of the pump turbine and to probe into the stability of the pump turbine under such working conditions. Additionally, the alterations in the runner state, pressure distribution, pressure pulsation, as well as the forces exerted on the runner and top cover during this process were analyzed. The results demonstrated that the internal pressure and flow pattern of the pump turbine under variable-pressure conditions fluctuated periodically in accordance with the outlet pressure. An augmented frequency of the outlet pressure variation led to an elevation in the amplitude of the internal pressure change. Nevertheless, a hysteresis difference was observed in the changes of the flow channel pressure and flow pattern. The pressure pulsation in the runner area was influenced by the runner rotation, static and dynamic interferences in the lobe-free area, and the unsteady flow induced by the alterations in the outlet pressure.

Dynamic and flow instability analysis during runaway process for a pump turbine

A power failure in the pump condition combined with the rejection of the guide vanes can cause the unit to runaway, which represents a dangerous transitional process for pumped storage power stations. This process is accompanied by intense oscillations in internal flow, pressure fluctuations, and changes runner forces. This study aims to clarify the unstable flow characteristics during the runaway process by focusing on the transient behaviour from the pump condition to the runaway condition in a high-head model pump turbine. The numerical calculation of the runaway speed and discharge are consistent with experimental test results. The results indicate that the dynamic curve is not continuously stable during the process but exhibits dynamic oscillations before reaching a relatively stable condition. Significant pressure fluctuations with high amplitudes are observed in the pump braking zone and close the runaway condition. Further analysis reveals low frequency, high amplitude pressure fluctuations within various flow components at frequencies smaller than the runner rotational frequency (fn). Axial forces demonstrate a linear correlation with the change rate of discharge. The dynamic evolution of the backflow vortex at the runner inlet is the main cause of significant fluctuations in the axial forces of the runner. The scale of the backflow vortex gradually increases as the discharge decreases, peaking in the pump braking zone. Entering the turbine operating condition, its intensity decreases to some extent but with a significantly expanded range. Near the optimal operating condition, the internal flow around the runner becomes smooth. As the discharge further decreases, the backflow vortex scale gradually increases, eventually forming a ring structure at the runner inlet. Further analysis indicates that the dynamic evolution of the backflow vortex at the runner inlet inevitably disrupts the flow, leading to a significant increase in pressure fluctuation amplitudes and more pronounced oscillations in axial forces.

An Mach-Zehnder interferometer refractive index sensor based on self-phase modulation effect in a tapered double-cladding highly nonlinear fiber

An Mach-Zehnder interferometer (MZI) sensor based on self-phase modulation (SPM) effect in a tapered double-cladding highly nonlinear fiber (DCHNLF) was proposed and experimentally verified for refractive index (RI) measurement. The DCHNLF was tapered and the SPM spectrum generated in its untapered region acted as the broadband light source for the sensor. The integration of the SPM effect and the RI detection not only simplified the structure of the sensor, but also enhanced its long-term stability and reliability. Since the effective RI of the outer cladding mode of the tapered DCHNLF was affected by the RI variation, a spectral shift would occur in interference spectrum between the core mode and the outer cladding mode. The tapering treatment enhanced the evanescent wave on the surface of DCHNLF, making the sensor more sensitive to external RI. In the external RI range of 1.3333 ∼ 1.3972, the sensor achieved an excellent sensitivity of 238.51 nm/RIU. In addition, the effect of average pump power and pump wavelength on the sensor performance were experimentally discussed. The results showed that the sensitivity was not affected by the pump condition. This MZI RI sensor has advantages of excellent performance, simple structure and easy fabrication, demonstrating broad application prospects in biomedical research, marine environment monitoring, and human health detection.

Performance Predictions of Solar-Assisted Heat Pumps: Methodological Approach and Comparison Between Various Artificial Intelligence Methods

The coefficient of performance (COP) is a crucial metric for evaluating the efficiency of heat pump systems. Real-time monitoring of heat pump system performance necessitates continuously collecting and processing data from various components utilizing multiple sensors and controllers. This process is inherently complex and presents significant challenges. In recent years, artificial intelligence (AI) models have increasingly been applied in refrigeration, heat pump, and air conditioning systems due to their capability to identify and analyze complex patterns and data relationships, demonstrating higher accuracy and reduced computation time. In this study, multilayer perceptron (MLP), support vector machines (SVM), and random forest (RF) are used to develop COP prediction models for solar-assisted heat pumps. By comparing the predictive accuracy and modeling time of the three models built, the results demonstrate that the random forest model achieves the best prediction performance, with a mean absolute error (MAE) of 2.42% and a root mean squared error (RMSE) of 4.01% on the train set. On the test set, the MAE was 2.35% and the RMSE was 3.84%. The modeling time for the RF model was 6.57 s.

Increasing the Wear Resistance of the Impellers of Electrical Centrifugal Submersible Pumps Through Repair

Objective: This research investigates the challenges of maintaining electrical submersible pumps (ESP) and develop effective repair techniques to enhance their reliability and efficiency. Theoretical Framework: The research draws upon theories and models related to pump maintenance, materials science, and corrosion prevention. Methodology: A case study approach was adopted, focusing on a Weir VTP submersible pump in continuous operation for 15 years. The pump's condition was assessed, and the root causes of erosion and corrosion were identified. Laser cladding with a TiC coating was applied to the damaged areas. Results and Discussion: The results demonstrated a significant improvement in the pump's wear resistance and overall efficiency following the laser cladding treatment. The TiC coating effectively mitigated the effects of erosion and corrosion, extending the pump's lifespan and reducing maintenance costs. Research Implications: The findings of this research contribute to the development of more effective maintenance strategies for submersible centrifugal pumps. The use of laser cladding with TiC coatings can be applied to other types of pumps and machinery operating in harsh environments. This research also highlights the importance of regular inspections and preventive maintenance. Originality/Value: This study provides a practical solution to the problem of erosion and corrosion in submersible centrifugal pumps. The application of laser cladding with a TiC coating is a relatively novel approach, offering a more effective repair method compared to traditional techniques. The results can be applied to improve the reliability and efficiency of pumps in various industries.

High-sensitivity and high-resolution triboelectric acoustic sensor for mechanical equipment monitoring

Traditional sensors for mechanical equipment monitoring often face challenges such as high cost, difficult installation and removal, and reliance on power sources. Herein, we introduced a polyvinylidene fluoride (PVDF) nanofiber membrane doped with BaTiO3 for constructing a triboelectric acoustic sensor (PB-TAS), innovatively designed for monitoring and recognizing the working conditions of mechanical equipment. This represents the first application of a triboelectric acoustic sensor for mechanical equipment monitoring. The PB-TAS demonstrates an ultra-broad frequency response range of 20–20,000 Hz, effectively covering the characteristic frequency spectrum (within 2000 Hz) during piston pump operation. It also exhibits extraordinarily sensitivity of 4.40 V Pa−1 at 85 dB, and ultra-high frequency resolution down to 0.1 Hz, enabling precise matching of the piston pump's acoustic characteristic frequencies. Integrated with deep learning techniques, the PB-TAS achieves real-time recognition of 15 distinct working conditions of a piston pump, with an impressive accuracy of 95.2 %. The PB-TAS, boasting exceptional sensitivity and frequency resolution, offers a cost-effective, miniaturized, self-powered, non-contact, and highly accurate solution for intelligent monitoring of hydraulic piston pumps.

Gain performance and thermal effects of Nd:Glass and Nd,Y:SrF2 crystal

The gain performance and thermal effects of Nd:glass (N31) and Nd,Y:SrF2 crystal are investigated and compared. The results show that, under the same pump conditions, Nd,Y:SrF2 can provide a small-signal gain similar to that of N31. The main advantages of Nd,Y:SrF2 are its weaker thermal effects and greater thermal-fracture limitations compared with those of N31. In this paper, the two gain media are compared in the form of rods whose diameter is 5 mm and length is 60 mm. The small-signal gain coefficients of N31 and Nd,Y:SrF2 are 1.39 and 1.46, respectively, at a pump energy of 1.5 J/1 Hz. The pump energy is set at 1.5 J/8 Hz to experimentally investigate their thermal effects. The thermal wavefront of N31 is 0.987λ at a repetition rate of 10 Hz, whereas that of Nd,Y:SrF2 is 0.679λ. In thermal destructive experiments, N31 fractured at an average pump power of 15 W (1.5 J/10 Hz), whereas Nd,Y:SrF2 fractured at a higher power of 27 W (1.5 J/18 Hz) owing to its excellent thermal conductivity, which is 7.28 times that of N31. These results indicate the potential of Nd,Y:SrF2 crystal as a gain medium for high-repetition-rate laser amplifiers.

Analysis of the Behaviour of the Hydraulic Fluid HM VG 32 and HV 32 at Different Operating Conditions of the Axial-Piston Pump

Analysis of the Behaviour of the Hydraulic Fluid HM VG 32 and HV 32 at Different Operating Conditions of the Axial-Piston Pump

Emission spectrum and photon statistics in cavity-QED system under incoherent pumping

The emission spectrum is an important tool for studying the properties and interactions of matter. By comparing analytical and numerical solutions, we validate the applicability and limitations of the low-excitation approximation. Here we show that even with a moderate pumping rate, rich multiple peaks can be observed in the emission spectrum which is the result of excitation of higher dressed rungs. Moreover, we find distinct photon distributions in the steady state under different pumping and coupling conditions and the physical mechanisms behind these phenomena are also illustrated. Additionally, we also show that the interference between the emission channels of the emitter and cavity can result in asymmetry of the emission spectrum of the whole system even if the emitter is resonant with the cavity field. Our findings can help in understanding the nonlinear characteristics and photon statistics in the cavity-QED systems.