Pump Start-up Research Articles

The Influence of Pre-Lift Gate Opening on the Internal and External Flow Characteristics During the Startup Process of an Axial Flow Pump

This paper focuses on a vertical axial flow pump and employs a 1D-3D coupling method to investigate the effects of different gate pre-opening angles on the internal and external flow characteristics of the axial flow pump during startup. Through comparative analysis, the following conclusions are drawn: In the study, a fully open gate is defined as 1, while a fully closed gate is defined as 0. When starting the axial flow pump with different valve pre-opening degrees, backflow occurs within the first 20 s of startup, and the backflow rate inside the pump gradually increases with the increase in the valve pre-opening degree. At a valve pre-opening degree of 0.6, the maximum backflow rate inside the pump reaches 5.89% of the rated flow rate. When starting the pump with the valve fully open, the maximum backflow rate reaches 10.98% of the rated flow rate, and the efficiency is affected by the backflow rate. The valve pre-opening degree has little impact on the axial force acting on the impeller during startup. When starting with a valve pre-opening degree of 0.6, the internal pressure difference in the pump is minimized. Within the first 20 s of startup, the internal pressure difference in the impeller is 28.96% higher and the flow velocity is 14.62% higher with valve pre-opening degrees of 0.8 and 1.0 compared to a 0.6 degree opening. During the initial stage of pump startup, with valve pre-opening degrees of 0.8 and 1.0, the pressure fluctuation amplitude inside the pump is minimal, with maximum relative amplitudes of only 0.621 and 0.525, which are 41.00% and 28.51% lower than the maximum amplitudes at 0 and 0.2 degrees, respectively. In summary, the peak pressure inside the pump is minimized when the valve pre-opening degree is around 0.8, while the pressure difference and flow velocity are relatively lower at a pre-opening degree of 0.6. It is recommended to start the pump with a valve pre-opening degree of around 0.6 to 0.8.

Operation of downhole pumps under sanding conditions

One of the unfavourable factors of downhole pumping equipment operation at the fields at the final stage of development is high content of mechanical impurities in the pumped fluid. Similar problems are observed in fields with friable, weakly cemented formations, the fracture products of which flow downhole, resulting in lower extraction rates, equipment damage and higher operating costs. In oil production practice various technological measures and technical means are used to reduce the negative impact of sand penetration - regulation and optimisation of pumping equipment operation mode to ensure a rational rate of fluid withdrawal, application of technical devices in the form of sand filters and sand anchors and others. However, these measures and recommendations, for the most part, work successfully in the modes of continuous operation of wells. With the growing number of oil fields at the final stage of development, the issue of sanding becomes more and more urgent, as due to low flow rate wells at such fields are often switched to the mode of periodic operation, which favours the formation of sand plugs in tubing above the pump due to sufficient time for sedimentation of mechanical impurities. This can lead to pump jamming or rod breakage during subsequent well pump start-up. The experience of using sand filters (frame, slotted and others) in the arrangement of downhole pumps has shown that it does not always effectively solve the problem of sand penetration due to clogging of their cells with mechanical impurities and increased hydraulic resistance. This negatively affects the pumping equipment operation due to the shift of characteristics into the zone of suboptimal modes with associated problems for the electric drive. This makes it necessary to carry out underground well workover with removal of deep well pumping equipment for replacement or washing of the filter in surface conditions, as due to their peculiarities in the well pump layout (the filter is located at the intake of the pumping section), washing in well conditions is not always possible. These problems require not only the creation of effective downhole devices to prevent sand ingress to the pump intake or devices to prevent sand plugs above it, but also acceptable in practice calculation methods for predicting the sedimentation time of mechanical impurities in tubing or determining the minimum required speed of upward oil flow for stable sand removal. These calculation methods would also allow to reasonably regulate the time of technological interruptions while waiting for the wells to start up in periodic operation modes or to predict the time of activation of sand control devices for discharging the sand accumulated above the pump. This is the subject of this article. As a result of calculation analysis it was established that the main factors affecting the sedimentation process of mechanical impurities in the well are the speed and mode of fluid movement, its viscosity, density and size of the impurities themselves. Moreover, the most sensitive for the calculation accuracy is to take into account the change of fluid viscosity as it moves along the tubing as a result of heat exchange and the change of dissolved gas content due to pressure drop. Although at this stage the proposed methodology does not take into account some factors that can make additional adjustments to the process of sand sedimentation, however, it allows to predict with acceptable accuracy the time of technological interruptions in the well operation to prevent the formation of sand plugs, or the rational mode of operation of pumping equipment, providing the necessary speed of upward flow in the pipe for sand removal.

Study on the Transient Flow Characteristics of Multistage Centrifugal Pumps during the Startup Process before System Operation

Multistage pumps are essential in emergency water supply, irrigation, and other systems undergoing unavoidable hydraulic transitions like pump startup and valve operations. These transitions cause rapid changes in impeller speed, flow rate, and pressure, destabilizing the internal flow field and impacting system reliability. To study transient flow characteristics, a numerical analysis of a three-stage pump was conducted, focusing on vortex identification, entropy production, and time–frequency pressure pulsation. Using the SST turbulence model, the simulation analyzed different start times and flow rate variations. Findings revealed that shorter startup times intensified transient effects, with the head increasing rapidly initially and then stabilizing. Vortex structures showed periodic development and dissipation. Entropy production rose with impeller speed, peaking higher with shorter startups. Blade passing frequency dominated pressure pulsations, with increased low-frequency pulsations as speed rose. During valve opening, flow stabilization accelerated with increasing flow rates, reducing amplitude and eliminating low-frequency components. This research aids the reliable operation of high-pressure pumping systems in energy storage.

MSR Transient Simulation and MSRE Transient Benchmark with SAM and SPECTRA

In recent years, there has been renewed interest in molten salt reactors (MSRs) for their potential advantages compared to reactors that rely on solid fuel. In response to such interest, many methods and codes have been developed to capture the unique features of MSRs. Among them, SPECTRA and SAM are two system analysis codes that have been enhanced to include MSR-specific modeling capabilities, including delayed neutron precursor drift and modified point kinetics equations. This paper discusses the efforts taken to verify and validate these features. A standard MSR system test problem was developed to verify and demonstrate the capability of SPECTRA and SAM on the MSR transient simulation. Sixteen transients were simulated. The results obtained from SPECTRA and SAM show good agreement. The Molten Salt Reactor Experiment transient experiments were reviewed and selected to validate the SPECTRA and SAM codes. The experiments included pump startup and coastdown tests at zero power, reactivity insertion tests at different power levels, frequency tests, and a natural convection test. The simulation results from SPECTRA and SAM show good agreement with the experimental data.

Numerical Study on Valve Closing Criteria during Pump-turbine Start-up on Pump Mode

Abstract Vibrations of exhaust pipes have been observed in some hydropower stations during the exhaust process of pump-turbine start-up on pump mode due to water ingress into the pipes. It may have a safety risk for the pump-turbine start-up process when exhaust pipes are operating under the compressed air-water two phase flow. Since the numerical simulation researches about pump start-up process have been rarely reported and the development of flow field in exhaust pipe is lack of quantitative cognition, it calls for an urgent need to supplement related works. In this paper, the transient full-channel two-phase numerical simulation research on the pump mode return water exhaust process of a pumped power station is carried out by Reynolds-Averaged Navier-Stokes approach. This work put emphasis on the characteristics of cone water level, runner torque and air speed in exhaust pipes after the compressed air released from the runner chamber. Then development laws and relationship with the exhaust valve closing timing are analysed and concluded. Results show that the cone water level, runner torque and air speed pulsation signal of exhaust pipes can be used as exhaust valve closing criteria, and the third criterion has the largest time margin.

A new approach to predict pump transient phenomena in Molten salt reactor Experiment (MSRE) by missing data identification and regeneration

Molten Salt Reactor Experiment (MSRE) is being extensively used for validating the computational tools for Molten Salt Reactors (MSRs). The pump transient tests were performed during the operation of MSRE to obtain the reactivity response to flow perturbation. The transient flow rate during this set of tests is required as input to predict the reactivity response. Since the primary loop of MSRE was not equipped with a flow rate meter, the transient flow rate, which is the crucial factor for the reactivity change in MSRE, is missing. Achieving an accurate simulation of the reactivity response to the MSRE pump transient tests necessitates a precise estimation of the transient flow rate.This paper endeavors to reconstruct the missing flow rate with the aim of offering a valuable input for simulating reactivity responses in the pump transient test series. In order to obtain an accurate transient flow rate, we employed a centrifugal pump transient model based on the affinity laws and solved the model for the MSRE secondary pump to validate the underlying assumptions of the model. In addition, we constructed the homologous pump head curves based on the water test data for the same purpose. The affinity law approximation is proved to be adequate in predicting the MSRE pump startup transient with the root-mean-square error (RMSE) in the normalized flow rate to be 0.03. On the other hand, for the MSRE pump coastdown transient, the preliminary results indicate that neither the affinity law approximation nor the homologous head curve is sufficient to provide acceptable predictions. To overcome this noticeable modeling deficit, we propose an innovative approach based on a straightforward data mining technique to regenerate the MSRE pump coastdown homologous relations using the measured data of the secondary pump. These relations are transferred to the primary pump and used to simultaneously solve for the impeller speed and the flow rate of the pump in the primary pump coastdown. With the new approach, the estimated RMSE in the normalized pump speed for the primary pump coastdown is reduced 0.0052. This excellent agreement validates the accurate calculations for the flow rate during the pump coastdown transient. We also performed an uncertainty analysis to quantify the confidence interval of the predicted quantities, which further justifies the robustness of the proposed approach.

Influence of start-up modes on the noise characteristics of mixed-flow pump during start-up process

The evolutions of noise characteristics of the pump have significant implications for monitoring the stability of the mixed-flow pump (MFP) start-up process. To investigate the variations in noise characteristics under different start-up modes and start-up times, the noise, shaft vibration and pressure pulsation of MFP under linear and nonlinear start-up modes were collected by an acoustic and vibration experimental system. Subsequently, an analysis was conducted based on acoustic signal processing methods. The results show that the high-amplitude sound pressure under different start-up modes appears in the later stage of start-up, and the time for the high-amplitude noise region to appear is the shortest under the concave exponential (CCEF) start-up mode. The shock noise under the CCEF start-up mode is relatively small, indicating that this start-up mode is conducive to avoiding severe mechanical collisions and shocks during the start-up process. The highest A-weighted sound pressure level (SPL) of the noise under different start-up modes appears at the center frequency of 250 Hz, and the CCEF start-up mode brings about the smallest total effective SPL. Adopting the CCEF start-up mode and extending the start-up time is beneficial to avoid severe mechanical collisions, reduce the SPL in each frequency band, and weaken the continuous impact of noise on the environment during the MFP start-up process. In addition, CCEF start-up modes can effectively reduce the tone of the noise during the start-up of the MFP.

Research of static and dynamic characteristics of a process system ‘electric drive-fluid-handling machine-pipeline’

<p>The paper offers the obtained quantitative assessment of the performance and energy parameters of a process system composed of an asynchronous motor, a fluid-handling machine and a pipeline when using two methods of performance control, in particular, throttling and speed control methods. Taking into account nonlinearity of mathematical representation of fluid-handling machines and asynchronous drive motors, the starting conditions were analysed using nonlinear differential calculus. The calculations for the models were performed using the MATLAB software package. Transient profiles of flow and head, stator current, angular frequency and torque of an asynchronous motor were obtained at pump startup and control of pump capacity. It has been found that the developed mathematical model of a process system composed of an asynchronous motor, a fluid-handling machine and a pipeline allows obtaining quantitative estimation of the performance and energy parameters of the unit when using two methods of the pump capacity control. The use of frequency method allows to decrease the pump rotation speed and significantly reduce the power consumed by the unit and provide energy-saving mode of operation, the economic efficiency of which depends on the range of feed control.</p>

Numerical Investigation of Guide Vane Hydraulic Torque Characteristics of a Pump Turbine in Pump Mode

This study performs numerical simulations to investigate the hydraulic torque characteristics of a pump turbine at different guide vane openings in pump mode. The SST k-ω turbulence model is utilized to simulate the flow field at guide vane angles from 1° to 21°. The simulation results reveal that the overall hydraulic torque shows a decreasing trend as guide vane opening increases. However, significant asymmetry of hydraulic torque exists among different guide vanes at certain openings. This asymmetry highly correlates with the large vibration observed during pump start-up in the field test. By analysing pressure contours and velocity streamlines at openings of 3°, 9° and 17°, the causes for torque asymmetry are explored in depth. The primary factors are identified as circumferential flow non-uniformity, distinct flow discharge tendencies between boundary guide vanes, and reverse flow towards upstream stay vanes. The research findings provide important insights into the hydraulic torque characteristics of pump turbines at off-design conditions, and offer valuable guidance for the optimal design and stable operation of pump turbines in pump mode.

Analysis of internal flow characteristics of a multistage pump during start-up

In order to study the transient characteristics during the startup process of a multi-stage pump, the Flowmaster software was used to obtain the rotating speed and flow characteristic curves of the pump under different valve openings, and analyze its internal flow and structural characteristics based on numerical simulation. The study results indicate that the time required for the flow to reach a steady state lags significantly behind the time required for the rotational speed to reach a stable state during the initial stage of pump start-up. By comparing the pressure distributions of a multistage pump under quasi-steady state and transient conditions, it can be seen that the internal flow field evolution of the pump under transient condition during the startup process lagged behind that under quasi-steady state condition, which makes using quasi-steady state laws were not suitable for describing the changes in transient flow field. The deformation law of the first-stage impeller under stable and start-up conditions was similar. The impact of increased flow rate on deformation was relatively weak and the difference in deformation values under different flow rates was relatively small under transient condition.

Pressure-adjusted venting eliminates start-up delays and compensates for vertical position of syringe infusion pumps used for microinfusion.

Microinfusions are commonly used for the administration of catecholamines, but start-up delays pose a problem for reliable and timely drug delivery. Recent findings show that venting of the syringe infusion pump with draining of fluid to ambient pressure before directing the flow towards the central venous catheter does not counteract start-up delays. With the aim to reduce start-up delays, this study compared fluid delivery during start-up of syringe infusion pumps without venting, with ambient pressure venting, and with central venous pressure (CVP)-adjusted venting. Start-up fluid delivery from syringe pumps using a microinfusion of 1mL/h was assessed by means of liquid flow measurement at 10, 60, 180 and 360s after opening the stopcock and starting the pump. Assessments were performed using no venting, ambient pressure venting or CVP-adjusted venting, with the pump placed either at zero, -43cm or + 43cm level and exposed to a simulated CVP of 10mmHg. Measured fluid delivery was closest to the calculated fluid delivery for CVP-adjusted venting (87% to 100% at the different timepoints). The largest deviations were found for ambient pressure venting (-1151% to + 82%). At 360s after start-up 72% to 92% of expected fluid volumes were delivered without venting, 46% to 82% with ambient pressure venting and 96% to 99% with CVP-adjusted venting. CVP-adjusted venting demonstrated consistent results across vertical pump placements (p = 0.485), whereas the other methods had significant variances (p < 0.001 for both). In conclusion, CVP-adjusted venting effectively eliminates imprecise drug delivery and start-up delays when using microinfusions.

Water Hammer Characteristics and Component Fatigue Analysis of the Essential Service Water System in Nuclear Power Plants

Due to the operation conditions and system characteristics of the essential service water system of nuclear power plants, water hammer pressure fluctuates in each transient process. In order to further analyze the characteristics of the water hammer and the harm this can cause to system equipment, this paper uses one-dimensional transient computing software to simulate the water hammer characteristics of the system under different operating conditions and at different water levels. The instantaneous pressure data of water hammer in the essential service water system were used as input conditions for fatigue analysis of components, and the fatigue damage of at-risk parts was calculated. The results show that the pressure fluctuation due to single pump outage is greater than that due to single pump start-up and the start-up of double pumps. The maximum pressure of the system under the design flood level is greater than that of other water levels, and the maximum pressure of the system under each working condition is 3.87 MPa. The most at-risk part of the system pressure fluctuation is the return valve, followed by the valve after a bend in a pipe and the tee pipe fitting. In the whole system, the joint of the main branch of a tee pipe experiences the greatest fatigue damage, and the theoretical fatigue life is 127.55 years.

Influence of Blade Trailing-Edge Filing on the Transient Characteristics of the Centrifugal Pump during Startup

During the startup process of a centrifugal pump, the vibration and noise problems caused by unsteady flow are the focus of attention, and pressure pulsation is one of the main reasons for this problem. In the current research, a special impeller with blade pressure side trimming was proposed to reduce the strong pressure pulsation phenomenon during the startup process of centrifugal pumps. This article uses numerical simulation methods to simulate three typical blade trailing edges: original trailing edge (OTE), pressure side long linear (LLPS), and pressure side short linear (SLPS), and verifies them with experimental results. The results indicate that although the head of the centrifugal pump after filing has been reduced, its efficiency has been improved to a certain extent. Thirteen monitoring points were set up near the impeller outlet circumference and volute tongue to analyze the changes in pressure pulsation, verifying that blade trimming has a significant inhibitory effect on pressure pulsation during the startup of centrifugal pumps. The average maximum pressure pulsation amplitude of all monitoring points decreased by 32.23%, and the maximum pressure pulsation amplitude decreased by 56%. Blade trimming can affect the internal flow field distribution of centrifugal pumps. By analyzing the static pressure distribution, velocity streamline distribution, and vorticity distribution at the middle interface of three different impellers during startup, it was verified that there is a close relationship between pressure pulsation and unsteady flow structure during startup. The final conclusion is that blade trimming has a significant inhibitory effect on the pressure pulsation of the centrifugal pump during startup, and the impeller outlet vorticity is significantly reduced. The scheme proposed in this study has far-reaching prospects in the design of low noise centrifugal pumps.

Effect of central venous pressure on fluid delivery during start-up of syringe infusion pumps for microinfusion.

Intravenous administration of highly concentrated and potent drugs at low flow rates is common practice, particularly in critically ill children. Drug delivery during infusion start-up can be considerably delayed by intrinsic factors of syringe infusion pump assemblies. The impact of central venous pressures on the course of start-up fluid delivery of such microinfusions remains unknown. Infusion volumes delivered after activation of the start button in a conventional 50 mL syringe infusion pump assembly equilibrated (representing classical in vitro testing) and not equilibrated (representing real clinical conditions) to central venous pressure levels of 0, 10 and 20 mmHg at a set infusion flow rate of 1 mL/h were measured using a fluidic flow sensor. The experimental setup mimicking real life conditions demonstrated considerable differences in fluid delivery during pump start-up depending on central venous pressure. A central venous pressure of 0 mmHg resulted in massive fluid delivery at infusion start-up, while central venous pressure levels of 10 and 20 mmHg resulted in retrograde flows with related mean (95% CI) zero-drug delivery times of 3.22 (2.98-3.46) min and 4.51 (4.33-4.69) min, respectively (p < .0001). Depending on central venous pressure level, connection and starting a new syringe pump can result in significant antegrade or retrograde fluid volumes. In clinical practice, this can lead to hemodynamic instability and hence requires clinical alertness. Further research and methods to improve start-up performance in syringe infusion pump systems are desirable.

Cumulative Fatigue Damage of Small-Bore Piping Subjected to Flow Induced Vibration

The structural fatigue of a vertically oriented small-bore connection due to flow induced turbulence emanating from an upstream piping manifold is experimentally investigated. Dynamic strain measurements are taken at two perpendicular locations on a small-bore connection and the method of rainflow counting is used to determine the cumulative damage incurred. A number of factors is investigated and their influences on the cumulative damage are explained. These include the effects of (1) single phase and multiphase flow, (2) the upstream flow path through the manifold, and (3) steady-state and transient conditions. From the experimental analysis, key observations that may be useful to piping designers and engineers are reported. For instance, for single-phase water, the largest bending stresses are due to the out-of-plane vibration of the small-bore piping, whereas the pulsating characteristics of the single-phase air and multiphase flow result in significantly larger in-plane bending stresses. It is also observed that under certain manifold outlet conditions, transient effects upon pump start-up can produce more than 300 times the cumulative fatigue damage compared to steady-state operation. As part of this study, the finite element method is also used to investigate the influence of piping support stiffness on the fatigue life of a small-bore connection. Through a series of parametric analysis, it is demonstrated that there exists a minimum support stiffness for which the fatigue life of a small-bore connection excited by flow-induced vibration, achieves its upper bound value.

METHOD OF QUALIFICATION OF MODERNIZATION OF ACTIVE SAFETY SYSTEMS TO PREVENT HYDRODYNAMIC INSTABILITY

The main reason for the hydrodynamic instability in the start-up mode of the pumps of the high-pressure reactor makeup system is related to the inertial delay in the reaction of the pump head and rate to rapid changes in operating parameters (flow rates, pressure, etc.).The consequences of the hydrodynamic instability in the high-pressure reactor makeup system can be: violation of the conditions for compensating the flow of possible leaks; hydro- and thermal "shocks" and other negative effects in the operating and emergency modes of the reactor.The control armature does not prevent the conditions for the hydrodynamic instability in the transient mode of pump start-up.&#x0D; An alternative approach to modernizing the high-pressure reactor makeup system with damping devices is proposed. Based on the performed modelling of the modernized system, the conditions and constructional and technical requirements for the prevention of the hydrodynamic instability in the transient modes of pump start-up were determined.

Optimal pump-valve coupling operation strategy of complex long-distance water-conveyance systems based on MOC

Transient simulation is crucial for protecting complex pump-valve water conveyance pipeline systems from extreme pressure and water level oscillations. In order to numerically simulate the transient response in a complex pump-valve water conveyance system, a transient flow calculation model was established adopting the method of characteristics (MOC). Based on the proposed model, the transient pressure and the water level fluctuation process were numerically predicted under steady-state operation state, and then the results were compared to the actual measured data. Due to the good agreement between the simulation results and the actual measured data, the model established based on MOC is effective and practical. 41 operational scenario switching schemes were designed according to the uniform experimental design, to study the operation sequence and time differences of pumps and valves during operational scenario switching state. The results show that the operational time interval has a major impact on the transient process under the operational scenario switching state in complex pump-valve systems, and also indicate that delayed pump startup can alleviate the pressure extremum of pipeline systems and effectively control water level fluctuation of such systems. In addition, this study points out the optimal operational sequence and the maximum and minimum allowable time intervals between the pump and the valve under operational scenario switching state in such systems. Finally, an optimized joint operation scheme for pumps and valves with simple operation and small water-level oscillation were proposed under operational scenario switching state.

Influence of pump start-up mode on the stability of mixed-flow pumps

Influence of pump start-up mode on the stability of mixed-flow pumps

10 clinical tips for advancing patient safety when using syringe pump systems for microinfusion intravenous drug therapy.

10 clinical tips for advancing patient safety when using syringe pump systems for microinfusion intravenous drug therapy.

Implementation of barcode medication administration (BMCA) technology on infusion pumps in the operating rooms

BackgroundMedication administration errors (MAEs) are a major cause of morbidity and mortality. An updated barcode medication administration (BCMA) technology on infusion pumps is implemented in the operating rooms to automate...