Pressure Pulsation Characteristics Research Articles

Investigation on the pressure pulsation characteristics in a twin-screw multiphase pump

A three-dimensional gas–liquid two-phase transient numerical model for a twin-screw multiphase pump based on dynamic grid technology was established and validated with experiments. The pump's simulated pressure distributions, velocity fields, and pressure pulsations were analyzed to reveal the mechanisms of pressure transmission and pressure pulsation characteristics. The results indicated that the flow rate of the pump fluctuated twice due to the discharge of the male and female rotors in one cycle. As the inlet gas volume fractions increased, the flow rate decreased, but the pressure pulsations increased. At the engaging positions of the two rotor tips, a sudden pressure drop happened due to the combined effect of both tooth-tip and tooth-flank leakage. When the discharge port opened, the backflow happened; the flow rate and the pressure in the discharge chamber decreased, but the pressure in the working and suction chambers increased. When the suction port closed, a slight compression of the fluid in the low-pressure working chamber occurred, causing a pressure increase in the working chamber. The working chambers inhaled and discharged once in one cycle, so the first harmonic of pressure pulsations at the suction and discharge chamber was two times the running speed. The transient flow due to the simultaneous closing and opening of the suction and discharge ports at both sides of the male and female rotors generated a harmonic of four times the running speed. This study would help to improve the operational stability of twin-screw multiphase pumps.

Numerical Study of Low-Specific-Speed Centrifugal Pump Based on Principal Component Analysis

The characteristics of pressure pulsations in centrifugal pumps have attracted considerable attention. In this study, principal component analysis is used to discuss the pressure pulsations in a centrifugal pump with a low specific speed, and the primary causes for these pressure pulsations are analyzed in conjunction with experimental results. The results indicate that principal component analysis effectively separates the primary modes that influence the flow field characteristics. An excessive wrap angle results in the formation of a backflow vortex on the working face of the blade. Obvious stratification of the zero-order modal pressure indicates that the geometric structure of the impeller is rational and that the transient flow field is stable. The second- and third-order modes are conjugates, and their dominant frequency coincides with the dominant rotating frequency of the impeller, indicating that the pulsations of a single channel are the primary component of the pressure pulsations. The primary frequency (148.54 Hz) of the pressure pulsations at monitoring points distributed across the volute is three times the rotational frequency (49.51 Hz) of the impeller. The different positions and sub-frequencies of the monitoring points mean that the principal component analysis can effectively identify the impeller-induced sub-frequency difference.

Transient Flow-Induced Stress Investigation on a Prototype Reversible Pump–Turbine Runner

Pump–turbine units with high heads are subjected to strong pressure pulsations from the unsteady transient flow in fluid channels, which can produce severe vibrations and high stresses on the pump–turbine structural components. Therefore, reducing transient flow-induced stresses on prototype reversible pump–turbine units is an important measure for ensuring their safe and efficient operation. A high-head prototype reversible pump–turbine with a rated head of 440 m was used to investigate the transient flow characteristics and the flow-induced-stresses in this study. First, the flow passages of the pump–turbine unit and the structure of the reversible pump–turbine runner were constructed with CAD tools. Next, CFD simulations at the full load were performed to investigate the pressure pulsation characteristics of the pump turbine in both the time domain and the frequency domain. After this, the pressure files calculated by the CFD were exported and applied to a finite element model of the pump–turbine runner to calculate the transient flow-induced dynamic stresses. The results show that the pressure pulsations in the flow passage are closely related to the rotational speed, the guide vane number, and the runner blade number of the pump–turbine unit. The maximum flow-induced stresses on the pump–turbine runner at the full load were below 2 MPa and lower than the allowable value, which reveals that the designs of the pump–turbine runner and the flow passage are acceptable. The conclusions can be used as a reference to evaluate the design of high-head pump–turbines units. The approaches used to carry out the transient flow-induced stress calculations can be applied not only to pump–turbines units but also to other types of fluid turbomachinery such as pumps, turbines, fans, compressors, turbochargers, etc.

Study on partial load vortex and pressure pulsation characteristics of Francis turbine

Abstract Under partial load condition of the Francis turbine, problems such as hydraulic vibration, noise, and high amplitude pressure pulsation that endanger the safe and efficient operation of the unit are inevitable during the transient process. Based on dynamic grid technology and CFD technology, unsteady numerical simulation was conducted for the closing process of the active guide vane from 54% opening to 38% opening, and the evolution characteristics of internal vortex and pressure pulsation were analyzed. The results show that there is always a vortex structure at the crown of the runner during the transition process of variable load. Because of the vortex structure, a “banded” low-pressure zone appears on the suction surface of the blade, which gradually approaches the lower ring of the runner as the vortex structure develops. The analysis of the pressure signal in the runner region shows that the pressure coefficient on the suction surface fluctuates greatly due to the influence of the distribution position of the vortex structure, and the evolution of the vortex structure from continuous to local fracture will lead to a sudden increase of the pressure coefficient. In addition, the frequency components within the runner domain include the frequency of the movable guide vanes passing through the blade and the low-frequency components caused by the evolution of eddy currents within the runner.

Analysis of stability characteristics of pump-turbine in a pumped-storage power station with large head variation

Abstract The head variation is a key index of pumped storage power station, which is related to the operation stability of pump-turbine. The greater the head variation, the more difficult it is to ensure the operation stability of the unit. In this paper, the pressure pulsation of the pump-turbine with a large head variation is measured, and its amplitude and frequency characteristics are analysed. The prototype results are compared with the model test results. Similarities and differences of the pressure pulsation characteristics between the prototype and model are obtained. At the same time, the vibration characteristics of the prototype unit is measured, and the correlation analysis of the pressure fluctuation characteristics and the head variation is made. Then, the stability characteristics of pump turbines in the pumped storage power station are obtained. It guides the operation of the power station.

Numerical Investigation of Rotor and Stator Matching Mode on the Complex Flow Field and Pressure Pulsation of a Vaned Centrifugal Pump

The match of rotor and stator blades significantly affects the flow field structure and flow-induced pressure pulsation characteristics inside the pump. In order to study the effects of the rotor and stator matching mode on the complex flow field and pressure pulsation of a centrifugal pump with a vaned diffuser, this paper designs three different vaned diffusers (DY5, DY8 and DY9) and uses the DDES (Delayed Detached Eddy Simulation) numerical method combined with structured grids to simulate the unsteady flow phenomena of the model pump under rated conditions. The results show that, under different rotor and stator matching modes, the pressure pulsation spectrum is dominated by the blade passing frequency and its harmonics. The matching mode of the rotor and stator significantly affects the time–frequency domain characteristics of the pressure pulsation inside the pump, and it is observed that the pressure pulsation energy of vaned diffusers with more blades is significantly smaller than that of fewer-blade vaned diffusers in comparison to the energy of the pressure pulsation at the blade passing frequency and within the 10–1500 Hz frequency band. Combined with the distribution characteristics of the complex flow field inside the pump, it can be found that increasing the number of vaned diffuser blades can reduce the energy of flow-induced pressure pulsation, improve the distribution of high-energy vortices in the interaction zone and stabilize the flow inside the centrifugal pump effectively.

Research on pressure pulsation characteristics of a pump-turbine in pump mode with rotating stall: Focus on the broadband frequency

To investigate the adverse effects of rotating stalls on the pressure pulsation characteristics of a pump-turbine in pump mode, an unsteady numerical simulation was carried out by applying the partially averaged Navier–Stokes turbulence model. The numerical methods were carefully verified, and the onset flow rate of the hump at the performance curve and heads were in good agreement with the experimental data. The rotating stall appeared in the guide vane when the flow rate ranged from 0.514 to 0.887 times the best efficiency point (QBEP), with a frequency of 11.7% times the rotational frequency. In the period of a rotating stall, a sudden intensive pressure pulsation in the guide vane channel was observed and named as the component of the broadband frequency, and its corresponding flow mechanism was explained as the vortex evolution between the adjacent guide vane blades based on the dynamic mode decomposition technology. There were three distinct characteristics of broadband frequency: (i) intermittent occurrence when the rotating stall cell propagated to the current flow channel, (ii) a wide range of the frequency varying with flow rate, (iii) a considerable amplitude, e.g., reaching 21.1%–42.2% times that of the rotating stall frequency. In addition, both the frequency range and amplitude of the broadband frequency gradually decreased as the flow rate increased to 0.887QBEP. This study clarified the internal flow mechanism and frequency behaviors of a sudden intensive pressure pulsation if a rotating stall occurred, which was important to assess the stability of pump-turbine units.

Investigations of the Formation Mechanism and Pressure Pulsation Characteristics of Pipeline Gas-Liquid Slug Flows

The pipeline system is widely used in marine engineering, and the formation mechanism and flow patterns of two-phase slug flows are of great significance for the optimal design of and vibration prevention in a complex pipeline system. Aiming at the above problems, this paper proposes a modeling and solving method for gas-liquid slug flows. First, a VOF-PLIC-based coupling gas-liquid slug flow transport model is conducted. Second, to reduce the fuzzy boundary between the gas-liquid coupling interfaces, an artificial compression term is added to the transport equations, and the formation and evolution mechanism of severe slugging flow in piping systems is investigated. The pressure pulsation and gas content characteristics of the gas-liquid coupling process are explored. Research results found that the slugging phenomenon occurs at the gas-liquid interface, where liquid slugging frequency reaches its peak. The pipeline system has prominent periodic characteristics of the slugging phenomenon, and the period decreases when the gas-phase converted speed rises; pressure fluctuation amplitude increases, and the gas-phase velocity change is the inducing factor for the drastic change of pressure fluctuation. The research results can offer theoretical references for optimal designs of and vibration prevention in marine pipeline systems.

Effect of suction temperature on the internal flow characteristics of hydrogen circulation pump

This paper explores the effects of suction temperature (ST) on the internal flow and pressure pulsation characteristics of a roots hydrogen circulation pump (HCP). The study analyzes the suction and discharge chamber pressure pulsation, as well as the inlet and outlet flow pulsation, at different STs. The research finds that an increase in ST leads to a decrease in the amplitude and fluctuation intensity of the pressure pulsation in both suction and discharge chambers. Moreover, the average flow rate of the HCP decreases with increasing ST, while the frequency and waveform remain unchanged. The maximum and minimum values of the inlet flow pulsation decrease, while the maximum value of the outlet flow pulsation decreases, and the minimum value increases, indicating a reduction in fluctuation intensity. The turbulent energy within the discharge and transport chambers also changes with increasing ST. The inter-lobe leakage flow (ILF) is slightly affected by ST, while the radial leakage flow (RLF) and axial leakage flow (ALF) exhibit slight increases. Overall, these findings reveal the importance of considering ST as a critical design parameter for optimizing the performance and stability of the HCP.

Pressure Pulsation Characteristics on the Bulb Body of a Submersible Tubular Pump

Submersible tubular pumps are an ideal choice for pump stations that require high flow rates and low lift. These pumps combine the unique features of submersible motors with axial flow pump technology, making them highly efficient and cost-effective. They have found extensive applications in China’s rapidly developing water conservancy industry. In this research, we focus on investigating the pressure pulsation characteristics of the internal bulb body in a specific pump station project in China. To conduct our analysis, we utilize a model of the submersible tubular pump and strategically position 18 monitoring points. These monitoring points cover various sections, including the impeller inlet and outlet, guide vane outlet, as well as the inlet, middle, and outlet sections of the bulb body segment. To calculate the unsteady flow of the system, we employ numerical simulation techniques. By combining the outcomes of model tests, we determine the pressure pulsation characteristics. The comparison of results reveals a remarkable similarity between the efficiency–head curves obtained from the numerical simulation and the model test. While the model test yields slightly higher head results, the numerical simulation indicates slightly higher efficiency values. This finding lends strong support to the reliability of numerical simulation results, which can provide valuable insights for the design and optimization of submersible tubular pumps. Overall, submersible tubular pumps demonstrate their suitability for pump stations with high flow rates and low lift requirements. The study of pressure pulsation characteristics within the bulb body contributes to a better understanding of their performance and facilitates their further application in the field of water conservancy engineering.

Hydraulic performance improvement of a two-way pumping station through bell mouth shape design

A two-way pumping station is a specialized device that facilitates bidirectional water pumping and drainage. The pressure pulsation characteristics of two-way pumping stations have emerged as a prominent research focus in the field of hydraulic engineering. In this work, with the aim of systematically proposing optimization measures to ensure operational stability, a transient numerical simulation is conducted to elucidate the influence mechanism of the suspension height of the bell mouth (SHb) on the internal flow field and pressure pulsation of a two-way pumping station. High-precision experiments are performed to compare time-frequency domain characteristics under different SHb using a continuous wavelet transform (CWT). The findings indicate that an appropriate reduction in SHb effectively reduces unstable flow and pressure pulsation within the inlet conduit, consequently reducing the pressure pulsation of the impeller. With a reduction in SHb, the influx of low-velocity backflow into the bell mouth is prevented and the generation and propagation of suction vortices are suppressed. However, the reduction amplifies the flow impact between the mainstream flow and the bell mouth wall. The spatial distribution of the pressure pulsation is also examined, and it is found that a reduction in SHb increases the pressure pulsation intensity on the side facing the incoming flow and on the rear side, while the mainstream area tends to exhibit stability. In terms of time-frequency domain characteristics, a reasonable reduction in SHb leads to improved circumferential uniformity of the impeller inflow and the effective suppression of low-frequency disturbances.

Influence of the Trailing Edge Shape of Impeller Blades on Centrifugal Pumps with Unsteady Characteristics

The flow field structure and pressure pulsation characteristics in two series of trailing edges of a centrifugal pump are investigated using the SST k-w turbulence model. Series 1 involves varying the impeller exit angle, and Series 2 involves varying the impeller exit shape. The entropy generation rate analysis method is used to evaluate the numerical simulation results. Vortex cores within the flow field are identified by applying the Ω criterion. The influence of different trailing edge configurations on the energy loss characteristics of the pumps is explored. The dynamic mode decomposition (DMD) method is used to analyze pressure pulsations at the volute considering unsteady flows in centrifugal pumps with different trailing edge shapes. The findings suggest that different trailing edge shapes can be used to adjust the energy loss proportions in various components of the pump. In Series 1, the efficiency remains nearly constant with changes in the outlet angle on both sides of the trailing edge. In Series 2, the efficiency is enhanced by 1.18% with the elliptical edge shape on both sides (EBS) compared to the original trailing edge (OTE) shape. In Series 1 and Series 2, greater entropy generation rates are accompanied by greater pressure pulsations at the pump outlet. The DMD results demonstrate a noticeable impact of the different trailing edges on the pressure distribution of various modes within the volute. Moreover, the impeller outlet pressure inhomogeneity coefficient changes under different modes. This study holds great significance for selecting the appropriate trailing edges for centrifugal pumps.

Unsteady internal flow characteristics study of a hydrogen circulation pump under different pressure differential conditions

The purpose of this paper is to investigate the flow and pressure pulsation characteristics of hydrogen circulation pump under varying pressure differences. A dynamic mesh technology was employed to conduct an unsteady numerical simulation of the interior of the hydrogen pump. The pressure pulsation within the pump cavity area was analyzed using fast Fourier transform, and the unevenness of pressure and flow inside the pump under varying pressure differential conditions was specifically studied. The results reveal that interference between dynamic and static in the pump cavity, caused by meshing clearance between rotors and radial clearance between the rotor and pump cavity, leads to pressure pulsation peaks occurring at twice the rotational frequency at all monitoring points. Additionally, as the pressure difference increases, the exhaust flow rate at the outlet of the pump cavity decreases from 49.237 m3/h to 12.392 m3/h, while volumetric efficiency decreases from 85.95% to 32.3%.

Pressure pulsation of pump turbine at runaway condition based on Hilbert Huang transform

Pumped storage is an important component of electrified wire netting. The safe and stable operation of pump turbines is extremely important. Among them, pressure pulsation is one of the main causes of pump turbine vibration. The characteristics of pressure pulsation are relatively complex, and it is difficult to directly observe their temporal changes using commonly used FFT methods. The division of frequency characteristics is often vague. Meanwhile, it is difficult to explain some phenomena such as frequency doubling. This article focuses on a certain model of pump turbine and uses SST model to numerically simulate the runaway condition of the pump turbine. And the Hilbert Huang transform method is used to analyze the pressure pulsation in the vaneless region and draft tube. The results show that the main characteristic frequencies of the vaneless region are blade passing frequency 112.5 Hz and rotational frequency 12.5 Hz. The main characteristic frequencies of the draft tube are vortex rope frequency near 3 Hz which energy ratio is up to 50%, rotational frequency, and blade passing frequency. The pressure pulsation characteristics in the vaneless region have changed from a complex composition of double blade passing frequency and rotational frequency to a distribution dominated by blade passing frequency. In the passage of the guide vane, the pressure pulsation is almost only characterized by blade passing frequency. The frequency characteristics of the vaneless region between the runner and the guide vane become complex again. Meanwhile, the results show that the characteristic frequencies of the vaneless region and the draft tube propagate upstream and downstream.

Pressure Pulsation Characteristics of a Self-Priming Pump under Typical Operating Conditions

To investigate the pressure pulsation characteristics of self-priming pumps under different flow conditions, Fluent 19.2 software was used to numerically calculate the internal flow inside a self-priming pump by means of the RNG k-ε model. The pressure pulsation characteristics, as well as the standard deviation in the volute and impeller domains, were analyzed under different flow conditions. As a result, under rated- and high-flow conditions, the monitoring points in the volute channel have obvious periodic patterns, and the peak pressure pulsations all occur in the octave band of the blade frequency. The pressure pulsation amplitude is larger under the high-flow condition than in the other two conditions. The monitoring points L1 and L5 on the impeller channel centerline are located near the impeller’s inlet and outlet, respectively, so the pressure pulsations are larger than other monitoring points.

Research on the internal pressure pulsation characteristics of reactor coolant pump under non-uniform inflow

Research on the internal pressure pulsation characteristics of reactor coolant pump under non-uniform inflow

Structure design on a new type of coupled impactor

Improving drilling efficiency and reducing drilling cost are new challenges for deep drilling. Based on this, a coupling impactor is designed by applying the principle of hydraulic pulse pressurization and axial impact. Based on the impactor compression structure and principle, the fluid flow equation of the drilling fluid flowing through the compression mechanism and the mechanical balance equation of the piston body are established in order to study the pressure pulsation characteristics of the coupled impactor fluid.

Study on unsteady characteristics of the reactor coolant pump under non-uniform inflow

The primary circuit of a nuclear power plant contains a steam generator (SG) and two vertical reactor coolant pumps (RCPs). Two RCPs are installed at the bottom of the SG. The structure of the channel-head of the SG is special, which leads to uneven flow from the RCP inlet and affects the operation performance of the pump. Taking the RCP of the third-generation reactor as the research object, the unsteady characteristics of the third-generation RCP under non-uniform inflow conditions were investigated using CFD, and the pressure pulsation characteristics inside the RCP were mainly studied. A series of monitoring points were set at the channel of the channel-head, impeller, diffuser and casing section respectively to study the influence of non-uniform flow on the pressure fluctuation and radial force distribution of the RCP. The results show that non-uniform inflow can cause instability in pressure fluctuations in the “throat” region of the channel-head. The interaction between the impeller and diffuser can cause pressure pulsation from the impeller outlet to the diffuser inlet, potentially impacting the safe and stable operation of the RCP. This research provides certain theoretical support for the design of RCPs under the condition of non-uniform inflow.

Effect of different blade number and thickness on performance of micro-turbine

At present, due to its special operating environment and operating conditions, there are few relevant theoretical studies and numerical simulation studies on micro-turbines. Therefore, the use of simulation technology to explore the internal flow law of micro-turbines is of great significance for the design optimization guidance of micro-turbines. The research method of this paper is through CFD software, using SST k-ω algorithm model. This paper studies the efficiency and output of micro-turbine with 8 blade numbers of 13,15,17,19,21,23,25 and 28, as well as the efficiency and output of micro-turbine with thickness of 12mm, 12.5mm, 13mm, 13.5mm and 14mm. The internal flow field characteristics, the pressure pulsation characteristics of impeller region and tip clearance region and the power loss distribution diagram are studied and analyzed. The results show that the maximum efficiency is 22.42% when the number of blades is 15, and 23.92% when the thickness is 10.5mm.

Vortex motion in vaneless space and runner passage of pump-turbine in S-shaped region

This study examines the S-characteristic, a key factor affecting the safe grid connection and operation of pumped-storage units, and its significant impact on the safety of pumped-storage power stations. We conducted numerical simulations and model experiments to investigate vortex motion characteristics in the vaneless space and runner passage of pump-turbines operating within the S-shaped region, along with an analysis of pressure pulsation characteristics. The accuracy of these simulations was validated through laser Doppler velocimetry experiments, and particle image velocimetry experiments were used to capture vortex motion in the vaneless space. We observed that vortices generated on the guide vane side follow the flow direction, blocking the guide vane passage, while those generated by runner blades move in the opposite direction. Employing an entropy production theory and the Liutex method, we investigated vortex distribution and hydraulic loss in the S-shaped region. The results show that reduced flow rates lead to significant vortices in the vaneless space and guide vane area, which become main contributors to energy loss in this region. These vortices, along with those in the runner passage, mainly arise from flow separation on blade and guide vane surfaces due to suboptimal inflow conditions. The study also identifies pressure fluctuations in the vaneless space, induced by a rotating stall, as the most significant pressure pulsation phenomenon, which significantly impacts the performance of the unit in both upstream and downstream directions.