Pressure-flow Characteristics Research Articles

Research on Multi-Objective Optimization of Low Pulsation Unloading Damping Groove of Axial Piston Pump

The high- and low-pressure switching of the axial piston pump is realized by the structure of the valve plate, and the buffer-groove structure on the valve plate is very important to reduce the pressure shock and flow fluctuation. In order to optimize the structural parameters of the buffer tank of the piston pump, the influence of the triangular-groove structure on the outlet pressure–flow characteristics was analyzed, and the low-pulsation buffer-groove structure was designed. First, the relationship between the structure of the triangular buffer tank and the output pressure and flow characteristics of the pump was analyzed theoretically. The Computational Fluid Dynamics (CFD) method was used to calculate the pressure and flow characteristics of the whole pump flow field of the triangular-groove structure, and the influence of the buffer-groove structure parameters on the outlet flow pulsation characteristics was studied. The multi-objective optimization algorithm was used to optimize the structure parameters of the buffer tank, and the optimized structure significantly reduced the outlet pressure–flow pulsation of the piston pump. The results show that, after optimization, the width angle of the front and rear triangular groove is 82.3°, the depth angle is 12.7°, the optimized pressure pulsation rate is 0.3%, and the optimized flow pulsation rate is 13.7%.

МОДЕЛЮВАННЯ РОБОЧОГО ПРОЦЕСУ СТРУМИННОГО НАСОСА ПРИ ЙОГО АСИМЕТРИЧНОМУ ОБЕРТАННІ В СВЕРДЛОВИНІ

The structure of the equations of the pressure-flow characteristics of the high-pressure jet pump is supplemented with a component that determines the additional pressure caused by the influence of eddy currents during the asymmetric rotation of the ejection system around the axis of the well. On the basis of the joint solution of the Bernoulli equations, the preservation of the integrity of the moving medium, the momentum and moment of movement of the mixed flows, a relationship was obtained for the analytical determination of the additional dynamic pressure created by the rotation of an eccentrically placed jet pump in the well. In the process of researching the resulting equation, the extreme nature of the growth of the pressure-flow and energy characteristics of the overbite ejection system was established. The increase in pressure and efficiency caused by the asymmetric rotation of the over-chisel ejection system is inversely proportional to the value of the main geometric parameter of the jet pump.

Correlation Analysis Between Echinocytosis Stages and Blood Viscosity During Oxygenator Perfusion: An In Vitro Study.

The study aimed to investigate the effect of red blood cell (RBC) morphology on oxygenator perfusion, focusing on stages of echinocytosis and their correlation with blood viscosity. A test circuit with an oxygenator and human RBC mixtures was used to induce changes in RBC shape by increasing sodium salicylate concentrations (0, 10, 20, 30, 60, and 120 mmol/L), while hematocrit, blood temperature, and anticoagulation were maintained. Blood viscosity was measured using a continuous blood viscosity monitoring system based on pressure-flow characteristics. Under a scanning electron microscope, the percentages of discocytes, echinocytes I-III, spheroechinocytes, and spherocytes were determined from approximately 400 cells per RBC sample. Early echinocytes, mainly discocytes and echinocytes I and II in the range of 0-30 mmol/L were predominant, resulting in a gradual increase in blood viscosity from 1.78 ± 0.12 to 1.94 ± 0.12 mPa s. At 60 mmol/L spherocytes emerged, and at 120 mmol/L, spheroidal RBCs constituted 50% of the population, and blood viscosity sharply rose to 2.50 ± 0.15 mPa s, indicating a 40% overall increase. In conclusion, the presence of spherocytes significantly increases blood viscosity, which may affect oxygenator perfusion.

Design and Characteristic Research on Variable Displacement Mechanism of Two-Dimensional (2D) Bivariable Pump

In a hydraulic system, a micro variable pump is required to be high pressure and high speed, and this work presents a new type of 2D bivariable pump structure in which the worm gear and worm mechanism are used to rotate the cylinder block to change the flow distribution state of the cylinder window and the piston groove to change the displacement of the 2D pump. The flow–pressure mathematical model of the 2D variable pump is established to analyze the relationship between pump displacement and the pump cylinder rotation angle and the effects of variable displacement on pump pressure characteristics, flow characteristics, and volume efficiency in Matlab. During the experiment, we tested the change in the corresponding pump output flow when the cylinder rotation angle is 0~12°, which verifies the correctness of the variable calculation model. The experimental results indicate that the volume efficiency and mechanical efficiency of the single-piston 2D pump are reduced to different degrees after variable displacement, the volume efficiency is reduced by approximately 3% at most, and the mechanical efficiency is reduced by approximately 5% at most.

Multi-Physical Field Simulation of Magnetorheological Fluid Flow State in Valve Magnetorheological Damper

Magnetorheological fluid (MRF) is a kind of magnetic field responsive intelligent fluid, which is widely concerned in the field of damping and vibration reduction. The flow state of MRF plays a key role in vibration control in dampers. In this work, the flow behavior. of magnetorheological fluid (MRF) in a valve damper is studied through multi-physical field simulations. The objective is to comprehensively comprehend the influence of the magnetic field on the velocity distribution and pressure drop of the MRF within the damper channel. The magnetic field is generated by creating an electrified coil, and the magnetic flux density is subsequently changed by adjusting the current. The magnetic field calculation shows that the magnetic field is almost perpendicular to the MRF flow direction at the narrowest part of the damper channel. Next, based on the coupling calculation of multiple physical fields between fluid flow, electric field, and magnetic field, the flow velocity and pressure characteristics of MRF in the flow channel were calculated and analyzed. The results indicate that at the slit where the MRF flow direction is perpendicular to the magnetic field direction, the volume force acting on the MRF reduces its flow velocity, resulting in a significant pressure difference between the left and right sides of the flow channel. Additionally, the flow rate of MRF exhibits a decrease as the magnetic field strength increases. When the magnetic field strength increases from 0. 5T to 1. 5T, the flow rate of MRF fluid at the narrowest part of the flow channel decreases by about 0. 18m/s.

Investigation of Wall Effect on Packing Structures and Purge Gas Flow Characteristics in Pebble Beds for Fusion Blanket by Combining Discrete Element Method and Computational Fluid Dynamics Simulation

In a tritium-breeding blanket of a fusion reaction, helium, used as a tritium-purging gas, will purge the tritium breeder pebble beds to extract the tritium in blanket. The purge gas flow characteristics will affect the tritium extraction efficiency. The effect of the fixed wall on the pebble packing structures and purge gas flow characteristics was investigated by combining the discrete element method (DEM) and computational fluid dynamics (CFD) method. The results indicate that the fixed wall leads to a regular packing of the pebbles adjacent to the fixed wall in association with drastic fluctuations in the porosity of the pebble bed, which can affect the purge gas flow behaviors. Further analyses of helium flow behaviors show that the helium pressure in the pebble bed decreases in a linear manner along the flow direction, whereas the pressure drop gradient of helium increases gradually with an increase in the packing factor. The reduction in porosity in the pebble bed leads to a notable escalation in helium flow velocity. Concerning the direction perpendicular to the helium gas flow, the evolution of the cut-plane averaged velocity of helium is similar to that of the porosity, except in the region immediately adjacent to the wall. The pressure drop and flow characteristics obtained in this study can serve as input for the thermohydraulic analysis of the tritium blowing systems in the tritium-breeding blanket of a fusion reactor.

Experimental investigation of flow patterns and rheological characteristics of compressed air foam in horizontal tube

The use of compressed air foam (CAF) for fire suppression has undergone rapid development in recent years. It has been successfully applied in fire incidents in the petroleum and chemical industries. The increasing need to fighting fires at high elevations necessitates an understanding of the rheological characteristics, pressure gradient changes, flow characteristics, and regularities of CAF within long firehoses. Therefore, this paper focuses on an investigation of the flow characteristics of CAF at foaming agent concentrations ranging from 0.1% to 1.2% and gas–liquid ratios ranging from 5 to 25. Specifically, it explores foam characteristics, pressure loss, and the relationship between flow rate and foaming agent concentration. The findings reveal that CAF exhibits four flow patterns: wave flow, elastic flow, ring flow, and dispersion flow. For most CAF firefighting applications, a foaming agent concentration of 0.3%–0.5% and a gas–liquid ratio of approximately 10 are suitable. However, for fire isolation purposes, a foaming agent concentration of 0.7%–1.0% and a gas–liquid ratio of over 15 should be employed. By utilizing a power-law rheological model and an experimental regression method, a prediction model is obtained for the flow characteristics and pressure loss of CAF in pipelines. The predictions of the model exhibit an error of less than 10% when compared with experimental results, validating the model. The results of this study provide a theoretical basis and technical support for understanding liquid supply resistance loss, which is crucial for maximizing firefighting effectiveness.

Measuring the pressure-flow characteristics of a proportional pilot operated pressure relief valve

The investigation of a pilot operated proportional pressure relief valve is described in this article. Different measurements are performed with a hydraulic test bench under laboratory conditions. A VT-VSPA1-1 amplifier module is used to control the current of the valve’s solenoid. The characteristics of the valve are determined as a function of the pressure – command value of the amplifier – volume flow rate. The results of the measurements can provide input data for the refinement of the mathematical model of the unit, which will be set up in the future.

Noise and Jet Momentum of Synthetic Jet Actuators with Different Orifice Configurations

Sound pressure levels and flow characteristics of a synthetic jet actuator (SJA) are investigated experimentally using the following orifice configurations: a) a slender rectangular slot orifice and b) an array of circular orifices with two different orifice diameters. All configurations have similar total orifice neck area, orifice height, and cavity volume, resulting in a similar Helmholtz frequency. Experiments are conducted for orifices mounted on a flat plate under a quiescent condition. The mean jet velocity exhibits resonant peaks at several excitation frequencies, which also gave rise to the sound pressure levels. The resonant frequencies and peak jet velocities were found to depend on the excitation amplitude and orifice configuration. Investigation of the jet momentum penetration into the quiescent air above the different orifice configurations shows that the momentum issuing from the rectangular slot decays much quicker than that of the circular orifices, irrespective of whether the SJA is excited at resonance or not. The most favorable performance (i.e., the highest momentum in the jet core) was obtained with the array of circular orifices having a smaller orifice diameter, even at off-resonance excitations. The work herein shows the possibility of reducing the SJA noise by 8–10 dB by operating the SJA at a frequency away from the Helmholtz frequency while still achieving comparable levels of jet momentum penetration into the crossflow.

Modelling and performance improvement of an annular grooved thrust air bearing

PurposeThis paper aims to combine the grooves with an annular air thrust bearing with multi-hole restrictors and discusses the influence of the groove parameters on the bearing performance.Design/methodology/approachFour models of aerostatic bearings with grooves of different geometries are established. The pressure distribution, load-carrying capacity (LCC), stiffness and flow characteristics of the flow field in the bearing clearances are obtained by computational fluid dynamics simulation.FindingsThe numerical and simulation results show that air bearing with grooved restrictors can slow down the pressure drop at the air inlet and increase the LCC and stiffness of the bearing. The gas flow in the aerostatic bearing is also studied, and the air vortex in the recess is analyzed.Originality/valueThis research optimizes the structure of the annular air thrust bearing, analyzes the gas vortex in the recess, improves the LCC and stiffness of the bearing and provides a reference for the bearing in the selection of groove parameters.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2023-0006/

A microfluidic transistor for automatic control of liquids

Microfluidics have enabled notable advances in molecular biology1,2, synthetic chemistry3,4, diagnostics5,6 and tissue engineering7. However, there has long been a critical need in the field to manipulate fluids and suspended matter with the precision, modularity and scalability of electronic circuits8–10. Just as the electronic transistor enabled unprecedented advances in the automatic control of electricity on an electronic chip, a microfluidic analogue to the transistor could enable improvements in the automatic control of reagents, droplets and single cells on a microfluidic chip. Previous works on creating a microfluidic analogue to the electronic transistor11–13 did not replicate the transistor’s saturation behaviour, and could not achieve proportional amplification14, which is fundamental to modern circuit design15. Here we exploit the fluidic phenomenon of flow limitation16 to develop a microfluidic element capable of proportional amplification with flow–pressure characteristics completely analogous to the current–voltage characteristics of the electronic transistor. We then use this microfluidic transistor to directly translate fundamental electronic circuits into the fluidic domain, including the amplifier, regulator, level shifter, logic gate and latch. We also combine these building blocks to create more complex fluidic controllers, such as timers and clocks. Finally, we demonstrate a particle dispenser circuit that senses single suspended particles, performs signal processing and accordingly controls the movement of each particle in a deterministic fashion without electronics. By leveraging the vast repertoire of electronic circuit design, microfluidic-transistor-based circuits enable fluidic automatic controllers to manipulate liquids and single suspended particles for lab-on-a-chip platforms.

Flow Turbulence and Pressure Fluctuations in a Hydraulic Jump

Turbulence and pressure fluctuations are key elements in the bed protection design of hydraulic structures. However, their roles in a hydraulic jump are not yet fully understood, and the nature of their relationships are not conclusive. In order to better understand the relationships between pressure fluctuations and flow characteristics of a hydraulic jump downstream of a weir, detailed measurements of flow kinematics using the nonintrusive techniques of particle image velocimetry and bubble image velocimetry and pressure using voltage-type pressure gauges were carried out in this study. The physical modeling of the hydraulic jump was carried out using the simultaneous measurements of pressure and turbulent flow properties. The distributions of flow properties, such as water level and velocity, were assessed in each case. Based on the measurements, the correlations between the pressure fluctuations and the variables were investigated by coupling the statistical values of the variables at the same points. The analysis results show that the water level and turbulence intensity are the main factors influencing the pressure fluctuations in the hydraulic jump. Using these factors, an empirical formula and dimensionless numbers are proposed to show that the pressure fluctuations depend on the bubble flow behavior.

Investigation on the pressure and flow characteristics for a high-speed bullet in high-altitude flight

The pressure analysis and flow characteristics during the flight of a high-speed bullet are significant for aerodynamic performance, flight trajectory control, safety and reliability, performance optimization, guidance and navigation. To accurately monitor the pressure variation for a high-speed bullet in the high-altitude flight, a novel local fluid domain method is introduced in current study. This method overcomes the limitations of conventional global fluid domain simulation methods, which often suffer from poor convergence and stability issues. On the basis, the force analysis is conducted and the mathematical model for the theoretical trajectory is established, which is applied to simulate the flight trajectory and construct fluid domain for the high-speed bullet. The findings reveal that monitoring points within the bullet hole are influenced by both cavity flow and the collision of forward airflows during the high-altitude flight. Furthermore, it is observed that the absolute total pressure and reference pressure at these monitoring points within the bullet hole are influenced by altitude variations. Subsequently, the factors affecting the absolute total pressure within the hole are explored, including the hole depth, the hole diameter, the hole position, and the bullet orientation. The results indicate that modifying the bullet structure to incorporate 45° angled hole, as opposed to standard holes, can lead to a 13.6% reduction in absolute total pressure variation. Additionally, mitigating the interaction between the external and internal fluids emerges as a critical factor in reducing absolute total pressure within the hole. This research not only presents a fresh perspective for pressure monitoring within the bullet hole, but also establishes a theoretical foundation for the precise guidance of high-altitude bullets.

Pressure-flow characteristics of a microchannel combining super-hydrophobicity and wall compliance

Pressure-flow characteristics of a microchannel combining super-hydrophobicity and wall compliance

Multi-objective optimisation of K-shape notch multi-way spool valve using CFD analysis, discharge area parameter model, and NSGA-II algorithm

Multi-way spool valves (MWSVs) with K-shape notches (KSNs) provide advantages such as improvement of the actuator speed control, micro-action, and response performance. However, the pressure drop (PD) associated with the energy consumption is larger of MWSVs under the high-pressure and large-flow condition. Meanwhile, extremely complex flow coefficient and multi-parameter, highly coupled KSNs are the chief factors restricting the flow-pressure characteristics exploration and optimisation design of MWSVs. To address these problems, complete numerical research and experiment are performed in this study, especially concerning the method of MWSV flow-pressure characteristics modelling, and surrogated model-based optimal design of KSN structures. First, the relationships between KSN structure parameters and flow-pressure properties of MWSV are modelled on the innovative discharge area parameter model (DAPM) and response surface methodology (RSM) (RSM-DPAM) using the CFD dataset. Second, to reduce the PD combining the flow control performance, surrogate model-based optimisation design is addressed. During optimisation, six KSN structure parameters are chosen as design variables, PD and flow area relative deviation (FARD) are selected as objective functions, and the RSM is employed as the projected model. Depended on the created surrogate model, the non-dominated sorting genetic algorithm (NSGA-II) is established to search for the optimal KSN structure. To certify the performance of the optimisation, flow field characteristics are analysed. The results demonstrate that the proposed RSM-DAPM-RSM model achieves reliable prediction for PD and FARD with a great correlation coefficient (0.9757 and 0.9946). The average PD reduces as much as 7.23% while the FARD is only 1.28%. Moreover, the region of low-pressure, high-velocity, and high-turbulent kinetic energy in the flow field are reduced. The proposed framework enhances the performance in KSN spool optimisation and could be applied to other kinds of notches.Abbreviations: BOI: Body of influence; BSV: Bucket spool valve; CFD: Computational fluid dynamics; CM: Construction machinery; DAPM: Discharge area parameter model; FARD: Flow area relative deviation; FCC: Flow control characteristic; GSA: Global sensitivity analysis; KSN: K-shape notch; MHAs: Meta-heuristic algorithms; MODE: Multi-objective differential evolution; MOGA: Multi-objective genetic algorithm; MOO: Multi-objective optimisation; MOPSO: Multi-objective particle swarm optimisation; MWSV: Multi-way spool valve; NRMS: Non-road mobile source; NSGA-II: Non-dominated sorting genetic algorithm; OLHD: Optimal Latin hypercube design; PD: Pressure drop; PDCs: Pressure drop characteristics; RSM: Response surface methodology; SA: Sensitivity analysis; TKE: Turbulent kinetic energy; TOPSIS: Technique for order preference by similarity to ideal solution; VFR: Volume flow rate

Experimental and numerical investigation on the wake flow and vortex shedding of a rotating circular cylinder

When fluid passes through a still cylinder, alternate shedding vortices are formed on the two sides of the cylinder in the wake. Regarding a rotating circular cylinder, the rotation can affect the wake flow and vortex shedding pattern. To investigate the wake flow and surface pressure characteristics of a rotating cylinder at different rotational speeds, wind tunnel tests and numerical simulation methods through Fluent were used. The dimensionless rotational speed was discussed for its impact on the vortex shedding intensity and pattern. Additionally, the correlation between the cylinder surface wind pressure and the vortex shedding pattern was analyzed. The results of this study provide useful insights into the mechanisms underlying the vortex shedding phenomenon and the effects of rotational speed on the wake flow and surface pressure of a rotating cylinder. The results show that an increase in the dimensionless rotational speed will change the characteristics of the wind pressure distribution, leading to the variation in aerodynamic coefficients. On the other hand, the vortex shedding characteristics of the wake flow will also be affected, with changes in the vortex shedding pattern and direction, thereby changing the characteristics of the wake deviation angle and correlation. Based on the analysis of wake flow speed power spectrum characteristics and the Reynolds number effect, the mechanism of the vortex shedding change caused by flow transitions is speculated and verified by numerical simulation of the vorticity field.

Performance of a new family of modular, bed-supported, chromatography devices.

Prepacked chromatography columns and cassette filtration units offer many advantages in bioprocessing. These include reduced labor costs and processing times, ease of storage, and enhanced process flexibility. Rectangular formats are particularly attractive as they can be easily stacked and multiplexed together for continuous processing. Cylindrical chromatography beds have dominated bioprocessing even though their bed support and pressure-flow performance vary with bed dimensions. This work presents the performance of novel, rhombohedral chromatography devices with internally supported beds. They are compatible with existing chromatography workstations and can be packed with any standard commercial resin. The devices offer pressure-flow characteristics independent of container-volume, simple multiplexing, and separation performance comparable to cylindrical columns. Their bi-planar, internal bed support allows mechanically less-rigid resins to be used at up to four times higher maximal linear velocities, and productivities approaching 200 g/L/h for affinity resins, compared to the 20 g/L/h typical of many column-based devices. Three 5 L devices should allow processing of up to 3 kg of monoclonal antibody per hour.

Analysis of Flow Characteristics of a Debris Filter in a Condenser Tube Cleaning System

In a power plant that uses seawater as a coolant, a debris filter (DF) is required to remove foreign substances from the seawater, and differential pressure leads to a decrease in the coolant flow rate, leading to a decrease in the power generation efficiency. In this study, an analysis was performed for the cases wherein the initial flow velocity conditions of the DF used in the condenser tube cleaning system (CTCS) were 1.5 m/s, 2.0 m/s, and 2.5 m/s using Ansys Fluent 2021, and the flow characteristics were identified. The flow and differential pressure characteristics of a CTCS with an installed DF were considered in a comparative analysis of the velocity, pressure, and turbulence kinetic energy (TKE) distributions. The results confirmed that a vortex was generated in the pipe with the DF, apparently due to the collision of the flow with the bracket of the DF. As the flow rate increased, the range of the vortex increased, causing a loss in flow.

Simulation study on the flow-induced vibration and noise in marine centrifugal pumps

Due to the three-dimensional non-axisymmetric shape of the volute, its interaction with the impeller increases the internal flow field complexity and instability of the marine centrifugal pump, representing the main reason for pump body vibration and hydraulic noise. First, the basic principle of fluid machinery noise calculation was explained based on the Lighthill acoustic analogy method and Curle’s theory. Then, the fluid pressure pulsation and flow characteristics of centrifugal pumps were analyzed using the Fluent software, after which the Actran software was used to examine the flow-induced vibration noise properties. The results showed that the clearance size significantly impacted the pump head, while the peak value of the flow-induced vibration response was mainly twice the blade frequency. Although a larger ring clearance increased the structural vibration, it had little impact on the sound pressure level changes in the external sound field. The results provided a new method for the structural optimization and low-noise design of marine centrifugal pumps.

Flow Pressure Characteristics of the Ahmed Glaucoma Valve and Possible Effect of Entrapped Air in the Tube.

The purpose of this study was to assess the pressure characteristics of the Ahmed Glaucoma Valve (AGV) and possible effects of air trapped in the tube. Physiologic saline was pumped through 17 AGVs using a syringe infusion pump, and the flow pressure was measured by a set of pressure transducers. During the infusion at a rate of 2µL/minute, the pressure measurement was repeated twice in each AGV to determine the repriming pressures with/without air (1µL) in the tube. After a pressure surge occurred during the initial priming, the pressure decreased suddenly and then became constant. The repriming pressure, determined as the peak pressure before valve opening, was significantly (P < 0.0001, paired t-test) higher with air (26.5 ± 6.8 mm Hg) than without air (12.1 ± 3.8 mm Hg), whereas the constant pressures after repriming was equivalent between with (10.6 ± 3.7 mm Hg) and without (10.4 ± 2.9 mm Hg) air conditions (P = 0.68). Air in the AGV tube causes increased repriming pressure of about two-fold compared to repriming without air. This pressure increment caused by air in the capillary-sized tube might occur because of the effects of viscosity pressure and capillary pressure. To ensure stable surgical results, surgeons are advised to not allow air to remain in the tube. Pars plana tube insertion of the AGV combined with gas tamponade surgery may result in higher-than-expected intraocular pressure. Conversely, injection of air/gas can avoid postoperative hypotony when the AGV is implanted in eyes with a high risk of hypotony.