Steady-state Flow Force Research Articles

Numerical Simulation of the Diffusion of Electroactive Molecule in Biosimilar Hydrogel Media

Based on experimental data of cyclic voltammetry, the values of the diffusion coefficients for toluidine blue in alginate hydrogel, gelatine hydrogel and alginate-gelatine hydrogels were obtained. Using the experimental values of the coefficients in a numerical model, the values of the recovery of flows have been calculated showing them consistent with what was the experimental. It is proposed to use the period in time during which the value of the flow force reaches the value of steady state flow force as an indicator of the diffusion properties of the hydrogel medium. The findings of this study can be used for the development of methods for the evaluation of the diffusion properties of hydrogel media: bioinks and tissue-engineered structures.

Simulation analysis and optimization of pilot type electro-hydraulic proportional directional valve based on multi field coupling

The pilot-operated electro-hydraulic proportional directional valve is widely used in complex and precision engineering fields. Its operational stability and reliability determine the overall performance of the hydraulic system. During the working process of the pilot-operated electro-hydraulic proportional directional valve, the spool is deformed due to the influence of pressure and temperature, resulting in problems such as clamping or stagnation. In order to solve this problem, this study uses the fluid-solid-thermal coupling simulation method to analyze the flow field characteristics and thermal deformation of the spool with different structural throttling grooves, and optimizes the U-shaped throttling groove structure. The results indicate that as the valve opening increases, the front section of the throttling groove becomes the primary region where the maximum radial deformation of the spool occurs. In this paper, the steady-state flow force of the valve core is taken as the measurement standard, the constraint range of the structural parameters is determined, and the radial thermal deformation is included in the optimization analysis of the structural size. It’s verified that the optimized flow characteristics are improved by about 32 % compared with that before optimization, and the maximum steady-state flow force after considering thermal deformation is reduced by about 4N compared with that before optimization. This provides an important design basis and reference for the structural design and optimization of the pilot electro-hydraulic proportional directional valve.

Design and optimization of hydraulic slide valve spool structure based on steady state flow force

This article studies the structure of hydraulic spool valve and the influence of different pressure differences on steady-state flow force. An improved scheme of designing a jet guide groove on the valve core is proposed to compensate for steady-state flow force. This article uses the CFD method to study the influence of spool valve structural parameters on steady-state flow force. The response surface method is used to establish the Polynomial regression model of the steady-state flow force, and the optimal structure size of the jet guide slot is obtained. The results indicate that the flow force increases with the increase of pressure difference. Moreover, under the same operating conditions, the absolute flow force of the spool valve with jet guide groove is smaller than that of the spool valve without jet guide groove. Therefore, the jet guide groove can effectively compensate for steady-state flow force, improve the control accuracy of the valve, and improve the stability of the spool valve.

Simulation and experimental research on steady flow force compensation for a servo proportional valve

In the development of high-performance directly driven proportional directional valves, reducing the flow force of the spool is a crucial aspect due to its significant influence on the dynamic characteristics and power consumption of these valves. This paper presents a study on the steady-state flow force of a servo-proportional valve spool by employing a combined approach of numerical simulations and experiments. Additionally, a method is proposed to compensate for the steady-state flow force by modifying the shoulder inclination of the spool. The results demonstrate that modifying the shoulder angle of the spool alters the emergence angle, leading to a substantial reduction in the steady-state flow force acting on the spool. Notably, the compensation method has negligible impact on the through-flow capability of the servo-proportional valve.

Review of the Research on and Optimization of the Flow Force of Hydraulic Spool Valves

As one of the important factors affecting the stability of slide valves, the analysis and research of flow force are of great significance. In recent years, more and more experts and scholars have conducted research in this field, attempting to find methods to reduce or utilize the flow force of hydraulic spool valves. Flow force includes steady-state flow force and transient flow force, with steady-state flow force having the most significant impact on spool valves. The influencing factors of flow force are complex and diverse, including the cavitation phenomenon, shape of the throttling groove, and jet angle. At present, the main ways to reduce flow force are to design the structure of the spool valve, the structure of the valve sleeve, and the flow channel of the valve body. This article mainly reviews the definition, calculation methods, influencing factors, and methods for reducing the flow force of slide valves. This provides a new approach to reducing the flow force in hydraulic spool valves.

Characteristics of Cavitation Flow for a Regulating Valve Based on Entropy Production Theory

A regulating valve is a key control element in the coal liquefaction industry, whose flow field distribution is related to the entropy production. In order to make a quantitative evaluation of the energy loss in the cavitation flow and calculate the magnitude and location of the hydraulic loss in the flow field more accurately, entropy production theory is employed to analyze the flow field in the regulating valve numerically. The entropy production under cavitation condition and its influence on steady-state flow force are also discussed. When the opening of the valve increases, the entropy production and energy loss change dramatically. The entropy production rate (EPR) is mainly distributed at the orifice and downstream of the regulating valve, the entropy production rate (EPR) reaches the maximum value at the orifice, and turbulent pulsation entropy production (TPEP) is the main part of the total entropy production for flow. When the valve’s opening increases from 40% to 70%, the total entropy production (TEP) increases from 467.14 W/K to 630.04 W/K. The entropy production by cavitation (EPC) increases firstly and then decreases. The smallest value of EPC is 0.103 W/K at the 40% opening, while the maximum value is 0.119 W/K at 60% opening. Furthermore, the relationship between total entropy production (TEP) and steady-state flow force can be approximated by an exponential distribution. When the steady-state flow force increases, the total entropy production for flow also increases. Cavitation effect on the steady-state flow force is strengthened firstly and then weakened with increasing the valve’s opening. Finally, a discriminant method based on the change of the steady-state flow force is proposed to detect whether cavitation occurs in the valve or not. The results in this paper could provided a directional and quantitative evaluation of energy loss in the regulating valve, which is help for the structural shape optimization and service life extension combining with external characteristics of the valve and internal flow field.

CFD analysis of flow field and hydrodynamic compensation of poppet valve

The steady-state hydrodynamic force of cartridge valve poppet valve core reduces the stability of cartridge valve. A circular arc structure is added to the main valve core of the poppet valve to compensate the steady-state flow force. Referring to the structure and parameters of the actual cartridge poppet valve, the three-dimensional geometric model of the flow channel in the valve is established with UG software. CFD method is used to calculate and analyze the flow state of fluid in the poppet valve under the working state of the valve core, and the influence of the arc size and position of the valve core on the steady-state hydrodynamic compensation of the main valve core is studied. The results show that the circular arc structure can realize the hydrodynamic compensation of the valve core and increase the stability of the valve core. When the opening amount is small, properly increasing the height h of the circular arc structure can increase the static hydrodynamic compensation of the valve core; Keep the circular arc structure size L less than 1mm, and the static hydrodynamic compensation effect of the valve core is better.

Study on flow force compensation characteristics and optimization design of jet guiding groove

A jet guiding groove is designed on the spool to compensate the steady-state flow force. The steady-state flow force model is analyzed and derived. The influence of structural parameters on steady-state flow force is studied by CFD simulation. The response surface method is used to construct the steady-state flow force polynomial regression model. The optimal structure size of the jet guiding groove is obtained. The steady-state flow force compensation coefficient is defined and calculated. Results show that the compensation effect decreases with the increase of pressure difference. However, at the same pressure difference, the absolute value of the compensation coefficient of the spool with jet guiding groove is less than that of the spool without jet guiding groove. The results show that the jet guiding groove can effectively compensate the steady-state flow force and improve the control accuracy of the valve.

A hybrid of surrogate model and MIGA method for optimization and compensation of steady-state flow force on water hydraulic HSV

In this research, a hybrid of surrogate model and Multi-island genetic algorithm (MIGA) is proposed for optimization and compensation of steady-state flow force on water hydraulic high-speed on-off valve (HSV) driven by voice coil motor. Firstly, a dynamic model on the spool of HSV is established, and the effects of spool displacement, spool half-cone angle, valve stem diameter and inlet pressure on the steady-state flow force of HSV are analyzed through the CFD simulation. Secondly, a quadratic response surface model is set up based on design of experiment (DOE) to analyze interactions of key parameters on steady-state flow force. MIGA is proposed to optimise the structural parameters of HSV, and the optimization results are analyzed and verified by CFD simulations. Simulation results demonstrate that the steady-state flow force is reduced significantly. Finally, the steady-state flow force in the optimized structure of HSV is also verified experimentally. The experiment results exhibit that the optimized spool can compensate about 71% for the steady-state flow force, then reduce about 15% the energy consumption of HSV. This research will provide the guide for the design and engineering application of HSV.

Characteristic of Steady-State Flow Force on the Cone Valve Based on Orthogonal Test Method

The steady-state flow force is the fundamental reason that affects the pressure stability, which will reduce the control performance of a hydraulic valve. A mathematical model of the axial steady-state flow force on the valve core is proposed to master the principle and characteristics of steady-state flow force. For understanding the dynamic changes of the steady-state flow force, a two-dimensional axisymmetric model is built to discuss the value of flow force. Different geometric parameters and operating conditions have different effects on the performance of the valve, and analyzing a variety of parameters is difficult because of the complexity of the test. Therefore, the geometric parameters and operating conditions in the steady-state flow force were optimized by the orthogonal test-optimization method. The main significant factors affecting the performance of steady-state flow force on the cone valve core are determined by extreme difference analysis, which are the opening and pressure differential, respectively. Furthermore, a test ring is built to measure the steady-state flow force. The results show that the greater the pressure differential is, the greater the steady-state flow force is. The steady-state flow force does not increase linearly, but increases first and then decreases with the increase of the opening. The study will lay the foundation to precise axial flow force prediction and reference for design optimization of the valve.

Fluid-dynamic analysis and multi-objective design optimization of piezoelectric servo valves

This paper proposes an effective methodology for the fluid-dynamic design optimization of the main spool of a piezoelectric servo valve. The aim is to improve global performances of the piezoelectric servo valve by reducing the flow force acting on the main spool and the mass of the main spool. The main disturbance forces acting the main spool were analyzed. The steady-state flow force acting on the main spool was derived and the relationship between the flow force and the design parameters of the main spool was established. The design problem of the main spool was formulated mathematically as a multi-objective optimization problem. The minimum steady-state flow force and the minimum mass of main spool were considered as optimization objectives. The elitist non-dominated sorting genetic algorithm (NSGA-II) was applied and a set of Pareto-optimal solutions was calculated. The optimized results were analyzed and the final design parameters of the main spool were selected for the simulation analysis and experimental research. The computational fluid dynamics (CFD) simulation was employed to calculate the forces acting on the main spool. Simulation results show the flow force acting on the optimized main spool is significantly reduced. The unoptimized and optimized main spools were machined and experimental study was performed. Results show that the piezoelectric servo valve equipped with the optimized main spool has better response performance and dynamic bandwidth. The dynamic bandwidth is measured to 172 Hz under the amplitude attenuation of −3 dB. Compared with the piezoelectric servo valve with unoptimized main spool, the dynamic bandwidth of the piezoelectric servo valve with optimized main spool is increased by 26%.

Study on the Influence of Triangular Groove Structure on Steady-State Flow Force Compensation Characteristics

In this study, a structurally improved spool was designed. The diameter of one side of the spool stem was reduced, making the spool stem into a rounded table shape. A triangular groove was circumscribed on the step and on the same side. After liquid flow was guided through the triangular groove, the flow direction changed. A flow component in the negative direction was generated, which reversely impacted the liquid flow in the positive direction. The liquid flow angle at the outlet increased; that is, jet angle increased and flow force decreased. The simulation results show that, increasing the depth, H, of the triangular groove has a positive effect on flow-force compensation and was conducive to the stability of the valve core. Properly increasing the groove’s bottom diameter, D1, of the triangular groove was conducive to the stability of the spool, but when D1 was too large, the flow force increased. The experimental results are consistent with the simulation results, which proves that the improved structure can effectively reduce the flow force of the spool.

Influence and Improvement of Hydraulic Power on Spool Valve Reversing

This paper analysed the effect of steady-state flow force and transient flow force to sliding direction valve, and two examples were given to illustrate adverse consequences caused by excessive fluid power, put forward the compensation measures. The effect of flow force should be considered when designing the hydraulic system in order to make the hydraulic system work more stable.

On the Steady-State Workpiece Flow Mechanism and Force Prediction Considering Piled-Up Effect and Dead Metal Zone Formation

Abstract The manufacturing of miniaturized components is indispensable in modern industries, where the uncut chip thickness (UCT) inevitably falls into a comparable magnitude with the tool edge radius. Under such circumstances, the ploughing phenomenon between workpiece and tool becomes predominant, followed by the notable formation of dead metal zone (DMZ) and piled-up chip. Although extensive models have been developed, the critical material flow status in such microscale is still confusing and controversial. In this study, a novel material separation model is proposed for the demonstration of workpiece flow mechanism around the tool edge radius. First, four critical positions of workpiece material separation are determined, including three points characterizing the DMZ pattern and one inside considered as stagnation point. The normal and shear stresses as well as friction factors along the entire contact region are clarified based on slip-line theory. It is found that the friction coefficient varies symmetrically about the stagnation point inside DMZ and remains constant for the rest. Then, an analytical force prediction model is developed with Johnson–Cook constitutive model, involving calibrated functions of chip-tool contact length and cutting temperature. The assumed tribology condition and morphologies of material separation including DMZ are clearly observed and verified through various finite element (FE) simulations. Finally, comparisons of cutting forces from cutting experiments and predicted results are adopted for the validation of the predictive model.

Numerical Simulation and Experimental Research on Flow Force and Pressure Stability in a Nozzle-Flapper Servo Valve

In the nozzle flapper servo valve, the transient flow force on the flapper is the fundamental reason that affects the pressure stability. The pressure pulsation in the pilot stage causes forced vibration of the flapper, and its deviation will directly influence the control pressure difference, which will make the pressure appear unstable. In order to grasp the principle and characteristics of transient flow force and its influence on pressure stability, a mathematical model of flapper displacement and control pressure is derived. For collecting the dynamic changes of the transient flow force and recording the motion behavior of the flapper, a three-dimensional model of the pilot-stage is established. Numerical simulations of turbulence phenomenon analysis are conducted with a variation of flapper displacement ranging from 5 μm to 20 μm. It can be concluded that the change trend of the flapper displacement is similar to the steady-state flow force and the transient flow force pulsation amplitude. Under the same structural parameters, the pulsating frequency of the flow force remains basically constant. The fluctuation of the flow force of the pilot stage will cause the pressure of the servo valve control cavity to vibrate to a certain extent, which is a factor that cannot be ignored that affects the output stability of the servo valve.

Computational Fluid Dynamics Analysis of the Flow Force Exerted on the Disk of a Direct-Operated Pressure Safety Valve in Energy System

Abstract The flow force acting on a valve disk plays an important role in the overall performance of pressure safety valves (PSVs). To quantify the disk force, computational fluid dynamics (CFD) methods have been widely implemented. In this paper, the capability of CFD models, and the identification of the most suitable turbulence models' geometry modeling and mesh requirements have been assessed to establish the accuracy of CFD models for disk force prediction. For validation purposes, a PSV disk force measuring rig was designed and constructed to obtain the steady-state flow forces exerted on the valve disk at different valve openings. The CFD model assessment is achieved by comparing the simulation results to experimental measurements; this is achieved in two stages. Stage 1 investigates the use of Reynolds averaged Navier–Stokes (RANS)-based turbulence models where two-dimensional (2D) simulations are performed with five turbulence models. The results indicate that a variety of force results are produced by different turbulence models, among which the shear stress transport (SST) k–ω was found to have the best performance. Stage 2 investigates meshing and the use of symmetry and geometry simplifications; 2D, 1/8 three-dimensional (3D) and 1/2 3D mesh models are examined. The results indicate that the 1/8 3D mesh model is the optimal choice, owing to its higher accuracy and reasonable grid scale. The studies performed in this paper extend the knowledge of compressible flow force prediction, and should facilitate the design or optimization of PSVs.

Research on Influence of Different types of Orifice on Axial Steady-state Flow Force in Cartridge Proportional Valve

This article mainly investigates how orifice structure influences the characteristics of steady-state flow force. The research model of this paper is originated from a cartridge proportional valve. Firstly, predicting characteristics of the flow force working on poppet in different types of orifice through CFD simulations; secondly, several parameters of poppet and seat, which may affect the characteristics of flow force, are defined, a series of CFD calculations were conducted to find a rule how each parameter influences flow force; thirdly, according to the analysis, optimization of orifice structure parameters has been successfully realized. Finally, a test bench was established to validate the simulation results. The results show that the orifice type has a significant influence on flow force, which indicates that choosing certain type of orifice can effectively decrease the influence of flow force, and the negative effect of flow force can be reduced within an acceptable extent. Besides, the influence of orifice on pressure difference has been also taken into account. The experimental results agree well with the simulative one.

Structure optimization of conical spool and flow force compensation in a diverged flow cartridge proportional valve

In this article, a method aims at reducing the steady-state axial flow force working on the main spool of a diverged flow cartridge proportional valve was proposed. The maximum flow force of original main spool can reach as high as 24% of the control force, which will definitely cause a huge disturbance to the proportional control of main spool, and consequently, the work condition of valve will be in an unstable status. The main contents of this paper are as follows: first, describing the damping flange and its parameters which may influence the effect of compensation; second, the rule that how these parameters influence the flow force was found by a series of computational fluid dynamics (CFD) simulations, and then, according to the analysis, the optimal structure can be gained, besides, the effect of damping flange on pressure difference is also taken into account; at last, a test-bed was built up to validate simulative results. The experiment results shows that the result of simulation is reliable and the proposed methods is feasible.

Study on hydrodynamic numerical simulation and radical offset characteristics of outflow cone valve

Aiming at the complicated internal flow state of hydraulic cone valve and the effect of fluid force on the performance, radial offset was seldom considered in the research of cone valve, so the inner flow field model of cone valve was established by UG software, and the mesh model was divided by ICEM CFD software. Then, the simulation calculation was carried out by FLUENT. The distribution of steady-state flow force, pressure field, and velocity field under the different opening of the cone valve was obtained. In order to verify the correctness of radial offset, the hydraulic simulation under the same working condition was carried out by AMESim software. Finally, the radial force on both sides of valve core was calculated on the basis of the pressure field on both sides of the valve core. The results show that the radial force difference on both sides of the spool is small when the valve port is small. With the increase of the valve port opening, the radial force difference between the two sides of the valve core changes larger, and finally fluctuating within a certain range. Then, the radial offset value can be calculated by the radial force formula. According to the obtained offset, the simulation and experimental study on the cavitation of the cone valve are carried out. The simulation results of radial offset are verified according to the distribution position of the cavitation, which lay the foundation for the design and performance research of the hydraulic poppet valve.

Theoretical analysis of steady state operating forces in control valves

The controlling components, such as valves are used to regulate controlled fluid power. It is not always possible to calculate valve forces accurately, and with some types of valves even the existence of certain types of forces cannot be predicted with certainty. In many cases, however, the analysis can be made fairly completely and accurately. The assumption of steady state conditions is valid for the valve alone, but transient effects in the rest of the system may be large. These effects are particularly important with regard to the instability of valves, where the system may react on the valve in such a way as to make it squeal or oscillate, sometimes with large amplitude. The origin of the steady state flow force understood from a brief qualitative explanation. The following paper will summarize much of what is known about valve forces in the spool type controlling element.