Steady 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.

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.

The Effect of Spool Displacement Control to the Flow Rate in the Piezoelectric Stack-Based Valve System Subjected to High Operating Temperature

This work investigates the effect of spool displacement control of the piezoelectric stack actuator (PSA) based valve system on the flow motion of the pressure drop and flow rate. As a first step, the governing equations of the structural parts of the displacement amplifier and spool are derived, followed by the governing equation of the fluid part considering control volume and steady flow force. Then, an appropriate size of the valve is designed and manufactured. An experimental apparatus to control the spool displacement is set up in the heat chamber and tracking control for the spool displacement is evaluated at 20 °C and 100 °C by implementing a proportional-integral-derivative (PID) feedback controller. The tracking controls of the spool displacement associated with the sinusoidal and triangular trajectories are realized at 20 °C and 100 °C. It is demonstrated that the tracking controls for the sinusoidal and triangular trajectories have been well carried out showing the tracking error less than 3 μm at both temperatures. In addition, the flow motions for the pressure drop and the flow rate of the proposed valve system are experimentally investigated. It is identified from this investigation that both pressure drop and flow rate evaluated 20 °C have been decreased up to 18% at 100 °C. This result directly indicates that the temperature effect to control performance of the structural part and fluid part in the proposed PSA based valve system is different and hence careful attention is required to achieve the successful development of advanced valve systems subjected to a wide range of the operating temperature.

Research on the dynamic characteristics of water hydraulic servo valves considering the influence of steady flow force

The International Thermonuclear Experimental Reactor remote-handling (ITER-RH) system powered by water hydraulics is a vision of the future. The 2D servo valve is a new type of servo valve, maybe suitable for the ITER-RH system. It has many advantages, including its fast response and strong anti-pollution ability. However, steady flow force is currently considered to be one factor that impacts the dynamic characteristics of servo valves. In this study, the influence of steady flow force on the dynamic characteristics was analyzed, and the structure was optimized accordingly. A mathematical model of the servo valve was built using theoretical analysis and numerical simulation. Results indicated that the amplitude bandwidth of the 2D water hydraulic servo valve was 169 Hz without considering the steady flow force, and it decreased to 162 Hz when the steady flow force was considered. Furthermore, a newly designed valve sleeve, to compensate for the axial steady flow force, was proposed by changing the angle of the inlet port designed in the valve sleeve to the spool axis. The maximum compensation capacity of the axial steady flow force was 35%, and the best angle of the inclined holes was approximately 120°. The optimized amplitude bandwidth of the 2D servo valve was 167 Hz. The results demonstrate that the optimized valve sleeve improved the dynamic response of the 2D servo valve.

Research on a high-accuracy and high-pressure pneumatic servo valve with aerostatic bearing for precision control systems

In this paper, a novel single-stage high-pressure electro-pneumatic servo valve (HESV) directly driven by a voice coil motor (VCM) is proposed for a precision control system. The HESV is a three-position three-way spool-type flow valve. As the friction force of the spool increases, the clearance between the spool and sleeve decreases. The aerostatic bearing is designed to reduce the friction wear and improve the motion sensitivity of the spool. A nonlinear mathematical model of the HESV is derived including the electromagnetic subsystem, dynamic force balance equation, and so on. Furthermore, considering the highly nonlinear steady gas flow force, a hybrid fuzzy logic PID controller with a disturbance observer (DOB) is adopted to improve the performance of the HESV. In this study, a numerical analysis and experiments are carried out, and their results indicate that the static friction force of the developed HESV decreases from 15 N to 4.4 N because of the aerostatic bearing. The developed HESV exhibits a strong anti-interference performance because of the hybrid controller with the DOB; the valve spool can be recovered to the original control position rapidly within 0.03 s. The position control accuracy of the novel HESV is greatly improved. Thus, the HESV can be applied to high-pressure pneumatic precision control systems.

Dynamic Characteristics and Stability Analysis of Conical Relief Valve

The overflow rate of poppet relief valve is established, the dynamics characteristics of poppet relief valve which contains transient flow force and steady flow force is established. Based on this point, the stability conditions of poppet relief valve system are derived using Routh-Hurmitz method. The effect of the design parameters of relief valve on the dynamic characteristics of poppet valve system is analyzed. Using sensitivity analysis, the effects of parameters of the most significant is obtained, that is diameter D of liquid flow cylinder fluid. The results showed that, the established model can largely capture the dynamic characteristics of the relief valve system, the established stability condition can be used as a favorable basis for the design of valve. DOI: http://dx.doi.org/10.5755/j01.mech.25.1.22881

Steady Flow Force Compensation and Test Research on Electrohydraulic Proportional Relief Valve

The pressure control accuracy of electrohydraulic proportional relief valve (EPRV) is affected by steady flow force. Thus, this paper investigates the method of designing a spool groove into the turbine bucket profile to compensate for the steady flow force maximally. The influence of steady flow force on the working pressure of the EPRV is analyzed. The calculation model of the steady flow force is deduced. Moreover, the computational fluid dynamics (CFD) model of the spool is established considering the fitting clearance between the spool and the valve body. The test bench is built to verify the CFD model. The turbine bucket profile is designed in the spool groove and optimized on the basis of the response surface method. Furthermore, the flow impact coefficient is defined and the compensation effect of the optimized spool to the steady flow force is tested. The results show that the absolute error value of the CFD simulation and test is smaller than 6.51%. When the working pressure is 0.5, 2, and 4 MPa, the flow impact coefficients of the optimized spool can be reduced by 100%, 59.15%, and 26.72%, respectively, compared with the original spool, indicating that the optimized spool can obviously compensate the steady flow force and improve the control accuracy of the EPRV.

Analysis on the Main Design Parameters Influencing the Impact Efficiency of Dual-Chamber-Controlled Hydraulic Drifter

Previous investigators demonstrate that the impact performance of the drifter is affected by the forces such as viscous friction resistance and axial thrust of liquid. In this research, some other forces including hydraulic sticking force, sealing resistance, steady flow force and transient flow force are also taken into the consideration to develop a non-linear mathematical model of the dualchamber-controlled hydraulic drifter. We take piston mass, supply flow rate, supply pressure and the front and back work areas of the piston as the main design parameters to predict the impact efficiency of the drifter using the controlling variable method. The result shows that the impact efficiency decrease as the increasing of the piston mass or supply flow rate. The impact efficiency reaches a peak value 0.48 when the supply pressure P ranges from 150 to 230 bars. The decrease of the front work area A1 of the piston, as well as the increase of the back work area A2, would improve the impact efficiency. With the combination of the design parameters P, A1 and A2, there is a high efficiency area 162.5 < P < 230 bars and 0.48 < A1/A2 < 0.86 with the impact efficiency value 0.46–0.495.

Numerical and experimental investigation on opening direction steady axial flow force compensation of converged flow cartridge proportional valve

This paper proposes a method to optimize a structure that can compensate the steady axial flow force acting on the spool in a converged flow cartridge proportional valve. The negative flow force working on the origin conical poppet, which can be as large as 13% of the control force, acts as a big disturbance to the conical spool position adjustment, resulting in poor lowering speed control performance of the proportional valve or even instability of the conical spool. Firstly, by introducing a damping tail structure to the conical poppet, the direction and the value of the flow forces can be regulated, and through changing parameters of damping tail, the optimal structure can be obtained. Computational fluid dynamics (CFD) calculations were conducted to analyze how the damping tail parameters affect the flow forces and obtain the best parameter combinations. A test rig was set up to verify the effect of above methods. Good agreement of the CFD calculations and experiment results indicates that the proposed methods can provide guidance for the flow force regulation of other valve poppets.

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.

A study of steady water flow forces acting on a bridge girder

A study of steady water flow forces acting on a bridge girder

Effects of groove shape of notch on the flow characteristics of spool valve

The grooves of notches of hydraulic spool valves are usually designed into various shapes for their desired flow characteristics. The aim of this paper is to clarify the effects of the groove shape on the flow characteristics through computational fluid dynamics (CFD) and experimental investigations. The RNG k–ε turbulence model is used to simulate the pressure distributions of the flow fields inside three notches with their corresponding typical structural grooves in order to analyze the changes of restricted locations along with the openings and, furthermore, to calculate the flow areas of the notches. The accuracy of the employed model is demonstrated by comparing the computational results with the experimental data. Additionally, the flow rate vs. pressure drop data obtained from the experiment is fitted by least square method. On this basis, the discharge coefficient as a function of groove geometry, flow condition, fitting coefficients and its stable value is deduced, proving to be quite consistent with the experimental result. Thanks to the jet flow angles estimated by CFD simulation, the steady flow forces are calculated, which show good agreement with the experimental results except for some small differences. Finally, the throttling stiffness of the three notches is investigated, with that of divergent U-shape groove falls between spheroid-shape groove and triangle-shape groove. Similar results are found for steady flow force. The results indicate that the groove shape has significant effects on the flow characteristics (flow area, discharge characteristic, jet flow angle, steady flow force and throttling stiffness) of spool valve.

Flow field simulation and establishment for mathematical models of flow area of spool valve with sloping U-shape notch machined by different methods

Precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke was derived. The computational fluid dynamics was used to analyze the flow features of the sloping U-shape notch on the spool, such as mass flow rates, flow coefficients, efflux angles and steady state flow forces under different operating conditions. At last, the reliability of the mathematical model of the flow area for the sloping U-shape notch orifice on the spool was demonstrated by the comparison between the orifice area curve derived and the corresponding experimental data provided by the test. It is presented that the bottom arc of sloping U-shape notch (ABU) should not be omitted when it is required to accurately calculate the orifice area of ABU. Although the theoretical flow area of plain bottom sloping U-shape notch (PBU) is larger than that of ABU at the same opening, the simulated mass flow and experimental flow area of ABU are both larger than these of PBU at the same opening, while the simulated flow force of PBU is larger than that of ABU at the same opening. Therefore, it should be prior to adapt the ABU when designing the spool with proportional character.

Study on Flow Rate and Steady Flow Force of Hydraulic Combination Valve Based on CFD

Hydraulic spool valve is the key components in fluid transmission and control technology. This paper analyzes flow field of the combination valve based on the CFD software. It gains the characteristic of flow rate and steady flow force, and it offers reference for design of the hydraulic combination valve.

Study on the Effect of Cone Diameter on the Cone Resistance and Steady Flow Force of Hydraulic Poppet Valve

The 3-D model is established and is meshed. Then the inner flow field of the poppet valve is simulated at different cone diameter E, different opening positions. Analyzing the result of simulation, the variation curves of cone resistance and steady flow force in different opening of different structure parameters can be obtained. This study for the valve offers the significant reference for designing the valve and optimizing its performance.

Study on the influence of flow force on a large flowrate directional control valve

This paper focuses on analyzing the characteristic of the flow forces acting on a large flowrate directional valve (1200L/min). The flow area of the notches on the spool is calculated and the mathematic model of the spool is presented. The change rule of the total steady flow force is obtained through numerical simulation. The nonlinear response of the spool valve is explained reasonably and the input forces needed to make this valve closing reliability are given out respectively. The results show that the total flow force promotes the spool movement at the beginning but suppresses it after the spool displacement reaches a certain value. Furthermore, the vibration is caused by the dynamic force balance acting on the spool, leading to the large input force to make sure the relative ports closed. It is proposed that each pair of ports of the large flowrate directional control valve should be designed to the same structure to weaken these problems.

Evaluation and compensation of steady gas flow force on the high-pressure electro-pneumatic servo valve direct-driven by voice coil motor

A novel voice coil motor (VCM) direct drive single stage high-pressure pneumatic servo valve is designed, and then the steady gas flow force acting on the spool of the servo valve is investigated by numerical simulation and experimental methods in this paper. At present, many studies about flow force are concentrated mainly on hydraulic valves, but rarely on pneumatic valves. However, the velocity of gas is up to sonic when high-pressure gas flows through the servo valve orifice. And therefore, the steady gas flow force, generated by high pressure and high speed gas flow, cannot be neglected and is an important disturbance for the VCM direct-drive single stage high-pressure pneumatic servo valve. Consequently, the numerical simulation with computational fluid dynamics (CFD) is adopted to analyze the flow filed, jet angles, and steady gas flow forces for the servo valve with different valve openings and inlet pressures. The experimental study is performed to evaluate and confirm the numerical analysis. Then the compensated approach is proposed to reduce the steady gas flow force for the servo valve, changing the angle of non-metering port designed in the valve sleeve to the spool axis. The results demonstrate that the presented numerical analysis method is validated, the gas jet angle for the servo valve orifice is more than 69° and varies with different spool openings, and the steady gas flow force is nonlinear with valve opening and linear with inlet pressure when the outlet boundary is atmospheric pressure. Moreover, the steady gas flow force can be decreased by using the compensated method, which indicates that the single stage servo valve tends to require less power and energy to actuate for the VCM.

Pressure Transient Flow Forces for Hydraulic Spool Valves

The objective of this paper is to experimentally investigate the significance of the pressure transient flow force acting on hydraulic spool valves. In the past, this flow force effect has been routinely neglected due to its assumed small size. Through analytical and experimental methods, this research shows that flow forces due to pressure transient effects can be comparable in magnitude to the steady flow forces acting on the valve and that the past tradition of neglecting this effect may not always be justified. The paper also shows that the traditional steady flow force model does a fairly good job predicting the steady flow forces on the valve, but more research must be done to develop a good model for pressure transient flow forces.

Numerical Simulation and Visualization of Flow Field in a Special Piloted Directional Valve for Marine Steering Gear

In order to understand the working performance of the special pilot operated directional valve, flow field simulation based on CFD and dynamic response simulation in MatLAB Simulink are adopted in the study of this paper. 3D flow field model of the valve with three kinds of the notch separately is build up using Pro/E, Gambit is used to generate quality computational grid, and the numerical simulation is performed by using the commercial code ‘Fluent’. The mathematic model based on physical equations for the valve is also established in Matlab Simulink, the dynamic responses are analyzed for the valve with three different notch types separately. The results show that the minimum pressure positions in flow fields are on the valve body near the notches. The value of the minimum pressure with K notches is the highest among three kind notch types. The minimum pressures will decrease greatly along with the flow rate increased. The efflux angles for the valve with three kind notch types separately are different, so are the steady flow forces. The valve with V notches responses quickest, but the ram moves quickest with U notch valve. The research in the paper contributes to a deeper understanding of the flow and dynamic response characteristics. The research method combining CFD simulation and MatLAB Simulink is available and will derive more precise results.