Valve Dynamic Characteristics Research Articles

An Adaptive Control Method for the Distribution Valve of a Digital Pump

Perfect flow distribution is extremely important and essential for digital pumps. However, the fluctuation of motor speed and the change of valve dynamic characteristics cause the flow distribution flaw, which generates the backflow of the oil in the piston chamber and the decrease in pump volumetric efficiency. Based on the three-dimensional and mathematical modeling of the digital pump, the perfect distribution state of the digital pump is analyzed. Then, the adverse effects of the variations in motor speed and valve dynamic characteristics on the flow distribution of the digital pump were simulated and investigated by the software AMESim. To overcome the aforementioned problems, we proposed an adaptive control method for the flow distribution valve of a digital pump, which was realized by adopting the axis rotation angle and the pressure difference between the inlet and outlet of the flow distribution valve. The results show that the control signal of the flow distribution valve can be regulated automatically along with the motor speed and the valve dynamic characteristics, achieving the ideal flow distribution of the digital pump designed in this paper. The study can be used as a reference for the optimal design and prototype manufacturing of the digital pump.

An experimental study on the needle valve motion characteristics of high pressure natural gas and diesel co-direct injector

To reveal the gas needle valve dynamic characteristics of the high pressure natural gas and diesel co-direct injector, an innovative non-intrusive needle valve motion characteristics measurement method is proposed. The influence of needle valve movement on injection rate is investigated, and the effect of diesel pressure fluctuation on needle lift process is revealed. The results indicated that the lifting speed of the needle increases with the increase of gas injection pressure. Under the same injection pressure, the displacement curve of the needle valve changes from triangle to trapezoid with the increase in energizing time. Due to the change of the gas flow throttle position, the injection rate does not correspond linearly with the needle displacement curve. In the process of needle upstroke, there are two different velocities in the rising process of the injection rate. Furthermore, in the diesel system, the compression wave reflected from the common rail has a significant influence on the needle dynamic characteristics and injection rate which becomes more obvious with the decrease in injection pressure. Under the action of reflected compression wave, the moment delay of needle reaching the maximum position can reach 0.6 ms, and the gas injection mass can be reduced by 16%.

Water hammer and cavitational hammer in process plant pipe systems

Abstract Fast acting valves are often applied for quick safety shut-down of pipelines for liquids and gases in the chemical and petrochemical industry as well as in power plants and state water supplies. The fast deceleration of the liquid leads to water hammer upstream the valve and to cavitational hammer downstream the fast closing valve. The valve characteristics given by manufacturers are usually measured at steady state flow conditions of the liquid. In comparison, the dynamic characteristics depend on the initial liquid velocity, valve closing velocity, the absolute pipe pressure and the pipe geometry. Fraunhofer UMSICHT conducts various test series examining valve dynamic characteristics in order of the dynamic analysis of pressure surges in fast closing processes. Therefore a test rig is used which consists of two pipelines of DN 50 and DN 100 with an approximate length of 230 m each. In this paper the results of performed pressure surge experiments with fast closing and opening valves will be compared to calculations of commercial software programs such as MONA, FLOWMASTER 2. Thus the calculation software for water supply, power plants, oil and gas and chemical industry can be permanently improved.

Investigation on recognition method of acoustic emission signal of the compressor valve based on the deep learning method

The valve affects the reliability and efficiency of the reciprocating compressor. The Acoustic Emission (AE) technology is applied to nondestructive measurement of compressor valve movement in this paper. Furthermore, the AE signal is analyzed to predict the valves dynamic characteristics of based on the deep learning method. The results show that the prediction accuracy of dynamic characteristics of valve by Convolutional Neural Network (CNN) artificial neural network and Long Short-Term Memory (LSTM) artificial neural network is 94.49% and 96.14%, respectively, which shows that the deep learning method can effectively predict the valve dynamic characteristics. The prediction accuracy of LSTM network is slightly higher than CNN. And the prediction speed of CNN is higher. Based on the models, the delay closing of the valve is analyzed. This paper provides the experimental and theoretical basis for the application of AE technology to the fault diagnosis of the reciprocating compressor.

Effect of High-speed Solenoid Valve Dynamic Characteristics on Downstream Transient Spray Atomization of Bipropellant Thruster

Effect of High-speed Solenoid Valve Dynamic Characteristics on Downstream Transient Spray Atomization of Bipropellant Thruster

A Large-Flowrate On–Off Valve with Hollow Structure for High-Frequency Hydraulic Vibration and Impact System

In high-frequency hydraulic vibration and impact systems, the high-speed reciprocating motion of the impact piston, as controlled by the main valve, transfers energy to the target. Therefore, the main valve must have a fast response speed and strong flow capacity. A novel two-stage large-flowrate on–off valve is developed in this study. The first stage is a small-flowrate servo valve, and the second stage is a large-flowrate hydraulic control valve with a hollow spool. The hollow structure not only reduces the quality of the spool and improves the valve dynamic characteristics but also improves the flow capacity and reduces the pressure drop at the valve port. A structural strength simulation is performed, and the deformation and stress of the spool are calculated. Then, the internal flow channel is extracted and the pressure drop characteristics of valve are obtained by simulation. To obtain the dynamic characteristics of the valve, the control equations of the valve are established, and the simulation model is built in Simcenter Amesim software. Then, the structural parameters of the valve body are optimized in this model. Finally, a prototype is developed for hydraulic vibration and impact systems. The experimental results show that the prototype works well, the opening time of the second-stage valve is within 6 ms, and the port pressure drop at a flow rate of 1000 L/min is only 30% of the conventional opening and closing valve of the same diameter.

The influence of dynamic swash plate vibration on outlet flow ripple in constant power variable-displacement piston pump

The vibration of a swash plate is caused by the piston forces and the control actuator acting on the swash plate. An earlier study of the outlet flow ripple of variable-displacement axial piston pumps assumed a fixed swash plate angle; it ignored the influence of swash plate vibration on the outlet flow ripple of the axial piston pump. In this work, a theoretical model of the outlet flow ripple and pressure pulsation was established in a constant power variable-displacement piston pump. The vibration of swash plate, flow leakage, and valve dynamic characteristics are considered in the theoretical model. The computational results of the theoretical model at different external load pressures are verified by comparison with experimental results. The vibration of the swash plate is strongly influenced by both the piston chamber pressure variation and the control actuator mechanism. The study proved the influence of the swash plate vibration on the outlet flow ripple and the pressure pulsation of an axial piston pump. Compared to the case of a fixed swash plate angle, accounting for swash plate vibration is much more suitable for the accurate determination of the outlet flow ripple and pressure pulsation of an axial piston pump. It is also shown that the vibration of the swash plate affects the valve plate design. Accordingly, valve plate optimization based on the theoretical model of the outlet flow ripple was also studied in this work. The amplitude of the instantaneous outlet flow ripple was considered as the optimization objective function. Finally, the optimized design parameters for a constant power variable-displacement swash plate axial piston pump were evaluated.

サーボ弁の動特性を考慮した静圧軸受エアステージの追従制御

サーボ弁の動特性を考慮した静圧軸受エアステージの追従制御

Trajectory sensitivity analysis of first order and second order on position control system of highly integrated valve-controlled cylinder

A Highly-integrated valve-controlled cylinder (HIVC) that has the advantage of large power weight ratio and fast response is widely applied in many fields. To ensure high performance of HIVC, control strategy selection and structure parameters optimization are essential; thus, performance-influenced main parameters and secondary parameters should be well-grasped to target control compensation and structure optimization. Trajectory sensitivity analysis (TSA), a branch of sensitivity analysis, can be adapted to research on the effects of control and structure parameter variation on system performance; the analysis conclusions can be used to improve system performance and the analysis has been applied in many applications in various fields. In this paper, based on the mathematical model of the First-order trajectory sensitivity analysis (FOTSA), the mathematical model of Second trajectory sensitivity analysis (SOTSA) is further derived; the general expression of the second-order trajectory sensitivity equations and the special expression that is applicable to each system parameter sensitivity analysis of HIVC are built respectively. Furthermore, based on the position control system of the nonlinear mathematical model of HIVC involved with servo valve dynamic characteristics, flow-pressure nonlinearity, initial piston position of servo cylinder, and friction nonlinearity, the coefficient items and the free items matrices of the special expression are calculated. Moreover, the First-order trajectory sensitivity function (FOTSF) and the Second trajectory sensitivity function (SOTSF) of the 17 main parameters in HIVC are computed on the MATLAB/Simulink platform under nine typical working conditions of the displacement step response. Then, the dynamic change rules and the differences and similarities of each parameter sensitivity analysis results are obtained through FOTSA and SOTSA under different working conditions with different parameter variations; each parameter sensitivity variation histogram based on the two kinds of sensitivity indexes, including the maximum value of the percentage absolute value and the absolute value summation within the sampling time, are given. Furthermore, differences and similarities of each parameter sensitivity index change rule and value are quantitatively analyzed. Finally, the sensitivity index change rules and values of the four parameters in the position control system of HIVC, including system supply oil pressure, proportion gain, initial piston position of servo cylinder, and load are experimentally verified. All above studies indicate that each parameter SOTSA result of HIVC vary under different working conditions. When parameter variation is significant, the differences in certain parameter sensitivity analysis between FOSTA and SOTSA are relatively significant; and SOTSA results are more similar to the test results, which illustrates that SOTSA results are more accurate.

Reduction of the flow forces in a small hydraulic seat valve as alternative approach to improve the valve characteristics

In this paper the optimization of the spool and housing geometry in a small hydraulic seat valve to enable the reduction of the axial flow forces to a minimum value is described. Non-optimized hydraulic valve geometry is usually the main cause for many problems related to response time, actuation force and energy consumption. To overcome these limitations and problems we have done a thorough numerical and experimental analysis of a seat valve. The main influential geometry parameters of the seat valve are defined for numerical analyses. In the next step the basic theory of the numerical simulation, including the 3D modelling, meshing and parameterization, is explained. The reduction of the flow forces in a small hydraulic seat valve is treated in detail by using a commercial simulation tool, Ansys CFX. The validation of the numerical fluid model of the valve is done by comparing simulation and experimental results obtained with the test rig for axial flow force measurement. With the validated numerical fluid model of the valve new fluid models are built taking into account all influential geometry parameters of the valve for the purpose of the final optimization of the valve geometry. The results of the simulation analyses show that the axial component of the flow forces can be reduced significantly just by modifying the geometry of the valve spool and housing. Thus the valve dynamic characteristics, such as response time, are significantly improved while the necessary actuation force and power consumption are reduced.

자동차 ESP 유압 모듈레이터의 수격 특성에 관한 연구

본 연구에서는 유압이 작용하는 유압 모듈레이터의 솔레노이드 밸브에 대한 동특성을 실험과 수학적 방법을 이용하여 해석하였다. 마스터 실린더에 작용하는 유압이 솔레노이드 밸브 동특성에 미치는 영향을 해석하였다. 유압장치에서 수격 압력은 소음과 진동 등과 같은 악 영향을 유발하게 된다. 이 수격 압력을 축소시키기 위하여 20kHz 대역의 고속 PWM 제어 방법을 도입하였다. 한편으로, 본 해석을 통하여 자동차 총합자세제어장치에서 발생되는 전자력과 유압 특성을 제안할 수 있었다. 결론적으로, 솔레노이드 밸브의 동특성 해석을 통하여 자동차 전자식 안정화 장치에 대한 제어 기준으로 활용할 수 있음을 확인할 수 있었다. In this study, mathematical modeling and experimental analysis were executed in order to evaluate the valve dynamic characteristics when the hydraulic pressure applied. High pressure on the master cylinder effects on the valve dynamic characteristics have been analyzed. The pulsation pressure generated in hydraulic systems causes noise, vibration and odd effect to the system. To reduce the pulsation pressure, high frequency PWM control of 20KHz was attempted. Also, an analytic method is proposed for the resultant forces of electromagnetism and hydraulic pressure generated in the real vehicle electro stability program. Consequently, results of solenoid valve dynamic characteristics analysis derived in the study can be confirmed criteria for the optimal control of electronic stability program system.

NUMERICAL SIMULATION ON THE DYNAMIC CHARACTERISTICS OF A TWO-STAGE WATER HYDRAULIC RELIEF VALVE

The mathematical model for a novel two-stage water hydraulic relief valve is estabilished. Numerical simulation on its dynamic characteristics is analysed. Simulation results clarify that setting damping chamber at the pilot stage is benefit to improve the pilot valve's stability. The main valve's differential working pressure can be decreased greatly by adding a suitable throttle for the purpose of reducing cavitation, enhancing the valve's performance and service life. The results also show that the upper chamber volume V12 of the main valve, the inlet chamber volume V2 of the pilot valve and the inlet chamber volume V0 of the relief valve influence the relief valve's dynamic characteristics markedly.

Test method of high-speed on-off valve dynamic characteristics

根据高速度开关阀门和它的行动的阀门港口特征，阀门港口能被简化进一种一类型半桥构造。由一半衔接的一类型的产量压力信号测试高速度开关阀门的动态特征的一个方法被建议。分析了与一半衔接的一种一类型的动态特征有关的因素，设计插头房间的体积的一条规则被得出。根据规则，一个测试看台被造测试自我开发的高速度的 on-offvalve。从测试结果，与插头，房间的卷按规则控制了几乎没被信号与不同频率变化驾驶的压力信号的上升时间，这能被看见。测试结果遵循模拟结果，它证明方法的正确性。

State-of-the-Art Review of Pressure Relief Valve Design, Testing and Modeling

It is well known that the response of a rail tank car to exterior heating (e.g., fire engulfment) is significantly affected by the operating characteristics of the pressure relief valve (PRV). If the valve jams or fails in some way, it can lead to a violent vessel rupture; therefore, PRV failure modes and mechanisms must be understood. This paper investigates the studies which have been conducted in the area of PRV technology. The original focus of the paper was to conduct a literature search to find the state-of-the-art for the PRV’s which are presently installed on railway tank cars, highway tankers, and stationary LPG storage vessels. When few papers were found which had concentrated on this particular topic, the authors continued the search by considering both the nuclear power and chemical processing industries, where similar technologies are found. The results of the literature search suggest that the PRV’s currently installed on tank cars and highway tankers are based on designs more than 30 yr old. Controlled fire tests and industry’s maintenance programs suggest that PRV’s could be improved. Most experimental studies of PRV’s have concentrated on flow visualization techniques and have not considered PRV dynamic characteristics. The lack of understanding of valve dynamic characteristics has slowed the development of improved PRV dynamic computer models.