Due to the large energy consumption as well as poor controllability and other problems, the traditional cooling system has not been able to adapt to the development needs of construction machinery ...with the continuous upgrading of emission regulations. This paper introduces a hydraulic driven fan cooling system based on pilot operated electro-hydraulic proportional valve. In order to make the whole machine quickly reach the temperature required in the best working condition when the construction machinery starts working, controlling the fan at a lower speed can reduce the heat dissipation and save energy. The electronic control system will adjust the motor speed in time when the temperature of the fluid rises, and control the temperature in the best temperature range required. A one-dimensional simulation model of this stepless speed control system is established to predict the parameter sensitivity of the electro-hydraulic proportional valve and the dynamic performance of the system. The simulation shows that the fan speed of the system can reach the required speed in only 5s at the extreme high temperature of 40 °C; the fan input power of the system accounts for 65% of the system input power at −30 °C and reaches 80% at 40 °C. Three-dimensional simulation shows that the fan-front temperature-controlled cooling system for forklift truck has high heat dissipation efficiency and can be applied to other heavy machinery products.
•A hydraulic driven cooling system simulation model is developed.•Parameter sensitivity with pilot relief valve is analyzed.•Dynamic behavior of the system at extreme temperatures is predicted.•Heat transfer efficiency of the system is improved.•Thermal equilibrium temperature is well controlled.
In this study, the electro-hydraulic servo system for speed control of fixed displacement hydraulic motor using proportional valve and (PID) controller is investigated theoretically ,experimentally ...and simulation . The theoretical part includes the derivation of the nonlinear mathematical model equation of (valve – motor ) combination system and the derivation of the transfer function for the complete hydraulic system , the stability test of the system during the operation through the transfer function using MATLAB packageV7.1 have been done. An experimental part includes design and built hydraulic test rig and simple PID controller .The best PID gains have been calculated experimentally and simulation, speed control performance tests for the system at different thermal conditions for hydraulic oil have been done , Simulation analysis for (EHSS) using Automation Studio package V5.2 have been done . Comparison was made between experimental work and simulation work .The experimental results show good performance for (EHSS) using simple (PID) controller at hydraulic oil temperature around (60 – 70 ) and good speed response and performance for hydraulic motor with constant rotation speed (700) rpm with different load disturbance applied on the hydraulic motor .
•Effects of cavitation upon a proportional directional valve are investigated.•A very accurate full 3D mixture model is employed to predict cavitation.•The reduction in the flow rate and the change ...of the driving forces are quantified.•The zones where cavitation occurs are identified.•The incipient cavitation number is calculated.
This paper evaluates the effects of cavitation upon the performance of a hydraulic, proportional, directly-operated, directional valve by means of thorough experimental and numerical investigations. The experimental campaign is performed to estimate how cavitation changes the performance curves of the valve; in particular, the experimental equipment assembled to control the cavitation phenomenon inside the proportional valve is described, and the influence of cavitation on the flow rate and the flow coefficient as a function of the spool position is assessed. In addition, a full three-dimensional mixture model of the flow field within the valve is developed to accurately predict cavitation within the flow path for several spool positions. The accuracy of the numerical model is proven by previous experiences and by comparing the numerical results with the experimental data. After their validation, the numerical predictions are employed to analyse the characteristics of cavitation that cannot be experimentally evaluated, such as the volume of vapour, and to identify the zones where cavitation occurs. The numerical simulations are finally employed to predict how the variation in cavitation intensity influences the driving forces required to move the sliding spool and to calculate the minimum cavitation number for which the effects of cavitation are negligible.
In this paper, attention was focused on identifying the components of the amplitude-frequency spectrum of pressure pulsations in a hydraulic system in which an external low-frequency mechanical ...vibration was subjected to a proportional hydraulic directional control valve. It was observed that an operating machine or device equipped with hydraulic valves is a source of mechanical vibrations with a wide frequency spectrum. The influence of these vibrations on the pressure pulsation spectrum was analyzed, identifying the components resulting from the forcing of the directional control valve spool. In addition, it was noted that the pressure pulsation spectrum includes components resulting from the pulsation of the displacement pump output feeding the hydraulic system. A description of these spectrum components was also made and, using the solution superposition method, the components of the pressure pulsation spectrum over a wide frequency range were identified.
Electrohydraulic proportional-control valves now match or exceed the performance of most industrial-grade servovalves. Better hardware and electronic controls yield systems that are more reliable, ...easier to use, and stand up to the toughest environments. From the user's standpoint, valve improvements lie in 3 primary areas: 1. electronic interfacing, 2. frequency response, and 3. zero-overlap spools. Faster response, zero-lap spools, and digital controllers have opened up a number of opportunities that were previously not possible with proportional-valve systems, including synchronizing 2 cylinders, positioning machine-tool slides, and smoothly controlling motion in animation simulators. High-response proportional valves are bringing the benefits of high-level motion control to hundreds of applications where the high cost of servovalve control made this level of sophistication impractical.
This paper presents a novel two-dimensional maglev servo proportional cartridge valve (2D maglev valve), where a contactless maglev coupling is introduced between electro-mechanical converter and ...valve body to realize functions of force transmission, spool position feedback and linear-rotary motion conversion. Such configuration can effectively reduce cost of both valve manufacturing and electro-mechanical converter, while still maintain features of 2D valve such as null pilot leakage, high power-to- weight ratio and excellent anti-pollution capacity. Firstly, the characteristic equation of the valve is derived using linear theory, and the stability criterion is established for parameter determination. The influences of crucial structural parameters such as initial height of overlapping area, width of high-pressure and low-pressure holes, acting radius of magnetic force, pitch angle of maglev coupling, length of sensitive chamber and system pressure on the dynamic response are investigated based on AMESim numerical simulation. The prototype valve is then designed and manufactured and a special test rig is built. The no-load flow characteristic, load flow characteristic, leakage characteristic, amplitude and phase frequency characteristics and step response under different system pressures are measured. The experimental results are in a good agreement with the simulated analysis. As an over-damped system, the prototype valve has excellent working stability, which can reach a no-load flow rate of 105.9 L/min with hysteresis of 3.51%, amplitude bandwidth of 28.7 Hz and phase bandwidth of 42.8 Hz under 21 MPa. The research indicates that the 2D maglev valve can be a potential solution of flow rate control valve for flight control surface system of civil aircraft with high pressure and large flow rate application.
The gas proportional valve (GPV) is a pneumatic pressure regulator, and the change in operating pressure will directly affect the opening and closing condition of the spool. In this study, the ...procedure for opening the spool is studied. The process of regulating the pressure of the GPV is revealed by the dynamical simulation method. The characteristics of displacement, total pressure and velocity of the spool during opening are analyzed. As time increases, it is found that the turbulence in the downstream of GPV becomes more obvious. In the process of spool movement, the influence of different inlet working pressures on spool displacement is analyzed. With a full open time of less than 1.5 × 10^ (−2) s, the spool reaches the stable state of full opening. In addition, the transient process of outlet flow is also studied. The simulated outlet flow is stable at 152 m3/h for the maximum opening. In order to verify the simulation results, the test of valve flow is carried out on the test bench. The results show that these methods can reduce the design difficulty and provide a reference for further optimization and engineering application of GPV.
•The dynamic numerical simulation of GPV is carried out by CFD.•The force of the spool opening process is analyzed by mathematical method.•A UDF program is developed to simulate the transient opening process of spool.•The influence of pressure variation on spool opening is analyzed by transient process.•The outlet flow of GPV is analyzed by transient process.
This article discusses the dynamic behavior of a spool plunger with a modernized drive. Modernization of the drive consists in replacing the electromagnet with a stepper motor with the transformation ...of rotational motion, — with the help of a screw pair, — into a rectilinear one. The contact between the ends of the screw and the plunger is provided by a spring. The value of the preliminary compression of the plunger to the end of the screw is assigned on the basis of guaranteed operation without loss of contact, due to which the plunger practically does not respond to disturbances and is devoid of an oscillatory component during the transient process. The mathematical model includes the influence of fluid friction and hydrodynamic force arising from pressure loss on the distributor 4 MPa. The study of the dynamics of the plunger consists in the accelerated retraction of the screw — which is in force contact with the end face of the spool — and the determination of the limit values of acceleration as a function of the preload force.
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.
•Analyzing and compensating the flow force in a cartridge proportional valve.•A optimization for a compensation device is proposed in this paper.•Negative effect from flow force can be almost neglected after optimization.•The optimization method may provide a guidance for other compensation device.
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 analysis focuses on the compensatory impact of the tilt of the P-port shoulder in the servo-proportional valve on the steady-state flow force.•A scheme for compensating the steady-state flow force is proposed, ensuring that the through-flow capability of the servo-proportional valve remains unaffected.•A dedicated test bench is designed to accurately measure the steady-state flow force.
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