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This paper is to investigate the effects of valve parameters on the performance of a trans-critical refrigeration compressor numerically. A numerical model has been implemented in Matlab based on mass balance, first thermodynamic law, NIST REFPROP database for gas properties and thermodynamic relationships. Good agreement is indicated by comparing numerical results with our previous measured data. The impact of key parameters such as: valve lift, spring stiffness, valve plate mass and valve port area are particularly evaluated on variation of valve displacement, valve speed, in-cylinder pressure and in-cylinder mass. Results demonstrate that: with lift increasing valve plate will not remain open to the limiter for a while but bounce back to seat after hitting the limiter; the valve plate mass has significant influence on both the opening motion and the closing motion of valves.

This paper focuses on the open-center multi-way valve used in loader buckets. To solve the problem of excessive flow force that leads to spool clamping in the reset process, joint simulations adopting MATLAB, AMESim, and FLUENT were carried out. Boundary conditions play a decisive role in the results of computational fluid dynamics (CFD) simulation. However, the boundary conditions of valve ports depend on the hydraulic system’s working condition and are significantly impacted by the port area, which has always been neglected. This paper starts with the port area calculation method, then the port area curves are input into the simulation hydraulic system, obtaining the flow curves of valve port as output, which are then applied as the boundary conditions of the spool valve CFD simulation. Therefore, the steady-state flow force of the spool valve is accurately calculated, and the result verifies the hypothesis that excess flow force causes spool clamping. Based on this, four kinds of structures were introduced in an attempt to improve the situation, and simulating calculation and theoretical analysis were adopted to verify the effects of improvement. Results show that the four structures could reduce the peak value of flow force by 17.8%, 60.6%, 61.6%, and 55.7%, respectively. Of the four, structures II, III, and IV can reduce the peak value of flow force to below reset spring force value, thus successfully avoiding the spool clamping caused by flow force.

High speed on-off valve is the core component of digital hydraulic technology. The valve port pressure pulsation caused by high frequency pulse directly affects the response and stability of the system. It is aimed at the pressure pulsation problem of normally open high speed on-off valve at high speed. Through theoretical analysis, the AMESim model is established to simulate and analyze the influence of the valve core on the valve port pressure. The finite element analysis of the flow field of the high speed on-off valve is carried out to obtain the pressure cloud and velocity map of the valve core. The valve pressure pulsation was tested and verified. Combined with the analysis results, theoretical guidance is provided for the high-speed on-off valve to reduce pressure pulsation during structural design.

a novel intelligent trace irrigation system based on pneumatic microfluidic chip for applications of expensive flower cultivation and seed cultivation is presented in this paper. The working principle and structural design of intelligent trace irrigation system are introduced. On-chip membrane microvalves on the pneumatic microfluidic chip are used as the water-saving device. The physical model of PDMS valve-film, on-chip membrane microvalve and intelligent trace irrigation system are given. The deformation of the flexible PDMS valve-film with different dimensions is analyzed by using ANSYS analytical software to get different valve-openings of the valve port. The numerical simulation of flow field under several valve-openings of the single on-chip membrane microvalve, and the manifold with different sets of the pneumatic microfluidic chip is carried out by using FLUENT software with UDF Function. The predicted characteristics of velocity, pressure, and flow rate of the on-chip membrane microvalve outlet under the conditions of different valve-openings of the intelligence trace irrigation system are given. According to the simulated results in this work, the on-chip membrane microvalve in parallel has both wide water-control range and fine regulation of flow rate. The simulation results confirm it is sufficient for the intended application.

In this paper, a digital hydraulic variable control method based on multi-way valve spool displacement feedback is proposed, which combines the advantages of low cost and high reliability of the loader fixed displacement pump hydraulic system, and the distinguished energy saving effect of the loader variable pump hydraulic system. Based on the principle of hydraulic resistance, the mathematical model of flow-pressure of multi-way valve was established. Meanwhile, the theoretical structure of a valve spool suitable for digital hydraulic system was deduced. On this basis, an improvement scheme of the valve spool was proposed in combination with machining feasibility. The simulation model of multi-way valve was established, the correctness of which was verified by experiment with the significance test method, and the valve port parameters of the multi-way valve were optimized by genetic algorithm. The simulation model before and after optimization was analyzed by AMESim software. The simulation results showed that the digital hydraulic system can basically realize the function of a variable system, and the energy consumption was significantly reduced compared with the fixed displacement pump hydraulic system. The optimized valve spool structure of the digital hydraulic system had more stable load characteristics than the fixed displacement pump system and a larger speed range. The increase range accounts for about 27% of the total stroke.

A superimposed hydraulic back pressure valve with adaptive back pressure was designed. The back pressure of the valve changes as the diving depth of underwater vehicles changes, and is always higher than outboard environmental pressure by an adjustable value, preferred 0.5MPa, to avoid leakage of environmental medium to the inboard hydraulic system. The valve was designed in a pilot-operated style with a flat valve port of main valve. Variable damping plugs were used to easily regulate the dynamic performance of the valve. And an isolation device was adopted to isolate the contact between the inboard and outboard media. The static mathematic models of the valve were established and simulations were carried out. The simulation results show the valve has good pressure stability and flow adaptability, and its back pressure changes with the change of outboard pressure well.

According to the cone-type throttle valve is prone to cavitation, resulting in the reduction in the performance of the cone throttle valve. Here, a visual experimental platform for hydraulic cavitation is built, and the cavitation number of the conical throttle valve under different working pressure, opening degree, and different back pressure is studied. The cavitation image under different conditions is obtained. The research shows that properly increasing back pressure, reducing system working pressure, and keeping small opening of the valve port can restrain cavitation.

Typical slewing valve is a three-position six-way proportional valve based on bypass throttle principle, whose output flow rate and opening dead zone of the main valve port are both affected by the load. Thus, it has poor performances in dynamic control of varying loads. This article presents a novel slewing valve based on bypass pressure-compensation principle, which has much better performance in dynamic control of varying loads and even for large inertia loads. A pressure-compensated valve is added to connect the out ports of the main valve port and the bypass port to keep the pressure differences at the main valve port and the bypass port in same. As a result, the flow distribution ratio of these two ports keeps stable for a certain spool position, which can avoid the output flow rate fluctuation despite the varying loads. In addition, the opening dead zone of the main valve port is very small and keeps almost unchanged. These advantages make the proposed valve to control large inertia load with great stability. In the article, a mathematical model formulating the dynamic performance of the valve is further established to provide guide for the optimization of the parameters, including the shapes and orifice areas of the main valve port and bypass port, the stiffness of the spring controlling spool motion, and so on. A prototype valve was manufactured based on the presented method. A series of tests on experiment bench and real crane validate its great performances on flow rate and dead zone stabilities as well as fast dynamic response.

The main rejections in the machining sections are exhaust valve port leak, injector bore blow hole, induction passage punchered, inlet valve port leak, top face unwash, valve guide hole blow hole, top face leak, joint face unwash, induction face unwash, rear face unwash, valve port unwash, water mixing with oil., water passage blocked, emf leak, injector bore leak, inlet valve port blocked, water way leak, oil way leak and defective jig location pad. This paper describes the method by which the rejections while maching the cylinder head, is minimized.

A compensation algorithm, based on the steady-state fluid force of spool, was proposed to reduce the error between the actual and theoretical spool displacement obtained from indirect measurement method and equilibrium of the pilot pressure and spring force, respectively. The steady-state fluid force of spool was calculated and the force analysis was carried out on the spool. Study on the influence of the steady-state fluid force on spool displacement during the spool movement. Finally, the relationship curve between the compensated flow area of valve port and the spool displacement was established. The error of spool displacement was effectively reduced and the accuracy of the test was improved by the proposed compensation method, thus it can provide certain reference value for the design of multi-way valves.

In the hydraulic system, when the hydraulic oil flows through the valve port and the pressure difference between the front and back of the valve port is large, a large number of bubbles will be produced, and the phenomenon of luminescence of hydraulic oil may even occur. In this paper, the influence of the pressure difference before and after the port of the hydraulic throttle cone valve on the luminescence of hydraulic oil is studied using simulation analysis and experiments. It is found that, with the increase of pressure difference, the luminescence phenomenon of hydraulic oil becomes more obvious.

Hydrodynamic force is one of the important factors to be considered in the design of hydraulic valves. In this paper, mathematical formula of steady hydrodynamic force was deduced basing on non-circular opening spool valve structure and working principle. The simulations were carried out with software FLUENT at differential pressure, different valve port openings, and then the variation of the steady hydrodynamic force can be obtained. The results show that the direction of the steady hydrodynamic force is opposite to the movement of the valve spool and tends to close the valve port; the magnitude of the steady hydrodynamic force is proportional to the valve opening and differential pressure respectively.

The dynamics of a direct operated relief valve with directional damping have been studied through Bondgraph simulation technique. The governing equations of the system have been derived from the Bondgraph model. While solving the system equations numerically, the pressure-flow characteristics of the valve port and the damper unit have been taken into consideration. From this study, some significant parameters of the valve response are identified, which can be modified to improve the dynamic characteristics of the valve.

The mixture formation in a single-cylinder, optical port-injected gasoline engine was investigated for both closed- and open-valve injection strategies with a combination of phase Doppler anemometry, laser-induced fluorescence and Mie scattering and correlated with combustion development and exhaust emissions. Detailed crank angle resolved data of the flow and mixture distribution during induction and compression have revealed the advantages of early open-valve injection, in terms of extending the lean limit and maintaining satisfactory engine performance and HC/NOx emissions, achieved through charge stratification in the vicinity of the spark plug at the time of ignition.

Hydraulic gap control system is the inner loop of automatic gauge control system, and the dynamics of hydraulic gap control system is the key factor for the high precision gauge control effect. The dynamics of hydraulic gap control system is influenced by a non-linear part since the oil flow of valve port depends not only on the control current but also on the changing rolling force. This influence is compensated by a method with compensation factor based on actual rolling force. The application indicates that the dynamics of the hydraulic gap control system is improved greatly with compensation.

The working principle of Augment Common-Rail Injection System. The reason and the influence of pressure oscillation in the pumping chamber of the electric-controlled pressure amplifier were analyzed. Designed the slide-valve plunger coupled parts which could eliminate the severe pressure fluctuation during the pumping chamber while the effect of pressurizing wasn't weaken. The influence caused by the position of valve port and shape of valve port and size of valve port were analyzed. The prototype was manufactured and the experimental investigation on this was carried out.

This paper introduces a certain type of special hydraulic truck crane counter balance valve structure and working principle of the establishment of a counter balance valve using AMESim software model and carry out time-domain and frequency domain characteristics of the simulation analysis, identify the issues affecting the performance of the main counter balance valve structural parameters of the relevant parameters of the amendment. At the same time through experimental research of the counter balance valve dynamic characteristic to verify the correctness of the simulation model. The results show that the counter balance valve main spool of the valve port opening has nothing to do with the load, gain good dynamic and static characteristics.

Theoretical guidelines of selecting the inlet-outlet port sizes, their position and sequences of the flow distributor valves used in epitrochoid generated rotary piston machine type hydrostatic units have been established in the present analysis. The formulae can also be used for programmable control of the inlet-outlet port sequences where a separate valve is used instead of the conventional distributor valve.

This paper presents a linear throttling groove, which could make the area of flow section directly proportional to the size of the entrance. When the linear throttling groove is used on the electromagnetic proportion throttle valve, it can achieve the discharge through valve port and the displacement of valve core with a regular linear change, and when the throttle valve is used with proportional electromagnet, which can achieve proportional control between the valve port discharge and the electrical signal easily. Simulating the steady state characteristics of electromagnetic proportion throttle valve with the MATLAB based on its practical working environment, we could get the flow characteristic curve at different valve port sizes, the stiffness characteristic curve and the relation curve between valve port sizes and the flow. Then we analyze the simulation results. The analysis results have an important guiding significance for the design parameters optimization of the electromagnetic proportion throttle valve.

The necessity to achieve ever shorter development cycles demands more and more the use of “simultaneous engineering” processes. To link together the phases of design, simulation and machining (prototyping) increasingly requires extensive graphical tools, the combination of various calculational and experimental methods and advanced production techniques. Furthermore a high degree of integration is demanded.

The object of this paper which deals with the phenomena at the end of injection of Bosch pump injection system is to show the relation between the design of fuel injection equipment and the pressure drop at the pump side. It was found from experiments that the pressure drop had two features. Pressure at the pump side drops down along a fundamental pressure drop curve. The fundamental pressure drop is a function of cam angle, but not of engine speed. The pressure drop along this curve has a maximum value which is determined mainly by the design of the delivery valve of the pump. The theoretical equations of pressure change and flow through the delivery valve port are obtained after reasonable treatment. Assuming suitable factors, the solution of these equations coincided very well with the experimental results.

The object of this paper which deals with the phenomena at the end of injection of Bosch pump injection system is to show the relation between the design of fuel injection equipment and the pressure drop at the pump side. It was found from experiments that the pressure drop had two features. Pressure at the pump side drops down along a fundamental pressure dropping curve. The fundamental pressure drop is a function of crank angle, injection pipe area, etc., but not of engine speed. The pressure drop along this curve has a maximum value which is decided mainly by the design of the delivery valve of the pump. The theoretical equations of pressure change and flow through the delivery valve port are obtained after reasonable treatment. Assuming suitable factors, the solution of these equations coincided very well with the experimental results.

Despite increasing efforts of manufacturers, the balloons of Foley catheters still on occasion will not deflate. This is probably more common in pure latex catheters due to their gradual absorption of water. Other causes of non-deflation include blockage of the lumen by foreign bodies and collapse of the lumen below the balloon due to a weak wall. Various methods have been described to remove these catheters.‘s2 In our experience, the valve port often has been cut in

In summary we will look at the working functions of the combined system. With the catheter connected, the pressure will be transmitted from the source through the stopcock, the T connector, the tubing, the zero valve Port b 2 to Port a 2 into the transducer. During a flush the saline flows from Port A to Port C of the flush valve through the T connector and stopcock into the catheter. Simultaneously the flush pressure is transmitted to the transducer to show the frequency response of the system. During the zero-reference recording, Port a 2 of the zero valve moves to Port c 2 , deadending Port b 2 , hence the catheter can be flushed without disturbing the zero-check or base-line recording. The system, either combined with all features or in parts, depending on various situations, will prove safe and efficient. The complete system as described is presently used in the Catheterization Laboratory at the University of Utah Medical Center.