Valve Opening Process Research Articles

Analysis of fluid-structure interaction in diaphragm plug valves for filling electrolyte in lithium-ion battery cells

In this paper, the stress and the local liquid residue of the diaphragm plug valve were simulated. Simulation of the diaphragm plug valve opening process was performed by using a bidirectional fluid-structure interaction based on dynamic mesh technique. The pressure and velocity distribution of the internal flow were obtained with boundary conditions for the fluid–structure interaction during the opening process. The finite element method was used to compare the equivalent stress with FSI method. The results indicate that mechanical tensile stress plays a prominent role in determining the equivalent stress of the diaphragm, with the highest stress concentration occurring in the root region. The electrolyte flow in the valve tends to be stable when reaching an opening degree of 56.6 %. Crystallization accumulation will occur due to the existence of vortices in the flow field around the diaphragm which affects the fluidity of the fluid, this area needs to be focused on.

Study on Transient Flow and Dynamic Characteristics of Dual Disc Check Valve Mounted in Pipeline System during Opening and Closing

Check valves are used extensively in industrial piping systems. Based on dynamic mesh technology, this study uses the RNG k-ε turbulence model to numerically calculate the dual disc check valve’s three-dimensional transient flow. The dynamic characteristics of the check valve in the pipeline system are also experimentally studied. To this end, the two discs are opened synchronously during the valve-opening process, including four stages: opening discs at a constant angular velocity, opening slowing down discs, slowly returning discs to the balance point, and discs maintaining oscillation. However, the movements of the two discs are asynchronous in the valve-closing process. As the downstream pressure increases, the valve disc begins to close, and the flow gradually stops; reverse flow takes shape, and the reverse flow stops until the discs are fully closed, and slamming of the check valve occurs. The non-dimensional dynamic characteristic curve of this type of dual disc check valve has a slope of about 1.624, which mirrors the response of the check valve closing to the occurrence of the water hammer in the system. Knowing the dynamic behavior can be convenient in designing and selecting a check valve and regulating piping system working conditions.

Effect of Upstream Valve Opening Process on Dynamic Spray Atomization of Bipropellant Thruster Injector.

In order to develop a new generation of intelligent satellites, fast-response bipropellant thrusters are required to work in minimum impulse mode without limitation. When a valve is opening, the fluctuation affects downstream spray atomization at the injector, which determines the thruster’s impulse performance, involving combustion efficiency and impulse repeatability. Accordingly, the spray atomization under impulse working condition was investigated to optimize the thruster’s dynamic response. The effects of propellant property, switch speed, valve stroke, and throttle orifice layout are respectively compared in simulation cases using OpenFOAM. The fluctuating flowrate caused by valve opening was simulated and then used as boundary conditions for downstream spray. Among these factors, orifice layout plays the most significant roles in transient spray development. Compared with MMH spray, NTO spray from outer swirl injector is more sensitive to upstream fluctuation. When the upstream flowrate stabilizes faster, the atomization stability can also be enhanced, thereby improving the impulse repeatability of thrusters in combustion. This experimental result was in good agreement with the simulation, thereby showing that only when atomization of MMH spray and NTO spray both develop into a steady state within 5 ms after valve opening can the impulse performance be reliably achieved.

Fluid dynamic analysis of liquefied natural gas flow through a cryogenic ball valve in liquefied natural gas receiving stations

Cryogenic ball valves are one of the most important fluid control devices in liquefied natural gas (LNG) receiving stations. The dynamic flow characteristics of cryogenic ball valves directly affect the stability of a pipeline system. In this paper, the sliding mesh technology was adopted to simulate the dynamic flow characteristics inside the cryogenic ball valve. Firstly, the energy loss inside the cryogenic ball valve during the opening and closing process was analyzed. It is found that the energy loss is larger when the spool degree is less than 30°, while the fluid resistance is very small at the rest of the degree. Then, the dynamic flow characteristics of the cryogenic ball valve at different spool rotational speeds were investigated. It is found that the velocity value and the flow turbulence are gradually increased when the spool rotational speed increases from 1.25 deg/s to 10 deg/s. Finally, dynamic flow characteristics during the valve opening process with fluctuation of inlet velocity were analyzed. It is found that the distribution of velocity and pressure is approximately consistent, while the value of velocity and pressure is increased with the increase of inlet velocity. It is helpful for the design of cryogenic ball valves and the improvement of the whole LNG pipeline system.

Normally closed one-shot isolation valve for micropropulsion systems

A normally closed one-shot isolation valve was developed here to isolate the high-pressure gaseous propellant in micropropulsion systems. The valve has the ability to greatly reduce the amount of metal debris entering and blocking the flow path. Inside the one-shot valve is a hollow-designed starting needle. The starting needle sends two symmetrically placed gas inlets at the top of the needle to the upstream of the isolation device to open the valve. During this process, metal debris is directed downstream of the isolation device by the high-pressure gaseous propellant. This process can greatly reduce the amount of metal debris entering and blocking the flow path through the gas inlets. The one-shot valve was opened at a pressure of 10.6 MPa with a power of 5.6 W. Thermal analysis of the base was conducted during the valve opening process. The volume flow through the starting needle was measured before and after activation. The performance of the valve was mainly analyzed by the volume flow ratio before and after activation.

Transient flow analysis of integrated valve opening process

The control rod hydraulic driving system (CRHDS) is a new type of built-in control rod drive technology and the IV is the key control component. The working principle of integrated valve (IV) is analyzed and the IV hydraulic experiment is conducted. There is transient flow phenomenon in the valve opening process. The theoretical model of IV opening process is established by the loop system control equations and boundary conditions. The valve opening boundary condition equation is established based on the IV three dimensional flow field analysis results and the dynamic analysis of the valve core movement. The model calculation results are in good agreement with the experimental results. On this basis, the model is used to analyze the transient flow under high temperature condition. The peak pressure head is consistent with the one under room temperature and the pressure fluctuation period is longer than the one under room temperature. Furthermore, the changing rule of pressure transients with the fluid and loop structure parameters is analyzed. The peak pressure increases with the flow rate and the peak pressure decreases with the increase of the valve opening time. The pressure fluctuation period increases with the loop pipe length and the fluctuation amplitude remains largely unchanged under different equilibrium pressure conditions. The research results lay the base for the vibration reduction analysis of the CRHDS.

Optimization of valve opening process for the suppression of impulse exhaust noise

Impulse exhaust noise generated by the sudden impact of discharging flow of pneumatic systems has significant temporal characteristics including high sound pressure and rapid sound transient. The impulse noise exposures are more hazardous to hearing than the energy equivalent uniform noise exposures. This paper presents a novel approach to suppress the peak sound pressure as a major indicator of impulsiveness of the impulse exhaust noise by an optimization of the opening process of valve. Relationships between exhaust flow and impulse noise are described by thermodynamics and noise generating mechanism. Then an optimized approach by controlling the valve opening process is derived under a constraint of pre-setting exhaust time. A modified servo-direct-driven valve was designed and assembled in a typical pneumatic system for the verification experiments comparing with an original solenoid valve. Experimental results with groups of initial cylinder pressures and pre-setting exhaust times are shown to verify the effects of the proposed optimization. Some indicators of energy-equivalent and impulsiveness are introduced to discuss the effects of the noise suppressions. Relationship between noise reduction and exhaust time delay is also discussed.

CFD simulation of dynamic characteristics of a solenoid valve for exhaust gas turbocharger system

The transient flow and dynamic characteristics of a PWM-controlled solenoid valve are simulated by CFD to investigate the pressure control performance of the solenoid valve under PWM-controlled conditions. A group of cases with a constant valve opening but different pressure drops are used in the steady-state CFD simulations, which cover both sonic and subsonic flows. The mass flow rates obtained from CFD simulations are compared with theoretical results and show a good agreement, indicating that CFD is capable of handling the complex flows. The dynamic mesh technique is used to simulate the movement of the valve spool, and transient CFD simulations are conducted to analyze the dynamic characteristics. The responses of the control pressure and the mass flow rate to the duty-cycle variation are analyzed for 30%, 50%, and 80% duty cycles. The mean control pressure values are verified by experimental data. The flow force exerted on the spool is recorded and the transient force is compared with the steady force. The pressure wave transmission during the valve opening process is captured. The influence of the valve opening time on the control pressure is also investigated, and results show that the former can affect the mean control pressure.

Sensitivity Analysis of Operational Time Differences for a Pump–Valve System on a Water Hammer Response

Pumps and valves are primary power and control devices in water supply piping systems. A collaborative operational scheme is very important for a series pump–valve system to decrease the transient pressure during the startup process. In order to analyze the influence of the operational time differences between the pump and the valve on the transient process, a complicated pump system was numerically simulated using the method of characteristics (MOC). The boundary conditions of the pump and the valve were separately established by equating an auxiliary element in the discrete mesh. The transient pressure, pump speed, and flow were studied for various time differences and the valve opening process for the series pump–valve startup process. Furthermore, an optimal collaborative scheme was presented to prevent inverse rotation and overpressure during the startup process. The results show that a reasonable time-lapse and fast opening can prevent the backward flow and reverse rotation, as well as control the transient maximal pressure during the system startup process.

Effects of multiple factors on the stress of the electro-hydraulic directional valve used on the hydraulic roof supports

The large flow electro-hydraulic directional valves are the key operating components for automation of the hydraulic roof supports in the coal mine. Cracking is a common failure mode of the valve. Effects of the buffer damp diameter, the valve type and the static pressure on the stress of the valve were researched. The valve dynamic behavior was investigated by AMESim. The transient collision stresses of the inlet valve sleeve of the main control valve under different buffer damp diam- eters and different valve types were investigated by ANSYS/LS-DYNA. The static stress analysis was conducted in ANSYS too. Results show that the valve failure is due to the fatigue of the inlet valve sleeve when suffered from the collision stress wave in the valve opening process, rather than the lack of component strength. The buffer damp diameter, the key parameter of the valve, has a significant effect on the collision stress of the inlet valve sleeve. The integrated type valve has a better stress state compared to the separated type valve. This paper provides an effective method to solve the fracture problems of hydraulic directional valves. It is also significant for the design and optimization of hydraulic components.

A new dry tray pressure drop model of float valve trays

An accurate prediction of the dry pressure drop is very important for consideration of valve trays and for calculations in distillation field. Therefore, in this article, a series of hydraulic experiments were first conducted to reveal that the intermediate state during the valve opening process is closely related to the dry tray pressure drop under great valve weight. Then, a rigorous force analysis was made to show that Euler number is related only to the valve's position at the balance points for a certain valve type. Third, a new model for prediction of the dry tray pressure drop—which considers for the first time the influence of the intermediate state—was developed and then simplified for the purpose of convenient utilizations. Finally, the new model and its simplified form were tested by comparisons with the experimental results. The agreements are good, with the mean deviations being <5%. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2694–2705, 2013

Opening Delay of a Reed Valve for Refrigerant Gas Discharges in Compressors (Visualization of Oil Film Behaviors and Measurement of Valve Deformations in the Opening Process)

Automatic reed valves are widely used to control refrigerant gas flows in reciprocating compressors for automotive air conditioners. The oil film in the clearance between the reed and the valve seat causes a delay in opening of the valve. This opening delay of the discharge valve leads to over compression, which increases losses in the compressor. This study aims to develop an experimental setup that enables simultaneous visualization of the oil film rupture and measurement of the reed deformation, and to observe this behavior during the valve opening process. The gas-compression stroke is simulated by controlling compressed air with an electromagnetic valve. The oil film rupture is visually observed using a high speed camera through a special valve seat made of glass. The total deformation of the cantilever reed is identified by multipoint strain measurement with 12 strain gauges. The experiment finds that the opening process is divided into four stages. In the first stage, the reed remains stuck to the seat and deforms while the bore pressure increases. In the second stage, cavitation occurs in the oil film and the film starts to rupture. In the third stage, the oil film ruptures and the bore pressure starts to decrease. Finally, in the fourth stage, the reed is separated from the seat and the gas flows through the valve. Reducing the reed/seat contact area changes the reed deformation in the first stage, thereby increasing the reed/seat distance and realizing an earlier oil film rupture and a shorter delay.

Design and transient analyses of emergency passive residual heat removal system of CPR1000

The steam generator secondary emergency passive residual heat removal system (EPRHRs) is a new design for traditional generation II + reactor CPR1000. The EPRHRs is designed to improve the safety and reliability of CPR1000 by completely or partially replacing traditional emergency water cooling system in the event of the station blackout or loss of heat sink accident. The EPRHRs consists of steam generator (SG), heat exchanger (HX), emergency makeup tank (EMT), cooling water tank (CWT), and corresponding pipes and valves. In order to improve the safety and reliability of CPR1000, the model of the primary loop and the EPRHRs was developed to investigate residual heat removal capability of the EPRHRs and the transient characteristics of the primary loop affected by the EPRHRs using RELAP5/MOD3.4. The transient characteristics of the primary loop and the EPRHRs were calculated in the event of station blackout accident. Sensitivity studies of the EPRHRs were also conducted to investigate the response of the primary loop and the EPRHRs on the main parameters of the EPRHRs. The EPRHRs could supply water to the SG shell side from the EMT successfully. The calculation results showed that the EPRHRs could take away the decay heat from the primary loop effectively, and that the single-phase and two-phase natural circulations were established in the primary loop and EPRHRs loop, respectively. The results also indicated that the effect of isolation valve open time on the transient characteristics of the primary loop was little. However, the effect of isolation valve open time on the EPRHRs condensate flow was relatively greater. The isolation valves should not be opened too rapidly during the isolation valve opening process, and the isolation valve opening time should be greater than 10 s, which could avoid the steam impact on the EPRHRs, and improve the stability of the system.

A New Method Solving Contact/Detach Problem in Fluid and Structure Interaction Simulation with Application in Modeling of a Safety Valve

A new virtual baffle methodology is implemented to solve contact/detach problem which is often encountered in fluid and structure interaction simulations while using dynamic grids technique. The algorithm is based on tetrahedral unstructured grid, and a zero thickness baffle face is generated between actually contacted two objects. In computation process, this baffle face is divided into two parts representing convective and blocked area, respectively; the area of each part is calculated according to the actual displacement between the two objects. Convective part in a baffle face is treated as inner interface between cells, and on blocked part wall boundary condition is applied; so convective and blocking effect can be achieved on a single baffle face. This methodology can simulate real detaching process starting from contact, that is, zero displacement, while it has no restriction to minimum grid cell size. The methodology is then applied in modeling of a complicated safety valve opening process, involving multidisciplinary fluid and structure interaction and dynamic grids. The results agree well with experimental data, which proves that the virtual baffle method is successful.

Numerical modelling of the opening process of the three-coating aortic valve

Numerical modelling of the three-coating human aortic valve is the objective of the paper. The proposed approach is used to select the material properties and the thickness of outer coating of the valve, which are required to obtain the proper work of the valve, which in the present paper is considered as the opening process. Following the previously developed model of the monocoating leaflet of the natural human aortic valve, the model of three-coating valve is prepared. Finite element method (FEM) and sensitivity analysis are used to solve the formulated and selected problems. Two methods of estimation of the valve opening process in numerical models are elaborated on the basis of experimental studies.

INVESTIGATION OF SHEAR FIELDS ACROSS MECHANICAL HEART VALVE MODEL

Purpose of Study: The dynamic flow field of a mechanical heart valve (MHV) is complex because of the moving boundary of its occluder. One special interest in MHV study is to link the flow dynamics to valvular hemolysis and thrombosis. In vitro experiments were carried out to investigate the shear stress distribution around the bi-leaflet MHV model for a complete cardiac cycle. Material and Method: A pulsatile test loop simulating physiological pressures and flow rate was constructed. A transparent bi-leaflet model was installed and particle image velocimetry (PIV) technique was used in this investigation. The cyclic signal from the occluder motion developed for PIV trigger. Results: The MHV occluders demonstrate symmetric motion and also good repetitiveness among various cycles in the valve opening process. The maximum flow velocity reaches 1.7 m/s at peak systole. After systole, the forward flow momentum decelerates until backflow initiates inside the central channel. The viscous shear stress and major Reynolds shear stress is increasing continuously till peak systole, with the maximum value up to 500 N/m2. Large stress is observed around the hinge zone and occluder trailing tip, causing by the central jet separation and wake formation. In the closing process, relative large stress is produced by the inhomogeneous flow in the middle section of the central channel. Conclusion: The simultaneous investigation of the occluder dynamics and the flow field provides more insights to the fluid-structure effect around MHV. The maximum shear stress in this work is found larger than the normal threshold for hemolysis.

Optic diagnosis of neutral beam injection on HL-1M

During the operation of a high-power neutral beam injection (NBI) system on the HL-1M tokamak, an optical diagnostic means using CCD camera was developed to characterize the NBI performance. The vacuum valve opening process and NBI period in the HL-1M experiment were displayed by a lot of photos taken with this means. Thus, the Hα emission profiles of the neutral beam (NB) and its interaction with plasma were given. Finally, the reason possible for plasma breakdown during NBI mode II discharge was investigated. Therefore, this in-situ diagnosis can provide more information of the NBI.