Hydraulic valve that allows flow in one direction only LibraryDirectional Valves GATE, GLOBE & CHECK VALVES GATE VALVES Gate valves serve as efficient on-off valves with flow in either direction. In such a design, a wedge slides cross a general passageway in order to control fluid flow (like a sliding gate - hence, the name). One of the most significant characteristics of this type of valves. DescriptionThe Check Valve block represents a hydrauliccheck valve as a altimg-valign='-7px' display='block'>Îp=pAâpB,. The valve remains closed while pressure differential acrossthe valve is lower than the valve cracking pressure. When crackingpressure is reached, the valve control member (spool, ball, poppet,etc.) is forced off its seat, thus creating a passage between theinlet and outlet. If the flow rate is high enough and pressure continuesto rise, the area is further increased until the control member reachesits maximum. At this moment, the valve passage area is at its maximum.The valve maximum area and the cracking and maximum pressures aregenerally provided in the catalogs and are the three key parametersof the block. In addition to the maximum area, the leakage area is also requiredto characterize the valve. The main purpose of the parameter is notto account for possible leakage, even though this is also important,but to maintain numerical integrity of the circuit by preventinga portion of the system from getting isolated after the valve is completelyclosed. An isolated or âhangingâ part of the systemcould affect computational efficiency and even cause failure of computation.Therefore, the parameter value must be greater than zero. By default, the block does not include valve opening dynamics,and the valve sets its opening area directly as a function of pressure: Adding valve opening dynamics provides continuous behavior thatis more physically realistic, and is particularly helpful in situationswith rapid valve opening and closing. The pressure-dependent orificepassage area A(p) in the block equations then becomesthe steady-state area, and the instantaneous orifice passage areain the flow equation is determined as follows: In either case, the flow rate through the valve is determinedaccording to the following equations: A(p)={Aleakfor p<=pcrackAleak+k·(pâpcrack)for pcrack<p<pmaxAmaxfor p>=pmax where
The block positive direction is from port A to port B. Thismeans that the flow rate is positive if it flows from A to B, andthe pressure differential is determined as Îp=pAâpB,. Basic Assumptions and Limitations
Parameters
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