Week 9 - Parametric study on Gate valve.

THEORY:

A gate valve also known as a sluice value is a valve that opens by lifting a barrier out of the path of the fluid gats valves required very little space along the pipe axis and hardly restrict the flow of fluid when the gate is fully opened. the gate faces can be parallel but are most commonly wedge shaped in order to be able apply pressure on the sealing surface.

gate valve are used to shut off the flow of liquid rather than for flow regulation. when fully open the typical gate valve has no obstruction in the flow path resulting in very low flow resistance. the size of the open flow path generally varies in a nonlinear manner as the gate is moved this means that the flow rate does not changed evenly with stem travel. depending on the construction a partially open gate can vibrate from the fluid flow.

Gate valves are mostly used with large pipe diameter from 2" to the largest pipelines since they are less complex to construct than other types of valves in large sizes.

At high pressure friction can become a problem as the gate pushed its guiding rail by the pressure of the medium it become harder to operate the valve. large gate valve are sometimes fitted with a bypass controlled by a smaller valve to be able to reduce the pressure before operating the gate valve itself. Gate valves without an extra sealing ring on the gate or the seat are used in application where minor leaking of the valve is not an issue such as heating circuits or sewer pipes

here in this project parametric study is performed at various valve position mass flow rate is checked at various valve position.

GEOMETRY:

Fluid volume extration:

inlet and outlet extraction is made for fully developed flow entrance in valve.

mesh:

The mesh is fine with an element size of 10mm for each design point the no. of cell change for each design point but the refinement level remains more or less the same the mesh for 10mm gate rise & mesh settings are as shown above.

Turbbulence model:

For reduced computational effort RANS based realizable k-eplision turbulance model is used with scalable wall for near wall modeling scalable wall function enforce the usage of the log law in conjunction with the standard wall function approch even in the range 11.225<y+<30. this helps avoid problems of succesive refinements is standard wall function meshes.

Time= steady state

Type= pressure based system

fluid = water

Scheme= simple second order upwind scheme is used

standard initilization is done

Boundary condition =inlet= pressure 10 pascal

Initial simulation:

The residual and mass flow rate plot is shown below it can be seen that mass flow rate convergence about 250 iteration and residual shown repetative patterns hence all simulation were out for 300 iteration.

convergence plots are similar for all cases.

PARAMETRIC TABLE: 

CHART PLOT

The negative value of mass flow rate simply indicates that mass is flowing out of our domain which gets more negative with gate rise as expected. From the graph it can be seen that mass flow increases rather slowly than flow factor & flow coefficient which show their exponential nature.

Hence much larger flow coeficient & flow factor ecah time there is an increment in mass flow rate.