Week 9 - Parametric study on Gate valve.

                                                                                                           PARAMETRIC STUDY ON GATE VALVE

AIM

To perfrom a Parametric Study for a Gate Valve.

Objectives ;

1. To perform the parametric study on the gate valve by simulating the opening of gate valve ranging from 10mm to 80mm.
2. To obtain the mass flow rate for each design point.
3. Calculate the flow factor and flow coefficeint for each design point.

Introduction;

The gate valve is the fluid valve that opens by lifting the barrier gate from the path of the fluid flowing thriugh a pipeline. Gate valves require generally very less space and are and can be fitted along the pipe axis and they hardly restict any fluid flow when they are fully opened.

Gate valves rae generally used to shut off the fluid flow inside a pipe line and also to control the fluid flow. When they are fuly opened they hardly restrict any fluid flow, thus offering very low flow resistance when fully opened. Gate valves are generally used for the pipe of diameters larger that that of 2" to the largest pipes. They are simpler to construct in large sizes. The gate can vibrate if it is in partially open state.

Genewrally in pipelines with high pressure the gate valve opening can be quiet difficult due to the high force exerted on the gate. So trhey are generally connected with a smaller bypass valve to release the pressure and then trhay are operated.

Simulation Methodology;

Modeling ;

The mode for the gate valve can be prepared in any CAD software and thus can be imported in Ansys Space Claim.

The model once imported is checked for any incoming errors such as extra edges and others. Once the errors are repaired the flanges on both the sides of the gate valve are pulled by 800mm to simulate the proper flow while defining the inlet and the outlet for the fluent. It can be seen below

Further the gate disc is moved by 10mm towards the handwheel and the valve is then parameterised by cling the 'P' button and the group is then created. Volume is then extraced using the volume extract command and the volume is updated in context to update the valume as the parameter changes.

Meshing

 The model is then imporeted into the mechanical module for the mesh generation where all the input parameters are kept as default and the mesh size is set as 6mm.

The number of nodes are 87339 and the number of elements are  414055. The mesh can be seen below

The element quality is further checked and it can be noted that all the elements are in the good element quality range.

Setting Up Physics:

First of all the mesh is set up and the solver is defined as below:

Solver Type: Pressure Based Solver

Gravity: -9.81 (in negative z direction)

Solver: Steady State

Model: k-epsilon model (realisable with scalable wall function)

Material: Water

Cell Zone: Fluid(water)

Inlet Boundary Condition : Pressure Inlet (10Pa)

Outlet Boundary Condition: Pressure Outlet

The model will be initialised with standard initialisation and the data will be computed from inlet.

After solving for 250 iterations the results can be seen below:

 Residuals ;

 Mass Flow rate at Outlet;

Velocity Contour ;

Pressure Contour ;

As above we parameterised the gate disc with the different movements we will exit the fluent and will notice that the new option of parameters is activated we will click that and set the new design points upto 80mm gate disc lift height with the increment of 10mm for each consecutive design point and thus we will update all the design points.

The results for the gate disc with 20mm lift can be seen below:

1. Residuals;

 Mass Flow rate at Outlet;

elocity Contour;

Pressure Contour;

 

  The results for the gate disc with 30mm lift can be seen below

Residuals;

Mass Flow rate at Outlet;

 Velocity Contour ;

pressure contour;

 

   The results for the gate disc with 40mm lift can be seen below

Residuals;

Mass flow rate at outlet;

]

velocity contour ;

 

Pressure contour ;

The results for the gate disc with 50mm lift can be seen be

Residuals;

Mass flow rate at out let ;

velocity contour ;

 

Pressure contour ;

The results for the gate disc with 60 mm lift can be seen be

residuals;

 

Mass flow rate at out let ;

Velocity clontour ;

pressure contour ;

The results for the gate disc with 70mm lift can be seen below

Residuals;

mass flow rate at out let ;

velocity contour ;

Pressure contour ;

The results for the gate disc with 80mm lift can be seen below

 Residuals;

mass flow rate at outlet ;

velocity contour ;

pressure contour ;

 

Flow Factor; (Kv)

Flow factor is the flow coefficient in the metric units. It is basically defined as the flow rate in cubic meters per hour for water at the constantr temperature of 16 degree celcius with the pressure drop of 1bar across teh valve.

Flow Coefficient; (Cv)

Cv is the flow coefficient in the imperial units. It is basically defined as the flow rate in US Gallons per minute of water at a constant temperature of 60 degree farenheitand a pressure drop of 1 psi across teh vavle. It is used to determine the flow for various conditions and to select the proper valve for the various applications.

The flow coefficient can be defined as 

k=Q√Sg/ΔP

where,

k= flow coefficient in Kv or Cv

Q= flow rate

Sg = specific gravity (1 for water)

$\Delta P$= Total Pressure Drop

Simply Cv=Kv*1.156

 

The mass flow rate for design points can be seen below

 

Here x axis represents the opening of the gate valve and the y axis represents the value of Kv and Cv.

Here it can be noticed that as the lift heifght increses the pressure drop also decreases and the flow coefficient also increases. Further high flow coefficient offers less frictionoll losses and the high pressure flow through the valve with very low pressure drop. 

 

  Conclusions:

1. The low lift height refers to the higher pressure drop and thus low flow rate through the valve.
2. The negative mass flow is due to the mass exiting the outlet.
3. With the help of the parameters the solving time and effort can be reduced drastically.
4. Flow factor and coefficient increses as the mass flow rate through the valve increases. 

 

gate valve working;

link ; 

https://youtu.be/mInxlZPBilA

result on 10mm left

https://youtu.be/8c3fowoAtMI

result on 20mm left 

https://youtu.be/ICZertpqCp4