Parametric study of a Gate Valve

Objective:

To run a parametric study of a gate valve in a pipe. We will be studying five different opening conditions of the gate valve and the corresponding mass flow rates at the outlet of the pipe.

Introduction:

A gate valve is generally used to completely shut off fluid flow or, in the fully open position, provide full flow in a pipeline. Thus it is used either in the fully closed or fully open positions. Gate valves are not normally used to regulate flow is because the flow rate of the fluid is not proportional to the amount that the valve is open. Moreover, a partially open gate valve may suffer from vibration in which the valve may move from its assigned position. Also the gate and seat may be subject to excessive wear if the valve is partially open.

A gate valve consists of a valve body, seat and disc, a spindle, gland, and a wheel for operating the valve. The seat and the gate together perform the function of shutting off the flow of fluid.

Gate valves are used in many industrial applications including the oil and gas industry, pharmaceuticals, manufacturing, automotive, and marine.

Geometry:

3d cad model of the gate valve assembly

Cross sectional view of the gate valve assembly

The fluid volume needs to be extracted to perform a CFD calculation. Both the inlets and outlets of the pipe are extended to allow for the flow to develop to satisfy mass conservation.

Mesh:

A baseline computational mesh was generated with an element size of 10mm. The total cell count was 192893 cells.

Solver input and boundary conditions:

• The case was solved as steady state with gravity enabled.
• The k-e turbulence model with standard wall functions was chosen.
• An inlet pressure of 10 Pa was assigned along a pressure outlet condition at the outlet boundary.
• The domain was initialised using standard iniatilization from the inlet.
• A report plot was defined at the outlet to study the mass flow rates.

Results:

1. Obtain mass flow rates for all design points

Design point	Gate valve lift condition (mm)	Mass flow rate (kg/s)
1	0	-0.14
2	10	-0.22
3	30	-0.44
4	50	-0.62
5	60	-0.70

The gate valve is simulated from an initial condition where the gate disc is completed closed and consquent values simulating the opening of the gate were calculated. From the above table we can see how the mass flow rates at the outlet of the pipe increase with raising of the gate disc proportionally. The -ve sign indicates the mass flowing out of the boundary.

2. Cut planes to visualize the flow through the pipe at different gate opening conditions

Velocity contours are displayed across a cross sectional cut planes to give an indication of the fluid flow also the lift of the disc also can be seen.

3. Contour animations for the design points

The above video aids in showing a better visual representation of the changes in water velocity with the corresponding lift points of the disc.