Twin Screw Pump, ANSYS Fluent CFD Simulation Training

Description

This simulation is about a twin screw pump via ANSYS Fluent software. We perform this CFD project and investigate it by CFD analysis.

A twin-screw pump is a positive displacement pump, meaning that the pump transfers a particular volume of product according to the speed and pitch of the screws. While turning, the two screws form closed chambers that move in an axial direction.

This movement creates a vacuum at the inlet boundary and positive pressure at the outlet. Due to this double chamber technic, there is an almost pulsation-free working with high and low viscosity products.

In other words, screw pumps operate using two counter-rotating screw rotors engineered to rotate “towards each other.” This traps the gas in the space between the “screws” of their rotors. As the screws rotate, this trapped volume decreases, compressing the fluid and moving it towards the exhaust.

The present problem simulates the pumping of highly viscous fluid (i.e., Glycerin). In this project, the glycerin fluid is sucked inside the computational domain due to the rotation of screws. The twin-screw pump increases the pressure of the Glycerin and pushes it toward the outlet.

The geometry of this project was designed in Solidworks and then edited in ANSYS design modeler and contains two rotating zones and one stationary zone (pump crust).

The model is then meshed by ANSYS Meshing software. The model mesh is unstructured, and 1184161 cells have been created.

Twin Screw Pump Method

In this simulation, the rotational motion of the pump should be defined. Instead of the motion being applied to the pump rotor itself, it is applied to the surrounding fluid. So, a distinct computational zone is created in the cell zone conditions to define the rotational movement.

This work is done using the Mesh Motion method, and the rotational velocity of 3 rad/s is defined.

Also, at the inlet and outlet of the pump, a pressure boundary condition is used because the movement of the fluid inside the pump is not forced, and the fluid transfer occurs according to the pressure changes.

Twin Screw Pump Conclusion

After simulation, 2D and 3D contours of velocity and pressure are obtained. Also, streamlines around the rotors are obtained. The results show that fluid flow is displaced by pressure.

The movement of the rotor causes suction pressure in the pump’s inlet and pushes it towards the outlet of the pump. Also, the flow lines show the rotational movement of the fluid inside the pump.