How to model a piston with a retracting spring at one end and having single hydraulic port??

The spring is to exert some force on the fluid inside the cyinder, thus pressurizing it. I want to find out the response rate (outlet flowrate) of the fluid when pushed out by the spring with different stiffness rates? Can anyone help? How to model this block in SimHydraulics?

Answer 1

[Animesh]

Hi @immanuelkeba,

To model a spring-pressurized hydraulic cylinder in SimHydraulics and analyze the outlet flow rate for different spring stiffness values, you can follow these steps:

1. Use the "Double-Acting Hydraulic Cylinder" block to represent the cylinder.
2. Add a "Translational Spring" block to simulate the spring applying force to the piston. Connect this block to the mechanical translational port of the hydraulic cylinder.
3. Include a "Hydraulic Fluid" block to define the properties of the fluid in the system.
4. Use a "Fixed Orifice" block to model the outlet through which the fluid exits.
5. Place a "Flow Rate Sensor" in the outlet line to monitor the flow rate of the fluid being expelled from the cylinder.

Once the setup is complete, you can run simulations with different spring stiffness values to observe how the outlet flow rate changes.

Additionally, you might find this video tutorial helpful for a practical demonstration of modeling a hydraulic actuation system:

https://www.youtube.com/watch?v=9LUuI9EIuAM

[immanuelkeba]

Hi Animesh,

Thanks for your answer. Tried doing your inputs with some additional blocks. I am getting some errors on it. Could please check and let me know where have I gone wrong?

Thanks

Immanuel Keba

Answer 2

[Yifeng Tang]

Something like this should work.

It's important to pay attention to a few things when setting up this model:

(1) area of the orifice will have a great impact on the outlet flowrate. You'll need some reference information to know an appropriate size.

(2) the spring needs to have an initial deformation.

(3) the initial pressure of the cylinder needs to match the initial spring force. calculate based on k*x/A.

(4) the initial position of the piston should not be zero, otherwise the cylinder has no fluid inside to push out.