How to calculate the pressure on a piston in a damper system?

In summary, the conversation discusses the calculation of pressures exerted back on a piston in a damper system using equations and data for flow rates through an orifice. The equation for the orifice flow is mentioned along with a correction for the equation used to calculate the pressure on top of the piston. Additionally, the conversation touches on the importance of accounting for the rod area and the type of orifice when calculating the pressure.
  • #1
LogNels
2
0
Hello all,

I'm trying to calculate the pressures exerted back on a piston by a working hydraulic fluid in a damper system. I've attached a drawing of the system and the equations I'm using. Essentially the piston motion is restricted by flow through an orifice. I have data for the flow rates through the orifice and I need to calculate the pressures the piston sees based on that data. My solution is giving me unreasonable results. Am I missing something?

Best Regards,
Logan
 

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  • #2
Your equation for the orifice flow ΔP is correct. Just as a note, if your system fluid is hydraulic oil, then I would expect the fluid expansion factor to be "1".

At the same time, your figure indicates that the orifice discharge fluid pressure is being directly applied to the rod side of the piston where the effective pressure area is the (the piston area - the piston rod area); if that is the case, then:

P piston = (F rod – Dp x (A piston – A rod)) / A piston

As a result, the pressure on the top of the piston will be primarily dependent upon the external load on the piston rod.
 
  • #3
Since the editing time for my prior last post has expired, this post is to correct an error in the equation presented in that post.

"P piston = (F rod – Dp x (A piston – A rod)) / A piston" should be:

P piston = P1 = (F rod + P2 x (A piston – A rod)) / A piston
 
  • #4
Hey JBA,

You brought a good point about accounting for the rod area. I realized my biggest problem was that I was oversimplifying the system model.

Thank you for your help!
 
  • #5
The pressure can be derived from the orifice flow equation -
Q = A x Cd x (sqrt (2 x Delta P/Density))

P = (0.5 x Density^2) / (Area x Orifice coefficient)

SI Units being used

Q - M^3/sec
P - Pascals
Density - kg/m^3
Area - m^2
Orifice coefficient being dependent on the type of orifice
 

1. How do you calculate the pressure on a piston in a damper system?

The pressure on a piston in a damper system can be calculated by dividing the force applied to the piston by the area of the piston. This can be represented by the equation P = F/A, where P is the pressure, F is the force, and A is the area of the piston.

2. What units are used to measure pressure in a damper system?

The most common units used to measure pressure in a damper system are pounds per square inch (psi) or newtons per square meter (N/m2). Other units such as bars, atmospheres, and pascals can also be used.

3. How can I determine the force applied to a piston in a damper system?

The force applied to a piston in a damper system can be determined by multiplying the pressure by the area of the piston. This can be represented by the equation F = PA, where F is the force, P is the pressure, and A is the area of the piston.

4. What factors can affect the pressure on a piston in a damper system?

The pressure on a piston in a damper system can be affected by various factors such as the weight of the object being supported, the velocity of the piston, the viscosity of the fluid in the damper, and the size and design of the damper system.

5. Can the pressure on a piston in a damper system be negative?

Yes, the pressure on a piston in a damper system can be negative. This can occur when the force acting on the piston is in the opposite direction of the piston's movement, causing it to compress rather than expand. Negative pressure can also occur when the fluid in the damper is flowing in the opposite direction of the piston's movement.

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