Hydraulic restrictors 2

[Michiel1984]

How do I have to calculate the pressure drop over a restrictor? If I calculate it with the formula stated below, the pressure drop will be huge!!!

Q=Cf*A*SQRT((2*differential pressure)/Density)

A=0.7 mm^2
Q=1.66 GPM
Density=0.997 g/ml

The units have to be calculated in cubic meters and liters (liters/second). The Cf is mostly in between 0.6 and 0.9, but I don't know what the right value of it is. If somebody does know how I can determine the value of it, it would be really great!

Thank you in advance

Ps: the system pressure is 3000 PSI (20,7 MPa)

 

[israelkk]

If you can't give at least the following data:
1. The landing gear geometry
2. a model of the aerodynamic loads (worst case, typical, and optimal case etc.)
3. The inernal resistance of the landing gear such as friction etc.

How are you expect to select the desired restrictor?

The calculations are not so complicated, all you need is to combine the hydraulic model with the dynamic model of the landing gear deployment which will result in a set of differential equation which can quite easily be numerically solved for the set of conditions.

I have done and still doing such analysis from time to time for pneumatic, electric and spring actuated systems using Mathcad Octave/Matlab.

 

[Michiel1984]

The only thing that I know is the landing gear geometry. I also don't have access to Matlab or the other programs. The calculations are indeed not so complicated, but if you have very less information, they become difficult. I made an approximation of the landing gear extension/retraction times. I also thought the following:

Flow is reduced from 6,5 gal to 1,5 (Factor 4.3333)
This means the actuating time is increased wiht 4.3333. I don't think this is right because of the non-lineair components in the system. But it is a good approximation I think (if the factor not becomes to high)

However, I think such analysis are real fun to find out.