So, if I maybe have a 2 millimeter orifice
that fluid is moving through, and I reduce that
down to a 1 millimeter orifice, well now I
have a 16 times increase in my pressure drop.
So we have to be very careful as we start
to change areas, as to what the pressure drop relationship is.
It's not linear, it's actually to the fourth power, so very substantial.
So you might say, how do you, how do you change the, the area?
Well, one of our most common valves that we use, is called a needle valve.
And I've got a diagram of it here.
Basically what's happening is I am turning this knob here, and it
is taking a, a conical shape, or a needle if you will.
And pulling it out of a seat or bringing it down into the seat.
What I'm doing is I'm changing the cross-sectional
area, so if you can imagine this is
the part down here that's actually restricting the
area, and the flow path is right through here.
So, I'm restricting that flow path as I turn this knob.
This is one of the common, simple ways to change the area
or the pressure drop flow rate relationship in a, in a hydraulic circuit.
So, now let's look at this in an application.
So, let's say I've got a valve here and I'm going to
pick a valve that, that is just an on/off valve, if you will.
It's got two, two ways, is what we call it.
It's got an input flow and an output flow.
I have a, a manifold block and so this is what would house the valve,
I've got it cut in half, so you can see it a little bit better.
And this valve with thread in here, and inside of this valve I've got
a cylinoid spool, I'll show you a better picture of it in just a moment.
And when I apply a magnetic field with a, a cylinoid, I then pull this
spool and the movement of the spool will either, open a port or block a port.
And provides the valving operation.
So, I've got a, a very simple circuit here, or I've got my hydraulic pump.
I then have this on off valve that I'm discussing that
I'm showing right here, and then I have a hydraulic cylinder.
So, recognize that this is not a very useful circuit because, we can only drive
the cylinder an extension and we can never return it to a retraction state, but it.
I'm, I'm using to provide an example of this flow rate pressure relationship.
So, I'm saying that I've got a, a flow
rate going across this valve of 25 liters per minute.
So, let me figure out what the pressure's drop, drop is going to be.
And again this is a valve that I can buy off the shelf
and because of that, can go to the data sheet for this valve.