Fluid power has the highest power density of all conventional power-transmission technologies. Learn the benefits and limitations of fluid power, how to analyze fluid power components and circuits, and how to design and simulate fluid power circuits for applications.
What is fluid power?
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来自 University of Minnesota 的课程
流体动力学基本原理
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从本节课中
Week 1: Fundamentals of Fluid Power
This week: An overview of the course, introduction to hydraulics and pneumatics, and introduction to fundamental concepts of fluid power through the cylinder.
与讲师见面
James D. Van De Ven, PhDAssistant Professor
Mechanical Engineering
Will Durfee, PhDMorse Alumni Distinguished Teaching Professor
Mechanical Engineering
So since you're taking a class on fluid
power, let's start with a definition of fluid power.
So fluid power is the use of a
confined, pressurized fluid to transmit force or motion.
What we want to stress here is that we're transmitting
force to the fluid, it's transmitting the power for us.
So if we look at three possible applications.
And we start to say are these fluid power?
Are they not?
Well, the dental tool, this will be an example
of fluid power because we're using compressed air in
this case to transmit power to the drill head
where you can do work on the, on a tooth.
But these other two applications, if we look at a parts
washer or a house type of a washing application like this.
A pressure washer.
This would not be an example of fluid power because we
are pressurizing the fluid, but we're not using it to transmit power.
Instead, we're just using that pressurized fluid to wash the building.
Or an example of an engine, if we look at the, the pump that is pumping oil in
an engine, this would also not be an example
of fluid power because that is just providing lubrication.
So, we're stressing here that this is fluid
power transmitting power and not necessarily fluid conveyance.
>> Is fluid power important?
Yes, it is.
This is a chart from the US
Energy Information Administration, where on the left it's
all the sources of energy, and on the right is where all the energy goes.
There's been estimates that over 100 quads, which is a quadrillion BTU
of energy flows through this chart each year in the United States.
Of that, two to three quads are used to drive fluid power machines.
So, that's a significant amount of the energy used
in the United States that is transmitted by fluid power.
Now, that fluid power on the other hand is only about 21% efficient.
What that means is that if you improve the efficiency of fluid
power by just 5%, you could save about $8 billion a year.
Fluid power is everywhere.
Let's show you a few examples.
Here's a bottle jack which you might use to pick
up a joist to raise the corner of your house.
>> Another example is a log splitter where you need to split a
log and you don't want to use a lot of effort to do so.
You can take the power from a gasoline engine,
use that to drive the hydraulics and split the log.
>> Here's a third example which is a commercial mowing machine where
hydraulics are used to do the steering and to drive the wheels.
>> Another example is a backhoe loader.
You often see these at construction sites where the
hydraulics are powering multiple circuits on this vehicle for
both the backhoe, and also the front end loader
that's being used to, to move rubble and debris.
>> This machine is used at MTS Corporation.
Which has hydraulic cylinders under each of the four wheels of the car
in order to move the car and shake the car to do vehicle testing.
>> Another example is a braking system.
This one happens to be on a bicycle where hydraulics are used to transmit the
force from the lever that the user's
operating to the disk brake of the vehicle.
>> And here's a thrill ride at Valley Fair Amusement Park
that uses fluid power to shoot riders up in the air.
We'll be taking a look at this one in more detail later on in the course.
>> So why do you want to use fluid power?
Well, there's a couple of reasons as you compare it to other power technologies.
The first one is just the very high force density and high
power density, a lot of force or power in a very small package.
So this allows you to do some very interesting things with how
you're going to package the vehicle, or whatever the application might be.
Another is very high bandwidth.
Because fluid power systems can move at very high speeds, we can
produce, produce a lot of flow and therefore move things at high velocities.
We have very precise control because oil is relatively incompressible
and so, high force and precise control at the same time.
And then we also have the flexibility in our
power transmission to move the fluid through various conveyance systems.
So we can have flexible hosing that might take the fluid from an
engine in a pump, out to the, the end of an excavator arm.
>> Here's an excavator, a large construction
machine that's digging a hole for the light
rail line that is opened up at the
University of Minnesota in the summer of 2014.
It uses hydraulics to move the bucket, and one of the things that when you are
digging through dirt is that you need a
tremendous amount of force to move through the dirt.
So that cylinder that's up at the top,
that hydraulic cylinder which is about five inches in
diameter, and runs at about 5,000 pounds per
square inch, can produce about 275,000 pounds of force.
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