Force / Thrust from Compressed Air Container 90ci/4500psi

[Curious007]

Hello All, I was wondering that what is the force/thrust we can get from 90ci/4500psi compressed air container, which are available in market for Air guns. Also how long that force will last continuously (2 min or 5 min or more) ?

For more info about the container : http://www.paintball-online.com/Nin...Carbon-Fiber-HPA-Tank-System-TKNJ4590-0X.aspx

Thank you.

 

[mfb]

It depends on your setup. The total energy is limited, total force is not - and if that force does not lead to a displacement, you can maintain that force as long as you like (neglecting leaks and so on).
If you have some specific application in mind, please post this.

 

[Curious007]

Thanks for your response MFB. I want to use it as shown in this diagram :

http://stevenmshort.com/wp-content/uploads/2008/01/bike2.JPG

What do you think about it?

 

[mfb]

Hmm, I don't know how efficient that setup will be.

As an upper limit (!) on the work you can get: Let x be the ratio of pressure in your container relative to the atmospheric pressure, which is ~310 according to WolframAlpha. ci is cubic inch? 90inch^3 = 1475cm^3.
If you expand a volume of V with pressure p to a volume x*V of pressure 10<sup>5[/su] Pa (=atmospheric pressure), you get a maximum of 565*p*V as work (with adiabatic expansion of dry air).

This gives ~26MJ - more than I expected, as it has about half the energy density of petrol.
If you want to replace a human (with ~200W power), you can use this for 36 hours. Note that the value is an upper limit - but if the efficiency is reasonable, you might get a nice tour with that device.</sup>

 

[Curious007]

Thank you very much for your explanation MFB.

I'm also curious to know what force would it exert continuously for 36 hours? I mean did you consider the nozzle size of some diameter to come to that conclusion?

Or other way, if I want 1000N of force from that setup continuously, how long it will last and how big the nozzle should be?

PS : I didn't know about WolframAlpha, I used to think Google calculator is the only option till date.

 

[mfb]

I think you mean Power and not Force. They are related via the velocity, but they are not the same. You can divide the energy (26MJ) by the time to get power - with 36 hours, this gives the 200 W I assumed for a human.
With 5m/s (18km/h, or ~11-12 miles per hour (guessed)), 200W corresponds to a force of 40N in forward direction. Probably more than the bike needs at that velocity.

The force at the piston is different, but that depends on the specific setup. The (maximal) energy does not, therefore I used energy and not forces.

 

[Curious007]

Ok.
For time being let's consider that there is no piston and no bicycle. My aim is to get 1000N force from the nozzle itself (I'm also curios to know what would be velocity of the air coming out). Let's forget what we would drive by that force.
So can we get 1000N from the nozzle? If not how much we can get and for how long? And what would be the velocity of that air?
I hope I'm not asking too much here, but I apologize as I'm not Mechanical engineer. However I think, I imagine better than a Mechanical engineer, and the reason for that is I'm not Mechanical engineer :)

 

[mfb]

As I said before, your question is not well-defined.

Force can be calculated as (pressure difference)*area. With a piston (or nozzle diameter or whatever) of appropriate area, you get a force of 1000N. If nothing moves, you can have this force forever. With a larger area, you can get any force you want, forever. If you want to drive something based on that force, you get a (non-zero) power, and that cannot be sustained forever.

 

[Curious007]

Well I meant to say that if we are releasing the air from the nozzle continuously in the environment, at some point all air will be gone from the container. So I wanted to know how much would be the duration till we can get continuous air flow, considering we are getting/drawing 1000N force. I mean do we have any formula to calculate that duration?

I hope I'm more clear in what I want to know now?

 

[mfb]

Repeating your question will not help - this is is simply not well-defined.
It is like a question "how long can a table stand on the ground with 1l of water?". How would you answer this?

 

[Curious007]

I think I didn't formulate my question properly. Let me try it other way for analogy.
Let's say, I have 5 gallon water filled tank with tap attached, which is kept on table. If I open the tap, water starts flowing out of the tank and falls on the floor. It would take 2-3 min till the tank becomes empty, depending on the Tap opening size and pressure of water at that particular moment.

Similarly is there any way I can find out how long the Air tank will supply 1000 N force? Or something approximation?

 

[mfb]

Let's say, I have 5 gallon water filled tank with tap attached, which is kept on table. If I open the tap, water starts flowing out of the tank and falls on the floor. It would take 2-3 min till the tank becomes empty, depending on the Tap opening size and pressure of water at that particular moment.

And there is no force you want to have in some way.

 

[Curious007]

I can use the force of falling water and generate electricity with that at very low scale. But that's not point :)

Point is How long It will take for air to come out of tank if the Tap size was 10 mm on the tank (I understand gradually the air force or pressure will keep on reducing, so I won't be able to get constant 1000N out of it.) ?

 

[mfb]

A hole with a diameter of 10mm, without further valves or similar? It would lose pressure in a matter of seconds, propelling itself in the opposite direction like a rocket.
And I still don't know how/where you want to measure a force.

 

[Curious007]

Ok, Here are more details.
The Air Can is tied/fixed to ground/Can't move. It can output 800psi using regulator/valve. So based on 800psi valve, how long it will last? [They also say the output can be adjusted/varied in between 400-800]

(Some more info about the Air Tank :
A Ninja Paintball 90 ci 4500 psi Carbon Fiber HPA Tank is the top choice of pro paintball teams the world over. Its also incredibly popular for scenario games where lots of cover fire is needed. Ninja Paintball regulators are built to some of the tightest tolerances in the industry, providing consistent output and reliable long lasting performance. Their customer service is also second to none!
The Ninja Paintball 90 ci 4500 psi Carbon Fiber HPA Tank features a high output (800-850 psi) to work with the majority of paintball markers on the planet. Their Mini Fill Valve is small and compact to clear most marker gripframes and rails. The design is also simple to rebuild and maintain when needed. One of our best selling 90/4500 HPA tanks for a good reason!)

 

[mfb]

Sorry, but I still don't think your questions have a meaningful answer.

The Air Can is tied/fixed to ground/Can't move. It can output 800psi using regulator/valve. So based on 800psi valve, how long it will last?

Depends on the valve.

 

[Curious007]

Hmmm, that's sad part. I thought we might have some kind of formulae to get the answer. I might have to empty the tank by purchasing it and see how long it will last and at what pressure against time.

 

[mfb]

There are formulas to get an answer, as soon as your question includes all relevant data.
This does not mean that the answer has to be easy to calculate - an experiment might be easier to do if the setup is complicated.

 

[Curious007]

Ok. Let me try again now. Please let me know if you want more info :)
90ci / 4500psi container has valve of 800psi. If valve is opened in it's full capacity, how much force we can get out of it and for how long at the valve opening? Please assume all ideal conditions and container fixed / non-movable.

 

[mfb]

An arbitrary force, for an arbitrary time. That is just the wrong question.

You can ask for energy, or power*time, or force*velocity*time, or something similar. This has a meaningful value.

 

[Curious007]

Hmmm, Ok, so can I have whatever meaningful we can calculate out of this?
Sorry again this is like me shooting in the dark and hoping it will hit target.

 

[mfb]

You can find the energy somewhere on page 1. As an example, you can use an energy of 1000 J to have a power of 100 W over 10 seconds (as 100W*10s=1000J), or 10 W over 100 seconds.

 

[Curious007]

Ok, great. I'll try to do some experiments with it. In case I get something out of it, I'll update you. Thank you very much for your help :)

 

[Curious007]

I found range of air motors (on www.atlascopco.com) which consumes 8 l/s to 30 l/s and gives output from 0.3 Hp to 300 hp. If we regulate the air with 90 psi at the rate of 10 l/s, I believe we would get less than 30.6 seconds to make it empty.