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-   -   How bad do we need a pressurized fuel tank? (http://www.physicsforums.com/showthread.php?t=363492)

dE_logics Dec15-09 02:41 AM

How bad do we need a pressurized fuel tank?
 
Imagine a fuel tank that can store fuel at pressure (it can store at pretty high pressure also) without having any component which provides it constant energy e.g. a pump (i.e energy has been previously fed into the system so as to maintain the pressure in the tank regardless of it's fuel quantity).

This can be also be used in fuel stations and aircrafts.


So, what will be the advantage of this?


I think it will make a sort of super/turbo charger.

xxChrisxx Dec15-09 06:16 AM

Re: How bad do we need a pressurized fuel tank?
 
I don't get it.

How are you going to get higher pressures without some sort of pump?

dE_logics Dec15-09 07:36 AM

Re: How bad do we need a pressurized fuel tank?
 
:D :D...it is somehow possible (maybe I'll post 'how' later)...the fuel has been maintained at high pressure and the pressure is not a function of the amount of fuel left...it's very cheep and reliable.


I just wanna know what will be the advantages.

xxChrisxx Dec15-09 07:52 AM

Re: How bad do we need a pressurized fuel tank?
 
Well... I really can't think of any.

I don't know why on earth you'd want to pressurise a full fuel tank on a car.

I must be thinking/imagining something different to you, as what's in my head just doesnt make any sense to do.

dE_logics Dec15-09 10:23 AM

Re: How bad do we need a pressurized fuel tank?
 
I was wondering about increasing the power delivery per stroke.


Like a super/turbo charger...instead of forcing the fuel/air mixture in, it will force the fuel.

xxChrisxx Dec15-09 10:27 AM

Re: How bad do we need a pressurized fuel tank?
 
Turbochargers work by having more AIR in the cylinder, so as a result you have more fuel and therefore more power. Just adding fuel under pressure will not add power, just make you run rich.

For that you don't need an entire fuel tank underpressue. In cars fuel is pumped from a low pressure tank into higher pressure injectors.

Typical out of cylinder injectors run at something like 4 bar, and use the heat of the valves to help atomise the fuels. Newer direct injection engines, use high pressure rail injectors running cloer to 150-200 bar. Common rail direct injection diesels can run at nearly 2000bar.

Higher pressures, allows smaller nozzles to be used for the same flow rates, meaning more atomised fuels, but agian only a very small amount of fuel needs to be at high pressure at any one time.

dE_logics Dec15-09 10:32 AM

Re: How bad do we need a pressurized fuel tank?
 
Ok...I know what you mean...there's an ideal fuel air mixture after which there's no use of adding more fuel to the mixture.

Topher925 Dec15-09 10:33 AM

Re: How bad do we need a pressurized fuel tank?
 
Quote:

Quote by xxChrisxx (Post 2492876)
Newer direct injection engines, use high pressure rail injectors running cloer to 150-200 bar. Common rail direct injection diesels can run at nearly 2000bar.

The only thing I can think is that it would allow you to get rid of the high pressure fuel pump(s) but I don't see that being a big advantage. While you are feeding fuel at a very high pressure, is at a very low mass flow rate so it doesn't take that much power away from your BHP.

xxChrisxx Dec15-09 10:33 AM

Re: How bad do we need a pressurized fuel tank?
 
Quote:

Quote by dE_logics (Post 2492881)
That will eliminate any pumps which were previously there to do the same job...that's what I'm talking about.

I don't know about you, but I don't fancy sitting on 15 gallons of petrol pressuried to 200bar. You only need a tiny amount of high pressure fuel at any one time.


It was an interesting idea though, eliminating moving components is always a good thing, how did you plan to keep it pressurised without a pump?

dE_logics Dec15-09 10:41 AM

Re: How bad do we need a pressurized fuel tank?
 
Sorry...I got only half the message last time...some sorta bug.

Quote:

Higher pressures, allows smaller nozzles to be used for the same flow rates, meaning more atomised fuels, but agian only a very small amount of fuel needs to be at high pressure at any one time.
What I mean is that the whole fuel in the tank is at pressure...so you wont require the pump...that's the only advantage.


What about bikes and small generators (by small I mean not those colossal ones which are large enough to make you think of fitting a small pump in it)?...it will provide fuel under pressure without any pump.

dE_logics Dec15-09 10:44 AM

Re: How bad do we need a pressurized fuel tank?
 
I will post the whole thing later (I'm making the formal docs)...not only it is applicable for fuel tanks...but many other applications; providing pressure in a cheep and reliable way.

Constant pressure i.e without the pressure being a function of the fluid left in the tank.

It has moving parts...but it's negligible...point is you won't have to worry about it's life.

xxChrisxx Dec15-09 10:46 AM

Re: How bad do we need a pressurized fuel tank?
 
Quote:

Quote by dE_logics (Post 2492897)
What about bikes and small generators (by small I mean not those colossal ones which are large enough to make you think of fitting a small pump in it)?...it will provide fuel under pressure without any pump.

You'd have an advantage in very very small things, that would either require tiny pumps.

Or it could replace things with a gravity feed, they don't use pumps but require an awkwardly placed fuel tank, so a lawn mower or something.

FredGarvin Dec15-09 10:49 AM

Re: How bad do we need a pressurized fuel tank?
 
We used pressurized fuel tanks in many of our applications already. The trouble is, Chris is right. Pressure just doesn't happen. We have to use some part of the engine to provide some source for that pressure. Of course, by doing so, there are tradeoffs like having more regulation and flow control equipment. Also you now have a pressure vessel and not just a tank. That all equates to more $$$.

dE_logics Dec15-09 10:56 AM

Re: How bad do we need a pressurized fuel tank?
 
Quote:

Quote by xxChrisxx (Post 2492908)
You'd have an advantage in very very small things, that would either require tiny pumps.

Or it could replace things with a gravity feed, they don't use pumps but require an awkwardly placed fuel tank, so a lawn mower or something.

Yeah, the thing is made primary to reduce the height...or it can give pressure without any height elevation.

Thanks for the answers...I got an ideal now.

dE_logics Dec15-09 11:06 AM

Re: How bad do we need a pressurized fuel tank?
 
What about CNG tanks...their pressure drops with the amount of fuel left, with this you can maintain a constant pressure.

dr dodge Dec15-09 12:15 PM

Re: How bad do we need a pressurized fuel tank?
 
there is a big advantage. the increase in static pressure would raise the fuell above its vapor pressure. That (in theory) would decrease evaporation in the tank, and help the fuell be more meterable due to a consistant density. Down side is it should increase the temp of the fuel at the time of pressurization. In IC lawn instruments it would also stop condensation of ambient water vapor in a normally vented tank. The pressure "release" at the injector could also possibly have better atomization.

dr

dE_logics Dec15-09 11:11 PM

Re: How bad do we need a pressurized fuel tank?
 
Ok...thanks.

chayced Dec15-09 11:12 PM

Re: How bad do we need a pressurized fuel tank?
 
I agree with Chris. A pressurized fuel tank regardless of where the pressure came from is a bomb. Look up "Fuel Air Bomb" if you doubt me. That's why we have a pump.


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