# How bad do we need a pressurized fuel tank?

1. Dec 15, 2009

### dE_logics

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.

2. Dec 15, 2009

### xxChrisxx

I don't get it.

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

3. Dec 15, 2009

### dE_logics

: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.

4. Dec 15, 2009

### xxChrisxx

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.

5. Dec 15, 2009

### dE_logics

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.

6. Dec 15, 2009

### xxChrisxx

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.

7. Dec 15, 2009

### dE_logics

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.

8. Dec 15, 2009

### Topher925

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.

9. Dec 15, 2009

### xxChrisxx

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?

10. Dec 15, 2009

### dE_logics

Sorry...I got only half the message last time...some sorta bug.

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.

11. Dec 15, 2009

### dE_logics

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.

12. Dec 15, 2009

### xxChrisxx

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.

13. Dec 15, 2009

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 $$. 14. Dec 15, 2009 ### dE_logics 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. 15. Dec 15, 2009 ### dE_logics What about CNG tanks...their pressure drops with the amount of fuel left, with this you can maintain a constant pressure. 16. Dec 15, 2009 ### dr dodge 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 Last edited: Dec 15, 2009 17. Dec 15, 2009 ### dE_logics Ok...thanks. 18. Dec 15, 2009 ### chayced 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. 19. Dec 15, 2009 ### Cyrus ...................? Why does it have to be pressurized with air? Even if it does have air, it will only ignite if the stoichiometric ratio is right. 20. Dec 16, 2009 ### dr dodge they already are pressurized thats why every 2-3 years your car needs a new gas cap to pass inspection and they don't blow up that much now, and theres plenty of O@ in there already dr 21. Dec 16, 2009 ### xxChrisxx IT doesn't matter what its pressuried with, the air is in the atmosphere. If your fuel tank explodes for some reason (admittedly an event that would never happen) the fuel would vapourise and mix with the air, then explode. My main conern was that in the event of a crash and failure of the tank, a standard pressure fuel tank would just leak out. A high pressure tank would actively eject it's contents onto the surroundings (especially with a system that tried to maintain its pressure) you'd have a fuel fountain. It's more of a fire risk than a bomb risk. 22. Dec 16, 2009 ### dr dodge if it was pressurized with fluid, as opposed to gas, then the forced ejection of fuel would be minimized. add a rubber bladder that the fuel resides in, and is pressurized from the outside of the bladder, and risk becomes minimal, if not safer than the current single layer tin can we currently use dr 23. Dec 16, 2009 ### xxChrisxx That's what i'd do to minimize risk. Only problem then is one of economics. Bladder + pressure vessel is way more expensive than a pump. You'd also need a locking fuel rig with valves, unless it's purged then repressuried after delivery. Edit: just thinking every fuel line would have to be a high pressure fuel line. Last edited: Dec 16, 2009 24. Dec 16, 2009 ### dr dodge I really can not see any significant advantage in the pressurized system. early race cars and aircraft had manual pumps to pressurize the tanks, and we can see where that went. as you said, the costs of the tubing alone would drive the$$\$ up significantly and high pressure tubing is also a bear to bend artisticly vs thin wall tubing. AN fittings and braided flex tubing would also probably be needed.

dr

25. Dec 16, 2009

### dE_logics

The whole pressurized arrangement is extremely cheep and sorta simple (sorta).

To fill the tank you can release the pressure using manual force or a small motor (the smaller the motor the more time will take).

Point is we have definite advantage with gaseous fuels right?