pulse jet fuel

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pulse jet fuel

Postby cokeman225 » Sun Apr 03, 2011 4:19 pm

first can someone tell me if you vaporize gasoline and use it instead of propane will it work? if its does will you get more thurst. second And I know this might be stupid but at the temp a pulse jet works while its running if you vaporize water and inject it in might it work like nos in a car the temp spliting the H and th O2 into gas from and fuel?
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Re: pulse jet fuel

Postby HPSCL » Sun Apr 03, 2011 5:47 pm

cokeman225 wrote:first can someone tell me if you vaporize gasoline and use it instead of propane will it work? if its does will you get more thurst. second And I know this might be stupid but at the temp a pulse jet works while its running if you vaporize water and inject it in might it work like nos in a car the temp spliting the H and th O2 into gas from and fuel?


The temperature required to separate the hydrogen and oxygen from water is approximately 5,000°F... Carbon Steel melts at 2600-2800°F, while Stainless Steel melts at 2750°F.

Water injection is used as a method for cooling combustion chambers of engines;

in a piston engine, the initial injection of water cools the fuel-air mixture significantly, which increases its density and hence the amount of mixture that enters the cylinder. An additional effect comes later during combustion when the water absorbs large amounts of heat as it vaporizes, reducing peak temperature and resultant NOx formation, and reducing the amount of heat energy absorbed into the cylinder walls. This also converts part of combustion energy from the form of heat to the form of pressure. As the water droplets vaporize by absorbing heat, it turns to high pressure steam (water vapor or steam mainly resulted from combustion chemical reaction), that would add engine output. The alcohol in the mixture burns, but is also much more resistant to detonation than gasoline. The net result is a higher octane charge that will support very high compression ratios or significant forced induction pressures before onset of detonation.
Reference: Water injection (engines)

I would guess that the use of a liquid fuel (as opposed to a gaseous fuel), would have the same benefit of the increased density and therefore a greater amount of fuel could enter the pulsejet engine?
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Re: pulse jet fuel

Postby Kool » Sun Apr 03, 2011 10:06 pm

maybe interesting to read for you:

viewtopic.php?f=2&t=4628&st=0&sk=t&sd=a&start=15
...It's better to generate heat efficiently, than recover it efficiently...
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Re: pulse jet fuel

Postby cokeman225 » Mon Apr 04, 2011 11:27 pm

ok putting aside the water part( what i get from your replys is it might be possible just not in a pulse jet because it does not get hot enought but even with a engin that runs at 5000 + the it would use up to much water to be useful?)
about the gasoline i think i worded the Q wrong there is a company compeating for the car X prize that turned gasolin into a vapor before injecting it into the combustion chamber turning a 25 mpg car into a 96 mpg car. They stated that in liquid form we don't use all of the gasolines potental. thats what i meant by vaporizng the gasoline before useing it in a pulse jet. any ideas?
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Re: pulse jet fuel

Postby ea7778 » Sun Aug 28, 2011 8:16 pm

what you wanna do is utilize electrolysis of water, which breaks it into hydrogen and oxygen, Alone this wont help and is wasteful BUT if you inject the gases into your fuel stream then it boosts the burn efficiency
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Re: pulse jet fuel

Postby tufty » Mon Aug 29, 2011 6:44 am

cokeman225 wrote:They stated that in liquid form we don't use all of the gasolines potental. thats what i meant by vaporizng the gasoline before useing it in a pulse jet. any ideas?

In the general case, combustion efficiency will increase with increased air and better mixing (and, for a liquid fuel, potentially by better atomisation). Vapourising would be good too, I guess, but you'd have to do it in such a way that your fuel feed doesn't get coked up or "inverse bubbles" in it. The usual way of vapourising, by running the fuel through a feed line wrapped around the combustion chamber, has a tendency to coke up and clog with liquid fuels.

As for the question of "more thrust", then yes, gasoline will get you more thrust per kg of fuel, as it's more energy dense than propane. Diesel even more so. Propane is a damn sight easier to get going though.

If you want more thrust without worrying too much about the weight or efficiency, augmentors and water injection are your friends. The search function will elucidate.

electrolysis of water ... hydrogen and oxygen ... inject the gases into your fuel stream then it boosts the burn efficiency

No. No it doesn't.
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Re: pulse jet fuel

Postby Jutte » Wed Aug 31, 2011 10:17 pm

"electrolysis of water ... hydrogen and oxygen ... inject the gases into your fuel stream then it boosts the burn efficiency"
Yeah Tufty is right - at the output that electrolysis of water gets you aren't really going to get enough gas - all you'll
be doing is burning the Hydrogen and Oxygen - which is cool but rather boring in a way.
However if you got heaps of Oxygen and Hydrogen - things are really cool and get super exciting
....and I'll be the guy watching you standing a loooooong way off way way over yonder ...:lol:
Apart from that...
"No. No it doesn't."
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Re: pulse jet fuel

Postby Viv » Wed Aug 31, 2011 11:01 pm

cokeman225 wrote:first can someone tell me if you vaporize gasoline and use it instead of propane will it work? if its does will you get more thurst. second And I know this might be stupid but at the temp a pulse jet works while its running if you vaporize water and inject it in might it work like nos in a car the temp spliting the H and th O2 into gas from and fuel?


Hi Cokeman

Yes you can vaporize gasoline but the advantages are not that many for the added complication when you are only running an engine static, if your after thrust bragging rights then yes but otherwise I would recommend you stick to propane gas for its simplicity and ease of use (and the huge safety factor compared to petrol ;-)

The temperature in a pulse jet combustor varies across the combustion cycle, for part of the cycle the engine is ingesting cool air and fuel, due to this fact peak temperatures are much to low to split water in to its components as others have detailed for you.

Viv
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