Best Fuel

Moderator: Mike Everman

Post Reply
spazz11
Posts: 1
Joined: Tue Dec 23, 2008 7:06 pm

Best Fuel

Post by spazz11 » Tue Dec 23, 2008 7:14 pm

what is the best fuel for my pulsejet in flight? (z23 z-jet)

What is easiest to start and gives the most thrust?

If I use petrol what octane should I use (here in Europe)?
Does the addition of liquid paraffin effect the thrust?
Normal lead replacement for old cars, does that do anything?

Is kerosene good? Many turbine pilots fly on a stove fuel, that is similar to purified kerosene. would this work?

kind regards,

Michael

noclassmac1972
Posts: 94
Joined: Sun Jun 05, 2005 5:41 am
Antipspambot question: 0
Location: New Zealand
Contact:

Re: Best Fuel

Post by noclassmac1972 » Thu Dec 25, 2008 10:01 pm

Michael,
When using petrol as a fuel for a pulsejet the best is one with the lowest octane rating possible. The higher the octane the harder they are to start and give less power. Methanol based fuels work well but need a igniter to help them. We currently are running 80% methanol and 20% Nitro methane with great success. The most powerfull liquid fuel to use is 50/50 mix of nitro and propylene oxide.

Hope this helps

Robert Bolton

ps merry xmas everybody

dynajetjerry
Posts: 465
Joined: Thu Jan 27, 2005 4:57 pm
Antipspambot question: 0
Location: Ohio, USA

Re: Best Fuel

Post by dynajetjerry » Sat Dec 27, 2008 4:28 pm

Michael,
The only fuel used by the people who developed the Minijet and Dyna-Jet was automotive gasoline. At that time, of course, it was all leaded, now known to be toxic to animal life. Later users found methanol-based fuels to work very well, especially when blended with other compounds (note Robert's suggestions.) However, gasoline is the most efficient of p-j fuels, even though it is also much less forgiving when not at its optimum mix (about 16:1 air:fuel by weight.) Pariffins can have widely-varying octane ratings and may be less useful in p-js than other hydrocarbons but, as Robert said, octane ratings (an index of ignition temperatures,) are unimportant in p-js. More important is ease of vaporization (vapor pressure,) because of the relatively crude carburetion systems in most model engines. 80/20 methanol/propylene oxide is the fuel of choice in p-j aeromodeling because of its relative non-toxicity, excellent power, combustibility at much wider fuel/air ratios than hydrocarbons, and slightly lower combustion temperatures. 80/20 is the ONLY fuel permitted in AMA p-j competition.
Good luck.
Jerry
Louder is always better.

RiverPhil
Posts: 4
Joined: Fri Sep 04, 2009 7:39 pm
Antipspambot question: 125

Re: Best Fuel

Post by RiverPhil » Tue Sep 08, 2009 6:14 pm

I just talked with FHS fuels and they say propylene oxide can no longer be used in fuels, as it is a carcinogen. I also have a question submitted to the AMA asking them what is now permitted pulse jet fuel.
noclasssmac1972, does the 80/20 methanol/ nitromethane mixture use the same carb jet size as the old methanol/propylene mixture? In other words, is it the same stoichiometric ratio?
Philip

noclassmac1972
Posts: 94
Joined: Sun Jun 05, 2005 5:41 am
Antipspambot question: 0
Location: New Zealand
Contact:

Re: Best Fuel

Post by noclassmac1972 » Fri Sep 11, 2009 10:54 am

Phill the AMA will be changing to 20 nitro 80 methanol fuel next year. For the metering jets you will need to go up 6thou in size for pressure and suction motors .. We have been running this fuel for the last few years here in NZ with no problems

Hope this helps

Robert

gone2fly
Posts: 13
Joined: Sat Sep 19, 2009 10:53 pm
Antipspambot question: 125

Re: Best Fuel

Post by gone2fly » Thu Sep 24, 2009 7:56 pm

I have done some experements with fuel.

If you pressurize a soft drink with CO2 the liquid is adsorb the CO2. If you pressurize gasoline with acetylene it will adsorb the acetylene just like the soft drink does. So I got to wondering if other fuels would do that too??? You do not want to use acetylene in your pulse jet it will get so hot it will melt the engine.

Hydrogen has the ability to burn even if it has an oxygen unbalance of about 50%. If you pressureize a fuel tank of gasoline for about a week at room tempearature the gasoline will adsorb a lot of the hydrogen gas. This gives the fuel the ability to burn with a shortage of oxygen. This increases the fuel mass flow of the pulse jet engine and the thrust goes way up. The excess of fuel acts like a cooling system and the engine runs cooler.

I ran an pulse jet on Methyl alcohol and Ethyl alcohol both with 10% gasoline for easy ignition. The fuel jet has to be larger to to get the engine to run.

Ethyl alcohol, with 35% oxygen, is slightly better than gasoline with 60% of the heat value of gasoline.

Methyl alcohol with 46% oxygen, is better than gasoline and runs cooler.

Alcohol with 10% water produces about the same power as pure alcohol but runs much cooler.

Kerosene produces more power than gasoline. 25% Kerosene 75% gasoline works great in a pulse jet.

yourmom003
Posts: 7
Joined: Mon Oct 12, 2009 9:49 pm
Antipspambot question: 125

Re: Best Fuel

Post by yourmom003 » Tue Oct 13, 2009 5:25 pm

hey, i'm new here. i want to make a go-cart with one of these on it and was wondering what the highest lbs of thrust a propane tank could run, or if i want it to be ran off of deasle/kerosean. i'm looking for between 100-200 lbs of thrust.

PS: i'm also wondering if a valveless or a valved pulse jet is more eficent? thanks

metiz
Posts: 1523
Joined: Fri Apr 21, 2006 6:34 pm
Antipspambot question: 125
Location: Netherlands

Re: Best Fuel

Post by metiz » Tue Oct 13, 2009 6:50 pm

yourmom003 wrote:hey, i'm new here. i want to make a go-cart with one of these on it and was wondering what the highest lbs of thrust a propane tank could run, or if i want it to be ran off of deasle/kerosean. i'm looking for between 100-200 lbs of thrust.

PS: i'm also wondering if a valveless or a valved pulse jet is more eficent? thanks
150 pound should be doable, liquid, with a properly designed engine. Catchy name btw
Quantify the world.

yourmom003
Posts: 7
Joined: Mon Oct 12, 2009 9:49 pm
Antipspambot question: 125

Re: Best Fuel

Post by yourmom003 » Tue Oct 13, 2009 9:24 pm

thanks, you where talking propane right?

and i'm also wondering how far you gould get on one of the standard BBQ sized propane tanks?

metiz
Posts: 1523
Joined: Fri Apr 21, 2006 6:34 pm
Antipspambot question: 125
Location: Netherlands

Re: Best Fuel

Post by metiz » Tue Oct 13, 2009 10:30 pm

yourmom003 wrote:thanks, you where talking propane right?

and i'm also wondering how far you gould get on one of the standard BBQ sized propane tanks?
thats what I was talking about, to. standard propane bottle, flipped upside down with a properly designed engine will give you 150+ pounds no problem
Quantify the world.

yourmom003
Posts: 7
Joined: Mon Oct 12, 2009 9:49 pm
Antipspambot question: 125

Re: Best Fuel

Post by yourmom003 » Wed Oct 14, 2009 2:48 pm

awsome thanks! it'll be a while before i make the jet though, right now i'm making a gasifier as a school project.

yourmom003
Posts: 7
Joined: Mon Oct 12, 2009 9:49 pm
Antipspambot question: 125

Re: Best Fuel

Post by yourmom003 » Thu Oct 15, 2009 2:52 pm

hey, why have the tank upside down though?

dynajetjerry
Posts: 465
Joined: Thu Jan 27, 2005 4:57 pm
Antipspambot question: 0
Location: Ohio, USA

Re: Best Fuel

Post by dynajetjerry » Thu Oct 15, 2009 5:50 pm

Yourmom,
I think pulse-jets usually consume their fuel at such a high rate that gaseous fuels won't flow enough. By inverting the tank, liquid is picked up and will permit proper operation.
Jerry
Louder is always better.

yourmom003
Posts: 7
Joined: Mon Oct 12, 2009 9:49 pm
Antipspambot question: 125

Re: Best Fuel

Post by yourmom003 » Thu Oct 15, 2009 6:21 pm

ok, thats what i thought, but i wasnt sure.

Post Reply