Fire in the hole!

[El-Kablooey]

NICE!

[Eric]

Yes very nice. You look like it tried to eat your hand the way you jumped back :D

So are you going to remake the valve system and try again? Maybe get it running on high?

Eric

[Eric]

Heres another thing you can do. Have the propane feed line go to a larger diameter distribution line, that will cool the valve grid, and also do a good job of preheating the propane.

If you feed it off of liquid fuel from one tank your valves and valve system will stay nice and cool, maybe even frosty cool.

[MB]

Interesting concept. Hmm...

Yes! We are definately getting ready for another firing next Saturday. We have the grid rebuilt, we've re-engineered the whole fuel nozzle thing, and have deployed a load cell to measure the thrust.

I took a regular square-head plug (1/8" pipe fitting) and drilled a tiny hole down the center with my Dremmel, then coutersunk a deep V (on the outside) and drilled 5 tiny holes radially into the V (perpendicular to the side of the V), and 5 connecting tiny holes up to the the radial holes (per the attached sketch cross-section). I tested it with water, and it produces a very nice atomization pattern.

[Eric]

Does it have any internal cooling fins? Even if you get the combustion in the right place the plate is going to get pretty damn hot without any increase in intake side surface area because its not getting a lot of cooling from moving through the air.

For the test run you might want to take a squirt bottle of water along and just spray a fine mist into the intake, if you see it vaporizing on contact then its going to get too hot, especially at max thrust.

Also a mixture of 50% methanol 50% water should cool quite well if you have any.

Are all the holes the same size? Try making a nozzle with 5 holes total, all the same size. One going down the center, and 4 drilled perpendicular to the countersink, and have them positioned so that they are tangental to the center hole. It basically makes a mini tornado that creates a ton of turbulence and sucks in a lot of air for a very short fat flame length that is very intense and extremely hard to blow out. You should be able to ligth it outside the engine and crank the fuel flow all the way up and have the flame stay right at the base of the vortex. The short flame length is a good indicator of mixing and burn rate.


Eric

[dynajetjerry]

Eric & MB,

Aeromarine's 8 in., 210 lb. thrust pulsejet also employed an aluminum valve grid but of a design that differed from all the others that have been posted here. It is worth repeating that this system yielded a reed valve life that was at least 2 hours, static, on gasoline. One test lasted for 10+ hours before the reeds began to leak, slightly. Even so, it continued to run and the seats were not badly damaged.

As I've mentioned before, there were 2 fuel injector systems: one in the intake throat and upstream of the reeds; ithelped cool the reeds. It supplied 1/2 the fuel flow. Inside the combustion chamber and immediately behind the valve grid was a system of 12 spray-head injectors, modified from oil burner nozzles and it supplied the other half of the fuel, a total of 400+ lbs. per hour.

There were "turbulators" inside the engine but they served, mainly, to keep the flame toward the front of the chamber rather than aid in cooling. They were adopted to reduce the usual fall-off in thrust as air speeds increased, a common failing of many valved pulsejets. The final test article retained a flight thrust of almost 190 lbs. at 350 mph, much better than earlier Aeromarine designs.

Jerry

[MB]

Two questions:

Eric,

Where can you buy Methanol? I presume because it's hazardous you can't just run down to Home Depot and pick it up like denatured alchohol or something.

Jerry,

Are the plans or specs or photos or something of the Aeromarine pulsejet on the web somewhere? Anything of dramatic improvement would be of great interest to me.

[Eric]

Ethanol would probably work ok too.

Methanol is used in water methanol injection systems, which greatly cool the incoming air charge in the engine to create a more dense fuel air mixture. Any performance car place should be able to order it for you.

You can get it in small quantities at walmart in yellow bottles called HEET gasline antifreeze / water remover which will work well for a test with the engine since its only like 80 cents for a 10 ounce container.

Eric

[tufty]

Ethanol would probably work ok too.

Methanol is used in water methanol injection systems, which greatly cool the incoming air charge in the engine to create a more dense fuel air mixture. Any performance car place should be able to order it for you.

You can get it in small quantities at walmart in yellow bottles called HEET gasline antifreeze / water remover which will work well for a test with the engine since its only like 80 cents for a 10 ounce container.

Eric

Unless I'm reading this wrong, Eric, adding methanol to the mix will greatly reduce the cooling available (although it will result in more combustible fuel in the charge); the latent heat of evaporation for ethanol is around 900 kj/kg and for water is around 2300 kj/kg (or, if you prefer in Btu/lb, 390 vs 970). Meaning that you will get more cooling / volume using just water, especially when you consider that the density of methanol is approximately 3/4 that of water.

Simon

[dynajetjerry]

MB,
No, as far as I know, none of the Aeromarine designs are posted on the internet. If and when I can figure out how to send attachments to my Email or Forum messages, I will post a few of the pictures and drawings that I have from Aeromarine. (I got all of them from Bill Tenney's widow about 8 years ago.)
Jerry

[Mike Everman]

Jerry, I'd like to help with posting pictures from you. Can you tell me what setup you have, computer, operating system, etc. Is it that you don't have a scanner, digital photos, or digital camera?

[Eric]

I mean that the water-methanol injection systems are used to greatly cool the air mixture.

Running a dynajet on methanol will result in the valve head getting frost on it.

Even running more water flow through the valve head and running on propane I have never had the valve head get as cold as with methanol.

The methanol-water mixture will give a good deal of cooling, and more power than a pure water mixture.

Eric

[Mark]

If you put some water on your hand and blow on it, it gets kind of cool. If you put methanol on your hand and blow it gets cooler than water. Or you might rather try ethanol, both alcohols evaporate at a lower temperature than water. Next try some liquid helium. ha
Mark

[noclassmac1972]

http://www.worldwideracingfuels.com/ourproducts.html Heres a web page which you can get some Methanol they also suply nitromethane and propylene oxide. If we can get it too NZ You guys can definately get it over there....

Robert Bolton

[evildrome]

Hi Jerry,

If you tell me what email program you have I will do you a blow by blow picture tutorial on how to send attachments. I would very much like to see some pictures or drawings of the Aeromarine valve setup.

Alternatively, can you copy your pictures onto a CD? If so, then you could mail it to Eric who will post them on the site for you. I would offer to do it but I'm in the UK which complicates postage.

BTW the idea of having half the fuel enter before the valves is a smart way to keep the valves cool. How did they stop the fuel igniting before it gets to the valves (especially when run static) ?
I take it the intake features a venturi that keeps the airspeed above the flame speed till after the turbulators?

Cheers,

Wilson.