Fuel for Pulsejet
 

i´m a beginner with my new BMS Dynajet. I tried it with this kind of fuel: 25% nitromethane and 75% methanol to start this little baby. But it doesn´t work. Is my spark to small? It´s only 2mm lenght. Would it work better with a glow plug - This kind of fuel is nearly the same as in our pistons...
Or is it to cold outside +5´Celsius...

What kind of fuel do you guys use for your Pulsejets?

RE: Fuel for Pulsejet
 

Hi Richi-d,
I have used regular gasoline in my dynajet many years ago, even better to use white gasoline (benzine). The key to starting is to get the right amount of air and fuel into the venturi while you have a big spark going. We used an old distibutor fitted with ignition coil and a handcrank at the time....
You need lots of compressed air until you learn the trick... I found that a small amount of air that just about openes a few valves would do the trick. Dont forget your earmuffs and dont get a fright when it starts....its awesome. It gets red hot unless in an airplane where some cooling air flows past.
As far as safety goes have co2 available. If fuel accumulates in the engine or outside, kill the spark and blow clear with air first.
Good Luck
Andre

RE: Fuel for Pulsejet
 

PulseJet Harry has pursued this (very weakly) for years now. We have gotten his to run with regular old gasoline, but not reliably (far too sensitive to fuel system head pressure). So he talked to the guys out in the Western USA that fly them all the time (is it Thorpe???). They told him to run something like 75 or 80% methanol and the rest ether and use a small Cline pressure regulator with a pressurized fuel bladder. I have no doubt this would work very well (at least it does in their videos), however I believe PulseJet Harry had damaged the regulator before we got a chance to try it. He is working on getting another for another attempt. Unfortunately, he has way too many ores in the fire and only has time for about one attempt every 9 to 12 months. The last try was the weekend after the Columbia tragedy. Based on that progress, I expect success in 2009.

RE: Fuel for Pulsejet
 

Pulsejets, like turbines, will generally run on anything that will form a stoichiometric (combustable) mixture with air.

The Dynajet likes white gasoline but regular gasoline will also work. If you want to use methanol then you'll need to ensure you''ve fitted the atomizer jet with the largest holes. The Dynajet usually has the gasoline-sized jets fitted which are too small for methanol and won't allow enough fuel to flow.

Starting them takes a bit of practice -- you have to get the air-flow just right and a nice hot spark helps a lot. Check out my "Starting a Pulsejet" page at http://aardvark.co.nz/pjet/starting.shtml

Note also that if it's cold where you are, the engine will be a lot harder to start. This is because a pulsejet atomizer does a lousy job of converting fuel into fuel droplets small enough to generate a combustible vapor. When it's really cold, heating the body of the engine itself before starting can help immensely. Even if you just raise the temperature so that it's just too hot to touch you may find it bursts into life far more easily.

As another poster has pointed out, these engines are incredibly sensitive to fuel-head so you need to get the fuel-level as close to the atomizer level as possible. Remember also that a single small bubble in the fuel line will cause the engine to stop.

The Cline regulator is absolutely essential if you're going to try and use the Dynajet in anything other than a control-line speed plane. If you try to use it in an RC or CL-sports model then the moment you put the nose up, the dynajet will likely stop due to the changing fuel-head.

Modern pulsejets (yes, there is such a thing) tend to inject the fuel directly into the combustion chamber as this not only makes starting much easier and eliminates the effect of fuel-head variations, it also allows you to throttle the engine down to as little as 30% of full power.

There's a heap more stuff on my website at http://aardvark.co.nz/pjet/ if you're interested in pulsejets and I have published an e-book that has a lot more info.

RE: Fuel for Pulsejet
 

XJET IS THE MASTER OF PULSE JET ENGINE. CAN,T GET NO BETTER THAN THAT.

RE: Fuel for Pulsejet
 

Richi,

I have one of these and have run it exactly the same fuel as you. What number jet are you using? I used a 0.062mm which ran OK. As long as you have a spark it should start. To start mine I onlt used a bicycle pump and some (read a lot) of effort. In your case I think it's the cold temperature that's your problem.

BMS engines do start and run well and Earl Bailey is a real nice guy who sure knows his stuff. Do you have the stock engine or the speed engine. The speed engine would be more difficult to start.

Regards,
Tony

RE: Fuel for Pulsejet
 

Thanks to all... I see - only buy one and fly isn´t possible! But thats the reason why it´s so fascinating!

To Tony:
I have the sport-jet version - the smaller one. Maybe when it ran good, I will buy the stronger one - the quality is fantastic!
Mr. Bailey gave me three sizes 0.56/.057/.058 and wrote that these sizes are optimal for Methano/Nitromethan. He helped me a lot.

With all your help, it will be a interesting weekend!

Thanks
Richi

RE: Fuel for Pulsejet
 

Thanks for all your help!! It´s running!!

I started it with 75% methanol and 25% nitro. For ignition I used a sparkler (fireworks). I think it will also work with the spark, when the weather is not so cold!

The question: does anybody know somebody who produces small size fuel-pumps? It ran without one this weekend, but for use in a plane it will be a must. The preassurized tanks are to dangerous I think - can´t stop them when they have a leakage

RE: Fuel for Pulsejet
 

Well done Richi,

I bet you found it started even easier after the first run. Can't beat the noise of these things.

As for fuel systems, yes you could use a small electric fuel pump which are easily available as we use them on our turbine engines. However, they are not cheap and cost around £60 and upwards. There are a number of alternatives open to you. I know people have had success using a latex bladder as a fuel tank, inflating it with fuel and due to the tension of the bladder gives you a constant head pressure plus no chance of any bubbles (important - 1 bubble = engines stops). The alternative is to use a bag in a bottle approach and pressurise the inside of the bottle from a pressure taping from the engine. Again, fill the bag and bleed out any air. I've also heard that alot of people have done this in conjunction with using a 'Cline Regulator'. This is a small device which is a demand type regulator, i.e. it only allows fuel to flow when there is suction from the engine. You should be able to find the website easy enough.

The electric fuel pump method is probably the most expensive and difficult to get set up plus there's the weight factor of pump, batteries and controller. You only need a constant headpressure and this can be done by other cheaper means. Keep it simple.

Any ideas of what you are going to put the engine on/in?

Regards,
Tony

RE: Fuel for Pulsejet
 

Hi tjay-

I will see where I can get a cline regulator. Does anyone have some photos of these bladder tanks or this bag in a bottle? I can´t imagine how it should work!

I want to build a V1 Rocket, but I´m still looking for drawings!! Does anyone have such plans? I was searching for hours in the web!

RE: Fuel for Pulsejet
 

Cool! V-1's are neat, I want to build one with a pulsejet sometime too. I figured I would make that launch rail too:D

Right now I am working on a V-2 rocket, just making the plug for fiberglass molds. It is 7'6" tall and will be powered with a hybrid rocket engine.there are a few picts on my site [link]http://www.rpmodeltech.com[/link]

Good luck with the project, I look forward to seeing some picts here;)

RE: Fuel for Pulsejet
 

Here's a V-1 3 view:

[link]http://www.fortunecity.com/marina/manatee/272/v-1.html[/link]

Beauty about it is you really dont need plans, everything you need is on the 3-view. That round rocket like fuse is simple enough.
When I build one I will move the wing back somewhat and the engine a little forward, otherwise you will never get that CG right without a ton of lead {warhead in the original}

I was also thinking of an engine "shroud" that fits close over the engine to give that scale size to the smaller tube model pulsejet.
This could also cool the engine if it is placed right at the end of the tailpipe.

RE: Fuel for Pulsejet
 

Hi RPMTECH,
great project - your V2 - really great.
Yes you´re right- building a V1 will be easy. Do you have some plans with the dimensions? Else it will be more difficult..

richard

RE: Fuel for Pulsejet
 

Hi Richard, Sorry I dont have any plans but could draw some up as I would like a set also. I can do it this evening and I will send you a copy if you like. I usually build stuff from 3-views. I wont do any ribs or cross sections but will do all the dimensions and scaling, you really dont need cross sections as the V-1 is round. Everything needed is on that 3-view. What size were you thinking? Anyway I will include formula to make one any size you like. I will post here when I am finished with them.

Rick

RE: Fuel for Pulsejet
 

Wow, that absolute great!
I think about a 1,0m - 1,10m wingspan..

RE: Fuel for Pulsejet
 

I ran my 1st on 115/145 av gas, it ran a bit hot but was fast..reeds survived flights, i didnt.
For Sale, my last german pulse jet, japan f84 melal c/l kit and ralphs U2 plans.
Offers?

RE: Fuel for Pulsejet
 

What German pulse Jet is it? Do you have photos? What happened?