Please put your "I am new and need help" question here.

[username]

my valveless pulsejet design.JPG (2.25 KiB) Viewed 11018 times

I built this tiny thing in 2 days. it has a 1/2" diameter exhaust, a 3/4" combustion chamber, a 1/4" air intake and a 1/8" fuel intake. All the parts are made of copper and are soldered together, seeing as i dont have anything to weld with.

I tried to fuel it with mapp gas, and i lit the end of the tube, seeing as i can't fit a spark plug on this. I was hoping that if i could get air into the intake, the flame would jump down into the combustion chamber and the engine would start. But i'm not sure this thing is even going to work at all.

Earlier in this thread I read that you need a fast burning fuel for tiny engines, and I don't think i'm fueling this thing right in the first place. When i put air in the intake, the exhaust just shoots out a huge fireball.

Will this design ever work? At first i thought that all the parts of the engine needed to have certain proportions. I was all excited to build a jet and just rushed into it and built one. I'm not so sure that was a good idea. So my question is, what's wrong with this engine? If there's nothing wrong, how can i possibly start this? Also, what fuel should i use and how should i fuel it? I first thought that the fuel was not pumped in, but was sucked in along with the air via the vacuum in the chamber. But this would mean that using gaseous fuels is not possible, and seeing as it is, i then figured that the fuel is constantly pumped in, which is what i did.

So anyways, i'm really confused about everything. How do i fuel it? are my proportions on the engine right? what fuel do i use? Any help is appreciated.




Edit:
http://www.youtube.com/watch?v=y6jYTOeIRJs

I got a video of it failing....if that helps.

The only thing i can think of doing is giving it a hotter fuel or giving it more fuel.

[username]

Well i extended the exhaust pipe by 6 inches, so the combustion chamber to exhaust pipe ratio is 1:5, or in this case 2:10. I figured there needed to be more of a vacuum in the combustion chamber, so more air would get sucked in. But the engine easily dies from giving it too much air in the first place. And i can't possibly imagine i need more fuel, i'm already giving it tons of gas. when i give it only a little bit of gas, it also dies.

i'm not sure what the problem is anymore. All the pieces are there, it should work with everything it has. I can't really use a design that's already out there, the designs don't come this small. And if i were to scale down a design i would get what i already have right now ; a minuature pulse jet based on the "chinese" design. The only thing i can think of now is using acetylene....

[Max]

Hello everyone,
My name is Max Rübsam and I am from Germany.
ME and two friends wanted to build a Puls Jet for a Physikgameshow, which will be seen on our school (Gesamschule Giessen-Ost, near Frankfurt).
After we have build a Prototype we realized that it does not work like we wanted to. The gas just burned(so we only got a flamethrogh), but the desired reaction was not to see.
We had to make the gas chamber angled, because we had not the best tools. The mainpipe is about 30cm long and we use propangas.
May you give us some advice, a checklist or some tips?
Do we have to use compressed air?
Regards from Max Rübsam

[metiz]

Hello everyone,
My name is Max Rübsam and I am from Germany.
ME and two friends wanted to build a Puls Jet for a Physikgameshow, which will be seen on our school (Gesamschule Giessen-Ost, near Frankfurt).
After we have build a Prototype we realized that it does not work like we wanted to. The gas just burned(so we only got a flamethrogh), but the desired reaction was not to see.
We had to make the gas chamber angled, because we had not the best tools. The mainpipe is about 30cm long and we use propangas.
May you give us some advice, a checklist or some tips?
Do we have to use compressed air?
Regards from Max Rübsam

You need to give us a bit more details for us to be able to help you. Do you have any photographs, video or plans? do you use a gas restrictor? what kind of gas bottle do you have? etc

[Max]

ok
I can control the gas with an regulator which is on the gas bottle.
I start the puls jet with throwing a sparkler into it, then I turned of the gas, but nothing happend. After that I first turned the gas on and then I just hold the sparkler in front of the puls jet, but I only got a big flame.
The Puls Jet is about 70 cm long front-behind
The mainpipe is about 50cm long and got a radius of 2cm, at the end of the mainpipe I fused an angled, not symmetric conus, which`s radius is getting bigger till the end. On this conus, I fused a little pipe (radius 1cm) which is bent so that it is paralell to the mainpipe, but it is only 10cm long. Into that little conus I stuck a long, very thin pipe, which is conected to a flexible tube,which is connected with the gas bottle.
(I tried to load a picture, but it always says the picture is invalid)

[Max]

hi everyone
I`ve talked with a prof and got most of my questions answered.
But I got a few left.
Do I have to boost the gas?
Do I have to put gas first and then detonate it, or can I through a sparkler into it and then turn the gas on?
And can I choose the dimensions as I want to, or do they have to be in a especially propotion?
Thanks

[metiz]

The dims have to be proportional
You'd best lose the gas restrictor
sparkler > gas is good

try again in uploading a pic or a drawing with the dimensions. make sure the pic is saved as a jpeg and does not exceed 2mb.

[Max]

thx that do help me a lot for the moment.
but in which proportional do they have to be?

[metiz]

thx that do help me a lot for the moment.
but in which proportional do they have to be?

there is no simple answer for that: this forum is here for a reason. just post some plans

[Max]

This is the link where u can see the plans.
http://max.jtmi.de/

there are 4 pictures.

The first, the second and the third one shows our pulse jet.
The other ones are plans, which I wanna know if they work.
greeds max

[metiz]

the escopette wil work. What I can see of the incredebly blurry photograph you provided, you need to lose the restrictor on the gastank and then try again. As for the excel sheet: I can't read German.

[Max]

hi everyone
i have another plan. www.max.jtmi.de
please tell me if it will work.
Thanks a lot
Greez Max

[Muddydisco]

Hi guy's I'm looking into building my first valveless pulsejet And can't find any info on the ratios or size relations for inlet,cc and tailpipe? So I have a cc thats conical on each end. Dia = 5", Length = 9", each cone is 3" in length and reduces down to 2" dia so the total length is 14" if you get me?
Was looking at making it into a chinese cs type by blanking off one end and putting spark plug into it.
So? Inlet how long and Dia? and exhaust how long and Dia?
Many Thanks
Nick

[ace_fedde]

Muddy,
If you do your first build please stick to the plans of known working PJ's. It will be hard enough to get them running and tuned.
Later you can, after studying, start to experiment with your own designs.

Fedde

[ace_fedde]

Could electric ducted fan replace leaf blower to start a valveless pulsejet (mini thermojet)?
I don't have propane tank or leaf blower.
Use butane lighter refill bottle + rosscojector, the engine failed to start

Well, a leaf blower is in fact also a ducted fan... I think the problem is in the lighter refill bottle, not enough gas flow.
Why don't you post some pictures that show the sizes of your equipment and the way it is installed?

Fedde