Would this work? Project: BenJet XL 0.1

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BenJet
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Re: Would this work? Project: BenJet XL 0.1

Post by BenJet » Sun Feb 14, 2010 3:21 pm

Viv wrote:
BenJet wrote:
Viv wrote:Hi Ben

Here's some thing for you to read ;-)

Viv
That is a nice piece of engineering, but it has one problem. :twisted:

It is has moving parts! That's a pain in the ass to change valves every x times. And personally I think I could not afford making that engine out of complete stainless steel or titanium. Because I will not work my ass off in designing/building an engine with crappy materials and see it engulfed in flames the first day of usage! Because I'm going to pwn it with massive fuel! And it must withstand. :D :lol: :lol:

I have to go to Switzerland in March and visit the parents of my girlfriend :shock: ... That money could have been inverted buying some nice stainless steel plates for my current project. :D :lol:

The start of building of the current project will be delayed 5 days, because one of the team members (one of the the metal guys) had to leave to France. He will come back next Friday :cry: . Patience, my friend... patience. I do not have patience!!!! Well at least I have time to finish the control panel :)

No, seriously now. Building that thing is over my level and possibilities, it was a nice read and it might help me for future projects. But now, wait until I get my current project done. :P

Greets
Ben
Hi Ben

The general idea was to give you a pointer towards the USPTO office and their very excellent search function, you can spend many happy hours there researching what has already been published on the subject ;-)

Melenric is a good place to start but try Dunbar and Bodine too ;-)

Viv
Indeed, I've been doing that. I like Google Patents. It is really well done. Just discovered it like 3 days ago or something and was very impressed. Going to check the names you told me and see what I find :)

Greets
Ben
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Viv
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Re: Would this work? Project: BenJet XL 0.1

Post by Viv » Sun Feb 14, 2010 5:44 pm

Hi Ben

Glad you found it, it will give you answers yes, but also more importantly give you the ability to pose better questions ;-)

Viv
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BenJet
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Re: Would this work? Project: BenJet XL 0.1

Post by BenJet » Mon Feb 15, 2010 2:20 pm

Jutte wrote:OK - wrote a big reply but my computer ate it - so will give it another go.
Just a few ideas...for the sake of the following consider a basic straight pulse jet - not a folded one.
OK - its a given that an outer shroud casing will stuff up the acoustics etc.
But what if you "retune'( shorten) the tail pipe so it resonates within the shroud
and still runs - ( a problem would be the returning hot gas piston - enough to produce thrust
within the shroud and enough to return for reignition etc...and what to do with the intake etc)?
In one of my experiments I sucessfully ran an enclosed shroud without retuning of the pulse jet.
The experiments had nothing to do with what Ben suggested but they were successful ( yes you can silence/quieten
a pulse jet to keep neighbours happy - the good wife happy ...the mother inlaw relatively impressed AND happy
{bonus points there guys} :lol: )
Another idea - why not a preforated barrier ( eg: as in a rijks tube but axially) that the pulse
jet sees it as a 'resonance barrier' but still enables the use of an outer shroud as Ben suggests.
I can't really do much experimentation now as I have recently rejoined the student world - and with
a family it changes things a bit.
However still managed to fire up the LPG Cylinder quiet pulse jet so the kids could toast
marshmellows . :D
OK just ideas - feel free to shoot down etc.
Hey Jutte, I hate when that happens.

I've just re-read the whole topic, and just seen your post. Damn I'm blind lol :P

It would be cool to be able to silence them some way without loosing to much thrust. But well thats still an area to investigate. I can't run a pulse-jet in my garden, because I do not have one. I life in a flat. so i have to start that thing somewhere else, so its ok if its going to be loud lol :D :lol:

The last design is the definitive (posted here viewtopic.php?f=3&t=5688&start=0#p68552 ) does not have shroud. I din't know that shrouds interfere with the engine operating well. That's why I changed plans. This one is simpler to build and it seems that it is going to be powerful.

I just hope everything goes well. Would be a bust if this thing is not going to run like it should, in the end, it will be an expensive 1,60 meters (59 inches) long and 30cm (11,8 inches) diameter marshmallow toaster. Since its going to be stainless steel I might even use it to cook fillet steaks on it. :lol: :roll:

See you around,
Ben
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karel
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Re: Would this work? Project: BenJet XL 0.1

Post by karel » Mon Feb 15, 2010 9:55 pm

I believe you are planing to build a BIG pressure jet judging on the supersonic intake. in that case you have to sonically tune the 3 phase intake with the CC or something like that or you end up with a 3lb thrust flamethrower. as for me, I don't have that kind of calculus knowledge i wanted to build a pressure jet myself, until i found out i was probably going to make a fancy flamethrower hahahaha, going for the lockwood/hiller now ;)

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Re: Would this work? Project: BenJet XL 0.1

Post by BenJet » Mon Feb 15, 2010 10:29 pm

karel wrote:I believe you are planing to build a BIG pressure jet judging on the supersonic intake. in that case you have to sonically tune the 3 phase intake with the CC or something like that or you end up with a 3lb thrust flamethrower. as for me, I don't have that kind of calculus knowledge i wanted to build a pressure jet myself, until i found out i was probably going to make a fancy flamethrower hahahaha, going for the lockwood/hiller now ;)
Hello Karel,

The sizes for this engine (the last one) are the correct ones, I've looked into that already.
Yeah well, it's kinda funny only for putting the fuel pipe in the compression chamber its already a pressure jet.
The only question I have now is how think the steel should be...

Saludos
Ben
Last edited by BenJet on Mon Feb 15, 2010 10:48 pm, edited 2 times in total.
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Johansson
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Re: Would this work? Project: BenJet XL 0.1

Post by Johansson » Mon Feb 15, 2010 10:31 pm

BenJet wrote:The sizes for this engine (the last one) are the correct ones, I've looked into that already. The only question I have now is how think the steel should be...
How do you know that?

BenJet
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Re: Would this work? Project: BenJet XL 0.1

Post by BenJet » Mon Feb 15, 2010 10:48 pm

Johansson wrote:
BenJet wrote:The sizes for this engine (the last one) are the correct ones, I've looked into that already. The only question I have now is how think the steel should be...
How do you know that?
I've found steps on the internet on how to calculate it, it was posted by some Engineer. I've written it down on a piece of paper, it was not 100% complete but I figured out the missing numbers, and I'm sure they are correct.

Greets
Ben
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karel
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Re: Would this work? Project: BenJet XL 0.1

Post by karel » Mon Feb 15, 2010 11:31 pm

Yeah well, it's kinda funny only for putting the fuel pipe in the compression chamber its already a pressure jet.
It's not only for putting the fuel pipe into the Combustion Chamber what makes it a pressure jet for me, its the 3 stage intake with the supersonic noozle and zero Pulsations, but merely a Pressurized injection what I think makes this design a helluva pressure jet, due all respect.

also, if running on liquid propane you need no flame-holder, for burning propane sticks to the walls of the CC, thus beeing the best possible flame-holder by itself.

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Re: Would this work? Project: BenJet XL 0.1

Post by BenJet » Tue Feb 16, 2010 11:33 am

karel wrote:
Yeah well, it's kinda funny only for putting the fuel pipe in the compression chamber its already a pressure jet.
It's not only for putting the fuel pipe into the Combustion Chamber what makes it a pressure jet for me, its the 3 stage intake with the supersonic noozle and zero Pulsations, but merely a Pressurized injection what I think makes this design a helluva pressure jet, due all respect.

also, if running on liquid propane you need no flame-holder, for burning propane sticks to the walls of the CC, thus beeing the best possible flame-holder by itself.
True, BTW your suggestion about the flame-holder and fuel is to appreciate :D

Image

Here is the exact list of pieces: 8)
1. 1st Air Intake, Length: 22,50cm - Diameter: 9,55cm
2. 2nd Air Intake, Length: 45,00cm - Diameter: 12,75cm
3. 3rd Air Intake, Length: 30,00cm - Diameter: 15,00cm
4. Comb. Chamber Disc, Inner Diameter 15,00cm, Outer Diameter 30,00cm
5. Comb. Chamber, Length: 55cm - Diameter: 30cm
6. Funnel, Length: 15cm - Diameter 1: 30,00cm - Diameter 2: 20,00cm
7. Exhaust, Length: 32,50 - Diameter: 20,00cm
8. The fuel tube inside the combustion chamber till the nozzle has 4cm of diameter.

9. The air intakes have a flared entrance, so the airs gets rushed in, its not on the design yet. The flared part is very small and to be "added" to the actual length. But I don't know how much yet. :roll:

10. Spark plug somewhere in the cc, not really relevant where it is.
11. Flame holder as a simple wire soldered right behind 3th air intake.

EDIT: Ummm, just noticed, this should go into the pressure jets forum then.

Greets
Ben
Last edited by BenJet on Tue Feb 16, 2010 3:16 pm, edited 1 time in total.
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Re: Would this work? Project: BenJet XL 0.1

Post by Viv » Tue Feb 16, 2010 2:13 pm

Hi Guys

Some quick answers

!/ Pulse jets do not use flame holders, Ramjets do
2/ liquid propane does not stick to the walls of the cc and burn (what!)
3/ Pressure jets do pulsate and are pulse jets with an tuned ejector inlet for self starting, they are not Ram jets or steady state burners.

Ben meet Michael Stram, Michael meet Ben ;-)

Viv
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BenJet
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Re: Would this work? Project: BenJet XL 0.1

Post by BenJet » Tue Feb 16, 2010 3:12 pm

Viv wrote:Hi Guys

Some quick answers

!/ Pulse jets do not use flame holders, Ramjets do
2/ liquid propane does not stick to the walls of the cc and burn (what!)
3/ Pressure jets do pulsate and are pulse jets with an tuned ejector inlet for self starting, they are not Ram jets or steady state burners.

Ben meet Michael Stram, Michael meet Ben ;-)

Viv
Thanks Viv,

Nice to meet you Michael, even if you are not reading me :lol: , I see you are using a wire as flame-holder. That clears the question of post: viewtopic.php?f=7&t=5690 but I still think you can use a better option than a "wire".

:arrow: Viv: I can't find information about the flaring if the air intakes in his document, and the picture does show that the intakes are flared. I think I am getting blind or I am jumping over some information. Are the crossover zones on my design correct? I'm a bit confused now. This paper is no the same the one I've taken the ideas out, and still no information about the flaring.

Hopefully getting my hands on it this weekend.
Ben
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Re: Would this work? Project: BenJet XL 0.1

Post by Viv » Tue Feb 16, 2010 3:43 pm

Hi Ben

Its not a wire flame holder, lets get that sorted out, what it is a hot wire re-igniter, basically pulse jets have a bad habit of going from full power to no power in one cycle if they miss a beat, that's bad if you happen to be relying on that power to stay in flight ;-) one of the reasons why you wont find man powered pulse jet aircraft, the wire in Stram's engine glows red hot during running and acts as an ignition source if the engine misfires.

It does work as I have tested it in a pressure jet using acoustic analysis to see the difference it causes to a rough running engine.

Inlet flare information you can find by searching the NACA technical servers, you will find a lot of good stuff there so I suggest you spend your time reading some of the reports on pulse jet and ram jet studies.

Q/ "are the cross over zones correct" no but that's design information I spent a lot of time gaining so its not available for free as it has commercial applications ;-)

Viv
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BenJet
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Re: Would this work? Project: BenJet XL 0.1

Post by BenJet » Tue Feb 16, 2010 7:36 pm

Viv wrote:Hi Ben

Its not a wire flame holder, lets get that sorted out, what it is a hot wire re-igniter, basically pulse jets have a bad habit of going from full power to no power in one cycle if they miss a beat, that's bad if you happen to be relying on that power to stay in flight ;-) one of the reasons why you wont find man powered pulse jet aircraft, the wire in Stram's engine glows red hot during running and acts as an ignition source if the engine misfires.

It does work as I have tested it in a pressure jet using acoustic analysis to see the difference it causes to a rough running engine.

Inlet flare information you can find by searching the NACA technical servers, you will find a lot of good stuff there so I suggest you spend your time reading some of the reports on pulse jet and ram jet studies.

Q/ "are the cross over zones correct" no but that's design information I spent a lot of time gaining so its not available for free as it has commercial applications ;-)

Viv
Yeah, I understood that its going to be a glowing wire, thats why I asked in the construction forum for good material since, im afraid that if its done with staineless steel its going to "get consumed". :roll:

Thanks for the other info, I've already figured out the measurements and working on the next plans... :cry: :x but its going faster now that i've got some practice :D :D

Greets
Ben
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Re: Would this work? Project: BenJet XL 0.1

Post by Viv » Tue Feb 16, 2010 7:50 pm

Hi Ben

Ok skipping over the part were a flame holder is not needed then, looking forward to the video ;-)

Viv
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Jutte
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Re: Would this work? Project: BenJet XL 0.1

Post by Jutte » Tue Feb 16, 2010 7:52 pm

Hi Viv,
I have seen that hot wire igniter on that patent before - and it intrigued me - so just
a few questions.
Does that pressure type intake 'stack' need that because of the pressures can
overcome the returning tail pipe hot gases and 'blow' them out?
And - is it really applicable to 'normal' pulse jets or just to the 'pressure jet'
class of pulse jets? ( - what is that wire - stainless steel?)
Thanks - hope the winter is not too savage where you are - we are
having a pretty good summer here - Cheers.

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