Odd Metal jars

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PyroJoe
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Re: Odd Metal jars

Post by PyroJoe » Wed Feb 01, 2012 5:37 pm


metiz
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Re: Odd Metal jars

Post by metiz » Wed Feb 01, 2012 8:45 pm

hehe I made both of them :lol:
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PyroJoe
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Re: Odd Metal jars

Post by PyroJoe » Wed Feb 01, 2012 10:17 pm

:lol:
I thought that jar looked alot like yours!

The PJ starts easier with the injector pointed down the intake.

Good on you both!

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Re: Odd Metal jars

Post by PyroJoe » Mon Feb 06, 2012 4:29 pm

Assembled all but the water jacket. Here are a few pictures before I welded the internal duct and the top cap on.
The beverage can is for scale, I also included my snorkler as it is only a few percent larger in scale.

A special note in that the internal duct is near twice the diameter of the port!
Have one more pin hole to weld, then it has its maiden alcohol run tonight.

Many apologies Nick that it has taken this long to build it.
Attachments
1.jpg
2.jpg
3.JPG

ganuganu
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Re: Odd Metal jars

Post by ganuganu » Tue Feb 07, 2012 3:03 pm

Please explain me are these jars for experiments or for fun. And is it to analyse anything about the pulsejets performance. Sorry if its a dumb question.

PyroJoe
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Re: Odd Metal jars

Post by PyroJoe » Wed Feb 08, 2012 2:39 pm

Cold virus had me out of operation for a couple days.

Jars represent near pure Helmholtz combustors. As with most design work there are advantages and disadvantages. The task is to find what parameters increase performance in particular areas. Nicks jar is good at producing heat from a small supply of fuel. It also runs on propane fuel which is a difficult process with pure Helmholtz combusters.

As seen in the the "blended body" and "fraction" theory, valveless pulse jets can vary greatly in design and run in a reasonable manner. The jars are more specific in design and have a more defined dimension. In my opinion they are more difficult to design. Many will run, but few will produce high frequency and high thrust.

Even Reynst would eventually apply tailpipes to many of his designs. Very little is known about pure helmholtz combustors. Even in modern analysis of valveless pulse jets you may find the helmholtz parameters completely missing.

I continue to speculate that jars will eventually become better understood, and eventually hope to increase performance with a "blended body" jar. As the port number increases for a given volume, the frequency will shift higher. The main disadvantage of a jar is the lack of a tailpipe and augmentor to supply a returning wave of pressure to compress the fuel air mixture. A snorkle helps, but lacks considerable quantity of mass. Plus the more snorkle that is added the lower the frequency shifts. Very complicated stuff. Even more complicated to optimize.

PyroJoe
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Re: Odd Metal jars

Post by PyroJoe » Tue Feb 14, 2012 3:38 pm

Welded the pin hole leak, and it has no leaks when filled with water and several pounds of pressure applied. Looking for a low humidity day to give it a go.
Last edited by PyroJoe on Tue Feb 14, 2012 8:49 pm, edited 1 time in total.

metiz
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Re: Odd Metal jars

Post by metiz » Tue Feb 14, 2012 3:48 pm

Just run it inside the house :)
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PyroJoe
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Re: Odd Metal jars

Post by PyroJoe » Tue Feb 14, 2012 8:49 pm

Ok, just not on Valentines day! hahaha

kevin lee
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Re: Odd Metal jars

Post by kevin lee » Tue Feb 14, 2012 10:09 pm

you can run it in my house on valentines day, iam here alone ha :twisted:

PyroJoe
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Re: Odd Metal jars

Post by PyroJoe » Thu Feb 16, 2012 6:33 pm

:D
First methanol run went well, the humidity was rather high resulting in a shortish run. Opened a fresh bottle of Heet so it has plenty of pep.

http://www.youtube.com/watch?v=WA7qgoQ5jA0

metiz
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Re: Odd Metal jars

Post by metiz » Wed Mar 14, 2012 7:27 pm

I scaled down Joe's large snorkler to an engine with an intake and exhaust diameter of 30mm (for easy pipe sourcing). It runs like a charm and is startable without air when mounted vertically. I gave the engine to a friend and went testing with him yesterday. It requires a bit of timimg to get the engine going without air but it runs great and has a massive throttlerange. I'll post some dimensions soon.

I haven't drilled a hole in the side of the cc (yet) because I feared the small cc would loose to much compression with a hole like that. We haven't got it to Reynst yet (as well as the large engine btw)

First pic: all those engines are at a friends house - I made all but one :lol:
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Small snorkler.jpg
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metiz
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Re: Odd Metal jars

Post by metiz » Thu Mar 15, 2012 7:12 pm

Here're the plans. If you are using 1mm sheet steel to build this engine you can use the sketchup flat pattern projections. Just print them out 1:1 and trace over steel. If you are using a different metal and you want to stay true to the plans (should't matter to much) you can use the dimensions to build your own cutouts.

This engine, when mounted vertically, can start without air, but it takes some practice. After mounting a 3-point GRIMjector inside the intake at just about the transition point from the cone to the straight pipe, let some gas flow into the engine. All but cut off the gas and light the exhaust pipe. A reddish flame will appear. Wait until the flame turns blue and gets sucked back into the exaust. Just before it reaches the combustion chamber (if you hear a pop you're to late) give the gas valve a good twist. If you timed it right the engine should start right up.

It might be possible to start and Reynst this engine if you drill an injector sized hole in the cc in the weld that connects the top plate to the cc, straight after the intake. I have not tested this, but it's possible in the bigger version.



Original design by Joe"GRIM"Deacon
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PyroJoe
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Re: Odd Metal jars

Post by PyroJoe » Mon Mar 19, 2012 2:09 pm

Thats a neat collection. Thanks for posting the plans.8)

Over several weekends I have tested the large jar, attempting to cross over to propane and found that it is collecting excessive amounts of humidity. It along with various jar designs will only run a short time then cycle slowly until full stop. It is obvious the humidity is high as the when the jars are intubated and fresh air applied, the expelled air is definitely excessively moist. This has been a on going problem across many designs and is not an isolated attribute to this particular design.

PyroJoe
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Re: Odd Metal jars

Post by PyroJoe » Fri Oct 17, 2014 4:42 pm

Example of an inertial pump
In this case the movement of the pump creates the change in velocity.
In valveless pulse jets I would offer that the process is driven by the pressure fluctuations created from combustion (along with the effects of aerodynamic valving).
Attachments
inertial.jpg

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