ramble about jets and potstands

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DarenN
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ramble about jets and potstands

Postby DarenN » Sun Feb 14, 2010 12:52 pm

i once read something about jet size and number of jets as pertaining to bloom time.
something like, more/fewer jets blooms faster/slower. and. larger/smaller jets blooms faster/slower.
does anyone know about this?
i've found that bloom time is signifigantly affected (lengthened) by useing an integral potstand in the Pepsi G. sure, the potstand returns heat to the burner, but it also steals heat from the burner during the initial warm-up period, lengthening the time it takes to bloom. the Trangia burner blooms in about ten seconds. i see no reason why the Pepsi G can't do the same. i've made the G boil 2C/1/2oz but it takes two minutes to bloom. not acceptable. i need to lower that bloomin' bloom time! ;)
"I'd rather be happy than right." Slartibartfast

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DarenN
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Re: ramble about jets and potstands

Postby DarenN » Sun Feb 14, 2010 5:09 pm

Jon
it's just a regular Pepsi G, but with 24 jets @ .0325, and an overall hieght of just 1". the bottom is the outside so i get a max. cap. of nearly 1oz. the potstand is integral like this ION. potstand hieght = 1/2".
Image
"I'd rather be happy than right." Slartibartfast

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Re: ramble about jets and potstands

Postby DarenN » Mon Feb 15, 2010 9:07 am

yes, lower potstand hieghts will cause longer bloom times. also, longer burn times.
"I'd rather be happy than right." Slartibartfast

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zelph
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Re: ramble about jets and potstands

Postby zelph » Mon Feb 15, 2010 11:54 am

I agree.............stove science 101 :D
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Re: ramble about jets and potstands

Postby zelph » Mon Feb 15, 2010 5:58 pm

It's the top edges that are heating up and transfereing heat to the entire stove body. Once the fuel begins to boil inside the double wall the jets ignite and all flame takes to the outer rim and forms the circular ring of fire. Once the ring forms, no oxygen can enter to the center of the stove.
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zelph
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Re: ramble about jets and potstands

Postby zelph » Tue Feb 16, 2010 12:46 pm

just tinkering wrote:Right, so that by deforming the top and pushing the rim down, more air can be supplied during the initial burning of the inner chamber (not bloominging yet). This might cause the alcohol to boil faster and get the bloom to occur earlier. And this is done without changing the pot to jet orifice position. Once the jets bloom (no air to the inner chamber), the air supplied to the jets remain the same. So, lowering the inner lip may reduce the bloom time. Does this make sense?

Jon


I don't think it's going to make much difference at all. Only one way to tell, make one with a pushed down rim and one without and do 3 timed tests under optimum conditions(no breeze)
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DarenN
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Re: ramble about jets and potstands

Postby DarenN » Sun Feb 21, 2010 7:36 am

insomnia sucks! but it's a fine time to do stove testing. ;)
still messing about with the Pepsi G, i built one with 24 jets at 0.0315", and gradually openned the jet size all the way out to 0.0625.
here are my findings. all tests were done without a windscreen or potstand. all with 15ml of Methyl Hydrate.

jet size. bloom time. flame out time.

.0315 - 0:49 - 3:13

.039 - 0:47 - 3:06

.046 - 0:45 - 3:05

.0625 - 0:43 - 3:10

all tests were done three times and averaged to get the numbers you see.
one other thing i did was to compare with and without the internal potstand as shown in the Ion pic earlier in this thread. the test times with the potstand were as follows:

.0315 - 1:49 - 3:53

look at the dramatic difference in bloom/burn times that the potstand creates! :o

so i pulled the potstand out of that Ion i showed earlier and got these results.
6 jets.

.046 - 0:07 - 5:54

that's more like it!but i'm still kinda partial to the ol' Pepsi G so i ain't done with it yet. ;)
"I'd rather be happy than right." Slartibartfast

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zelph
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Re: ramble about jets and potstands

Postby zelph » Sun Feb 21, 2010 11:06 am

look at the dramatic difference in bloom/burn times that the potstand creates! :o

so i pulled the potstand out of that Ion i showed earlier and got these results.
6 jets.

.046 - 0:07 - 5:54

that's more like it!but i'm still kinda partial to the ol' Pepsi G so i ain't done with it yet. ;)


Holy moly, that is dramatic. Can't sleep........go out in the garage and create "Dramatic" :mrgreen:

Great modification results, you should do that more often :o
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DarenN
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Re: ramble about jets and potstands

Postby DarenN » Sun Feb 21, 2010 1:01 pm

just tinkering wrote:I take it that these test were done without pots as well?


you are correct, Jon.
the burn times would have been a lot longer with a pot closing down O2 input. i already know that, so i took it out of the equation. just a burner, free to do what burners do. :geek:
i feel that with proper sizing and jetting, the Pepsi G can be made to emulate the Trangia burner more closely. i'm working towards this end.

Daren......
"I'd rather be happy than right." Slartibartfast

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DarenN
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Re: ramble about jets and potstands

Postby DarenN » Wed Feb 24, 2010 10:24 pm

i built a 12 jet burner and ran through the same testing.
15ml Methyl Hydrate was burned in all tests.
each jet size times were averaged over three burns.

jet size - bloom time - total burn time:

.0315 - 0:45 - 4:46

.039 - 0:41.67 - 4:26.33

.046 - 0:37 - 4:04.33

.0625 - 0:37.67 - 3:46.33

i'm not going to abandon the Pepsi G just yet but the Ion is really starting to look like the better burner.
next i will build and test an 6-jet Pepsi G.

Daren.........
"I'd rather be happy than right." Slartibartfast


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