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Post by racket on Feb 20, 2018 15:40:38 GMT -5
Hi
The cross sectional area of the sticks need to be ~10% of the inducer area, so with a 76 mm inducer thats 10% of 4536 sq mms so 453 sq mms , div by 4 = ~113 sq mms/stick or 12 mm ID , so yep , a bit small at 10mm , also 1.5mm WT is getting a tad thick , if you can source 1.2mm WT its better and can still be easily welded .
Heating surface of all sticks needs to be ~6 times inducer area , so 27,216 sq mms , if 15 mm OD , then a total of 577 mm of stick length or 144/stick if 4 of , so legs maybe 75, 40, 50 mm , the mitered corners need to be accounted for in the area calcs
Cheers John
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greazy
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Post by greazy on Feb 20, 2018 16:06:37 GMT -5
ok the compressor is actually only 70.5 mm I'm not sure how to change the topic name. 70.5 = 3903mm2 10% 390mm2 ÷ 4 = 97.9 so 11/12 id is the go i may bore out some solid bar to make some thin walled tubing
dose the bellmouthing at the entry increase flow / speed of the evap sticks at all. thereby reducing the nessissary stick size?
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greazy
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Post by greazy on Feb 20, 2018 16:08:10 GMT -5
the other option is 5 sticks at 10mm id or will that be too crowded in the flametube
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Post by racket on Feb 20, 2018 16:21:52 GMT -5
Maybe I'd better check with you about your latest drawing , are these sticks , straight or walking stick types , straight ones like Anders and I use in our micro type engines won't be much use if they're discharging towards the turbine end of the flametube as there won't be any flames to heat them , walking stick types are OK but you'll probably find it might be difficult fitting them into the space available with the positioning you have unless they're "tangentially??" angled around each other whilst still allowing the entry to be where you have them .
The bellmouthing on my "micro" tubes is there to stop them falling into the combustion space rather than improving inflow , the frictional drag through the tubing might be more of a controlling influence , don't really know , haven't thought about it ..............the surface area and heat transfer rate is probably more important a consideration than rigidly sticking to that 10% figure
Cheers John
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Post by racket on Feb 20, 2018 16:22:44 GMT -5
5 X 10 mm OK
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greazy
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Post by greazy on Feb 20, 2018 16:32:39 GMT -5
yes they will be walking sticks ( 180° bend outlet facing the start of the flametube ) i just drew up the fusion program to get my head around the penetrations.
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greazy
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Post by greazy on Feb 20, 2018 16:35:59 GMT -5
ok ill have a play with 5 bent tubes and see how they fit. and ill also look for some thinner tubing in the meantime
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greazy
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Post by greazy on Feb 23, 2018 9:08:29 GMT -5
end cap from 3mm ss that a friend cut a few months back on his home built cnc plazma I cleaned it up a bit then tacked the lid and ring together and drilled out the holes to 10.5mm . i then welded 10mm stainless nuts behind the ring and also added 2 5mm rod locating pins. it may not seem necissary but the last engine i made i spent ages trying to line up the holes wich are never perfect in any other orientation. during the the test and tune phaze that plate came off about 40 times at least so this is well worth it for the hour or so work it took. i have aslo ordered some 12.7mm .9mm thick tube for the vaporizers 5 of should give me 11.5% or so of the inducer area and its nice and thin so thats a bonus. hopefully i have more to update shortly ryan
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greazy
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Post by greazy on Feb 25, 2018 17:19:59 GMT -5
i picked up my ss evap tubes on sat and decided to try a right radius bend instrad of miter cuts and welding back together for the walking sticks. i had many failed attempts i tried heating and bending. fail pack with sand and cap ends. fail (probably the best result) internal bending spring. fail afyer all this dissapointment i decided to make a tool up. i have a half inch mill bit the same size as the tube and milled perfect grooves in the blanks and also made a die for supporting rhe straight part of the stock. ill mount these all to a base today and see how it goes. if this fails i may make a bullet for the internal part like a mandrel bender but it may be too much work by that point so there is always the mitrr cut and weld option. ryan
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Post by racket on Feb 25, 2018 17:42:48 GMT -5
The mitred joint product probably has a better performance than a bent tube , the right angle corners makes the fuel spread out and evaporate not only from the wall heat but also the more intense air turbulence , whereas a bent tube will most likely simply force the fuel to the "outside" of the bend and theres minimal air turbulence in a cylindrical tube even if curved .
Just some thoughts
Cheers John
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greazy
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Post by greazy on Feb 26, 2018 7:14:43 GMT -5
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greazy
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Post by greazy on Feb 26, 2018 18:52:49 GMT -5
i have drawn a mockup of where the walking sticks below outlets into the c/c are in the center of the five circles and the black pen are my options of where to start the vaporizers from. i feel like option 3 would be best leaving the start of the sticks in the hot middle where there is no real chance cool air can affect the vaporizers but it may be over crowded. any thoughts???
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greazy
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Post by greazy on Feb 26, 2018 19:02:56 GMT -5
here is a bit better mockup with the black dots actual size of vaporizers dotted circle around them the spray area apon exhausting from tube and the number options for the inlets
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Post by racket on Feb 26, 2018 22:01:12 GMT -5
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greazy
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Post by greazy on Feb 26, 2018 23:55:30 GMT -5
ok thanks. the pic below is how i will lay them out black holes represent outlets one ladt question before i make the vaporizers. how much room should i leave between the outlets and the back plate? i was going to leave about 20 mm is this enough room or should i go with a bigger gap?
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