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Post by azwood on Mar 26, 2018 2:39:23 GMT -5
Hi OK , 5280 sq mms inducer area , 30% for Primary is 1585 sq mms , if you only intend to have a single row of holes , then you need them where a fuel spray would theoretically impact the wall , or if using vapouriser , where the outlets of them are and some others inbetween to produce turbulence , but we'll concentrate of a single row of 10 holes using 2/3rds of that 30% , the other 1/3rd for wall cooling/other things , so 1585/3 X 2 = 1056 sq mms , divide by our 10 holes = 105.6 sq mms per hole, divide by Pi = 33.6.45, square root = 5.8 mm radius , so 10 X 11.6 mm dia holes required . The other 1/3rd or 528 sq mms would normally be used in the flametube cap , some for swirl vanes surrounding the fuel spray nozzle and some for holes in the cap to keep it cool by keeping flames away from it . The Secondary holes at roughly mid point down the flametube will have a total of 1056 sq mms , but lets go for 15 holes as they don't need to penetrate as deep, so 70.4 sq mms/hole , div by Pi = 22.4 , sq root = 4.7 , so 15 X 9.4 mm dia holes , these can again be smaller is some of that 1056 sq mms is allotted to a row of small 2mm dia wall cooling between the Primary and Secondary rows , 2mm dia holes are roughly 3 sq mms a piece so if theres say 30 of them around the flametube we use up only ~100 sq mms , this would then bring our 15 main Secondary holes back to 63.7 sq mms each or 9 mm dia . The Tertiary holes at the lower parts of the flametube have 2640 sq mms to be divided amongst them , so if you have 10 holes at 264 sq mms each , or 18.3 mm dia Hope this helps Cheers John Thanks your a legend mate at least I know I will be done Wright now. Ok so have the ft done apart from one part I was not sure on you said 30 2mm cooling holes are taken from the secondary hole volume how many can I add in the primary zone and do I need to allow any between secondary and tursurey holes. |
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Post by racket on Mar 26, 2018 3:21:14 GMT -5
Hi
You can have a row of 2 mm holes between Secondary and Tertiary rows if you want.
The ~100 sq mms I deducted from your main Secondary hole allotment of 1056 sq mms for a row of 30 X 2 mm dia holes allows you to position that row of 2 mm holes midway between the line of Primary and Secondary holes.
If you want to add some 2 mm cooling holes in the Primary Zone then you'll need to deduct their area from the 1585 sq mms that was divided up between the various original Primary holes .
Its important to decide on how the allotted areas are going to be divided up before making the flametube , and stick to that decision , if we start adding holes or changing positions at a latter date it can upset the area divisions and potentially the operation of the flametube .
Cooling holes are only cooling holes , the flametube shouldn't fail quickly if they aren't provided , considering most of our engines are lucky to clock up 1 hour of use , just about any flametube will survive that , even a mid steel one .
Cheers
John
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Post by azwood on Mar 26, 2018 3:23:36 GMT -5
Hi You can have a row of 2 mm holes between Secondary and Tertiary rows if you want. The ~100 sq mms I deducted from your main Secondary hole allotment of 1056 sq mms for a row of 30 X 2 mm dia holes allows you to position that row of 2 mm holes midway between the line of Primary and Secondary holes. If you want to add some 2 mm cooling holes in the Primary Zone then you'll need to deduct their area from the 1585 sq mms that was divided up between the various original Primary holes . Its important to decide on how the allotted areas are going to be divided up before making the flametube , and stick to that decision , if we start adding holes or changing positions at a latter date it can upset the area divisions and potentially the operation of the flametube . Cooling holes are only cooling holes , the flametube shouldn't fail quickly if they aren't provided , considering most of our engines are lucky to clock up 1 hour of use , just about any flametube will survive that , even a mid steel one . Cheers John Thanks that's the way I thought you ment it great I'm on the wright track |
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Post by azwood on Mar 26, 2018 18:57:13 GMT -5
The length I have for the ft without the reducer cone is 420mm you said 350 is better right
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Post by racket on Mar 26, 2018 19:23:40 GMT -5
The 420 mm is probably better as it provides more dwell time , whilst the 350 mm would make for a more compact combustor , without "hands on " examination of your build its a bit hard to give recommendations , thats why Jetspecs was created
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Post by azwood on Mar 27, 2018 4:41:43 GMT -5
The 420 mm is probably better as it provides more dwell time , whilst the 350 mm would make for a more compact combustor , without "hands on " examination of your build its a bit hard to give recommendations , thats why Jetspecs was created Ok thanks I'll leave it how it is and see how things go I can always change it. |
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Post by azwood on Mar 27, 2018 20:34:12 GMT -5
Found a nice cutaway of a chamber  |
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Post by racket on Mar 27, 2018 21:38:15 GMT -5
thats an early one
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Post by azwood on Mar 27, 2018 21:40:36 GMT -5
Is that a Derwent style chamber.l really the old style engine's |
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Post by racket on Mar 27, 2018 23:20:06 GMT -5
Even earlier , maybe a Whittle unit , Power Jets W2/700..............something like that in one of my books
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Post by smithy1 on Mar 28, 2018 21:28:23 GMT -5
I think have a spare C20 "Bang box" floating around home somewhere...just needs some voltage, wiring and a spark plug...
I'll see if I can find it and see what can be done for you..
Smithy.
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Post by stoffe64 on Mar 29, 2018 6:56:16 GMT -5
 I have such c20 box,they bang quite good, i can assure you! |
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Post by azwood on Mar 29, 2018 20:09:49 GMT -5
A nice little unit
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Post by azwood on Mar 30, 2018 1:35:53 GMT -5
I have such c20 box,they bang quite good, i can assure you! What's one of those worth |
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Post by azwood on Mar 30, 2018 1:37:17 GMT -5
Been looking at electric oil pumps online can't find one that's ment for continuous use
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