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Post by stoffe64 on May 22, 2014 11:12:06 GMT -5
Hello everyone,i have a question for you experienced builders, what happens to the hot gasses exciting the round flametube when it enters the rectangular turbine inlet duct?, flametube and the smallest section of the turbine inlet duct-in other words the long side and the short side have the same dimensions but the corners of the rectangular turbine inlet duct will be a tad bigger,this part i planned to make an adapter plate for,with the rectangular shape with a hole suitable to fit the flametube in.
Now i started to think,what happens under that adapter plate when the hot gasses enters thrue it,would it swirl around like in a dump style afterburner?....that is my concern,anyone in here have any input on this?
Thanks/stephan
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Post by Johansson on May 22, 2014 16:07:14 GMT -5
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Post by finiteparts on May 22, 2014 20:43:45 GMT -5
Stephan,
I think the general answer to you question is...yes, the flow will likely create a region of swirl downstream of the plate similar to the dump expansion used in some afterburners. This will of course be a frictional/viscous loss to the flow kinetic energy, but since the flow in the turbine scroll housing is accelerating, it will probably not be a big issue...since accelerating flows tend to inhibit the boundary layer flows from growing larger. If you have steps in the compressor side, that is a flow that is decelerating, it is much more of an issue because in decelerating flows the boundary layers will grow larger till the flow separates from the surface and creates stalled flow regions.
So, why don't you make the combustor area larger than the turbine housing inlet and grind the housing inlet till it "matches" the combustor exit area. Think of it like the port matching that people do on high performance reciprocating engines.
~ Chris
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Post by stoffe64 on May 23, 2014 5:29:27 GMT -5
Anders...im surprised over your answer to my question, i think i would like to get more answer than just a photo of a mushroom cloud from a nuclear explosion,you being an member with expert status and all that. /stephan |
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Post by stoffe64 on May 23, 2014 5:33:18 GMT -5
Stephan, I think the general answer to you question is...yes, the flow will likely create a region of swirl downstream of the plate similar to the dump expansion used in some afterburners. This will of course be a frictional/viscous loss to the flow kinetic energy, but since the flow in the turbine scroll housing is accelerating, it will probably not be a big issue since accelerating flows tend to the boundary layer flows from growing larger. If you have steps in the compressor side, that is a flow that is decelerating, it is much more of an issue because in decelerating flows the boundary layers will grow larger till the flow separates from the surface and creates stalled flow regions. So, why don't you make the combustor area larger than the turbine housing inlet and grind the housing inlet till it "matches" the combustor exit area. Think of it like the port matching that people do on high performance reciprocating engines. ~ Chris Hello Chris,thank you very much for your explaining about the gas flows, now i understand that it wouldnt funktion so good,then i must solve that somehow, not sure how though. Cheers/stephan |
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Post by Johansson on May 23, 2014 6:50:01 GMT -5
Anders...im surprised over your answer to my question, i think i would like to get more answer than just a photo of a mushroom cloud from a nuclear explosion,you being an member with expert status and all that. /stephan It was a joke.  |
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Post by turbochris on May 23, 2014 7:39:24 GMT -5
grind the entrance as round as you can and then make a transition piece to take care of the rest.
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Post by stoffe64 on May 23, 2014 13:26:58 GMT -5
Anders...im surprised over your answer to my question, i think i would like to get more answer than just a photo of a mushroom cloud from a nuclear explosion,you being an member with expert status and all that. /stephan It was a joke. ok....i understand I know that i dont have your skills nor the kind of Equipment either,im fighting to get this engineproject together with limited resourses but anyway a tad better than a redneck Engine, this involves Stainless parts and my skills with metal work is very limited and Stainless is tough, finally i started to Think about making this rectangular thing because that was the way i suceeded to make paper templates so it fitted turbine inlet. you are a true expert Anders and im jellous of your work! |
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Post by enginewhisperer on May 23, 2014 18:52:02 GMT -5
to be fair, a contained mushroom cloud is pretty much what happens when gas flows through a stepped pipe |
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Post by stoffe64 on May 24, 2014 7:44:50 GMT -5
ok...yes,like Chris said....and as i suspected, an dump expansion afterburner scenario in the turbine inlet duct, i would have come up with something against that then!
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Post by finiteparts on May 24, 2014 11:18:46 GMT -5
Stephan,
Just a follow up comment...while it will cause a loss in efficiency due to the flow disturbance, it shouldn't be a major issue in the operation of the engine. If your tools are limited and your major goal is to produce a working engine, I don't think having a step in the turbine housing entrance is a big deal.
Only if you were trying to make the engine as efficient as possible would it become important. Now, if you can make the outlet of the combustion chamber larger than inlet to the turbine housing, you can grind the turbine housing inlet to make a better transition.
~ Chris
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Post by stoffe64 on May 24, 2014 15:07:30 GMT -5
Hello Chris thanks for your help here,i think i understand what you mean ,i guess to fond out you have to build and try.
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Post by stoffe64 on May 24, 2014 15:14:15 GMT -5
grind the entrance as round as you can and then make a transition piece to take care of the rest. Thank you Chris ,you are One hell of a Good builder as well, thanks mate! |
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miuge
Veteran Member
Joined: March 2014
Posts: 200 
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Post by miuge on May 24, 2014 15:19:17 GMT -5
Build and try is a good way to start! I think that the flametube itself and air inlet are in more significant role which effect to the combustion process.. Everything what happens after that would only have effect to efficiency like Chris said |
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Post by stoffe64 on May 25, 2014 1:05:17 GMT -5
Build and try is a good way to start! I think that the flametube itself and air inlet are in more significant role which effect to the combustion process.. Everything what happens after that would only have effect to efficiency like Chris said Thank you Magnus for your input here, really appreciated ,i roll try to take a photo and post when its possible! Cheers/Stephan. |
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