Turbine section design help (please)

[doctorklein]

Hi,

Some members of my team and I have posted on here many times in the past couple of months as progress on our turbine build has accelerated. Now we have a couple of questions regarding design choices for our turbine and combustion stage of the engine.

For context our engine is loosely based off of the KJ-66 for which we do not have full blueprints (if someone has these I would love to see them).

But anyways, we just finished machining our diffuser and want to begin work on the stator guide vane. What we don't know is how to determine the cross-sectional area of the stator guide vane based on our diffuser. Should we just go off of what the KJ-66 had? Is there a calculation we can do? If that calculation produces infeasible results how closely would we have to stick to it? Last, it would be great to hear what sorts of materials you all have used for stators / turbines in the past. 

Thanks so much!

[racket]

This book www.ebay.co.uk/itm/114801623350?hash=item1abab5c136:g:btcAAOSwKJVgmTDJ has plans for the KJ66 , or simply join the GTBA www.gtba.co.uk/

[doctorklein]

Hi perhaps I made a mistake:

I have been basing my engine off of the engine in this book: www.ebay.co.uk/itm/182992802331?epid=19046670515&hash=item2a9b38921b:g:pB0AAOSw6zheFftf which is the kamps micro turbine right? The problem has mainly been that we cannot follow the design in the book exactly due to machining limitations, but we don't have a robust enough understanding of the fluid mechanics/thermodynamics that govern the design to feel confident in just changing the design.

[racket]

Hi

Thomas' book is a very good book , I have an earlier Edition , but its very similar , if you are uncertain of something in the book just give me a reference to the page/subject and we can get it sorted .

There are some "rubbery" bits in the calcs , which are OK for his design but aren't once power levels are greater , but for a home build its fine .

Cheers
John

[doctorklein]

Hi John,



It's been a while! Since we last talked I've almost completed my build of the kamps microturbine. Right now the pieces that are left to go are the compressor cover and the diffuser.

Because I have access to a CNC mill I have opted to make the alternative diffuser blading seen in thomas's third edition of Jet Engines.



The problem is that the drawing for that diffuser is missing some dimensions, namely the blade thickness at the end.

I believe this dimension could be the angle in yellow or it could be the distance between A and B.






This dimension could also be a combination of the radius of the tapped holes in the blades and the amount of clearance between the M2 holes and the sides of the blade (In this case 0.3mm clearance around the 2mm tapped hole).






For reference, here is the diagram in the book:




Best,

Michael

[racket]

Hi Michael

I gather you need to know the thickness at the outflow end.

Its rather irrelevant as long as you have sufficient meat around the M2 thread , the 2.6mm width in the drawing at 42 mm radius, ...........you'd need to juggle the "centre" for the 63 and 90 mm radii curves , as long as the 63 mm radius meets the tangent at 21 degrees above it to align with the air angle

Cheers
John

[michalc]

Nov 14, 2021 3:24:46 GMT -5 doctorklein said:

It is an axial turbine design or radial ?  If it is axial design I strongly recommend  Saravanamutto, Rodgers, Cohen "Gas turbine theory".
The simplest axial design is 50% reaction design.
For a start in axial design NGV i would try alpha1 = 0-:-10 deg range, alpha2 = 60 deg measuring from axial direction. Real problem is not NGV but turbine rotor due "limited space".