RE: What size engine - A poll
 

[/quote]

Model Turbine engines have a long way to go before they reach the level of perfomance that can and has already been achieved in 4'' diameter sizes. I have seen compression ratios of 6:1 and 300N thrust at FSC of 0.02 g/N/s in KJ sized package, using ceramic NGV and turbine, 600N with 2000 deg EGT.
Mainly the compressors and diffusors are radically different from the current CFD ''optimised'' designs. Combustors are simple but also very different.
Andre Baird

[/quote]

Will this technology make its way into model turbines and at what price?

RE: What size engine - A poll
 

Some might and some probably won't. The only ceramic material I'm aware of that has the required strength to withstand the stresses of rotation is carbon-carbon. The same material that makes up the leading edges of the space shuttle. Really expensive stuff.

Supersonic compressors are neat but have their limitations in our use.
Some might

RE: What size engine - A poll
 

Enough said Gaspar, you nailed it. Will Jet Central carry something like that on the other side of the pond? Or is this solely a Jet-munts project?

RE: What size engine - A poll
 

I prefer the teeny ones
You dont see this engines as much as the big ones.

I build two 40rs engines ,they are 65mm o.d and i realy like them.
i think they are much more fun to build then kj66 type

RE: What size engine - A poll
 

I shoulda clued in when the turbine wheel was sitting on top of a manual for a Bandit. That makes it 9-10" in dia as it sticks off one edge of the page.

Turbines of any size are COOL! [8D]

RE: What size engine - A poll
 

A lot of reasearch has been done in the last 5 years which has turned conventional wisdom re compressor difussor design on its head. Some of it was known decades ago in the soviet block and has found its way into small missile engines. There is no reason why a reworked design with the technology we already use cannot produce 240N in a KJ size engine with close to half the fuel consumption. Its a question of know how. Add ceramics and youre talking 600N...
The truth is current compressors barely works as it is. CFD tools available to the public are not good enough to hint at this. Their flow predictions are just way wrong.
Andre

RE: What size engine - A poll
 

I've been tinkering with different diffuser designs and reading a lot of the published literature in the past couple of years.
I agree that there are some really nice innovations in impeller/diffuser designs.

The problem (for us) is the use of ceramics. The current trend for turbines is to use Silicone Nitride and hot press it under high pressure (Hot Isostatic Pressing). While the process itself is not terribly expensive when compared to vacuum casting Inconel the bare materials are still very expensive. Plus any FOD that enters the engine will instantly turn that expensive turbine to dust. All in all the technology has not yet matured to the point we can reliably use ceramic turbines. I'm tinkering with this on-and-off. I promise to tell if I hit on anything :)

As to the thrust figures - we're probably very close to the limit of what you can get in terms of thrust. 240N of thrust from a 70mm impeller will require almost 100% efficiency of the compressor stage. I doubt it's possible but I'd love to be proven wrong. Going to ceramics can increase thrust twofold. 600N from a Kj sized engine is probably not possible.


That's simply not true. I've seen results from OpenFOAM that rivals anything ANSYS can dish out. The real problem is setting up the problem correctly and analyzing the results correctly.

RE: What size engine - A poll
 

Erazz,
Its not a question of being proved wrong, its been done 15 years ago already. Ansys CFD gets it wrong too... New tools being develped right now are improving the situation but advances in laser velocitromy has divulged the true flow problems in non-axial compressors. While is is true that when the problem is set up incorrectly the best CFD fails, predicting initial conditions is very important. I know a lot about the subject, more than most small turbine builders, but it is nowhere near enough to form an opineon of what is possible and what not. So I rely on what has been done as a guide.
I am reminded of the NASA propultion enginners that refused to believe a specification for a rocket motor developed in the 60's in the USSR. When they observed it during tests exceeding the spec they realized they were 40 years behind... Many military /research rockets now use this motor under licence in the USA...
Andre Baird

RE: What size engine - A poll
 

Did you know that the internal of the JetCat P-200 actually is a copy of the legandary first generation AMT NL Olympus?? ;-)

RE: What size engine - A poll
 

Did they copy the reliability as well?

RE: What size engine - A poll
 

:)
Yeah, engineers get stubborn. Good thing I'm not an engineer! :D


BTW. Do you have any link or articles that deal with these new impellers and diffusers? I'd like to read about them.

RE: What size engine - A poll
 

No public info has been released AFAIK from the specific company. I do have the info but I could not release it since it is copyrighted.
I can say that the diffusor has no vanes as we know them. The compressor is mixed flow and has a lot of backsweep right from the inducer end already. It runs at 120K and has a press ratio of 6:1

RE: What size engine - A poll
 

Nothing beats the reliability of AMT NL turbines. ;-)