DIY Gas Turbine Blades: Can I Make Them Using Ceramic and Carbon Fiber?

[kjjohn]

I have been researching DIY gas turbines lately, and I have concluded that I want to make one. My only issue is that all amateur designs I have seen use turbochargers. I would like to see an axial, multi-stage compressor/turbine design. Obviously this would require one to fabricate the blades yourself, but I believe it can be done. In fact, I have thought of an idea that may work, but I'm no expert, so I would like some more input. My idea is that each blade would be made by casting it out of a 2-part ceramic casting compound, specifically one designed to withstand high-temperatures once cured. This way, you would be able to form the blade to whatever shape you wanted without high-temperature metal casting. Next, the ceramic blade would be layered in carbon fiber/resin layers to increase its tensile strength. I believe my idea would work, given the fact that the ceramics can withstand nearly 4000 degrees (Fahrenheit) in some cases, and the strength of hardened carbon fiber. However, my only concern is that the high temperatures in the engine may cause the epoxy in the carbon fiber to break down. Would this idea work?

 

[mgb_phys]

carbon fibre - being made of carbon and glue is not known for it's fire-proofness.
The difficulty with ceramic blades has always been their brittleness - a small crack in a metal takes time to spread and can be caught by inspections, while a crack in a ceramic spreads incredibly quickly. Think of cutting glass with a diamond wheel - you make an almost invisible scratch in the glass and can snap it easily

 

[kjjohn]

That was another problem I neglected to mention. Although there is a possibility of this, would it be safe to use? I have been reading up on ceramic turbine parts research, and I know that ceramics are being developed that are design to eliminate this problem, however, they probably won't be available as a casting compound for a while.

 

[mgb_phys]

People have tried CF turbine blades, Rolls-Royce went bust trying to develop one for the RB211

 

[minger]

Another big problem with ceramic blades is connection to the shaft. Typically the shafts are metal, and the rotors can be blisks, but the thermal conductivity between the two makes the connection difficult.

You must understand that at those high temperatures using different materials makes things very difficult.

 

[Averagesupernova]

I recall seeing somewhere on the web that someone built a homemade turboshaft. They started with a conventional turbo charger and built the power turbine by jigging round tubing in such a way to cut it precisely to form the blades. I don't recall how it was balanced after assembly but the description was VERY detailed. I think the power turbine only spun up to about 20,000 RPM which compared to the rest of a conventional turbo charger is quite slow. If I were to mess around with homemade gas turbines and wanted to fab my own turbine I would try to build the turboshaft. After that was complete I would most likely be satisfied. Building things as a hobbiest that spin really really fast with really really tight tolerances while running really really hot requires a lot of patience. I am sure there will be failures.

 

[kjjohn]

That was Don Giandomenico. I have read his entire website in detail. He did produce a turboshaft engine in way described above, however, it still used a turbocharger. I believe the turbine was not even stainless steel, and he balanced it by simply drilling holes in the hub until it no longer vibrated. He achieved around 6 horsepower. I believe he could achieve much higher output with multiple compressor stages, and even multiple turbine stages possibly. Obviously turbines welded together from sections of pipe are not optimized for efficiency, but it certainly worked, and seemed to hold together.

 

[xxChrisxx]

The word 'homemade' and any sort of turbomachinery, especially high speed like a gas turbine or turbocharger REALLY shouldn't be mixed.

Unless of course you have a full machine shop with precision measuring equipment in your home.

 

[zfolwick]

kjjohn- I have been thinking about this as well. There's numerous tin-can versions out there, but none of them work to produce any thrust to my knowledge; and all of them overheat.

I believe I may have figured a way to form the blades, but the connection with the shaft, as well as understanding the friction forces involved will take some time. If you'd like to collaborate on this, PM me. We may be able to combine brainpower and manufacturing.

My understanding of a Turbofan (what I'd like to build) is that

1) the turbines drive the compressors and the turbofan blade(s), and the turbofan provides around 80% of the thrust of the engine.

2) the engine functions best when the combustion chamber is at room temperature.

3) gearing is going to be a *****.

 

[mugaliens]

I have been researching DIY gas turbines lately, and I have concluded that I want to make one. My only issue is that all amateur designs I have seen use turbochargers. I would like to see an axial, multi-stage compressor/turbine design. Obviously this would require one to fabricate the blades yourself, but I believe it can be done.

Same here. In fact, you could use aluminum foil-covered wood, so long as you kept the temps and pressures low enough. I'm sure you've seen the candle-driven Christmas "turbines..." Of course they don't have much power except to turn the little hand-painted wood angles...

In fact, I have thought of an idea that may work, but I'm no expert, so I would like some more input. My idea is that each blade would be made by casting it out of a 2-part ceramic casting compound, specifically one designed to withstand high-temperatures once cured. This way, you would be able to form the blade to whatever shape you wanted without high-temperature metal casting.

Have you considered lost-wax processing? It's somewhat of a misnomer that modern blades are made of ceramic, though they do possesses ceramic coatings and certain internal components. Most of the blades these days are nickel-based superalloys.

But as I mentioned before, if you'd like to use steel, it'll work. You just can't use nearly the temps or pressures, but hey - the 707 had steel engines for years. In fact, they used to clean carbon scoring from them by shoveling walnut shells into them. Plus, you can machine steel fairly easily, so for a DIY project, it's a fairly good choice.

Next, the ceramic blade...

Not really. Ceramic is used as a form, but it's chemically removed, leaving a hollow blade.

I know the idea of coupling old turbochargers seems like a cop-out, but I've seen 'em used for everything from go-karts to make-shift turboprops as well as outright compressors for R/C aircraft.