Gas Turbine Ceramic Bearings

Nice idea.. Reviie the Chrysler Turbine engine.

It runs on 5% alcohol and the patents are spent and readily available!

google Chrysler Turbine and perfect their design...

JL Mealer

America's next major Automaker

http://mealercompanies.com

Hello Mr. Mealer.

The Chrysler turbine relied on internal heat exchangers, that's not exactly what I'm doing.

Still find your concept (Mealer car) really interesting.

Thanks

I wish you luck and since you can read my typos without comment, you are en route to success with your product. Provided you don't let vane warpage slide like you did for my typos.

Good luck and have fun doing what you're doing.

JL Mealer
Mealer Companies

http://mealercompanies.com

I may be a bit naieve here and nit picky, but does this piece really weigh less than 2 grams?

However that issue aside, I remember one of my Material lecturers talking about a material called Partially Stabalised Zirconia. A ceramic for most parts, but is about as tough as steel. I don't know the operation temp, but i'm certain that it's coefficient of thermal expansion would be far less than most metals, making it more suitable for high temp environment.

Good luck with the research.

With all the due respect.

1.293 grams it's almost 1.3 Kilograms or = to 2.850 pounds.

Thanks

No 1.293 grams is 1.293/1000 kilograms that is .00285 pounds. Spend some time with a basic textbook before you try to re-invent the gas turbine.

The point was taken not the comma

It depends where you live! In the United States, a "." within a number is called a "decimal point", and separates the whole number from the fractional part, so 1.293 grams means one gram and 293/1000 of a gram. A "," is used to separate sets of three digits within a whole number, so 1,293 means one thousand two hundred and ninety-three.

I don't know what they call it, but in some other places the meanings of "." and "," are reversed, so 1.293 grams means means one thousand two hundred and ninety-three grams, and 1,293 means one gram and 293/1000 of a gram.

did you notice that he gave the rpms as 30.000 (with a period, not a comma)?

Along the same lines, a billion means very different things in different countries: in the USA, a billion means 1 followed by 9 zeroes. in many other countries, a billion means 1 followed by 12 zeroes! The latter really makes more sense, as bi- means 2. The bi- of billion in other countries means million twice. In those places, a billion is a million milion!

The place is Toronto. Canada.

Why you people quibble on a trivial matter? It just gives away that you have no useful idea to add to this discussion, do you?

Go and address the real issue instead otherwise hold your breath!

Like the other poster said "the point was taken not the decimal" very well put I must say.

Isti, it may seem a trivial matter, but is is a very important problem. Choosing to use commas and decimal points incorrectly simply because your country or region wants to be different will lead to much pain and heartache (not to mention costs and scrapping of parts). Periods used as decimal points and commas used as separators are the world engineering standard, it is standardized in both ASME Y14.5M as well as numerous ISO standards, refusing to follow the standard will land your arse in deep caca in very short order.

The question raised about the bearing that is more important than the misplace of the period(.)

I tend to agree that it is important at times to mark down things accurately but not now. Yet the others seemingly just went on about it even after the OP quickly acknowledged the error corrected the b...period

Was pretty clear that it was just an honest mistake and the 1.2+gram would have been too light even for a toy part of a type, don't you think?

And the OP is still waiting for the RELEVANT answer period

ciao, bello

Hello there.

You would say 1 angular bearing or two in tandem?

The shaft diameter is 25 mm.

Outer and inner diameter? Please.

"Use the standard aircraft bearing fit modified by the difference in the expansion coefficients of steel and silicon nitride so that you have the needed fit at the operating temperature."

I do have a very limited knowledge of CNC and such. Could you please be specific to the point I will be able to explain it to my CNC person?

Thanks for the reply.

GA Guest. Not a great answer because the questioner has left out some very important information that the guys from SKF will want to know. So a great answer is not possible at this time.

Specifically: what are your radial and axial loads and what will be the operating temperatures of the bearings?

Your axial loads will depend on the fluid loads acting on the turbine. I don't know enough about turbine technology to be able to say radial fluid loads will be significant or not. But I will tell you that balance of the rotor will have to be very good or the radial loads resulting will destroy any antifriction bearing you choose if not the entire mechanism at the rpm's you are talking about.

I'm not going to tell you how to calculate unbalance loads because you absolutely will need to be very familiar with this calculation. So you might as well dig into your books and learn about it before you waste any resources on building a new shaft to mount that rotor.

Ed Weldon

needle bearings, or more specifically tapered roller bearings will distribute the load within the bearing better than a roller or even double roller bearing set. At a lower per unit cost usually.

You might want to look into what is called "Fluid Bearings" wiki: http://en.wikipedia.org/wiki/Fluid_bearing Check out the NASA spec sheet in the references for specific specs. They are sometimes called air bearings. They work well over 2000 rpm, relying on a thin film of air between the shaft and the special bearing. There have been improvements in the last few years; I think they are into Gen 3 or 4 by now. Another way to look at the problem is with magnetic bearings. Many high-speed flywheels use this technology. Here is one example company: http://www.waukbearing.com/fluid_film_bearings.html

Hello.

I've looked at this same options in the past, it's simply prohibitivly expensive to go either ways.

Thanks.

Thank you.

may i add :

too expensive??

save to buy the best once, the accident you prevent may be your own.

when blades seperate from the hubs.. not much stops `em..

Ceramic bearings do not handle large temperature changes well since they have virtually NO elastic region, they cannot handle differences in CTE. I am in agreement with the previous poster that conventional metallic bearings are probably better for this application. I would also suggest that putting the turbine disk on it's side supported by the blade tips as you show it is probably bad practice.

Hi,

steel rings and steel or silicon-nitride is the only useful and available possibility.

I would stay with the original maximum speed and add a shield to protect from may be disintegrating blades.

You will get advice where you may buy the bearings.

RHABE

Boy, and I thought I had issues at 10,000 to 12,000 RPM for the disc turbine I'm designing!

That type of rotor by design is going to have some axial load, since the hot gas hits it from one side and is converted into rotation. Also, whatever gearing you use will likely generate radial loads.

I am thinking of using angular contact ball bearings for my turbine, since they accept both radial and axial loads. According to this they will operate at higher speeds with primarily axial loads: http://www.bearingstrade.com/angular-contact-ball-bearings.html

When you test this critter, make sure you know the design max RPM, and have a speed readout of some sort on the output shaft so you can monitor RPM. Buy (or make) bearings that will meet your design max RPM plus a "fudge factor". I'm planning on using pressurized oil lubrication, to keep the bearings cool. For a gas turbine, you will need a special high-temperature oil designed for turbines.

BTW, you have the turbine, what are you using for the compressor?

Hello.

There's no gears for the time being, it's just a proof of concept engine.

I will have a oil pump pumping into a custom ball bearing casing, but it's not high pressure, it will be more like an oil mist system type deal.

Will have an angular contact ball bearing in tandem with an high speed "regular" type ball bearing.

The compressor it's where i'm making it different than the rest, so for the time being I do not feel confortable talking about it since it has not been tested and could be heither major failure or breakthrough, it all remains to be seen.

Thanks for the imput.

Just as long as that "breakthrough" isn't the turbine casing being broken through....

You are such a miserable person.

I'm miserable because I don't want you to kill yourself or others?

Ok, I can live with that. It's your neck, not mine.

It's not as if hundreds of thousands of very smart people have been working on the problem for 60 some odd years or anything....

Rhabe -- Lots of good stuff in your answer #33. I appreciate your tip on the latest edition of Harris and Kotsalas.

http://www.amazon.com/Rolling-Bearing-Analysis-Fifth-Set/dp/0849381673

I've been out of this particular game for some years now. Not sure I have the bandwidth to wade through this latest edition; but it is tempting.

I'm going to throw out some comments here; but I need to state a disclaimer first. I don't have any engineering experience in the gas or even the steam turbine world. I do have a lot of respect for the level of engineering that has made these technologies an everyday reality. So what I say here must be judged as general in nature.

I think we'd agree that this field of technology (gas turbines) has a substantial amount of "art" that requires a practitioner to be well versed in both at the theoretical and practical levels. But for the "lone wolf" inventor trying only to work at the proof of concept level the learning of all that is needed build a fully operational prototype can be an impediment.

To me the first order of business here is to understand the loads and speeds involved and then select a suitable angular contact bearing spindle setup to handle those conditions. I would pay a lot of attention to housing design to maintain accuracy of fits and alignment at the temperatures involved as well as the method of lubrication and cooling. But the important point here is that this is a performance test model were talking about. It doesn't have to live for thousands of hours. It does need to stay together while enough good data is collected to prove the concept in question.

And the net power output does need to be measured with some accuracy. That means there cannot be mechanical losses in the test spindle that are unpredictable or are of such a magnitude that they make credible readings of thermodynamic power output impossible. If the test rig requires a highly sophisticated spindle requiring design and construction considerations that you suggest then the experimenter will be well advised to prepare his equipment accordingly. To me the real issue may be the need to minimize energy losses caused by mechanical vibrations in the test setup from machining inaccuracies and rotor inbalances.

Am I on the right track here?

Ed Weldon ........PS....don't forget that 100,000 ft lbs of energy is like a 5 ton truck dropping 10 feet to the ground.

Hi E.W.,

I agree totally, same as you, no experience with turbines but with turbo-molecular pumps.

RHABE

Good luck on your innovative compressor design.

Don't get discouraged- remember, when the Wright Brothers were testing their Flyer at Kitty Hawk with their own money, Langley was crashing government-funded planes into the Potomac.

Hello.

Thanks everyone for their replies in particular to Ed Weldon, RAHBE and Mark Stockman. Yes you too and you know who you are ;) You made me think ... it's all I can say.

Would one angular contact bearing suffice for the turbine wheel assembly? Should I use 2 instead? RHABE please answer this one.

Since my twenties, that I've been cultivating myself on what regards this amazing engine type, the gas turbine. Finally I decided to turn into practice whatever I've observed and think it's possible to be done.

The turbine wheel it's whatever turbine I could find on e-bay to purchase (there's not a lot to choose from, and they all come with no paperwork.)

I will have professional CNC people helping to put my project together, they will manufacture and assemble the whole thing, yes safety is paramount. Don't want this to be my last project. I am aware of the so many things that could go wrong in a split second.

RHABE is there any way I could send you drawings for you to comment on?

Would like to show you the drawings I will be doing for the shaft and posterior manufacture of the same.

The basic layout of my turbine wheel assembly will be:

1 (or two?) angular contact bearings on a 20 mm appropriate quality steel shaft. The bearing case it's CNC cut. Lubrication via a adjustable flow micro oil pump. (The idea here it's to supply just enough oil so that I have a oil mist going exactly where it's needed in the bearings race rather than an oil bath. Oil to be cooled to requirements.

Still don't know about expected RPMs since it's a novel design and I have no info on how fast the turbine was turning when part of the original setup.

There's risks as we all know, I have to admit that there's a lot of crucial data that I simply have no acess.

I am starting right here with a good turbine wheel, possible bearings and set-up, some advice from my friends and the will to make it happen.

Thank you so much everyone.

See you all around here.

Hi,

if you click on my name in any of my posts you will my CR4 profile and a link to my website and there my email-address.

"Would one angular contact bearing suffice for the turbine wheel assembly?"

This can only be answered if you have a good guess of loads and speed and power-loss in the bearing and lubrication. Are you above (certainly) the first critical speed? Do you have damping at critical speed?

"Just enough oil" how do you detect this condition - pretty difficult. Oil mist for bearing lubrication is usually too much, but one of the best approaches you can buy from the ball-bearing companies. This will spray by compressed air a lot of oil into air, most of it hits a plate that is perpendicular to spray, the fine droplets that can avoid being caught by the plate are carried with the air through the bearings. Some is deposited there. If you are content with a short lifetime you can go to non-permanent oil flow. Reliable bearings have to be disassembled prior to use, cleaned and checked for cleanliness and thus wettability by oil.

RHABE

Here's a site I found on a quick web search for a homebrew digital non-contact tachometer: http://ikalogic.com/d_tach.php Might need to get one of these for myself!

I'm working on steam turbines myself (see "disc design for boundary layer turbine" thread on this forum) but Tesla's boundary layer turbine will work with just about anything. Cheap to built, robust, power dense, but we mortals have trouble hitting his claimed efficencies.

Hello Mark.

Thanks for the tip. Yes I'm going to need one.

Since we have a similar task at hands, I would like to continue to exchange mail with you.

manuelbicudo@hotmail.com

Thanks

Unfortunately, I didn't bookmark it, but a recent "Global Spec" had info on ceramic bearings based on partially stabilized zirconia.

These has sufficient elasticity to allow them to be a press fit. Most ceramic bearings won't tolerate this.

Sorry I can't be more specific.

Hi,

I believe the wheel you have is an Allison C30 second stage wheel.

I would have gone with gas bearings or magnetic bearings.

You could try active magnetic bearing, or even a "passive" electrodynamic magnetic bearing. The latter relies upon eddy currents set up by small displacements of the rotor (attached to the ring magnets) within a ring of copper or aluminum. The ring will need to extend the length of the magnets plus a bit. Will still require a high speed compatible thrust bearing for axial load. Significant radial loads can be accommodated, by 50 psi x shaft cross-sectional area.

There are also air stone bearings, and since this is compressor, or power wheel, there should be the availability of "bypass" air to supply the air stone surrounding the rotating shaft. These can handle radial load only, so you have to supply additional thrust bearing.

Silicone nitride bearings require zero lubrication, just a clean environment, typically. One does not contact silicon nitride with high temperature steam or game over. Relatively cool bypass air should prevent problem with gas turbine exhaust corroding the silicon nitride balls. Speed limit has to be checked with the OEM, since it varies from 25,000 rpm on smaller (skateboard) bearings to the larger ones.

Check with the manufacturer on the critical whirl speeds of your assembly.

I once had a centrifugal air compressor which I wanted to run at 3000 rpm instead of 3600 (this was the speed of the input shaft to the bull gear which spun the rotors much faster)

On checking with the manufacturer I found a critical speed around 3000 rpm so had to use a gearbox to speed up to 3600.

The point is that dangerous resonances can occur at a variety of speeds so checking for them at your top speed may not be good enough as trouble can arise on speed up and slow down, especially if you don't pass through the critical speeds quickly enough.

Good luck

Actually, that is a key point, and highly valid. Thank you for reminding us of that.