Ceramics for engine exhaust

[BillClark]

A need in my particular field of interest exists for a tuned pipe/muffler (for IC engines) that has very low thermal conductivity, mild to moderate strength, good thermal tolerance (1600deg.F) and be relativly easy to manufacture. Typically aluminum, steels or carbon fiber w/ a BMI matrix are used. I was thinking a Ceramic material (pourable, injectable?), reinforced or not might be worth exploring but soon realized the technology is complex (for me). so my question is am I barking up the right tree here. are there castable ceramics availabe that may work in this application and are available to the average person. thanks

 

[TVP]

Exhausts for high performance racing racing engines (F1, etc.) are typically titanium or nickel alloys, which are relatively low thermal conductivity, that are subsequently coated with a ceramic layer. I doubt that castable ceramics can achieve the necessary dimensional accuracy and mechanical properties, primarily fracture toughness and fatigue strength under vibration/high frequency excitation.

 

[BillClark]

My concern was the toughness too. I think they are producing turbine housings out of the stuff. Not a piston engine screaming into it w/ high frequency, supersonic waves but still a harsh environment

 

[EdStainless]

Look at using very thin metal. Stick with Ti or a ferritic stainless (low thermal expansion, no Al or austenitic SS). Then look at ceramic coatings. These are porous so that they are not too brittle.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[TVP]

BC,

If I understood your last post correctly, you are likely referring to a housing that has been made using injection molding technology, similar to metal injection molding. While this may be suitable for some types of parts, I would not imagine a relatively "fluffy" part like an exhaust manifold would be suitable. Smaller, more discrete parts with good load paths, no deflection, etc.

 

[BillClark]

Ed, I was thinking along those lines too.
TVP, to offer a better understanding an example would be what resembles a baseball bat.Hollow,30" long, 2.5-3" diameter w/ taper on one or both ends. A steel pipe about 12" long is between this an engine. Application is weight sensitive (less than one pound req) but equally important would be the ability to retain heat (not radiate). the existing carbon/BMI designs weight 6-7oz and do a very good job of not radiating heat (dumping gases through outlet at rear)but are right on the max service temp threshold. The market is relatively small so manufacturing cost have to be low (what’s new). I have the ability to produce tooling inhouse if I can find a suitable material. I appreciate you folks taking your time to think about this

 

[boo1]

Goodrich developed FyreRoc for the General Dynamics, Expeditionary Fighting Vehicle (EFV) turbine exhaust.

FyreRoc is a matrix of polyacrylonitrile carbon fiber and glass/ceramic epoxy resin which can be used up to 630 degrees C.

 

[BillClark]

Thanks Boo, I will research that. I did find several putty/adhesive materials that might be used as a matrix with a braided ceramic sleeve material as a reinforcement. Maybe it can be sufficiently reduced for impregnation. I am waiting to here back from this company

http://www.cotronics.com/vo/cotr/ca_putties.htm

We'll see what they have to say about it. Probabley not ideally suited but then again.....

 

[MikeHalloran]

Jet-Hot and/or header wrap tape won't work?



Mike Halloran
Pembroke Pines, FL, USA

 

[BillClark]

Mike, I'm sure that would work. I am intersted in creating a marketable product though. The market a product such as this would be presented would respond favorably to things like "Aerospace Carbon/Ceramic Tuned Pipe" (a little fluff,yes)and if we can end up decreasing radiated heat, noise, and keep the weight comparable we will have a winner. FYI, one or two of these would be used in a $8,000+, 120"wingspan, radio controlled aerobatic airplane with most of the owners having multiple planes.

 

[MikeHalloran]

I used to have a smoking pipe called 'The Pipe', which was made of a material the manufacturer called 'pyrolitic graphite'.

It was not remarkably lighter or heavier than briar. It didn't conduct much heat.

It lasted 30 years before yet another collision with a floor revealed that it was actually double walled and hollow.
I have no idea how it was made.
I haven't seen one in years. I guess its lifecycle was sort of like that of jetways; the initial production run completely saturated the market, and the product was durable enough that replacements couldn't keep the company alive.

I have the impression that the material was also used to make rocket nozzles. Maybe you can find someone who can make expansion chambers from it.



Mike Halloran
Pembroke Pines, FL, USA

 

[davefitz]

possible application for geoplymer technology. Most geopolymers are stable to over 1000 C ( 1832 F). Fatigue strength, fracture toughness can be greatly improved by the addition of microfibers . Need to consult with a materical science engineer familiar with geopolymners to get it right the first time.