Ceramic chamber coatings.

[Capt.Crash'n'Burn]

Have ceramic chamber coating been extensively tested in aviation engines?

Are they certified for use in certified aircraft?

Are there noticeable improvements in cylinder head temps and fuel burn rates?

 

[gismo]

Have ceramic chamber coating been extensively tested in aviation engines?

Are they certified for use in certified aircraft?

Are there noticeable improvements in cylinder head temps and fuel burn rates?

What "chamber" are you talking about? If you meant cylinder, various attempts have been made to incorporate ceramics into the steel bore but AFaIK the only successful approach is CermiNil which combines the ceramic material with nickel and I don't believe any engine manufacturer offers that (aftermarket only).

 

[bbchien]

The ceraminc chambered combustion heater in my AC put an end to the pressure test AD o/w applicable....

 

[Capt.Crash'n'Burn]

What "chamber" are you talking about? If you meant cylinder, various attempts have been made to incorporate ceramics into the steel bore but AFaIK the only successful approach is CermiNil which combines the ceramic material with nickel and I don't believe any engine manufacturer offers that (aftermarket only).

No, I was refering to having the combustion chamber in the cylinder head coated along with the valves and pistons.

It acts as a heat shield that keeps the heads and pistons cool, along with improving the thermaldynamic efficiency of the engine (less energy lost to cooling system).

 

[bbchien]

IIRC they were tried in the big round pratts, but they were brittle, and chipped, which is bad for parts. Plus, in the Lycs and Continentals alike, the valve gets cooled against the surface of the valve seat (never mind the sodium filling on Lycs). So you can't coat that part.

 

[Capt.Crash'n'Burn]

IIRC they were tried in the big round pratts, but they were brittle, and chipped, which is bad for parts.

I was afraid that that was the problem with coatings.

Plus, in the Lycs and Continentals alike, the valve gets cooled against the surface of the valve seat (never mind the sodium filling on Lycs). So you can't coat that part.

Right, you coat the face of the valve, not the seat area. Coating the valve face prevents it from getting very hot in the first place. The only time it's exposed to heat is durring the exhaust stroke.

 

[gismo]

The ceraminc chambered combustion heater in my AC put an end to the pressure test AD o/w applicable....

I read that a recent change to the AD now requires periodic testing even if you have one of the newer ceramic coated heater tubes. Maybe not for your specific heater though. I guess they found some ceramic tubes that cracked. You might want to check on that.

 

[weilke]

You dont want to insulate the inside of the cylinder head in an aviation engine. The heat-sink effect of the metallic head helps to maintain detonation margin. The theoretical gain in achievable maximal thermodynamic efficiency would probably not make up for that.

 

[Capt.Crash'n'Burn]

You dont want to insulate the inside of the cylinder head in an aviation engine. The heat-sink effect of the metallic head helps to maintain detonation margin. The theoretical gain in achievable maximal thermodynamic efficiency would probably not make up for that.

Interesting.

So are you saying that after ignition, the ceramic surface of the cylinder head would flash heat and cause detonation??

 

[BiffJ]

Interesting.

So are you saying that after ignition, the ceramic surface of the cylinder head would flash heat and cause detonation??

I think what he's saying is that with the ceramic coating the heat would not be transferred to the cyl head and then to the air so it would build heat over a shorter time and at some point be hot enough to promote detonation and pre-ignition. The cyl head transfers much of the waste heat out of the system through the fins and if it can't do that the heat has to go somewhere....carbon build up in the cylinder, head and valves promotes pre-ignition by retaining heat and creating hot spots. I think the ceramic coatings would have the same effect.

Frank

 

[weilke]

I think what he's saying is that with the ceramic coating the heat would not be transferred to the cyl head and then to the air so it would build heat over a shorter time and at some point be hot enough to promote detonation and pre-ignition. The cyl head transfers much of the waste heat out of the system through the fins and if it can't do that the heat has to go somewhere....carbon build up in the cylinder, head and valves promotes pre-ignition by retaining heat and creating hot spots. I think the ceramic coatings would have the same effect.

What he said

A lot of stuff that works in race engines, automotive engines or on the test-stand doesn't seem to work in aviation engines with their huge air-cooled cylinders, teenie-weenie valves and hand-cranked mixture and ignition control.

 

[Doggtyred]

The cyl head transfers much of the waste heat out of the system through the fins and if it can't do that the heat has to go somewhere....carbon build up in the cylinder, head and valves promotes pre-ignition by retaining heat and creating hot spots. I think the ceramic coatings would have the same effect.

Frank

I think the heat would go out the exhaust pipe, with the ceramic as an insulator.

However.. one episode of detonation can shed the coating..

 

[gismo]

I think the heat would go out the exhaust pipe, with the ceramic as an insulator.

However.. one episode of detonation can shed the coating..

My guess (and this is just a guess) is that detonation margins are increased when a substantial portion of the energy released during each combustion event is absorbed by the cylinder head and piston. If that transfer was inhibited the peak temp and pressure in the cylinder would go up as the mixture started to burn and that would make detonation more likely. I know that detonation is harder to control in a large volume cylinder typical of aircraft engines.

 

[Capt.Crash'n'Burn]

My guess (and this is just a guess) is that detonation margins are increased when a substantial portion of the energy released during each combustion event is absorbed by the cylinder head and piston. If that transfer was inhibited the peak temp and pressure in the cylinder would go up as the mixture started to burn and that would make detonation more likely. I know that detonation is harder to control in a large volume cylinder typical of aircraft engines.

That actually makes a lot of sense.

Now if you were to use water/alcohol injection in conjunction with ceramic coatings...