Question about reed valves

[fireslave]

I am wondering what the maximum limitations are on reed vaves...

is there a reed valve design that can open and close 5000x per second, or is that absurdly beyone what is possible? could such a valve withstand heat variations in the 500F to 1200F range?

it wouldnt need to prevent 100% of backflow, just 95% of it...

it would have to allow like 10 CFM of air to flow at like a 5 psi difference, but would have to close occasionally to prevent reverse flow... occasionally being thousands of times per minute.


thanks for any input whatsoever

 

[Compositepro]

The reed valve could move that fast if you could get the fluid to reverse flow that fast. Not likely but not impossible. It would be like the reed in a wind instrument.

 

[fireslave]

are any such valves durable in the long term?

i was under the impression that carbon fiber was only good to about 500-600F, and i figured metal valves would fatigue easily...


i actually way over stated the speed... i originally meant 5000 times per minute but i wrote second...

I actually paid more attention this time and its closer to 200x a second, which is good.... but unfortunately the temperature is closer to 1700F, which seems really bad. if there are valves that can withstand direct contact with a flame that would be ideal, but i can design around that.


they use reed valves in pulse jet engines, right? they probably stay cooler though as all the inlet air chills them once per cycle... I dunno.

 

[MikeHalloran]

The spring steel reed valves used in two-stroke engines can have useful lives within their fatigue limits, provided deflection is limited, typically by a stiff finger backing up the reed and spaced away from the static reed position by a couple mm at its tip.

While they don't ordinarily communicate directly with the combustion chamber, it's possible that they could survive there, provided that the engine is always running at design speed, like a pulse jet, where the average temperature of the reed is kept within reason by the cold gas at the inlet.

If your flow is hot on both sides of the reed, you're screwed.



Mike Halloran
Pembroke Pines, FL, USA

 

[Compositepro]

Maybe platinum would work.