how to seal a small inlet?

[Bill G]

I've been doing some studying on Lloyds topic of sonic choke or sonic joke.  Lots of math and lots of theory involved.  Any way. a question came too me that involves the inlet.  theoretically.....if I were to use an inlet that was only .063, the force closing it from pressure would be 5.5lbs at 1800psi and over 7 at 2600psi. The question is, will it actually seal?  with that small cross section, it would seem to me that even Delrin wouldn't give enough to make a reliable seal.  Perhaps UHMW, which is much softer would work?

What this pertains to is the use of a nozzle instead of a transfer port.  with a converging diverging nozzle, the volume of air that can pass through is far greater than what can pass through a "pipe".  In theory, this would allow us to use a much smaller inlet and still achieve the required flow.  Really the biggest gain is how much lighter the strike would have to be to open the valve.  Again, in theory, this could result in a valve for a big bore that opens with the force of a pellet slinger. We've all done plenty of work trying to seal valves the other end of the spectrum but has anyone done any at the other end? Maybe a configuration as I've loosely described would require a stronger closing spring. 

Lloyd maybe you have some input from your work with a balanced valve

Bill

[rsterne]

It would depend on the seat margin.... ie how much area that 7 lbs. of force is spread over.... It you used a tapered poppet in a knife-edged hole it may work fine.... The larger the seat area, the softer the material you will need.... Teflon works great of low pressures (eg. CO2).... O-ring material at ever lower pressures....

Bob

[Bill G]

So a spherical poppet in a converging cone would likely work as long as the cone isn't too sharp and the material isn't too soft.

Thanks Bob
Bill

[lloyd-ss]

Bill, sorry I missed this.  I don't think you'll have too much trouble sealing it, although a more compliant material like UHMW or Teflon might work more easily.  I think the margin width and the angles of the seat and valve are quite important.  Think about how a taper shank drill can lock up with very little force.  Two conical surfaces of slightly different angles or a sphere fitting into a conical recess ought to work.
Lloyd

[Bill G]

 Yes the tapper would have to be pretty shallow. I am thinking 160deg with a .030 transition(maybe less) into a a much tighter convergence.   I was just spit balling with this post. Thinking about if it would be possible to get higher performance by inducing sonic flow.  AND THEN  .......you started the sonic Choke or sonic joke thread.  That pretty much made this one null.  Thanks for the reply though, I'm following the other guys thread now LOL.   See you there.

Bill G   

[lloyd-ss]

................................................ with a converging diverging nozzle, the volume of air that can pass through is far greater than what can pass through a "pipe".  In theory, this would allow us to use a much smaller inlet and still achieve the required flow.  Really the biggest gain is how much lighter the strike would have to be to open the valve.  Again, in theory, this could result in a valve for a big bore that opens with the force of a pellet slinger. We've all done plenty of work trying to seal valves the other end of the spectrum but has anyone done any at the other end? Maybe a configuration as I've loosely described would require a stronger closing spring. 
......................

Bill

Bill,
You are talking about using the converging - diverging cone for the actual valve and that the throat area could be  smaller than the actual barrel bore.  I say that in reference to the fact that normally to achieve high velocities/ high power, we try and make all the convoluted passageways at least as large as the barrel bore.

Could you make a sketch of what you envision this thing looking like, in a more or less ideal configuration?  Ignore the problem of how it will be sealed for the moment.
Thanks,
Lloyd

 

[Bill G]

currently doing inventor drawings.  after following the sonic choke or sonic joke thread, I've started to reconsider some of the theory.

Bill

[lloyd-ss]

A lot of theory, all with some merit, but at least as many questions as answers.
Lloyd

[Bill G]

Lol.  Every answer gives birth to another question.