limited by the speed of the air moleculesat that temperature
Kirby, I had a hard time following that, and I certainly don't have the depth of Physics or Math to understand, or much less work through, CD nozzles.... My knowledge is limited to a few basic facts regarding them.... 1. There are no shock waves upstream of the nozzle, as the flow is subsonic....2. When and if Mach 1 occurs AT the nozzle, there is a minimum 47% drop in pressure across the nozzle.... This is called "Choked Flow".... yes BUT that is only when there is no backpressure both the finite air supply causing an upstream loss of psi and the pellet act to drop the amount of that pressure loss...Ok there is a 4500 psi pressure vessel of 20cc and the pellet is 2cm down the barrel what is the barrel pressure at that point...The drop in psi is only caused by the growth in size of the vessel (Boyle's law) when the pellet has traveled to the point the vessel is 40cc you are down to 2250 psi...and the pellet/air is still subsonic... so no sonic chokingwith the converging cone feeding the barrel it acts the same way but at a certain point the psi/flow rate/size of the air chamber turn it into a pseudo converging diverging nozzle it happens at a psi that induces supersonic flow through the restriction(throat) and that is when he sonic choking happens producing the supersonic shock wave that since the pellet/and column of air have distance from the source of the shock wave it causes sonic packing behind the pellet but also disrupts flow as it travels up the air column supersonic and crumbling to subsonic and that pressure drop after the shockwave... The cd nozzle produces a supersonic jet which extends in to the diverging cone and only falls apart past the nozzle when shock waves form.the fall in pressure does not matter at that point... it is the shock wave that is packing the charge in front of it...3. Once Mach 1 occurs at the nozzle, there is a mass flow limit for any given pressure.... and no change in the output pressure can increase that.... 4. By shape of the Diverging (downstream) part of the nozzle can affect the velocity of the flow, but since the mass flow is fixed, increased velocity must be matched by decreased pressure....The thread is about the THEORETICAL MAXIMUM velocity that a PCP can produce, and that is a very simple calculation based on pressure (psi) x area (sq.in.) = force (lbs.), acting through a given distance, the length of the barrel in ft.... which results in the maximum possible energy (ft.lb) that can be generated.... Basically, in terms of energy, we are pushing hard to reach 70% of that energy in highly specialized experimental guns, like Lloyd used to reach 1745 fps in the thread he mentioned above.... and even the best of our usable PCPs have great difficulty reaching 50% of the maximum.... There is a thread in the Gate on Choked Flow, perhaps you may find somebody there who has a deep enough understand to help you through that complicated subject.... It would at least be worth your while to go through it as there is a lot of valuable information there.... http://www.gatewaytoairguns.org/GTA/index.php?topic=66737.0Bob
......................It has to be happening or Lloyd could not have beat the speed of sound in the 4500 psi original charge...
This is kind of like arguing about religion, a lot of things have to be taken on faith.
...........but science is also proving why...
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