Thanks Scott,I guess I misunderstood, I thought Bob was describing the ideal barrel where the pellet is pushed by a non-varying source tank pressure for the entire length of the barrel without losses. In that case the energy imparted into the pellet simplifies to the PxAxL and should be the ideal upper limit for those conditions. I'm not sure I understand what maximum energy means if it does not apply to the pellet at the muzzle. I need to re read some of the discussion. Glad I asked
Stan, the P x A x L term is the maximum energy available for the shot, indeed the "upper limit for those conditions".... Part of that goes into accelerating the air itself, so is not available to accelerate the pellet.... At 3000 psi a .22 cal. barrel 24" long contains 55 grains of air.... This is why the very best of our PCPs on air have great difficulty approaching 50% of the P x A x L theoretical number.... In fact, I use P x A x L / 2 as a "lofty goal" for PCPs running on air.... The ~ 30% loss in the spreadsheet (now about 10% in the latest version) is after you take into account all the known losses.... If you ask me, getting within 10% is quite a feat, Lloyd should be very proud of that result.... I'm looking forward to seeing the latest version of his spreadsheet....Bob
Regarding the approach being taken......."maximum FPE is of course bore area x pressure (ie force) x barrel length"........even with an infinite reservoir, expanding air doesn't behave this way. In the interest of accuracy, which seemsto be the stated goal, why not use the right equation..... for an adiabatic process, w = (p2V2-p1V1)/(gamma-1) Also, ........." the type of expansion is different while the valve is open or closed "..........this too is incorrect. Whetherthe valve is open or closed is of no consequence, the above equation still holds. What does change, however, are theboundary conditions and distribution/magnitude of losses associated with each. Ron