I like how in the suppressor video the shooter gets thin safety glasses and the camera gets a thick bulletproof shield for protection.
Not sure if that 110,000 frames/sec camera is in my airgun budget but I like how in the suppressor video the shooter gets thin safety glasses and the camera gets a thick bulletproof shield for protection.
The text goes further explaining the desirability of choked flow in the second stage of pellet acceleration. It states that transfer port diameter can easily be calculated to based on achieving Mach 1 in the TP. What I would like to know, is the speed of sound dependent on the absolute pressure in the TP? The higher the pressure, the more dense the air; and I believe, the higher the speed of sound. So, the choked flow velocity point of the TP should depend on the pressure in the TP - something that is not constant - and is actually rather a steep up and down spike.
I wonder if the choked flow TP model has an analogy in air conditioning (or if that can shed some light on helping me understand useful heat transfer, via flow through a restrictor). A/C or refrigeration works by compressing a gas such as Freon by means of a compressor. The rapid increase in pressure increases the temperature of the gas. The hot gas is passed through a radiator where the heat is rejected back to near ambient. Then the near ambient temperature high pressure gas is expanded through a restrictor. There, the resultant rapid pressure drop across the "nozzle" causes the gas to cool significantly. That cold lower pressure flow is directed through a second radiator, placed in a location where it can pick up heat, such as inside a refrigerator.Else, choking the flow in a TP seems counter to efficiency in airguns. Certainly, TP restrictions reduce power in PCPs. Just using a TP restrictor to reduce power is not a good way to increase efficiency either. What are they good for? Restrictors are useful to flatten the velocity curve of unregulated PCPs.This is my way of stating that I see some hazy logic, but am not yet convinced the articles are using convincing math. I did not see them making any adjustment to the value of Mach 1 for the increased pressure and temperature in springer TPs. Nor acknowledge that temperature and pressure in the TP are not constant while the pellet is in the barrel. Nor recognize that when the pellet is propelled in the choked flow mode, that the piston has and is moving backwards in bounce. In my simplistic view, anything that adds restriction to flow through the TP after peak pressure is likely to increase piston bounce. For this reason, the fact that reducing piston bounce is known to increase efficiency keeps me skeptical of the choked flow model - unless that pressure drop has the property of extracting thermal energy to help expand the air behind the pellet. Thermal energy that would otherwise be "lost" (apparently the main claim for coked flow in the TP).The simple act of shooting similar pellets that have a range of weights shows an "efficiency curve". Shooting pellets that are too light or too heavy for a given spring airgun system reduces the power seen in measured pellet velocity. Too heavy a pellet looses energy because it provokes more piston bounce. The pellet is more reluctant to accelerate and spends more time in the barrel. Taking longer to leave places the pellet nearer the breech when the piston has bounced back far enough to lower the average driving pressure significantly.A light pellet is less efficient because it moves so easily and so early, that full pressure in front of the piston cannot be reached. It is possible that the flow through the TP is so fast with a light pellet, that the TP is operating in a choked flow mode during more of the light pellet's barrel time. Here, choked flow would reduce the pressure acting on the base of the pellet, limiting its acceleration, and ultimately it velocity, energy and system efficiency. In both too heavy and too light pellet model above, the main cause of inefficiency is the reduced average air pressure acting on the pellet base. The too light pellet model is more likely to see supersonic choked flow through the TP, because the pellet velocity is closer to the speed of sound. It does not seem to help; except to reduce the air pressure behind the pellet. I rest my case...
My m48 gets more for with light pellets. Now my PCPs get more for with heavy pellets.
Look at the results from the RS-2 . The 7 grain gets the most fpe.
I'm just going by what I've observed. Ive only had 2 springers in my life time and only ever chronoed the one I have now.