Can 206 PSI DETONATE?
206 PSI can go BANG ! ! !
Diesel engines operate efficiently anywhere from 14:1 to 25:1 compression ratio. So, the mean sea level air pressure of 14.696 PSI air compressed quickly at the ratio of 14:1 Or approximately 206 PSI becomes so hot it can detonate diesel fuel injected into it.
With PCP air rifles we are using easily 10 times the pressure of a common diesel engines initial compression. Any flammable lubricant could easily be atomized in a multi stage PCP pump as it is heated, collects at a valve and is suddenly released into the next stage or into the quickly heating connecting hose.
So, what could happen if the rifle tank is low in PSI when a pump or connecting hose detonates? What if the rifle tank is already heated and nearly full?
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Got it!! 😀
Thanks for taking the time to spell it out for me!
theoretically that would produce an infinite amount of heat. but that would require starting to pump in a vacuum.
when your tank has 0psi, it actually has 14.7psi. so, starting from 14.7psi and instantly pumping to 3000psi would increase temperature ~207 fold.
of course, your o-rings would melt long before you got to 3000psi. instantly pumping to just 45psi would triple your pump’s temperature, melt your o-rings and stop any further pressure increase.
Ah, so if one were to increase the pressure from 0 to 3000 in a single stroke it would produce an enormous amount of heat?
these discussions about pressure v temperature are governed by the guy-lussac ideal gas law. that law states the ratio of start/end pressure is equal to the ratio of start/end temperature. (it actually says more but that’s all we need to discuss pcp pressure v temperature.) none of the gas laws say anything about the difference between the start and end pressure/temperature.
it makes no difference whether you increase pressure from 100psi to 200psi or you increase pressure from 1500psi to 3000psi. the pressure doubles in both scenarios. the fact that pressure increases by 1400psi more in the 2nd scenario is irrelevant. the pressures double so the temps will double.
a diesel cylinder doesn’t really compress a gas. it compresses a mixture of a gas (air) and a liquid (diesel fuel). but if that were an ideal gas in the diesel cylinder,
(end-pressure)/(start-pressure) ~ 10 would cause the end-temperature to be about 10 times the start-temperature (with a bunch of assumptions about rapid enough compression that heat dissipation via conduction/convection/radiation would not be significant and the diesel gas/liquid mixture acting like an ideal gas).
when you pump from 2900psi to 3000psi you’re increasing pressure by (3000/2900 – 1) ~ .035 times. so temperature (if that increase were almost instant) would increase by ~.035 times.
so, if your pump were at 90F at the start and you cranked 14 strokes very rapidly on your pump (increasing pressure from 2900 to 3000), the temperature of the pump at the end of that would be about:
90F*(1.035) = 93F
of course, you probably can’t very rapidly pump 14 strokes starting at 2900 so i would expect significantly less than 3F temp increase because some of that heat dissipates in the room/floor where you’re pumping.
😕 Now i’m really confused.
How can a diesel engine make more pressure and temperature if it’s max chamber pressure is 500psi per stroke, yet when I pump from 2999 to 3000psi (what I would assume is a near 3000psi chamber pressure) it’s not significant? 😕
Could you elaborate a bit on your explanation?
This is good stuff!! 😉
you’re confusing absolute pressure with relative pressure. this seems to be a common error. the fact that you’re increasing your pressure by 1500 psi is irrelevant to the issue of pressure vs temperature. the relevant fact is that you’re doubling pressure.
increasing pressure from 1500psi to 3000psi, doubles your pressure and, if effected, almost instantly, the temperature would (briefly) double. you’re not doing anything even close to that with your pump because your pump is not insulated and you’re not increasing the pressure almost instantly.
I admit I don;t know very much about diesel engines, more of a two stroke engine guy…
So it relies on the existing heat from the first four minutes, sort of like when a gas engine precombusts (diesels) from carbon build up or lack of proper cooling…? And of course the run on jallopy… 😆
“Similar” engine is a glow plug nitro engine for RC stuff. Except it’s the filament that stays hotter than the other items and the glow plug is only heated during the initial firing up of the engine…
16:1 would produce around 500+psi. I’m thinking motor oil would combust but probably create a bunch of crap in the combustion chamber, they do get vegetable oil and other fats to combust in biodiesel engines. Nasty smelling shit right there.
Question, does a turbo on a diesel work the same way as a gas powered turbo (exhaust gas powered)? I remember something is different, but that was from researching turbo-diesel generators…
Well…..the glow plugs actually only stay on for 4 minutes in a Ford diesel. They compensate for a cold block and the heat that is lost rapidly to hundreds of pounds of cast iron. BTW, diesels run at least 16 to 1 compression and that’s for engines that depend heavily on turbo boost…
The big point is that diesel combustion requires a lot of things to be just right. A hand pump is not remotely akin to a diesel engine ands neither is the average airtank being filled. Just start a diesel on a cold day…
If it’s tenfold in a combustion chamber, and we are talking over normal atmospheric pressure, it’s 100x in the pump, yet the temperature isn’t 100x or the pump would melt instantly…
I pump my tanks up to 3000psi and I can tell you with absolute certainty that the pump never gets hotter than 200F.
32 psi times 10 is 320 psi (inside pressure of a combustion chamber at 10:1) I can turn over a car engine with the distributor cap removed and not generate any heat to speak of, and surely not generate ten times the ambient temperature of the block…
As Jerry noted the GLOW PLUG is what is needed to ignite the atomized fuel. Once the plug is hot it stays hot, a diesel engine will not start without some type of heat source or it would run without a glow plug and become a perpetual motion machine (which is a physical impossibility).
in a diesel cylinder with a 10-fold pressure increase (and insignificant heat loss because of the rapid compression), temperature should increase about 10-fold.
so, the flash point of motor oil should be reached in a diesel cylinder. but that just means the oil vaporizes and, if exposed to a spark/flame, it will combust.
with a hand pump, except when filling an empty tank, the pressure might double (after many strokes and significant time that, at least, some heat would dissipate).
but even if no heat dissipated and the pressure doubling were rapid, the temperature would, at most, double. which will still be well below the flash point of motor oil (unless the ambient/start temp in your pump environment is ~200F).
and, even with an empty tank and rapid pumping, you would almost certainly cause substantial o-ring damage before your pump reached oil’s flash point.
Good point Synopsys.
Flash point of motor oil 420-485 degrees F.
Diesel fuel 100-130.
Not to mention motor oil is NOT diesel fuel…
Would motor oil detonate in a diesel engine? Probably not. 😉
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CLICK..:idea: 💡 😯 the lights are ON ❗
Everybody should make sure their hands are in their own pockets. 😆 😆 😆
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you’re welcome.