Idea for possible cartridge improvement

scriptguru

scriptguru

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I am not sure this is right forum for a thread like this, but I don't know what forum here would fit this thread better.

As we all know, only part of powder's energy is being used to actually propell a bullet - the rest just heats up a firearm and increases "bang" loundness.

Did you hear or anything about experiments to make use of this unneeded heat :confused:

There are many possible solutions that come into my mind:
  • replace part of powder charge with water-filled capsule
  • same, but with CO[SUB]2[/SUB] filled capsule
  • same, but with powder that converts to gas when heated

Something like that could make firearm cooler (because some thermal energy will be consumed to change filler state from solid/liquid to gas), eliminate or reduce flash, make sound quieter.

I didn't perform any calculations for now, so I don't have idea about proportions. Please, don't perform any experiments if you are not sure what you are doing :cool:.
 
I like the way you're thinking, but I'll point out a few things which could help you dig a little deeper into the idea:

1) Gun powder is a powder which converts itself into a gas as it reacts.

2) Using water to generate gas from heat is a neat idea, but not ideally applicable to this purpose. It takes 4200 joules of energy to raise 1 litre of water 1 degree celcius. That works out to 4.2j per cc. It would take 420 j to make that cc of water into steam That is all energy which would be pulled out of the combustion reaction.

3) If you take a close look at the ingredients on the back of a bottle of gun powder, you'd see that the recipes contain many different components for different effects. It's already very scientific.
 
1) Sure, but also it generates a lot of unnecessary heat. The idea is to make use of this heat.
2) Let's imagine that bullet energy is 400j. It means that powder charge generated at least 400j of mechanical energy + ###j of thermal energy. If we use some of this ###j of thermal energy to create more gases from liquid or solid body, it will just add some energy to initial 400j.
3) Yes, you're right - that's why I asked if anybody knows that something like this is already in use.
 
Wikipedia said:
Gunpowder contains 3 megajoules per kilogram
Click to expand...

3,000,000 J/kg = 3000J/g
1 gram = 15.4grain

Let's do a scenario: .50 Beo, 350grain slug, 35 grains of powder.

This powder load is 2.3 grams, so, roughly 6800 joules of energy is released in the combustion.

Let's find out how much water we can evaporate with that energy:

E= M x SHC x (delta)T
6800j = M x 4.2 x 80
20.24g = M

20g = ~20cc.


...But it doesn't stop there. This is the first of 4 steps

(Here's an example I grabbed off of google answers)

A 79g sample of water at 21oC is heated until it becomes steam with a temperature of 143oC. Find the chnage in heat content of the system in joules. PLEASE show all workings.


1) Raise the temperature from 21 C to 100 C:
Mass of water * specific heat of water * temperature rise
79g * 4.2 J/g K * (100-21) = 26200 J
2) Evaporate the water:
Mass of water * Heat of Vaporization
79 g * 2260J/g = 178500 J
3) Raise the temperature from 100 C to 143 C:
Mass of steam * specific heat of steam * temperature rise
79g * 2.0 J/g K * 43 = 6800 J
4) Add the three numbers:
26200 + 178500 + 6800 = 211.5 kJ
 
The heat is not - not - unnecessary.

Charles' Law is a very basic chemistry equation. It says that the volume of a given amount of gas increases in a direct line with an increase in temperature.

It is not the transformation of a small amount of solid fuel (propellent) to a large amount of gas that provides high velocities, it is its transformation into a large amount of high temperature gas. Without the heat to provide additional pressure, your bullet would have a trajectory like a rainbow.
 
bad implement, but not completely unfounded. Use of water ( a little bit ) in a suppressor (if in a country that allowed it) would suppress the noise the firearm generates more than the suppressor alone dry. I believe the reasoning behind it is that the sound wave is further absorbed into the water rather than continuing out the barrel completely.
 
Why are you trying to get rid of "unneeded heat"? Why do you think it is unneeded? Why is the present method of dissipating the "unneeded heat" (warm barrel and big bang) not the best method? How do you calculate what amount of the heat generated is "unneeded" when, as Atom pointed out, a great deal of it is, in fact, "needed"?
 
ATOM said:
The heat is not - not - unnecessary.

Charles' Law is a very basic chemistry equation. It says that the volume of a given amount of gas increases in a direct line with an increase in temperature.
Click to expand...

Perhaps this is only semantics but since you are dealing with a constant volume, the temperature increase contributes to the overall chamber pressure which in turn, relates to velocities and all that. In order to obtain a desired velocity, if you somehow (significantly) reduce chamber temp, you've got to bump up the charge no ? Seems to me this could lead to a cat chasing its tail scenario.
 
rtracer13 said:
bad implement, but not completely unfounded. Use of water ( a little bit ) in a suppressor (if in a country that allowed it) would suppress the noise the firearm generates more than the suppressor alone dry. I believe the reasoning behind it is that the sound wave is further absorbed into the water rather than continuing out the barrel completely.
Click to expand...

More or less. A 'wet can' uses the liquid inside to cool the combustion gases which have exited the barrel. This reduces the pressure and thus helps lower the noise from escaping gas as it exits the suppressor.
 
About 15%-25% of the powder's chemical energy ends up as kinetic energy in the bullet. The rest goes to heat (in various places).

A gun is a "single stroke heat engine", and is remarkably analogous to a gasoline or diesel engine - and the thermal efficiency of a gun is broadly comparable to their thermal efficiencies.

While it is natural to think about good uses for the 75%+ waste heat (for example, making a gun more powerful, or making it more efficient), when you dig into what is happening it turns out that this waste heat is largely the cost of doing business. The various ideas you suggest, to absorb some of the heat of combustion, would end up reducing the peak temperature reached by the gun gas. The question is, is that a better place for the heat to go? It turns out, for both performance reasons and efficiency reasons, this makes things worse. In a heat engine, higher efficiency and higher performance are achieved when you go to *higher* peak temperatures. There are other practical tradeoffs to make (e.g. barrel life due to erosion) which hold back interior ballisticians from choosing powders that give the highest possible flame temperatures. High nitroglycerin propellants (for example cordite, which has 57% NG) have very high flame temps - however the small increase in thermal efficiency that they give is more than outweighed by other negative factors, which is why you don't commonly see cordite being used as a propellant these days.
 
Thanks for explanations, guys.
I thought about most problems you described, but wanted to share it anyway just in case.
Of course, firearms were evolving for hundreds years and they have been improved during all this time, but I believe further improvement is still possible.
 
The interesting concept is finding a way to harness that surplus heat - in a productive, useful fashion - after the bullet has left the muzzle.
 
As I understand, even experiments on this topic would hardly be legal in Canada without special permission, since silencers are prohibited, and anything reducing sound even by 0.5dB is a silencer.
 
scriptguru said:
As I understand, even experiments on this topic would hardly be legal in Canada without special permission, since silencers are prohibited, and anything reducing sound even by 0.5dB is a silencer.
Click to expand...

Point taken and thanks for raising it, but right now we are talking principles of physics and chemistry, not the construction of anything illegal.
 
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