3F black powder combustion gas constant

[redsox15]

Does anyone know the combustion gas constant (R) for 3F black powder? I was looking for 4F powder but it seems all the hunting supply stores in my area only have 3F and I called a place who had never heard of 4F powder before. Once I find the R value I can do the calculations for my ejection charges.

Thanks in advanced,

Matt

 

[Reinhard]

The gas constant is the same as for 4F. This is a property of the chemicals involved and independent of the grain size.

See here for numbers (I guess you already know about it):
https://www.info-central.org/?article=303

Reinhard

 

[redsox15]

makes sense that it is independent of grain size. thanks

Matt

 

[Rocketjunkie]

3F works fine for ejection. The particles do burn longer and will require good wadding or other chute protection.

 

[Shade]

That equation is the Ideal Gas Law, PV=nRT. R is constant for all gases,
the numeric value only changes due to the units changing. Remember
the temp is always in Kelvin or Rankine (the absolute scales) never Celsius
or Farhenheit.

 

[jimzcatz]

4F is available online, but shipping for 1 pound is as much as product usually. Be absolutely sure you are getting BP, and not Pyrodex as most hunting supply stores I have found do not carry real BP. I dont know where you are, but BP is available locally in Raleigh NC at Hill'S. I think Ken Allen at Performance hobbies sell it,you might put a motor order together and make the shipping charge worth while. Good luck

 

[redsox15]

Im in eastern MA, Andover to be exact but I have called a couple of stores in NH and they carry the Goex FFFg black powder in the 1lb bottles. I will double check when I go to make sure I'm getting powder and not pyrodex


Matt

 

[bobkrech]

For every gram of BP you burn, you obtain 0.0182 moles of gas and 0.0026 moles of condensibles. The combustion temperature of BP is 1739K, so the hot gas peak volume is (1739/273)*(0.182/0.014) = 8.3 times the cold gas volume, which for 1 gram of BP is 2600 cm^3 or 157 cubic inches at 1 atm pressure.

As the gas expands and cools down the volume shrinks until it reaches the ambient temperature. Of the more volatile gases, you get 0.0158 moles including water and 0.0140 excluding water. The volume of a mole of gas at 273K is 22.4 liters, so 1 gram of BP generates at least 313 cm3 or 19 cubic inches of cold gas per gram of BP @ 1 atm. pressure.

See attachment for details calculated by propep.

Bob

View attachment BP Combustion.TXT

 

[guywad]

Im in eastern MA, Andover to be exact but I have called a couple of stores in NH and they carry the Goex FFFg black powder in the 1lb bottles. I will double check when I go to make sure I'm getting powder and not pyrodex


Matt

Kittery Trading Post in Maine is a good source. About 25 minutes one way from the parking lot at the Amesbury field. No hassles at all when buying. They stock Goex FFFFg and had 18lbs of it when I bought some earlier this spring.

 

[shockie]

For every gram of BP you burn, you obtain 0.0182 moles of gas and 0.0026 moles of condensibles. The combustion temperature of BP is 1739K, so the hot gas peak volume is (1739/273)*(0.182/0.014) = 8.3 times the cold gas volume, which for 1 gram of BP is 2600 cm^3 or 157 cubic inches at 1 atm pressure.

As the gas expands and cools down the volume shrinks until it reaches the ambient temperature. Of the more volatile gases, you get 0.0158 moles including water and 0.0140 excluding water. The volume of a mole of gas at 273K is 22.4 liters, so 1 gram of BP generates at least 313 cm3 or 19 cubic inches of cold gas per gram of BP @ 1 atm. pressure.

See attachment for details calculated by propep.

Bob

Bob, post yer pepcoded.daf file as a .txt file please

I don't have pine charcoal in mine, just oak and maple. DO you also have airfloat charcoal?

Terry Dean