Ignition Point vs Mass Burn Rate

[Parrott-Cannon]

I burned FG black powder (90 grains) in clear plastic tubes, ½ inch in diameter and 1 1/8 inches long.  I video the burns at 1200 frames per second and initiated the burns with cannon fuse.  The fuse was placed at the bottom, top and middle of the powder column.  A new tube was used for each replicate and fuse position.  The following are the average (5 replicates) mass burn rates under the conditions described:
When the fuse was located at the bottom of the tube the powder burnt at 1240 grains per second.  Shortly after ignition the powder column was pushed from the tube and burn very rapidly.
When the fuse was located at the middle of the tube the powder burnt at 610 grains per second.  The powder column above the fuse was ejected from the tube shortly after ignition and burned very rapidly.  The powder below the fuse did not start burning until the ejection of the powder above the fuse and then burn down the tube.
When the fuse was located at the top of the tube the powder burnt at 281 grains per second.  The powder burnt down the tube with no ejection of powder particles.
While these results can not be directly related to velocity they indicate black powder at least in a chamber environment and at atmospheric pressure can burn at different rates depending on the ignition point.
 

[jeeper1]

Interesting.
Videos would be nice and very interesting to watch.

[Double D]

 
 
I think understand your grain rate per second to mean how many grains (weight) of powder  burns in a second-correct?

[Parrott-Cannon]

Thank you for the suggested wording change.  Yes it is a mass burn rate of grains (weight) per second.

[Artilleryman]

I find this very interesting.  I was wondering what would happen if there was a projectile or wadding.

[Cannoneer]

Parrott-Cannon,
Here's a blast from the past that contains a couple historical references related to your topic. 

http://www.gboreloaded.com/forums/index.php?topic=174589.0

[Joe111]

I find this very interesting.  I was wondering what would happen if there was a projectile or wadding.

Shouldnt change the burn rate. Not much at least. Residence time is too short.

[Joe111]

I found this millitary test on blackpowder.
http://www.dtic.mil/dtic/tr/fulltext/u2/a129087.pdf

[Parrott-Cannon]

I find this very interesting.  I was wondering what would happen if there was a projectile or wadding.

Shouldnt change the burn rate. Not much at least. Residence time is too short.

The initial burn rate is affected by the number of particles ignited, the flame propagation rate and the burn rate of the powder particles.  The burn rate is impacted by the pressure.  The initial pressure is the atmospheric pressure, the resistance of the projectile due to friction, and the mass of the projectile per square inch.  As the powder burns it produces gases, when the pressure exceeds the initial pressure the projectile begins to move.  In a chambered weapon the pressure drops at the initial movement of the projectile due to the increased volume experienced by the gases and the burn rate changes.