Experimental set-up and results of the process of co-extruded perforated gun propellants

17 Pages·0.618 MB·English

by  Zebregs Martijn, Driel Chris van.

Experimental set-up and results
of the process of co-extruded
perforated gun propellants
Martijn Zebregs, Chris van Driel
[email protected]
TNO Defence, Security and Safety – Protection, Munitions and Weapons – Energetic Materials
Chris van Driel
Introduction
• Co-layered gun propellants – advantages and difficulties
• Performance characteristics
• Co-extrusion of gun propellants at TNO
• Experimental set-up
• Development steps in recent years
• Burning characteristics of 1-perf co-extruded co-layered
propellant
• Future developments
• Conclusive remarks
2 Co-extrusion of gun propellants IM/EM Symposium, Tucson, AZ, May 2009
Co-layered propellants
• US Patent 4581998 (1986) A.W. Horst et al.
• Advantage: improvement of gun performance
by enlargement of the impulse on the projectile
• Ritter ICT 2007
Manufacture:
• Disadvantage:
‘The time-consuming manufacturing of assembled propellant sheets
proved to be a difficult task.’
• TNO’s approach: co-extrusion
 with proper die design easy manufacturing (not labour intensive
and excellent geometries in one step)

3 Co-extrusion of gun propellants IM/EM Symposium, Tucson, AZ, May 2009
Co-layered propellants
Advantages Notes
• Increased performance • Increased performance of sheet
• High progressivity of propellants is comparable to the
co-extruded 0- and 1-perf grains performance of regular granular
• Decreased erosivity of high multi-perforated propellant
energy propellants • Variations in layer thickness may
• Increased ignition behaviour result in increased dispersion of V
0
(e.g. LOVA propellants) • Contrary to co-layered sheet
propellants, co-extruded propellants
provide wide variation in
geometries, implying a larger
number of possible applications
Ritter, ICT 2007
(note: not multi-perforated grains!)
4 Co-extrusion of gun propellants IM/EM Symposium, Tucson, AZ, May 2009
Co-layered propellants
• Examples of simulated performance effects
7-perf versus 0-perf co-layered sheet propellant
350 1200
300 1000
250
800 P 7-perf
]
Pa] 200 600 m/s P 0-perf
P [M 150 400 V(0) [ TT 70--ppeerrff.
100
50 200
0 0
0 0.005 0.01 0.015
Time [s]
Ritter, ICT 2007
5 Co-extrusion of gun propellants IM/EM Symposium, Tucson, AZ, May 2009
Performance characteristics
• Examples of simulated performance effects
7-perf; T (core) = 3515 K; T (layer) = 3170 K
f f
factor burning rates = 1.5
350 1200 350 4500
pressure pressure
300 1000 300 4000
]
s gas temperature
MPa] 220500 680000 tile) [m/ MPa] 220500 33050000 s) [K]
P [ 150 400 ojec P [ 150 2500 T(ga
100 r 100 2000
p
50 projectile 200 V( 50 1500
velocity
0 0 0 1000
0 0.005 0.01 0.015 0 0.005 0.01 0.015
Time [s] Time [s]
P conv. P co-layer T conv. T co-layer P conv. P co-layer T conv. T co-layer
 T = 3165 K
max
= 3385 K without ‘cool’ outer layer
6 Co-extrusion of gun propellants IM/EM Symposium, Tucson, AZ, May 2009
Performance characteristics
• Examples of simulated performance effects
7-perf; T (core) = 3515 K; T (layer) = 2900 K
f f
factor burning rates = 2
350 1200 350 4500
pressure pressure
300 300 4000
1000
]
s gas temperature
MPa] 220500 680000 tile) [m/ MPa] 220500 33050000 s) [K]
P [ 150 400 ojec P [ 150 2500 T(ga
100 r 100 2000
p
50 projectile 200 V( 50 1500
velocity
0 0 0 1000
0 0.005 0.01 0.015 0 0.005 0.01 0.015
Time [s] Time [s]
P conv. P co-layer T conv. T co-layer P conv. P co-layer T conv. T co-layer
 T = 3040 K
max
= 3385 K without ‘cool’ outer layer
• Higher charge densities  further performance improvement
7 Co-extrusion of gun propellants IM/EM Symposium, Tucson, AZ, May 2009
Performance characteristics
• Examples of simulated performance effects
Dynamic vivacity 1-perf grain:
(both layers intact until Z = 100%)
3
]
u. 2.5
a.
[ no layer
y
t 2
ci
va r(core)/r(layer) =
vi 1.5 1.5 (sim.)
c
mi 1 r(core)/r(layer) =
na 2 (sim.)
y 0.5
D
0
0 0.2 0.4 0.6 0.8 1
P/P(max) [-]
 increased progressivity, even without double peak;
‘low’ (usual) pressure exponent
 with smaller outer layer: progressive + double peak in P-time curve
 large grains (applicable for both medium and large calibre)
8 Co-extrusion of gun propellants IM/EM Symposium, Tucson, AZ, May 2009
Co-extrusion of co-layered propellants at TNO
2 barrels
double barrel
capillary rheometer
heating zones
pressure
transducers
(co-)extrusion block
9 Co-extrusion of gun propellants IM/EM Symposium, Tucson, AZ, May 2009
Co-extrusion of co-layered propellants at TNO
First attempts (2005-2006):
• Non-perforated co-extruded propellant
• ‘Self-encapsulation’ is theoretically possible for a large viscosity
difference (factor 2.5), but appears to fail
• Improper die design leads to slip, resulting in a ‘rope of beads’
• Experiments resulted in good insight in the problem of
co-extrusion
10 Co-extrusion of gun propellants IM/EM Symposium, Tucson, AZ, May 2009