Modelling the Ignition of Modular Charges

Transcription

1 Modelling the Ignition of Modular Charges Clive Woodley & Steve Fuller A presentation to: 42 nd Guns & Missiles Conference April 2007 QinetiQ/D&TS/WPNS/PUB

2 Contents 01 Background 02 Validation 03 Simulations 04 Conclusions & future work 2

3 01 Background 3

4 01 Charge design why UPCS? Existing inventory replaced with 1 module 4

5 01 Charge design advantages of UPCS Current charges Not fully IM compliant Not cleared for A1/C2 climatic conditions Wasteful decremental system Costly & L10 can t routinely be used for training Often remain in WMR until they life out With UPCS Same charges are used in training as are deployed for war fighting Training simplified/more realistic Substantial cost savings can be achieved through incremental system Logistic burden reduced Autoloader compatible 5

6 01 Modular charges the problem being addressed Safety & performance are important requirements linked to ignition Pressure waves eliminated or minimised and consistent Simultaneous ignition along length of charge Combustible cartridge cases present barrier to flamespread along the propellant bed Modules act as projectiles! Pressure difference (MPa) Time (ms) 6

7 01 Modelling approach - QIMIBS 2D mortar code Developed initially with MOD funding Developed further using QinetiQ funding Details presented at 22 nd International Symposium on Ballistics Ability to represent internal solid boundaries 7

8 02 Validation 8

9 02 Primer only single module initial geometry 9

10 02 Primer only single module Pressure (MPa) QIMIBS P1 QIMIBS P2 Round 1 P1 Round 1 P Pressure (MPa) QIMIBS P1 QIMIBS P2 Round 4 P1 Round 4 P Time (ms) Time (ms) 1.43g black powder Max velocity measured: 1.5m/s Max velocity predicted: 3.2m/s 1.25g NC Max velocity measured: 2.0m/s Max velocity predicted: 5.0m/s Correct trend predicted for pressure and module velocity Module velocities overpredicted but no account taken of sliding resistance 10

11 02 5 modules - flamespread Time of first visible light (ms) Test 1 Test 2 Simulation Distance from breech (m) 11

12 03 Simulations 12

13 03 Simulations Single module Igniter mass & location Flash tube diameter & vent hole size Three modules Five modules 13

14 03 Single module igniter mass (5g top, 15g bottom) 0.5ms 1.0ms 14

15 03 Single module igniter mass (5g top, 15g bottom) 1.5ms 2.0ms 15

16 03 Single module igniter mass (5g top, 15g bottom) 2.5ms 3.0ms 16

17 03 Single module igniter mass (5g top, 15g bottom) 3.5ms 4.0ms 17

18 03 Single module igniter mass (5g top, 15g bottom) 4.5ms 5.0ms 18

19 03 Single module igniter mass (5g top, 15g bottom) 5.5ms 6.0ms 19

20 03 Single module igniter mass (5g top, 15g bottom) 6.5ms 7.0ms 20

21 03 Single module igniter mass Temperature (K) g P6 5g P5 5g P4 15g P6 15g P5 15g P Time (ms) 21

22 03 Single module effect of igniter position Outside P6 Outside P5 Outside P4 Inside P6 Inside P5 Inside P Outside P6 Outside P5 Outside P4 I/O P6 I/O P5 I/O P4 Temperature (K) Temperature (K) Time (ms) Time (ms) Outside = outside module but inside flash tube Inside = inside module but outside flash tube Modelling indicates better ignition if igniter material is both sides of the flash tube 22

23 03 Single module effect of flash tube diameter mm P6 52mm P5 52mm P4 26mm P6 26mm P5 26mm P mm P6 20mm P5 20mm P4 26mm P6 26mm P5 26mm P4 Temperature (K) Temperature (K) Time (ms) Time (ms) Modelling indicates better ignition for 26mm flash tube diameter 23

24 03 Single module effect of flash tube hole size mm P6 14mm P5 14mm P4 10mm P6 10mm P5 10mm P mm P6 6mm P5 6mm P4 10mm P6 10mm P5 10mm P4 Temperature (K) Temperature (K) Time (ms) Time (ms) Modelling indicates better ignition for 6mm flash tube holes 24

25 03 Three modules initial geometry 25

26 Temperature (K) QinetiQ Proprietary 03 Three modules 10g black powder per module P1 P2 P3 P6 P5 P Time (ms) Taking 600K as the propellant ignition temperature, propellant in 2 nd & 3 rd modules ignited 0.8ms & 1.7ms after the 1 st module Temperature (K) P9 P8 P7 P12 P11 P Time (ms) Use another internal ballistics code to predict pressure waves 26

27 03 Five modules initial geometry 27

28 03 Five 10g black powder per module Temperature (K) P1 P2 P3 P6 P5 P Time (ms) Igniter in last module not ignited Module 2 might ignite first Taking 600K as the propellant ignition temperature, propellant in 2 nd, 3 rd & 4 th modules ignited 1ms, 2ms & 5ms after the 1 st module use another internal ballistics code for ΔP Temperature (K) Temperature (K) P9 P8 P7 P12 P11 P Time (ms) P15 P14 P13 P18 P17 P Time (ms) 28

29 04 Conclusions & future work 29

30 04 Conclusions & further work QIMIBS has much of the functionality required to model MCS Validated for two primers for 1 & 5 modules Parameter studies showed 5g black powder per module not likely to ignite Best position of igniter is both sides of flash tube 26mm diameter flash tube better than 52mm and 20mm Reducing flash tube vent area predicted to produce better ignition Predictions for 5 modules show Primer and igniter insufficient to ignite (5 th ) module adjacent to the projectile Module 2 might ignite before module 1 Possibility of significant ignition delay for 4 th module 155mm gun firings planned & further modelling Conclusions likely to be very dependent on primers and geometries used in this study 30

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