A Full Scale Hydrodynamic Simulation of High Explosion Performance for Pyrotechnic Device

파이로테크닉 장치의 고폭 폭발성능 정밀 하이드로다이나믹 해석

Abstract

A full scale hydrodynamic simulation that requires an accurate reproduction of shock-induced detonation was conducted for design of an energetic component system. A detailed hydrodynamic analysis SW was developed to validate the reactive flow model for predicting the shock propagation in a train configuration and to quantify the shock sensitivity of the energetic materials. The pyrotechnic device is composed of four main components, namely a donor unit (HNS+HMX), a bulkhead (STS), an acceptor explosive (RDX), and a propellant (BPN) for gas generation. The pressurized gases generated from the burning propellant were purged into a 10 cc release chamber for study of the inherent oscillatory flow induced by the interferences between shock and rarefaction waves. The pressure fluctuations measured from experiment and calculation were investigated to further validate the peculiar peak at specific characteristic frequency (${\omega}_c=8.3kHz$). In this paper, a step-by-step numerical description of detonation of high explosive components, deflagration of propellant component, and deformation of metal component is given in order to facilitate the proper implementation of the outlined formulation into a shock physics code for a full scale hydrodynamic simulation of the energetic component system.

고에너지 구성 요소 시스템의 설계를 위하여 고폭화약의 폭발 반응을 엄밀하게 모사할 수 있는 실제 규모의 하이드로다이나믹 해석을 수행하였다. 폭발성능 정밀 해석 SW는 고에너지 물질의 충격 민감도를 정량화하기 위한 반응 유동 모델을 검증하고 일련의 화약 트레인을 통과하는 충격파 전달을 예측하기 위해 개발되었다. 파이로테크닉 장치는 여폭약(HNS+HMX), 격벽(STS), 수폭약(RDX), 파이로테크닉 추진제(BPN)로 구성된다. 추진제 연소로 인하여 생성된 고압의 연소 가스는 충격파와 저밀도파 간 간섭에 의해 유도된 고유의 진동 유동 특성을 파악하기 위하여 10 cc 밀폐형 챔버에 유입된다. 특정 주파수(${\omega}_c=8.3kHz$)에서의 피크 특성을 검증하기 위하여 실험 및 계산으로 측정된 압력 진동을 비교하였다. 본 연구에서는 고폭화약의 폭발반응과 추진제의 폭연반응, 비-반응 금속의 변형에 관하여 단계별 수치해석 기법들을 충격 물리 해석 SW로 구현함으로써 고에너지 물질 시스템에 대한 대규모 하이드로다이나믹 시뮬레이션을 용이하게 하였다. 개발된 고폭화약 폭발성능 정밀 해석 SW를 고에너지 구성 요소 시스템의 파이로테크닉 연소 반응 M&S에 적용하여 실험 결과와 비교함으로써 검증하였다.

Fig. 1. Operating sequence on flyer impact initiation of an exploding foil initiator

Fig. 2. Calculation results for flyer velocity at 2.0 and 2.5 km/s on HNS detonator

Fig. 3. Impact pressure profile

Fig. 5. Schematic of pyrotechinc bulkhead initiator and timed images of calculated pressure contour at t = 0 – 3.5 μs with pressure range 0 - 10 GPa

Fig. 4. Free surface velocity profiles

Fig. 6. Time trace of shock attenuating pressure along STS bulkhead (dot : experimental data, dotted line : calculation data, red line : fitted data)

Fig. 7. Test specimen (upper) and computational domain (lower) for closed chamber test

Fig. 8. Pressure histories for Go/No-go cases

Fig. 9. Raw and filtered pressure profiles

Fig. 10. Power spectral densities of closed chamber test data

Fig. 11. Timed images of pressure at (a) 3.8 mm, and (b) 4.0 mm bulkhead of explosive train

Fig. 12. Shock pressure trajectory in Detonator – Bulkhead - Acceptor of pyrotechnic initiator

Fig. 13. Reaction and regression rates of BPN based on the Arrhenius temperature dependence

Fig. 14. Shown schlieren (top) and pressure (bottom) evolution in time for entire pyrotechnics-chamber assembly that shows a detonator (HNS+HMX), bulkhead (STS), acceptor (RDX), and gas-generating propellant (BPN)

Fig. 15. Shape comparison of pyrotechnic device between calculation and experiment

Fig. 16. Comparison of pressure signal inside the chamber between calculation and experiment

Table 1. Modeling constants for HNS, HMX, RDX(pure) and CH-6(97.5% RDX)

Table 2. Material properties for STS[12,13].

Table 3. CBT Experimental Result

Table 4. Nominal Arrhenius law and JWL EOS parameters for BPN