Effect of a collapsing gas bubble on the shock-to-detonation transition in liquid nitromethane

• Published in: Journal of applied physics 2024-12, Vol.136 (22)
• Main Authors: Turley, W. D., La Lone, B. M., Mance, J. G., Staska, M. D., Stevens, G. D., Veeser, L. R., Aslam, T. D., Dattelbaum, D. M.
• Format: Article
• Language: English
• Subjects: cameras; Chemical reactions; Detonation waves; Explosive compacting; Explosives; Flat plates; High speed cameras; Hydrodynamics simulations; INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; Nitromethane; Optical fibers; optical spectroscopy; Pressure dependence; Shock wave propagation; Shock waves; Temperature dependence; Temperature metrology; Time measurement; Velocimetry
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/5.0241114

We studied the shock-induced collapse of butane gas bubbles in the homogeneous explosive nitromethane (NM) to investigate the effects of hot spot formation on the detonation process. A butane bubble was injected into a sample of NM, and a shock wave from a flat plate impactor compressed the bubble, creating a localized hot spot. We measured shock and detonation wave speeds with optical velocimetry, and we used a high-speed camera to image the shock propagation and bubble collapse processes. A multiband optical fiber pyrometer measured the time-resolved thermal radiance, and we used the results and emissivity values extracted from spectral fits to estimate temperatures. We measured the characteristics of the shock-to-detonation transition in NM with and without a bubble. All experiments were performed at shock pressures near 8 GPa, where neat NM can detonate. A single bubble in this system was shown to sensitize NM, leading to a reduced run-to-detonation time. We used hydrodynamic modeling to predict shock wave propagation, the extent of chemical reaction, and subsequent temperature rise from the collapsing bubble. We used a temperature-dependent Arrhenius burn model for simulations, and it yielded much better results than reactive burn models that depend only on pressure and density.