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Explosives for Industrial Underwater Blasts

#KR-899


Novel Efficient Metal-Containing Energetic Materials for Underwater Explosions in Industry

Tech Area / Field

  • MAT-EXP/Explosives/Materials

Status
8 Project completed

Registration date
20.06.2002

Completion date
17.05.2006

Senior Project Manager
Libby M D

Leading Institute
Kyrgyz-Russian Slavonic University, Kyrgyzstan, Bishkek

Supporting institutes

  • Russian Academy of Sciences / Semenov Institute of Chemical Physics, Russia, Moscow

Collaborators

  • Université de Poitiers / Laboratoire de Combustion et de Détonique, France, Futuroscope\nSNPE Group/SNPE Propulsion/Le Bouchet Research Center of SNPE Group, France, Vert-le-Petit\nKrispin Technologies, Inc., USA, MD, Rockville

Project summary

The main objective of the project is to study underwater explosions of heterogeneous solid metal fuel – solid oxidizer mixtures enriched with metal. The reaction is initiated in an injector and the burning material (or combustion products) is injected in water to achieve its rapid mixing with water. Elucidated will be peculiarities and basic features of burning of the energetic material within the injector and interaction of the jet material with water. The results of experimental study and computer modeling will be used to suggest recommendations on the use of heterogeneous metallized energetic materials in practice.

Implementation of the formulated tasks implies conducting many explosions. Safety of the working personnel will be guaranteed at all the stages of the work with energetic materials: transport, storing and explosion tests proper, including destruction of the products of tests. The safety measures are based on “Unified safety regulations of explosion works” approved by the State Technical Inspection (GOSTEKHNADZOR) of the Kirgyz Republic and State Technical Inspection of the Russian Federation. All the personnel dealing with energetic materials passed State attestation that permits them to perform explosion works and is confirmed by the Unified Certificates of Explosion Workers. In compliance with the aforesaid Regulations all the experimenters dealing with energetic materials are instructed before each set of runs by the supervisors responsible for safety of works, the fact of this instruction is fixed in a special book by the personnel signatures. All the participants of explosion tests have health certificates indicating that they are allowed to deal with energetic materials.

At present two basic types of energetic materials are used to generate blast waves in various media: (i) condensed detonating high explosives (HE) which, being initiated, release their energy in a small volume to produce high-amplitude quickly decaying compression waves and (ii) and fuel-air mixtures (FAE) generating longer low-amplitude blast waves. Energetic materials exhibiting the properties of both HE and FAE would suite much better the requirements imposed by the majority of practical applications of explosive materials. Fuel-rich mixtures of a solid oxidizer and metal powders reacting in a regime of convective burning or low-velocity detonation are the best materials meeting the requirements of practice because their specific energy is normally higher than that of HE, the pressure build-up in the course of their explosion is such that many metal constructions would survive without destruction, and the pressure pulses produced by these explosions are even longer than in the case of FAE and their amplitude is intermediate between blast waves generated by HE and FAE (from several tens of kilobars to few tens of bars). The hot combustion products of heterogeneous mixtures are capable of releasing additional heat when mixed with an oxidizing surrounding (air or water).

From the standpoint of specific energy and cost aluminum – ammonium nitrate (or ammonium perchlorate) mixtures are the best candidates to be used as energetic materials for “mild” explosions.

The use of underwater explosions in solving technical problems often imposes specific requirements on the parameters of compression waves that can not be provided by conventional HEs. Breaking of ice, generation of pressure pulses in seismic exploration, seam fracture to enhance oil well yield, cleaning clogged wells, stamping and forming sheet materials, hydrostatic pulse pressing and compacting of powdered materials are among these applications. They require explosives producing compression waves not destroying equipment with a readily controllable pulse duration ranging from tens of microseconds to several tens of milliseconds, generating much gas, and save for underwater fauna (that is, lacking a negative phase). Furthermore, energetic materials must be save in handling and storing and cheap.

Aluminum is known to readily react with water releasing much heat, steam and hydrogen. Experiments performed by the authors of the project with small Al-rich charges fired in an injector under water have demonstrated that charges generate pressure waves under water with an amplitude of several hundreds of bars, pressures above the water surface is below 100 bar. Experiments clearly show that all the excess metal reacts with water to generate a cloud of bubbles in water. Bubbled water moves at a velocity of about 150 m/s and produces a pressure pulse exceeding 1 kbar at its maximum and lasting about 10 ms when impinges the upper tube flange. Thus metal-rich heterogeneous energetic materials exhibit properties that meet virtually all the above-mentioned requirements and hence, are nearly ideal energetic materials to be used in all the above-listed applications.

Further intense studies of performance of metallized mixtures under water are needed to ascertain the scaling effect, jet structure, mixing and reaction rate, the effect of metal concentration, and the state and structure of the discharged water-gas mixture, that is to gain data needed to design various pressure-pulse generators. Apart from scrutinizing fundamental aspects of the jet generation and interaction between the jet material and water, which are very poorly studied, we intend, within the project, to recommend how to apply these energetic materials in various practical situations and even to design model pressure-pulse generators. The particular studies would be aimed at development of generators for oil wells, for ice breaking, for surface and underwater seismic exploration, and hydrostatic compaction of materials. It should be emphasized that the suggested energetic materials have nothing to do with explosives of dual application, because they are not detonable.

The problems to be solved to hit the target are:

1. To study the internal ballistics of injectors in a constant volume bomb (to measure the pressure rise rate and burning wave velocity), including the effect of the initial pressure, temperature, charge composition and porosity on the measured parameters; to ascertain the mechanism of convective burning of metal-oxidizer-liquid component mixtures with the purpose of gaining data needed to search for and optimization of compositions to be applied under different conditions.

2. To investigate burning of an excess metal component injected in water at atmospheric pressure, including jet mixing with water and to gain data needed to find optimal designs of injectors capable of solving the formulated practical problems.

3. To achieve efficient performance of the injectors and energetic materials at elevated pressures (up to 140 bar) and to ascertain the effect of charge properties and initial conditions on the reaction of the injected heterogeneous material with water under conditions simulating real situations.

4. To numerically simulate compression pulses generated by new energetic materials fired in injectors of various designs and under various conditions.

5. To scrutinize the dynamics of motion of a bubbled liquid accelerated by the jet reaction with water and its reflection from rigid surfaces.

6. Based on the gained data, to develop a numerical code simulating all the stages of the process taking place in various scenarios of injector application.

7. To design and manufacture model pressure pulse generators for every of the above-formulated particular applications and to formulate recommendations for designing practical devices.

8. To develop, based on the results of laboratory investigations, a numerical model predicting pressure pulse impact on the real surrounding needed to plan full-scale tests and design generators to be applied in practice.

Investigations will involve measurements of burning velocity of materials in constant volume bombs, pressure recording both in water, above water surface, and in accelerated bubbled liquid, photographing jet penetration in water and motion of bubbled liquid, X-ray flash photography of the jet structure. All the equipment needed for studies is available.

To sum up, the study is aimed at developing new efficient ecologically safe energetic materials and injectors capable of producing pressure pulses ranging from tens of kilobars to tens of bars and lasting from tens of milliseconds to hundreds of microseconds with easily controllable parameters (shape, duration, and amplitude) to meet requirements of many practical applications (seismic exploration, enhancing oil-well yield, compacting powders, ice breaking, explosion stamping) and to achieve charge performance not accessible to conventional high and commercial explosives.


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