Research On Underwater Explosion Characteristics And Applications Of Fiber Detonating Fuse

With the rapid development of aviation, military and civil blasting technique, the development of low-energy detonating fuse has been widely appreciated. As a new low-energy detonating fuse, fiber detonating fuse has these characteristics: the metal shell as a strong constraint, with strong lateral binding; high density cored; uniform charged dynamite; density of linear charged dynamite is low and detonation occurs steadily with quality assurance; at the same time, the metal shell has a good waterproof performance. In this paper, the author has conducted a comprehensive analysis on the characteristics of underwater explosion with fiber detonating fuse by building an underwater explosion test tower and underwater explosion test system, which reveals its underwater explosion shock wave and the law of bubble pulsation. The author also has studied the application of fiber underwater detonating fuse explosion. In the test, the Hilbert - Huang transform was introduced to analyze the fiber fuse underwater explosion pressure signals and characteristics of the signals. Meanwhile, the underwater explosion optical fiber measurement system was used to explore the law of underwater explosion bubble pulsation. Also, based on the theory of underwater explosions, underwater explosion acoustic characteristics have been studied. And from the study an effective continuous source of acoustic interferencehas been found. The finding is expected to provide a new means of the underwater sound confrontation. The author has put forward that the attenuation produced through underwater explosion of the curtain constituted of fiber fuse underwater explosion bubbles can reach a critical system explosion in the end. Meantime, the explosion energy attenuation effect has been studied. In this paper, within limited water underwater energy test method for fiber fuse underwater explosion was used to measure the explosion parameters, to obtain the energy distribution of fiber fuse explosion, which provides a basis work for the development of fiber detonating fuse. The specific studies have been done as follows:First, based on the analysis of the current problems in the underwater explosion pressure signals, the Hilbert - Huang transform was introduced into the underwater explosion pressure signal analysis, and its applicability was evaluated. Through theunderwater explosive test device, the fiber fuse and fiber explosion explosive fusegrid structure of underwater explosion pressure characteristics have been studied, andthe findings like that the shock wave pressure in the fiber fuse explosion 3μs goesfrom zero to peak pressure 5.21MPa, followed by approximately exponential decay,in the characteristic time decay slowly, and the shock wave pressure signal energy ismainly concentrated in 40KHz, the highest energy is concentrated especially in thefollowing band energy 5KHz and within the first 80μs. The fiber fuse mesh structureis equal to an underwater explosion shock wave generator, the flexibility of which iseasy to select the layout way to form a number of discontinuous shock wave pressure.The signal frequency of the fiber fuse grid structure of the underwater explosionpressure is concentrated within 100KHz, and the signal is particularly obvious whenit is below 50KHz. That is to say, the energy value is much focused which isconcentrated within 100 KHz, and when it is lower than 50 KHz the low energyfrequency is maximum.Second, high-speed photography is used to study the law of explosion bubblesproduced by single or two fiber fuses underwater explosion. The findings is like this:single fiber fuse's first time bubble pulsation remains cylinder-shape, but from thesecond bubble pulsation the shape becomes irregular cylinder; and the first bubblepulsation period is 21.5ms, the second pulsation period of 15.5ms; the maximumradius of bubble pulsation is 5.6cm. However, when two fiber explosion fusesdetonate at the same time, the first bubble pulsation period is 27.5ms, because the twobubbles each inhibit the movement of other bubbles, resulting in the increase ofbubble pulsation period. When the two fuses are laid with 10cm space, the bubblesgradually blend in and finally form a bubble curtain, the duration is very long, whichcan significantly increase the reverberation effect of underwater explosion.Third, to explore the high power, broadband, continuous interference sources ofwater sound, acoustic characteristics based on the theory of fiber fuse underwaterexplosion were studied. Primarily by stress testing and underwater explosion bubblepulsation experiment, the author has studied the fiber cable underwater explosionsound pressure level, sound duration, reverberation effects and characteristics of power spectral. It is found that fiber fuse is of high sound pressure level, of widerange of frequencies, of strong sound reverberation effect and of long duration. Basedon the findings, the author has proposed that the underwater explosion of fiber fusegrid can generate multiple underwater explosion pulses, each pulse can link up well tomake the blast wave a smooth, continuous one. Therefore, the width of underwaterexplosion pulse's pressure wave is increased, and bubble pulsation and reverb effectsis also significantly increased, the duration of underwater explosions is increased, too,which can be used as a continuous sound source of underwater explosions.Fourth, to meet the urgent safety protection needs of underwater blasting, theauthor have studied the attenuation of the compartment air of underwater explosionenergy and found that compartment air can attenuate the peak shock wave pressureeffectively, and the effect of the attenuation can be significantly improved with theincrease of the interlayer air thickness; meantime, the air compartment can attenuatethe underwater explosion shock wave energy of each frequency band and theattenuation effect on most are above 50%.Fifth, drawing lessons from home and abroad in the security measures andtechnologies, based on the bubbles'characteristics of fiber fuse underwater explosion,building fiber fuse grid structure and making full use of the bubble curtain producedby the underwater explosion of the fiber fuse grid structure to reduce the underwaterexplosion energy, the author has proposed the new concept to attenuate explosionenergy through the explosion bubble curtain. Bubble curtain can attenuate the shockwave's peak pressure up to 60%, and attenuate the shock wave impulse as high as62.2%; bubble curtain is also of great attenuation effect to the shock wave energy, upto 57.7%; and bubble curtain has a very good attenuation effect of each band of shockwave energy, in particular, can effectively eliminate the high frequency components.The author has set the principles in bubble curtain attenuating the water shock waveenergy to ensure its ability to achieve the best attenuation.Sixth, the author has analyzed the calculation method of Linear Chargeddynamite's underwater explosion energy, offered calculation method of the fiber fuseunderwater explosion energy, tested the energy of fiber fuse underwater explosion,conducted the systematic research on the energy distribution of underwater explosion, and obtained the exact distribution of the total energy: shock wave energy is about 85%, the bubble is about 15% of total energy. The total energy of explosion fiber fuse conforms; the deviation is just a bit, and shock wave energy is basically about 2.20MJ/kg. The research on the distribution of the fiber fuse explosion energy will promote the development of fiber cable explosion.