Research And Development Of Rock Fragmentation Device By High Voltage Pulse

Rock fragmentation technology has had widespread application in mineral exploitation, oil and gas drilling, geological prospecting, stone machining, tunnel driving, municipal, bridge and culvert, and other areas of the foundation engineering, which is an important part of national economy. With the development of pulsed power technology, its application has been gradually extended from military to civilian industry, which has a wide range of applications now in medcial, environmental protection and blasting. Compared with the traditional methods, Rock disintegration by pulse discharge has a lot advantage such as high efficiency, low power, low energy, no environmental pollution, etc, which has a broad application prospect in rock fragmentation engineering.With the increasingly mature of pulsed power technology and the development of rock disintegration technology by pulse discharge, More and more scholars have researched and developed rock fragmentation device by high voltage pulse. If people want to put rock fragmentation device by pulse on a large scale of engineering application, its life must be increased. So it's particularly important to carry out the research of long life rock fragmentation devices by pulse.In this thesis, we study the basic principles of rock disintegration by pulse discharge through the understanding of the mechanism of rock fragmentation and the current situation of rock fragmentation engineering. We show that the rock fragmentation is caused by pulse discharge and liquid-electric effect, describe the process of rock fragmentation by pulse discharge between two electrode in water, then put forward the basic requirement of the pulse that rock fragmentation required: high enough voltage, fast enough rising edge and enough energy. In order to break some kind of long rod stone, we research and design a pulsed rock fragmentation device which energy stored by Marx generator, that can output pulse front edge less than 500 ns, pulse voltage about 200 k V, single pulse energy about 1000 J, discharge 1-5 times every second.As important energy storage device in the pulsed rock fragmentation device, the pulse capacitor needs to satisfy the requirement of long life time, low inherent inductance and high energy density. Since the polypropylene film' breakdown strength is large and dielectric loss is low, so we adopt oil immersed full-film dielectric as the capacitor dielectric structure for reducing the volume of the capacitor. In this thesis, a capacitor was designed with a capacitance of 90 nF and the inherent inductance is less than 40 nH. According to results of the experiment, the capacitor inherent inductance satisfies the expected requirement. According to life test of the capacitor, the typical failure modes are classified from the dissection of failed capacitors. According to Ansys simulation, the damage mechanism of the capacitor is analysed and an improved design is presented. The life of capacitor increased to more than 106 times charging and discharging. Gas switch has advantages such as high working voltage, high discharge current, short pulse front edge, low inherent inductance, low on-resistance, etc. But its main disadvantages is that life is not too long and repetition rate is not high. We design a kind of long life three-electrode gas switch for the pulsed rock fragmentation device, optimize its structure according to Ansys simulation. It can discharge 106 times in conditions of ±40k V, 20 kA. Trigger circuit is designed and can trigger the first-level switches of Marx generator stably. High-frequency, soft-switch, constant-current, series resonance charging technology is used to charge the capacitors. Discharge electrodes are stainless steel which can adjust the gap and position.In order to simplify the structure of the device and reduce the number of the gas switch, we show a kind of parallel capacitor group discharge circuit through pulse transformer. We Set up a experiment circuit platform and the pulse transformer and the pulse sharpening switch are introduced. According to results of the rock fragmentation experiment, we find out that the pulsed rock fragmentation device which energy stored by Marx generator and the parallel capacitor group discharge circuit both have a good effect of rock fragmentation.