RU1828353C - Method for initiating and shaping electric discharge - Google Patents

Abstract

FIELD: handling of heavy-current electric circuits; plasma technology. SUBSTANCE: electrodes are immersed in working fluid contained in discharge chamber whose free space is filled with gas held under pressure. Immersed fluid jet is formed in discharge initiation zone which is perpendicular to electrode axis; this jet provides for generation of gas bubbles in discharge initiation zone. EFFECT: reduced breakdown voltage and time of development of electric discharge. 3 cl, 2 dwg

Description

 The invention relates to electrical engineering and can be used in the development of high-voltage switches of high-current electrical circuits, as well as plasma technology devices and powerful pulsed light sources with an extended glow body.

 The aim of the invention is to reduce the breakdown voltage and the development time of the electric discharge.

 In FIG. 1 shows one of the possible designs in which the proposed method for initiating and forming an electric discharge in a liquid is implemented; in FIG. 2, section AA in FIG. 1.

+

= const, из которого выделим безразмерный параметр число кавитации σ

где Р давление над поверхностью жидкости в камере, Р_кр. давление, при котором возникает кавитация, в данном случае его можно принять равным давлению насыщенных паров жидкости Р_нп. ρ- плотность жидкости, V скорость течения струи жидкости. Согласно экспериментальным данным значение σ≅0,2 можно считать соответствующим кавитационному режиму. Подачу струи жидкости осуществляют вдоль оси нижнего электрода 3 с последующим перпендикулярным поворотом перед выходом из сопла, образованного электродами 2 и 3. Это вызывает завихрение потока жидкости за кромками электродов 2 и 3 и усиливает кавитационные явления в турбулентной зоне вязкого перемешивания. Когда длина l струи достигает необходимой величины, ключом 5 замыкают конденсаторную батарею 6 на электроды 2 и 3. Наличие микропузырьков кавитационного происхождения в пограничной зоне струи, их поляризация в электрическом поле, и разрядные процессы в пузырьках активизируют зажигание разряда, поддерживая его распространение в область низкой напряженности электрического поля. Пробой развивается не по кратчайшему расстоянию между электродами, а в граничной области по огибающей струи, которая становится зоной инициирования разряда. Напряженность электрического поля Е по длине разряда устанавливают больше порогового значения Е_пор. Е Е

, где U амплитуда импульса электрического напряжения; L длина разряда, L Kl при К 2,0-2,5 коэффициенте, учитывающим форму струи.In the chamber 1 are placed coaxially and vertically cylindrical electrodes of the upper 2 and lower 3 (figure 1). The interelectrode gap is an annular nozzle located below the liquid level with which chamber 1 is filled. The necessary interelectrode gap h is provided by moving the upper electrode 2. In the lower stationary electrode 3 there is a cavity 4 filled with the same liquid that the chamber 1 is filled in. In the cavity 4 in a known manner create increased pressure, as a result of which begins the outflow of fluid through the interelectrode gap into the chamber 1. For a horizontal flooded stream of liquid, you can record Bernoulli equation

+

= const, from which we select the dimensionless parameter cavitation number σ

where P is the pressure above the surface of the liquid in the chamber, P _cr. the pressure at which cavitation occurs, in this case it can be taken equal to the pressure of saturated vapor of the liquid P _np. ρ is the fluid density, V is the velocity of the fluid stream. According to experimental data, the value of σ≅0.2 can be considered consistent with the cavitation regime. A fluid stream is supplied along the axis of the lower electrode 3, followed by a perpendicular rotation before exiting the nozzle formed by the electrodes 2 and 3. This causes a swirl of the fluid flow beyond the edges of the electrodes 2 and 3 and enhances cavitation in the turbulent viscous mixing zone. When the jet length l reaches the required value, the capacitor bank 6 is closed with a key 5 to the electrodes 2 and 3. The presence of cavitation microbubbles in the boundary zone of the jet, their polarization in the electric field, and discharge processes in the bubbles activate the ignition of the discharge, maintaining its propagation in the low region electric field strength. Breakdown does not develop along the shortest distance between the electrodes, but in the boundary region along the envelope of the jet, which becomes the zone of discharge initiation. The electric field E along the length of the discharge is set greater than the threshold value E _then. HER

where U is the amplitude of the voltage pulse; L discharge length, L Kl at K 2.0-2.5 coefficient, taking into account the shape of the jet.

15. Разряд в прототипе принимает на дуговой стадии горения форму цилиндра. В описанном устройстве разряд представляет собой тонкую плазменную оболочку, занимающую сектор до 50% площади диска струи.Using this method of forming an electric discharge, it is possible to reduce the threshold voltage by at least 2 times and the breakdown development time by an order of magnitude in comparison with the prototype when forming an electric discharge in industrial water. In addition, it should be noted that in the prototype the discharge length L is approximately equal to the interelectrode gap h, and when implementing the proposed method in the described construction, it can be achieved

15. The discharge in the prototype takes the shape of a cylinder at the arc stage of combustion. In the described device, the discharge is a thin plasma shell occupying a sector of up to 50% of the area of the jet disk.

Claims (3)

1. METHOD FOR INITIATING AND FORMING AN ELECTRIC DISCHARGE between electrodes immersed in a working fluid filling a discharge chamber, including initiation of a discharge by introducing gas bubbles into the discharge initiation zone and subsequent supply of voltage pulses to the electrodes, characterized in that, in order to reduce the breakdown voltage and the time of development of the electric discharge, before the introduction of gas bubbles into the zone of initiation of the discharge, the volume of the discharge chamber free from the working fluid is filled with gas, introducing e gas bubbles are carried out by creating a flooded jet of working fluid in the initiation zone of the discharge directed perpendicular to the common axis of the electrodes, the gas pressure above the surface of the working fluid, the speed of the fluid flow and the amplitude of the voltage pulse are set in the ratios

where P is the gas pressure above the surface of the working fluid, Pa;
v the speed of the flow of the jet of working fluid, m / s;
ρ density of the working fluid, kg / m ³
P _{n p} the saturated vapor pressure of the working fluid, Pa;
U is the amplitude of the voltage pulse, V;
l jet length, m;
E _{p o r} threshold breakdown electric field strength in the working fluid, V / m;
K 2 2.5 coefficient taking into account the shape of the jet.  2. The method according to claim 1, characterized in that the jet of working fluid is carried out along the axis of one of the electrodes, followed by a perpendicular rotation in front of the discharge initiation zone.  3. The method according to claim 1, characterized in that the jet of working fluid is formed in the interelectrode gap, made in the form of a nozzle.