RU2611037C1 - Method of fog dissipation - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: inhomogeneous electric field affects the air flow moving in the direction of the object that needs to be protected from the fog. Influence is made by the an alternating electric field, resulting from applying an alternating voltage to an electrode electrically insulated from the air flow.

EFFECT: reduction in energy costs for the drop separation and dispersion of mist.

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Description

The invention relates to the field of technology intended for the separation of liquid droplets from fog, and can be used to disperse fog over a controlled area. These are, first of all, airfields, high-speed roads, seaports, etc., where to control vehicles it is necessary to ensure the range of visibility, as well as open areas for various sports and entertainment events. In addition, the technical solution can be used to obtain water from moving waterlogged air masses of air, as well as to clean the gas streams emitted into the atmosphere from liquid droplets contained in them.

A number of technical proposals are aimed at solving the problem of artificial fog dispersion. US Pat. No. 2,160,900, publ. 06/06/1939, No. 2934275, publ. 04/26/1960, No. 2527230, publ. 10/24/1950, methods for dispersing mists based on artificial condensation of water vapor by using special substances and reagents are presented. However, these methods for dispersing warm mists have not found practical application.

During World War II in England, a thermal fog method called FIDO was used to disperse fog over airfields. Heat was generated during the burning of oil or fuel oil in burners installed on long pipelines along the runway. Heat flows provided dispersion of fog over the airfield. See, for example, http://www.youtube.com/watch/v=gAIjxaJ2_Ag. This method has not found wide application due to the high cost of operation. It took several hundred thousand liters of fuel to disperse the fog per hour. A known method of thermal dispersion of fog, which in addition to the thermal effect on the fog used the kinetic energy of the heat stream. See, for example, US patent No. 2 969920, publ. 01/31/1961, US patent No. 3712542, publ. 03/15/1971 This method also required significant energy resources.

Known methods of electrical exposure to the atmosphere. So, in US patent No. 4671805, publ. 06/09/1987, a method for dispersing fog using an ion cloud is described. NASA's 3481 report from 1981 (see http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19820008785_1982008785. Pdf) presents research on the creation of ion generators. However, the practical application of ion generators for dispersing fog is not presented in published sources.

A known method of dispersing fogs and clouds, which consists in generating electric charges into the atmosphere by connecting corona wires to the high voltage source, fixed through insulators on supports at the surface of the earth (see Journal of Geophysical Research, Cambridge, Massachusetts, March, 1962, t. 67, pp. 1073-1082). Information about this method is reflected in the domestic technical literature (see L. G. Kachurin. Physical fundamentals of exposure to atmospheric formations. L., Gidrometeoizdat, 1978, pp. 287-293). Work on the testing of this method, conducted with the participation of the authors, showed that dispersion of fog by this method has a statistically significant result (see VB Lapshin, A. A. Paley. Results of field experiments to assess the effect of corona discharge on fog density. Meteorology and hydrology, 2006, No. 1, pp. 41-47).

The closest technical solution to the proposed technical solution is a method and device for dispersing fog according to patent RU No. 2534568, publ. November 27, 2014. A known method is that they determine the direction of propagation of the fog relative to the protected object. Then, an inhomogeneous electric field is formed on the side windward from the protected object in the fog region adjacent to the grounded surface of the fog region. The field is formed by applying an electric potential to the surface of the electrode. In this case, the electrode is made in the form of a shell with a smooth surface, with a radius of curvature of not less than zero. The electrode is mounted equidistantly with a gap through the dielectric gasket relative to the grounded capacitor plate. In a known technical solution, an electrically charged electrode forms an inhomogeneous electric field in the surrounding space. The energy of the generated electric field provides polarization of the droplets of fog in the surrounding space and, due to its inhomogeneity, carries out the movement of polarized droplets in the direction of increasing the gradient of the electric field to the electrically charged electrode. Having reached an electrically charged electrode, the droplets of fog get an electric charge and are pushed to the grounded surface by electric lines (see, for example, WD Ristenpart, J.C. Bird, A. Belmonte, F. Dollar, HA Stone. Non-coalescence of oppositely charged drops. NATURE, Vol. 461, 17 September, 2009). Free from droplets of fog, air moves towards the protected object and displaces the fog from the controlled area. This ensures the dispersal of fog in a controlled area at low energy costs compared to methods using a corona discharge to electrically charge the droplets of fog. However, in the known method, energy is wasted on the electric charging of the droplets at the moment the droplets contact the electrically charged electrode.

The aim of the invention is to reduce energy costs for the separation of droplets and, as a consequence, the dispersion of fog.

To achieve the stated goal in the known method of dispersing fog, which consists in exposure to an inhomogeneous electric field on an air stream moving towards an object protected from fog, the effect is carried out by an alternating electric field by applying an alternating voltage to an electrode electrically isolated from the air stream.

The technical result is achieved due to the fact that the proposed technical solution eliminates the possibility of overflow of electric charges from the power source through the electrically insulated surface of the electrode to droplets attracted to it. Due to the fact that the voltage on the electrode is variable, the electric charges move either to the surface in contact with the separated drops, or from it. Electric charges, not having time to reach the surface in contact with the separated drops, after changing the sign of the voltage return back. Fog droplets attracted by the current inhomogeneous electric field to the electrically insulated surface of the electrode do not receive an electric charge, remain on its surface and, as they accumulate, drain into the drainage system under the action of gravity, and the droplet-free air flow moves toward the protected object, displacing fog from the controlled territory.

Implementation of the proposed method is as follows. The boundaries of the area protected from the fog are pre-set. According to long-term observations, streamlines are established along which fog flows onto the protected area, and devices are installed at an acceptable distance from the protected area to ensure the formation of an inhomogeneous electric field. Upon receipt of information about the possible formation of fog, the direction of propagation of the fog relative to the protected object is determined. On the windward side of the protected object, they turn on the power source and apply alternating voltage to the electrode electrically isolated from the air flow. The proposed method does not provide for direct contact of the electrode with a grounded surface. The electrical insulation of the electrode is carried out on the basis of the times of the flow of charges along the possible path of leakage of the charge (the length of the path of leakage) from the electrically charged electrode to the area on the surface of the insulation on which the droplets separated from the air stream are collected. The value of the insulation parameters is determined experimentally depending on the quality of the insulation surface, the frequency of the alternating voltage, the nature of the voltage pulse, etc. As a first approximation, a value of the insulation discharge path of at least 1 cm per 1 KV of the maximum potential difference between the electrode and the ground plane at frequency of an alternating voltage of 50 Hz. To ensure maximum reliability of eliminating the probability of overflow of electric charges, it is necessary to supply an alternating voltage to the electrode electrically isolated from the air flow through a high-voltage cable connected to the electrically insulated electrode using a high-voltage connector. In this case, the overflow of electric charges on the surface of the insulation is excluded, and the overflow of electrical discharges can only be ensured by the so-called bulk conductivity of the dielectric. The choice of dielectric parameters at which the elimination of the flow of electric charges to the outer surface of the insulating layer of the electrode (the surface in contact with liquid droplets) is ensured is a very difficult theoretical problem that can be solved experimentally. In the experiments conducted by the authors of the present invention, when the electrode was connected to an AC voltage source with a frequency of 50 Hz, coating the electrode with an insulating layer of polyvinyl chloride insulation of 3 mm thickness ensured the accumulation of water droplets on the electrode in an artificially formed fog in a fog chamber at the maximum possible value of the applied voltage. A further increase in voltage led to the formation of electric discharges. Thus, when using an industrial frequency AC voltage source for electrical insulation, an insulation layer can be used, the electrical resistance of which at an alternating voltage of industrial frequency is equivalent to the electrical resistance of the polyvinyl chloride insulation layer with a thickness of at least 3 mm. An electric field is formed in the space between the electrically charged electrode and the grounded surface. In order for the generated electric field to be inhomogeneous, it is necessary and sufficient to make the electrode in the form of a convex hull. When the electrode is made in the form of a convex hull, the generated electric field will be inhomogeneous, and the gradient of the electric field will be directed toward the electrode. Drops of fog located in an electric field are polarized and, due to the inhomogeneity of the electric field, are drawn in the direction of increasing its gradient. Thus, electrically neutral droplets of fog are attracted to an electrically charged electrode and are separated from the air stream. Drops of fog remain on the surface of the electrically insulated electrode, and the air stream cleaned from drops of fog moves toward the protected object and forces the fog out of the controlled area. Since the electrode is electrically isolated from the surrounding space, direct contact of the droplets with the electrically charged surface of the electrode is excluded. And since the voltage supplied to the electrode is variable, the overflow of electric charges onto droplets of fog from the electrically charged surface of the electrode over the surface that insulates the electrode from ambient air is eliminated. Thus, the proposed technical solution provides the separation of droplets without flowing electric charge into droplets with their subsequent transfer to a grounded surface, which reduces energy costs and achieve the stated goal. As shown by experimental studies conducted by the inventors, the solution to the problem of eliminating the flow of electric charges to droplets attracted to the electrode at a constant voltage across the electrode is associated with great technical difficulties. To achieve the accumulation of droplets of fog on the electrode when applying a constant voltage to it, the experiments were unsuccessful. In all experiments performed, droplets of fog deposited on grounded surfaces. The electrode always remained dry. When using alternating voltage, the overflow of electric charges is limited to a simple coating of the electrode with a layer of insulating material. The sign of the inhomogeneous electric field acting on the mist drops does not matter. Drops of fog are drawn toward the electrode.

In fig. 1 and in fig. 1a is a schematic diagram of a device that allows implementing the proposed method for dispersing fog. The device includes an electrically conductive, grounded, transparent frame for air flow W that is installed on the surface of the earth; frame 1, made in the form of a set of hollow cells 2, inside each of which with a gap relative to the surface of the frame and electrically isolated, for example, electrodes 4 are mounted on insulators 3 The electrodes 4 are made in the form of a convex shell electrically connected to an AC voltage source 5, covered with a layer of electrical insulation 6.

The device operates as follows.

When applied from an alternating voltage source 5 to a high voltage electrode 4, an electric charge will accumulate on its surface. An electric charge in the space surrounding it forms an inhomogeneous electric field, the value of which is proportional to the magnitude of the charge. An electric field induces an electric dipole moment on the surface of mist droplets. The drops of fog due to the induced dipole moment are drawn in by an inhomogeneous electric field in the direction of increasing its gradient, i.e. to the surface of the electrode 4 and accumulate on the insulation layer 5, covering the surface of the electrically charged electrode 4. Thus, drops of water are separated from the passing air stream through the surrounding electrode. By installing the proposed device on the windward side of the protected object, provides the removal of droplets of fog and their separation from the moving air stream. An air stream free of drops of fog will move to the protected area. The air stream cleared of fog will force the fog out of the controlled area and ensure dispersal of the fog. When changing the direction of wind movement relative to the protected area, those pre-installed devices that are located on the windward side are turned on. Various types of aerodynamic reflectors can be used to clean the fog at a height, which ensures that the air masses cleaned from drops of fog rise to the required height due to the energy of the wind flow. As you know, the electric field is always normal to an electrically charged surface. The execution of the shell with a positive radius of curvature of the surface provides the most remote propagation of the electric field in space from the fog diffuser. Making the surface smooth provides a more even distribution of the energy of the electric field in the space surrounding the shell. Thus, the proposed solution, thanks to new, previously unknown features, allows us to solve the problem of fog dispersion, practically without transferring electric charges to the separated droplets, which allows to reduce the cost of operating costs, to achieve the purpose of the invention.

The invention was created with the support of the Russian Federal Property Fund. Projects No. 14-08-00835, 15-08-04724.

Claims (1)

A method for dispersing fog, which consists in exposing an air stream to a non-uniform electric field moving towards an object protected from fog, characterized in that the exposure is carried out by an alternating electric field by applying an alternating voltage to an electrode electrically isolated from the air stream.

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