RU2390872C1 - Thermionic generator - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: thermionic generator includes current leads (16), cathode with heat supply devices (7) and perforated anode (12) with heat discharge devices, which are separated with an interelectrode gap (8), supply system of cerium steam through holes in anode (10) to interelectrode gap (8). Supply system of cesium steam through holes in anode (10) to interelectrode gap (8) is formed with perforated anode (12), capillary-porous gasket (6) soaked with cesium alloy and anode substrate (13), which are all connected to each other. At least some part of holes (10) in anode is arranged above heat-insulating gaskets (14) arranged on anode substrate (13). In particular cases of device version the distance between holes in perforated anode (12) is 0.7-4 of thickness of interelectrode gap (8), and size of holes in perforated anode (12), which are located above heat-insulating gaskets (14), is at least twice as small than holes in perforated anode (12), which are arranged outside heat-insulating gaskets (14).

EFFECT: increasing efficiency of energy conversion and improving compactness of device.

3 cl, 2 dwg, 1 ex

Description

The invention relates to the field of conversion of thermal energy into electrical energy and can be used in the power generating elements of a power plant.

Known thermionic electricity generating channel (EGC) of the active zone of a nuclear reactor (Gryaznov G.M., Pupko V.Ya. TOPAZ-1 - Soviet space nuclear power plant. Nature, 1991, No. 10, p.29-36). An EGC of a nuclear reactor core contains series-connected power generating elements containing heat sources in the form of a fuel rod, the shells of which are cathodes, and separated from them by an annular gap of the anodes, through insulating gaskets connected to an EHC housing cooled by a liquid metal coolant, in which an annular gap between the anode and the cathode is washed with cesium vapor supplied from a cesium thermostat from one end of the EGC and discharged into the environment at the other end of the EGC.

The disadvantages of such a device are:

- flow diagram of the circulation of the working fluid EGC - cesium;

- relatively low energy conversion efficiency.

The closest in technical essence to the claimed device is a thermionic converter described in US patent No. 5578886, date of publication of the patent 02/18/1993

The known technical solution contains a heated cathode, separated from it by a gap filled with cesium vapor, a cooled anode, and the anode has at least several openings through which cesium vapor is supplied from the cesium thermostat into the gap.

The disadvantages of this solution are:

- the presence of an external circuit for the circulation of cesium vapor;

- supply of cesium to the holes of the anode in the vapor phase through the channels from the heat removal means;

- reduced efficiency of energy conversion due to overheating of cesium vapor relative to the saturation temperature when passing through the supply channels.

The authors were faced with the task of eliminating these drawbacks, namely, the creation of a thermionic converter with greater conversion efficiency due to intensive microcirculation of cesium vapor in the interelectrode gap, supplying cesium to the holes in the anode in the liquid phase, and supplying cesium vapor through holes in the anode from the state corresponding to the line saturation at anode temperature.

To solve this problem, in a thermionic emission converter containing current leads, a cathode with heat supply means and a perforated anode with heat removal means separated by an interelectrode gap, a cesium vapor supply system through openings in the anode to an interelectrode gap, a cesium steam supply system through openings in the anode to an interelectrode gap clearance offered:

- form a cesium vapor supply system through the holes in the anode into the interelectrode gap to form a perforated anode interconnected, a capillary-porous pad impregnated with cesium melt, and the anode substrate, and at least a part of the anode holes should be placed over heat-insulating spacers placed in the anode substrate.

In special cases it is proposed:

- the distance between the holes in the perforated anode is chosen in the range from 0.7 to 4 thicknesses of the interelectrode gap;

- the size of the holes in the perforated anode located above the heat-insulating gaskets should be made at least half the size of the holes in the perforated anode placed outside the heat-insulating gaskets.

The technical results of the invention are improving the energy conversion efficiency due to the approach of the cesium vapor parameters in front of the holes in the anode to the parameters corresponding to the saturation line;

- increasing the compactness of the device due to the lack of external sources of cesium vapor to ensure its circulation.

The invention is illustrated by figures, in which Fig. 1 shows the structure of a thermionic converter, and Fig. 2 is a longitudinal axial section of a particular embodiment of a thermionic converter of cylindrical geometry.

In figure 1 and figure 2 the following notation:

1 - inlet window of the gas-air mixture, 2 - spacer, 3 - ignition device, 4 - insulating gasket, 5 - gas furnace chamber, 6 - capillary-porous gasket, 7 - cathode with heat supply, 8 - interelectrode gap, 9 - window combustion products, 10 - holes in the anode, 11 - pipe for evacuation and inlet of cesium vapor, 12 - perforated anode with heat dissipation, 13 - anode substrate, 14 - heat-insulating gaskets, 15 - thermal insulation, 16 - current leads, 17 - flanges .

The thermionic converter contains current leads 16, a cathode with heat supply means 7 and a perforated anode with heat removal means 12, separated by an interelectrode gap 8, a cesium vapor supply system through holes 10 in the perforated anode 12, into an interelectrode gap 8 formed by interconnected perforated anode 12, a capillary-porous pad 6 impregnated with cesium melt and anode substrate 13, with at least a portion of the holes 10 of the perforated anode 12 being placed above the heat-insulating spacers 14, p located in the substrate of the anode 13. The distance between the holes 10 in the perforated anode 12 is 0.7-4 of the thickness of the interelectrode gap 8. The size of the holes 10 in the perforated anode 12 located above the insulating spacers 14 is at least half the size of the holes 10 in perforated anode 12, placed outside the insulating gaskets 14.

The device operates as follows.

The working process is carried out by supplying heat to the cathode 7 from means of heating it (for example, by radiation and convection from a burning gas-air mixture in the furnace chamber) with heating it to a temperature in the range 1100-1300 ° C under conditions of heat removal from the anode 12 by means of its cooling (for example , heat pipe or thermosiphon) at a temperature of 250-500 ° C. In the indicated temperature regime, a spotted structure of the temperature field of the capillary-porous strip 6 is established — under the holes 10 in the perforated anode 12 with heat-insulating spacers 14, the temperature is higher than under the holes 10 without heat-insulating spacers 14. As a result, cesium melt is intensively evaporated from the capillary-porous gasket 6 and its steam entering through openings 10 in the perforated anode 12 above the heat-insulating spacers 14 into the interelectrode gap 8 and condensation of cesium vapor coming from m the electrode gap 8 through the holes 10 of the perforated anode 12 located outside the heat-insulating spacers 14, on the capillary-porous gasket 6. Due to capillary forces, cesium condensate flows over the capillary-porous gasket 6 from the holes 10 in the perforated anode 12 without heat-insulating spacers 14 to the holes 10 in a perforated anode 12 with heat-insulating gaskets 14. In the interelectrode gap 8 a system of multidirectional cesium vapor flows is formed, which forms convective microcirculation cells. The criterion for the stable formation of microcirculation cells is the ratio of the step between the holes 10 of the perforated anode 12 with opposite directions of cesium vapor flow to the thickness of the interelectrode gap 8. With a ratio of the indicated sizes in the range 0.7-1.4, convective microcirculation cells of the first order are formed (one vortex zone, shown in figure 1), with a ratio in the range of 2.5-4.0 - second order (three vortex zones). With an increase in the order of microcirculation cells, the cesium vapor velocity rapidly decreases due to dissipative processes, therefore, their use is impractical.

An example of a specific implementation of the device

The cathode 7 is made of heat-resistant steel EP 747, a layer of a substance emitting electrons is deposited on its surface from the side of the perforated anode 12. The perforated anode 12 is made of nickel foil with slit openings 10 of a width of 0.1 mm and 0.3 mm, placed on a capillary-porous strip 6 of a stainless twill mesh impregnated with cesium melt. From the side of the cathode 7, an electron absorbent coating is applied to the surface of the perforated anode 12. The capillary-porous gasket 6, in turn, is connected to the substrate of the anode 13, made of stainless steel, in which from the side of the perforated anode 12 there are samples for heat-insulating gaskets 14, located opposite the part of the holes 10 in the perforated anode 12, made of aluminum oxide. The width of the slotted holes 10 above the insulating gaskets is 14-0.1 mm, outside them 0.3 mm.

A special case of device execution

A special case of a thermionic converter in a cylindrical geometry is shown in FIG. 2. The device comprises a tubular cathode 7 and a perforated tubular anode 12 separated from it by an interelectrode gap 8, located on the tubular substrate of the anode 13. The tubular cathode 7 and the anode substrate 13 are provided with flanges 17 with a non-metallic insulating gasket 4, which rigidly fixes the value of the interelectrode gap 8 in azimuth in the upper parts of thermionic converter. In the lower part of the thermionic converter, the magnitude of the interelectrode gap 8 is fixed by the spacer 2 with the possibility of axial movement of the cathode 7 relative to the substrate of the anode 13. The current flowing through the interelectrode gap 8 along the walls of the tubular cathode 7 and the substrate of the anode 13 is discharged to the flanges 17 and then through the current leads 16 to the consumer . As a means of supplying heat to the cathode 7, a gas-flame furnace is used, including thermal insulation 15 surrounding the chamber of the gas furnace 5, in which the active part of the thermionic generator is placed. In the thermal insulation 15, an inlet window of the gas-air mixture 1 and a window for discharging the products of combustion 9 are made. The gas-air mixture is ignited by the ignition device 3. Heat is removed from the anode substrate 13 by a thermosyphon formed by the internal cavity of the anode substrate 13.

The device operates as follows.

When gas-air mixture is combusted in the chamber of the gas furnace 5 by radiation and convection of combustion products, the surface of the tubular cathode 7 is heated to a temperature of 1100-1300 ° C with simultaneous heat removal from the anode substrate 13 by boiling the thermosiphon working substance at a temperature of 250-500 ° C. The emission current flowing through the interelectrode gap 8 along the walls of the cathode 7 and the substrate of the anode 13 flows to the flanges 17 and then is fed to the consumer via current leads 16.

According to experimental data, overheating of cesium vapor entering the interelectrode gap relative to the saturation line reduces the energy conversion efficiency in the thermionic converter with a rate of 1-2% / 10 ° C. The claimed technical solution provides minimal overheating of cesium vapor relative to the saturation line due to the maximum reduction in the length of the vapor path from the evaporation surface to the interelectrode gap, therefore, it provides maximum efficiency for converting thermal energy into electrical energy.

Using the invention allows to create a thermionic converter with increased efficiency of converting thermal energy into electrical energy (up to 20%), improved weight and size characteristics and reduced cost.

Claims (3)

1. A thermionic converter containing current leads, a cathode with heat supply means and a perforated anode with heat removal means, separated by an interelectrode gap, a cesium vapor supply system through openings in the anode and an interelectrode gap, characterized in that the cesium steam supply system through openings in the anode has the interelectrode gap is formed by interconnected perforated anode, a capillary-porous pad impregnated with cesium melt, and the anode substrate, and at least part of the anode openings eschena over the insulating spacers placed in the anode substrate. 2. The device according to claim 1, characterized in that the distance between the holes in the perforated anode is 0.7-4 of the thickness of the interelectrode gap. 3. The device according to claim 1, characterized in that the size of the holes in the perforated anode located above the insulating gaskets is at least half the size of the holes in the perforated anode located outside the heat-insulating gaskets.

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