RU2707557C1 - Thermionic transducer built into the structure of high-speed aircrafts - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to the field of thermionic conversion of heat energy into electrical energy, namely to thermionic transducers (TIT), which can be used in thermal protection systems and onboard electric power sources of hypersonic aircrafts (HAC). Purpose of this TIT is to generate electric power combined with efficient cooling of HAC structural elements, such as leading edges of wings, steering surfaces etc. Thermionic converter built into the high-speed aircraft structure includes the emitter and the collector arranged in the form of pipes and sealed on both sides and arranged inside the collector at their mutual electric and thermal decoupling. External surface of the emitter pipe has a heat-resistant coating, for example molybdenum disilicide. Collector pipe is equipped with one or more current collectors and one or more inlet / outlet branch pipes of the collector cooling circuit. Current leads and branch pipes are connected to the lateral surface of the collector pipe, are located within the limits of one semicircle and are equipped with the sealed leads, respectively. Note here that every sealed lead comprises cermet and bellows assemblies. As heat carrier in cooling circuit of collector there can be used fuel of aircraft engine, at that for matching of allowable temperature of this fuel with temperature of collector inner surface of collector is equipped with heat-insulating material. Cooling circuit of the collector can be made in the form of evaporation section of the T-shaped heat pipe.

EFFECT: higher reliability of thermal protection and onboard HAC electric power sources.

6 cl, 2 dwg

Description

The invention relates to the field of thermionic conversion of thermal energy into electrical energy, in particular to thermionic converters (TEC), which can be used as part of thermal protection systems and on-board sources of electrical energy of hypersonic aircraft (GLA). The purpose of this TEC is to generate electricity in combination with efficient cooling of GLA structural elements, such as leading edges of wings, steering surfaces, etc.

There is a known scheme of a thermionic converter with semicylindrical coaxial electrodes embedded in the leading edge of the GLA wing in such a way that the external surface of the emitter is subjected to aerodynamic heating (A. V. Kolychev. “Active thermal protection of structural elements of a hypersonic aircraft based on new physical principles during aerodynamic heating”. The electronic journal “Transactions of MAI”, issue No. 51, UDC 629.782, www.mai.ru/science/trudy). Changing the current in the TEC electric circuit allows you to control the intensity of electronic cooling of the wing edge, and the electricity generated by this is used for onboard needs of the GLA.

The known circuit did not find technical implementation, since it is impossible to provide sealing of the interelectrode gap around the perimeter of electrodes of a semicylindrical shape during their thermal and electrical isolation.

To date, in technically feasible and promising designs of TEC, only cylindrical coaxial or plane-parallel electrodes are used.

The closest in technical essence to the claimed invention is a thermionic converter with coaxial cylindrical electrodes, with an external location of the emitter heated by a flame (Ushakov V.A., Nikitin V.D., Emelyanov I.Ya. Fundamentals of thermionic energy conversion. M, Atomizdat, 1974, pp. 131-132). The coaxial cylindrical electrodes of this TEC are made in the form of cups with a hemispherical bottom inserted one into the other when they are mutually electrically and thermally decoupled using a pressure seal containing a ceramic-metal assembly. The emitter made of tungsten is heated from the side of its bottom, and the collector is cooled from the opposite side by a heat pipe.

However, this device, taken as a prototype, cannot be used as part of thermal protection systems and on-board electric power sources of the GLA for the following reasons:

- the geometry of the outer surface of the emitter and the relative position of the components of the TEC does not correspond to the shape of the structural elements of the GLA subjected to the most intense aerodynamic heating, such as the leading edges of the wings, steering surfaces, etc .;

- a tungsten emitter under hypersonic flight conditions (heating in the atmosphere to temperatures above 1300 ° C) will be destroyed by intense gas corrosion;

The objective of the invention is to develop the design of the TEC, suitable for use as part of thermal protection systems and on-board sources of electric energy of the GLA.

The problem is solved due to the fact that in a thermionic converter with an emitter made in the form of pipes and a cooled collector placed inside it during their mutual electrical and thermal isolation using at least one pressure seal containing a ceramic-metal assembly, the emitter and collector pipes according to the invention sealed on both sides, a heat-resistant coating is created on the outer surface of the emitter pipe, the collector pipe is equipped with one or more current outputs and one or more inputs GOVERNMENTAL / output collector pipes of the cooling circuit, wherein the cold ends and the pipes are located on the side surface of the manifold pipe within a semicircle and each provided with cable glands them arranged comprising in its composition bellows assemblies.

In particular cases of the invention:

- the emitter is made with a wall thickness variable along its circumference, which is selected from the condition of uniformity of the density value of the azimuthal heat flux along this circle;

- the aircraft engine fuel is used as a coolant in the collector cooling circuit, and for matching the permissible fuel temperature with the temperature of the collector, the inner surface of the collector and the inlet / outlet pipes of the cooling circuit are covered with insulating material;

- the collector cooling circuit is made in the form of an evaporation section of a T-shaped heat pipe;

- molybdenum is selected as the material of the emitter;

- as the material of the heat-resistant coating, molybdenum disilicide was selected.

The invention is illustrated using the figures of graphic images.

In FIG. 1 shows a diagram of a GLA TEP wing embedded in the front (in the direction of flight) wing, in which fuel for the GLA engine can be used as a coolant to cool the collector. The collector 1 is made in the form of a round pipe sealed on both sides and placed inside the emitter 2. The emitter 2 is made in the form of a pipe sealed on both sides with a displaced longitudinal hole and provided with a heat-resistant coating 4. An electrode gap between the collector 1 and the emitter 2 is provided by remote control 3. Within one semicircle of the collector 1, perpendicular to the longitudinal axis of the collector 1, its current leads 5 are placed and the input / output pipes 6 of the collector cooling circuit for the cooling fuel pumping direction is indicated by arrows. Thermal and electrical isolation of the TEC electrodes in the region of the indicated current leads 5 and nozzles 6 is realized with the help of pressure glands consisting of bellows assemblies 7 and cermet assemblies 8. Tires for current collection from both electrodes are conventionally shown with the signs “+” and “-”.

In order to provide the possibility of direct cooling of the collector with fuel for the GLA engine, the inner surface of the collector 1 and inlet / outlet pipes 6 are coated with a material 9 with low thermal conductivity to match the permissible temperature of the fuel with the temperature of the collector. The heat entering the collector 1 is absorbed due to the heat capacity of this fuel pumped inside the collector and then entering the GLA engine. As a result, the collector is cooled to its optimum temperature of 600-700 ° C. This temperature may be unacceptable for fuel (for example, coking of aviation kerosene occurs at temperatures above -400 ° C). Therefore, limiting the increase in temperature of the cooling fuel to within acceptable limits is provided by the coating 9, which is applied to the inner surface of the collector and the inlet / outlet pipes of the cooling circuit. As materials for coating 9 use a material with low thermal conductivity, preventing direct thermal contact of the fuel with the surface of the collector 1 and the input / output pipes 6 of the cooling circuit.

In FIG. 2 shows a diagram of a GLA TEP built into the wing edge, in which the cooling circuit of collector 1 is made in the form of an evaporative section of a T-shaped heat pipe 10 with a wick. Positions 1 to 8 in FIG. 2 denote the same structural elements, respectively shown in FIG. 1. The direction of movement of the steam of the working fluid in the heat pipe 10 is shown by an arrow. The heat entering the collector 1, which is essentially combined with the evaporative portion of the heat pipe, is removed by the pipe 10 to the elements of the GLA structure that are less heated by the aerodynamic flow (for example, to the aerodynamic surfaces near their trailing edges) and then they are radiated into the surrounding space.

Thermionic Converter, built into the design of high-speed aircraft, operates as follows.

During the flight, the emitter 2 of the TEC installed in the GLA from the side of the wing edge is heated by braking of the hypersonic aerodynamic flow to ~ 1500 ° C. The thermal energy received by emitter 2 is partially converted into electrical energy with efficiency ≤20%, and the rest through electron cooling, thermal radiation and due to the thermal conductivity of the interelectrode medium enters the collector 1, and also due to the thermal conductivity of the material spreads around the circumference of the emitter 2 on its unheated side. Placement of pressure glands for collector current outputs and inlet / outlet pipes within the same emitter semicircle, located on the opposite side of the TEC side with respect to the GLA flight direction, excludes the effects of hypersonic flow on these structural elements. The bellows assemblies 7, which are part of the pressure glands, eliminate mechanical stresses arising from thermal deformations.

Performing an emitter with a wall thickness that is variable around its circumference, which is selected from the condition that the density of the azimuthal heat flux is uniform over this circle, helps to equalize the temperature of the emission surface, thereby reducing the negative effect of uneven heating of the emitter on the efficiency of the TEC. A change in wall thickness can be obtained by displacing a longitudinal hole in the emitter pipe relative to its center in the direction of the unheated side of the circumference of the emitter pipe.

Thus, the solution of the problem is provided by the selected shape of the TEC electrodes, the relative position of the elements of its structure, the presence of a heat-resistant coating on the outer surface of the emitter.

The implementation of the invention.

In a thermionic emission transducer, a tubular emitter with an internal diameter of ~ 15 mm is made of a refractory material, for example, molybdenum, which is protected externally from high-temperature gas corrosion by a silicide coating 0.1-0.15 mm thick and has a tungsten emission coating on the inside. The collector is made in the form of a round pipe sealed on both sides of niobium, nickel or stainless steel with a diameter of ~ 13 mm and a length of ~ 500 mm, and placed inside the emitter. The interelectrode gap between the emitter and the collector (MEZ) is provided by a belt of six spacers for each ~ 100 mm of electrode length. Within one semicircle of the collector pipe, perpendicular to the longitudinal axis of the collector, current leads are arranged (one for each ~ 100 mm of the pipe length) and two pipes of the collector cooling circuit for cooling fuel are connected, the pumping direction of which is shown by arrows in FIG. 1. Thermal and electrical isolation of the TEC electrodes in the region of the indicated current leads and branch pipes is realized with the help of pressure glands consisting of bellows assemblies 7 and cermet assemblies 8. Tires for current collection from electrodes are conventionally shown with the signs “+” and “-”. The collector is cooled by the fuel of the GLA engine. To coordinate the permissible temperature of this fuel with the temperature of the collector, a zirconia dioxide coating with a low thermal conductivity of 1-2 mm thickness is applied to its inner surface.

In the case of cooling the collector using a medium-temperature (e.g., sodium) heat pipe, current outputs (one for each ~ 100 mm of the pipe length) are placed within one semicircle of the collector pipe perpendicular to the longitudinal axis of the collector and a collector cooling pipe is connected. The capillary structure of the heat pipe is formed on the inner surface of the collector pipe and the pipe of the cooling circuit in the form of many longitudinal grooves with a characteristic size of ~ 0.5 mm. Hermovods of collector current leads and cooling pipes consist of steel bellows and cermet units with insulators of aluminum oxide (including monocrystalline) and cuffs of nickel alloys.

Claims (6)

1. Thermionic converter integrated in the design of a high-speed aircraft, with an emitter made in the form of tubes and a cooled collector placed inside it when they are electrically and thermally isolated using at least one pressure seal containing a ceramic-metal assembly, characterized in that the emitter and the collector pipe are sealed on both sides, a heat-resistant coating is created on the outer surface of the emitter pipe, the collector pipe is equipped with one or more current output and one or more inlet / outlet nozzles of the collector cooling circuit, while the current leads and nozzles are located on the side surface of the collector pipe within the same semicircle and are equipped with corresponding hermetic inlets containing bellows assemblies. 2. The thermionic converter according to claim 1, characterized in that the emitter is made with a wall thickness that is variable along its circumference, which is selected from the condition of uniformity of the density value of the azimuthal heat flux along this circle of the emitter. 3. The thermionic converter according to claim 1, characterized in that the inner surface of the collector and inlet / outlet nozzles is coated with heat-insulating material, and the aircraft engine fuel is used as a coolant in the collector cooling circuit. 4. The thermionic converter according to claim 1, characterized in that the collector cooling circuit is made in the form of an evaporation section of a T-shaped heat pipe. 5. The thermionic converter according to claim 1, characterized in that molybdenum is selected as the material of the emitter. 6. The thermionic converter according to claim 1, characterized in that molybdenum disilicide is selected as the material of the heat-resistant coating.

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