RU2704106C1 - Thermionic transducer for thermionic thermal protection edge of small radius of curve of high-speed aircraft wing - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to the field of thermionic conversion of heat energy into electrical energy, namely, to use of thermionic transducers (TIT) in thermal protection systems of high-speed aircrafts (HSA). According to the invention, in a thermionic converter with cylindrical coaxial cathodes and an anode containing metal-ceramic units for mutual insulation of the cathode and anode and bellows units compensating for the difference in thermal expansions of these electrodes, cathode is made in the form of a tube from refractory metal, streamlined in transverse direction by hypersonic air flow, equipped with heat-resistant coating on the entire external surface and layer of heat insulation on the area of this surface, which is not streamlined by the flow. Anode located inside the cathode is made in the form of a metal rod equipped with input and output gas collectors in the form of internal cavities from opposite ends of this rod, connected by longitudinal micro channels for cooling gas supplied to the inlet gas collector and discharged outside from the outlet gas collector. At that, bellows unit, together with one of two metal-ceramic units located on the side of inlet gas header, is arranged inside HSA, and the second metal-ceramic unit is arranged inside the fairing from heat-resistant material, which contains inner layer of heat insulation.

EFFECT: development of TIT structure built in edge with small radius of wing curvature HSA as thermal-emission thermal protection of this edge.

4 cl, 1 dwg

Description

The invention relates to the field of thermionic conversion of thermal energy into electrical energy, and in particular to the use of thermionic converters (TEC) as part of thermal protection systems of high-speed aircraft (VLA).

Among the structural elements of the VLA, the leading edges of the VLA wings, steering surfaces, etc. are subjected to the most intensive aerodynamic heating by hypersonic free flow. The known scheme of thermal emission thermal protection (TETZ) of such edges, based on the TEC with semicylindrical coaxial electrodes embedded in the edge (AV Kolychev. "Active thermal protection of structural elements of a hypersonic aircraft based on new physical principles in aerodynamic heating." Electronic Journal " Proceedings of the Moscow Aviation Institute ”, issue No. 51, UDC 629.782, www.mai.ru/science/trudy). Changing the current in the electric circuit of such a TEC allows you to control the intensity of electronic cooling of its cathode, subjected to aerodynamic heating, and the electricity generated by this is used for on-board needs.

However, such a scheme is not technically feasible due to the problem of ensuring the sealing of the TEC interelectrode gap along the perimeter of the semicylindrical electrodes during their thermal and electrical isolation. In connection with this problem, in technically feasible and promising TEC designs, only cylindrical coaxial or plane-parallel electrodes are used. In particular, a thermionic converter with coaxial cylindrical electrodes with an external arrangement of an emitter heated by a flame is known (Ushakov V.A., Nikitin V.D., Emelyanov I.Ya. Fundamentals of thermionic energy conversion. M, Atomizdat, 1974, p. 131 -132). The 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 cathode 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, such a device cannot be integrated into the edge with a small radius of curvature of the wing of the VLA due to the mismatch between the geometry of the heated surface of the emitter and the relative position of the components of the TEC to the shape of this edge.

The closest in terms of the most important structural features to the claimed invention is a thermionic electric power generating channel / fuel element (EGC / fuel element) for the Russian-American project of a combined electric motor installation, developed on the basis of a single-element electric power generating channel (EGC) of the TOPAZ-2 thermionic nuclear power plant (Nuclear Power Plant) "(Ponomarev-Stepnoi NN, Nikolaev YV, Gontar AS, at al. Conceptual design of the bimodal nuclear power and propulsion system based on the" TOPAZ-2 "type thermionic reactor-converter with the modernized single-cell thermionic fuel elements. 12th Symposium on space nuclear power and propulsion. Albuquerque, New Mexico, 1995, pp. 755-758.). This EGC was a TEC with cylindrical coaxial electrodes in the form of tubes, the inner of which, made of single-crystal tungsten alloy, was a cathode and contained a core of nuclear fuel with through longitudinal microchannels, and the outer one, an anode cooled by a liquid metal coolant. In the mode of a nuclear rocket engine (NRE), hydrogen was fed into the cathode tube from one side, which was heated through microchannels in the fuel core and was ejected from the opposite side of the tube into the jet nozzle.

However, this device, taken as a prototype, cannot be used as part of the TETZ of the wing edge of the VLA for the following reasons:

- its cathode is located inside the anode and is heated by nuclear fuel from the inside, and not as a result of a flow around a hypersonic air stream from the outside;

- in the NRE mode, the gas-cooled electrode is the cathode, and not the anode, for cooling of which, both in this mode and in the NP mode, a liquid metal coolant is required, which is absent on the VLA;

- a cathode tube of refractory metal in a hypersonic air stream will undergo significantly more intense destruction by high-temperature gas corrosion than in a hydrogen stream;

- the dimensions of the EGC / fuel element in the radial direction (radius ~ 13 mm), determined in accordance with the neutron-physical characteristics of the nuclear reactor, do not correspond to the conditions for the placement of TEC in the edge of the wing of the VLA.

The objective of the invention is to develop the design of the TEC embedded in the edge with a small radius of curvature of the wing of the VLA, as a TETZ of this edge.

The problem is solved due to the fact that in the thermionic converter with a cylindrical coaxial cathode and anode containing ceramic-metal nodes for mutual isolation of the cathode and anode and bellows nodes compensating for the difference in thermal expansions of these electrodes, the cathode is made in the form of a pipe made of refractory metal, streamlined in the transverse direction hypersonic air flow, provided with a heat-resistant coating over the entire outer surface and a layer of thermal insulation on a portion of this surface that is not streamlined over at the same time, and the anode is located inside the cathode and is made in the form of a metal conductive rod equipped with inlet and outlet gas manifolds in the form of internal cavities from opposite ends of this rod, connected by longitudinal microchannels for cooling gas supplied to the inlet gas manifold and discharged outward from the outlet gas manifold . In this case, the bellows assembly, together with one of the two ceramic-metal assemblies located on the inlet side of the gas manifold, is located inside the high-speed aircraft, and the second ceramic-metal assembly is located inside the cowl made of heat-resistant material containing an inner layer of thermal insulation.

In particular cases of the invention:

- tungsten is selected as the cathode material, while the cathode is provided with an external heat-resistant coating of tungsten disilicide;

- molybdenum or niobium is selected as the cathode material, while the cathode is provided with an external heat-resistant coating, respectively, of their disilicides and an inner coating of tungsten;

- stainless steel with an external coating of nickel or tungsten, or niobium is selected as the anode material.

In this case, the inner coating of tungsten for the cathodes of molybdenum or niobium and the outer coating of nickel, tungsten or niobium for the anode of stainless steel serves to improve their emission characteristics (which increases the efficiency of thermionic energy conversion), and the use of the anode as a corrosion-resistant stainless steel makes it possible to use atmospheric air pre-cooled on board the VLA as a cooling gas anode.

The invention is illustrated by the drawing shown in FIG. one.

This drawing schematically shows the design of the TEC with cylindrical coaxial electrodes and with the external location of the cathode, which performs the function of the leading edge of the wing 1 VLA. In this case, the cathode 2 in the form of a pipe made of refractory metal with an external heat-resistant coating 3 is heated by braking the hypersonic air flow incident on the edge to a temperature> 1300 ° C. The direction of this flow is conditionally shown by an arrow. On the back side of the heat-resistant coating with respect to the air flow, there is a layer of thermal insulation 4 of the cathode from the wing structure. Anode 5 of the TEC in the form of a metal rod is located inside the cathode and is equipped with an inlet 6 and outlet 7 collectors for cooling gas, which are cavities inside the rod located at its ends and formed by end grooves in the rod connected to the nozzles 8 and 9 for supplying and discharging gas cooling the anode to a temperature of 600 ÷ 700 ° C. The cavity of the collectors are connected by longitudinal through microchannels 10 in the rod for the passage of this gas. Electrical and thermal decoupling of the electrodes, sealing of the interelectrode gap cavity (MEZ) 11 provided in the radial and axial directions by the spacers 12 and 13, respectively, as well as compensation of the difference in thermal expansions is carried out by ceramic-metal pressure junctions 14 and bellows assembly 15. In this case, the bellows assembly and the ceramic-ceramic containment, located on the side of the inlet gas manifold of the anode are placed inside the VLA, the wall 16 of which is conventionally shown in the drawing, and the second hermetic unit, located one hundred the outlet gas manifold is protected from air flow by a cowl 17 made of heat-resistant material, having an internal heat-insulating insert 18 and a nozzle 19 for exiting the cooling gas anode. In this case, the TEC cathode is under the electric potential of the VLA 20 casing, and the anode is equipped with a negative current output 21.

The solution to this problem is provided by the selected location and design of the components of the TEC under consideration. In particular, the location of the ceramic-metal assemblies and the bellows assembly, which determine the radial dimensions of the TEC with coaxial cylindrical electrodes, inside the VLA body and the fairing at the end of its wing, as well as the presence of microchannels in the anode for the gas passage allows the necessary cooling intensity to be maintained along its entire length; transducer into the wing edge of a relatively small radius.

Information confirming the possibility of carrying out the invention.

The TEC cathode is made in the form of a tube of monocrystalline tungsten, siliconized on the outside to form a protective heat-resistant coating and has an additional zirconium oxide thermal insulation coating with respect to the direction of flight of the VLA, which has a relatively low thermal conductivity. The anode is made in the form of a stainless steel rod with a nickel coating of its cylindrical surface. Grooves are made at the ends of the rod, which together with two nozzles welded into them form the cavities of the inlet and outlet gas collectors, connected by a plurality of through axial holes with a diameter of 0.5 ÷ 1.0 mm in the rod, through which the cooling anode gas is pumped (stored on board the VLA, or taken from the atmosphere with subsequent cooling in heat exchangers). Cermet hermetic joints and a bellows assembly are installed coaxially with the aforementioned nozzles. At the same time, the ceramic-metal hermetic unit installed on the outlet pipe side is protected from the influence of air flow by a spherical fairing with a diameter of ~ 30 mm from carbon graphite material with a cylindrical zirconium oxide insert, and the bellows assembly along with the second of the two hermetic units are located inside the VLA casing. The use of such a design made it possible to reduce the radius of the outer surface of the TEZ to ~ 7 mm, i.e. about twice. Thus, the specified combination of new features allows to solve the problem of the invention.

Claims (4)

1. Thermal emission transducer with a cylindrical coaxial cathode and anode, containing cermet units for mutual isolation of the cathode and anode and bellows units that compensate for the difference in thermal expansions of these electrodes, characterized in that the cathode is made in the form of a pipe made of refractory metal flowing in the transverse direction by hypersonic air a stream provided with a heat-resistant coating over the entire outer surface and a layer of thermal insulation on a portion of this surface that is not streamlined, and the anode is located ith inside the cathode, made in the form of a metal rod equipped with inlet and outlet gas manifolds in the form of internal cavities from opposite ends of this rod, connected by longitudinal microchannels for cooling gas supplied to the inlet gas manifold and discharged outward from the outlet gas manifold, the bellows assembly together with one of the two cermet units located on the inlet side of the gas manifold, it is located inside a high-speed aircraft, and the second metal the local ceramic unit is placed inside a fairing made of heat-resistant material containing an inner layer of thermal insulation. 2. The thermionic converter according to claim 1, characterized in that tungsten is selected as the cathode material, while the cathode is provided with an external heat-resistant coating of tungsten disilicide. 3. The thermionic converter according to claim 1, characterized in that molybdenum or niobium is selected as the cathode material, while the cathode is provided with an external heat-resistant coating of their disilicides and an inner coating of tungsten, respectively. 4. The thermionic converter according to claim 1, characterized in that stainless steel with an outer coating of nickel or tungsten or niobium is selected as the anode material.

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