A Helical High-Temperature Armored Heater for a Space High-Energy Propulsion System

Abstract

The present invention discloses a spiral high-temperature armored heater for a space high-energy propulsion system, belonging to the technical field of armored heating devices. The armored heater includes a working part, a transition part, and a lead-out part; the working part is closely attached to the outer wall surface of the catalytic bed of the propulsion system and is wound in a spiral shape along its circumferential direction. The working part includes an armored protective shell, a heating wire, a dense ceramic skeleton, and ceramic powder; the transition part extends from the working part and forms a 90° angle with the lead-out direction of the working part, and includes an armored protective shell, a dense ceramic skeleton, ceramic powder, and a transition wire; the lead-out part is composed of an outer sleeve, a multi-strand outer lead wire, and a high-temperature insulating adhesive. The present invention adopts a transition lead-out process, which makes the power concentrated and the heating efficiency higher; uses platinum-rhodium alloy as the heating wire and the armored shell, and the heater has a high working and tolerance temperature; utilizes α-Al2O3 ceramic as the support and protection skeleton, making the device have better insulation performance and longer working life.

Description

Technical Field

[0001] The present invention relates to the technical field of armored heating devices, and particularly to a spiral high-temperature armored heater for a space high-energy propulsion system. Background Art

[0002] After a spacecraft separates from a launch vehicle and enters orbit, to complete various flight missions (for example, spacecraft orbit transfer, orbital transfer and maintenance, attitude adjustment and maintenance of itself, spacecraft docking, rendezvous and separation, takeoff and reentry of a lander, etc.), its maneuverability will completely rely on the space propulsion system equipped on itself. The armored heater of the space propulsion system is one of the important active thermal control facilities in the space propulsion system, and plays a key role in maintaining the thermal startup of the catalytic bed and the injection chamber, reducing the propellant consumption, extending the catalyst life, preventing the propellant from freezing and blocking the nozzle, ensuring the sensitive ignition and safe operation of the propulsion system according to instructions, etc.

[0003] Liquid monopropellant thrusters are generally used as the main propulsion units in spacecraft. Hydrazine (N2H4) monopropellant is the main propellant used in existing attitude and orbit control propulsion systems. Due to the safety problems of hydrazine propellant such as high toxicity, high freezing point, flammability and explosiveness, special protection and prevention measures need to be taken during the installation of the propulsion system, which greatly increases the launch cost of the satellite and related costs such as use and maintenance. With the development of space propulsion technology, "high energy and green" has gradually become the main development direction of liquid propellants for spacecraft attitude and orbit control propulsion systems. At present, two green propellants that are widely studied include HAN (hydroxylammonium nitrate) and ADN (ammonium dinitramide) - based propellants, both of which have the characteristics of safety, non - toxicity, high energy and low freezing point. However, during the ignition process of high - energy green thrusters, the required preheating and ignition temperatures are relatively high. For example, for a high - energy ADN - based non - toxic thruster, the preheating temperature required for its catalyst generally needs to reach above 300°C. At the same time, the combustion temperature of the propellant is as high as above 1600°C, and the temperature transferred to the heater through the catalytic bed is also above 1500°C, which poses higher requirements for the temperature - bearing capacity of the armored heater.

[0004] At present, the sheathed heaters of the space propulsion system developed in China mainly serve the monopropellant hydrazine thrusters. Since such heating devices mainly use NiGr or NiGrAl as the heating element or the sheathed protective shell, the maximum operating temperature is only 1100°C, which cannot meet the operating requirements of high-energy propellants above 1500°C during use. At the same time, traditional sheathed heaters have large resistance and low power, and cannot meet the heating requirements at high temperatures. Some patents have also proposed methods for developing high-power high-temperature heaters, but there are still some problems. For example, the neutralizer heating device of a Hall thruster involved in Patent No. 201510153525.3 is a high-power heating device. The sheathed heating component described therein is only composed of a heating core wire, ceramic powder, and a sheathed shell. Due to the low strength and density of the ceramic powder, during the bending or operation of the heater, the heating core wire is prone to eccentricity, resulting in a situation where the heater is prone to short-circuit and wire burnout during operation. On the other hand, the heating device described in the above patent has no design for the transition lead-out, so that the power of the heater cannot be fully concentrated on the working section during operation, which reduces the heating efficiency of the device to a certain extent. The sheathed heater for a thermal conductivity type liquid level sensor for high-temperature lava involved in Patent 201420798031.1 also has the above disadvantages. Summary of the Invention

[0005] In order to overcome the above deficiencies existing in the prior art, the purpose of the present invention is to provide a spiral high-temperature sheathed heater for a space high-energy propulsion system, which has concentrated power, higher heating efficiency, and high operating and tolerance temperatures.

[0006] To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0007] A spiral high-temperature sheathed heater for a space high-energy propulsion system includes a working part, a transition part, and a lead-out part, wherein: the working part includes a sheathed protective housing I, a heating wire, a dense ceramic skeleton, and ceramic powder; the transition part includes a sheathed protective housing II, a dense ceramic skeleton, ceramic powder, and a transition wire; the lead-out part includes an outer sleeve, a multi-strand outer lead, and a high-temperature insulating glue.

[0008] The working part of the sheathed heater is closely attached to the wall surface of the propulsion system catalytic bed and wound around it in a spiral shape along the circumferential direction. The working part can be closely attached to the thrust catalytic bed to ensure the heating efficiency of the sheathed heater.

[0009] In the working part, the sheathed protective housing I is in a spiral tubular structure, the dense ceramic skeleton is a ceramic tube, the heating wire is inserted into the ceramic tube, the ceramic tube is placed inside the sheathed protective housing, and the ceramic powder is filled in the gap between the ceramic tube and the sheathed protective housing.

[0010] The transition part extends from the working part and forms a 90° angle with the leading direction of the working part. In the transition part: the dense ceramic skeleton is a ceramic tube, the transition wire is installed inside the ceramic tube, the ceramic tube is placed inside the armored protection housing II, and the void between the ceramic tube and the armored protection housing II is filled with the ceramic powder.

[0011] The lead-out part of the heating wire circuit (two lead-out ends) is connected to the transition wire, and the connection process is spot welding, and the welding point is located in the transition section of the device.

[0012] The armored protection housing I and the armored protection housing II are thin-walled tube structures made of platinum-rhodium alloy, with an outer diameter of 2 mm and a wall thickness of 0.15 mm; the dense ceramic skeleton is alumina ceramic, the main component is α-Al2O3, the alumina content is higher than 99%, and the density is higher than 90%; the heating wire is made of platinum-rhodium alloy, and the transition wire is made of metallic platinum; the wire diameter of the transition wire is about 1.5 times that of the heating wire diameter, so as to ensure that the heating power is concentrated on the outer wall surface of the catalytic bed.

[0013] The ceramic powder is uniformly mixed by SiO2 and Al2O3 fine powder in a weight ratio of 1:1.

[0014] In the lead-out part, multiple strands of external leads are separated by high-temperature resistant insulating glue, and an outer sleeve is coated outside the multiple strands of external leads and the high-temperature resistant insulating glue.

[0015] The multiple strands of external leads are connected to the transition wire in the transition part; the high-temperature resistant glue has sufficient strength and can withstand high temperatures above 250°C at the same time.

[0016] When the satellite is in a low-temperature environment (-250°C to -100°C), without coating, the armored heater can preheat the thruster catalytic bed to above 400°C under the rated voltage. In the thermal vacuum flight simulation test, the device has gone through multiple ignition processes, can withstand the ignition high temperature of 1500°C, and is still operating well at present.

[0017] The design mechanism of the present invention is as follows:

[0018] Compared with the existing high-temperature heaters, the spiral high-temperature armored heater developed by the present invention uses a ceramic skeleton to position and protect the heating wire. Since the main component inside the ceramic skeleton is α-Al2O3, and the alumina content and density are both higher than 90%, the ceramic skeleton is superior to the ceramic powder in terms of strength, toughness, heat resistance, and temperature shock resistance, etc., and can provide better protection and support for the heating wire at high temperatures, reducing the risk of device short circuit.

[0019] The present invention uses a mixture of fine SiO2 and Al2O3 powders to fill the internal gaps of the device. The former has better bonding properties, and the latter has a higher dielectric constant. After being mixed in a weight ratio of 1:1, they can improve the high-temperature and vibration performance of the device. In order to concentrate the power of the heater on the working part, the heater of the present invention uses a transition lead-out design, and uses pure metal with lower conductivity as the transition wire to increase the effective power of the heater and the heating power of the device.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) Adopting the transition lead-out process, the power is concentrated and the heating efficiency is higher;

[0022] (2) Using platinum-rhodium alloy as the heating wire and the sheathed housing, the working temperature of the heater is high;

[0023] (3) By means of the vacuum perfusion process, SiO2 and Al2O3 powders are filled into the device, and the high-temperature anti-seismic performance of the heater is better;

[0024] (4) Using α-Al2O3 ceramic as the support and protection framework, the insulation performance of the device is better, and the working life and reliability are higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic structural diagram of the spiral high-temperature sheathed heater of the space high-energy propulsion system of the present invention;

[0026] Figure 2 It is the preferred dimensions of each part of the spiral high-temperature sheathed heater of the present invention (the dimension unit in the figure is cm).

[0027] Figure 3 For Figure 2 The cross-sectional schematic diagram at position "Ⅰ" in

[0028] Figure 4 For Figure 2 The A-A cross-sectional schematic diagram in

[0029] Figure 5 It is the schematic assembly diagram of the spiral high-temperature sheathed heater of the present invention and the catalytic bed.

[0030] In the figure: 100 - working part; 101 - sheathed housing Ⅰ; 102 - ceramic framework; 103 - ceramic powder; 104 - heating wire; 200 - transition part; 201 - sheathed housing Ⅱ; 202 - solder joint; 300 - lead-out part; 301 - outer sleeve; 302 - multi-strand lead; 303 - high-temperature resistant insulating glue; 4 - catalytic bed. DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention will be further described below in conjunction with the accompanying drawings.

[0032] The present invention provides a helical high-temperature sheathed heater for a space high-energy propulsion system, which includes a working part, a transition part, and a lead-out part, as Figures 1-4 shown; the working part includes a sheathed housing I 101, a ceramic skeleton 102, ceramic powder 103, and a heating wire 104; the heating wire circuit exists independently and is located inside the sheathed housing I 101. The heating wire is externally sleeved in the ceramic skeleton 102, and the ceramic powder 103 is filled in the device gap. The heating wire circuit is insulated from the sheathed housing. The ceramic skeleton is two parallel single-hole alumina ceramic tubes, mainly composed of α-Al2O3, with an alumina content higher than 99% and a density higher than 90%. The ceramic skeleton is used to position the heating wire. The ceramic powder is mainly prepared by mixing SiO2 and Al2O3 fine powder in a weight ratio of 1:1. Among them, SiO2 can improve the bonding performance of the ceramic powder layer, and Al2O3 can improve the heat conduction efficiency and insulation performance of the heater. Both the sheathed housing I and the heating wire are made of platinum-rhodium 30 alloy, and the wire diameter of the heating wire is 0.15 mm.

[0033] The transition part includes a sheathed housing II 201, a ceramic skeleton, ceramic powder, and a transition wire. The materials or compositions of the sheathed housing II 201, the ceramic skeleton, and the ceramic powder are the same as those of the working part; the transition wire is made of pure platinum metal with a wire diameter of 0.25 mm. The wire diameter of the transition wire is thicker than that of the heating wire to ensure that the heating power is mainly concentrated on the working part. The lead-out part (two lead-out ends) of the heating wire circuit is connected to the transition wire, and the connection process is spot welding. The solder joints are located in the transition section of the device; each of the two heating wire lead-out ends is connected to a transition wire, and the two formed solder joints 202 are effectively protected by being sleeved with a ceramic skeleton. (The ceramic skeleton used in the transition section is a double-hole alumina ceramic tube, and each hole of the ceramic tube protects a solder joint)

[0034] The sheathed housing I and the sheathed housing II are thin-walled tubular structures with an outer diameter of 2 mm and a wall thickness less than 0.15 mm, thereby reducing the heat conduction to the rear end.

[0035] The working part of the sheathed heater of the present invention is circumferentially distributed in a spiral shape on the outer wall of the catalytic bed 4 of the propulsion system. The working part can be closely attached to the thruster catalytic bed to ensure the heating efficiency of the sheathed heater ( Figure 5 ). After being led out, the sheathed housing I is bent at a 90° angle to protect the structure of the rear transition part.

[0036] The lead-out part includes an outer sleeve 301, a multi-strand lead 302, and a high-temperature insulating glue 303. The multi-strand lead is welded to the transition wire through an argon-protected micro-arc welding process, and the multi-strand lead is connected to the space power supply. Figure 5It is led out by two multi-strand lead wires, and the two lead wires are respectively connected to the positive and negative poles of the power supply. The high-temperature resistant adhesive used needs to have sufficient strength and be able to withstand a high temperature of 250 °C, such as silicon nitride high-temperature resistant adhesive.

[0037] The spiral high-temperature armored heater of the present invention has been installed on a high-energy green thruster. At present, it has completed the thermal vacuum flight simulation test with the thruster. The device can preheat the catalytic bed to over 400 °C within a short time without coating, and at this time, the surface temperature of the device exceeds 600 °C. The armored heater has completed multiple preheating tasks in the test and also experienced multiple ignition processes. After the test, the electrical performance of the device is good. The experiment proves that the device can not only withstand the high-temperature ignition process of 1500 °C, but also has high heating efficiency and service life, and can ensure the normal operation of the green high-energy thruster. The above embodiments are only the preferred embodiments of the present invention and do not limit the protection scope of the present invention. Any changes made by adopting the design principle of the present invention and non-creative labor on this basis shall fall within the protection scope of the present invention.

Claims

1. A spiral high-temperature armored heater for a space high-energy propulsion system, characterized in that: The sheathed heater includes a working part, a transition part and a lead-out part, where: the working part includes a sheathed protection housing I, a heating wire, a dense ceramic skeleton and ceramic powder; the transition part includes a sheathed protection housing II, a dense ceramic skeleton, ceramic powder and a transition wire; the lead-out part includes an outer sleeve, a multi-strand outer lead and a high-temperature resistant insulating adhesive. The working part of the sheathed heater is closely attached to the wall surface of the propulsion system catalytic bed and wound in a spiral shape along its circumferential direction. The working part can be closely attached to the thruster catalytic bed to ensure the heating efficiency of the sheathed heater. In the working part, the sheathed protection housing I is in a spiral tubular structure, the dense ceramic skeleton is a ceramic tube, the heating wire is installed inside the ceramic tube, the ceramic tube is placed inside the sheathed protection housing, and the ceramic powder is filled in the gap between the ceramic tube and the sheathed protection housing. The sheathed protection housing I and the sheathed protection housing II are thin-walled tube structures made of platinum-rhodium alloy, with an outer diameter of 2 mm and a wall thickness of 0.15 mm; the dense ceramic skeleton is alumina ceramic, the main component is α-Al2O3, the alumina content is higher than 99%, and the density is higher than 90%; the heating wire is made of platinum-rhodium alloy, and the transition wire is made of metallic platinum; the wire diameter of the transition wire is 1.5 times that of the heating wire diameter, so as to ensure that the heating power is concentrated on the outer wall surface of the catalytic bed.

2. The helical high-temperature armored heater of the high-energy propulsion system for satellites according to claim 1, characterized in that: The transition part extends from the working part and forms a 90° angle with the lead-out direction of the working part; in the transition part: the dense ceramic skeleton is a ceramic tube, the transition wire is installed inside the ceramic tube, the ceramic tube is placed inside the sheathed protection housing II, and the ceramic powder is filled in the gap between the ceramic tube and the sheathed protection housing II.

3. The spiral high-temperature armored heater of the space high-energy propulsion system according to claim 2, characterized in that: The lead-out part of the heating wire circuit is connected to the transition wire, and the connection process is spot welding, and the welding point is located in the transition section of the device.

4. The helical high-temperature armored heater of the space high-energy propulsion system according to claim 1, wherein: The ceramic powder is uniformly mixed by SiO2 and Al2O3 fine powder in a weight ratio of 1:

1.

5. The helical high-temperature armored heater of the space high-energy propulsion system according to claim 1, wherein: In the lead-out part, the multi-strand outer leads are separated by a high-temperature resistant insulating adhesive, and the outer sleeve covers the multi-strand outer leads and the high-temperature resistant insulating adhesive.

6. The helical high-temperature armored heater of the space high-energy propulsion system according to claim 5, characterized in that: The multi-strand outer leads are connected to the transition wire in the transition part by using argon arc micro-welding process with protection; the high-temperature resistant insulating adhesive has sufficient strength and can withstand a high temperature of 250 °C at the same time.

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