Local gradient high temperature resistant structure of aviation ignition electric nozzle

Abstract

The invention belongs to the field of aviation and airspace engine ignition, and particularly relates to a local gradient high temperature resistant structure of an aviation ignition electric nozzle, which comprises an outer shell with a central cylindrical cavity and a through hole at the tail end, and a step surface is formed between the through hole and the central cylindrical cavity; the semiconductor block is cylindrical and is sleeved in the central cylindrical cavity, the end surface of the semiconductor block is in contact and limit with the step surface, and the center of the semiconductor block is provided with an inner through hole; the central electrode comprises a threaded section, a polished rod section and a large-diameter section at the tail end; wherein the polished rod section is sleeved in an inner through hole of the semiconductor block, a conical surface is formed between the large-diameter section and the polished rod section, and the inner through hole of the semiconductor block is provided with a conical surface matched with the central electrode; the end face of the nut abuts against the end face of the semiconductor block, so that the conical surface of the central electrode is tightly attached to the conical surface of the semiconductor block. And the insulator is sleeved in the central cylindrical cavity and pressed on the end face of the semiconductor block.

Description

Technical Field

[0001] This application belongs to the field of aviation and aerospace engine ignition, and specifically relates to an aviation ignition electric nozzle structure resistant to local gradient high temperature. Background Technology

[0002] With the development of aero-engines, the thrust-to-weight ratio of new engines has increased, leading to higher afterburner temperatures and greater axial temperature differences in the ignition nozzles. Temperature measurements of the actual operating environment of the aero-engine ignition nozzles were conducted using a temperature-indicating paint. The highest measured temperature was 1080℃, with a testing error of ±20℃, approaching the extreme high temperature limit of 1100℃. The temperature in the outer region was already below the indicative temperature of the paint, and the axial temperature gradient was significantly greater than 780℃.

[0003] Based on the application scenario of the afterburner ignition nozzle in an engine, the nozzle housing is installed between the retaining ring and the mounting thread inside the duct, subjected to an airflow pressure of 290.4 kPa, a temperature of 810°C, and a flow velocity of 170 m / s; the temperature at the nozzle discharge tip is 1020°C, the flow velocity is 10 m / s, and the duration is 8 minutes. Simulations were conducted as required, with an internal and external temperature difference of approximately 200°C. The results are shown below. Figure 2 .

[0004] Due to the increased axial temperature difference, the internal core rod expands, deforms, and protrudes during the use of existing electric nozzles due to the thermal expansion difference caused by the temperature difference between the inside and outside. Summary of the Invention

[0005] To address the aforementioned problems, this application provides an aerospace ignition nozzle structure resistant to localized high-temperature gradients, comprising:

[0006] The outer shell (1) has a central cylindrical cavity and a through hole at the end, wherein a stepped surface is formed between the through hole and the central cylindrical cavity;

[0007] Semiconductor block (3), which is cylindrical, is fitted inside the central cylindrical cavity, its end face is in contact with the stepped surface for limiting, and its center has an internal through hole;

[0008] The center electrode (4) includes a threaded section, a smooth section and a large-diameter section at the end; wherein the smooth section is fitted into the inner through hole of the semiconductor block (3), and a conical surface is formed between the large-diameter section and the smooth section, and the inner through hole of the semiconductor block (3) has a conical surface that mates with the center electrode (4);

[0009] A nut (2) is installed on the threaded section, and the end face of the nut (2) abuts against the end face of the semiconductor block (3), so that the conical surface of the center electrode (4) is in close contact with the conical surface of the semiconductor block (3);

[0010] An insulator (5) is fitted inside the central cylindrical cavity and pressed against the end face of the semiconductor block (3).

[0011] Preferably, there is a preset distance between the end face of the semiconductor block (3) and the end face of the outer shell (1), and the preset distance forms a gas retention area in the through hole, which facilitates ignition.

[0012] Preferably, the preload of the nut (2) forms a preload that makes the center electrode (4) radially contact the semiconductor block (3) through the conical surface, and the semiconductor block (3) applies the preload or radial thermal expansion force uniformly to the inner cylindrical surface of the semiconductor block (3) through the outer cylindrical surface.

[0013] Preferably, the thickness of the end wall of the outer shell (1) is at least 3 mm.

[0014] Preferably, the preset distance is 2mm.

[0015] Preferably, the step surface is a right-angled step surface.

[0016] This application improves the expansion structure of the ignition nozzle under high-temperature operating conditions. High-temperature verification shows a significant reduction in expansion deformation at high temperatures. This solves the problem of high-temperature expansion deformation of the ignition nozzle, improves product reliability, and yields good economic and social benefits. Attached Figure Description

[0017] Figure 1 This is a partial schematic diagram of the structure of an aviation ignition nozzle that can withstand localized high temperatures.

[0018] Figure 2 This is a simulation diagram of an existing ignition nozzle.

[0019] Figure 3 This is a simulation diagram of the ignition nozzle of this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings. Figure 1 As shown, this application provides a structure for an aviation ignition nozzle resistant to localized high temperatures, comprising:

[0021] The outer shell (1) has a central cylindrical cavity and a through hole at the end, and a stepped surface is formed between the through hole and the central cylindrical cavity; the stepped surface is a right-angled stepped surface.

[0022] Semiconductor block (3), which is cylindrical, is fitted inside the central cylindrical cavity, its end face is in contact with the stepped surface for limiting, and its center has an internal through hole;

[0023] The center electrode (4) includes a threaded section, a smooth section and a large-diameter section at the end; wherein the smooth section is fitted into the inner through hole of the semiconductor block (3), and a conical surface is formed between the large-diameter section and the smooth section, and the inner through hole of the semiconductor block (3) has a conical surface that mates with the center electrode (4);

[0024] A nut (2) is installed on the threaded section, and the end face of the nut (2) abuts against the end face of the semiconductor block (3), so that the conical surface of the center electrode (4) is in close contact with the conical surface of the semiconductor block (3);

[0025] An insulator (5) is fitted inside the central cylindrical cavity and pressed against the end face of the semiconductor block (3).

[0026] The central electrode assembly is welded from a core rod and a central electrode. After being installed into the semiconductor block, the assembly is secured with a special nut to ensure close contact between the central electrode and the end face of the semiconductor block. A tapered fit is used between the semiconductor block and the housing. An insulator is installed between the central electrode assembly and the housing for insulation. The gap is filled with sealant and then heat-sealed to achieve sealing, insulation, and fixation. The central electrode is in contact with the end face of the semiconductor block, and the semiconductor block is fixed to the tapered surface of the housing with sealant to ensure the appropriate discharge gap dimensions.

[0027] Working principle: When the discharge terminal of the electric nozzle is under an external voltage, current flows through the semiconductor surface, forming several discharge channels. Heat is generated in the area with high current density. Due to the negative temperature coefficient of the semiconductor material, the resistance decreases rapidly. When the current density increases to a certain level, electron avalanches are formed on the surface of the discharge terminal of the electric nozzle, ionizing the surface gas. The discharge gap between the center electrode and the side electrode of the electric nozzle is broken down to form an electric spark, which then ignites the fuel-air mixture in the engine combustion chamber.

[0028] Preferably, there is a preset distance between the end face of the semiconductor block (3) and the end face of the outer casing (1), and the preset distance forms a gas retention area within the through hole, which facilitates ignition. The "gas retention area" function is integrated into the basic structure. This design, by reserving space, may help to form a more ignitable mixture at the tip of the electric nozzle, improving ignition reliability. At the same time, this space itself also provides a buffer for thermal expansion, which is a clever multifunctional design.

[0029] Preferably, the preload of the nut (2) forms a preload that radially contacts the central electrode (4) and the semiconductor block (3) through the conical surface. The semiconductor block (3) then uniformly applies the preload or radial thermal expansion force to the inner cylindrical surface of the semiconductor block (3) through its outer cylindrical surface. The key function of the conical surface fit is to convert the axial preload of the nut into radial contact pressure between the central electrode and the semiconductor block. This not only ensures good electrical contact but, more importantly, allows the structure to undergo radial stress compensation when heated, which is the core mechanism for achieving "resistance to localized high-temperature gradients." Simultaneously, it prevents the outer casing from cracking.

[0030] Preferably, the thickness of the end wall of the outer shell (1) is at least 3 mm. The preset distance is 2 mm.

[0031] Thermal simulations were performed on the improved structure, applying compensated temperature and wind speed. The results showed that the highest end temperature was 1050℃, and the highest central electrode temperature was 920℃. A small temperature difference existed between the central electrode and the shell, with the highest temperature below 100℃. The length was approximately 20mm. Figures 2-3 .

[0032] The central electrode region is 920℃. When the central electrode temperature is 100℃ higher than the central electrode temperature, the elongation of the free end of the central electrode head is 15.6 × 10⁻⁶. -6 × (920-20)×20=0.28mm, the elongation at the free end of the shell head is 14.9×10 -6 × (800-20)×20=0.24 (mm), the elongation of the shell is 0.28-0.24=0.04 (mm) less than the elongation of the center electrode.

[0033] When under cooling pressure, with the center electrode temperature at 920℃ and the shell cooling limit temperature at 300℃, the elongation of the free end of the center electrode head is 20 × 15.6 × 10⁻⁶. -6 ×(920-20)+25×11.4×10 -6 × (800 - 20) + (156.9 - 25 - 20) × 14.9 × 10 -6 × (800-20) = 1.8 (mm) The elongation at the free end of the shell head is 12.85 × 10 -6 × (300-20)×156.9=0.56 (mm), the elongation of the shell is 1.8-0.56=1.24 (mm) less than the elongation of the center electrode.

[0034] Calculations show that the improved design can reduce the difference between the elongation of the housing and the elongation of the center electrode during engine use, thereby reducing internal stress.

[0035] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A structure for an aviation ignition nozzle resistant to localized high-temperature gradients, characterized in that, include: The outer shell (1) has a central cylindrical cavity and a through hole at the end, wherein a stepped surface is formed between the through hole and the central cylindrical cavity; Semiconductor block (3), which is cylindrical, is fitted inside the central cylindrical cavity, its end face is in contact with the stepped surface for limiting, and its center has an internal through hole; The center electrode (4) includes a threaded section, a smooth section and a large-diameter section at the end; wherein the smooth section is fitted into the inner through hole of the semiconductor block (3), and a conical surface is formed between the large-diameter section and the smooth section, and the inner through hole of the semiconductor block (3) has a conical surface that mates with the center electrode (4); A nut (2) is installed on the threaded section, and the end face of the nut (2) abuts against the end face of the semiconductor block (3), so that the conical surface of the center electrode (4) is in close contact with the conical surface of the semiconductor block (3); An insulator (5) is fitted inside the central cylindrical cavity and pressed against the end face of the semiconductor block (3).

2. The aerospace ignition nozzle structure resistant to localized high-temperature gradients as described in claim 1, characterized in that, There is a preset distance between the end face of the semiconductor block (3) and the end face of the outer shell (1). The preset distance forms a gas retention area in the through hole, which facilitates ignition.

3. The aerospace ignition nozzle structure resistant to localized high-temperature gradients as described in claim 1, characterized in that, The preload of the nut (2) forms a preload that makes the center electrode (4) and the semiconductor block (3) radially contact each other through the conical surface. The semiconductor block (3) applies the preload or radial thermal expansion force evenly to the inner cylindrical surface of the semiconductor block (3) through the outer cylindrical surface.

4. The aerospace ignition nozzle structure resistant to localized high-temperature gradients as described in claim 1, characterized in that, The thickness of the end wall of the outer shell (1) is at least 3 mm.

5. The aerospace ignition nozzle structure resistant to localized high-temperature gradients as described in claim 4, characterized in that, The preset distance is 2mm.

6. The aerospace ignition nozzle structure resistant to localized high-temperature gradients as described in claim 1, characterized in that, The step surface is a right-angled step surface.

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