An arc heated optical transmission test nozzle and method of operation

Abstract

This invention provides an arc-heated optical transmission test nozzle and its operation method, which is used for the ground simulation test of arc heating for imaging of simulated targets by the optical guidance system of high-speed air-to-air missiles, surface-to-air missiles and other aircraft. The method addresses technical issues such as the design principle of key nozzle dimensions based on the optical test aperture requirements, the solution to the cold airflow escape problem before and after the test, and the nozzle cooling method.

Description

Technical Field

[0001] This invention relates to an arc-heated optical transmission test nozzle and its operation method, belonging to the field of simulation test device design. Background Technology

[0002] Aircraft employing infrared terminal guidance technology jettison their fairings at a certain altitude during the terminal phase of their trajectory and continue flying in the dense atmosphere. The optical window located on the nose, often made of infrared-transmitting glass materials such as zinc sulfide, magnesium fluoride, spinel, and sapphire, is the part most severely affected by aerodynamic heating loads. The high window temperature and temperature gradient can interfere with the transmission of the optical imaging detection system, causing distortions such as target image shift, jitter, and blurring, severely impacting target recognition. This phenomenon is known as aero-optical effect. Currently, more and more aircraft are employing infrared terminal guidance technology. During their development, ground simulation tests of aero-optical effects are required to verify the thermodynamic properties of the window to withstand thermal shock and the various optical transmission performance indicators of the seeker system. This allows for a near-realistic target recognition effect under actual flight conditions, providing technical support for the thermal protection design of the window assembly and the optical design and algorithm improvement of the seeker system.

[0003] Arc-heated ground testing equipment has become the preferred equipment for aerodynamic heating simulation tests due to its advantages such as realistic gas composition, wide parameter adjustment range, and long-term heating capability. However, it is generally used for screening conventional heat-insulating materials and studying ablation performance, and no nozzle design technology suitable for aerodynamic optics research has been developed. To meet the needs of comprehensive system evaluation tests, it is necessary to develop specialized nozzle design technology based on arc-heated ground simulation testing equipment, focusing on the unique requirements of simultaneous heat, force, and light loading, to solve problems encountered in experiments such as reverse airflow optical observation and the fragility of crystalline materials due to rapid heating and cooling.

[0004] To conduct an optical imaging effect evaluation test, the detector located in the optical window needs to observe the simulated target against the nozzle airflow. The beam and the nozzle throat may be interfered with by the solid wall. It is necessary to establish the design principle of the inner surface of the test nozzle for optical transmission effect, so as to meet both the flow field simulation conditions and the special requirements of optical transmission.

[0005] Before / after the electric arc heater starts its formal operation, an equal amount of cold air will inevitably flow out of the heater. If this air blows directly onto the surface of the optical window, which is thermally brittle, it will cause a rapid heating / cooling effect on the window, leading to the risk of breakage. Effective measures need to be taken to protect the window.

[0006] During the test, the nozzle is at a high temperature, so it is necessary to achieve effective and uniform cooling of the nozzle. Summary of the Invention

[0007] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and propose an electric arc heated optical transmission test nozzle and its operation method to realize reverse airflow observation inside the nozzle.

[0008] The technical solution adopted in this invention is as follows:

[0009] This invention discloses an arc-heated optical transmission test nozzle, comprising: a nozzle body, a converging section water outlet pipe, a converging section cooling shell, an expanding section water outlet pipe, an expanding section cooling shell, a guide groove, a guide baffle, a feeding mechanism, an expanding section water inlet pipe, and a converging section water inlet pipe; wherein,

[0010] The outlet end of the nozzle body is connected to the U-shaped guide channel. The inner side of the U-shaped guide channel is symmetrically provided with limiting grooves, which match the guide baffle. The guide channel and the guide baffle form an overflow channel.

[0011] The feeding mechanism is connected to the guide baffle. The feeding mechanism controls the guide baffle to move along the limiting groove, which serves to block the nozzle body outlet.

[0012] The water outlet pipe and water inlet pipe of the contraction section are symmetrically arranged on the upper and lower sides of the cooling shell of the contraction section; the water outlet pipe and water inlet pipe of the expansion section are symmetrically arranged on the upper and lower sides of the cooling shell of the expansion section; cold water flows in from the water inlet pipe of the contraction section and the water inlet pipe of the expansion section respectively, and then flows out from the water outlet pipe of the contraction section and the water outlet pipe of the expansion section respectively, which serves to cool the nozzle body.

[0013] Furthermore, in the above-mentioned test nozzle, the nozzle body includes a contraction section and an expansion section; wherein, the inner surface of the contraction section is a concave spherical surface, and the inner surface of the expansion section includes an inner conical surface and a convex surface with an expansion angle θ of 5° to 6°, and the concave spherical surface and the inner conical surface are smoothly connected by the convex surface.

[0014] Furthermore, in the above-mentioned test nozzle, the cooling shell of the contraction section and the cooling shell of the expansion section are thin-walled roll structures, which are connected to the outer surface of the contraction section and the outer surface of the expansion section respectively to form a sandwich gap.

[0015] Furthermore, in the aforementioned test nozzle, the interlayer gap between the constriction section and the constriction section cooling shell of the nozzle body is the first cooling water flow gap, and the interlayer gap between the expansion section and the expansion section cooling shell is the second cooling water flow gap; cooling water flows into the first cooling water flow gap from the constriction section inlet pipe and flows out from the constriction section outlet pipe to cool the constriction section of the nozzle body; cooling water flows into the second cooling water flow gap from the expansion section inlet pipe and flows out from the expansion section outlet pipe to cool the expansion section of the nozzle body.

[0016] Furthermore, in the above-mentioned test nozzle, the width of the first cooling water flow gap and the second cooling water flow gap is 3-4 mm.

[0017] Furthermore, in the above-mentioned test nozzle, the diameter D1 of the throat at the narrowest section of the nozzle body is 1.2 to 1.5 times the local diameter D2 of the beam.

[0018] Furthermore, in the above-mentioned test nozzle, the exit Mach number of the nozzle body is 1.5 to 2.5.

[0019] Furthermore, in the above-mentioned test nozzle, the distance L between the guide baffle and the nozzle body is 1 / 3 to 1 / 2 of the nozzle body outlet diameter D3.

[0020] Furthermore, in the above-mentioned test nozzle, the guide vane's travel distance H is 1.2 to 1.6 times the nozzle body's outlet diameter D3.

[0021] Furthermore, in the above-mentioned test nozzle, the nozzle body, the water outlet pipe of the contraction section, the cooling shell of the contraction section, the water outlet pipe of the expansion section, the cooling shell of the expansion section, the water inlet pipe of the expansion section, and the water inlet pipe of the contraction section are all made of stainless steel, while the guide groove and the guide baffle are made of carbon steel.

[0022] A method for conducting experiments using an electric arc-heated optical transmission test nozzle, characterized by comprising:

[0023] Before the test begins, the feeding mechanism controls the baffle to block the test object, and the external cold airflow overflows through the space formed by the guide channel and the baffle.

[0024] The electric arc heater is activated to generate a flow field. After the flow field stabilizes, the feed mechanism pulls the guide baffle out of the flow field; the flow field pneumatically heats the test object.

[0025] The test subject observes the target through the throat of the nozzle body and obtains the observation results;

[0026] When the test time arrives, the feeding mechanism will send the guide baffle into the flow field to block the test object;

[0027] When the arc heater is stopped, the hot airflow becomes cold airflow and overflows from the space formed by the guide channel and the guide baffle.

[0028] The beneficial effects of this invention compared to the prior art are as follows:

[0029] (1) This invention closely combines the special requirements of thermo-mechanical-optical joint assessment of the aero-optical effect test of the terminal guidance optical window. Based on the electric arc heating ground test equipment, a special nozzle was developed, which solved the technical problems such as interference of reverse airflow observation in the nozzle and easy breakage of the window due to rapid cooling / heating. This allows the aero-heating test and optical effect research to be organically combined in the ground test, and has strong comprehensive utilization value.

[0030] (2) This invention provides experimental data for ground reproduction of flight failures and solves the problem of optimization and verification of improved optical detection systems for aircraft. Attached Figure Description

[0031] Figure 1 These are front and side views of the nozzle of the present invention; (a) is the front view, and (b) is the side view.

[0032] Figure 2 This is a schematic diagram of the delivery process of the flow guide baffle of the present invention;

[0033] Figure 3 This is a schematic diagram of the nozzle body throat and beam of the present invention. Detailed Implementation

[0034] like Figure 1 As shown, this embodiment provides an arc-heated optical transmission test nozzle; it consists of a nozzle body 1, a contraction section water outlet pipe 2, a contraction section cooling shell 3, an expansion section water outlet pipe 4, an expansion section cooling shell 5, a guide groove 6, a guide baffle 7, a feeding mechanism 8, an expansion section water inlet pipe 9, and a contraction section water inlet pipe 10, and their connection sequence is as follows. Figure 1 As shown.

[0035] In this embodiment, the inner surface of the nozzle body 1 has a concave-convex-conical structure. The contraction section is a concave spherical surface, and the expansion section is a conical surface. The contraction and expansion sections transition naturally from a convex surface. After the transition, a throat is formed at the narrowest cross-section. The diameter D1 of the throat at the narrowest cross-section of the nozzle body 1 is 1.2 to 1.5 times the local diameter D2 of the beam. Figure 3 As shown. In this embodiment, it is 1.2 times; the center of the concave spherical surface inside the nozzle body 1 coincides with the center of the end face, and the inlet size should be determined according to the outlet size of the mixing chamber of the upstream electric arc heater. The expansion section of the nozzle body 1 is a conical surface, and the expansion angle is preferably 5° to 6°. The outlet size of the expansion section is determined according to the equivalent size of the optical window of the test object. If the upstream test capability is sufficient, the outlet size of the nozzle body 1 can be appropriately enlarged to obtain a larger uniform area. The Mach number is determined by the ratio of the throat to the outlet size of the expansion section, and the recommended Mach number range is 1.5 to 2.5.

[0036] In this embodiment, the outer wall profile of the nozzle body 1 corresponds to the conical section and the straight section of the contraction section, respectively. The two are smoothly transitioned by a circular arc. The conical contraction section cooling shell 3 and the expansion section cooling shell 5 are respectively welded to the thin-walled roll for cooling. The contraction section water inlet pipe 10, the contraction section water outlet pipe 2, the expansion section water inlet pipe 9, and the expansion section water outlet pipe 4 are symmetrically welded upstream of the contraction section cooling shell 3 and the expansion section cooling shell 5 to ensure that the cooling water enters from the bottom and exits from the top, which is conducive to heat exchange.

[0037] The guide vane's travel stroke H is 1.2 to 1.6 times the nozzle body's outlet diameter D3, such as... Figure 2 As shown.

[0038] In this embodiment, a U-shaped guide groove 6 is welded to the outlet of the expansion section of the nozzle body 1. A guide baffle 7 is designed inside the groove. The guide baffle 7 is controlled by the feeding mechanism 8. The stroke should be greater than the outlet diameter of the nozzle body 1, and 1.5 times is recommended. This ensures that after feeding, it can completely block the outlet of the nozzle body 1 and after exiting, it is far enough away so as not to affect the flow field quality.

[0039] To achieve optimal cooling, this embodiment employs segmented cooling for the nozzle body 1. The contraction section is constructed from a large-tapered stainless steel plate, welded to form the contraction section cooling shell 3. The expansion section is constructed from a small-tapered stainless steel plate, welded to form the expansion section cooling shell 5. The taper is determined based on the external dimensions of the nozzle body 1, ideally creating a 3mm cooling water flow gap. The contraction section inlet pipe 10, contraction section outlet pipe 2, and expansion section inlet pipe 9, expansion section outlet pipe 4 are all welded to the upstream position, ensuring that the cooling water enters at the lowest point and exits at the highest point, thereby facilitating more thorough heat exchange and improving the cooling effect.

[0040] The steps for using the nozzle of this invention in a simulation experiment of ground heating by an electric arc during optical window detection imaging are as follows:

[0041] (a) Before the test begins, the feeding mechanism 8 controls the baffle 7 to be in the feeding state and block the front of the test object. The cold air during the air conditioning process overflows through the space formed by the guide groove 6 and the baffle 7.

[0042] (b) After the external equipment arc heater is started and the flow field is stable, the feed mechanism 8 quickly pulls the guide baffle 7 out of the flow field to fully expose the test object so that it can undergo aerodynamic heating test. At this time, the optical transmission test begins and the beam passes through the throat of the nozzle body 1 to image the observation target.

[0043] (c) When the test time is reached, the feeding mechanism 8 quickly sends the guide baffle 7 into the flow field to block the test object. Then the arc heater stops. At the moment of stopping, the hot airflow suddenly turns into cold airflow and overflows again from the space formed by the guide groove 6 and the guide baffle 7, thereby avoiding sudden cooling and breakage of the test object which is at high temperature.

[0044] Using this nozzle design technology, multiple sets of nozzles were successfully developed for optical windows of different structures and sizes. Optical transmission effect simulation tests were conducted on multiple optical terminal guidance aircraft, especially those using infrared terminal guidance, and good results were achieved. Figure 2 These are two infrared images of a simulated target obtained during the experiment.

[0045] The undisclosed technologies in this invention are common knowledge to those skilled in the art.

Claims

1. An arcjet optical transmission test nozzle characterized by, include: The nozzle body (1), the converging section water outlet pipe (2), the converging section cooling shell (3), the expanding section water outlet pipe (4), the expanding section cooling shell (5), the guide channel (6), the guide baffle (7), the feeding mechanism (8), the expanding section water inlet pipe (9), and the converging section water inlet pipe (10); among which, The outlet end of the nozzle body (1) is connected to the U-shaped guide groove (6). The inner side of the U-shaped guide groove (6) is symmetrically provided with limiting grooves, which match the guide baffle (7). The guide groove (6) and the guide baffle (7) form an overflow channel. The feeding mechanism (8) is connected to the guide baffle (7). The feeding mechanism (8) controls the guide baffle (7) to move along the limiting groove, which serves to block the outlet of the nozzle body (1). The contraction section outlet pipe (2) and the contraction section inlet pipe (10) are symmetrically arranged on the upper and lower sides of the contraction section cooling shell (3); the expansion section outlet pipe (4) and the expansion section inlet pipe (9) are symmetrically arranged on the upper and lower sides of the expansion section cooling shell (5); cold water flows in from the contraction section inlet pipe (10) and the expansion section inlet pipe (9) respectively, and then flows out from the contraction section outlet pipe (2) and the expansion section outlet pipe (4) respectively, which serves to cool the nozzle body (1); The nozzle body (1) includes a contraction section and an expansion section; wherein, the inner surface of the contraction section is a concave spherical surface (1-1), and the inner surface of the expansion section includes an inner conical surface (1-3) with an expansion angle θ of 5°~6° and a convex surface (1-2), and the concave spherical surface (1-1) and the inner conical surface (1-3) are smoothly connected through the convex surface (1-2); The diameter D1 of the throat at the narrowest section of the nozzle body (1) is 1.2 to 1.5 times the local diameter D2 of the beam.

2. An arcjet optical transmission test nozzle according to claim 1, wherein: The shrink section cooling shell (3) and the expansion section cooling shell (5) are thin-walled roll structures, which are connected to the outer surface of the shrink section and the outer surface of the expansion section respectively to form a sandwich gap.

3. An arcjet optical transmission test nozzle as recited in claim 2, wherein: The gap between the contraction section and the cooling shell (3) of the contraction section of the nozzle body (1) is the first cooling water flow gap, and the gap between the expansion section and the cooling shell (5) of the expansion section is the second cooling water flow gap. Cooling water flows into the first cooling water flow gap from the inlet pipe (10) of the contraction section and flows out from the outlet pipe (2) of the contraction section to cool the contraction section of the nozzle body (1). Cooling water flows into the second cooling water flow gap from the inlet pipe (9) of the expansion section and flows out from the outlet pipe (4) of the expansion section to cool the expansion section of the nozzle body (1).

4. The arc-heated optical transmission test nozzle according to claim 3, characterized in that: The width of the first cooling water flow gap and the second cooling water flow gap is 3~4mm.

5. The arc-heated optical transmission test nozzle according to claim 1, characterized in that: The nozzle body (1) has an exit Mach number of 1.5 to 2.

5.

6. The arc-heated optical transmission test nozzle according to claim 1, characterized in that: The distance L between the guide baffle (7) and the nozzle body (1) is 1 / 3 to 1 / 2 of the nozzle body (1) outlet diameter D3.

7. The arc-heated optical transmission test nozzle according to claim 1, characterized in that: The flow path H of the guide baffle (7) is 1.2 to 1.6 times the outlet diameter D3 of the nozzle body (1).

8. The arc-heated optical transmission test nozzle according to claim 1, characterized in that: The nozzle body (1), the water outlet pipe of the contraction section (2), the cooling shell of the contraction section (3), the water outlet pipe of the expansion section (4), the cooling shell of the expansion section (5), the water inlet pipe of the expansion section (9) and the water inlet pipe of the contraction section (10) are all made of stainless steel, and the guide groove (6) and the guide baffle (7) are made of carbon steel.

9. A method for conducting experiments using an arc-heated optical transmission test nozzle as described in any one of claims 1 to 7, characterized in that, include: Before the test begins, the feeding mechanism (8) controls the baffle (7) to block the test object. The external cold airflow overflows through the space formed by the guide groove (6) and the baffle (7). The electric arc heater is started to generate a flow field. After the flow field stabilizes, the feed mechanism (8) pulls the guide baffle (7) out of the flow field; the flow field pneumatically heats the test object. The test subject observes the target through the throat of the nozzle body (1) and obtains the observation results; When the test time is reached, the feeding mechanism (8) sends the guide baffle (7) into the flow field to block the test object; After the electric arc heater is stopped, the hot airflow becomes cold airflow and overflows from the space formed by the guide groove (6) and the guide baffle (7).

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