CN110132524A - A Large Aperture Schlieren System Applicable to Wind Tunnel Test Section - Google Patents

Abstract

The invention relates to a large-diameter schlieren system suitable for a wind tunnel test section, which solves the problems that the existing schlieren observation system adopts a large window glass, which leads to a decrease in system sensitivity and uniformity of background illumination and high cost. The system includes a light source system, a sealed front observation window, a collimating main reflector, a schlieren system, a schlieren main reflector, a sealed rear observation window and an imaging system; the schlieren system includes a sealed front schlieren lens barrel, test Cabin, sealed rear schlieren lens barrel; sealed front observation window is set on the side of the sealed front schlieren lens barrel, and sealed rear observation window is set on the side of the sealed rear schlieren lens barrel; light from the light source system is incident through the sealed front observation window to the collimated main reflector, the light passing through the collimated main reflector enters the test chamber through the sealed front schlieren mirror tube, passes through the airflow of the test chamber and enters the schlieren main reflector through the sealed back schlieren mirror tube, and the schlieren main reflector The mirror reflects the light and enters the imaging system through the sealed rear viewing window.

Description

A Large Aperture Schlieren System Applicable to Wind Tunnel Test Section

technical field

The invention relates to a schlieren observation system in the technical field of aerodynamic optics, in particular to a large-diameter schlieren system suitable for a wind tunnel test section.

Background technique

The schlieren observation system uses the principle that the refractive index gradient of light in the measured flow field is proportional to the airflow density of the flow field, and converts the change of the density gradient in the flow field into the change of the relative light intensity on the recording plane, so that the flow field density change area becomes Observable, distinguishable images, which are recorded. In the wind tunnel test, the Schlieren system is widely used to display the flow field structure of the wind tunnel model, and to test the variation characteristics of the flow field density in the test area. It has the characteristics of simple operation and high stability.

With the development of modern hypersonic vehicles, their size is getting larger and larger, and the requirements for the display range of the flow field of the Schlieren system are also increased to the level of Φ1m. The schlieren system with a Φ1m caliber belongs to the super-large schlieren system. In the traditional schlieren system, the light has to pass through two window glasses installed on the wall of the wind tunnel test section, the inhomogeneity of the refractive index gradient inside the window glass material and the processing defects on the surface shape will appear in the form of noise. In the schlieren image, the sensitivity of the schlieren system and the uniformity of the background illumination are reduced. The larger the window glass, the more difficult it is to ensure the uniformity of its refractive index gradient and the quality of surface processing. In addition, the window glass needs to withstand the load generated during the wind tunnel test, so that the larger the glass diameter, the thicker it is, and the longer the annealing time for the thicker glass material, the higher the safety risk. The production and processing risks of schlieren window glass materials with a diameter above Φ1m are very high, and there is no product that meets the demand in China. Imported high-performance and high-uniformity large-diameter window glass is very expensive. If it is used, it will bear 1/3 of the cost of the Schlieren system construction, which is a huge cost. Therefore, both the difficulty of production and processing of large-diameter schlieren window glass materials and the price cost limit the development of large-scale schlieren systems.

Contents of the invention

The purpose of the present invention is to solve the problem that the existing schlieren observation system adopts large window glass, which leads to the decrease of the sensitivity of the schlieren system and the uniformity of background illumination and high cost, and provides a large-diameter schlieren system suitable for the wind tunnel test section . The system can avoid the use of large-diameter window glass, reduce the defects of the sensitivity of the schlieren system and the uniformity of background illumination caused by the inhomogeneity of the large-diameter window glass material and processing defects, and greatly reduce the construction cost of the schlieren system. Improve its safety and reliability.

Technical scheme of the present invention is:

A large-diameter schlieren system suitable for a wind tunnel test section, including a light source system, a sealed front observation window, a collimating main reflector, a schlieren system, a schlieren main reflector, a sealed rear observation window, and an imaging system; The schlieren system includes a sealed front schlieren lens barrel, a test cabin, and a sealed rear schlieren lens barrel arranged in sequence; the sealed front observation window is arranged on the side of the sealed front schlieren lens barrel, and the sealed rear observation window is arranged on the sealed The side of the rear schlieren lens barrel; the light emitted by the light source system passes through the sealed front observation window and enters the collimating main reflector, and the light collimated by the collimating main reflector enters the test chamber through the sealed front schlieren lens barrel, passes After the air flow in the test chamber passes through the sealed rear schlieren lens barrel, it enters the schlieren main reflector, and the schlieren main reflector reflects the light, and then enters the imaging system after passing through the sealed rear observation window.

Further, the observation window before sealing is a small size observation window before sealing, and its diameter is less than 1/10 of the display range of the effective flow field.

Further, the sealed rear observation window is a small-sized sealed rear observation window, and its caliber is less than 1/10 of the effective flow field display range.

Further, the sealed front schlieren lens barrel is connected to the test cabin through a sealed bellows, and the test cabin is connected to the sealed rear schlieren lens barrel through a sealed bellows.

Further, the light source system includes an ultra-high-brightness LED lamp, a condenser lens group, a slit, and a first plane reflector arranged in sequence.

Further, the optical axis of the condensing lens group, the center of the slit, and the center of the first plane reflector are arranged coaxially.

Further, the slit is a "mouth"-shaped slit.

Further, the imaging system includes a second plane mirror, a knife edge, a focusing lens group, a schlieren camera arranged in sequence, and a knife edge controller to control the knife edge.

Further, the sealed front schlieren lens barrel and the sealed rear schlieren lens barrel are cylindrical structures.

Compared with the prior art, the present invention has the following technical effects:

1. The system of the present invention avoids the use of large-diameter window glass, and solves the problem of decreased sensitivity of the schlieren system and uniformity of background illumination caused by the inhomogeneity of the refractive index of the glass material.

2. The system of the present invention avoids the use of large-diameter window glass, which solves the safety risks of processing and installation of large-diameter window glass. The diameter of the small-diameter window glass used is less than 1/10 of the effective flow field display range, and the small diameter makes installation and processing Both are easier than large aperture window glass.

3. The present invention uses small-diameter window glass, which solves the problem of high cost of large-diameter window glass in large-scale schlieren systems, and saves about 1/3 of the construction cost compared with traditional schlieren systems.

Description of drawings

Fig. 1 is an optical path diagram of the large aperture schlieren system of the present invention.

Reference signs: 1-ultra-high brightness LED lamp, 2-condensing lens group, 3-slit, 4-first plane reflector, 5-sealed front observation window, 6-collimating main reflector, 7-seal Front schlieren tube, 8-test chamber, 9-sealed rear schlieren tube, 10-slieren primary reflector, 11-sealed rear observation window, 12-second plane reflector, 13-knife edge, 14-knife edge Controller, 15-focusing lens group, 16-schlieren camera, 17-sealing bellows.

Detailed ways

The content of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, the present invention provides a large-diameter schlieren system suitable for the wind tunnel test section, including a light source system, a sealed front observation window 5, a collimating main reflector 6, a sealed front schlieren lens barrel 7, a test Cabin 8, sealed rear schlieren lens barrel 9, schlieren main reflector 10, sealed rear observation window 11 and imaging system. The sealed front observation window 5, the collimating main reflector 6, and the sealed front schlieren lens barrel 7 constitute a schlieren system.

The light source system includes an ultra-high-brightness LED lamp 1, a condenser lens group 2, a slit 3, and a first plane reflector 4, and the slit is a "mouth"-shaped slit. The ultra-high brightness LED lamp 1 should have a large luminous flux value. The optical axis of the condenser lens group 2, the center of the "mouth"-shaped slit 3, and the center of the first plane reflector 4 are coaxially arranged. The "mouth" shaped slit 3 is composed of four narrow slits 3 in the shape of a "mouth" and a composite color filter spliced by four colored glasses of red, yellow, green and blue.

The imaging system includes a knife edge controller 14 , a knife edge 13 , a second plane mirror 12 , a focusing lens group 15 , and a schlieren camera 16 . The knife edge 13 is four narrow slits in the shape of "口", and the knife edge controller 14 can control the positions of the four narrow slits 3 of the "口" shape respectively, so that light can pass through the knife edge 13 entirely. The optical axes of the second plane mirror 12, the focusing lens group 15, and the schlieren camera 16 are consistent. The schlieren camera 16 is located at the focal point of the focusing lens group 15 . After the light passes through the sealed observation window 11, it is reflected by the second plane mirror 12 to the knife edge 13, and the knife edge controller 14 controls the positions of the four slits 3 in the shape of "mouth" in the knife edge 13, so that the light passes through the knife edge 13 and enters the focusing lens group 15. The focusing lens group 15 focuses the light onto the photosensitive surface of the schlieren camera 16, and the schlieren camera 16 forms an image of the outgoing light to obtain a schlieren image of the high-speed airflow in the test chamber 8.

The schlieren system includes a sealed front schlieren lens barrel 7 , a test chamber 8 , and a sealed rear schlieren lens barrel 9 . The sealed front schlieren lens barrel 7 and the sealed rear schlieren lens barrel 9 are fixed at both ends of the test cabin 8, and the test cabin 8 is placed in a high-speed wind tunnel. The collimating optical axis of the collimating primary reflector 6 is consistent with the main axis of the schlieren system, and the center of the schlieren primary reflector 10 is consistent with the center of the collimating primary reflector 6 . The sealed front schlieren lens barrel 7 is connected to the test cabin 8 through an airtight bellows, and the test cabin 8 is connected to the sealed rear schlieren lens barrel 9 through an airtight bellows. The sealed front schlieren lens barrel 7 and the sealed rear schlieren lens barrel 9 can be welded on both sides of the test chamber 8, and the sealed front schlieren lens barrel 7 and the sealed rear schlieren lens barrel 9 can be cylindrical, crimped and welded by stainless steel plates made. The light emitted by the collimating main reflector 6 is parallel light, and the parallel light emitted by the collimating main reflector 6 passes through the central axis of the sealed front schlieren lens barrel 7 , the test chamber 8 , and the sealed back schlieren lens barrel 9 .

The observation window before sealing is arranged on the side of the schlieren lens barrel before sealing, and the observation window after sealing is arranged on the side of the schlieren lens barrel after sealing. The pre-sealing observation window 5 is a small-sized pre-sealing observation window, whose aperture is smaller than 1/10 of the effective flow field display range, and does not block the effective passage aperture of light. The sealed observation window 11 is a small-sized sealed observation window, whose aperture is smaller than 1/10 of the effective flow field display range, and does not block the effective passing aperture of light.

The light emitted by the ultra-high-brightness LED lamp 1 is condensed by the condensing lens group 2, and after being condensed by the condensing lens group 2, the light passes through the "mouth"-shaped slit 3, and is captured by the red and yellow "mouth"-shaped slits. Four narrow slits in the shape of "mouth" in colored glass, green and blue, filter light. The filtered light is reflected by the first plane reflector 4 to the small-sized sealed front observation window 5, and the light passes through the small-sized sealed front observation window 5 and enters the collimating main reflector 6, and the collimating main reflector 6 collimates the light , and reflect the light to the sealed front schlieren lens barrel 7, the light passes through the sealed front schlieren lens barrel 7 to reach the test cabin 8, the test cabin 8 is placed in the high-speed wind tunnel, and the light passes through the high-speed wind tunnel in the test cabin 8 After sealing, the schlieren lens barrel 9 is incident on the schlieren main reflector 10, and the schlieren main reflector 10 reflects the light through the small-sized sealed observation window 11 to the second plane reflector 12, and the second plane reflector 12 reflects the light To the knife edge 13, the knife edge controller 14 controls the position of the four slits 3 of the "mouth" shape in the knife edge 13, so that the light passes through the knife edge 13 and reaches the focusing lens group 15, and the focusing lens group 15 focuses the light on the photosensitive surface of the schlieren camera 16 , the schlieren camera 16 images the outgoing light to obtain a schlieren image of the high-speed airflow in the test chamber 8 .

The invention provides a large-diameter color schlieren system suitable for wind tunnels. The effective flow field display range of the system is greater than Φ1m, and no large-diameter (greater than or equal to the flow field display range) window glass is used on both sides of the wind tunnel test section. The schlieren primary mirror equipment directly faces the disturbance and impact of high-speed airflow in the wind tunnel, and successfully solves the problem of high sensitivity and background illumination uniformity limited by the inhomogeneity of the window glass material, and greatly reduces the schlieren equipment with large aperture. The construction cost can be widely used in the construction of other large-diameter schlieren systems.

The invention adopts test equipment with a caliber above 1m, and connects the test equipment with the wind tunnel test section through a sealed schlieren lens barrel and a test cabin. Set small-sized sealed observation windows (less than 1/10 of the effective flow field display range) on both sides of the test cabin 8, and isolate the light source system and imaging system from the sealed environment of the wind tunnel. This setting is an external means to monitor the target. It is convenient for external observers to operate and adjust, and also ensures the safety of the operator. The system of the invention has high sensitivity, and can display the flow field whose refractive index changes to 5×10-5 caused by air flow disturbance. When the system has no disturbance in the test area, the illumination uniformity of the image plane is higher than 97%.

Claims (9)

1. A large-diameter schlieren system suitable for wind tunnel test sections, characterized in that: it includes a light source system, a sealed front observation window (5), a collimating main reflector (6), a schlieren system, and a schlieren main reflection Mirror (10), sealed rear observation window (11) and imaging system; The schlieren system comprises a sealed front schlieren lens barrel (7), a test chamber (8), and a sealed rear schlieren lens barrel (9) arranged in sequence; The observation window (5) before the sealing is arranged on the side of the schlieren lens barrel (7) before the sealing, and the observation window (11) after the sealing is arranged on the side of the schlieren lens barrel (9) after the sealing; The light emitted by the light source system passes through the sealed front observation window (5) and is incident on the collimating main reflector (6), and the light collimated by the collimated main reflector (6) passes through the sealed front schlieren lens barrel (7 ) enters the test chamber (8), passes through the airflow of the test chamber (8) and enters the schlieren main reflector (10) through the sealed schlieren lens barrel (9), and the schlieren main reflector (10) reflects the light and passes through the After sealing the rear observation window (11), it is incident to the imaging system. 2. The large-diameter schlieren system applicable to the wind tunnel test section according to claim 1, characterized in that: the observation window before sealing (5) is a small-sized observation window before sealing, and its diameter is smaller than that of the effective flow field display 1/10 of the range. 3. The large-diameter schlieren system applicable to the wind tunnel test section according to claim 2, characterized in that: the sealed observation window (11) is a small-sized sealed observation window, and its diameter is smaller than that of the effective flow field display 1/10 of the range. 4. The large-diameter schlieren system applicable to the wind tunnel test section according to claim 3, characterized in that: the sealed front schlieren lens barrel (7) and the test cabin (8) pass through the sealed bellows (17) Connection, the test chamber (8) and the sealed rear schlieren lens barrel (9) are connected through a sealed bellows (17). 5. The large-diameter schlieren system applicable to the wind tunnel test section according to any one of claims 1 to 4, characterized in that: the light source system includes super-high-brightness LED lamps (1) and condenser lenses arranged in sequence Group (2), slit (3), first plane mirror (4). 6. The large-aperture schlieren system applicable to the wind tunnel test section according to claim 5, characterized in that: the optical axis of the condenser lens group (2), the center of the slit (3), and the first plane The central coaxial setting of reflector (4). 7. The large-diameter schlieren system suitable for wind tunnel test section according to claim 6, characterized in that: the slit (3) is a "mouth"-shaped slit. 8. The large-diameter schlieren system applicable to the wind tunnel test section according to claim 7, characterized in that: the imaging system includes a second plane mirror (12), a knife edge (13), and a focusing lens arranged in sequence Group (15) and schlieren camera (16), and the blade controller (14) of controlling blade (13). 9. The large-diameter schlieren system applicable to the wind tunnel test section according to claim 8, characterized in that: the sealed front schlieren lens barrel (7) and the sealed rear schlieren lens barrel (9) are cylindrical structure.