A wind tunnel test section device for acoustic resonance testing of heat transfer tubes

Abstract

The present invention discloses a wind tunnel test section device for acoustic resonance testing of heat transfer tubes. The test section device is a rectangular chamber, including a top plate, a bottom plate, a front side plate, a rear side plate, a detachable test block, and an angle display dial. The detachable test block is respectively mounted on the front side plate and the rear side plate, and the angle dial is respectively located on the front side plate and the rear side plate. The center positions of the top plate and the bottom plate are provided with mounting holes for acoustic detection devices. The size range of the rectangular chamber cross section is (300-500) mm*(300-500) mm. The present invention adopts a wind tunnel test section device for acoustic resonance testing of heat transfer tubes, which is provided with a detachable test piece, and the flow velocity attack angle can be adjusted. The thicker wall thickness overcomes the phenomenon of sound leakage, and ensures the requirements for sound energy when acoustic resonance occurs. The cavity of the test section of a certain size effectively achieves the phenomenon of "locking frequency" with the inherent sound frequency of the cavity and the frequency of vortex shedding generated by the fluid bypassing the heat transfer tube.

Description

Technical Field

[0001] The invention relates to the technical field of wind tunnel testing, and in particular to a wind tunnel testing section device for acoustic resonance testing of a heat transfer tube. Background Art

[0002] A wind tunnel is a device used to simulate atmospheric flow. It usually consists of a wind duct and corresponding fans. It is usually used to test the performance of objects such as aerospace equipment, cars, and buildings at different wind speeds. It can accurately control the speed, temperature, humidity, and pressure of the airflow, allowing relevant researchers to study the aerodynamic performance of objects in a controlled environment.

[0003] The concept of heat transfer tube acoustic resonance is that after the gas enters the cavity, an acoustic standing wave will be formed in a direction perpendicular to the flow direction and the axis of the heat transfer tube. When the frequency of the acoustic standing wave is close to or consistent with the Karman vortex frequency, acoustic resonance will occur.

[0004] The four walls of the test section of the traditional wind tunnel are relatively thin, which will lead to sound leakage during the acoustic resonance experiment, resulting in loss of sound energy, so that the requirements of the acoustic resonance of the heat transfer tube cannot be met, and the corresponding sound pressure and sound pressure level are greatly reduced; on the other hand, the cavity size of the test section of the traditional wind tunnel is relatively large, which will cause the inherent sound frequency of the cavity to be much greater than the frequency of vortex shedding generated by the gas bypassing the heat transfer tube, so that the two frequencies cannot be locked. In summary, the traditional wind tunnel test section cannot meet the experimental requirements of the acoustic resonance of the heat transfer tube in the cavity. In addition, the traditional wind tunnel test section device is an integral structure, which cannot flexibly disassemble the test piece, cannot arbitrarily switch the flow angle, and cannot meet the requirements of frequent disassembly and installation of the test piece, replacement, and change of different experimental angles. Summary of the invention

[0005] The purpose of the present invention is to provide a wind tunnel test section device for acoustic resonance testing of heat transfer tubes, which is provided with a detachable test piece and an adjustable flow velocity angle of attack. The thicker wall thickness overcomes the phenomenon of sound leakage and ensures the requirement for sound energy when acoustic resonance occurs. The cavity of the test section with a certain size effectively achieves a "frequency locking" phenomenon with the inherent sound frequency of the cavity and the frequency of vortex shedding generated by the fluid bypassing the heat transfer tube.

[0006] To achieve the above-mentioned purpose, the present invention provides a wind tunnel test section device for acoustic resonance testing of heat transfer tubes, wherein the test section device is a rectangular chamber, comprising a top plate, a bottom plate, a front side plate, a rear side plate, a detachable test block, and an angle display dial. The top plate, the bottom plate, the front side plate, and the rear side plate are assembled in an inlay manner, the detachable test blocks are respectively mounted on the front side plate and the rear side plate, the angle dials are respectively located on the front side plate and the rear side plate, mounting holes for acoustic detection devices are provided at the center positions of the top plate and the bottom plate, the size range of the rectangular chamber cross section is (300-500) mm*(300-500) mm, and a connecting flange is provided at one end of the rectangular chamber.

[0007] Preferably, the top plate and the bottom plate are made of acrylic material, and the thickness thereof is not less than 15 mm.

[0008] Preferably, the detachable experimental block is a circular block structure with a radius of 6-9D, and the detachable experimental block is provided with one or more through holes for installing and fixing the heat transfer pipe, and the diameter of the through hole is 0.6D.

[0009] Preferably, a mounting groove is provided on the upper surface of the detachable test block, a detachable indicator rod is provided in the mounting groove, and the indicator rod indicates the scale on the angle display dial.

[0010] Preferably, the front side plate and the rear side plate are provided with reserved holes for installing detachable experimental blocks.

[0011] Preferably, a 0-360° angle display dial is provided around the reserved holes of the front side plate and the rear side plate.

[0012] Preferably, a protrusion is provided on the outer wall of the detachable test block, a slide rail corresponding to the protrusion is provided on the inner wall of the reserved hole, the protrusion slides in the slide rail, the size of the slide rail is adapted to the protrusion, and a notch is provided on the slide rail for installation and removal of the protrusion, the size of the notch is adapted to the protrusion.

[0013] Preferably, the mounting hole of the acoustic detection device is a through hole with a diameter of 0.2D.

[0014] The advantages and positive effects of the wind tunnel test section device for acoustic resonance testing of heat transfer tubes described in the present invention are:

[0015] 1. The test section device of the present invention can be used for special acoustic resonance experiments of single heat transfer tube, multiple heat transfer tubes and special-shaped heat transfer tubes arranged at an angle of 0-90°.

[0016] 2. The present invention utilizes a detachable experimental block to achieve the frequent replacement and installation requirements of the experimental pieces, saving the processing and production costs of the side walls at different numbers, saving the corresponding manpower and material resources, and avoiding the waste of other required resources. The angle dials set on the walls on both sides of the rectangular cavity are utilized to achieve the requirements of different flow rate angle changes. The indicator rod on the detachable experimental block is used to cooperate with the dials with the same angle display to achieve the adjustment of different flow rate angles.

[0017] 3. The wind tunnel test section cavity within a certain wall thickness range designed by the present invention has a small sound leakage, thereby ensuring the sound tightness of the test section. Due to the use of acrylic materials of a certain thickness calculated through design, the test section with a thickness of 15 mm or more can effectively produce a sound insulation of more than 34 dB, effectively limiting the leakage of sound energy and meeting the experimental requirements for acoustic resonance. Using the designed dimensions as the specific structural dimensions of the device can meet the requirement that the inherent sound frequency of the cavity is in the range of 300 to 600 Hz.

[0018] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of a wind tunnel test section device for acoustic resonance testing of a heat transfer tube according to the present invention;

[0020] Figure 2 A schematic diagram of a detachable test block in a wind tunnel test section device for acoustic resonance testing of a heat transfer tube according to the present invention;

[0021] Figure 3 An exploded view of the reserved holes and detachable test blocks in the wind tunnel test section device for the heat transfer tube acoustic resonance test of the present invention;

[0022] Figure 4 for Figure 3 Enlarged view of point A in the middle;

[0023] Figure 5 The experimental effect diagram of the verification example of the present invention;

[0024] Figure 6 This is a cross-sectional diagram of a single heat transfer tube experiment in a verification example of the present invention.

[0025] Reference numerals

[0026] 1. Flange; 2. Through hole; 3. Removable test block; 4. Mounting hole; 5. Front side panel; 6. Bottom panel; 7. Rear side panel; 8. Top panel; 9. Angle display dial; 10. Bump; 11. Slide rail; 12. Notch; 13. Indicator rod; 14. Mounting slot; 15. Reserved hole. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0028] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0029] Example

[0030] like Figure 1 As shown, a wind tunnel test section device for acoustic resonance testing of a heat transfer tube is provided. The test section device is a rectangular chamber, the size range of the rectangular chamber cross section is (300-500) mm*(300-500) mm, and a connecting flange 1 is provided at one end of the rectangular chamber.

[0031] The rectangular chamber includes a top plate 8, a bottom plate 6, a front side plate 5, a rear side plate 7, a detachable experimental block 3, and an angle display dial 9. The top plate 8, the bottom plate 6, the front side plate 5, and the rear side plate 7 are assembled in an inlaid manner. The top plate 8 and the bottom plate 6 are made of acrylic material, and the thickness thereof is not less than 15 mm.

[0032] The detachable experimental block 3 is respectively installed on the front side plate 5 and the rear side plate 7. The detachable experimental block 3 is a circular block structure with a radius of 6-9D. The detachable experimental block 3 is provided with one or more through holes 2 for installing and fixing the heat transfer tube. The diameter of the through hole 2 is 0.6D. The angle dial is respectively located on the front side plate 5 and the rear side plate 7. The front side plate 5 and the rear side plate 7 are provided with reserved holes 15 for installing the detachable experimental block. Around the reserved holes 15 of the front side plate 5 and the rear side plate 7, a 0-360° angle display dial 9 is provided.

[0033] like Figure 2 As shown, a mounting groove 14 is provided on the upper surface of the detachable experimental block 3 , and a detachable indicating rod 13 is provided in the mounting groove 14 . The indicating rod 13 indicates the scale on the angle display dial 9 .

[0034] like Figure 3As shown, a convex block 10 is provided on the outer wall of the detachable test block 3, and two convex blocks 10 are provided and symmetrically arranged. A slide rail 11 corresponding to the convex block 10 is provided on the inner wall of the reserved hole 15. The convex block 10 slides in the slide rail 11. The size of the slide rail 11 is adapted to the convex block 10. The slide rail 11 is provided with a notch 12 (such as Figure 4 As shown, there are two notches 12 and they are symmetrically arranged, corresponding to the two protrusions 10 respectively, and the size of the notches 12 is adapted to the protrusions 10. The protrusion 10 of the detachable experimental block 3 is installed into the slide rail 11 through the notch 12, and the detachable experimental block 3 slides on the scientific research slide rail 11, driving the indicator rod 13 to rotate, and the indicator rod 13 indicates the angle on the angle display dial 9 to achieve the change of the incoming flow attack angle. When the detachable experimental block 3 needs to be removed, the detachable experimental block 3 is rotated to align the protrusion 10 with the notch 12, and the detachable experimental block 3 is pulled out through the notch 12.

[0035] A mounting hole 4 for the acoustic detection device is provided at the center of the top plate 8 and the bottom plate 6 . The mounting hole 4 for the acoustic detection device is a through hole 2 with a diameter of 0.2D.

[0036] The detachable test block 3 is mounted on the front side plate 5 and the rear side plate 7 in an inlaid manner, forming a complete wind tunnel test section device that can realize the acoustic resonance test of the heat transfer tube. The change of the flow velocity angle of attack is achieved by rotating the indicator rod 13 on the detachable test block 3 to align with the angle value of the angle dial on the front side plate 5 and the rear side plate 7. The microphone is installed at the position of the acoustic test equipment installation hole 4, and finally it is connected to other components of the wind tunnel through the connecting flange 1.

[0037] The acoustic modal frequency of the rectangular cavity of the test section device can be expressed by the following formula:

[0038]

[0039] Where: f a is the natural sound frequency, Hz;

[0040] n is the number of vibration modes, which refers to the integer multiple of half wave and has no dimension;

[0041] c is the speed of sound, m / s;

[0042] L is the characteristic length, m, which here refers to the height or width of the designed test section device.

[0043] The frequency of vortex shedding around the heat transfer tube can be expressed by the following formula:

[0044]

[0045] Where: f v is the frequency of vortex shedding, Hz;

[0046] St is the Strouhal number, dimensionless;

[0047] D is the diameter of the experimental heat transfer tube, m;

[0048] U is the incoming flow velocity, m / s.

[0049] When 0.8f v <f a <1.2f v , the vortex shedding frequency of the heat transfer tube and the acoustic mode frequency of the cavity will be locked, and the system will experience acoustic resonance.

[0050] Acrylic material of a certain thickness that has been designed and calculated is used, and the acrylic board is referred to as PMMA board. The weighted sound insulation of 12mm and 15mm thick PMMA boards is measured to be 32dB and 34dB, while 20mm can reach 37dB. The test section with a thickness of 15mm or more will produce a sound insulation greater than 34dB, effectively limiting the leakage of sound energy and meeting the experimental requirements for acoustic resonance. According to the above-given cavity inherent sound frequency calculation formula, according to the size of the rectangular cross-section (300-500)mm*(300-500)mm, it can be calculated that the cavity size in the invention can make the cavity sound frequency 310Hz or 425Hz, which just meets the requirement of 300-600Hz.

[0051] Verification Example

[0052] Take the heat transfer tube diameter D as 13mm and the test section cross-sectional size as 300*400mm as an example to conduct a verification experiment. Figure 6 As shown, Figure 6 W is the width of the test section, 300 mm; H is the height of the test section, 400 mm; the blue line represents the diameter of a single cylinder in the experiment, which is 13 mm.

[0053] Experimental Procedure

[0054] Starting from the incoming flow velocity of 0, the flow velocity value is continuously increased. The data logger can collect the vortex shedding frequency and the corresponding sound pressure at different flow velocities. It is found that before the flow velocity of about 25m / s, the collected vortex shedding frequency is constantly increasing with the increase of the incoming flow velocity. When the incoming flow velocity reaches 25m / s, the vortex shedding frequency is stabilized between 440-445Hz with the continuous increase of the incoming flow velocity, which is close to the theoretical natural acoustic modal frequency of the chamber of 425Hz, indicating that the expected effect of the experiment has occurred, that is, the heat transfer tube has undergone acoustic resonance in the test section. The results are as follows: Figure 5 And as shown in Table 1.

[0055] Table 1 Vortex shedding frequency at different flow velocities

[0056] Flow velocity (m / s) Frequency (Hz) 21.8 373 22.9 398 23.8 412 24.6 429 24.8 437 25 441 25.3 445 26.2 445 25.8 444 27.2 444 26.9 444 27.5 452 28 465 28.8 500 29.4 513

[0057] Figure 5 This is a diagram of the effect obtained by the experiment conducted in the device of the present invention. The black dots show the increase in the frequency of vortex shedding caused by the gas bypassing the heat transfer tube as the flow rate increases; the red line shows the effect of frequency locking within a certain flow rate range, that is, the vortex shedding frequency is consistent with the frequency of the chamber and locked, that is, the vortex shedding frequency does not increase with the increase of flow rate. If the device section of the present invention is not used, the phenomenon represented by the red line will not occur.

[0058] Therefore, the present invention adopts the above-mentioned wind tunnel test section device for acoustic resonance testing of heat transfer tubes, which is provided with a detachable test piece and adjustable flow velocity angle of attack. The thicker wall thickness overcomes the phenomenon of sound leakage and ensures the requirement for sound energy when acoustic resonance occurs. The cavity of the test section with a certain size effectively makes the inherent sound frequency of the cavity and the frequency of vortex shedding generated by the fluid bypassing the heat transfer tube achieve a "frequency locking" phenomenon.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A wind tunnel test section device for acoustic resonance testing of heat transfer tubes, characterized in that: The test section device is a rectangular chamber, including a top plate, a bottom plate, a front side plate, a rear side plate, a detachable test block, and an angle display dial. The top plate, the bottom plate, the front side plate, and the rear side plate are assembled in an inlaid manner. The detachable test block is respectively installed on the front side plate and the rear side plate. The detachable test block is provided with one or more through holes for installing and fixing the heat transfer tube. The diameter D of the heat transfer tube is 12-35 mm. The angle dial is respectively located on the front side plate and the rear side plate. The center position of the top plate and the bottom plate is provided with a mounting hole for the acoustic detection device. The size range of the rectangular chamber cross section is (300-500) mm*(300-500) mm. A connecting flange is provided at one end of the rectangular chamber. The top plate and the bottom plate are made of acrylic material, and the thickness thereof is not less than 15 mm; The front side plate and the rear side plate are provided with reserved holes for installing detachable experimental blocks; A 0-360° angle display dial is arranged around the reserved holes of the front side plate and the rear side plate; A protrusion is provided on the outer wall of the detachable experimental block, and a slide rail corresponding to the protrusion is provided on the inner wall of the reserved hole. The protrusion slides in the slide rail, and the size of the slide rail is adapted to the protrusion. The slide rail is provided with a notch for installing and removing the protrusion, and the size of the notch is adapted to the protrusion.

2. The wind tunnel test section device for acoustic resonance testing of heat transfer tubes according to claim 1, characterized in that: The detachable experimental block is a circular block structure with a radius of 6D-9D, and the diameter of the through hole is 0.6D.

3. The wind tunnel test section device for heat transfer tube acoustic resonance testing according to claim 1, characterized in that: The upper surface of the detachable experimental block is provided with a mounting groove, and a detachable indicating rod is arranged in the mounting groove, and the indicating rod indicates the scale on the angle display dial.

4. The wind tunnel test section device for heat transfer tube acoustic resonance testing according to claim 1, characterized in that: The diameter of the mounting hole of the acoustic detection device is 0.2D.

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