Recirculating sheath flow type virtual impactor

Abstract

The utility model discloses a recirculation sheath flow type virtual impactor which comprises a virtual impactor cavity, an air pump and filter paper, a radioactive aerosol air inlet is formed in the top of the virtual impactor cavity and connected with an air outlet through an inner flow channel, and a main air pump is installed at the air outlet. Recycling sheath flow channels are arranged on two sides of the virtual impactor cavity, the upper ends of the recycling sheath flow channels are communicated with the air inlet, and the lower ends of the recycling sheath flow channels are respectively communicated with the sampling cavity air outlet and the virtual impactor cavity air outlet; the sampling cavity comprises an artificial radioactive aerosol channel and a radon daughter aerosol channel; a first groove is formed in the artificial radioactive aerosol channel; a second groove and a third groove are formed in an outlet of the radon daughter aerosol channel; a first air pump and a second air pump are mounted at the bottom of an outlet of the radon daughter aerosol channel; according to the utility model, the gas filtered by the filter paper is used as clean air through the recirculation sheath flow channel, so that the wall surface loss is reduced, and meanwhile, the instrument structure is simpler.

Description

Technical Field

[0001] The utility model relates to the field of radioactive aerosol, and particularly relates to a recirculating sheath flow virtual impactor. Background Art

[0002] Generally, the particle size range of radioactive aerosol is 0.1 - 20 μm, among which the proportion of aerosol particles with a size of 1 - 5 μm is more than 80%. For particles with a size of 10 - 20 μm, their movement is mainly caused by gravity sedimentation as they are little affected by the flow field; for particles with a size below 10 μm, especially particles around 1 μm, they are easily affected by the flow field disturbance, will remain suspended for a long time, and at the same time do slow sedimentation and diffusion movements. If radioactive aerosol is inhaled or ingested into the human body, the radioactive isotope will release radiation, directly irradiating the internal tissues, and this internal irradiation may cause damage to cells and tissues and increase the risk of cancer.

[0003] The sampling of artificial radioactive aerosol is often interfered by radon daughter aerosol. After sampling the radioactive aerosol, it is often necessary to correct the obtained energy spectrum data through algorithm deduction in subsequent data analysis to reduce the influence brought by the radon daughter tailing. To solve this problem, according to the characteristics of different aerodynamic diameters of natural and artificial radioactive aerosols, the virtual impact separation technology can be used to utilize the different inertia of particles with different diameters to separate the radon daughter aerosol and artificial radioactive aerosol before sampling, reduce the interference of radon daughter on the sampling of artificial radioactive aerosol, and facilitate the subsequent processing of energy spectrum data. In addition, in order to reduce the wall loss, clean air is often used to isolate the wall surface from the aerosol, but this requires additional clean air provided by the instrument for the virtual impactor. Therefore, a recirculating sheath flow virtual impactor is proposed, which can reduce the wall loss, improve the separation accuracy and sampling efficiency while separating the radon daughter aerosol, and simplify the instrument equipment of the virtual impactor. Summary of the Invention

[0004] The purpose of the utility model is to solve the influence of the interference of radon daughter aerosol on the sampling of artificial radioactive aerosol, and propose a recirculating sheath flow virtual impactor, which can reduce the wall loss, improve the separation accuracy and sampling efficiency while separating the radon daughter aerosol, and simplify the instrument equipment of the virtual impactor.

[0005] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0006] A recirculating sheath flow virtual impactor, comprising a virtual impactor cavity, a sampling cavity, a radioactive aerosol inlet, an internal flow channel, a recirculating sheath flow channel, an acceleration nozzle, a radon progeny aerosol channel, an artificial radioactive aerosol channel, a first groove, a third groove, a second air pump, an air outlet, a main air pump, a first air pump, a second groove, and a filter paper; the top of the virtual impactor cavity is provided with a radioactive aerosol inlet, which is connected to the air outlet through the internal flow channel, and a main air pump is installed at the air outlet; the two sides of the virtual impactor cavity are provided with recirculating sheath flow channels, the upper ends of which are communicated with the inlet, and the lower ends are respectively communicated with the bottom end of the sampling cavity and the air outlet of the virtual impactor cavity; the sampling cavity includes an artificial radioactive aerosol channel and a radon progeny aerosol channel; a first groove is provided in the artificial radioactive aerosol channel; a second groove and a third groove are provided at the outlet of the radon progeny aerosol channel; a first air pump is installed directly below the second groove, and a second air pump is installed directly below the third groove.

[0007] As a further improvement to the technical solution of the present utility model, the virtual impactor cavity has a left-right central symmetry structure.

[0008] As a further improvement to the technical solution of the present utility model, the inner upper corner of the recirculating sheath flow channel and the upper corner of the radon progeny aerosol channel are both in a semi-circular arc shape.

[0009] As a further improvement to the technical solution of the present utility model, the inner diameter of the radon progeny particle channel is larger than that of the artificial radioactive aerosol channel, and the inner diameter of the artificial radioactive aerosol channel is larger than that of the acceleration nozzle.

[0010] As a further improvement to the technical solution of the present utility model, the first groove is provided in the artificial radioactive aerosol channel near the collection nozzle, the second groove is provided in the left radon progeny aerosol channel of the sampling cavity, and the third groove is provided in the right radon progeny aerosol channel of the sampling cavity.

[0011] As a further improvement to the technical solution of the present utility model, the filter paper is fixed in a detachable filter membrane fixture and is respectively placed in the first groove, the second groove, and the third groove.

[0012] As a further improvement to the technical solution of the present utility model, the first air pump, the second air pump, and the main air pump are all adjustable air pumps; the first air pump is a leftward air extraction pump, the second air pump is a rightward air extraction pump, and the main air pump is a downward air extraction pump.

[0013] The beneficial effects of the present utility model are:

[0014] By using an air pump to control the flow rate, the secondary flow ratio and the sheath flow ratio are adjusted, improving the separation accuracy of radon daughter aerosol and the sampling efficiency of artificial radioactive aerosol. The gas filtered by the filter paper forms an autonomous recyclable sheath flow system through the recirculating sheath flow channel, thereby reducing the wall loss while separating the radon daughter aerosol and simplifying the instrument equipment of the virtual impactor. Description of the Drawings

[0015] The present utility model will be further described below in conjunction with the drawings and embodiments.

[0016] Figure 1 is a schematic structural diagram of the present utility model; Figure 2 is a three-dimensional structural diagram of the cavity of the present utility model; in the figure, 1. virtual impactor cavity, 2. sampling cavity, 3. radioactive aerosol inlet, 4. internal flow channel, 5. recirculating sheath flow channel, 6. acceleration nozzle, 7. radon daughter aerosol channel, 8. artificial radioactive aerosol channel, 9. first groove, 10. third groove, 11. second air pump, 12. outlet, 13. main air pump, 14. first air pump, 15. second groove, 16. filter paper. Specific Embodiments

[0017] The present utility model will be further described in detail below in conjunction with the drawings, so that those skilled in the art can implement it with reference to the description. The following embodiments are used to illustrate the present utility model, but are not used to limit the scope of the present utility model.

[0018] In this embodiment Figure 1 、 Figure 2 As shown, the present utility model provides a recirculating sheath flow type virtual impactor, including a virtual impactor cavity, an air pump, and a filter paper. The top of the virtual impactor cavity 1 is provided with a radioactive aerosol inlet 3, which is connected to the outlet 12 through the internal flow channel 4, and a main air pump 13 is installed at the outlet; the two sides of the virtual impactor cavity 1 are provided with recirculating sheath flow channels 5, the upper end is communicated with the radioactive aerosol inlet 3, and the lower end is respectively communicated with the bottom end of the sampling cavity 2 and the outlet 12; the sampling cavity 2 includes an artificial radioactive aerosol channel 8 and a radon daughter aerosol channel 7; a first groove 9 is provided in the artificial radioactive aerosol channel 8; a second groove 15 and a third groove 10 are provided at the outlet of the radon daughter aerosol channel 7; a first air pump 14 is installed directly below the second groove 15, and a second air pump 11 is installed directly below the third groove 10.

[0019] In this embodiment, the virtual impactor cavity 1 is overall symmetric about the left and right center, making the internal flow field distribution more uniform, reducing the turbulence, vortices and energy loss in the flow, and improving the stability of the flow.

[0020] In this embodiment, the upper inner corners of the recirculating sheath flow channel 5 and the upper corners of the radon daughter aerosol channel 7 are both semi-circular in shape, enabling the circulating fluid to flow along a smoother path, reducing the occurrence of flow separation, and preventing violent backflows and vortices when passing through elbows, thereby maintaining a more uniform streamline and velocity distribution, avoiding pressure fluctuations caused by changes in flow velocity, and ensuring the stability and reliability of the flow.

[0021] In this embodiment, the inner diameter of the radon daughter aerosol channel 7 is larger than that of the artificial radioactive aerosol channel 8, and the inner diameter of the artificial radioactive aerosol channel 8 is larger than that of the acceleration nozzle 6, enabling the filter paper to effectively collect artificial radioactive aerosol particles.

[0022] In this embodiment, the first groove 9 is provided near the collection nozzle of the artificial radioactive aerosol channel 8, the second groove 15 is provided in the radon daughter aerosol channel 7 on the left side of the sampling chamber 2, and the third groove 10 is provided in the radon daughter aerosol channel 7 on the right side of the sampling chamber 2.

[0023] As shown in this embodiment Figure 1 The filter paper 16 is fixed in a detachable filter membrane fixture and placed in the first groove 9, the second groove 15, and the third groove 10 respectively. After the radioactive aerosol is filtered by the filter paper, it becomes clean gas and is used as sheath flow.

[0024] In this embodiment, the first air pump 14, the second air pump 11, and the main air pump 13 are all adjustable air pumps; the first air pump 14 is a leftward air suction pump that pumps the gas filtered from the radon daughter aerosol channel 7 on the left side of the sampling chamber 2 into the left recirculating sheath flow channel 5, and the second air pump 11 is a rightward air suction pump that pumps the gas filtered from the radon daughter aerosol channel 7 on the right side of the sampling chamber 2 into the right recirculating sheath flow channel 5, thereby forming sheath flow on both sides of the radioactive aerosol in the inner flow path 4 and reducing wall losses. The main air pump 13 is a downward air suction pump that controls the secondary flow ratio and sheath flow ratio by adjusting the air pump, thereby improving the separation accuracy of the virtual impactor and the sampling efficiency of artificial radioactive aerosol.

[0025] Working principle: Start the main air pump 13. The radioactive aerosol is drawn from the radioactive aerosol inlet 3 into the inner flow path 4 and accelerated through the acceleration nozzle 6. Since the radon daughter aerosol and the artificial radioactive aerosol have different particle sizes, the radon daughter aerosol particles with smaller inertia follow the mainstream into the radon daughter aerosol channel 7, while the artificial radioactive aerosol particles with larger inertia do not follow the mainstream and enter the artificial radioactive aerosol channel 8. After the radioactive aerosol is filtered by the filter paper 16, a part of it is drawn into the recirculating sheath flow channel 5 by the first air pump 14 and the second air pump 11, forming sheath flow on both sides of the radioactive aerosol at the inner flow path 4 and reducing the wall losses of the virtual impactor, and the other part is discharged from the air outlet.

[0026] Finally, it should be noted that the above description is only a further improvement of the technical solution of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present utility model.

Claims

1. A recirculating sheath flow virtual impactor, comprising a virtual impactor cavity (1), a sampling cavity (2), a radioactive aerosol inlet (3), an internal flow channel (4), a recirculating sheath flow channel (5), an acceleration nozzle (6), a radon daughter aerosol channel (7), an artificial radioactive aerosol channel (8), a first groove (9), a third groove (10), a second air pump (11), an air outlet (12), a main air pump (13), a first air pump (14), a second groove (15), a filter paper (16), characterized in that, The top of the virtual impactor cavity (1) is provided with a radioactive aerosol inlet (3), which is connected to the air outlet (12) through an internal flow channel (4), and a main air pump (13) is installed at the air outlet; two sides of the virtual impactor cavity (1) are provided with recirculating sheath flow channels (5), the upper ends of which are communicated with the radioactive aerosol inlet (3), and the lower ends are respectively communicated with the bottom end of the sampling cavity (2) and the air outlet (12); the sampling cavity (2) includes an artificial radioactive aerosol channel (8) and a radon daughter aerosol channel (7); a first groove (9) is provided in the artificial radioactive aerosol channel (8); a second groove (15) and a third groove (10) are provided at the outlet of the radon daughter aerosol channel (7); a first air pump (14) is installed directly below the second groove (15), and a second air pump (11) is installed directly below the third groove (10).

2. The recirculating sheath flow virtual impactor according to claim 1, characterized in that, The virtual impactor cavity (1) is of an overall left-right central symmetry structure.

3. A recirculating sheath flow virtual impactor according to claim 1, characterized in that, The inner upper corners of the recirculating sheath flow channels (5) and the upper corners of the radon daughter aerosol channels (7) are both in a semi-circular arc shape.

4. A recirculating sheath flow virtual impactor according to claim 1, wherein The inner diameter of the radon daughter aerosol channel (7) is larger than that of the artificial radioactive aerosol channel (8), and the inner diameter of the artificial radioactive aerosol channel (8) is larger than that of the acceleration nozzle (6).

5. A recirculating sheath flow virtual impactor according to claim 1, wherein The first groove (9) is arranged in the artificial radioactive aerosol channel (8) near the collection nozzle, the second groove (15) is arranged in the radon daughter aerosol channel (7) on the left side of the sampling cavity (2), and the third groove (10) is arranged in the radon daughter aerosol channel (7) on the right side of the sampling cavity (2).

6. A recirculating sheath flow virtual impactor according to claim 5, characterized in that, The filter paper (16) is fixed in a detachable filter membrane fixture and placed in the first groove (9), the second groove (15), and the third groove (10) respectively.

7. A recirculating sheath flow virtual impactor according to claim 1, wherein, The first air pump (14), the second air pump (11), and the main air pump (13) are all adjustable air pumps; the first air pump (14) is a leftward air suction pump, the second air pump (11) is a rightward air suction pump, and the main air pump (13) is a downward air suction pump.

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