Stall sampling device for induced draft fan

Abstract

The utility model discloses an induced draft fan stall sampling device which comprises a fan shell, fan blades and a stall sampling device body, the connection mode of a stall sampling pipe and a connector is changed from welding to threaded connection, the welding quality problem is avoided, and if the problems such as blockage occur in the operation process, the stall sampling pipe can be detached, and the fan blades can be taken down. The stall sampling pipe is dredged, the heat tracing band is additionally arranged outside the stall sampling pipe, the heat tracing band can effectively prevent the phenomena of condensation and blockage in the stall sampling pipe through active heating, the accuracy and reliability of stall measurement of the induced draft fan are effectively improved, misoperation or rejection of stall protection is radically treated, and safe operation of the induced draft fan is guaranteed.

Description

Technical Field

[0001] This utility model relates to the technical field of fan pressure sampling devices, specifically a stall sampling device for an induced draft fan. Background Technology

[0002] The induced draft fans at Heyuan Power Plant use axial flow fans. Axial flow fan blades are typically airfoil-shaped. When the fan is in its stable operating range, the angle between the airflow direction and the blade chord is called the angle of attack α. If α is lower than a critical value (e.g....), Figure 5 When airflow is applied along the blade surface, according to Bernoulli's equation, the pressure on the concave surface of the airfoil is greater than the pressure on the convex surface. This pressure is decomposed into lift perpendicular to the blade surface and drag parallel to the blade, with lift being greater than drag. Once α exceeds a critical value, the boundary layer on the back of the blade is disrupted, and the airflow leaves the blade surface to form vortices, causing a decrease in lift and an increase in drag. At the same time, the fan pressure drops sharply, which is the phenomenon of fan stall. As α increases, partial blockage of the flow channel may even occur.

[0003] Prolonged stall time of induced draft fans can cause blade cracking and damage to mechanical parts. Therefore, stall protection is provided to trip the fan and protect the blades in the event of stall. Existing induced draft fan stall measurement devices are prone to condensation, blockage, and sampling tube cracking, which often leads to false tripping or failure of protection.

[0004] Condensation occurs because the induced draft fan is located at the boiler flue outlet. The flue gas produced by combustion in the furnace carries some dust and water vapor. When the flue gas reaches the induced draft fan, the temperature drops sharply. Once it is below the dew point temperature, condensation will occur. Especially during the rainy season, the fuel and flue gas have a high water content and the ambient temperature of the induced draft fan is low. The rate of condensation of water in the stall sampling tube will be faster, making condensation more likely to occur.

[0005] The blockage is due to the influence of the dust removal efficiency of the electrostatic precipitator. When the flue gas reaches the induced draft fan, there is still a certain amount of dust. Since the relative wind speed at the stall sampling port is relatively low, the dust is easy to fall and accumulate. When the flue gas with high humidity condenses at the sampling port, the ash in the flue gas will be adsorbed on the inner wall of the sampling tube, gradually blocking the sampling tube.

[0006] The sampling tube cracks because the high and low pressure sampling holes of the sampling device are close together, which makes welding difficult. The welding quality at the factory has a significant impact, and problems such as pores and cracks are prone to occur at the root of the sampling tube and the sampling device. Due to the vibration during the operation of the fan, the sampling tube with welding quality problems will crack over time, causing the stall protection to malfunction or fail to operate. Utility Model Content

[0007] (a) Technical problems to be solved

[0008] To address the shortcomings of existing technologies, this invention provides a stall sampling device for induced draft fans, which solves the aforementioned problems.

[0009] (II) Technical Solution

[0010] To achieve the above objectives, this utility model provides the following technical solution: a stall sampling device for an induced draft fan, comprising a fan housing 1, a fan blade 2, and a stall sampling device 4. The fan blade 2 is disposed inside the fan housing 1, and a mounting hole 3 is provided on the outer side of the fan housing 1. The stall sampling device 4 is connected to the mounting hole 3 of the fan housing 1. The stall sampling device 4 includes a connector 41, a high-pressure side sampling hole 42, a low-pressure side sampling hole 43, a partition 44, a stall sampling tube 45, a heating cable 46, a clamping sleeve 47, and a hexagonal nut 48. High-pressure side sampling holes are respectively provided on the left and right sides inside the connector 41. The high-pressure side sampling port 42 and the low-pressure side sampling port 43 are provided, and a partition 44 is provided between the high-pressure side sampling port 42 and the low-pressure side sampling port 43. The partition 44 is fixed to the inner middle part of the connector 41. The outer ends of the high-pressure side sampling port 42 and the low-pressure side sampling port 43 are connected to the stall sampling tube 45, and the stall sampling tube 45 is threaded to the connector 41. The outer side of the stall sampling tube 45 is wrapped with a heat tracing cable 46. The outer end of the stall sampling tube 45 is sealed by a ferrule 47. The connector 41 is threaded to the mounting hole 3 of the fan housing 1. The connector 41 and the fan housing 1 are locked and fixed by a hexagonal nut 48.

[0011] Preferably, the middle part of the ferrule 47 is connected to the hose 49, and the two stall sampling tubes 45 are respectively connected to the differential pressure switch 410 through the hose 49.

[0012] Preferably, the connection between the stall sampling tube 45 and the connector 41 is sealed, and the stall sampling tube 45 is sealed to the ferrule 47.

[0013] Preferably, the inner diameters of the high-pressure side sampling port 42, the low-pressure side sampling port 43, and the stall sampling tube 45 are the same, and the inner diameters of the high-pressure side sampling port 42, the low-pressure side sampling port 43, and the stall sampling tube 45 are all twelve millimeters.

[0014] Preferably, the high-pressure side sampling hole 42 and the low-pressure side sampling hole 43 of the connector 41 are connected to the inside of the fan housing 1, and the end of the connector 41 near the fan blade 2 is flush with the inner wall of the fan housing 1.

[0015] Preferably, the connection between the connector 41 and the fan housing 1 is sealed.

[0016] (III) Beneficial Effects

[0017] This invention provides a stall sampling device for induced draft fans. It offers the following advantages: The connection between the stall sampling tube and the connector is changed from welding to a threaded connection, avoiding welding quality issues. Furthermore, if blockages occur during operation, the stall sampling tube can be removed and cleared. Adding a heating element to the outside of the stall sampling tube effectively prevents condensation and blockages, thus significantly improving the accuracy and reliability of stall measurement for induced draft fans. This also eliminates the possibility of false or failed stall protection activation, ensuring the safe operation of the induced draft fan. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of this utility model;

[0019] Figure 2 This utility model Figure 1 A magnified view of a portion of area A;

[0020] Figure 3 This is a schematic diagram of the stall sampling device in this utility model;

[0021] Figure 4 This is a bottom view of the connector structure in this utility model;

[0022] Figure 5 This is a diagram illustrating the stall principle of an axial flow fan.

[0023] In the diagram: Fan housing-1, Fan blade-2, Mounting hole-3, Stall sampling device-4, Connector-41, High-pressure side sampling hole-42, Low-pressure side sampling hole-43, Spacing plate-44, Stall sampling tube-45, Heating tape-46, Compression fitting-47, Hex nut-48, Hose-49, Differential pressure switch-410. Detailed Implementation

[0024] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0025] Please see Figure 1 This utility model provides a technical solution for a stall sampling device for an induced draft fan: a stall sampling device for an induced draft fan includes a fan housing 1, a fan blade 2 and a stall sampling device 4. The fan blade 2 is disposed inside the fan housing 1, and an installation hole 3 is provided on the outer side of the fan housing 1. The stall sampling device 4 is connected to the installation hole 3 of the fan housing 1.

[0026] Please see Figure 2-4The stall sampling device 4 includes a connector 41, a high-pressure side sampling hole 42, a low-pressure side sampling hole 43, a partition 44, a stall sampling tube 45, a heating tape 46, a retainer 47, and a hexagonal nut 48. The connector 41 has a high-pressure side sampling hole 42 and a low-pressure side sampling hole 43 on its left and right sides respectively. A partition 44 is provided between the high-pressure side sampling hole 42 and the low-pressure side sampling hole 43. The partition 44 is fixed to the inner middle part of the connector 41. The outer ends of the high-pressure side sampling hole 42 and the low-pressure side sampling hole 43 are connected to the stall sampling tube 45. The stall sampling tube 45 is threaded to the connector 41. The outer side of the stall sampling tube 45 is wrapped with the heating tape 46. The outer end of the stall sampling tube 45 is sealed by the retainer 47. The connector 41 is threaded to the mounting hole 3 of the fan housing 1. The connector 41 and the fan housing 1 are locked and fixed by the hexagonal nut 48.

[0027] The middle part of the ferrule 47 is connected to the hose 49, and the two stall sampling tubes 45 are respectively connected to the differential pressure switch 410 through the hose 49.

[0028] The connection between the stall sampling tube 45 and the connector 41 is sealed, and the stall sampling tube 45 is sealed to the ferrule 47. The connection between the connector 41 and the fan housing 1 is sealed to prevent gas leakage, ensure the accuracy of pressure signal transmission, reduce pressure loss due to poor sealing, and improve the detection sensitivity of the differential pressure switch 410.

[0029] The high-pressure side sampling port 42, the low-pressure side sampling port 43, and the stall sampling tube 45 have the same inner diameter, and the inner diameter of the high-pressure side sampling port 42, the low-pressure side sampling port 43, and the stall sampling tube 45 is 12 mm. This avoids the throttling effect caused by sudden changes in pipe diameter, ensures that the pressure signal is transmitted without attenuation, and improves the response speed and accuracy of stall detection.

[0030] The high-pressure side sampling port 42 and the low-pressure side sampling port 43 of the connector 41 are connected to the inside of the fan housing 1, and the end of the connector 41 near the fan blade 2 is flush with the inner wall of the fan housing 1 to avoid the protruding structure from disturbing the airflow.

[0031] In use, the connector 41 of the stall sampling device 4 is threaded onto the outer casing 1 of the induced draft fan, with its bottom flush with the inner surface of the outer casing 1. It is then secured externally with a fixed hexagonal nut 48. When the induced draft fan is running, the fan blades 2 rotate clockwise, and the blades of the fan blades 2 sweep across the high-pressure side sampling hole 42 and the low-pressure side sampling hole 43 in sequence. The differential pressure switch 410 measures the differential pressure between the high-pressure side sampling tube 42 and the low-pressure side sampling tube 43. When the differential pressure is greater than 500 Pa, it is determined that the induced draft fan has stalled.

[0032] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A fan stall sampling device, comprising a fan shell (1) and a fan blade (2), the fan blade (2) is arranged inside the fan shell (1), and a mounting hole (3) is arranged on the outer side of the fan shell (1); characterized in that It also includes a stall sampling device (4), which is connected with the mounting hole (3) of the fan shell (1), the stall sampling device (4) includes a connecting head (41), a high-pressure side sampling hole (42), a low-pressure side sampling hole (43), a spacer (44), a stall sampling tube (45), a heating band (46), a sleeve (47) and a hexagonal nut (48), the inside of the connecting head (41) is provided with a high-pressure side sampling hole (42) and a low-pressure side sampling hole (43) on the left and right sides respectively, and a spacer (44) is arranged between the high-pressure side sampling hole (42) and the low-pressure side sampling hole (43), the spacer (44) is fixed to the inner middle part of the connecting head (41), the outer side end of the high-pressure side sampling hole (42) and the low-pressure side sampling hole (43) is connected with the stall sampling tube (45), and the stall sampling tube (45) is screwed with the connecting head (41), the outer side of the stall sampling tube (45) is wrapped with a heating band (46), the outer side end of the stall sampling tube (45) is capped by a sleeve (47), the connecting head (41) is screwed with the mounting hole (3) of the fan shell (1), and the connecting head (41) is locked and fixed with the fan shell (1) through a hexagonal nut (48).

2. A stall sampling device for a fan as claimed in claim 1, wherein: The middle part of the sleeve (47) is connected with a hose (49), and the two stall sampling tubes (45) are respectively connected with a differential pressure switch (410) through the hose (49).

3. A stall sampling device for a fan as defined in claim 1, wherein: The connection between the stall sampling tube (45) and the connecting head (41) is sealingly arranged, and the stall sampling tube (45) is sealingly connected with the sleeve (47).

4. A stall sampling device for a fan as defined in claim 1, wherein: The inner diameters of the high-pressure side sampling hole (42), the low-pressure side sampling hole (43) and the stall sampling tube (45) are consistent, and the inner diameters of the high-pressure side sampling hole (42), the low-pressure side sampling hole (43) and the stall sampling tube (45) are all twelve millimeters.

5. A stall sampling device for a fan as defined in claim 1, wherein: The high-pressure side sampling hole (42), the low-pressure side sampling hole (43) and the stall sampling tube (45) of the connecting head (41) are in communication with the inside of the fan shell (1), and the end of the connecting head (41) close to the fan blade (2) is flush with the inner wall of the fan shell (1).

6. A stall sampling device for a fan as defined in claim 1, wherein: The connection between the connecting head (41) and the fan shell (1) is sealingly arranged.

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