Air compressor cooling structure, air compressor

Abstract

The present invention provides an air compressor cooling structure and an air compressor, wherein the air compressor cooling structure includes a casing, a motor rotor is arranged in the casing, the motor rotor includes a second short shaft and a first short shaft arranged at intervals along the axial direction of the motor rotor, the second short shaft is provided with a thrust plate corresponding to the air-floating axial bearing, the shaft end of the first short shaft is connected to a first impeller, a first cooling air channel is constructed on the casing, a flow channel is constructed in the first short shaft, and the cooling air flow outside the casing is discharged to the outside of the casing after passing through the first cooling air channel and the flow channel. According to the present invention, the first short shaft and the magnetic steel at one end of the first short shaft can be cooled to dissipate heat, the temperature rise of the motor rotor can be reduced, the anti-demagnetization ability of the magnetic steel can be improved, the deformation of the entire shaft length can be reduced, and the first impeller can be prevented from scratching the volute and causing the whole machine to fail.

Description

Technical Field

[0001] The invention belongs to the technical field of compressors, and in particular relates to an air compressor cooling structure and an air compressor. Background Art

[0002] At present, the air-suspended centrifugal two-stage air compressor is composed of a first-stage volute, a first-stage impeller, a second-stage volute, a second-stage impeller, a first-stage diffuser, a second-stage diffuser, a front cover, a rear cover, a water-cooled casing, a permanent magnet motor stator, a permanent magnet motor rotor, an air-suspended axial bearing assembly, and an air-suspended radial bearing assembly.

[0003] Among them: the permanent magnet motor rotor includes a front short shaft, a rear short shaft, a magnetic steel, and a sleeve (alloy / carbon fiber material); the water-cooled casing is provided with a cooling water channel, usually a spiral water channel or an axial U-shaped water channel; taking the secondary side as an example, the gap between the secondary impeller and the secondary volute is the blade tip gap δ, δ mainly affects the aerodynamic efficiency. During operation, the larger δ is, the lower the aerodynamic efficiency is.

[0004] The original technical structure currently has the following difficulties:

[0005] 1. Unable to effectively cool the rotor

[0006] High-speed permanent magnet motors have the characteristics of high speed, small size and high efficiency. At present, centrifugal air compressors usually use high-speed permanent magnet motors. The motor stator is cooled and dissipated through the cooling water channel on the casing, but the motor rotor is not cooled separately and effectively, and can only dissipate heat from the stator to the outside through thermal radiation. High-speed permanent magnet motors are different from traditional motors. They have high frequency and small size. The high-frequency harmonics of the current cause serious heating of the magnetic steel and the sheath (when a metal sheath is used). If a carbon fiber sheath is used, it will make it more difficult to dissipate the heat generated by the magnetic steel. At the same time, the heat dissipation conditions are more difficult due to the small size of the whole machine. In summary, the rotor temperature rise is more serious when the high-speed motor is running. The higher temperature rise will cause the magnetic steel to demagnetize and the motor performance will decline, and even cause the sheath to fail and become dangerous. Therefore, how to effectively cool the rotor is the focus of the air compressor structural design.

[0007] 2. The axial elongation of the rotor causes wear on the impeller and volute

[0008] High-speed motors are usually equipped with special bearings, such as magnetic bearings, air bearings, and sliding bearings. The difference between these bearings and traditional ball bearings is that traditional ball bearings are respectively arranged on both sides of the rotor to achieve radial and axial limit of the rotor. However, for the above-mentioned special bearings, the radial bearing can achieve radial limit of the rotor, but the axial bearing is only arranged on one side for axial limit. When the temperature rise of the rotor is high, it will cause the entire shaft to deform and stretch toward both ends with the thrust plate (due to limit reasons) as the center. According to the material thermal deformation formula: σ=L·α·ΔT, where σ is the thermal deformation, α is the thermal expansion coefficient, and ΔT is the temperature rise. The distance L2 between the secondary impeller side and the thrust plate is much larger than the distance L1 between the primary impeller side and the thrust plate. Combined with the above formula, when the rotor temperature rises, the thermal deformation from the thrust plate to the secondary impeller side is much larger than the other side. At this time, the blade tip clearance δ between the secondary impeller and the volute becomes smaller. If the rotor cooling effect is poor, the blade tip clearance δ will be sharply reduced. In severe cases, the impeller will rub against the volute, resulting in abnormal performance or damage to the entire machine. If the design value of δ is increased to prevent scratches, the aerodynamic efficiency of the air compressor will be seriously reduced in the low-speed area (because the rotor temperature rise increases with the operating speed). The rotor temperature rise in the low-speed area is not obvious, and the larger blade tip clearance reduces the efficiency of the entire machine. Summary of the invention

[0009] Therefore, the present invention provides an air compressor cooling structure and an air compressor, which can overcome the shortcomings of the air compressor in the prior art, such as the single-end axial positioning of the rotating shaft, the large deformation of the rotating shaft extension when the motor rotor, especially the rotating shaft, is poorly cooled, resulting in a sharp decrease in the blade tip clearance, which may cause the impeller and the volute to rub against each other, resulting in abnormal performance or even damage to the whole machine.

[0010] In order to solve the above problems, the present invention provides an air compressor cooling structure, including a casing, a motor rotor is arranged in the casing, the motor rotor includes a second short shaft and a first short shaft arranged at intervals along the axial direction of the motor rotor, a thrust plate corresponding to an air-floating axial bearing is arranged on the second short shaft, a first impeller is connected to the axial end of the first short shaft, a first cooling air duct is constructed on the casing, a flow channel is constructed in the first short shaft, and the cooling air flow outside the casing is discharged to the outside of the casing after passing through the first cooling air duct and the flow channel.

[0011] In some embodiments, the first short shaft is rotatably supported on a first end cover, the first end cover is disposed at the first end of the housing, a second cooling air duct is constructed on the first end cover, and the cooling air flow in the first cooling air duct can enter the flow channel via the second cooling air duct.

[0012] In some embodiments, a first diffuser is connected to a side of the first end cover facing the first impeller, a third cooling air passage is configured on the first diffuser, and the cooling air flow in the second cooling air passage can enter the through-flow passage via the third cooling air passage.

[0013] In some embodiments, the first short shaft has a shoulder annular surface facing the first impeller side, the first diffuser has an axial boss extending toward the shoulder annular surface, the inlet of the flow channel is located on the shoulder annular surface, the outlet of the third cooling air channel is located on the axial boss, and the outlet of the third cooling air channel and the inlet of the flow channel can be aligned in the axial direction of the motor rotor.

[0014] In some embodiments, the first diffuser is made of a wear-resistant material.

[0015] In some embodiments, the amount of the axial gap formed between the axial boss and the shoulder ring is δ1, the tip clearance of the first impeller is δ, and δ1<δ.

[0016] In some embodiments, δ−δ1>0.15 mm.

[0017] In some embodiments, a magnetic steel is sandwiched between the second short axis and the first short axis, and the flow channel has a flow channel section arranged adjacent to the magnetic steel; and / or, the flow path of the flow channel is U-shaped or V-shaped; and / or, the flow channel has multiple flow channels.

[0018] In some embodiments, a lubricating coating is provided on the outer circumferential wall of the first short shaft in an area corresponding to the air-floating radial bearing; and / or a second impeller is connected to the end of the second short shaft; and / or a cooling water channel is constructed on the casing.

[0019] The present invention also provides an air compressor, comprising the above-mentioned air compressor cooling structure.

[0020] The present invention provides an air compressor cooling structure and an air compressor. By constructing the flow channel on the first short shaft, the cooling air flow in the first cooling air channel can enter the first short shaft, thereby dissipating the heat and cooling the first short shaft and the magnetic steel at one end of the first short shaft, reducing the temperature rise of the motor rotor, improving the anti-demagnetization ability of the magnetic steel, reducing the deformation of the entire shaft length, and preventing the first impeller from scratching the volute and causing the entire machine to fail. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of the internal structure of an air compressor cooling structure according to an embodiment of the present invention;

[0022] Figure 2 for Figure 1 A partial enlarged view of the middle A;

[0023] Figure 3 for Figure 1 A partial enlarged view of point B in the middle;

[0024] Figure 4 for Figure 1 Schematic diagram of the three-dimensional structure of the first short axis;

[0025] Figure 5 The figure is a schematic diagram of the internal structure of an air compressor cooling structure according to another embodiment of the present invention.

[0026] The reference numerals are as follows:

[0027] 101. first-stage volute; 102. second impeller; 103. second-stage volute; 104. first impeller; 105. second diffuser; 106. first diffuser; 1061. axial boss; 107. second end cover; 108. first end cover; 109. casing; 110. motor stator; 111. motor rotor; 112. air-floating axial bearing; 113. air-floating radial bearing; 114. thrust plate; 115. second short shaft; 116. first short shaft; 117. magnetic steel; 118. jacket (alloy / carbon fiber material); 119. cooling water channel; 201. flow channel; 202. first cooling air channel; 2021. second cooling air channel; 2022. third cooling air channel. DETAILED DESCRIPTION

[0028] See also Figures 1 to 5As shown, according to an embodiment of the present invention, an air compressor cooling structure is provided, including a casing 109, in which a motor rotor 111 is arranged, and the motor rotor 111 includes a second short shaft 115 and a first short shaft 116 arranged at intervals along the axial direction of the motor rotor 111, and the second short shaft 115 is provided with a thrust plate 114 corresponding to the air-floating axial bearing 112, and the axial end of the first short shaft 116 is connected to the first impeller 104, and a first cooling air duct 202 is constructed on the casing 109, and a flow channel 201 is constructed in the first short shaft 116, and the cooling air flow outside the casing 109 is discharged to the outside of the casing 109 after passing through the first cooling air duct 202 and the flow channel 201. In this technical solution, by constructing the flow passage 201 on the first short shaft 116, the cooling airflow in the first cooling air passage 202 can enter the first short shaft 116, so that the first short shaft 116 and the magnetic steel 117 at one end of the first short shaft 116 can be cooled and dissipated, the temperature rise of the motor rotor 111 can be reduced, the anti-demagnetization ability of the magnetic steel 117 (such as a permanent magnet) can be improved, the deformation of the entire shaft length can be reduced, and the first impeller 104 can be prevented from scratching the volute and causing the whole machine to fail. It can be understood that since the elongation of the entire shaft is reduced, there is no need to give a large design margin when designing the aerodynamic tip clearance (usually the tip clearance design should consider: assembly tolerance superposition + thermal elongation of the entire shaft), so the aerodynamic efficiency can be effectively improved.

[0029] The first short shaft 116 is rotatably supported on the first end cover 108 (specifically, through the air-floating radial bearing 113). The first end cover 108 is arranged at the first end of the housing 109. The first end cover 108 is configured with a second cooling air passage 2021. The cooling airflow in the first cooling air passage 202 can enter the through-flow passage 201 via the second cooling air passage 2021, and the cooling airflow can cool the first end cover 108. Furthermore, the first end cover 108 is connected to the first diffuser 106 on the side facing the first impeller 104. The first diffuser 106 is configured with a third cooling air passage 2022. The cooling airflow in the second cooling air passage 2021 can enter the through-flow passage 201 via the third cooling air passage 2022, so as to further dissipate heat and cool the first diffuser 106.

[0030] In some embodiments, the first short shaft 116 has a shoulder annular surface facing the side of the first impeller 104, the first diffuser 106 has an axial boss 1061 extending toward the shoulder annular surface, the inlet of the flow channel is located on the shoulder annular surface, the outlet of the third cooling air channel 2022 is located on the axial boss 1061, and the outlet of the third cooling air channel 2022 and the inlet of the flow channel 201 can be aligned in the axial direction of the motor rotor 111, so that the cooling air flow in the third cooling air channel 2022 can more easily enter the flow channel 201.

[0031] The first diffuser 106 is made of a wear-resistant material to enhance the wear resistance of the first diffuser 106 and increase its service life.

[0032] In some embodiments, the amount of the axial clearance formed between the axial boss 1061 and the shoulder ring is δ1, the blade tip clearance of the first impeller 104 is δ, δ1<δ, specifically, δ-δ1>0.15mm. In this technical solution, when the operating environment of the air compressor is extremely harsh and the elongation of the rotor after cooling is still greater than the blade tip clearance δ, since δ1 is set to be slightly smaller than the blade tip clearance δ, and the diffuser is made of wear-resistant material, the first impeller 104 and the corresponding secondary volute can be protected; otherwise, the aerodynamic performance of the first impeller 104 and the volute will drop sharply after wear, and the entire machine will be scrapped, while the wear of the first diffuser 106 and the shaft will not affect the performance of the air compressor.

[0033] The through-flow channel 201 has a flow channel section disposed adjacent to the magnetic steel 117 so as to sufficiently dissipate heat and cool the magnetic steel 117. The flow path of the through-flow channel 201 is U-shaped (eg Figure 4 As shown) or V-shaped, preferably U-shaped, to have a flow channel section parallel to the radial direction of the magnetic steel 117 to ensure that the cooling airflow fully cools the magnetic steel 117. It can be understood that the connected flow channel sections at both ends should be connected in the form of arc flow channels to reduce the energy loss of the cooling airflow and thus improve the cooling effect. Figure 5 A flow channel 201 with a right-angle bend structure is shown, which causes greater energy loss to the cooling airflow compared with the aforementioned U-shape, but can also be used in some cases; the flow channel 201 has multiple flow channels 201, and the multiple flow channels 201 are arranged at circumferential intervals along the first short axis 116 to ensure that the cooling airflow in the third cooling air channel 2022 can enter smoothly.

[0034] In some embodiments, a lubricating coating is provided on the outer circumferential wall of the first short shaft 116 in an area corresponding to the air-floating radial bearing 113. The lubricating coating is specifically a lubricating coating of an organic polymer material. Such coatings are sensitive to temperature. High temperature will cause the coating to fail, and eventually shorten the life of the bearing. In the technical solution of the present invention, Figure 3 As shown (the arrow in the figure indicates the cooling airflow), since there is a gap δ1 between the first diffuser 106 and the first short shaft 116, although most of the cooling gas flowing out of the first diffuser 106 enters the flow channel 201 in the first short shaft 116, some gas will still pass through the working air gap of the bearing between the air-floating radial bearing 113 and the first short shaft 116, and then flow to the air-floating radial bearing 113 on the other side through the stator-rotor air gap. This cooling flow channel cools the surface of the air-floating radial bearing 113 and the motor rotor 111 at the same time, reduces the bearing temperature rise, and increases the life of the surface coating. At the same time, this cooling airflow also makes the air inside the motor flow, effectively improving the load-bearing performance of the air-floating bearing.

[0035] See also Figure 1 As shown, the end of the second short shaft 115 is connected to the second impeller 102. At this time, the second impeller 102 is a first-stage impeller, and the first impeller 104 is a second-stage impeller. At this time, the corresponding air compressor is a two-stage air compressor.

[0036] The casing 109 is provided with a cooling water channel 119, which can cool the cooling gas in the first cooling air channel 202 by heat exchange. Specifically, the cooling gas can be provided by an external air source. In the absence of an external air source, a portion of the compressed gas can be diverted from the primary or secondary exhaust side of the air compressor into the cooling channel.

[0037] According to an embodiment of the present invention, there is also provided an air compressor, comprising the above-mentioned air compressor cooling structure.

[0038] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0039] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention. The above are only preferred embodiments of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present invention, and these improvements and variations should also be regarded as the protection scope of the present invention.

Claims

1. An air compressor cooling structure, characterized in that: The invention comprises a casing (109), wherein a motor rotor (111) is arranged in the casing (109), wherein the motor rotor (111) comprises a second short shaft (115) and a first short shaft (116) which are arranged at intervals along the axial direction of the motor rotor (111), wherein the second short shaft (115) is provided with a thrust plate (114) corresponding to an air-floating axial bearing (112), and the shaft end of the first short shaft (116) is connected to a first impeller (104), and the casing (109) is provided with a first cooling air duct (202). ), a flow passage (201) is configured inside the first short shaft (116), and a cooling airflow outside the housing (109) is discharged to the outside of the housing (109) after passing through the first cooling air passage (202) and the flow passage (201); the first short shaft (116) is rotatably supported on a first end cover (108), the first end cover (108) is provided at a first end of the housing (109), a second cooling air passage (2021) is configured on the first end cover (108), and the first The cooling air flow in the cooling air duct (202) can enter the through-flow channel (201) via the second cooling air duct (2021); the first end cover (108) is connected to a first diffuser (106) on a side facing the first impeller (104); a third cooling air duct (2022) is configured on the first diffuser (106); the cooling air flow in the second cooling air duct (2021) can enter the through-flow channel (201) via the third cooling air duct (2022); the first short The shaft (116) has a shoulder annular surface facing one side of the first impeller (104); the first diffuser (106) has an axial boss (1061) extending toward the shoulder annular surface; the inlet of the flow channel (201) is located on the shoulder annular surface; the outlet of the third cooling air channel (2022) is located on the axial boss (1061); and the outlet of the third cooling air channel (2022) and the inlet of the flow channel (201) can be aligned in the axial direction of the motor rotor (111).

2. The air compressor cooling structure according to claim 1, characterized in that: The first diffuser (106) is made of wear-resistant material.

3. The air compressor cooling structure according to claim 1, characterized in that: The amount of the axial clearance formed between the axial boss (1061) and the shaft shoulder annular surface is δ1, and the tip clearance of the first impeller (104) is δ, where δ1<δ.

4. The air compressor cooling structure according to claim 3, characterized in that: δ—δ1>0.15mm.

5. The air compressor cooling structure according to claim 1, characterized in that: A magnetic steel (117) is sandwiched between the second short axis (115) and the first short axis (116); the flow channel (201) has a flow channel section arranged adjacent to the magnetic steel (117); and / or the flow path of the flow channel (201) is U-shaped or V-shaped; and / or the flow channel (201) has a plurality of channels.

6. The air compressor cooling structure according to claim 1, characterized in that: A lubricating coating is provided on the outer circumferential wall of the first short shaft (116) in an area corresponding to the air-floating radial bearing (113); and / or, the end of the second short shaft (115) is connected to a second impeller (102); and / or, a cooling water channel (119) is constructed on the casing (109).

7. An air compressor, characterized in that: The air compressor cooling structure comprises the air compressor cooling structure according to any one of claims 1 to 6.

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