CN217440317U

CN217440317U - Air compressor

Info

Publication number: CN217440317U
Application number: CN202220928815.6U
Authority: CN
Inventors: 杨国蟒; 曾轲
Original assignee: Gree Electric Appliances Inc of Zhuhai
Current assignee: Gree Electric Appliances Inc of Zhuhai
Priority date: 2022-04-21
Filing date: 2022-04-21
Publication date: 2022-09-16
Anticipated expiration: 2032-04-21

Abstract

The utility model provides an air compressor, including casing, rotor subassembly, the casing has first end plate, the rotor subassembly includes the pivot, the one end of pivot is connected with first impeller, the wheel hub orientation of first impeller one side of first end plate is equipped with first sealed bulge loop, first end plate orientation one side of first impeller has first sealed annular, first sealed bulge loop is in the first sealed annular, just first sealed bulge loop with can form labyrinth seal structure between the first sealed annular. According to the utility model discloses, do not increase can have bigger sealed length in the axial length of pivot to effectively reduce gaseous interstage and reveal, improved the air compressor performance.

Description

Air compressor

Technical Field

The utility model belongs to the technical field of the compressor is made, concretely relates to air compressor.

Background

The air compressor is also the focus of current research as the "heart" inside the vehicle fuel cell system. The direction and the size of the axial force of the air compressor are of great importance to the design of the gas bearing, meanwhile, the performance of the air compressor is reduced due to excessive interstage gas leakage, for the double-stage air compressor, due to the fact that the rotor assembly is improperly designed, the axial force is too large, the direction changes along with the change of the operation working condition, the safety and the stability of the gas axial bearing are reduced, and due to the fact that the length of the main shaft of the two stages is limited, the interstage gas leakage is large due to the fact that the length of the main shaft of the two stages is not enough, and the performance of the air compressor is affected.

SUMMERY OF THE UTILITY MODEL

Therefore, the utility model provides an air compressor can overcome and has the contradiction between the air compressor pivot main shaft sealing performance among the correlation technique and the axle length design, leads to air compressor to need to have bigger sealed length when having higher performance to lead to the too big not enough of pivot bearing length.

In order to solve the problem, the utility model provides an air compressor, including casing, rotor subassembly, the casing has first end plate, the rotor subassembly includes the pivot, the one end of pivot is connected with first impeller, the wheel hub orientation of first impeller one side of first end plate is equipped with first sealed bulge loop, first end plate orientation one side of first impeller has first sealed annular, first sealed bulge loop is in the first sealed annular, just first sealed bulge loop with can form labyrinth seal structure between the first sealed annular.

In some embodiments, the groove wall of the first sealing ring groove is provided with a first sealing comb tooth structure.

In some embodiments, on the axial cross section of the first impeller, the first sealing convex ring is convex towards one side of the first sealing ring groove, on the axial cross section of the first end plate, the first sealing comb tooth structure is convex towards one side of the first impeller, and/or the first sealing comb tooth structure is composed of Na first sealing teeth which are arranged at intervals along the axial direction of the rotating shaft, and Na is more than or equal to 8 and less than or equal to 11.

In some embodiments, the casing further has a second end plate disposed opposite to the first end plate, the other end of the rotating shaft is further connected with a second impeller, a second sealing convex ring is disposed on one side of the second end plate, which faces the hub of the second impeller, a second sealing ring groove is disposed on one side of the second impeller, the second sealing convex ring is disposed in the second sealing ring groove, and a labyrinth sealing structure can be formed between the second sealing convex ring and the second sealing ring groove.

In some embodiments, the groove wall of the second sealing ring groove is provided with a second sealing comb tooth structure; and/or the first end plate comprises a first outer ring plate and a first inner ring plate which are assembled and connected, first radial outer side sealing teeth corresponding to the first sealing comb tooth structures are arranged on the hole wall of an inner hole of the first outer ring plate, first radial inner side sealing teeth corresponding to the first sealing comb tooth structures are arranged on the outer circumferential wall of the first inner ring plate, and/or the second end plate comprises a second outer ring plate and a second inner ring plate which are assembled and connected, second radial outer side sealing teeth corresponding to the second sealing comb tooth structures are arranged on the hole wall of an inner hole of the second outer ring plate, and second radial inner side sealing teeth corresponding to the second sealing comb tooth structures are arranged on the outer circumferential wall of the second inner ring plate.

In some embodiments, the second sealing convex ring is convex towards one side of the second sealing ring groove on the axial section of the second impeller, the second sealing comb tooth structure is convex towards one side of the second impeller on the axial section of the second end plate, and/or the second sealing comb tooth structure is composed of Nb second sealing teeth arranged at intervals along the axial direction of the rotating shaft, and Nb is more than or equal to 11 and less than or equal to 14.

In some embodiments, Na ═ 10; alternatively, Nb ═ 12; or the ratio of the height of the first sealing tooth or the second sealing tooth to the pitch of the teeth is 1.3-1.5.

In some embodiments, the first seal tooth or the second seal tooth has a ratio of gauge height to tooth pitch of 1.44.

In some embodiments, the first impeller is a low pressure stage impeller, the second impeller is a high pressure stage impeller, the first impeller and the second impeller are sized, and/or the first sealing bulge loop and the second sealing bulge loop are sized, so that the axial force direction of the rotating shaft is directed from the first impeller to the second impeller when the first impeller and the second impeller are simultaneously in a compression state.

In some embodiments, the protruding height a2 of the first sealing convex ring is 5 mm-7 mm, and the protruding height b2 of the second sealing convex ring is 8 mm-10 mm.

In some embodiments, the first sealing collar has a projection height a2 of 6mm and the second sealing collar has a projection height b2 of 9 mm.

In some embodiments, when the shaft section of the first sealing convex ring is in a convex shape, the first sealing convex ring comprises a first small-diameter ring segment close to one side of the first end plate and a first large-diameter ring segment clamped between the first small-diameter ring segment and the hub of the first impeller, the protruding height of the first large-diameter ring segment is a1, and a1/a2 is 0.58-0.62; or when the shaft section of the second sealing convex ring is convex, the second sealing convex ring comprises a second small-diameter ring segment close to one side of the second end plate and a second large-diameter ring segment clamped between the second small-diameter ring segment and the hub of the second impeller, the protruding height of the second large-diameter ring segment is b1, and the b1/b2 is 0.58-0.62.

In some embodiments, a1/a2 ═ b1/b2 ═ 0.6; and/or the diameter ratio d1/d2 of the first sealing convex ring to the second sealing convex ring is 1.17-1.22.

In some embodiments, d1/d2 is 1.18.

In some embodiments, the outlet diameter D1 of the first impeller is greater than the outlet diameter D2 of the second impeller.

In some embodiments, D1/D2 is 1.08-1.13; and/or the hub ratio l1/D1 of the first impeller is 0.22-0.25, and the hub ratio l2/D2 of the second impeller is 0.23-0.25; and/or the wheel diameter ratio c1/D1 of the first impeller is 0.58-0.62, and the wheel diameter ratio c2/D2 of the second impeller is 0.55-0.59.

In some embodiments, D1/D2 is 1.09; and/or, l1/D1 ═ 0.23; and/or, l2/D2 ═ 0.24; and/or, c1/D1 ═ 0.61; and/or, c2/D2 is 0.56.

The utility model provides a pair of air compressor constructs in first sealed bulge loop on the first terminal plate with construct in both form the cartridge and hold back formation labyrinth seal structure on the first impeller, do not increase can have bigger sealed length in the axial length of pivot to effectively reduce gaseous interstage and reveal, improved the air compressor performance.

Drawings

Fig. 1 is a schematic view of an internal structure of an air compressor according to an embodiment of the present invention (omitting components such as volute bodies corresponding to a first impeller and a second impeller, and corresponding connecting pipes);

FIG. 2 is a schematic view of the labyrinth seal structure formed between the raised sealing ring and the annular sealing ring in FIG. 1, illustrating the attenuation of the air flow;

FIG. 3 is a schematic axial cross-sectional view of the first impeller of FIG. 1 with some structural dimensions indicated;

FIG. 4 is a partial structural view of the first sealing collar of FIG. 1 with some structural dimensions indicated;

FIG. 5 is a schematic axial cross-sectional view of the second impeller of FIG. 1 with some structural dimensions indicated;

fig. 6 is a partial structural view of the second sealing convex ring marked with partial structural dimensions in fig. 1.

The reference numerals are represented as:

1. a housing; 11. a first end plate; 111. a first seal ring groove; 112. a first seal tooth; 114. a first outer ring plate; 115. a first inner ring plate; 12. a second end plate; 121. a second seal ring groove; 122. a second seal tooth; 124. a second outer ring plate; 125. a second inner ring plate; 21. a rotating shaft; 22. a first impeller; 221. A first sealing convex ring; 23. a second impeller; 231. a second sealing convex ring; 100. a motor stator; 101. A thrust plate; 102. a gas axial bearing; 103. and locking the nut.

Detailed Description

Referring to fig. 1 to 6 in combination, the present invention provides an air compressor, especially an ultra-high speed oil-free two-stage air compressor for a gas suspension fuel cell engine, comprising a casing 1 and a rotor assembly, the motor stator and the rotor component are assembled in the machine shell 1, one axial end of the machine shell 1 is provided with a first end plate 11, the rotor assembly comprises a rotating shaft 21, one end of the rotating shaft 21 is connected with a first impeller 22 (specifically, a semi-open impeller), the side of the hub of the first impeller 22 facing the first end plate 11 (which can be understood as the back side of the hub) is provided with a first sealing convex ring 221, the side of the first end plate 11 facing the first impeller 22 has a first sealing ring groove 111, the first sealing convex ring 221 is located in the first sealing ring groove 111, and a labyrinth structure can be formed between the first sealing convex ring 221 and the first sealing ring groove 111. In this technical solution, the first sealing ring groove 111 configured on the first end plate 11 and the first sealing convex ring 221 configured on the first impeller 22 are inserted and accommodated to form a labyrinth structure, so that the axial length of the rotating shaft 21 is not increased, and the sealing length can be longer, thereby effectively reducing interstage leakage of gas and improving the performance of the air compressor.

In some embodiments, the groove wall of the first seal ring groove 111 has a first seal comb structure 112, that is, it is preferable to configure the first seal comb structure 112 on the first end plate 11, so that the first seal comb structure 112 can be replaced when worn, and a corresponding impeller does not need to be replaced, thereby effectively reducing the maintenance cost of the air compressor.

In some embodiments, in the axial cross section of the first impeller 22 (i.e., the cross section passing through the central axis of the first impeller 22), the first sealing protrusion ring 221 is in a shape of a protrusion protruding toward the first sealing ring groove 111 side, and in the axial cross section of the first end plate 11, the first sealing comb-tooth structure 112 is in a shape of a protrusion protruding away from the first impeller 22 side, so that the labyrinth seal structure is formed in a stepped structure along the axial direction of the rotating shaft 21, which can reduce the straight-through effect and the air-permeable loss, and the sealing effect with the same sealing length is better, and tests prove that the interstage air leakage amount of the labyrinth seal structure adopting the structure is reduced by about 25% compared with that of a smooth labyrinth seal structure, thereby further improving the air compressor performance. Referring to fig. 2, when the gas flows through the labyrinth structure with the step structure, the gas is throttled, the pressure and temperature of the gas flow decrease and the flow rate increases, the volume of the gas in the cavity increases, the speed decreases and forms a vortex, the temperature of the gas in the cavity returns to the point before throttling, and the pressure is not recovered; every time gas passes through the gap and the cavity, the airflow is subjected to the functions of throttling and capacity expansion once, the flow rate and the pressure drop of the gas are increased along with the increase of the number of the gas flowing through the gap and the cavity, and the gas does not continuously flow out when the pressure is reduced to an atmospheric pressure value, so that the sealing of the gas is realized.

In some embodiments, the casing 1 further has a second end plate 12 opposite to the first end plate 11, the other end of the rotating shaft 21 is further connected with a second impeller 23 (specifically, a semi-open impeller), one side of the hub of the second impeller 23 facing the second end plate 12 is provided with a second sealing convex ring 231, one side of the second end plate 12 facing the second impeller 23 is provided with a second sealing ring groove 121, the second sealing convex ring 231 is located in the second sealing ring groove 121, and a labyrinth structure can be formed between the second sealing convex ring 231 and the second sealing ring groove 121. That is, the first impeller 22 and the second impeller 23 are oppositely disposed at two ends of the rotating shaft 21, and correspondingly, the first impeller 22 is a first-stage impeller, and the second impeller 23 is a second-stage impeller, so that the axial force of the two-stage air compressor can be obviously reduced, the axial movement of the rotor assembly can be prevented, the design difficulty of the gas axial bearing can be reduced, and the stability of the axial bearing can be improved. The groove wall of the second seal ring groove 121 may also have a second seal comb-tooth structure 122 thereon to improve the gas tightness of the second impeller 23, and the second seal protrusion ring 231 is formed in a shape of a protruding projection toward the second seal ring groove 121 side on the axial cross section of the second impeller 23, similar to the first seal comb-tooth structure 112, and the second seal comb-tooth structure 122 is formed in a shape of a protruding projection away from the second impeller 23 side on the axial cross section of the second end plate 12.

In some embodiments, the first seal comb tooth structure 112 is composed of Na first seal teeth 112 spaced along the axial direction of the rotating shaft 21, 8 ≦ Na ≦ 11, preferably Na ≦ 10, and the second seal comb tooth structure 122 is composed of Nb second seal teeth 122 spaced along the axial direction of the rotating shaft 21, 11 ≦ Nb ≦ 14, preferably Nb ≦ 12, which is effective for reducing air leakage. The shape of the first seal tooth 112 and the second seal tooth 122 may be various, for example, any one of an asymmetric trapezoid, a symmetric trapezoid, a rectangle, and a triangle may be adopted, and an asymmetric trapezoid seal tooth is preferred. The ratio of the height to the pitch of the first seal teeth 112 or the second seal teeth 122 is 1.3-1.5, preferably 1.44, and air leakage can be further reduced.

In some embodiments, the first end plate 11 comprises a first outer ring plate 114 and a first inner ring plate 115 assembled together, the inner hole wall of the first outer ring plate 114 has a first radial outer sealing tooth corresponding to the first sealing comb-tooth structure 112, the outer circumferential wall of the first inner ring plate 115 has a first radial inner sealing tooth corresponding to the first sealing comb-tooth structure 112, and/or the second end plate 12 comprises a second outer ring plate 124 and a second inner ring plate 125 assembled together, the inner hole wall of the second outer ring plate 124 has a second radial outer sealing tooth corresponding to the second sealing comb-tooth structure 122, the outer circumferential wall of the second inner ring plate 125 has a second radial inner sealing tooth corresponding to the second sealing comb-tooth structure 122, and the assembly of the corresponding outer ring plate and inner ring plate to form the corresponding sealing comb-tooth structure can facilitate difficulty in manufacturing the first sealing tooth 112 and the second sealing comb-tooth 122 After the corresponding sealing teeth are manufactured respectively, the corresponding outer ring plate and the corresponding inner ring plate are assembled, for example, bolted through bolts, and the method is simple and convenient.

As described above, the first impeller 22 is a low-pressure stage impeller, the second impeller 23 is a high-pressure stage impeller, the size of the first impeller 22 and the size of the second impeller 23, and/or the size of the first seal convex ring 221 and the second seal convex ring 231 are configured to make the axial force direction of the rotating shaft 21 be directed from the first impeller 22 to the second impeller 23 when the first impeller 22 and the second impeller 23 are simultaneously in a compressed state. Through the design to the structural dimension of impeller and corresponding sealed bulge loop make the axial force that pivot 21 bore rationally move towards second impeller 23 one side to can effectively control the clearance increase trend between second impeller 23 and the corresponding spiral case inner wall, and then guarantee that the air leakage of high-pressure stage side is in lower level, guarantee air compressor's performance. It will be understood that the magnitude of the aforementioned axial force should be within the adjustable range of the gas axial bearing 102 on the rotating shaft 21, so as to enable the gas axial bearing 102 to normally perform the adjustment function of the axial displacement thereof.

Specifically, the protruding height a2 of the first sealing convex ring 221 is 5mm to 7mm, preferably, a2 is 6mm, and the protruding height b2 of the second sealing convex ring 231 is 8mm to 10mm, preferably, b2 is 9mm, so that the corresponding labyrinth sealing structure can be ensured to adapt to the sealing requirements of a low-pressure stage and a high-pressure stage, and the sealing effect is improved. When the shaft cross section of the first sealing convex ring 221 is a convex shape, the first sealing convex ring 221 includes a first small-diameter ring segment on a side close to the first end plate 11 and a first large-diameter ring segment sandwiched between the first small-diameter ring segment and the hub of the first impeller 22, the protruding height of the first large-diameter ring segment is a1, and a1/a2 is 0.58 to 0.62 (preferably a1/a2 is 0.6); or, when the shaft cross section of the second sealing convex ring 231 is a convex shape, the second sealing convex ring 231 includes a second small-diameter ring segment close to the second end plate 12 side and a second large-diameter ring segment sandwiched between the second small-diameter ring segment and the hub of the second impeller 23, the protruding height of the second large-diameter ring segment is b1, and b1/b2 is 0.58 to 0.62 (preferably, b1/b2 is 0.6). This structural design can ensure that the axial force of the rotating shaft 21 is directed toward the second impeller 23. Preferably, the diameter ratio d1/d2 of the first sealing convex ring 221 to the second sealing convex ring 231 is 1.17-1.22 (preferably, d1/d2 is 1.18), so that the axial force of the rotating shaft 21 can be ensured to be directed to the second vane 23 side.

As mentioned above, the axial force is related to the impeller outlet diameter, the impeller inlet diameter, the hub diameter, and the convex seal ring diameter, and therefore, these structural dimensions can change the axial force, specifically, the pressure difference ratio of the compression cavity corresponding to the first impeller 22 to the compression cavity corresponding to the second impeller 23 is 0.45:0.55, the outlet diameter D1 of the first impeller 22 is greater than the outlet diameter D2 of the second impeller 23 according to the method of distributing large impellers and small impellers according to small pressure difference, and in some embodiments, D1/D2 is 1.08 to 1.13 (preferably, D1/D2 is 1.09); the hub ratio l1/D1 of the first impeller 22 is 0.22-0.25 (preferably l1/D1 is 0.23), and the hub ratio l2/D2 of the second impeller 23 is 0.23-0.25 (preferably l2/D2 is 0.24); the wheel diameter ratio c1/D1 of the first impeller 22 is 0.58-0.62 (preferably c1/D1 is 0.61), and the wheel diameter ratio c2/D2 of the second impeller 23 is 0.55-0.59 (preferably c2/D2 is 0.56).

It is readily understood by a person skilled in the art that the advantageous ways described above can be freely combined, superimposed without conflict.

The above description is only exemplary of the present invention and should not be construed as limiting the present invention, and any modifications, equivalents and improvements made within the spirit and principles of the present invention are intended to be included within the scope of the present invention. The above is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims

1. The utility model provides an air compressor, its characterized in that, includes casing (1), rotor subassembly, casing (1) has first end plate (11), the rotor subassembly includes pivot (21), the one end of pivot (21) is connected with first impeller (22), the wheel hub of first impeller (22) is towards one side of first end plate (11) is equipped with first sealed bulge loop (221), first end plate (11) orientation one side of first impeller (22) has first sealed annular (111), first sealed bulge loop (221) are in first sealed annular (111), just first sealed bulge loop (221) with can form labyrinth seal structure between first sealed annular (111).

2. The air compressor as claimed in claim 1, wherein the groove wall of the first sealing ring groove (111) has a first sealing comb tooth structure thereon.

3. The air compressor according to claim 2, wherein the first seal protrusion ring (221) is formed in a protrusion shape protruding toward the first seal ring groove (111) side in an axial cross section of the first impeller (22), and the first seal comb tooth structure is formed in a protrusion shape protruding away from the first impeller (22) side in an axial cross section of the first end plate (11), and/or the first seal comb tooth structure is formed of Na number of first seal teeth (112) provided at intervals in an axial direction of the rotating shaft (21), and Na is 8 ≦ Na ≦ 11.

4. The air compressor according to claim 3, wherein the casing (1) further has a second end plate (12) opposite to the first end plate (11), the other end of the rotating shaft (21) is further connected with a second impeller (23), a second sealing convex ring (231) is arranged on one side of the hub of the second impeller (23) facing the second end plate (12), a second sealing ring groove (121) is arranged on one side of the second end plate (12) facing the second impeller (23), the second sealing convex ring (231) is arranged in the second sealing ring groove (121), and a labyrinth structure can be formed between the second sealing convex ring (231) and the second sealing ring groove (121).

5. The air compressor according to claim 4, characterized in that the groove wall of the second sealing ring groove (121) is provided with the second sealing comb tooth structure; and/or the first end plate (11) comprises a first outer ring plate (114) and a first inner ring plate (115) which are assembled and connected, the inner hole wall of the first outer ring plate (114) is provided with a first radial outer sealing tooth corresponding to the first sealing comb tooth structure, the outer circumferential wall of the first inner ring plate (115) is provided with a first radial inner sealing tooth corresponding to the first sealing comb tooth structure, and/or the second end plate (12) comprises a second outer ring plate (124) and a second inner ring plate (125) which are assembled and connected, the inner hole wall of the second outer ring plate (124) is provided with a second radial outer sealing tooth corresponding to the second sealing comb tooth structure, and the outer circumferential wall of the second inner ring plate (125) is provided with a second radial inner sealing tooth corresponding to the second sealing comb tooth structure.

6. The air compressor according to claim 5, wherein the second seal protrusion ring (231) is formed in a convex shape protruding toward the second seal ring groove (121) side in an axial cross section of the second impeller (23), the second seal comb tooth structure is formed in a convex shape protruding away from the second impeller (23) side in an axial cross section of the second end plate (12), and/or the second seal comb tooth structure is formed of Nb second seal teeth (122) provided at intervals in an axial direction of the rotating shaft (21), and Nb is 11 or more and 14 or less.

7. The air compressor of claim 6, wherein Na-10; alternatively, Nb ═ 12; or the ratio of the ruler height to the tooth pitch of the first sealing tooth (112) or the second sealing tooth (122) is 1.3-1.5.

8. The air compressor of claim 7, wherein the first seal tooth (112) or the second seal tooth (122) has a ratio of gauge height to tooth pitch of 1.44.

9. The air compressor according to claim 4, wherein the first impeller (22) is a low-pressure stage impeller and the second impeller (23) is a high-pressure stage impeller, the first impeller (22) and the second impeller (23) have the same dimensions, and/or the first and second seal collars (221, 231) have the same dimensions that the axial force direction of the rotating shaft (21) is directed from the first impeller (22) to the second impeller (23) when the first and second impellers (22, 23) are simultaneously in a compressed state.

10. The air compressor as claimed in claim 9, wherein the first sealing protrusion ring (221) has a protrusion height a2 of 5mm to 7mm, and the second sealing protrusion ring (231) has a protrusion height b2 of 8mm to 10 mm.

11. The air compressor as claimed in claim 10, wherein the first sealing protrusion ring (221) has a protrusion height a2 of 6mm, and the second sealing protrusion ring (231) has a protrusion height b2 of 9 mm.

12. The air compressor as claimed in claim 10, wherein when the first sealing convex ring (221) has a convex shape in axial cross section, the first sealing convex ring (221) includes a first small-diameter ring segment on a side close to the first end plate (11) and a first large-diameter ring segment sandwiched between the first small-diameter ring segment and the hub of the first impeller (22), and the first large-diameter ring segment has a protrusion height of a1, a1/a2 of 0.58-0.62; or when the shaft section of the second sealing convex ring (231) is in a convex shape, the second sealing convex ring (231) comprises a second small-diameter ring segment close to one side of the second end plate (12) and a second large-diameter ring segment clamped between the second small-diameter ring segment and the hub of the second impeller (23), the protruding height of the second large-diameter ring segment is b1, and b1/b2 is 0.58-0.62.

13. The air compressor of claim 12, wherein a1/a2 ═ b1/b2 ═ 0.6; and/or the diameter ratio d1/d2 of the first sealing convex ring (221) to the second sealing convex ring (231) is 1.17-1.22.

14. The air compressor of claim 13, wherein d1/d2 is 1.18.

15. The air compressor of claim 9, wherein the outlet diameter D1 of the first impeller (22) is greater than the outlet diameter D2 of the second impeller (23).

16. The air compressor as claimed in claim 15, wherein D1/D2 is 1.08-1.13; and/or the hub ratio l1/D1 of the first impeller (22) is 0.22-0.25, and the hub ratio l2/D2 of the second impeller (23) is 0.23-0.25; and/or the wheel diameter ratio c1/D1 of the first impeller (22) is 0.58-0.62, and the wheel diameter ratio c2/D2 of the second impeller (23) is 0.55-0.59.

17. The air compressor as claimed in claim 16, wherein D1/D2 is 1.09; and/or, l1/D1 ═ 0.23; and/or, l2/D2 ═ 0.24; and/or, c1/D1 ═ 0.61; and/or, c2/D2 is 0.56.