Patent Application
20240392792
The present disclosure relates to an electric turbo compressor.
A conventional electric turbo compressor is disclosed in the Japanese Patent Application Publication No. 2015-194151 (Patent Document 1), for example. The electric turbo compressor has a rotary shaft that is driven to rotate, and a first impeller and a second impeller that are mounted on the rotary shaft.
Patent Document 1: Japanese Patent Application Publication No. 2015-194151
The present disclosure proposes an electric turbo compressor that can perform efficient two-stage compression.
According to the conventional knowledge, an efficiency of a compressor is determined by the relationship between a height of a blade of an impeller at an outlet and a tip clearance, and if the height of the blade at the outlet is small, the efficiency deteriorates unless the tip clearance is also made small. As a result of an intensive study on improvement of the efficiency of a turbo compressor that performs two-stage compression, the present inventors have found that an effect of the tip clearance differs from the above-mentioned conventional knowledge, and have devised the following configuration.
In accordance with the present disclosure, an electric turbo compressor including a housing, an electric motor accommodated in the housing, a rotary shaft accommodated in the housing and driven to rotate by the electric motor, and a first impeller and a second impeller rotating together with the rotary shaft is proposed. The electric motor, the first impeller, the second impeller are arranged in this order in an axial direction of the rotary shaft. The first impeller includes a first hub fixed to the rotary shaft, and a plurality of first blades arranged in the first hub. The second impeller includes a second hub fixed to the rotary shaft, and a plurality of second blades arranged in the second hub. The first impeller moves gas from a leading end to a trailing end of each of the first blades with rotation. The second impeller moves the gas moved by the first impeller from a leading end to a trailing end of each of the second blades with rotation. A housing includes a first shroud facing the first blades and forming a first impeller chamber that accommodates the first impeller, and a second shroud facing the second blades and forming a second impeller chamber that accommodates the second impeller. A gap between the trailing end of each of the first blades and the first shroud is a first trailing end gap that has a shortest distance between each of the first blades and the first shroud, and a gap between the trailing end of each of the second blades and the second shroud is a second trailing end gap that has a shortest distance between each of the second blades and the first shroud, and the first trailing end gap is smaller than the second trailing end gap.
By setting the gaps in this manner, disturbance in the flow of refrigerant in the first impeller may be suppressed, which allows the electric turbo compressor to perform efficient two-stage compression. Furthermore, since contact between the second impeller and the housing may be suppressed, the reliability of the electric turbo compressor may be improved.
In the above-described electric turbo compressor, a height of the trailing end of each of the first blades toward the first trailing end gap is a first outlet height, and a height of the trailing end of each of the second blades toward the second trailing end gap is a second outlet height, and the first outlet height may be the higher than the second outlet height. Increasing the pressure of the refrigerant discharged from the first impeller by improving the compression efficiency of the first impeller allows the flow velocity of the refrigerant flowing into the second impeller to be reduced. As a result, an effect of making the first trailing end gap smaller than the second trailing end gap to achieve the efficient two-stage compression may be more reliably obtained.
In the above-described electric turbo compressor, an outer diameter of the first impeller may be greater than an outer diameter of the second impeller. Increasing the pressure of the refrigerant discharged from the first impeller by improving the compression efficiency of the first impeller allows the flow velocity of the refrigerant flowing into the second impeller to be reduced. As a result, an effect of making the first trailing end gap smaller than the second trailing end gap to achieve the efficient two-stage compression may be more reliably obtained.
In the above-described electric turbo compressor, a gap between the leading end of each of the first blades and the first shroud is a first leading end gap that has a shortest distance between each of the first blades and the first shroud, and a gap between the leading end of each of the second blades and the second shroud is a second leading end gap that has a shortest distance between each of the second blades and the second shroud, and the first leading end gap may be smaller than the second leading end gap. By setting the gaps in this manner, disturbance in the flow of refrigerant may be suppressed, which allows the electric turbo compressor to perform the efficient two-stage compression. Furthermore, since contact between the second impeller and the housing may be suppressed, the reliability may be improved.
The above-described electric turbo compressor may be configured to compress refrigerant circulating in a refrigeration cycle. As a result, efficient and reliable two-stage compression may be achieved by making the first trailing end gap smaller than the second trailing end gap.
Effect of Invention
According to the electric turbo compressor of the present disclosure, efficient two-stage compression may be performed.
Hereinafter, an embodiment will be described with reference to the drawings. In the following description, identical parts are designated with the same reference numerals and characters. Names and functions for these parts are the same. Therefore, the detailed descriptions thereof will not be repeated.
An electric turbo compressor of the embodiment is used, for example, for an air conditioner. Fluid to be compressed by the electric turbo compressor is refrigerant circulating in a refrigeration cycle.
As illustrated in
10 having a tubular shape. The housing 10 has a rear housing 11, a motor housing 12, a first compressor housing 13, a second compressor housing 14, a partition wall 15, a first intermediate housing 16, and a second intermediate housing 17. The rear housing 11, the motor housing 12, the first compressor housing 13, the second compressor housing 14, the partition wall 15, the first intermediate housing 16, and the second intermediate housing 17 are each made of metal material, for example, aluminum.
The motor housing 12 has a bottomed tubular shape, and includes an end wall 12a having a plate shape and a peripheral wall 12b extending in a tubular shape from an outer periphery of the end wall 12a. The second intermediate housing 17 is connected to the motor housing 12 with an opening of the peripheral wall 12b opposite from the end wall 12a closed by the second intermediate housing 17. A motor chamber 18 is defined by the end wall 12a, the peripheral wall 12b of the motor housing 12, and the second intermediate housing 17. The motor housing 12 has an inlet hole (not illustrated) through which refrigerant is introduced. The inlet hole is in communication with the motor chamber 18. Thus, refrigerant is introduced into the motor chamber 18 through the inlet hole.
A shaft insertion hole 17a having a circular hole shape is formed in a central portion of the second intermediate housing 17. The second intermediate housing 17 has a first bearing holder 19 having a cylindrical shape. The first bearing holder 19 is formed on an inner peripheral surface of the second intermediate housing 17. An inside of the first bearing holder 19 is in communication with the shaft insertion hole 17a. A central axis of the first bearing holder 19 and a central axis of the shaft insertion hole 17a coincide with each other. A first radial bearing 20 is held by the first bearing holder 19.
The end wall 12a of the motor housing 12 has a second bearing holder 21 having a cylindrical shape. The second bearing holder 21 is formed in a central portion of the end wall 12a of the motor housing 12. The central axis of the first bearing holder 19 coincides with a central axis of the second bearing holder 21. A second radial bearing 22 is held by the second bearing holder 21. The first radial bearing 20 and the second radial bearing 22 are disposed in the housing 10.
A first chamber forming recess 17b is formed in an outer surface of the second intermediate housing 17 opposite from the motor chamber 18. The first chamber forming recess 17b is in communication with the shaft insertion hole 17a. The second intermediate housing 17 has a plurality of communication holes 23. The communication holes 23 are positioned in a portion of the second intermediate housing 17 close to an outer periphery thereof. The communication holes 23 extend through the second intermediate housing 17. The communication holes 23 provide communication between the motor chamber 18 and the first chamber forming recess 17b.
The first intermediate housing 16 is connected to the second intermediate housing 17. The first intermediate housing 16 is connected to the second intermediate housing 17 so that an opening of the first chamber forming recess 17b is closed by the first intermediate housing 16. A thrust bearing accommodation chamber 25 is defined by the first intermediate housing 16 and the first chamber forming recess 17b of the second intermediate housing 17. A shaft insertion hole 16a having a circular hole shape is formed in a central portion of the first intermediate housing 16.
The first intermediate housing 16 has a plurality of communication holes 16b. The communication holes 16b are positioned in a portion of the first intermediate housing 16 close to an outer periphery thereof. The communication holes 16b extend through the first intermediate housing 16. A second chamber forming recess 16c is formed in an outer surface of the first intermediate housing 16 opposite from the thrust bearing accommodation chamber 25. The second chamber forming recess 16c is in communication with the shaft insertion hole 16a. The communication holes 16b provide communication between the thrust bearing accommodation chamber 25 and the second chamber forming recess 16c.
The first compressor housing 13 has a tubular shape and has a first inlet 24 having a circular hole shape. The first compressor housing 13 is connected to the first intermediate housing 16 in a state in which a central axis of the first inlet 24 coincide with a central axis of the shaft insertion hole 16a. The first inlet 24 is in communication with the second chamber forming recess 16c.
The partition wall 15 is connected to an end surface of the first compressor housing 13 opposite from the first intermediate housing 16. The partition wall 15 has a plate shape. A through hole 27 (
The second compressor housing 14 is connected to an end surface of the partition wall 15 opposite from the first compressor housing 13. An intermediate pressure chamber 31 is formed across the first compressor housing 13, the partition wall 15, and the second compressor housing 14. The intermediate pressure chamber 31 is in communication with the first discharge chamber 29 through a passage (not illustrated). The second compressor housing 14 has a second inlet 32 having a circular hole shape and in communication with the intermediate pressure chamber 31. The first discharge chamber 29 and the second inlet 32 are in communication with each other through the intermediate pressure chamber 31.
A second impeller chamber 33 in communication with the second inlet 32, a second discharge chamber 34 extending around the central axis of the second inlet 32 around the second impeller chamber 33, and a second diffuser passage 35 providing communication between the second impeller chamber 33 and the second discharge chamber 34 are formed between the partition wall 15 and the second compressor housing 14.
The housing 10 has the first impeller chamber 28 and the second impeller chamber 33. The first impeller chamber 28 and the second impeller chamber 33 are partitioned by the partition wall 15.
The rear housing 11 is connected to the second compressor housing 14. The rear housing 11 defines the intermediate pressure chamber 31. The rear housing 11 has a plate shape.
The electric turbo compressor 1 includes a rotary shaft 40. The rotary shaft 40 extends from an inside of the second bearing holder 21 and passes through the motor chamber 18, an inside of the first bearing holder 19, the shaft insertion hole 17a, the thrust bearing accommodation chamber 25, the shaft insertion hole 16a, the first inlet 24, the first impeller chamber 28, the through hole 27, the second impeller chamber 33, and the second inlet 32 in this order in an axial direction of the housing 10. The rotary shaft 40 is disposed across the first impeller chamber 28 and the second impeller chamber 33 with the rotary shaft 40 inserted through the through hole 27.
The rotary shaft 40 has a first end 40a and a second end 40b on one end and the other end, respectively, of the rotary shaft 40. The first end 40a is positioned in the second compressor housing 14. The second end 40b is positioned in the end wall 12a of the motor housing 12. The rotary shaft 40 is accommodated in the housing 10.
The rotary shaft 40 has an axis L that coincides with the central axes of the first bearing holder 19, the second bearing holder 21, the shaft insertion hole 17a, the shaft insertion hole 16a, the first inlet 24, the through hole 27, and the second inlet 32. In the following description, the “axial direction of the rotary shaft 40,” which is a direction in which the axis L of the rotary shaft 40 extends, may be referred to as a “thrust direction” and a “radial direction of the rotary shaft 40” as a “radial direction.
The first radial bearing 20 and the second radial bearing 22 rotatably support the rotary shaft 40 in the radial direction. The first radial bearing 20 and the second radial bearing 22 each may be an aerodynamic bearing.
The electric turbo compressor 1 has a support plate 75 having a disk shape and formed on the rotary shaft 40. The support plate 75 protrudes radially outward from an outer peripheral surface of the rotary shaft 40. The support plate 75 rotates together with the rotary shaft 40. The support plate 75 is disposed in the thrust bearing accommodation chamber 25.
Thrust bearings 80 are disposed between the first intermediate housing 16 and the support plate 75, and between the second intermediate housing 17 and the support plate 75, respectively. Both of the thrust bearings 80 rotatably support the rotary shaft 40 in the thrust direction. The thrust bearings 80 each may be an aerodynamic bearing.
The electric turbo compressor 1 includes an electric motor 41. The electric motor 41 is accommodated in the motor chamber 18. The electric motor 41 is accommodated in the housing 10. The electric motor 41 is an example of a drive power source that drives the rotary shaft 40 to rotate. The electric motor 41 includes a stator 42 and a rotor 43.
The stator 42 includes a stator core 44 having a cylindrical shape, and a coil 45 wound around the stator core 44. The stator core 44 is fixed to the inner peripheral surface of the peripheral wall 12b of the motor housing 12.
The rotor 43 is positioned inside the stator core 44 in the radial direction in the motor chamber 18. The rotor 43 rotates together with the rotary shaft 40.
The rotor 43 includes a rotor core 43a fixed to the rotary shaft 40, and a plurality of permanent magnets (not illustrated) disposed in the rotor core 43a. Electric power controlled by an inverter device (not illustrated) is supplied to the coil 45, which rotates the rotor 43 of the electric motor 41. The rotary shaft 40 rotates together with the rotor 43.
The electric turbo compressor 1 includes a first impeller 51 and a second impeller 52. The first impeller 51 and the second impeller 52 are made of aluminum, for example. The first impeller 51 and the second impeller 52 are connected to the rotary shaft 40. The first impeller 51 and the second impeller 52 rotate together with the rotary shaft 40.
The second impeller 52 is disposed closer to the first end 40a of the rotary shaft 40 than the first impeller 51 is. The first impeller 51 and the second impeller 52 are disposed closer to the first end 40a of the rotary shaft 40 than the first radial bearing 20 is. The first impeller 51 is disposed closer to the electric motor 41 than the second impeller 52 is. The electric motor 41, the first impeller 51, and the second impeller 52 are arranged in this order in the axial direction of the rotary shaft 40. As illustrated in
The first impeller 51 includes a first hub 51H. The first hub 51H is fixed to the rotary shaft 40. The first hub 51H has a trailing end surface 51a, a leading end surface 51b, an outer peripheral surface 51c, and a radial outer edge portion 51d. The trailing end surface 51a, the leading end surface 51b, the outer peripheral surface 51c, and the radial outer edge portion 51d form part of an outer surface of the first hub 51H. The first hub 51H has a substantially truncated conical shape, the outer diameter of which increases from the leading end surface 51b positioned on the first inlet 24 side toward the trailing end surface 51a.
The trailing end surface 51a forms a rear end of the first hub 51H. The trailing end surface 51a forms part of the outer surface of the first hub 51H that does not form a refrigerant flow passage. In a state in which the first impeller 51 is connected to the rotary shaft 40 and the electric turbo compressor 1 is assembled, the trailing end surface 51a faces the partition wall 15 in the axial direction of the rotary shaft 40. The partition wall 15 has a first facing surface 15a that faces the trailing end surface 51a of the first hub 51H in the axial direction of the rotary shaft 40.
The leading end surface 51b forms a front end of the first hub 51H. The leading end surface 51b forms one end of the first impeller 51 in the axial direction of the rotary shaft 40. The leading end surface 51b corresponds to an end of the first hub 51H on a side on which refrigerant flows into the first impeller 51.
The outer peripheral surface (hub surface) 51c forms part of an inner wall surface of the first impeller chamber 28. The outer peripheral surface 51c is a curved surface concaved toward the axis L of the rotary shaft 40. At least a portion of the outer peripheral surface 51c faces outward in the radial direction of the rotary shaft 40. The outer peripheral surface 51c is formed so that the diameter of the outer peripheral surface 51c gradually increases from the leading end surface 51b to the trailing end surface 51a along the axial direction of the rotary shaft 40. The outer peripheral surface 51c is gradually inclined outward in the radial direction from the leading end surface 51b to the trailing end surface 51a.
The radial outer edge portion 51d is a portion of the first impeller 51 having the largest outer diameter. The radial outer edge portion 51d has a cylindrical shape with a short axis. The first impeller 51 has an outer diameter R1. The outer diameter R1 of the first impeller 51 is a distance between the axis L of the rotary shaft 40 and the radial outer edge portion 51d of the first impeller 51 in the radial direction of the rotary shaft 40.
The first impeller 51 has a plurality of first blades 51B. The plurality of
first blades 51B are provided on the outer peripheral surface 51c of the first hub 51H. The plurality of first blades 51B are arranged in a circumferential direction of the first hub 51H. The plurality of first blades 51B divide the first impeller chamber 28 in the circumferential direction to form refrigerant flow passages between pairs of the first blades 51B disposed side by side in the circumferential direction. The first blades 51B project radially outward from the outer peripheral surface 51c of the first hub 51H. The plurality of first blades 51B are arranged at equal intervals in the circumferential direction on the outer peripheral surface 51c of the first hub 51H. The distance between the first blades 51B disposed side by side in the circumferential direction of the first hub 51H increases from the front end to the rear end of the first hub 51H.
The first blades 51B each have a trailing end 51Ba, a leading end 51Bb, and an edge surface 51Bc. The trailing end 51Ba, the leading end 51Bb, and the edge surface 51Bc form part of the edge portion of each of the first blades 51B. The leading end 51Bb of each of the first blades 51B faces the first inlet 24. The trailing end 51Ba of each of the first blades 51B faces the first diffuser passage 30. The edge surface 51Bc of each of the first blades 51B faces the first compressor housing 13. The leading end 51Bb extends in the radial direction of the rotary shaft 40. The trailing end 51Ba extends in the axial direction of the rotary shaft 40.
The edge surface 51Bc is curved. The edge surface 51Bc is formed so that the diameter of the edge surface 51Bc gradually increases from the leading end 51Bb to the trailing end 51Ba along the axial direction of the rotary shaft 40. The edge surface 51Bc is gradually inclined outward in the radial direction from the leading end 51Bb to the trailing end 51Ba. The curvature of the edge surface 51Bc of each of the first blades 51B is larger than the curvature of the outer peripheral surface 51c of the first hub 51H.
The leading end 51Bb is an edge portion of each of the first blades 51B on an upstream side in a refrigerant flow direction. Refrigerant from the first inlet 24 flows into spaces between the pairs of the first blades 51B disposed side by side in the circumferential direction, via spaces between the leading ends 51Bb. The trailing end 51Ba is an edge portion of each of the first blades 51B on a downstream side in the refrigerant flow direction. The refrigerant flows radially outward via the spaces between pairs of the trailing ends 51Ba disposed side by side in the circumferential direction.
The second impeller 52 has a second hub 52H. The second hub 52H is fixed to the rotary shaft 40. The second hub 52H has a trailing end surface 52a, a leading end surface 52b, an outer peripheral surface 52c, and a radial outer edge portion 52d. The trailing end surface 52a, the leading end surface 52b, the outer peripheral surface 52c, and the radial outer edge portion 52d form part of an outer surface of the second hub 52H. The second hub 52H has a substantially conical shape, the outer diameter of which increases from the leading end surface 52b positioned on the second inlet 32 side toward the trailing end surface 52a.
The trailing end surface 52a forms a rear end of the second hub 52H. The trailing end surface 52a forms part of the outer surface of the second hub 52H that does not form the refrigerant flow passage. In a state in which the second impeller 52 is connected to the rotary shaft 40 and the electric turbo compressor 1 is assembled, the trailing end surface 52a faces the partition wall 15 in the axial direction of the rotary shaft 40. The partition wall 15 has a second facing surface 15b that faces the trailing end surface 52a of the second hub 52H in the axial direction of the rotary shaft 40.
The leading end surface 52b forms a front end of the second hub 52H. The leading end surface 52b forms one end of the second impeller 52 in the axial direction of the rotary shaft 40. The leading end surface 52b corresponds to an end of the second hub 52H on a side on which refrigerant flows into the second impeller 52.
The outer peripheral surface (hub surface) 52c forms part of an inner wall surface of the second impeller chamber 33. The outer peripheral surface 52c is a curved surface concaved toward the axis L of the rotary shaft 40. At least a portion of the outer peripheral surface 52c faces outward in the radial direction of the rotary shaft 40. The outer peripheral surface 52c is formed so that the diameter of the outer peripheral surface 52c gradually increases from the leading end surface 52b to the trailing end surface 52a along the axial direction of the rotary shaft 40. The outer peripheral surface 52c is gradually inclined outward in the radial direction from the leading end surface 52b toward the trailing end surface 52a.
The radial outer edge portion 52d is a portion of the second impeller 52 having the largest outer diameter. The radial outer edge portion 52d has a cylindrical shape with a short axis. The second impeller 52 has an outer diameter R2. The outer diameter R2 of the second impeller 52 corresponds to a distance between the axis L of the rotary shaft 40 and the radial outer edge portion 52d of the second impeller 52 in the radial direction of the rotary shaft 40. As illustrated in
The second impeller 52 has a plurality of second blades 52B. The plurality of second blades 52B are provided on the outer peripheral surface 52c of the second hub 52H. The plurality of second blades 52B are arranged in a circumferential direction of the second hub 52H. The plurality of second blades 52B divide the second impeller chamber 33 in the circumferential direction to form refrigerant flow passages between pairs of the second blades 52B disposed side by side in the circumferential direction. The second blades 52B project radially outward from the outer peripheral surface 52c of the second hub 52H. The plurality of second blades 52B are arranged at equal intervals in the circumferential direction in the outer peripheral surface 52c of the second hub 52H. A distance between the second blades 52B disposed side by side in the circumferential direction of the second hub 52H gradually increases from the front end to the rear end of the second hub 52H.
The second blades 52B each have a trailing end 52Ba, a leading end 52Bb, and an edge surface 52Bc. The trailing end 52Ba, the leading end 52Bb, and the edge surface 52Bc form part of an edge portion of each of the second blades 52B. The leading end 52Bb of each of the second blades 52B faces the second inlet 32. The trailing end 52Ba of each of the second blades 52B faces the second diffuser passage 35. The edge surface 52Bc of each of the second blades 52B faces the second compressor housing 14. The leading end 52Bb extends in the radial direction of the rotary shaft 40. The trailing end 52Ba extends in the axial direction of the rotary shaft 40.
The edge surface 52Bc is curved. The edge surface 52Bc is formed so that the diameter of the edge surface 52Bc gradually increases from the leading end 52Bb to the trailing end 52Ba along the axial direction of the rotary shaft 40. The edge surface 52Bc is gradually inclined outward in the radial direction from the leading end 52Bb toward the trailing end 52Ba. The curvature of the edge surface 52Bc of each of the second blades 52B is larger than the curvature of the outer peripheral surface 52c of the second hub 52H.
The leading end 52Bb is an edge portion of each of the second blades 52B on an upstream side in a refrigerant flow direction. Refrigerant from the second inlet 32 flows into spaces between the pairs of the second blades 52B disposed side by side in the circumferential direction, via spaces between the leading ends 52Bb. The trailing end 52Ba is an edge portion of each of the second blades 52B on a downstream side in the refrigerant flow direction. The refrigerant flows radially outward through spaces between pairs of the trailing ends 52Ba disposed side by side in the circumferential direction.
The electric motor 41 drives a rotating body including the rotary shaft 40, the first impeller 51, and the second impeller 52 to rotate, so that the rotating body rotates integrally around the axis L. The first impeller 51 rotates together with the rotary shaft 40 to move gaseous refrigerant from the leading ends 51Bb to the trailing ends 51Ba of the first blades 51B and compress the refrigerant. The second impeller 52 rotates together with the rotary shaft 40 to move the gaseous refrigerant moved and compressed by the first impeller 51 from the leading end 52Bb to the trailing end 52Ba of the second blades 52B and t compress the refrigerant. The first impeller 51 is disposed upstream, and the second impeller 52 is disposed downstream in the refrigerant flow direction.
The first impeller 51 and the second impeller 52 are disposed on the rotary shaft 40 so that the trailing end surface 51a of the first hub 51H and the trailing end surface 52a of the second hub 52H face each other across the partition wall 15. A spacer 54 having a hollow cylindrical shape is disposed between the first impeller 51 and the second impeller 52. The spacer 54 has a first end facing the trailing end surface 51a of the first hub 51H and a second end facing the trailing end surface 52a of the second hub 52H. A dimension of the spacer 54 in the axial direction of the rotary shaft 40 is slightly greater than a distance between the first facing surface 15a and the second facing surface 15b of the partition wall 15. The spacer 54 functions to seal a gap between the outer peripheral surface of the rotary shaft 40 and the inner peripheral surface of the through hole 27.
The rotary shaft 40 has a fitting member 55 mounted to the outer peripheral surface of the rotary shaft 40 in the first end 40a. The fitting member 55 has a hollow tubular shape. The fitting member 55 is mounted to the rotary shaft 40 by way of screwing, for example. The fitting member 55 is in contact with the leading end surface 52b of the second hub 52H. The fitting member 55 supports the second impeller 52 in the axial direction of the rotary shaft 40.
The first compressor housing 13 has a first shroud 53a that cooperates with the partition wall 15 to define the first impeller chamber 28. The first shroud 53a has a truncated conical shape, which covers the first impeller 51 from an outer side in the radial direction. The first shroud 53a faces the outer peripheral surface 51c of the first hub 51H. The first shroud 53a extends along the outer peripheral surface 51c of the first hub 51H from the trailing end surface 51a to the leading end surface 51b of the first hub 51H. The first shroud 53a surrounds the plurality of first blades 51B. The first shroud 53a faces the edge surfaces 51Bc of the first blades 51B and forms part of the inner wall surface of the first impeller chamber 28. The pairs of the first blades 51B disposed side by side in the circumferential direction of the first hub 51H, the first hub 51H, and the first shroud 53A form refrigerant flow passages extending radially.
A first tip clearance 61 is formed between the first impeller 51 and the first shroud 53a. The first tip clearance 61 is a gap extending between the edge surfaces 51Bc of the first blades 51B and the first shroud 53a of the first compressor housing 13 from the leading ends 51Bb to the trailing ends 51Ba of the first blades 51B.
The second compressor housing 14 has a second shroud 53b that cooperates with the partition wall 15 to define the second impeller chamber 33. The second shroud 53b has a truncated conical shape, which covers the second impeller 52 from an outer side in the radial direction. The second shroud 53b faces the outer peripheral surface 52c of the second hub 52H. The second shroud 53b extends along the outer peripheral surface 52c of the second hub 52H from the trailing end surface 52a to the leading end surface 52b of the second hub 52H. The second shroud 53b surrounds the plurality of second blades 52B. The second shroud 53b faces the edge surfaces 52Bc of the second blades 52B and forms part of the inner wall surface of the second impeller chamber 33. The pairs of the second blades 52B disposed side by side in the circumferential direction of the second hub 52H, the second hub 52H, and the second shroud 53b form refrigerant flow passages extending radially.
A second tip clearance 62 is formed between the second impeller 52 and the second shroud 53b. The second tip clearance 62 is a gap extending between the edge surfaces 52Bc of the second blades 52B and the second shroud 53b of the second compressor housing 14 from the leading ends 52Bb to the trailing ends 52Ba of the second blades 52B.
As illustrated in
As illustrated in
In addition, as illustrated in
The first outlet height T1 is a height of the trailing end 51Ba of each of the first blades 51B toward the first trailing end gap 61b. The first outlet height T1 is the height of the trailing end 51Ba of each of the first blades 51B that protrudes from the outer peripheral surface 51c of the first hub 51H toward the first trailing end gap 61b, and refers to the largest protruding height in each of the first blades 51B. The second outlet height T2 is a height of the trailing end 52Ba of each of the second blades 52B toward the second trailing end gap 62b. The second outlet height T2 is the height of the trailing end 52Ba of each of the second blades 52B that protrudes from the outer peripheral surface 52c of the second hub 52H toward the second trailing end gap 62b, and refers to the largest protruding height in each of the second blades 52B.
In the electric turbo compressor 1, refrigerant is drawn into the motor chamber 18 through an inlet hole (not illustrated). The refrigerant drawn into the motor chamber 18 passes through the communication holes 23, the thrust bearing accommodation chamber 25, the communication holes 16b, and the inside of the second chamber forming recess 16c, and is drawn into the first inlet 24. The refrigerant drawn into the first inlet 24 is pressurized by the centrifugal action of the first impeller 51, and is fed from the first impeller chamber 28 into the first diffuser passage 30 in which the refrigerant is further pressurized. The refrigerant having passed through the first diffuser passage 30 is discharged to the first discharge chamber 29.
The refrigerant discharged to the first discharge chamber 29 passes through the intermediate pressure chamber 31, and is drawn into the second inlet 32. The refrigerant drawn into the second inlet 32 is pressurized by the centrifugal action of the second impeller 52, and is fed from the second impeller chamber 33 into the second diffuser passage 35 in which the refrigerant is further pressurized. The refrigerant having passed through the second diffuser passage 35 is discharged to the second discharge chamber 34. The second discharge chamber 34 is in communication with a discharge port (not illustrated). The refrigerant compressed by the electric turbo compressor 1 is discharged from the discharge port to an outside of the electric turbo compressor 1.
As has been described, in the electric turbo compressor 1 of the embodiment, as illustrated in
The second impeller 52 compresses the refrigerant having been compressed by the first impeller 51. The pressure of the refrigerant flowing through the second impeller chamber 33 is higher than the pressure of the refrigerant flowing through the first impeller chamber 28. Since the density of the refrigerant flowing through the first impeller chamber 28 is lower than the density of the refrigerant flowing through the second impeller chamber 33, a volumetric flow rate needs to be higher in the first impeller 51. Thus, the flow velocity of the refrigerant flowing through the first impeller chamber 28 is higher than the flow velocity of the refrigerant flowing through the second impeller chamber 33. It is noted that the compression ratio of the refrigerant by the first impeller 51 is higher than that by the second impeller 52.
As the flow velocity of the refrigerant increases, an effect of the tip clearance becomes greater. In the first impeller 51 where the flow velocity of the refrigerant is high, the flow of the refrigerant is disturbed if the first tip clearance 61 is large. In the second impeller 52 where the flow velocity of the refrigerant is low, an effect on the performance is small even if the second tip clearance 62 is large. Disturbance in the flow of the refrigerant may be suppressed by making the tip clearance of the first impeller 51 small to set the first trailing end gap 61b smaller than the second trailing end gap 62b. Therefore, the electric turbo compressor 1 of the embodiment may perform efficient two-stage compression.
The second impeller 52 is disposed closer to the first end 40a of the rotary shaft 40 than the first impeller 51 is. The second impeller 52 disposed on the tip end side of the rotary shaft 40 may have greater runout than the first impeller 51 during operation. By setting the second trailing end gap 62b larger than the first trailing end gap 61b, contact between the second impeller 52 and the second compressor housing 14 may be suppressed. Therefore, the reliability of the electric turbo compressor 1 may be improved.
As illustrated in
Since both the first impeller 51 and the second impeller 52 rotate integrally with the rotating shaft 40, the rotation speeds of the first impeller 51 and the second impeller 52 are equal to each other. In this case, the compression efficiency of the first impeller 51 may be improved by making the first outlet height T1 larger than the second outlet height T2. By increasing the pressure of the refrigerant discharged from the first impeller 51, the flow velocity of the refrigerant flowing into the second impeller 52 may be reduced. Thus, the effect on performance may be reduced even if the second tip clearance 62 is increased. As a result, an effect of the configuration in which the first trailing end gap 61b is made smaller than the second trailing end gap 62b to achieve the efficient two-stage compression may be more reliably obtained.
As illustrated in
As illustrated in
Since fluid to be compressed by the electric turbo compressor 1 is a refrigerant that circulates in the refrigeration cycle, even if the second tip clearance 62 is increased, the effect on performance may be reduced. Thus, the efficient and reliable two-stage compression may be achieved by making the first trailing end gap 61b smaller than the second trailing end gap 62b.
In the description of the embodiment, an example of an arrangement in which the trailing end surface 51a of the first hub 51H of the first impeller 51 and the trailing end surface 52a of the second hub 52H of the second impeller 52 face each other with the partition wall 15 interposed therebetween has been described. The arrangement of the first impeller 51 and the second impeller 52 is not limited to this example.
Although the electric turbo compressor 1 described in the embodiment is a centrifugal compressor, the technical idea of the present disclosure is also applicable to a diagonal flow type compressor.
Although the description of the embodiment has been provided as above, the embodiment disclosed herein is an example in all respects, and should not be considered restrictive. The scope of the present invention shall be defined not by the description but by the claims, and is intended to include embodiments equivalent to the scope of the claims and all modifications within the scope.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-151033 | Sep 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/011619 | 3/15/2022 | WO |
