JP2022025926A - Centrifugal compressor - Google Patents

Abstract

To provide a centrifugal compressor with a further improved efficiency.SOLUTION: A centrifugal compressor includes a bell mouth having a tubular shape surrounding an axis, a shroud forming a clearance by surrounding an end portion at one side of the axial direction of the bell mouth from an outer peripheral side and extending from an upstream side toward a downstream side toward an outer side in a radial direction toward the one side in the axial direction, a main plate facing the one side of the axial direction of the shroud, and a plurality of main blades arranged at intervals in a circumferential direction. The main blades include a main blade body erected toward a shroud side from the main plate and a tip portion connecting to the other side of the axial direction of the main blade body and twisting so as to be along a tangent direction of a virtual circle centered at the axis.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to centrifugal compressors.

As an example of the air conditioner, a ceiling-embedded air conditioner as shown in Patent Document 1 below is widely used. The ceiling-embedded air conditioner includes a casing embedded in the indoor ceiling, a motor having an output shaft that rotates around an axis extending in the vertical direction, a turbofan, a main plate that fixes the turbofan to the output shaft, and a turbo. It mainly has a heat exchanger that surrounds the fan and a bell mouth. A turbofan has a cylindrical shroud that surrounds an axis and a plurality of main wings that are spaced circumferentially spaced on one side of the shroud. Further, on the inner peripheral side of the shroud, a bell mouth for guiding the air taken in the casing toward the turbofan is provided. A certain clearance is formed between the bell mouth and the shroud.

As the turbofan rotates, indoor air is taken into the casing from the central part of the casing. This air is pumped to the outer peripheral side by a turbofan and then passes through a heat exchanger to become cold or warm air and is supplied indoors. In other words, the turbofan functions as a part (impeller) of the centrifugal compressor.

Japanese Unexamined Patent Publication No. 2006-77631

Here, a part of the air flow from the turbofan toward the outer peripheral side flows into the inside of the shroud as a leak flow through the above-mentioned clearance. This leak flow contains a swirling component due to being pumped by a turbofan. Losses occur when such leaks merge with the mainstream inside the shroud. Specifically, the inflow angle with respect to the main wing changes by the amount of the swirling component of the leak flow, which may cause the flow to separate. As a result, the efficiency of the centrifugal compressor is reduced.

The present disclosure has been made to solve the above problems, and an object of the present disclosure is to provide a centrifugal compressor with further improved efficiency.

In order to solve the above problems, the centrifugal compressor according to the present disclosure forms a clearance by surrounding a tubular bell mouth that surrounds an axis and one end of the bell mouth in the axial direction from the outer peripheral side. Along with this, a shroud extending from the upstream side to the downstream side so as to go outward in the radial direction toward one side in the axial direction, a main plate facing the one side in the axial direction of the shroud, and a circumferential direction provided over the shroud and the main plate. The main wing is provided with a main wing in which a plurality of wing are arranged at intervals, and the main wing rises from the main plate toward the shroud side and has a two-dimensional wing shape having a uniform cross-sectional shape orthogonal to the axis. , A portion of the main wing body that is continuous with the other side in the axial direction and includes the front edge of the main wing, and the cross-sectional shape orthogonal to the axis is directed toward the other side in the axial direction. It has a tip portion that is twisted along the tangential direction of a virtual circle centered on.

According to the present disclosure, it is possible to provide a centrifugal compressor with further improved efficiency.

It is sectional drawing which shows the structure of the ceiling-embedded type air conditioner which concerns on embodiment of this disclosure. It is an enlarged view which shows the structure of the turbofan which concerns on embodiment of this disclosure. It is a figure which looked at the main wing of the turbofan which concerns on embodiment of this disclosure from the axial direction. It is an enlarged view which shows the modification of the turbofan which concerns on embodiment of this disclosure. It is an enlarged view of the main part which shows the modification of the ceiling-embedded type air conditioner which concerns on embodiment of this disclosure.

(Ceiling-embedded air conditioning configuration)
Hereinafter, the ceiling-embedded air conditioner 100 as a centrifugal compressor according to the embodiment of the present disclosure will be described with reference to FIGS. 1 to 4. As shown in FIG. 1, the ceiling-embedded air conditioner 100 includes a casing 1, a motor 2, a main plate 3, a turbofan 4, a heat exchanger 5, and a bell mouth 6.

The casing 1 is embedded in the ceiling wall C of the building. The casing 1 has a rectangular shape when viewed from below, and is recessed upward to form an internal space. Specifically, the casing 1 has a panel 1A exposed to the ceiling surface Ca and a box-shaped cabinet 1B provided above the panel 1A. The panel 1A has a panel main body 11 which is a rectangular frame body, and a grill 12 as a suction port 11A provided in the center of the lower part. The panel main body 11 forms an outlet 11B around the suction port 11A.

The motor 2 is provided in the central portion of the bottom surface 1S facing downward inside the cabinet 1B. The motor 2 has a motor main body 21 that houses a coil, a magnet, and the like, and an output shaft 22 that projects vertically downward from the motor main body 21. The output shaft 22 is rotationally driven around an axis line Ac extending in the vertical direction.

A main plate 3 extending radially outward from the output shaft 22 is fixed to the output shaft 22. The main plate 3 has a conical cross-sectional shape extending from the lower side to the upper side from the inner side to the outer side in the radial direction. A turbofan 4 is attached to a portion of the lower surface of the main plate 3 including the radial outer edge. The turbofan 4 has a plurality of main wings 41 arranged at intervals in the circumferential direction, and an annular shroud 42 that covers the main wings 41 from below. The detailed configuration of the turbofan 4 will be described later. The main plate 3 and the turbofan 4 rotate with the rotation of the output shaft 22, and the air sucked from the suction port 11A is sent outward in the radial direction.

An annular heat exchanger 5 surrounding the turbofan 4 is provided on the radial outer side of the turbofan 4. The heat exchanger 5 is part of a refrigerant circuit having a refrigeration cycle. The air (mainstream Fm) sent to the heat exchanger 5 by the turbofan 4 exchanges heat with the refrigerant when passing through the heat exchanger 5. As a result, the air flowing out to the outer peripheral side of the heat exchanger 5 becomes cold air or warm air. This air flows downward along the side surface of the cabinet 1B and is supplied into the room from the outlet 11B.

Below the turbofan 4, a bell mouth 6 fixed to the upper part of the panel body 11 is arranged. The bell mouth 6 is provided to guide the air introduced from the suction port 11A and send it to the turbofan 4. The bell mouth 6 has a conical shape by gradually reducing its diameter from the lower side to the upper side. The end of the bell mouth 6 on one side (upper side) in the Ac direction is surrounded by the above-mentioned shroud 42 from the outer peripheral side. As shown in FIG. 2, a clearance C extending in the radial direction is formed between the outer peripheral surface 6S of the bell mouth 6 and the shroud 42 (the inner peripheral surface 42S of the shroud described later).

(Turbofan configuration)
Next, the configuration of the turbofan 4 will be described in detail. As shown in FIG. 2, the shroud 42 is curved so as to be radially outward from the other side in the axis Ac direction to one side. In the following description, in the curved direction in which the shroud 42 extends, the inside in the radial direction is referred to as "upstream side", and the outside in the radial direction is referred to as "downstream side". Further, the direction connecting the upstream side and the downstream side along the curved surface formed by the shroud 42 is called the shroud direction Ds. Of both sides of the shroud 42 in the thickness direction, the surface facing the inner peripheral side is the shroud inner peripheral surface 42S.

On the inner peripheral surface 42S of the shroud, a plurality of main wings 41 arranged at intervals in the circumferential direction with respect to the axis Ac are provided. The main wing 41 extends from the lower surface of the main plate 3 over the inner peripheral surface of the shroud 42S. The main wing 41 has a main wing main body 41A which is a portion on the main plate 3 side and a tip portion 41B which is a portion on the shroud 42 side. The main wing body 41A rises from the main plate 3 toward the shroud 42 side. The cross-sectional shape of the main wing body 41A orthogonal to the axis Ac is a uniform two-dimensional wing shape. More specifically, the cross-sectional shape of the main wing body 41A is rectangular as an example.

The leading edge E1a (that is, the radial inner edge) of the main wing body 41A extends in the axial direction Ac. The leading edge E1b of the tip portion 41B extends from the inside to the outside in the radial direction from one side to the other side in the axis Ac direction. Further, the lower end of the leading edge E1b (the other side in the axis Ac direction) extends to the inner edge of the inner peripheral surface of the shroud 42S in the radial direction. The trailing edge E3 (that is, the radial outer edge) of the main wing body 41A extends in the axial direction Ac.

The tip portion 41B extends from the lower end of the main wing body 41A to the inner peripheral surface of the shroud 42S. That is, the tip portion 41B is connected to the main wing body 41A (is integrally formed). The upper edge of the tip portion 41B (the portion shown by the broken line in FIG. 3) extends in the radial direction with respect to the axis line Ac. The tip portion 41B is appropriately determined from a range of 10% or more and 20% or less of the height of the main wing body 41 in the axis Ac direction.

Further, as shown in FIG. 3, when the main wing 41 is viewed from the axis Ac direction, the tip portion 41B is twisted with respect to the main wing main body 41A. More specifically, the tip portion 41B is twisted along the tangential direction of the virtual circle Cv centered on the axis line Ac as compared with the main wing main body 41A. In other words, the tip portion 41B is twisted so that the blade angle with respect to the radial direction becomes larger than that of the main blade main body 41A toward the other side in the axis Ac direction. In other words, the tip portion 41B is twisted toward the front side in the rotation direction of the turbofan 4 as compared with the main wing main body 41A. The twist angle of the tip portion 41B with respect to the main wing body 41A is appropriately determined from a range of 5 ° or more and 10 ° or less.

(Action effect)
Next, the operation of the ceiling-embedded air conditioner 100 will be described. When operating the ceiling-embedded air conditioner 100, the motor 2 is first driven. By driving the motor 2, the output shaft 22, the main plate 3, and the turbofan 4 rotate around the axis Ac. As the turbofan 4 rotates, indoor air is taken in from the suction port 11A. This air is sent to the turbofan 4 via the bell mouth 6 and then pumped outward in the radial direction to form a mainstream Fm (see FIG. 1 or FIG. 2). The mainstream Fm flows along the lower surface of the main plate 3. That is, the mainstream Fm flows from the inside to the outside in the radial direction from the lower side to the upper side. Most of this mainstream Fm exchanges heat with the refrigerant by passing through the heat exchanger 5, becomes cold air or warm air, and is supplied to the room from the outlet 11B.

Here, a part of the mainstream Fm from the turbofan 4 toward the outer peripheral side flows into the inside of the shroud 42 as a leak flow Fl through the above-mentioned clearance C (see FIG. 2). This leak flow Fl contains a swirling component (swivel component around the axis Ac) due to being pumped by the turbofan 4. When such a leak flow Fl joins the mainstream Fm inside the shroud 42, a loss occurs. Specifically, the inflow angle with respect to the main wing 41 may change by the amount of the swirling component of the leak flow Fl, and the flow may be separated. As a result, the efficiency of the ceiling-embedded air conditioner 100 is reduced.

Therefore, in the present embodiment, the tip portion 41B is formed on the main wing 41. Since the tip portion 41B is provided, the leak flow Fl flowing from the clearance C is captured by the tip portion 41B. As a result, the leak flow Fl accelerates, and the flow velocity becomes the same as that of the mainstream Fm. Further, the tip portion 41B is twisted with respect to the main wing body 41A along the tangential direction of the virtual circle Cv centered on the axis line Ac. As a result, the positive incident (inflow angle) of the leak flow Fl with respect to the mainstream Fm is optimized. As a result, the possibility of flow separation can be reduced. When these events occur in combination, the viscous dissipation when the leak flow Fl joins the main flow is suppressed, and the loss as a centrifugal compressor can be further reduced.

Further, according to the above configuration, the leading edge E1b of the tip portion 41B extends to the radial inner edge of the shroud 42. As a result, the leak flow Fl flowing from the clearance C can be captured by the tip portion 41B at an early stage. As a result, the loss generated between the leak flow Fl and the mainstream Fm can be further suppressed.

Further, according to the above configuration, the tip portion 41B is 10% or more and 20% or less of the height of the main wing 41 in the axis Ac direction. As a result, the mainstream Fm can be smoothly formed by the main wing body 41A while sufficiently securing the size of the chip portion 41B. As a result, the ceiling-embedded air conditioner 100 can be operated more efficiently.

In addition, in the above configuration, the tip portion 41B is twisted with respect to the main wing main body 41A in a range of 5 ° or more and 10 ° or less. Thereby, the inflow angle of the leak flow Fl can be changed more appropriately.

The embodiments of the present disclosure have been described above. It is possible to make various changes and modifications to the above configuration as long as it does not deviate from the gist of the present disclosure.

For example, as shown in FIG. 4, the leading edge E1a of the main wing body 41 and the leading edge E1b of the tip portion 41B are configured to extend radially outward from one side in the axis Ac direction to the other side. You may. Here, the main plate 3 has an annular portion 31 extending in a plane orthogonal to the axis Ac, and a reduced diameter portion provided on the inner peripheral side of the annular portion 31 and decreasing in diameter from one side in the axis Ac direction to the other side. 32 and. In this modification, the upper end (one side in the axis Ac direction) of the leading edge E1a of the main wing body 41A is located on the lower surface of the reduced diameter portion 32. The lower end of the leading edge E1b of the tip portion 41B is located at the radial inner end edge of the inner peripheral surface 42S of the shroud, as in the above embodiment.

According to the above configuration, the leading edges E1a and E1b extend in a direction that largely intersects the flow direction of the mainstream Fm (direction orthogonal to the flow). Therefore, the timing at which the mainstream Fm collides with the leading edges E1a and E1b can be aligned over the entire area of the leading edges E1a and E1b. As a result, the possibility of flow separation on the surface of the main wing 41 can be further reduced.

Further, as shown in FIG. 5, it is also possible to arrange a fence 7 for blocking the leak flow on the outer peripheral side of the clearance C. The fence 7 has an annular shape centered on the axis line Ac. Further, in the example of the figure, a plurality of fences 7 having different diameters are arranged concentrically.

According to the above configuration, the clearance C is closed by the fence. As a result, the leakage flow itself through the clearance C can be reduced. As a result, the efficiency of the ceiling-embedded air conditioner 100 can be further improved.

<Additional Notes>
The ceiling-embedded air conditioner 100 (centrifugal compressor) described in each embodiment is grasped as follows, for example.

(1) The ceiling-embedded air conditioner 100 according to the first aspect has a tubular bell mouth 6 surrounding the axis Ac and an end portion of the bell mouth 6 on one side in the axis Ac direction from the outer peripheral side. A shroud 42 that forms a clearance C and extends from the upstream side to the downstream side so as to go outward in the radial direction toward one side in the axis Ac direction, a main plate 3 facing the one side in the axis Ac direction of the shroud 42, and the above. The main wing 41 is provided over the shroud 42 and the main plate 3 and a plurality of the main wings 41 are arranged at intervals in the circumferential direction. The main wing 41 rises from the main plate 3 toward the shroud 42 side and the axis line Ac. A main wing main body 41A having a uniform cross-sectional shape orthogonal to the main wing main body 41A and a portion of the main wing main body 41A connected to the other side of the main wing main body 41A in the Ac direction and including the front edge of the main wing 41. It has a tip portion 41B that is twisted along the tangential direction of the virtual circle Cv centered on the axis Ac from the main wing main body 41A as the cross-sectional shape orthogonal to Ac is directed to the other side in the axis Ac direction.

According to the above configuration, since the tip portion 41B is provided, the leak flow flowing from the clearance C is captured by the tip portion 41B. As a result, the leak flow accelerates and the flow velocity becomes the same as that of the main flow. Further, the tip portion 41B is twisted with respect to the main wing body 41A along the tangential direction of the virtual circle Cv centered on the axis line Ac. This optimizes the positive incident (inflow angle) of the leak flow with respect to the mainstream. When these events occur in combination, viscous dissipation when the leak flow joins the main flow is suppressed, and the loss as a centrifugal compressor can be further reduced.

(2) In the ceiling-embedded air conditioner 100 according to the second aspect, the leading edge of the chip portion 41B extends to the radial inner end edge of the shroud 42.

According to the above configuration, the leading edge of the tip portion 41B extends to the radial inner edge of the shroud 42. As a result, the leak flow flowing from the clearance C can be captured by the tip portion 41B at an early stage. As a result, the loss between the leak flow and the mainstream can be further reduced.

(3) In the ceiling-embedded air conditioner 100 according to the third aspect, the tip portion 41B is 10% or more and 20% or less of the height of the main wing 41 in the axis Ac direction.

According to the above configuration, the mainstream can be smoothly formed by the main wing body 41A while sufficiently securing the size of the tip portion 41B. This makes it possible to operate the centrifugal compressor more efficiently.

(4) In the ceiling-embedded air conditioner 100 according to the fourth aspect, the tip portion 41B is twisted with respect to the main wing main body 41A in a range of 5 ° or more and 10 ° or less.

According to the above configuration, the inflow angle of the leak flow can be changed more appropriately.

(5) In the ceiling-embedded air conditioner 100 according to the fifth aspect, the leading edge of the main wing 41 extends radially outward from one side in the Ac direction to the other side.

According to the above configuration, the leading edge of the main wing 41 extends radially outward from one side in the Ac direction to the other side. That is, the leading edge extends in a direction that largely intersects the mainstream flow direction. Therefore, the timing at which the mainstream collides with the leading edge can be aligned over the entire leading edge. As a result, it is possible to reduce the possibility of flow separation occurring on the surface of the main wing 41.

(6) The ceiling-embedded air conditioner 100 according to the sixth aspect is arranged on the outer peripheral side of the clearance C, and further includes an annular fence 7 centered on the axis Ac.

According to the above configuration, the clearance C is closed by the fence 7. As a result, the leakage flow itself through the clearance C can be reduced. As a result, the efficiency of the centrifugal compressor can be further improved.

100 Ceiling-embedded air conditioning 1 Casing 1A Panel 1B Cabinet 1S Bottom 2 Motor 3 Main plate 4 Turbo fan 5 Heat exchanger 6 Bellmouth 6S Outer surface 7 Fence 11 Panel body 11A Suction port 11B Air outlet 12 Grill 21 Motor body 22 Output shaft 31 Circular part 32 Reduced diameter part 41 Main wing 41A Main wing body 41B Chip part 42 Shroud 42S Shroud inner peripheral surface Ac Axial line C Clearance Ds Shroud direction E1a, E1b Leading edge E3 Trailing edge Fl Leakage flow Fm Mainstream Cv Virtual circle

Claims (6)

A tubular bell mouth that surrounds the axis,
A clearance is formed by surrounding the end of the bell mouth on one side in the axial direction from the outer peripheral side, and a shroud extending from the upstream side to the downstream side so as to go radially outward toward one side in the axial direction.
A main plate facing one side in the axial direction of the shroud,
A main wing provided over the shroud and the main plate, and a plurality of wings are arranged at intervals in the circumferential direction.
Equipped with
The main wing
A main wing body that rises from the main plate toward the shroud side and has a uniform cross-sectional shape orthogonal to the axis, and a main wing body.
A portion of the main wing body that is continuous with the other side in the axial direction and includes the leading edge of the main wing, and the axis is more than the main wing body as the cross-sectional shape orthogonal to the axis is directed toward the other side in the axial direction. The tip part that is twisted along the tangential direction of the virtual circle at the center,
Centrifugal compressor. The centrifugal compressor according to claim 1, wherein the leading edge of the chip portion extends to the radially inner end edge of the shroud. The centrifugal compressor according to claim 1 or 2, wherein the tip portion is 10% or more and 20% or less of the height of the main wing in the axial direction. The centrifugal compressor according to any one of claims 1 to 3, wherein the tip portion is twisted with respect to the main wing body in a range of 5 ° or more and 10 ° or less. The centrifugal compressor according to any one of claims 1 to 4, wherein the leading edge of the main wing extends radially inward from one side in the axial direction toward the other side. The centrifugal compressor according to any one of claims 1 to 5, further comprising an annular fence centered on the axis, which is arranged on the inner peripheral side of the clearance.

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