JPH04209993A - Centrifugal compressor - Google Patents

Abstract

PURPOSE:To prevent high pressure fluid from flowing into a motor side by constituting an impeller which feeds a fluid under pressure sucked by rotation of the impeller from the front side in radial direction with two impellers formed integrally with each other with their back surfaces made in contact with each other. CONSTITUTION:In a centrifugal compressor in which an impeller 3 driven rotatably by a motor 2 is provided in a fluid passage 4 in a casing 1, the impeller 3 is composed of a first impeller 5 opposed to an inlet portion 4a of the fluid passage 4 and a second impeller 6 formed integrally at the back of the first impeller 5. Also, a rear side suction passage 7 for feeding fluid W to the second impeller 6 is provided in the casing 1. By this, the fluid W sucked from the inlet portion 4a of the fluid passage is fed under pressure in radial direction by the first impeller 5 and the fluid W sucked from a rear side suction passage 7 is fed under pressure in radial direction by the second impeller 6. Thus high pressure fluid on the outlet side of the impeller 3 is prevented from flowing into the motor 2 side.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a centrifugal compressor.

(Prior Art) Generally, a centrifugal compressor has a structure as shown in FIG.

That is, the centrifugal compressor is equipped with a naro motor 2' as a drive source disposed inside a cane blower 1', and an impeller-type fan 3' rotationally driven by the motor 2'. Rotational energy is applied to the fluid W' sucked in from the front side inlet 9' of 3' to increase the total pressure of the fluid, and the fluid is pumped in the centrifugal direction. A centrifugal compressor having such a configuration is disclosed in Japanese Unexamined Patent Publication No. 1-205585.

(Problems to be Solved by the Invention) In the case of a centrifugal compressor configured as described above, the inflow side of the fan wheel 3' and the motor 2' side are at low pressure, and the outflow side of the fan wheel 3' is at high pressure. Therefore, in order to prevent the high-pressure fluid on the outflow side from flowing into the motor 2' side, which is in a low-pressure atmosphere, it is necessary to maintain a high sealing performance at the bearing portion of the motor rotating shaft 2a'. However, in reality, the greater the difference between high and low pressures, the more difficult it is to ensure sole properties, and the high temperature and high pressure fluid on the outflow side will flow into the motor 2' side. As a result, the motor 2' is exposed to high temperature and high pressure fluid.
This will lead to a decrease in efficiency. In addition, the imbalance between the pressure applied from the inflow side to the outflow side (i.e., high pressure) and the pressure on the rear side of the fan wheel 3' (i.e., low pressure) that occurs at startup causes an axial thrust force to be generated. This causes loss of rotational energy.

The present invention has been made in view of the above points, and therefore prevents high-pressure fluid from flowing into the motor side by making it possible to suck in fluid only from the front side of the fan, but also from the back side. The purpose is to make it possible.

(Means for Solving the Problem) In the invention of claim 1, as a means for solving the above problem, as shown in the drawings, a motor 2 serving as a drive source is provided in the goo song 1 and a motor 2 is provided in the casing 1. The fan wheel 3 is disposed in the provided fluid passage '4 and is rotationally driven by the motor 2, and is configured to pump fluid W sucked in from the front side of the fan wheel 3 in a centrifugal direction. In the centrifugal compressor, the fan wheel 3 is connected to the inflow section 4 & of the fluid passage 4.
It is composed of a first impeller 5 facing the first impeller 5, and a second impeller 6 installed integrally on the back side of the first impeller 5, and supplies fluid W to the second impeller 6 for use in the engine. A back side suction passage 7 is provided for this purpose.

In the invention according to claim 2, as a means for solving the above problem, as shown in the drawings, in the centrifugal compressor according to claim 1, the second impeller 6 is of a small flow rate and low specific speed type, and , the passage cross-sectional area of the back suction passage 7 is set smaller than that of the fluid passage inflow portion 4a.

In the invention according to claim 3, as a means for solving the above problem, as shown in the drawings, in the centrifugal compressor according to claim 1 or 2, the fluid passage inflow portion 4a and the back side suction passage 7 are are connected via a bypass passage 8.

(Function) In the invention of claim 1, the following effects can be obtained by the above means.

That is, when the fan wheel 3 is rotated by the rotational drive of the motor 2, the fluid W sucked from the fluid passage inflow part 4a flows into the first
The fluid W that is pumped in the centrifugal direction by the impeller 5 and sucked in from the back side suction passage 7 is pumped in the centrifugal direction by the second impeller 6.
High-pressure fluid is prevented from flowing into the motor 2 side, and a low-pressure fluid atmosphere exists on the motor 2 side.

In the invention of claim 2, the following effects can be obtained by the above means.

That is, due to the rotation of the second impeller 6, the back side suction passage 7
Although the amount of fluid sucked in from the motor 2 decreases, it is possible to prevent high-pressure fluid from flowing into the motor 2 side, and the motor 2 side becomes a low-pressure fluid atmosphere. In this case, the first impeller 5 takes on most of the work required for fluid pressure feeding by the fan wheel 3.

In the invention of claim 3, the following effects can be obtained by the above means.

That is, the first fluid W sucked in from the fluid passage inflow portion 4a located on the front side of the first impeller 5 is pumped in the centrifugal direction by the first impeller 5, and a part of it is
It is supplied to the second impeller 6 via the bypass passage 8 and the back side suction passage 7, and is forced to be fed in the centrifugal direction by the second impeller 6.

(Effects of the Invention) According to the invention of claim 1, a motor 2 serving as a driving source is provided in the caning I, and a motor 2 provided in the caning l is disposed in the fluid passage 4 and is rotationally driven by the motor 2. In the centrifugal compressor, the fan wheel 3 is connected to the inflow of the fluid passage 4 in a centrifugal compressor configured to pump fluid W sucked in from the front side of the fan wheel 3 in a centrifugal direction. Part 4a
A first impeller 5 facing the first impeller 5 and a second impeller 6 integrally provided on the back side of the first impeller 5, and for supplying fluid W to the second impeller 6 in the casing l. A rear side suction passage 7 is provided, and the fluid W sucked from the fluid passage inflow part 4a is
This is so that the fluid W that is pumped in the centrifugal direction by the first impeller 5 and sucked in from the back side suction passage 7 is pumped in the centrifugal direction by the second impeller 6, without the need for special sealing means. , the high-pressure fluid on the outflow side of the fan wheel 3 is prevented from flowing into the motor 2 side, and the motor 2
This makes it possible to create a low-pressure fluid atmosphere at a low temperature (that is, near the suction temperature) on the side, which provides an excellent f2 effect in that a decrease in motor efficiency can be prevented.

In addition, since the fluid is sucked in from the first and second innovators 5 and 6, which are in opposite directions, there is no pressure imbalance between the front side and the back side of the fan wheel 3, and rotational energy due to axial thrust is eliminated. This also has the effect of eliminating losses.

According to the invention of claim 2, in the centrifugal compressor of claim 1, the second impeller 6 is of a small flow rate and low specific velocity type, and the passage cross-sectional area of the back side suction passage 7 is set to the fluid passage inflow portion 4a. Since the setting is smaller than that of the first impeller 5, the first impeller 5 can take on most of the work required for the fluid pumping by the fan wheel 3, and the small amount of fluid pumped by the second impeller 6 can be used to carry out most of the work on the motor 2 side. This provides a sealing effect that prevents high-pressure fluid from flowing into the tank, which has the excellent effect of improving fluid pumping efficiency.

Since the second impeller 6 is of a small flow rate and low specific speed type, the shaft diameter of the rotating shaft 3a that supports the fan wheel 3 can be increased, which has the effect of greatly contributing to improving the support strength of the fan wheel 3. .

According to the third aspect of the present invention, in the centrifugal compressor according to the first or second aspect, the fluid passage inflow portion 4a and the back side suction passage 7 are connected via the bypass passage 8.
This has the effect that the fluid inflow path can be unified into one, and the device can be made more compact.

(Embodiments) Hereinafter, some preferred embodiments of the present invention will be described with reference to the accompanying drawings.

Embodiment 1 FIG. 1 shows a centrifugal compressor according to Embodiment 1 of the present invention. This embodiment corresponds to the first and third aspects of the invention.

The centrifugal compressor of this embodiment includes a motor 2 disposed in a casing 1 and serving as a drive source, and a fan 3 having a drive shaft 3a connected to a rotation shaft 2a of the motor 2. .

The fan wheel 3 is arranged at an intersection of a T-shaped fluid passage 4 formed in the casing 1. The fluid passage 4
consists of an inflow part 4a extending in the axial direction of the fan wheel 3 and an outflow part 4b extending in the centrifugal direction from the terminal end of the inflow part 4a.

The fan wheel 3 includes a first impeller 5 including a conical hub 5a facing toward the fluid passage inlet 4a and a number of blades 5b protruding from the conical surface of the conical hub 5a. The second impeller 6 includes a conical hub 6a provided on the back side of the first impeller 5, and a number of blades 6b protruding from the conical surface of the conical hub 6a. In the case of this example, both impellers are 5.6
The plates 5b and 6b have the same shape.

Note that the conical hub 6a of the second impeller 6 and the drive shaft 3a
are considered to be one and the same.

The casing 1 includes the second impeller 6.
A rear side suction passage 7 is formed to supply fluid to the rear side suction passage 7, and a bypass passage 8 branched from the inlet portion 4a of the fluid passage 4 is connected to the rear side suction passage 7. The cross-sectional area of the back suction passage 7 is smaller than that of the fluid passage inflow portion 4a.

In the drawings, reference numeral 9 denotes an inlet that serves as an inlet of the inlet portion 4a in the fluid passage 4, 10 an outlet that serves as an outlet of the outlet portion 4b in the fluid passage 4, 11 the stator of the motor 2, and 12 the motor. 2 is a rotor, and 13 is a bearing.

The centrifugal compressor configured as described above operates as follows.

When the fan wheel 3 is rotationally driven by the drive of the motor 2, most of the fluid W supplied from the fluid passage inflow part 4a is forced into the centrifugal direction by the first impeller 5, and a part of the inflow fluid W is is supplied to the second impeller 6 via the bypass passage 8 and the back side suction passage 7, and is pumped in the centrifugal direction.

Therefore, even without special sealing means, the high-pressure fluid at the fan 3 outlet side is prevented from flowing into the motor 2 side, creating a low-pressure fluid atmosphere at a low temperature (that is, near the suction temperature) on the motor 2 side. This makes it possible to prevent a decrease in motor efficiency. Also, since the fluid is sucked from the first and second impellers 5.6 which are oriented in opposite directions, the fan wheel 3
There is no pressure imbalance between the front side and the back side of the
Loss of rotational energy due to axial thrust is also eliminated.

In the case of this embodiment, since the passage area of the back side suction passage 79 is made small, the amount of fluid pumped by the second impeller 6 is small. It is sufficient to have the effect of preventing the high-pressure fluid from flowing into the motor 2 side. Therefore, the fluid pressure required for the compressor is mainly performed by the first impeller 5.

Embodiment 2 FIG. 2 shows a centrifugal compressor according to Embodiment 2 of the present invention. This embodiment corresponds to the invention of claim 1.

In the case of this embodiment, the fluid passage inflow portion 4a and 1. It is independent from the back side suction passage 7. Therefore, the centrifugal compressor of this embodiment is suitable for use by being placed in a low-pressure dome, for example.

The other configurations and effects are the same as those of the first embodiment, so their explanations will be omitted.

In the case of this embodiment, the passage cross-sectional area of the back side suction passage 7 may be made equal to that of the fluid passage inflow portion 4a.

Embodiment 3 FIG. 3 shows a centrifugal compressor according to Embodiment 3 of the present invention. This embodiment corresponds to claims 1.2 and 3 of the invention.

In the case of this embodiment, a small flow rate, low specific speed type is used as the second impeller 6 in the first embodiment. That is, the blades 6b of the second impeller 6 are significantly smaller than the blades 5b of the first impeller 5, and the shaft diameter of the drive shaft 3a of the fan wheel 3 is correspondingly increased.

With this configuration, the amount of fluid pumped by the second impeller 6 is extremely small, and serves only to prevent high-pressure fluid from flowing from the outlet side of the fan wheel 3 to the back side of the fan wheel 3. becomes.

Therefore, the work of pumping the fluid by the fan wheel 3 is carried out by the first impeller 5. In addition, the drive shaft 3a of the fan wheel 3
Since the shaft diameter of the fan wheel 3 can be increased, the support strength of the fan wheel 3 can be greatly increased.

The other configurations and effects are the same as those in the first embodiment, so their explanations will be omitted.

Embodiment 4 FIG. 4 shows a centrifugal compressor according to Embodiment 4 of the present invention. This embodiment corresponds to the first and second aspects of the invention.

In the case of this embodiment, the fluid passage inflow portion 4a and the back side suction passage 7 are independent. Therefore, the centrifugal compressor of this embodiment is suitable for use by being placed in a low-pressure dome, for example.

The other configurations and effects are the same as those of the third embodiment, so their explanations will be omitted.

It goes without saying that the present invention is not limited to the configurations of the embodiments described above, and that the design can be changed as appropriate without departing from the gist of the invention.

[Brief explanation of the drawing]

1 to 4 are sectional views of centrifugal compressors according to embodiments 1 to 4 of the present invention, and FIG. 5 is a sectional view of a conventional centrifugal compressor. 1...Casing 2...Motor 3...Fan wheel 3a...Drive shaft 4...Fluid passage 4a...Inflow section 4b...Outflow Part 5...First impeller 6...Second impeller 7...Back side suction passage 8...Bypass passage W...Fluid Applicant Daikin Industries, Ltd. company

Claims (1)

[Claims] 1. A motor (2) serving as a driving source is provided within the casing (1).
and a fluid passageway (4) provided within the casing (1).
A fan wheel (3) disposed inside the fan wheel (3) and rotationally driven by the motor (2), and configured to pump fluid (W) sucked in from the front side of the fan wheel (3) in a centrifugal direction. In the centrifugal compressor, the fan wheel (3) is connected to a first impeller (5) facing the inflow portion (4a) of the fluid passageway (4).
) and a second impeller (6) integrally provided on the back side of the first impeller (5),
The casing (1) includes the second impeller (6).
A centrifugal compressor characterized by being provided with a back side suction passage (7) for supplying fluid (W) to. 2. The second impeller (6) is of a small flow rate and low specific velocity type, and the passage cross-sectional area of the back side suction passage (7) is set smaller than that of the fluid passage inlet (4a). The centrifugal compressor according to claim 1. 3. The fluid passage inflow part (4a) and the back side suction passage (7)
) are connected to each other via a bypass passage (8).