JPH08303381A - Centrifugal compressor - Google Patents

Abstract

PURPOSE: To provide a highly efficient centrifugal compressor which can reduce in outer diameter and improve in flow coefficient, by providing a multistage low-pressure stage impeller and a multistage high-pressure stage impeller positioned close each other by separated across a partition wall in the central part. CONSTITUTION: A low-pressure stage suction port 1 is provided in an area adjacent to a partition wall 8 in the central part in the axle direction of a casing, and the multistage low-pressure stage impeller 5 is arranged along the axle 6 toward one end of the low-pressure stage delivery port 2. And a high-pressure stage suction port 3 is provided close to the low-pressure stage suction port 1 in the central part by separated across the partition wall 8 therefrom and a multistage high-pressure impeller 7 is provided along the axle 6 toward the other end of the high-pressure stage delivery port 4. The low-pressure stage suction port 1 and the high-pressure stage suction port 3 are thus positioned close to each other in the central part of the thick axle 6 and the low-pressure stage delivery port 2 and the high-pressure stage delivery port 4 are positioned in the both ends of the axle 6 so that both high-pressure sides of the multistage low-pressure stage impeller 5 and the high-pressure stage impeller 7 can be arranged in the adjacent to the end of the small diameter and the outer diameter can be minimized.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to centrifugal compressors.

[0002]

2. Description of the Related Art Conventionally, the arrangement of impellers of a multi-stage centrifugal compressor is called a straight arrangement from the low pressure side of the low pressure stage suction port 1 to the high pressure side of the high pressure stage discharge port 4 as shown in FIG. They are arranged in order.

Further, in the case of a composite arrangement by means of intermediate cooling, etc., the same arrangement is performed in the same order, or as shown in FIG.

That is, in FIGS. 2 and 3, 1 is a low pressure stage suction port, 2 is a low pressure stage discharge port, 3 is a high pressure stage suction port, 4 is a high pressure stage discharge port, 5 is a low pressure stage impeller, and 6 is a shaft. , 7 is a high-pressure stage impeller, 8 is a partition wall, and 9 is a casing.

[0005]

The above conventional centrifugal compressor has the following problems to be solved.

That is, the efficiency of the impeller is known to be related to the flow coefficient as shown in FIG. 4. In the case of a multi-stage impeller, the impeller on the high pressure side has a smaller flow coefficient and the efficiency decreases. .

In order to increase the flow coefficient, it is preferable to reduce the outer diameter of the impeller on the high pressure side, but there is the drawback that the shaft diameter of the impeller is also reduced.

As a means for attaching the impeller and the shaft, a shrink fitting or key method is generally used.

By the way, a rotor of a compressor is usually designed to operate between a primary natural frequency and a secondary natural frequency. The natural frequency of the rotor is f = (1 / 2π) ・ √ (K / M) (1) where f: frequency, K: rigidity of shaft, M: mass of shaft, relationship with shaft diameter f ∝ D / L ² (2) However, D: shaft diameter, L: distance between bearings In the case of a composite compressor that uses an intercooler, etc. in a multi-stage impeller, a straight arrangement is used as before. In the case of the rear arrangement, there is a problem that the outer diameter of the impeller cannot be correspondingly reduced due to the lower limit of the shaft diameter (the lower limit of the rigidity), and the efficiency decrease on the high pressure side cannot be avoided.

That is, it is not enough for the axle to simply satisfy the strength and to transmit the torque, and the deflection (deflection) in the direction perpendicular to the axis due to vibration or the like is not suppressed to a very small range, for example, near the center and the side of the casing. Interference with the labyrinth seal, large amplitude vibrations and various other problems.

When a shaft (round bar) having a uniform cross section is supported at both ends and a load is appropriately distributed between both ends and a load is applied, the deflection near the center is the largest, as can be seen well in the case of iron bars for gymnastics. . Therefore, even in the case of an axle whose both ends are axially supported, if the cross section is uniform, the center of the axle is moved by its own weight including the impeller, etc., or by centrifugal force due to the imbalance of the minute mass around the axis that is unavoidable in manufacturing during rotation. Since the maximum bending that occurs is maximum, the axle is designed to be thicker near the center of the axle and gradually (exponentially) narrower toward both ends in order to keep the deflection within a certain limit while reducing the moving weight. To be done.

This deflection depends on the rigidity, which is represented by E · I (therefore K in the above equation (1) is synonymous with E · I). E is the Young's modulus of the material, and I is the moment of inertia of the cross section, so if the material used for the axle is determined, E
Is determined automatically, and the only factor that determines the deflection is I (assuming that the distance between shaft supports and the load are constant). In the case of a circular cross section, since I depends only on the diameter (the fourth power), it is essential to increase the diameter in order to increase the rigidity of the axle.

Therefore, conventionally, even if the efficiency is sacrificed as described above, the impeller on the high pressure side, which is relatively close to the center, must be increased in outer diameter in accordance with the axle diameter.

An object of the present invention is to provide a centrifugal compressor that solves the above problems.

[0015]

As a means for solving the above problems, the present invention is directed to a centrifugal compressor in which a casing covers a multi-stage impeller arranged along the axle, and a partition wall at the center of the casing in the axle direction is used. A multi-stage low-pressure stage impeller, which has a low-pressure stage suction port in the vicinity and is arranged in order toward the low-pressure stage discharge port at one end along the axle, and a high pressure that is adjacent to the central low-pressure stage suction port with a partition wall. A centrifugal compressor comprising: a multistage high-pressure stage impeller having a stage suction port and arranged in order from the other end toward the high-pressure stage discharge port along the axle. Is.

[0016]

Since the present invention is constructed as described above, it has the following actions.

That is, the low pressure stage suction port (low pressure side) is provided in the vicinity of the partition wall at the center of the casing in the axle direction, and the low pressure stage is arranged along the axle toward the low pressure stage discharge port (high pressure side) at one end. A high-pressure stage which has a stage impeller and a high-pressure stage suction port (low-pressure side) adjacent to the low-pressure stage suction port with a partition wall between them, and is arranged along the axle toward the high-pressure stage discharge port (high-pressure side) at the other end. Since it has a stage impeller, both the low-pressure stage and the high-pressure stage are on the low-pressure side of the suction port at the central portion where the diameter of the axle is large, the large outer shape of the impeller is allowed, and the high-pressure side of the discharge port is on the low-pressure stage. Since the high-pressure stage common shaft has one end and the other end, that is, both ends having a small diameter, the outer diameter of the impeller can be correspondingly reduced, and the flow coefficient can be increased to obtain a highly efficient centrifugal compressor.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. It should be noted that the reference numerals and names of the respective parts are the same in order to facilitate comparison with the conventional example, unless otherwise necessary.

FIG. 1 is a vertical cross-sectional view of a centrifugal compressor according to this embodiment, in which 1 is a low pressure stage suction port (low pressure) provided near a partition wall 8 at a central portion of a casing 9 in the direction of an axis (axle) 6. side),
Reference numeral 2 denotes a low pressure stage discharge port (high pressure side) provided on one side (right side in the figure) along the shaft 6, and 3 is adjacent to the low pressure stage suction port (low pressure side) 1 with a partition wall 8 interposed therebetween. The high-pressure stage suction port (low-pressure side) provided at 4 is the other end along the shaft 6 (left end in the figure)
High-pressure stage discharge port (high-pressure side), 5 are low-pressure stage suction port (low-pressure side) 1 to low-pressure stage discharge port (high-pressure side) 2.
Low-pressure stage impellers, which are arranged in order toward, horizontally fix the multi-stage low-pressure stage impellers 5 and multi-stage high-pressure stage impellers 7 horizontally and pivotally support both ends (left and right ends in the figure) of the casing 9. In order to maintain the required rigidity of the axle (axle) as described in the section "Problems to be solved by the invention", the vicinity of the center is formed thick and both ends are formed thin. 7 is a high pressure stage suction port (low pressure side)
The high-pressure stage impellers arranged in order from 3 to the high-pressure stage discharge port (high-pressure side) 4, 8 is a partition wall for partitioning the low-pressure stage impeller 5 and the high-pressure stage impeller 7 in the casing 9, and 9 is A casing that covers the low-pressure stage impellers 5 and the high-pressure stage impellers 7 arranged along the shaft 6 and supports the shaft 6 at both ends.

Next, the operation of the above configuration will be described.

The low-pressure stage suction port (low-pressure side) 1 and the high-pressure stage suction port (low-pressure side) 3 are both located adjacent to each other in the thick central portion of the shaft 6, and the low-pressure stage discharge port (high-pressure side) 2 and high-pressure stage Each of the discharge ports (high pressure side) 4 is located at both narrow ends of the shaft 6. Therefore, the high-pressure sides of the multi-stage low-pressure stage impeller 5 and the multi-stage high-pressure stage impeller 7 are arranged near the respective thin (small diameter) shaft ends of the shaft 6, and the outer diameter can be correspondingly reduced. Therefore, a highly efficient impeller having a large flow coefficient, that is, a highly efficient centrifugal compressor can be obtained.

[0022]

[Table 1]

Table 1 is a relative comparison table with the present example in which the specifications of the conventional example are each 100, and this table reduces the required power of the centrifugal compressor of the present example by 3% as compared with the conventional example. It can be seen that the efficiency as a centrifugal compressor is improved by about 3%.

At present, in such a compressor, 3%
The efficiency improvement of is a significant improvement.

As described above, according to the present embodiment, both the low pressure side and the high pressure side of the centrifugal compressor have the low pressure side at the central portion with a large shaft diameter and the high pressure side at each end with a small shaft diameter. Because of the arrangement, the outer diameter of the impeller on the high pressure side can be reduced in accordance with the small shaft diameter, and as a result, the efficiency of the centrifugal compressor is improved due to the increased flow coefficient.

The effects of the present invention can be utilized more efficiently in a high compression type centrifugal compressor. That is, the larger the molecular weight of the gas, the greater the effect. Further, in a composite compressor having an intercooler or the like having a multistage impeller,
There is an advantage that efficiency reduction on the high pressure side can be avoided and a compressor with excellent performance can be realized.

[0027]

The present invention has the following effects because it is configured as described above.

That is, according to the present invention, the impeller on the high pressure side is
Since both the low-pressure stage and the high-pressure stage are arranged in the vicinity of both ends with a small shaft diameter, the outer diameter can be made small, and a highly efficient centrifugal compressor can be obtained by improving the flow coefficient.

In other words, in the conventional impeller arrangement, even if an impeller having an efficient flow coefficient is arranged in the first stage on the low pressure side, it is necessary to secure a certain shaft diameter on the high pressure side, so that the outer diameter of the impeller is required. However, by adopting the present invention, the outer diameter of the impeller can be gradually decreased toward the high pressure side, and an impeller having a large flow coefficient can be used. Therefore, a more efficient compressor than before can be obtained.

The effect of the present invention is more remarkably exhibited in the high compression type centrifugal compressor, and the larger the molecular weight of the gas, the greater the effect.

Further, in the composite type compressor having the multi-stage impeller and using the intercooler or the like, it is possible to avoid a decrease in efficiency on the high pressure side and realize a compressor having excellent performance.

[Brief description of drawings]

FIG. 1 is a side sectional view of a centrifugal compressor according to an embodiment of the present invention,

FIG. 2 is a sectional view of a conventional straight array,

FIG. 3 is a cross-sectional view of a back surface array of a conventional example,

FIG. 4 is a diagram showing a relationship between a flow coefficient and efficiency.

[Explanation of symbols]

 1 Low pressure stage suction port 2 Low pressure stage discharge port 3 High pressure stage suction port 4 High pressure stage discharge port 5 Low pressure stage impeller 6 Shaft (axle) 7 High pressure stage impeller 8 Partition wall 9 Casing

Claims (1)

[Claims] 1. A centrifugal compressor in which a casing covers a multi-stage impeller arranged along an axle, and a low-pressure stage suction port is provided near a partition wall at a central portion of the casing in the axle direction. Low pressure stage impellers arranged in order toward the low pressure stage discharge port, and a high pressure stage suction port adjacent to the low pressure stage suction port in the central portion with a partition wall adjacent to each other. A centrifugal compressor, comprising: a multistage high-pressure stage impeller arranged in order toward a stage discharge port.