CN112983849B - A centrifugal compressor structure with automatic balance of axial force - Google Patents

Abstract

The invention belongs to the field of fluid machinery, and relates to a centrifugal compressor structure whose axial force can be automatically balanced. The primary impeller and the secondary impeller are respectively installed, and the primary impeller and the secondary impeller are respectively located in the primary volute and the secondary volute; a primary shaft seal is arranged between the motor housing and the primary volute, and the motor housing A secondary shaft seal is arranged between the body and the secondary volute. The invention controls the wheel back pressure of the first-stage impeller and the second-stage impeller by adjusting the intake pressure of the first-stage shaft seal and the second-stage shaft seal. The axial force generated by the front and rear pressure difference is balanced out, avoiding the wear and failure of the centrifugal compressor due to the unbalanced axial force, and improving the performance and service life of the compressor. At the same time, the wheel back can be used as a thrust plate, and the thrust bearing is eliminated, which improves the positioning accuracy of the impeller and the compactness of the whole machine.

Description

A centrifugal compressor structure with automatic balance of axial force

technical field

The invention belongs to the field of fluid machinery, and relates to a centrifugal compressor structure whose axial force can be automatically balanced.

Background technique

As a type of fluid machinery, centrifugal compressors are widely used in metallurgy, petrochemical, natural gas transportation, refrigeration and power industries, and play a vital role in promoting economic development.

The increase of the gas pressure in the centrifugal compressor is due to the fact that when the gas flows through the impeller, the high-speed rotation of the impeller does work on the gas to increase the pressure of the gas. At the same time, the gas obtains a high speed. When , the flow velocity of the gas gradually decreases, and the kinetic energy is converted into pressure, which can further increase the pressure.

Traditional centrifugal compressors run smoothly under design conditions, but there are often some shortcomings and deficiencies in non-design conditions. The bearing wear is serious, which affects the performance and life of the compressor. In addition, the traditional centrifugal compressor is prone to the problem of axial force imbalance when the pressure difference between the impeller and the back side of the wheel is too large under high pressure conditions.

SUMMARY OF THE INVENTION

In view of this, the main purpose of the present invention is to provide a centrifugal compressor structure with which the axial force can be automatically balanced, so as to overcome the above-mentioned defects of the prior art.

The technical solution of the present invention to solve the above problem is: a centrifugal compressor structure with an automatic balance of axial force, the special feature of which is that it includes:

Motor housing, spindle, motor, primary volute, secondary volute; the motor is located in the motor housing, and the motor drives the spindle to rotate;

The first-stage volute and the second-stage volute are respectively installed on both ends of the motor casing, and the two ends of the main shaft are respectively installed with a first-stage impeller and a second-stage impeller. inside the stage volute;

A primary shaft seal is provided between the motor housing and the primary volute, and a secondary shaft seal is provided between the motor housing and the secondary volute;

The primary shaft seal separates the chamber of the primary volute from the chamber in the motor housing, and the secondary shaft seal separates the chamber of the secondary volute from the chamber in the motor housing. Separated, on the basis of reducing the leakage of the gas from the impeller outlet to the wheel back, it is ensured that the first-stage impeller and the second-stage impeller in the compressor operate relatively independently and do not affect each other. The motor housing is provided with an upper through hole and a lower through hole respectively at the inner side of the primary shaft seal and the position of the secondary shaft seal, and a filter is connected to the inlet of the upper through hole.

Further, the positions corresponding to the primary shaft seal and the secondary shaft seal on the motor housing are respectively provided with a first vent hole and a third vent hole; the primary shaft seal and the secondary shaft seal open the second vent hole and The fourth vent hole, the outlet axes of the second vent hole and the fourth vent hole are parallel to the main shaft and point to the back of the first stage impeller and the second stage impeller; the first vent hole and the third vent hole are respectively connected with the first The second vent hole communicates with the fourth vent hole.

By adjusting the pressure entering the vent holes and the pressure on the backs of the primary and secondary impellers to balance the axial force with the impellers at all levels, avoid deformation and excessive vibration caused by excessive axial force of a single impeller. big problem. In addition, supplying air to the back of the impeller can reduce the leakage of the impeller outlet and achieve the purpose of effective sealing.

Further, the number of the second ventilation holes and the fourth ventilation holes is multiple, and they are evenly distributed in the circumferential direction, so that the wheel backs of the primary impeller and the secondary impeller have uniform pressure.

Further, a first dynamic pressure radial gas bearing is provided on the main shaft against the inner side of the primary shaft seal; a second dynamic pressure radial gas bearing is provided against the inner side of the secondary shaft seal, and the first dynamic pressure radial gas bearing is provided on the inner side of the secondary shaft seal. The dynamic pressure radial gas bearing and the second dynamic pressure radial gas bearing jointly support the main shaft and bear the radial load of the main shaft, and the joint action of the two-stage impeller wheel back bears the axial load of the main shaft . Using the back of the two-stage impeller wheel directly as the thrust surface not only makes the compressor structure more compact, but also improves the positioning accuracy of the impeller, ensures the safe and stable operation of the impeller in the case of small clearance, and further improves the efficiency of the impeller.

Further, a first-stage inlet and a first-stage outlet are arranged on the above-mentioned first-stage volute, the first-stage inlet is arranged at the center of the first-stage volute, and the first-stage outlet is arranged on the circumference of the first-stage volute; The secondary volute is provided with a secondary inlet and a secondary outlet, the secondary inlet is arranged at the center of the secondary volute, and the secondary outlet is arranged on the circumference of the secondary volute. The primary outlet communicates with the secondary inlet.

Further, the first-stage volute is assembled with the first-stage shaft seal to form a first-stage impeller diffuser, and the first-stage impeller outlet is facing the first-stage impeller-diffuser inlet; the second-stage volute is connected to the first-stage impeller diffuser. The secondary shaft seal is assembled to form a secondary impeller diffuser, and the outlet of the secondary impeller faces the inlet of the secondary impeller diffuser.

Further, the above-mentioned motor includes a motor rotor and a motor stator, the motor stator is fixed in the motor housing, and the motor rotor drives the main shaft to rotate.

Further, the first vent hole and the third vent hole on the above-mentioned motor housing are respectively installed with connectors that communicate with external equipment.

Advantages of the present invention:

1) When the present invention is working, the pressure difference before and after the primary impeller will generate an axial force, and the pressure difference before and after the secondary impeller will also generate an axial force. By adjusting the inlet pressure of the primary shaft seal and the secondary shaft seal to control the wheel back pressure of the primary impeller and the secondary impeller, the axial force generated by the pressure difference between the front and rear of the primary impeller and the pressure difference between the front and rear of the secondary impeller The generated axial force can be balanced out respectively, which avoids the wear and failure of the centrifugal compressor due to the unbalanced axial force, and improves the performance and service life of the compressor.

2) Compact and efficient. The invention directly utilizes the two-stage impeller wheel back as the thrust surface, without the use of thrust bearings, improves the compactness of the compressor, and can ensure the precise positioning of the impeller, reduce the vibration and deformation of the impeller, and reduce the clearance of the impeller. Thereby increasing the efficiency of the impeller. At the same time, the air supply to the wheel back increases the pressure on the wheel back side, which can reduce the leakage of the impeller outlet.

3.) Clean, long life and high reliability. The invention adopts the gas bearing, which not only has no wear, low maintenance cost, but also has good cleanliness. In addition, the axial load of the impellers on both sides can be actively balanced, the running state of the rotor is stable, the reliability of the bearing is high, and the service life is long.

Description of drawings

1 is a schematic structural diagram of a centrifugal compressor whose axial force can be automatically balanced according to an embodiment of the present invention;

Fig. 2 is the structural representation of the primary shaft seal in the centrifugal compressor shown in Fig. 1;

Fig. 3 is the structural representation of the secondary shaft seal in the centrifugal compressor shown in Fig. 1;

FIG. 4 is a schematic diagram of the working principle of the centrifugal compressor shown in FIG. 1 .

Among them: 1. Motor housing, 2. First dynamic pressure radial bearing, 3. Motor, 5. Second dynamic pressure radial bearing, 6. First-stage impeller diffuser, 7. Second-stage impeller diffuser , 12, primary volute, 13, secondary volute, 14, main shaft, 15, motor rotor, 16, motor stator, 17, upper joint, 18, lower joint, 21, primary shaft seal, 22, secondary Shaft seal, 27, primary impeller, 30, secondary impeller, 31, first vent hole, 32, second vent hole, 33, third vent hole, 34, fourth vent hole, 35, upper through hole, 36 , lower through hole, 37, first joint, 38, second joint, 41, primary inlet, 42, primary outlet, 43, secondary inlet, 44, secondary outlet, 48, chamber, 100, centrifugal compressor, 101, secondary compressor, 102, primary compressor, 103, two-stage compression cycle condenser, 104, economizer, 105, first throttle, 106, second throttle, 107, double Stage compression cycle evaporator, 108, liquid storage tank, 109, third throttle valve, 110, fourth throttle valve.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Accordingly, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention.

A centrifugal compressor structure whose axial force can be automatically balanced, as shown in FIG. 1 , includes a motor housing 1 , a main shaft 14 located in the motor housing 1 , and a motor installed in the motor housing 1 3. At the left end of the motor housing 1, a primary volute 12 and a primary shaft seal 21 are installed. At the right end of the motor housing, a secondary volute 13 and a secondary shaft seal 22 are installed. At the left end of the main shaft 14, a first-stage impeller 27 is installed. At the right end of the main shaft 14, a secondary impeller 30 is installed.

A first-stage inlet 41 and a first-stage outlet 42 are provided on the first-stage volute 12, the first-stage inlet 41 is arranged at the center of the first-stage volute 12, and the first-stage outlet 42 is arranged on the circumference of the first-stage volute 12; The casing 13 is provided with a secondary inlet 43 and a secondary outlet 44 .

The primary impeller 27 is located in the primary volute 12 . The primary volute 12 and the primary shaft seal 21 are assembled to form the primary impeller diffuser 6 , and the outlet of the primary impeller 27 faces the inlet of the primary impeller diffuser 6 . The secondary impeller 30 is located in the secondary volute 13 . The secondary volute 13 and the secondary shaft seal 22 are assembled to form the secondary impeller diffuser 7 , and the outlet of the secondary impeller 30 faces the inlet of the secondary impeller diffuser 7 .

The primary shaft seal 21 separates the primary volute chamber 12 from the chamber where the motor 3 is located, and the secondary shaft seal 22 separates the secondary volute 13 chamber from the motor housing 1 chamber, The first-stage impeller 27 and the second-stage impeller 30 in the compressor operate relatively independently and do not affect each other. At the left end of the motor housing 1 in the state shown in FIG. 1, an upper through hole 35 is provided, and the inlet of the upper through hole 35 is connected to the filter and then the upper connector 17 (not shown in the figure) is installed; The casing 1 is provided with a lower through hole 36 near the inner side of the secondary shaft seal 22 , and a lower joint 18 (not shown in the figure) that communicates with external equipment is installed outside the lower through hole 36 . The medium such as coolant can be supplied to the inside of the motor housing 1 through the upper joint 17 and the filter, and then the medium such as the coolant inside the motor housing 1 can be discharged through the lower joint 18 and the lower through hole 36, so that the motor 3 can be discharged. By cooling, it is possible to prevent operation failures caused by overheating of the motor 3 . As a preferred embodiment of the present invention, at the position where the primary shaft seal 21 is installed at the end of the motor housing 1, for example, at the left end of the motor housing 1 in the state shown in FIG. Air hole 31, a first joint 37 (not shown in the figure) that communicates with external equipment is installed outside the first air hole 31; the primary shaft seal 21 opens a second air hole 32, and the inlet axis of the second air hole 32 is connected to the main shaft 14. Vertically, the outlet axis of the second vent hole 32 is parallel to the main shaft 14 and points to the primary impeller 27 ; the first vent hole 31 at the end of the motor housing 1 communicates with the second vent hole 32 on the primary shaft seal 21 .

At the position where the secondary shaft seal 22 is installed at the end of the motor housing 1, for example, at the right end of the motor housing 1 in the state shown in FIG. A second joint 38 (not shown) that communicates with external equipment is installed; the secondary shaft seal 22 opens a fourth vent hole 34, the inlet axis of the fourth vent hole 34 is perpendicular to the main shaft 14, and the outlet axis of the fourth vent hole 34 It is parallel to the main shaft 14 and points to the primary impeller 30 ; the third vent hole 33 at the end of the motor housing 1 communicates with the fourth vent hole 34 on the secondary shaft seal 22 .

As shown in FIGS. 2 and 3 , the second vent hole 32 and the fourth vent hole 34 may include a plurality of vent holes, so that the first-stage impeller 27 and the second-stage impeller 30 have uniform pressure on the wheel backs.

As a preferred embodiment of the present invention, a first dynamic pressure radial gas bearing 2 is provided on the main shaft 14 against the inner side of the primary shaft seal 21, for example, on the left side of the main shaft in the state shown in FIG. 1; The inner side of the secondary shaft seal is provided with a second dynamic pressure radial gas bearing 5 . The two dynamic pressure radial gas bearings jointly support the main shaft and bear the radial load of the main shaft, directly use the back of the two-stage impeller wheel as a thrust surface, and use the joint action of the two-stage impeller wheel back , bear the axial load of the main shaft.

During the working process of the centrifugal compressor, the cooling medium will enter the chamber 48 where the motor is located, and a dynamic pressure radial direction is formed between the first dynamic pressure radial gas bearing 2 , the second dynamic pressure radial gas bearing 5 and the main shaft 14 . Gas friction pair; the medium enters the wheel back of each impeller through the first vent hole 31 and the third vent hole 33 at both ends of the motor casing. Air film, provides axial load and balances the axial force of the impeller. When the main shaft 14 rotates, the medium entering the chamber 48 where the motor is located will flow through the gaps between the first dynamic pressure radial gas bearing 2 , the second dynamic pressure radial gas bearing 5 and the main shaft 14 . The relative movement of the first dynamic pressure radial gas bearing 2, the second dynamic pressure radial gas bearing 5 and the main shaft 14 will produce a dynamic pressure effect, so that the gas film has high pressure and thus has a good bearing capacity, which can make the pressure radial gas bearing reach Self-lubricating effect. Compared with traditional lubricating oil lubrication, it can not only prevent the deterioration of the lubrication state caused by the mutual dissolution of the medium and the lubricating oil, but also prevent the adverse effects caused by the loss of lubricating oil and reduce the heat exchange effect of the medium in the heat exchange equipment.

After the motor 3 is powered on, an alternating magnetic field is generated between the motor rotor 15 and the motor stator 16. The magnetic field acts on the motor rotor 15, so that the motor rotor 15 drives the main shaft 14 to rotate, and the main shaft 14 further drives the primary impeller 27 and the secondary impeller 30. Rotation, the working medium is sucked from the primary inlet 41 and the secondary port 43 respectively, and work is performed on the working medium to increase the pressure of the working medium, and the pressurized working medium has a large kinetic energy after flowing out of the impeller. After passing through the first-stage impeller-diffuser 6 and the second-stage impeller-diffuser 7, most of the kinetic energy is converted into pressure to further increase the pressure of the working medium, and finally passes through the first-stage outlet 42 and the second stage located on the circumference of the first-stage volute 12. The secondary outlet 44 on the circumference of the stage volute 13 discharges.

In the above process, since the working fluid entering the first-stage volute 12 and the second-stage volute 13 is pressurized by the first-stage impeller 27 and the second-stage impeller 30, the wheel front and the second-stage impeller 30 and the first-stage impeller 27 and 30 are There is a pressure difference on the back side of the wheel. In Fig. 1, the left side of the first stage impeller 27 is the front of the wheel and the right side is the back of the wheel. Because the supercharging process occurs in front of the wheel, the average pressure in front of the wheel is lower than the pressure after supercharging, and the back of the wheel has the pressure after supercharging. . The pressure difference between the wheel back pressure and the wheel front pressure will generate an axial force on the main shaft 14, and the direction of the axial force will change due to factors such as the cross-sectional area of the first-stage impeller 27, the cross-sectional area of the main shaft 14, and operating conditions. Similarly, in FIG. 1, the pressure difference between the back pressure and the front pressure of the secondary impeller 30 will also generate an axial force on the main shaft 14. The cross-sectional area, operating conditions and other factors have changed. In the design process, try to balance the axial force generated by the back pressure difference of the first-stage impeller 27 and the front wheel of the second-stage impeller 30 to balance each other, so as to avoid the failure caused by the unbalanced axial force. and losses.

In order to illustrate the working principle of the centrifugal compressor structure in which the axial force can be automatically balanced according to the embodiment of the present invention, the principle is described using only a one-stage throttling two-stage compression cycle with an economizer as an example. Embodiments of the present invention are not limited to this cycle, and can also be applied to various other types of two-stage compression cycles. 4, the working principle of the centrifugal compressor of the embodiment of the present invention is:

The centrifugal compressor 100 provided by the embodiment of the present invention is powered on, and the working medium first flows through the primary inlet 41 at the center of the primary volute 12 of the primary compressor 102 and enters the inner cavity of the primary volute 12 . The first-stage impeller 27 of the first-stage compressor 102 works on the inhaled gas working medium to increase the pressure of the gas working medium. The pressurized gas working medium flows out of the primary compressor 102 through the outlet 42 in the circumferential direction of the primary volute 12 , and enters the secondary compressor 101 from the secondary inlet 43 at the center of the secondary volute 13 . After the secondary impeller 30 of the secondary compressor 101 performs work on the gas working medium, the secondary outlet 44 in the circumferential direction of the secondary volute 13 flows out of the secondary compressor. During the working process of the primary compressor 102, as the rotational speed of the main shaft 14 gradually increases, the first dynamic pressure radial gas bearing 2 and the second dynamic pressure radial gas bearing 5 respectively form a gas film with the main shaft 14, and the lubrication form changes. For gas lubrication.

The high-temperature and high-pressure gaseous refrigerant pressurized by the secondary compressor 101 flows through the dual-stage compression cycle condenser 103 to cool down into a liquid state and enter the liquid storage tank 108 . One refrigerant flows through the first throttle valve 105 and then enters the economizer 104 to absorb heat to reduce the temperature of the other refrigerant in the economizer, and then the refrigerant passes through the upper joint 17 on the centrifugal compressor 100 and passes through the filter to remove impurities and enter the electricity. The casing 1 flows out through the lower joint 18 after cooling the motor 3 in the motor casing 1 . Then, it is mixed with the outlet gas of the primary compressor 102 and then enters the secondary inlet 43 at the center of the secondary compressor 101 for secondary compression. The other refrigerant first flows through the economizer 104 to cool down (heat is absorbed by the previous refrigerant), flows through the second throttle valve 106, and then flows into the two-stage compression cycle evaporator 107 to evaporate and absorb heat to generate cooling capacity, and then be absorbed by the first-stage refrigerant. Compressor 102 sucks for the next cycle.

The high temperature and high pressure gas flowing out through the secondary outlet 44 of the secondary compressor 101 not only flows into the condenser to participate in the main circulation, but also separates two refrigerants. One channel of refrigerant flows through the third throttle valve 109 and then flows through the first vent hole 31 and the second vent hole 32 through the joint 37 and then reaches the back of the first-stage impeller 27 to adjust the pressure difference between the front and the back of the first-stage impeller 27 , and then part of the refrigerant is discharged with the first-stage compression, and part of the refrigerant flows through the first-stage shaft seal into the motor housing and then enters the second-stage compression. The other refrigerant flows through the fourth throttle valve 110 and then flows through the joint 38 through the third vent hole 33 and the fourth vent hole 34 and then reaches the back of the secondary impeller 30 to adjust the pressure in front of the secondary impeller 30 and on the back of the wheel. Then, part of the refrigerant is discharged with the secondary compression, and part of the refrigerant flows through the secondary shaft seal 22 and enters the motor housing 1 and then enters the secondary compression.

The above descriptions are only the embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the description and drawings of the present invention, or directly or indirectly applied to other related The system field is similarly included in the protection scope of the present invention.

Claims (7)

1. A centrifugal compressor structure with an automatically balanced axial force is characterized in that:

comprises a motor shell (1), a main shaft (14), a motor (3), a first-stage volute (12) and a second-stage volute (13); the motor (3) is positioned in the motor shell (1), and the motor (3) drives the spindle (14) to rotate;

the primary volute (12) and the secondary volute (13) are respectively installed at two ends of the motor shell (1), the two ends of the main shaft (14) are back-to-back respectively provided with a primary impeller (27) and a secondary impeller (30), and the primary impeller (27) and the secondary impeller (30) are respectively located in the primary volute (12) and the secondary volute (13);

a primary shaft seal (21) is arranged between the motor shell (1) and the primary volute (12), and a secondary shaft seal (22) is arranged between the motor shell (1) and the secondary volute (13);

the primary shaft seal (21) separates a chamber of the primary volute (12) from a chamber in the motor shell (1), and the secondary shaft seal (22) separates a chamber of the secondary volute (13) from a chamber in the motor shell (1); an upper through hole (35) and a lower through hole (36) are respectively formed in the position, close to the inner side of the primary shaft seal (21), of the motor shell (1) and the position, close to the secondary shaft seal (22), of the motor shell, and the inlet of the upper through hole (35) is connected with a filter;

a first vent hole (31) and a third vent hole (33) are respectively formed in the positions, corresponding to the primary shaft seal (21) and the secondary shaft seal (22), on the motor shell (1); the primary shaft seal (21) and the secondary shaft seal (22) are provided with a second vent hole (32) and a fourth vent hole (34), and outlet axes of the second vent hole (32) and the fourth vent hole (34) are parallel to the main shaft (14) and point to wheel backs of the primary impeller (27) and the secondary impeller (30); the first vent hole (31) and the third vent hole (33) are respectively communicated with the second vent hole (32) and the fourth vent hole (34).

2. A centrifugal compressor structure with self-balancing axial force, as claimed in claim 1, wherein:

the number of the second vent holes (32) and the fourth vent holes (34) is multiple, and the second vent holes and the fourth vent holes are uniformly distributed in the circumferential direction.

3. A centrifugal compressor structure capable of automatically balancing axial force according to claim 2, wherein:

a first dynamic pressure radial gas bearing (2) is arranged on the main shaft (14) and abuts against the inner side of the primary shaft seal (21); and a second dynamic pressure radial gas bearing (5) is arranged on the inner side of the secondary shaft seal (22) in a propping manner, and the main shaft (14) is supported by the first dynamic pressure radial gas bearing (2) and the second dynamic pressure radial gas bearing (5) together.

4. A centrifugal compressor structure with self-balancing axial force, as claimed in claim 3, wherein:

a primary inlet (41) and a primary outlet (42) are arranged on the primary volute (12), the primary inlet (41) is arranged at the central position of the primary volute (12), and the primary outlet (42) is arranged on the circumference of the primary volute (12); the two-stage volute (13) is provided with a two-stage inlet (43) and a two-stage outlet (44), the two-stage inlet (43) is arranged at the center of the two-stage volute (13), the two-stage outlet (44) is arranged on the circumference of the two-stage volute (13), and the one-stage outlet (42) is communicated with the two-stage inlet (43).

5. A centrifugal compressor structure with self-balancing axial force, as claimed in claim 4, wherein:

the first-stage volute (12) and the first-stage shaft seal (21) are assembled to form a first-stage impeller diffuser (6), and the outlet of the first-stage impeller (27) is opposite to the inlet of the first-stage impeller (27) diffuser (6); the two-stage volute (13) and the two-stage shaft seal (22) are assembled to form a two-stage impeller diffuser (7), and the outlet of the two-stage impeller (30) is over against the inlet of the two-stage impeller diffuser (7).

6. A centrifugal compressor structure capable of automatically balancing axial force according to claim 5, wherein:

the motor (3) comprises a motor (3) rotor and a motor (3) stator, the motor (3) stator is fixed in the motor shell (1), and the motor (3) rotor drives the spindle (14) to rotate.

7. A centrifugal compressor structure with self-balancing axial force, as claimed in claim 6, wherein:

and joints communicated with external equipment are respectively arranged on the first vent hole (31) and the third vent hole (33) on the motor shell (1).

Images