CN107725113B - Two-stage cantilever type axial flow expander - Google Patents
Two-stage cantilever type axial flow expander Download PDFInfo
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- CN107725113B CN107725113B CN201711051562.9A CN201711051562A CN107725113B CN 107725113 B CN107725113 B CN 107725113B CN 201711051562 A CN201711051562 A CN 201711051562A CN 107725113 B CN107725113 B CN 107725113B
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- 238000004804 winding Methods 0.000 claims abstract description 13
- 238000001816 cooling Methods 0.000 claims description 17
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- 229910000831 Steel Inorganic materials 0.000 claims description 7
- 239000010959 steel Substances 0.000 claims description 7
- 238000006243 chemical reaction Methods 0.000 abstract description 4
- 239000007789 gas Substances 0.000 description 47
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 34
- 239000003345 natural gas Substances 0.000 description 17
- 239000000725 suspension Substances 0.000 description 17
- 238000005461 lubrication Methods 0.000 description 15
- 238000007789 sealing Methods 0.000 description 15
- 238000010248 power generation Methods 0.000 description 14
- 239000010687 lubricating oil Substances 0.000 description 10
- 239000003921 oil Substances 0.000 description 9
- 230000000694 effects Effects 0.000 description 6
- 238000000034 method Methods 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000005086 pumping Methods 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000008676 import Effects 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 230000002706 hydrostatic effect Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 239000002918 waste heat Substances 0.000 description 1
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D1/00—Non-positive-displacement machines or engines, e.g. steam turbines
- F01D1/02—Non-positive-displacement machines or engines, e.g. steam turbines with stationary working-fluid guiding means and bladed or like rotor, e.g. multi-bladed impulse steam turbines
- F01D1/04—Non-positive-displacement machines or engines, e.g. steam turbines with stationary working-fluid guiding means and bladed or like rotor, e.g. multi-bladed impulse steam turbines traversed by the working-fluid substantially axially
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D13/00—Combinations of two or more machines or engines
- F01D13/02—Working-fluid interconnection of machines or engines
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D17/00—Regulating or controlling by varying flow
- F01D17/10—Final actuators
- F01D17/12—Final actuators arranged in stator parts
- F01D17/14—Final actuators arranged in stator parts varying effective cross-sectional area of nozzles or guide conduits
- F01D17/16—Final actuators arranged in stator parts varying effective cross-sectional area of nozzles or guide conduits by means of nozzle vanes
- F01D17/162—Final actuators arranged in stator parts varying effective cross-sectional area of nozzles or guide conduits by means of nozzle vanes for axial flow, i.e. the vanes turning around axes which are essentially perpendicular to the rotor centre line
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
- F01D25/16—Arrangement of bearings; Supporting or mounting bearings in casings
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
- F01D25/24—Casings; Casing parts, e.g. diaphragms, casing fastenings
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
- F01D5/02—Blade-carrying members, e.g. rotors
- F01D5/06—Rotors for more than one axial stage, e.g. of drum or multiple disc type; Details thereof, e.g. shafts, shaft connections
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K5/00—Casings; Enclosures; Supports
- H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
- H02K5/18—Casings or enclosures characterised by the shape, form or construction thereof with ribs or fins for improving heat transfer
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K5/00—Casings; Enclosures; Supports
- H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
- H02K5/20—Casings or enclosures characterised by the shape, form or construction thereof with channels or ducts for flow of cooling medium
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K9/00—Arrangements for cooling or ventilating
- H02K9/02—Arrangements for cooling or ventilating by ambient air flowing through the machine
- H02K9/04—Arrangements for cooling or ventilating by ambient air flowing through the machine having means for generating a flow of cooling medium
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
- Magnetic Bearings And Hydrostatic Bearings (AREA)
Abstract
The invention discloses a two-stage cantilever type axial flow expander, which comprises a first-stage expander, a second-stage expander and a motor; the first-stage expander comprises an air inlet shell, a first-stage nozzle ring and a first-stage rotor impeller; the second expander comprises a unit outer shell, a second-stage nozzle ring and a second-stage rotor impeller; the motor comprises a motor rotor and a stator winding; the air inlet shell is arranged opposite to the machine set shell to form a cavity, the motor rotor is arranged in the cavity along the axis of the cavity, the auxiliary pushing bearing shell, the motor shell and the second-stage flow guiding shell are sequentially arranged on the outer edge of the motor rotor in the direction from the air inlet shell to the machine set shell, a first-stage input end is coaxially arranged on the end face, close to the air inlet shell, of the motor rotor, and a second-stage input end is coaxially arranged on the end face, close to the machine set shell, of the motor rotor. The invention utilizes two-stage axial flow, can effectively reduce the rotating speed of the expander, improves the reliability and efficiency of the motor and the frequency converter, and obtains higher energy conversion rate.
Description
Technical Field
The invention relates to the technical field of expanders in residual pressure and waste heat power generation systems, in particular to a two-stage cantilever type axial flow expander.
Background
At present, valves are adopted for pressure regulation of natural gas transmission and distribution pipe networks in China, so that pressure energy is not utilized, and a large amount of energy is wasted. The annual consumption of natural gas in China is about 2000 hundred million cubic meters, wherein more than 1300 hundred million cubic meters are self-picked, and more than 600 hundred million cubic meters are imported. The pressure regulating links with different degrees exist from the gas extraction port to the user, and the expander is adopted to replace the pressure regulating valve for reducing the pressure, so that the wasted pressure energy can be recovered and converted into mechanical energy for power generation
Natural gas is a flammable and explosive gas, and once leaked, has a great potential safety hazard. At present, a plurality of natural gas differential pressure power generation demonstration projects built in China all have a plurality of problems, and the most important problem is natural gas leakage. The traditional method is to install a shaft end seal on the expander output shaft. The adopted seal mainly comprises a piston ring, a mechanical seal and a dry gas seal. The piston ring has low sealing price and simple structure, but has poor sealing performance and is often accompanied by small natural gas leakage. The mechanical seal requires high-pressure oil stations to cooperate, high-pressure lubricating oil is utilized to seal gas, and a small amount of lubricating oil permeates into the expander and is further attached to downstream equipment. In addition, the mechanical seal has short service life and frequent maintenance of the unit. The dry gas sealing system is complex, high in cost, high-pressure nitrogen is consumed in a large amount in the use process, high-pressure nitrogen is consumed for a long time even after the machine set is stopped, and the dry gas sealing system is high in operation cost and suitable for being used on high-power equipment with the temperature of more than megawatts.
In addition, if the generator set adopts oil lubrication, after the lubricating oil leaks into a natural gas pipeline, the downstream gas transmission and distribution can be influenced.
In a natural gas differential pressure power generation system, the working medium pressure is high, and the gas density is high, so that the volume flow of a unit is very small and the power density is very high under the condition of increasing the mass flow. At present, a small-flow expander mostly adopts a centripetal turbine, but the single-stage centripetal turbine has high rotating speed, a plurality of stages of centripetal turbine pipelines are complex, the pipeline connecting flanges are more, and the potential leakage points are more. The centripetal turbine has small application range to the rotating speed during design due to the limitation of the self geometric shape of the impeller, and the space for reducing the rotating speed is very limited. The rotating speed of the unit is high, and the motor power is difficult to meet the design requirement.
Organic RANKINE CYCLE (ORC) power generation has many common sites with natural gas pressure differential power generation. The working media are hydrocarbon organic matters, and the expansion machines are adopted to convert pressure energy into electric energy, so that the problems are basically consistent.
In the natural gas differential pressure power generation system and the ORC power generation system, the working pressure of an expander is high, and most of the working pressure of a unit is megapascal. Because of the high air pressure, the axial thrust of the expander is very large. Even if the generating power of the unit is about 100kW, if the axial thrust is not specially adjusted, the axial thrust of part of the unit can reach more than 10000 newtons. If oil-free lubrication technology such as magnetic suspension or air suspension bearing is adopted, the axial thrust which can be born by the unit is very limited, and is usually controlled below 1000N, so that the axial thrust is reduced from the angle of the design of the blades of the expander, and the design requirement can not be met frequently.
In summary, the existing expander is applied to the natural gas and organic rankine cycle system, and mainly has the following problems:
1. Sealing problems;
2. The lubricating oil causes pollution to working medium gas;
3. the rotating speed of the unit is high and the reliability is poor;
4. The axial thrust of the expander is very large, and the axial thrust which the unit can bear is very limited;
5. the service life is short, and the maintenance is frequent;
6. The system is complex and the cost is high.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a two-stage cantilever type axial flow expander, which adopts two-stage axial flow impellers to be respectively hung at two ends of a motor and connected with the motor coaxially. The two-stage axial flow is utilized, so that the rotating speed of the expander can be effectively reduced, the reliability and the efficiency of the motor and the frequency converter are improved, and a higher energy conversion rate is obtained. And the motor shell is cooled by utilizing the movable vane outlet gas, so that the cooling efficiency is improved. By adopting the oil-free lubrication bearing, the influence on downstream facilities and equipment caused by the penetration of the lubricating oil into the pipeline can be completely avoided. The unit has no rotating part connected to the outside, only the static seal at the flange is contacted with the outside, and no dynamic seal connected with the outside is provided, thus realizing zero leakage of working medium.
The technical scheme adopted by the invention is as follows:
A two-stage cantilever type axial flow expander comprises a first-stage expander, a second-stage expander and a motor; the first-stage expander comprises an air inlet shell, a first-stage nozzle ring and a first-stage rotor impeller; the second expander comprises a unit outer shell, a second-stage nozzle ring and a second-stage rotor impeller; the motor comprises a motor rotor and a stator winding; the air inlet shell and the unit shell are arranged in a cavity along the axis of the cavity, the motor rotor is sequentially provided with an auxiliary pushing bearing shell, a motor shell and a second-stage flow guiding shell along the direction from the air inlet shell to the unit shell, a first-stage input end is coaxially arranged on the end face, close to the air inlet shell, of the motor rotor, a second-stage input end is coaxially arranged on the end face, close to the unit shell, of the motor rotor, and the stator winding is mounted on the inner side of the motor shell; the first-stage nozzle ring is arranged in the air inlet shell, and the first-stage rotor impeller is arranged on the first-stage input end; the second-stage nozzle is arranged on the second-stage diversion shell in a ring mode, and the second-stage rotor impeller is arranged on the second-stage input end; the motor rotor is sleeved with a rotor thrust disc and a first-stage side radial bearing at one end close to the air inlet shell, thrust bearings are arranged at two sides of the rotor thrust disc, the first-stage side radial bearing is positioned at one side of the rotor thrust disc far away from the air inlet shell, and a second-stage side radial bearing is sleeved at one end of the motor rotor close to the unit outer shell; one end of the air inlet shell body, which is far away from the air unit shell body, is provided with an air inlet, and one end of the air unit shell body, which is far away from the air inlet shell body, is provided with an air outlet.
The two-stage axial flow is utilized, so that the rotating speed of the expander can be effectively reduced, the reliability and the efficiency of the motor and the frequency converter are improved, and a higher energy conversion rate is obtained.
Because the power density of the natural gas expansion power generation unit and the ORC power generation unit with high pressure is very high, the unit rotating speed below 300kW is very high. Particularly, a single-stage centripetal turbine is adopted, and under the condition of ensuring the high performance of the expander, the required rotating speed is very high, so that the motor is difficult to meet the use requirement. In order to ensure stable operation of the motor, it is necessary to forcibly reduce the rotational speed by sacrificing the efficiency of the expander. By adopting the invention, higher aerodynamic performance can be obtained by using lower rotating speed.
The unit has no dynamic seal and is connected with the outside, and the zero leakage of the power generation system can be realized only by connecting the unit with a gas pipeline through a flange, so that the operation of the unit is safe and reliable.
Preferably, the thrust bearing is a static pressure air bearing, one side of the unit outer shell is provided with an air inlet communicated with the thrust bearing, and the thrust bearing is provided with a small hole leading to the end face of the rotor thrust disc.
The high-pressure air source input by the thrust bearing flows to the rotor thrust disc through the small hole on the thrust bearing to form an air film, so that the air lubrication function is realized.
In the operation process of the air bearing, the rotating part and the static part are not in direct contact, the friction loss is small, and the mechanical efficiency is high.
The machine set adopts oil-free lubrication, and lubricating oil does not enter a circulating system, so that working medium is polluted, and downstream equipment is affected.
The existing expander mainly adopts an oil lubrication bearing or a magnetic suspension bearing. The oil lubrication bearing unit can completely solve the leakage of natural gas by adopting expensive dry gas sealing on the output shaft of the expander. The dry gas seal needs a complex control system besides the seal body, and the domestic dry gas seal is about 20 ten thousand yuan/set, so that the import is more expensive. The invention does not require expensive dry gas seals. Although air bearing is more expensive than oil lubricated bearings, it is still much cheaper than dry gas seals. The unit adopting the magnetic suspension bearing does not need expensive dry gas sealing, but the current magnetic suspension bearing is very expensive, and needs professional personnel to install and debug on site, and the cost is far higher than that of the air suspension bearing.
Preferably, the thrust bearing is further provided with a bearing exhaust hole communicated with the inside of the motor.
The thrust bearing is provided with an exhaust hole leading to the inside of the motor, and working medium gas exhausted by the bearing is exhausted to the inside of the motor and used for cooling the rotor magnetic steel of the motor.
Preferably, the first-stage side radial bearing and the second-stage side radial bearing are static pressure or dynamic pressure air bearing.
In order to solve the problem of working medium leakage, prevent lubricating oil from entering natural gas and reduce mechanical loss, the motor bearing adopts an oil-free lubrication gas suspension bearing, namely an air suspension bearing for short. The thrust bearing adopts a static pressure air bearing, and the radial bearing adopts a static pressure or dynamic pressure air bearing. All rotating parts of the unit are sealed inside the shell, and no position is contacted with the external environment.
Preferably, a labyrinth seal is processed between the first-stage nozzle ring and the first-stage rotor impeller; the motor rotor is characterized in that magnetic steel corresponding to the stator winding is arranged in the middle of the motor rotor, two ends of the motor rotor are of hollow structures, a through hole is formed in the axis of the first-stage input end, the through hole is communicated with a hollow part of the motor rotor, which is close to one end of the air inlet shell, a plurality of thrust regulation exhaust holes are formed in the side wall of the hollow part, and the thrust regulation exhaust holes are uniformly distributed around the axis of the motor rotor.
A labyrinth seal is processed between the first-stage nozzle ring and the first-stage rotor impeller, an axial thrust adjusting device is formed by combining a first-stage input end and a thrust adjusting exhaust hole of a hollow part of the motor rotor and is used for adjusting the axial thrust of the motor rotor, and exhaust gas of the axial thrust adjusting device is introduced into the motor to strengthen the cooling of magnetic steel of the motor rotor.
Exhaust holes are uniformly distributed on the side wall of the hollow part of the motor rotor, which is close to one end of the air inlet shell, and the motor rotor plays a role in pumping air under high-speed rotation to suck working medium air, which is close to one end of the air inlet shell. Through the adjustment to exhaust hole quantity, aperture and eccentric volume, can play different suction effects. When the exhaust hole is used for exhausting, high-pressure gas between the first-stage nozzle ring and the first-stage rotor impeller flows to the motor rotor through a gap between the nozzle ring and the impeller, so that a sealing structure is arranged between the first-stage nozzle ring and the first-stage rotor impeller, the pressure of the high-pressure gas between the nozzle ring and the impeller is reduced when the high-pressure gas flows to the motor rotor, the pumping effect of the exhaust hole is different, and the reduction of the gas pressure is different.
Preferably, a plurality of motor cooling exhaust holes are formed in the side wall of the hollow part of the motor rotor, which is close to one end of the unit outer shell, the motor cooling exhaust holes are uniformly distributed around the axis of the motor rotor, and a through hole is formed in the axis of the second-stage input end and is communicated with the hollow part of the motor rotor, which is close to one end of the unit outer shell.
The cooling air in the motor passes through the motor cooling exhaust hole and is discharged into the outlet pipeline from the through hole on the second-stage input end.
The cavity between the motor shell and the unit shell is used as a passage for working medium gas to flow from the first stage to the second stage.
Preferably, the outer side of the motor housing is fitted or milled with a plurality of fins along its axial direction.
The heat exchange area is increased through the fins, and the first-stage outlet working medium gas is utilized to dissipate heat of the stator winding. The fin and the motor rotor have the same axial direction, so that the working medium airflow loss can be reduced, and the rectification effect can be realized.
The beneficial effects of the invention are as follows:
1. no dynamic seal exists between the unit and the external environment, so that zero leakage can be realized;
2. the unit adopts oil-free lubrication, so that lubricating oil does not enter a circulating system, and pollution is caused to working medium gas, thereby affecting downstream equipment;
3. higher overall performance: by adopting the invention, higher pneumatic performance can be obtained by using lower rotating speed, and in the running process of the air bearing, the rotating part and the static part are not in direct contact, so that the friction loss is small, and the mechanical efficiency is high;
4. the lower working rotation speed improves the reliability of the unit: by adopting the invention, the working rotation speed is lower under the condition of ensuring the pneumatic performance, so that the unit can run below a first-order bending mode, and the running reliability of the unit is improved;
5. through the exhaust holes uniformly distributed on the hollow shaft, the static pressure of the impeller wheel disc is reduced by combining the sealing between the nozzle ring and the impeller, so that the axial thrust of the rotor is reduced;
6. The control system is simple: the axial thrust of the expander is increased along with the rising of inlet air pressure, and is close to a proportional relation, working medium gas of an inlet pipeline of the expander is used as a bearing air source, a complex control system is not needed, the bearing capacity is automatically increased along with the rising of inlet air pressure, and the unit can normally operate under larger inlet pressure fluctuation;
7. lower manufacturing cost: the invention does not need to adopt expensive dry gas sealing, and the cost of the air bearing is higher than that of an oil lubrication bearing, but the air bearing is cheaper than the dry gas sealing; the unit adopting the magnetic suspension bearing does not need expensive dry gas sealing, but the current magnetic suspension bearing is very expensive, and needs professional personnel to go to the site for installation and debugging, and the cost is far higher than that of the air suspension bearing;
8. the service life is long: after the machine set reaches the working rotation speed, the rotating part is not contacted with the static part, no abrasion is caused, and the machine set can run for a long time.
Drawings
FIG. 1 is a schematic diagram of an embodiment of the present invention;
FIG. 2 is a schematic view of the structure of section A in FIG. 1;
FIG. 3 is a schematic view of the structure of section B in FIG. 2;
reference numerals: 11-first-stage nozzle ring, 12-first-stage rotor impeller, 1112-labyrinth seal, 121-first-stage input, 13-intake housing, 21-second-stage nozzle ring, 22-second-stage rotor impeller, 221-second-stage input, 23-unit outer housing, 31-motor rotor, 32-stator winding, 33-motor housing, 34-auxiliary thrust bearing housing, 35-thrust bearing, 36-first-stage side radial bearing, 37-bearing housing, 38-second-stage flow guiding housing, 39-second-stage side radial bearing, 361-bearing exhaust vent, 311-rotor thrust disk, 312-thrust adjustment exhaust vent, 313-motor cooling exhaust vent.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
Examples
As shown in fig. 1 and 2, a two-stage cantilever type axial flow expander comprises a first-stage expander, a second-stage expander and a motor; the first-stage expander comprises an air inlet shell 13, a first-stage nozzle ring 11 and a first-stage rotor impeller 12; the second expander comprises a unit outer casing 23, a second stage nozzle ring 21 and a second stage rotor impeller 22; the motor comprises a motor rotor 31 and stator windings 32; the air inlet shell 13 and the unit outer shell 23 are oppositely arranged to form a cavity, the motor rotor 31 is arranged in the cavity along the axis of the cavity, an auxiliary pushing bearing shell 34, a motor shell 33 and a second-stage flow guiding shell 38 are sequentially arranged outside the motor rotor 31 along the direction from the air inlet shell 13 to the unit outer shell 23, a first-stage input end 121 is coaxially arranged on the end surface of the motor rotor 31, which is close to the air inlet shell 13, a second-stage input end 221 is coaxially arranged on the end surface of the motor rotor 31, which is close to the unit outer shell 23, and the stator winding 32 is arranged on the inner side of the motor shell 33; the first-stage nozzle ring 11 is installed in the air inlet shell 13, and the first-stage rotor impeller 13 is installed on the first-stage input end 121; the second-stage nozzle ring 21 is arranged on the second-stage diversion shell 38, and the second-stage rotor impeller 22 is arranged on the second-stage input end 221; the end of the motor rotor 31, which is close to the air inlet shell 13, is sleeved with a rotor thrust disc 311 and a first-stage side radial bearing 36, a bearing shell 37 is arranged outside the first-stage side radial bearing 36 and is used for isolating the interior of the motor shell 33 from the end of the motor rotor 31, thrust bearings 35 are arranged on two sides of the rotor thrust disc 311, the first-stage side radial bearing 36 is positioned on one side, which is far away from the air inlet shell 13, of the rotor thrust disc 311, one end, which is close to the unit outer shell 23, of the motor rotor 31 is sleeved with a second-stage side radial bearing 39, and an isolating part extending towards the motor rotor 31 is arranged on one end, which is close to the unit outer shell 23, of the motor shell 33 and is used for isolating the interior of the motor shell 33 from the end of the motor rotor 31; the air inlet is arranged at one end of the air inlet shell 13 far away from the unit outer shell 23, and the air outlet is arranged at one end of the unit outer shell 23 far away from the air inlet shell 13.
The two-stage axial flow is utilized, so that the rotating speed of the expander can be effectively reduced, the reliability and the efficiency of the motor and the frequency converter are improved, and a higher energy conversion rate is obtained.
Because the power density of the natural gas expansion power generation unit and the ORC power generation unit with high pressure is very high, the unit rotating speed below 300kW is very high. Particularly, a single-stage centripetal turbine is adopted, and under the condition of ensuring the high performance of the expander, the required rotating speed is very high, so that the motor is difficult to meet the use requirement. In order to ensure stable operation of the motor, it is necessary to forcibly reduce the rotational speed by sacrificing the efficiency of the expander. By adopting the invention, higher aerodynamic performance can be obtained by using lower rotating speed.
The unit has no dynamic seal and is connected with the outside, and the zero leakage of the power generation system can be realized only by connecting the unit with a gas pipeline through a flange, so that the operation of the unit is safe and reliable.
In one embodiment, the thrust bearing 35 is a static pressure air bearing, one side of the unit outer casing 23 is provided with an air inlet communicated with the thrust bearing 35, and the thrust bearing 35 is provided with a small hole leading to the end face of the rotor thrust disc 311.
The high-pressure air source input by the thrust bearing flows to the rotor thrust disc through the small hole on the thrust bearing to form an air film, so that the air lubrication function is realized.
In the operation process of the air bearing, the rotating part and the static part are not in direct contact, the friction loss is small, and the mechanical efficiency is high.
The machine set adopts oil-free lubrication, and lubricating oil does not enter a circulating system, so that working medium is polluted, and downstream equipment is affected.
The existing expander mainly adopts an oil lubrication bearing or a magnetic suspension bearing. The oil lubrication bearing unit can completely solve the leakage of natural gas by adopting expensive dry gas sealing on the output shaft of the expander. The dry gas seal needs a complex control system besides the seal body, and the domestic dry gas seal is about 20 ten thousand yuan/set, so that the import is more expensive. The invention does not require expensive dry gas seals. Although air bearing is more expensive than oil lubricated bearings, it is still much cheaper than dry gas seals. The unit adopting the magnetic suspension bearing does not need expensive dry gas sealing, but the current magnetic suspension bearing is very expensive, and needs professional personnel to install and debug on site, and the cost is far higher than that of the air suspension bearing.
In another embodiment, the thrust bearing 35 is further provided with a bearing vent 361 communicating with the interior of the motor.
The thrust bearing is provided with an exhaust hole leading to the inside of the motor, and working medium gas exhausted by the bearing is exhausted to the inside of the motor and used for cooling the rotor magnetic steel of the motor.
In another embodiment, the first stage side radial bearing 36 and the second stage side radial bearing 39 are hydrostatic or hydrodynamic air bearing.
In order to solve the problem of working medium leakage, prevent lubricating oil from entering natural gas and reduce mechanical loss, the motor bearing adopts an oil-free lubrication gas suspension bearing, namely an air suspension bearing for short. The thrust bearing adopts a static pressure air bearing, and the radial bearing adopts a static pressure or dynamic pressure air bearing. All rotating parts of the unit are sealed inside the shell, and no position is contacted with the external environment.
In another embodiment, a labyrinth seal 1112 is machined between the first stage nozzle ring 11 and the first stage rotor wheel 12; the middle part of motor rotor 31 is equipped with the magnet steel that corresponds with stator winding 32, the both ends of motor rotor 31 are hollow structure, the axle center department of first level input 121 is equipped with the through-hole, and this through-hole communicates with the hollow part that motor rotor 31 is close to air inlet housing 13 one end, and is equipped with a plurality of thrust regulation exhaust holes 312 on the lateral wall of this hollow part, thrust regulation exhaust hole 312 is evenly distributed around the axle center of motor rotor 31, and this thrust regulation exhaust hole 312 is located the outside of bearing shell 37.
A labyrinth seal is processed between the first-stage nozzle ring and the first-stage rotor impeller, an axial thrust adjusting device is formed by combining a first-stage input end and a thrust adjusting exhaust hole of a hollow part of the motor rotor and is used for adjusting the axial thrust of the motor rotor, and exhaust gas of the axial thrust adjusting device is introduced into the motor to strengthen the cooling of magnetic steel of the motor rotor.
Exhaust holes are uniformly distributed on the side wall of the hollow part of the motor rotor, which is close to one end of the air inlet shell, and the motor rotor plays a role in pumping air under high-speed rotation to suck working medium air, which is close to one end of the air inlet shell. As shown in fig. 3, by adjusting the number of the exhaust holes, the aperture Φb and the eccentric amount a, different suction effects can be achieved. When the exhaust hole is used for exhausting, high-pressure gas between the first-stage nozzle ring and the first-stage rotor impeller flows to the motor rotor through a gap between the nozzle ring and the impeller, so that a sealing structure is arranged between the first-stage nozzle ring and the first-stage rotor impeller, the pressure of the high-pressure gas between the nozzle ring and the impeller is reduced when the high-pressure gas flows to the motor rotor, the pumping effect of the exhaust hole is different, and the reduction of the gas pressure is different.
In another embodiment, a plurality of motor cooling exhaust holes 313 are formed in the side wall of the hollow portion of the motor rotor 31 near one end of the unit housing 23, the motor cooling exhaust holes 313 are uniformly distributed around the axis of the motor rotor 31, the motor cooling exhaust holes 313 are located at the inner side of the isolation portion, and a through hole is formed at the axis of the second-stage input end 221, and the through hole is communicated with the hollow portion of the motor rotor 31 near one end of the unit housing 23.
The cooling air in the motor passes through the motor cooling exhaust hole and is discharged into the outlet pipeline from the through hole on the second-stage input end.
The cavity between the motor shell and the unit shell is used as a passage for working medium gas to flow from the first stage to the second stage.
In another embodiment, the outer side of the motor housing 33 is provided with a plurality of fins mounted or milled in the axial direction thereof.
The heat exchange area is increased through the fins, and the first-stage outlet working medium gas is utilized to dissipate heat of the stator winding. The fin and the motor rotor have the same axial direction, so that the working medium airflow loss can be reduced, and the rectification effect can be realized.
The foregoing examples merely illustrate specific embodiments of the invention, which are described in greater detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention.
Claims (3)
1. The two-stage cantilever type axial flow expander is characterized by comprising a first-stage expander, a second-stage expander and a motor; the first-stage expander comprises an air inlet shell, a first-stage nozzle ring and a first-stage rotor impeller; the second-stage expander comprises a unit outer shell, a second-stage nozzle ring and a second-stage rotor impeller; the motor comprises a motor rotor and a stator winding; the air inlet shell and the unit shell are arranged in a cavity along the axis of the cavity, the motor rotor is sequentially provided with an auxiliary pushing bearing shell, a motor shell and a second-stage flow guiding shell along the direction from the air inlet shell to the unit shell, a first-stage input end is coaxially arranged on the end face, close to the air inlet shell, of the motor rotor, a second-stage input end is coaxially arranged on the end face, close to the unit shell, of the motor rotor, and the stator winding is mounted on the inner side of the motor shell; the first-stage nozzle ring is arranged in the air inlet shell, and the first-stage rotor impeller is arranged on the first-stage input end; the second-stage nozzle is arranged on the second-stage diversion shell in a ring mode, and the second-stage rotor impeller is arranged on the second-stage input end; the motor rotor is sleeved with a rotor thrust disc and a first-stage side radial bearing at one end close to the air inlet shell, thrust bearings are arranged at two sides of the rotor thrust disc, the first-stage side radial bearing is positioned at one side of the rotor thrust disc far away from the air inlet shell, and a second-stage side radial bearing is sleeved at one end of the motor rotor close to the unit outer shell; an air inlet is formed in one end, far away from the air inlet shell, of the air inlet shell, and an air outlet is formed in one end, far away from the air inlet shell, of the air inlet shell;
the thrust bearing is a static pressure air bearing, one side of the outer shell of the unit is provided with an air inlet communicated with the thrust bearing, and the thrust bearing is provided with a small hole leading to the end face of the rotor thrust disc;
the thrust bearing is also provided with a bearing exhaust hole communicated with the inside of the motor;
The first-stage side radial bearing and the second-stage side radial bearing are static pressure or dynamic pressure air bearing;
A labyrinth seal is processed between the first-stage nozzle ring and the first-stage rotor impeller; the motor rotor is characterized in that magnetic steel corresponding to the stator winding is arranged in the middle of the motor rotor, two ends of the motor rotor are of hollow structures, a through hole is formed in the axis of the first-stage input end, the through hole is communicated with a hollow part of the motor rotor, which is close to one end of the air inlet shell, a plurality of thrust regulation exhaust holes are formed in the side wall of the hollow part, and the thrust regulation exhaust holes are uniformly distributed around the axis of the motor rotor.
2. The two-stage cantilever type axial flow expander according to claim 1, wherein a plurality of motor cooling exhaust holes are formed in the side wall of the hollow portion of the motor rotor, which is close to one end of the outer shell of the unit, the motor cooling exhaust holes are uniformly distributed around the axis of the motor rotor, and a through hole is formed in the axis of the second-stage input end and is communicated with the hollow portion of the motor rotor, which is close to one end of the outer shell of the unit.
3. The two-stage cantilever axial flow expander of claim 1, wherein the outer side of the motor housing is mounted or milled with a plurality of fins along its axial direction.
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| CN201711051562.9A CN107725113B (en) | 2017-10-31 | 2017-10-31 | Two-stage cantilever type axial flow expander |
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| CN111486103B (en) * | 2019-01-29 | 2022-06-14 | 青岛海尔智能技术研发有限公司 | Centrifugal compressor and heat pump system |
| CN114320475B (en) * | 2021-12-27 | 2023-05-02 | 北京理工大学 | Pressure energy driving type high-speed autorotation vortex expander |
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