LABYRINTH SEALS FOR COMPRESSOR

Abstract

A compressor is configured to increase the pressure of a vapor. The compressor includes one or more labyrinth seals configured to prevent leakage of the vapor. Each of the one or more labyrinth seals includes a first stepped portion and a second stepped portion. Each of the first stepped portion and the second stepped portion includes a plurality of canted teeth.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of and priority to U.S. Provisional Patent Application No. 62/476,477 filed Mar. 24, 2017, the entire disclosure of which is incorporated by reference herein.

BACKGROUND

Buildings can include heating, ventilation and air conditioning (HVAC) systems.

SUMMARY

One implementation of the present disclosure is a compressor configured to increase the pressure of a vapor. The compressor includes one or more labyrinth seals configured to prevent leakage of the vapor. Each of the one or more labyrinth seals includes a first stepped portion and a second stepped portion. Each of the first stepped portion and the second stepped portion includes a plurality of canted teeth.

Another implementation of the present disclosure is a chiller assembly. The chiller assembly includes an evaporator configured to convert a liquid refrigerant into a refrigerant vapor. The chiller assembly further includes a condenser configured to convert the refrigerant vapor into the liquid refrigerant. The chiller assembly further includes a compressor. The compressor includes one or more labyrinth seals configured to prevent leakage of the refrigerant vapor. Each of the one or more labyrinth seals includes a first stepped portion and a second stepped portion. Each of the first stepped portion and the second stepped portion includes a plurality of canted teeth. The chiller assembly further includes a suction line configured to transfer the refrigerant vapor from the evaporator to the compressor. The chiller assembly further includes a discharge line configured to transfer the refrigerant vapor from the compressor to the condenser. The chiller assembly further includes a motor assembly including a motor configured to drive the compressor. The motor assembly includes a shaft supported by one or more bearings.

Another implementation of the present disclosure is a method. The method includes providing a compressor configured to increase the pressure of a vapor. The compressor includes one or more labyrinth seals configured to prevent leakage of the vapor. Each of the one or more labyrinth seals includes a first stepped portion and a second stepped portion. Each of the first stepped portion and the second stepped portion includes a plurality of canted teeth.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing of a chiller assembly.

FIG. 2 is a drawing of an induction motor within the chiller assembly of FIG. 1.

FIG. 3 is a drawing of a conventional labyrinth seal.

FIG. 4 is a drawing of a stepped labyrinth seal with angled teeth included in the chiller assembly of FIG. 1.

DETAILED DESCRIPTION

Referring generally to the FIGURES, a chiller assembly including a compressor is shown. Also shown is a motor assembly which can be referred to herein as a motor. The chiller assembly can be configured to perform a refrigerant vapor compression cycle in an HVAC system. The compressor can include an impeller that is driven by the motor and rotates at a high speed in order to increase the pressure of a refrigerant vapor. The compressor includes one or more labyrinth seals configured to prevent leakage of the refrigerant vapor. The labyrinth seals include a first stepped portion and a second stepped portion configured to introduce a change of direction in the flow path of vapor through the labyrinth seals. The labyrinth seals also include a plurality of canted (i.e., angled) teeth configured to disrupt the flow of vapor through the labyrinth seals. The labyrinth seals are made of a high performance plastic material such as polyether ether ketone (PEEK) and/or polyamide-imide (PAI). This improved labyrinth seal design minimizes pressure loss at the impeller stage in order to drive increased capacity and performance of the compressor. In addition, the improved design delivers cost savings, increased efficiency, and improved performance of the chiller assembly as a whole. The labyrinth seal design described in the present disclosure is not limited to chiller assemblies or compressors, however, as the design can deliver improved performance in a wide variety of applications.

Referring specifically to FIG. 1, an example implementation of a chiller assembly 100 is shown. Chiller assembly 100 is shown to include a compressor 102 driven by a motor 104, a condenser 106, and an evaporator 108. A refrigerant is circulated through chiller assembly 100 in a vapor compression cycle. The refrigerant can be a low pressure refrigerant (e.g., R1233zd) with an operating pressure less than 400 kPa, for example. Chiller assembly 100 can also include a control panel 114 to control operation of the vapor compression cycle within chiller assembly 100. Control panel 114 may be connected to an electronic network in order to share a variety of data related to maintenance, analytics, etc.

Motor 104 can be powered by a variable speed drive (VSD) 110. VSD 110 receives alternating current (AC) power having a particular fixed line voltage and fixed line frequency from an AC power source (not shown) and provides power having a variable voltage and frequency to motor 104. Motor 104 can be any type of electric motor than can be powered by a VSD 110. For example, motor 104 can be a high speed induction motor. Compressor 102 is driven by motor 104 to compress a refrigerant vapor received from evaporator 108 through a suction line 112. Compressor 102 then delivers compressed refrigerant vapor to condenser 106 through a discharge line. Compressor 102 can be a centrifugal compressor, a screw compressor, a scroll compressor, a turbine compressor, or any other type of suitable compressor.

Evaporator 108 includes an internal tube bundle (not shown), a supply line 120, and a return line 122 for supplying and removing a process fluid to the internal tube bundle. The supply line 120 and the return line 122 can be in fluid communication with a component within a HVAC system (e.g., an air handler) via conduits that circulate the process fluid. The process fluid is a chilled liquid for cooling a building and can be, but is not limited to, water, ethylene glycol, calcium chloride brine, sodium chloride brine, or any other suitable liquid. Evaporator 108 is configured to lower the temperature of the process fluid as the process fluid passes through the tube bundle of evaporator 108 and exchanges heat with the refrigerant. Refrigerant vapor is formed in evaporator 108 by the refrigerant liquid delivered to the evaporator 108 exchanging heat with the process fluid and undergoing a phase change to refrigerant vapor.

Refrigerant vapor delivered by compressor 102 to condenser 106 transfers heat to a fluid. Refrigerant vapor condenses to refrigerant liquid in condenser 106 as a result of heat transfer with the fluid. The refrigerant liquid from condenser 106 flows through an expansion device and is returned to evaporator 108 to complete the refrigerant cycle of the chiller assembly 100. Condenser 106 includes a supply line 116 and a return line 118 for circulating fluid between the condenser 106 and an external component of the HVAC system (e.g., a cooling tower). Fluid supplied to the condenser 106 via return line 118 exchanges heat with the refrigerant in the condenser 106 and is removed from the condenser 106 via supply line 116 to complete the cycle. The fluid circulating through the condenser 106 can be water or any other suitable liquid.

Referring now to FIG. 2, a more detailed drawing of motor 104 and compressor 102 is shown. Motor 104 can be a high speed induction motor configured to directly drive a centrifugal compressor (i.e., compressor 102), for example. Motor 104 is shown to include a shaft 212, a rotor 214, and a stator 216. Stator 216 is supplied with AC power (e.g., from VSD 110) and includes windings that can generate a magnetic field. The magnetic field can induce an electromagnetic force that produces a torque around the axis of rotor 214. As a result, rotor 214 and shaft 212 begin to rotate in a circular motion. The shaft can be supported by one or more bearings. These components can be lubricated with oil or another type of lubricant in order to reduce friction and provide various other benefits to the system as a whole. Shaft 212 can be connected to an impeller 220 of compressor 102 via a direct drive mechanism 218. Impeller 220 can therefore be configured to rotate at a high speed in order to raise the pressure of refrigerant vapor within compressor 102. Efficiency and performance of compressor 102 can suffer if the refrigerant vapor is allowed to escape or leak out before being transferred to condenser 106 via the discharge line.

Motor 104 is shown to include three labyrinth seals and compressor 102 is shown to include two labyrinth seals. Labyrinth seal 250 can be located at the non-drive end of motor 104 while labyrinth seals 260 and 270 can be located at the drive end of motor 104. These labyrinth seals can keep lubricant sealed within appropriate locations of motor 104 in order to prevent leakage. For example, labyrinth seals 250, 260, and 270 can be located near lubricated bearings configured to support shaft 212. Labyrinth seals 280 and 290 can be installed near impeller 220 of compressor 102. Seals 280 and 290 can act as a high efficiency restriction to the flow of vapor or gas from one chamber of compressor 102 to another (e.g., inlet, impeller stage, discharge line, etc.). Seals 280 and 290 can be configured to prevent leakage of refrigerant vapor from compressor 102 in order to minimize pressure loss and maximize operating capacity. Labyrinth seals 250, 260, 270, 280, and 290 can sometimes be referred to as bearing isolators or non-contact seals. Unlike other types of seals such as lip seals, labyrinth seals 250, 260, and 270 do not make contact with or rub the surface of shaft 212 during operation of motor 104. The ability to prevent and leakage of lubricant allows various components of motor 104 (e.g., bearings, seals) to realize a longer lifetime and require less maintenance. In addition, the effectiveness of labyrinth seals 280 and 290 can drive an increase in capacity and efficiency of compressor 102. High performance labyrinth seals 250, 260, 270, 280, and 290 can also improve overall efficiency and performance of chiller assembly 100 as a whole.

Labyrinth seals 250, 260, 270, 280, and 290 can consist of multiple parts. For example, one part can remain stationary during operation of motor 104 while another part can be connected to shaft 212. In this case, the two parts (e.g., stator and rotor) can interlock as shaft 212 begins to rotate in order to form an effective seal that takes the shape of a ring. In other implementations, labyrinth seals 250, 260, 270, 280, and 290 can be ring-shaped members consisting of one main part. With the seal in place, lubricant and refrigerant vapor have a very narrow path (e.g., 50-100 microns) to pass through. In addition, labyrinth seals 250, 260, 270, 280, and 290 can include stepped portions and/or angled teeth in order to create a “maze” of turns, drops, and angles through which vapor or lubricant must pass. This turbulent flow path can form a very effective seal.

Referring now to FIG. 3, a drawing of a conventional labyrinth seal 300 is shown. Labyrinth seal 300 is shown to include a straight flow path 306 through which vapor and lubricant must pass to break the seal. Labyrinth seal 300 also includes a plurality of straight teeth 312. Given that seal 300 includes these straight teeth 312, it can sometimes be referred to as a “look-through” seal, since one could look directly through all of teeth 212 from either end (i.e., through flow path 306). The design of labyrinth seal 300 can be more effective than other seal designs (e.g., lip seal) but performance can suffer in various applications (e.g., centrifugal compression). Labyrinth seal 300 can allow a significant amount of leakage, thus leading to performance loss of various machine components (e.g., motor assembly, centrifugal compressor, bearings, etc.). Labyrinth seal 300 can be made of an aluminum material.

Referring now to FIG. 4, a drawing of a stepped labyrinth seal 400 with angled teeth is shown. Labyrinth seal 400 can be identical or nearly identical to labyrinth seals 250, 260, 270, 280, and 290 described above. Labyrinth seal 400 can achieve greater performance when compared to designs such as described above with respect to labyrinth seal 300. Labyrinth seal 400 is shown to include a first stepped portion 410 that includes a plurality of canted teeth 412. Labyrinth seal 400 is also shown to include second stepped portion 420 that includes a plurality of canted teeth 422. A flow path 406 that provides significant resistance to the flow of liquid (e.g., oil, lubricant, process fluid) and gas (e.g., refrigerant vapor) is also shown. In addition, the transition from stepped portion 410 to stepped portion 420 (or vice versa) introduces a change of direction to flow path 406. Unlike seal 300, labyrinth seal 400 is not a “look-through” seal since one could not look all the way through teeth 412 and 422 due to stepped portions 410 and 420.

Canted teeth 412 and 422 are fabricated with an angular deviation from a vertical or horizontal plane. These tilted teeth increase the resistance to the flow of lubricant or vapor through flow path 406 when compared to other seal designs such as the straight teeth 312 shown as part of labyrinth seal 300 in FIG. 3. Canted teeth 412 and 422 can introduce significant flow disruption that helps prevent leakage of lubricant and vapor. Stepped portion 420 is shown to be elevated above stepped portion 410. As a result, vapor or lubricant flowing through path 406 are forced to undergo a perpendicular change in direction. This change in direction caused by stepped portions 410 and 420 also increases resistance to flow. In addition, the orientation of canted teeth 412 and 422 allows the teeth to remain more flexible when compared to straight teeth 312. This flexibility can allow seal 400 to preclude wear when the rotating component (e.g., shaft 212, impeller 220) comes in contact with the seal. Alternatively, seal 300 can be damaged and worn when in contact with a rotating component.

Labyrinth seal 400 can be made of a material with a high PV rating and elastic properties. The PV rating can be found by multiplying the maximum pressure experienced by the seal (e.g., seal 400) by surface velocity of the shaft or impeller (e.g., shaft 212, impeller 220). For example, the PV rating can be expressed by the equation PV=Pressure×Velocity=(psi)×(fpm). The high PV rating of labyrinth seal 400 signifies a high resistance to wear. This resistance to wear can improve the performance of labyrinth seal 400 as well as allow the seal to realize a longer lifetime and require less maintenance. Labyrinth seal 400 can be made of a high performance plastic material such as polyether ether ketone (PEEK), polyamide-imide (PAI), or a combination thereof. Labyrinth seal 400 can also be made of a variety of other plastics or other materials (e.g., polymers). As a result, labyrinth seal 400 can withstand intermittent contact with rotating element during operation of motor 104. This durability allows seal 400 to be placed closer (i.e., less clearance) to shaft 212 or impeller 220 in order to form a more effective seal when compared to aluminum seals. The use of aluminum labyrinth seals often coincides with a need to anodize (e.g., coat) components such as impeller 220 in order to increase resistance to wear. The use of a plastic labyrinth seal such as seal 400 can drive significant cost savings (e.g., for chiller assembly 100) since anodized surfaces may not be necessary. The design principles described above with respect to labyrinth seal 400 can be implemented in a variety of different applications and is not limited to compressors, motor assemblies, or chiller assemblies, for example.

The construction and arrangement of the systems and methods as shown in the various exemplary embodiments are illustrative only. Although only example embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, the position of elements can be reversed or otherwise varied and the nature or number of discrete elements or positions can be altered or varied. Accordingly, such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps can be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present disclosure.

Claims

1. A compressor configured to increase pressure of a vapor comprising:

one or more labyrinth seals configured to prevent leakage of the vapor, wherein each of the one or more labyrinth seals is a ring-shaped member and includes a first stepped portion and a second stepped portion, each of the first stepped portion and the second stepped portion including a plurality of canted teeth.

2. The compressor of claim 1, wherein the one or more labyrinth seals are made of a high performance plastic material.

3. The compressor of claim 2, wherein the high performance plastic material is polyether ether ketone (PEEK).

4. The compressor of claim 2, wherein the high performance plastic material is polyamide-imide (PAI).

5. The compressor of claim 1, wherein the second stepped portion is elevated from the first stepped portion.

6. The compressor of claim 1, wherein the compressor operates as part of a chiller assembly, the chiller assembly including an evaporator configured to convert a liquid refrigerant into the vapor and a condenser configured to convert the vapor into the liquid refrigerant.

7. The compressor of claim 6, wherein the chiller assembly further includes a suction line configured to transfer the vapor from the evaporator to the compressor and a discharge line configured to transfer the vapor from the compressor to the condenser.

8. The compressor of claim 7, wherein the compressor further includes an impeller, the impeller driven by a motor and configured to rotate at a high speed in order to increase the pressure of the vapor.

9. The compressor of claim 8, wherein the chiller assembly further includes a variable speed drive (VSD) configured to provide the AC power to the motor.

10. The compressor of claim 9, wherein the refrigerant is a low pressure refrigerant having an operating pressure of less than 400 kPa.

11. The compressor of claim 10, wherein the low pressure refrigerant is R1233zd.

12. The compressor of claim 1, wherein a flow path through the one or more labyrinth seals ranges from 50-100 microns.

13. The compressor of claim 12, wherein the flow path includes a perpendicular change of direction resulting from the first stepped portion and the second stepped portion.

14. The compressor of claim 13, wherein the plurality of canted teeth increase a level of resistance associated with the flow path.

15. The compressor of claim 14, wherein the plurality of canted teeth include an angular deviation from a vertical plane.

16. A chiller assembly comprising:

an evaporator configured to convert a liquid refrigerant into a refrigerant vapor;

a condenser configured to convert the refrigerant vapor into the liquid refrigerant;

a compressor including one or more labyrinth seals configured to prevent leakage of the refrigerant vapor, wherein each of the one or more labyrinth seals includes a first stepped portion and a second stepped portion, each of the first stepped portion and the second stepped portion including a plurality of canted teeth;

a suction line configured to transfer the refrigerant vapor from the evaporator to the compressor;

a discharge line configured to transfer the refrigerant vapor from the compressor to the condenser; and

a motor assembly including a motor configured to drive the compressor, the motor assembly including a shaft supported by one or more bearings.

17. The chiller assembly claim 16, wherein the one or more bearings are lubricated with a lubricant.

18. The chiller assembly of claim 17, wherein the motor assembly further includes one or more bearing labyrinth seals configured to prevent leakage of the lubricant.

19. The chiller assembly of claim 18, wherein each of the one or more bearing labyrinth seals includes a first stepped portion and a second stepped portion, each of the first stepped portion and the second stepped portion including a plurality of canted teeth.

20. A method comprising:

providing a compressor configured to increase pressure of a vapor, the compressor comprising:

one or more labyrinth seals configured to prevent leakage of the vapor, wherein each of the one or more labyrinth seals is a ring-shaped member and includes a first stepped portion and a second stepped portion, each of the first stepped portion and the second stepped portion including a plurality of canted teeth.