Patent Application
20220074415
The disclosure relates generally to compressor systems and, more specifically, to a direct drive refrigerant screw compressor using refrigerant lubrication of one or more components thereof.
Refrigeration systems are utilized in many applications to condition an environment. The cooling or heating load of the environment may vary with ambient conditions, occupancy level, other changes in sensible and latent load demands, and with temperature and/or humidity changes.
Refrigeration systems typically include a compressor to deliver compressed refrigerant to a condenser. From the condenser, the refrigerant travels to an expansion valve and then to an evaporator. From the evaporator, the refrigerant returns to the compressor to be compressed.
A direct drive screw compressor in an HVAC chiller application has a driving (male) rotor and a driven (female) rotor. An electric motor drives the driving rotor to rotate. The driving rotor then drives the driven rotor by way of meshing. The meshing process requires direct contact of the rotors at contact locations. Lubrication is necessary to protect both rotors and decrease the friction during operation.
In addition, the rotors in a screw compressor in HVAC chiller applications are supported by rolling element bearings. These bearings may be lubricated using oil because of a high viscosity requirement of bearing lubricant. After passing through the bearings, oil is mixed with refrigerant in the compression process to be carried out of the compressor.
Disclosed is a direct-drive refrigerant screw compressor, comprising: a housing; a compression chamber in the housing; a pair of rotors, each rotor of the pair of rotors being rotationally disposed in the compression chamber and including an outer surface with a screw-geared profile; wherein, for each rotor, the compressor includes: a plurality of bearing packs disposed within a respective plurality of bearing chambers; a working fluid disposed within each of the plurality of bearing chambers, the working fluid providing oil-free lubrication to the plurality of bearing packs; a plurality of bearing lubrication ports extending through the housing and into each of the plurality of bearing chambers, and configured for injecting the working fluid into each of the plurality of bearing chambers when the compressor is running.
In addition to one or more of the above features, or as an alternate, for each rotor: the plurality of bearing lubrication ports include a respective plurality flow control orifices.
In addition to one or more of the above features, or as an alternate, for each rotor: the plurality of bearing chambers include a forward bearing chamber and an aft bearing chamber; and the plurality of bearing lubrication ports include a forward bearing lubrication port and an aft bearing lubrication port configured for directing the working fluid into the respective plurality of bearing chambers.
In addition to one or more of the above features, or as an alternate, for each rotor: the compressor includes a lubricant drain port for draining the working fluid from the plurality of bearing chambers when the compressor is running.
In addition to one or more of the above features, or as an alternate, for each rotor: the lubricant drain port extends into the aft bearing chamber and is fluidly connected to the forward bearing chamber through the compression chamber.
Further disclosed is a refrigerant system comprising: a condenser; and a direct-drive refrigerant screw compressor having one or more of the above disclosed features; and a condenser conduit fluidly connecting condenser to the plurality of bearing lubrication ports.
In addition to one or more of the above features, or as an alternate, the condenser conduit includes a forward branch and an aft branch for injecting in parallel the working fluid to each forward bearing chamber and each aft bearing chamber in the compressor; and each branch includes a plurality of sub-branches for injecting in parallel the working fluid to the bearing chambers on each branch.
In addition to one or more of the above features, or as an alternate, the system further comprises an evaporator; and an evaporator conduit fluidly connected between the evaporator and the lubricant drain port.
Further disclosed is a method of directing working fluid in a direct-drive refrigerant screw compressor, wherein for each rotor of a pair of rotors in the compressor, the method comprises: receiving working fluid at a plurality of bearing lubrication ports in a housing of the compressor, wherein the working fluid is oil-free; and directing the working fluid from the plurality of bearing lubrication ports to a plurality of bearing chambers; and when the compressor is running, lubricating a plurality of bearing packs in the respective plurality of bearing chambers with the working fluid.
In addition to one or more of the above features, or as an alternate, the method further comprises: controlling flow through the plurality of bearing lubrication ports with a respective plurality of flow control orifices.
In addition to one or more of the above features, or as an alternate, the method further comprises: injecting the working fluid into a forward bearing chamber from a forward bearing lubrication port and an aft bearing chamber from an aft bearing lubrication port.
In addition to one or more of the above features, or as an alternate, the method further comprises for each rotor: draining the working fluid through a lubricant drain port from the plurality of bearing chambers when the compressor is running.
In addition to one or more of the above features, or as an alternate, for each rotor, the forward and aft bearing chambers are fluidly connected through the compression chamber, and the lubricant drain port is disposed in the aft bearing chamber; and the method comprises: draining the working fluid from each bearing chamber through the lubricant drain port in the aft bearing compartment.
In addition to one or more of the above features, or as an alternate, the method further comprises: transporting the working fluid from a condenser of a refrigeration system to the plurality of bearing lubrication ports.
In addition to one or more of the above features, or as an alternate, the method further comprises: transporting the working fluid in the condenser conduit so that the working fluid is injected in parallel to each forward bearing chamber and each aft bearing chamber in the compressor.
In addition to one or more of the above features, or as an alternate, the method further comprises for each rotor: transporting the working fluid from the lubrication drain port to an evaporator in the refrigeration system.
The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:
A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.
Described herein are systems and methods for lubricating components of a compressor in a refrigeration system.
The compressor 30 may be a screw compressor that includes suction bearings 35, discharge bearings 40, and a set of rotors 45 therebetween. Both sets of bearings 35, 40 and the rotors 45 require some form of lubrication. Lubricating oil is provided by an oil separator 50. The oil separator 50 transfers oil to an oil filter 55. The oil filter 55 transfers oil a first portion of oil 60 to one orifice 71, e.g, in the compressor housing, fluidly connected to the suction bearings 35. A second portion of oil 65 is distributed in parallel to one orifice 70, e.g., in the compressor housing, fluidly connected to the rotors 45 and another orifice 75, e.g., in the compressor housing, fluidly connected to the discharged bearings 40. The oil then mixes with the working fluid in the compressor 30.
Output from the compressor 30 is directed to the oil separator 50. The oil separator 50 separates the output from the compressor into a first portion 80 that is the working fluid directed the condenser 15. The second portion 85 is the lubricant directed to the filter 55. Unless otherwise indicated herein, for each embodiment all flows between the system components that are separately referred to are fluidly transferred in respective conduit lines. It is to be appreciated that fluid branches that are branched upstream or downstream of the orifices 70, 75 in the housing of the compressor 30 may be branched in conduit exterior to the housing of the compressor 30.
Viscosity of oil lubricant may be reduced when mixed with the working fluid. Both bearing load carrying capacity and oil sealing characteristics are dependent upon the oil viscosity. As such, due to lower viscosity, moving components, such as bearings and rotors, in some systems may experience increased wear during operation. In addition, separating lubricating oil from refrigerant requires the use and maintenance of additional equipment such as the oil separator and related filter. In addition, because the oil separation process cannot completely remove the oil from refrigerant, excessive oil may decrease heat transfer efficiency in the system and lower the overall system capacity. Oil may be saturated with refrigerant in the separator. The separation process is often unable to adequately lower the refrigerant content in the oil.
In view of the above challenges
The condenser feeds first portion 116 of a working fluid to the expansion valve 112 and, in parallel, a second portion 120 of the working fluid 120 to the compressor 115. The working fluid consists of refrigerant form a condenser conduit 125 to the compressor 115 for providing lubrication to components of the compressor 115 as described below.
The second portion 120 of the working fluid is distributed in parallel to a first branch 121 and a second branch 122. The first branch 121 is distributed in parallel to a third branch 123 and a fourth branch 124. The third branch 123 delivers the working fluid through one or more orifices 126, e.g. in the compressor housing 130, to the suction side bearing pack 190a. The fourth branch 124 delivers the working fluid through another one or more orifices 127, e.g. in the compressor housing 130, to the rotors 150. The second branch 122 delivers the working fluid to a further one or more orifices 128, e.g. in the compressor housing 130, to the branch side bearing pack 190b.
From the suction side bearing pack 190a, the working fluid flows directly into the rotors 150 with the working fluid from the evaporator 114. This may occur within the compressor housing 130. From the discharge side bearing pack 190b the working fluid flows to the evaporator 114 to mix with fluid therein and then be redirected to the rotors 150 of the compressor 115. This may occur by the working fluid exiting the compressor housing 130 from the discharged side bearings 190b and being directed thereafter to the evaporator 114. Unless otherwise indicated herein, for each embodiment all flows between the system components that are separately referred to are fluidly transferred in respective conduit lines. It is to be appreciated that fluid branches that are branched upstream or downstream of the orifices 126, 127, 128 in the compressor housing 130 may be branched in conduit exterior to the compressor housing 130.
The features of the compressor are illustrated more specifically, for example, in
The compressor 115 includes the plurality of rotors generally referred to as 150, including the first rotor 150a and the second rotor 150b, rotationally disposed in the compression chamber 140. Each rotor 150 includes an outer surface 160 with a screw-geared profile, for example, having an alternating plurality of peaks 160a and plurality of troughs 160b, for example, in cross sectional view. The plurality of rotors 150 intermesh and form compression volumes within the compression chamber 140. The first rotor 150a is a driven rotor and the second rotor 150b is a drive rotor, driven by a motor 180.
For each rotor 150, the compressor 115 includes the plurality of bearing packs generally referred to as 190 including the forward bearing pack generally referred to as 190a and the aft bearing pack generally referred to as 190b. For each rotor 150, the plurality of bearing packs 190 may disposed within a respective plurality of bearing chambers generally referred to as 200. The bearing chambers 200 may be structural portions of the housing 130 in or proximate the compression chamber 140 configured to securely position the respective bearing packs 190. The bearing chambers 200 may including a forward bearing chamber generally referred to as 200a and an aft bearing chamber generally referred to as 200b. The bearing chambers 200 may be fluidly connected with each other through the compression chamber 140.
Turning now to
In
Turning now to
The passage 260 may be an internal passage in the one rotor 150. The passage 260 may be fluidly connected between an axial aft port 265 in the one rotor 150 and the outer surface 160 of the one rotor 150. The aft port 265 may be in the respective aft bearing chamber 200b, though this placement is not intended to be limiting.
The passage 260 may include an axial segment 270 forming a blind hole in the one rotor 150 and a radial segment generally referred to as 280 fluidly connected between the axial segment 270 and a surface port generally referred to as 290 on the outer surface 160 of the one rotor 150. In one embodiment, the passage 260 may include a plurality of the radial segments 280 fluidly connected to a respective plurality of the surface ports 290 on the outer surface 160 of the one rotor 150. This configuration may provide a greater distribution of the fluid 120 about each rotor 150 as compared with, for example, a single fluid 120 port.
In one embodiment, the plurality of the surface ports 290 may be staggered at regular intervals along the outer surface 160, for example, at or proximate the plurality of alternating peaks 160a or troughs 160b. This configuration may provide an even distribution of fluid 120 around the outer surface 160 of the each rotor 150. In one embodiment the plurality of the radial segments 280 may each include a plurality of opposing radial portions 280a, 280b extending to a respective plurality of the radial ports 290a, 290b on the outer surface 160 of the one rotor 150. This configuration may provide an ability to quickly distribute fluid 120 around the outer surface 160 of the rotors 150.
Turning to
Turning to
Thus, in the above disclosed embodiments, the working fluid 120 is drawn from a chiller condenser and used to provide lubrication to the compressor and more specifically to the screw rotors. The liquid can be injected direct from port(s) on the housing close to the rotor meshing locations or through a passage inside the driving rotor. The liquid flow can be adjusted by using flow restriction devices, such as a flow control orifice. The embodiments enable the utilization of pure refrigerant as the working fluid 120 in the components of the system 100, including the condenser 110, evaporator 114, etc.
Turning now to
In addition, a suction side (upstream) lubrication port 300a includes a suction side (upstream) flow control orifice 301a (which may be the same as orifice 126 in
The condenser conduit 125 fluidly connects the condenser 110 to the plurality of bearing lubrication ports 300. From this configuration, the plurality of bearing lubrication ports 300 are configured for injecting the fluid 120 into each of the plurality of bearing chambers 200 when the compressor 115 is running, to thereby provide lubrication to the plurality of bearing packs 190. In one embodiment the plurality of bearing lubrication ports 300 include a respective plurality flow control orifices 230 to reduce a flow volume or rate from the condenser 110 as may be needed.
In one embodiment, the condenser conduit 125 includes a forward branch 310a and an aft branch 310b for injecting in parallel the fluid 125 to each forward bearing chamber 200a and each aft bearing chamber 200b in the compressor. Each branch 310a, 310b includes a plurality of sub-branches generally referred to as 320 for injecting in parallel the fluid to the bearing chambers 200 on each branch 310a, 310b. This configuration enables the condenser 110 to feed the fluid 120 to the compressor 115 from the single condenser conduit 125.
As further illustrated in
As illustrated in
According to an embodiment, for each rotor 150, the method includes block 730 of draining the fluid 120 through the lubricant drain port 360 from the plurality of bearing chambers 200 when the compressor 115 is running According to an embodiment, for each rotor 150 block 730 further includes draining the fluid 120 from the plurality of chambers 20 through the aft bearing chamber 200, into the evaporator conduit 370, and to the evaporator 114 in the refrigerant system 100.
With the above disclosed embodiments, for example in
With the above disclosed embodiments, oil separation equipment on a chiller is no longer necessary. This configuration reduces the complexity of the chiller system. The chiller cost will be therefore reduced. The chiller heat transfer efficiency will therefore increase.
Accordingly, as indicated above, there are two kinds of fluids in a typical system: oil and a working fluid. Oil is typically used for lubricating bearings and rotors and for sealing. The working fluid, such as refrigerant, is typically used to transmit heat. According to the disclosed embodiments, the working fluid, instead of oil, is used for lubricating bearings and rotors.
The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.
While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.
This application claims the benefit of U.S. Application No. 62/850,328, filed on May 20, 2019, which is incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2020/033675 | 5/20/2020 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62850328 | May 2019 | US |
