Patent Description:
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.

<CIT> discloses a screw refrigerating apparatus comprising a refrigerant circulating passage including a screw compressor, a condenser, an expansion valve, and an evaporator, which is constituted such that a bypass flow passage branching at a part of the refrigerant circulating passage between the condenser and the expansion valve, routing through throttle means, and communicating with a rotor cavity within the screw compressor, is provided.

<CIT> discloses a vapor compression system comprising: a compressor having a suction port and a discharge port; a heat rejection heat exchanger coupled to the discharge port to receive compressed refrigerant; a heat absorption heat exchanger; a first lubricant flowpath from the heat rejection heat exchanger to the compressor; a second lubricant flowpath from the heat absorption heat exchanger to the compressor; at least one lubricant pump; and a controller configured to control lubricant flow along the first lubricant flowpath and the second lubricant flowpath based on a sensed fluctuation.

According to a first aspect of the invention a direct-drive refrigerant screw compressor is provided, 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; and 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, wherein the working fluid is refrigerant; characterized in that: for each rotor, the compressor includes: 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, wherein for each rotor: the plurality of bearing lubrication ports include a respective plurality flow control orifices to reduce a flow volume or rate from a condenser, wherein the respective plurality flow control orifices are in the compressor housing; 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.

Optionally, 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.

Optionally, 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.

According to another aspect of the invention, a refrigerant system is provided, comprising: a condenser; and a direct-drive refrigerant screw compressor according to the first aspect and optionally including any of the other features as described above; and a condenser conduit fluidly connecting the condenser to the plurality of bearing lubrication ports.

Optionally, 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.

Optionally, the system further comprises an evaporator; and an evaporator conduit fluidly connected between the evaporator and the lubricant drain port.

According to another aspect of the invention, a method of directing working fluid in a direct-drive refrigerant screw compressor is provided, 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 refrigerant; 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; characterized in that: the method comprises controlling flow through the plurality of bearing lubrication ports with a respective plurality of flow control orifices that reduce a flow volume or rate from a condenser, wherein the respective plurality flow control orifices are in the compressor housing, and wherein for each rotor, 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.

Optionally, 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.

Optionally, 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.

Optionally, the method further comprises: transporting the working fluid from a condenser of a refrigeration system to the plurality of bearing lubrication ports.

Optionally, 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.

Optionally, the method further comprises for each rotor: transporting the working fluid from the lubricant drain port to an evaporator in the refrigeration system.

Described herein are systems and methods for lubricating components of a compressor in a refrigeration system. <FIG> illustrates a refrigeration system <NUM> that is an oil lubricated system. The system <NUM> includes a condenser <NUM> that receives a high pressure gaseous form of the working fluid, ejects heat from the working fluid, for example to the environment, and outputs a high pressure liquid form of the working fluid. Downstream of the condenser <NUM> is an expansion valve <NUM> that receives the high pressure liquid form of the working fluid and outputs a low pressure liquid form of the working fluid. Downstream of the expansion valve <NUM> is an evaporator <NUM> that receives the low pressure liquid form of the working fluid, transfers heat to the working fluid, thereby conditioning warm air, and outputs a low pressure gaseous form of the working fluid. Downstream of the evaporator <NUM> is a compressor <NUM> that receives the low pressure gaseous form of the working fluid and outputs a high pressure gaseous form of the working fluid.

The compressor <NUM> may be a screw compressor that includes suction bearings <NUM>, discharge bearings <NUM>, and a set of rotors <NUM> therebetween. Both sets of bearings <NUM>, <NUM> and the rotors <NUM> require some form of lubrication. Lubricating oil is provided by an oil separator <NUM>. The oil separator <NUM> transfers oil to an oil filter <NUM>. The oil filter <NUM> transfers oil a first portion of oil <NUM> to one orifice <NUM>, e. g, in the compressor housing, fluidly connected to the suction bearings <NUM>. A second portion of oil <NUM> is distributed in parallel to one orifice <NUM>, e.g., in the compressor housing, fluidly connected to the rotors <NUM> and another orifice <NUM>, e.g., in the compressor housing, fluidly connected to the discharged bearings <NUM>. The oil then mixes with the working fluid in the compressor <NUM>.

Output from the compressor <NUM> is directed to the oil separator <NUM>. The oil separator <NUM> separates the output from the compressor into a first portion <NUM> that is the working fluid directed the condenser <NUM>. The second portion <NUM> is the lubricant directed to the filter <NUM>. 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 <NUM>, <NUM> in the housing of the compressor <NUM> may be branched in conduit exterior to the housing of the compressor <NUM>.

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 <FIG> disclose embodiments and examples in which an oil separator and oil filter may be avoided. More specifically, turning to <FIG>, disclosed is a refrigerant system <NUM> (a chiller) applicable to each of the embodiments and examples disclosed herein. The system <NUM> includes a condenser <NUM>, an expansion valve <NUM>, an evaporator <NUM>, and a dual rotor refrigerant screw compressor <NUM> (compressor <NUM>), which is a direct drive compressor. The compressor <NUM> includes two screw rotors <NUM>. The rotors <NUM> are configured in the compressor <NUM> with a suction side 140a and discharge side 140b (illustrated schematically in <FIG>). The compressor <NUM> includes bearing packs <NUM> including a suction side bearing pack 190a and a discharge side bearing pack 190b. The suction side bearing pack 190a may be referred to herein as a forward bearing pack and the discharge side bearing pack 190b may be referred to herein as an aft bearing pack.

The condenser feeds first portion <NUM> of a working fluid to the expansion valve <NUM> and, in parallel, a second portion <NUM> of the working fluid <NUM> to the compressor <NUM>. The working fluid consists of refrigerant form a condenser conduit <NUM> to the compressor <NUM> for providing lubrication to components of the compressor <NUM> as described below.

The second portion <NUM> of the working fluid is distributed in parallel to a first branch <NUM> and a second branch <NUM>. The first branch <NUM> is distributed in parallel to a third branch <NUM> and a fourth branch <NUM>. The third branch <NUM> delivers the working fluid through one or more orifices <NUM>, e.g. in the compressor housing <NUM>, to the suction side bearing pack 190a. The fourth branch <NUM> delivers the working fluid through another one or more orifices <NUM>, e.g. in the compressor housing <NUM>, to the rotors <NUM>. The second branch <NUM> delivers the working fluid to a further one or more orifices <NUM>, e.g. in the compressor housing <NUM>, to the branch side bearing pack 190b.

From the suction side bearing pack 190a, the working fluid flows directly into the rotors <NUM> with the working fluid from the evaporator <NUM>. This may occur within the compressor housing <NUM>. From the discharge side bearing pack 190b the working fluid flows to the evaporator <NUM> to mix with fluid therein and then be redirected to the rotors <NUM> of the compressor <NUM>. This may occur by the working fluid exiting the compressor housing <NUM> from the discharged side bearings 190b and being directed thereafter to the evaporator <NUM>. 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 <NUM>, <NUM>, <NUM> in the compressor housing <NUM> may be branched in conduit exterior to the compressor housing <NUM>.

The features of the compressor are illustrated more specifically, for example, in <FIG>. Turning now to <FIG>, the compressor <NUM> includes the housing <NUM>. A compression chamber <NUM> is disposed in the housing <NUM>. The compression chamber <NUM> has a forward end 140a and an aft end 140b which are respective suction and discharge sides of the compression chamber <NUM>. For simplicity, inlet and outlet ports in the housing <NUM> for fluidly communicating working fluid <NUM> in the refrigeration system <NUM> are not illustrated in <FIG>.

The compressor <NUM> includes the plurality of rotors generally referred to as <NUM>, including the first rotor 150a and the second rotor 150b, rotationally disposed in the compression chamber <NUM>. Each rotor <NUM> includes an outer surface <NUM> 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 <NUM> intermesh and form compression volumes within the compression chamber <NUM>. The first rotor 150a is a driven rotor and the second rotor 150b is a drive rotor, driven by a motor <NUM>.

For each rotor <NUM>, the compressor <NUM> includes the plurality of bearing packs generally referred to as <NUM> including the forward bearing pack generally referred to as 190a and the aft bearing pack generally referred to as 190b. For each rotor <NUM>, the plurality of bearing packs <NUM> may disposed within a respective plurality of bearing chambers generally referred to as <NUM>. The bearing chambers <NUM> may be structural portions of the housing <NUM> in or proximate the compression chamber <NUM> configured to securely position the respective bearing packs <NUM>. The bearing chambers <NUM> may including a forward bearing chamber generally referred to as 200a and an aft bearing chamber generally referred to as 200b. The bearing chambers <NUM> may be fluidly connected with each other through the compression chamber <NUM>.

Turning now to <FIG>, an exemplary refrigeration system <NUM> is illustrated. The example of <FIG> includes all of the features illustrated in the system <NUM> illustrated in <FIG>. In <FIG>, the fluid <NUM> is disposed within the compression chamber <NUM>. A first port <NUM> extends through the housing <NUM> for directing fluid toward the compression chamber <NUM>. The first port <NUM> is connected by the condenser conduit <NUM> to the condenser <NUM>. The first port <NUM> includes a flow control orifice <NUM>. This may be used to reduce a flow volume or rate from the condenser <NUM> as may be needed.

In <FIG>, the first port <NUM> extends directly into the compression chamber <NUM>. Within the compression chamber <NUM>, the first port <NUM> delivers working fluid <NUM> between the two rotors <NUM> so that the working fluid <NUM> flows to meshing points between the two rotors <NUM>. In one example, the first port <NUM> is proximate one rotor <NUM> (the second rotor 150b) of the compressor <NUM> and distal the other rotor <NUM> (the first rotor 150a). Identifying the one rotor <NUM> as the second rotor 150b and the other rotor <NUM> as the first rotor 150a in <FIG> is for example only. Rotation of the rotors <NUM> distributes the fluid <NUM> about the rotors <NUM>.

Turning now to <FIG>, an exemplary refrigeration system <NUM> is illustrated. The example of <FIG> includes all of the features illustrated in the system <NUM> illustrated in <FIG>. In <FIG>, the fluid <NUM> is disposed within the compression chamber <NUM>. A first port <NUM>, configured differently than the first port <NUM> in the example of <FIG>, extends through the housing <NUM>. In <FIG>, the first port <NUM> fluidly connects with a passage <NUM> within one rotor <NUM> (the first rotor 150a) for directing fluid toward the compression chamber <NUM>. Identifying the one rotor <NUM> as the first rotor 150a, and thus the other rotor <NUM> as the second rotor 150a, in <FIG> is for example only. The first port <NUM> is connected by the condenser conduit <NUM> to the condenser <NUM>. According to an example, the passage <NUM> includes a flow control orifice <NUM>, which may be the same as the above introduced flow control orifice <NUM>. This may be used to reduce a flow volume or rate from the condenser <NUM> as may be needed.

The passage <NUM> may be an internal passage in the one rotor <NUM>. The passage <NUM> may be fluidly connected between an axial aft port <NUM> in the one rotor <NUM> and the outer surface <NUM> of the one rotor <NUM>. The aft port <NUM> may be in the respective aft bearing chamber 200b, though this placement is not intended to be limiting.

The passage <NUM> may include an axial segment <NUM> forming a blind hole in the one rotor <NUM> and a radial segment generally referred to as <NUM> fluidly connected between the axial segment <NUM> and a surface port generally referred to as <NUM> on the outer surface <NUM> of the one rotor <NUM>. In one example, the passage <NUM> may include a plurality of the radial segments <NUM> fluidly connected to a respective plurality of the surface ports <NUM> on the outer surface <NUM> of the one rotor <NUM>. This configuration may provide a greater distribution of the fluid <NUM> about each rotor <NUM> as compared with, for example, a single fluid <NUM> port.

In one example, the plurality of the surface ports <NUM> may be staggered at regular intervals along the outer surface <NUM>, for example, at or proximate the plurality of alternating peaks 160a or troughs 160b. This configuration may provide an even distribution of fluid <NUM> around the outer surface <NUM> of the each rotor <NUM>. In one example the plurality of the radial segments <NUM> 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 <NUM> of the one rotor <NUM>. This configuration may provide an ability to quickly distribute fluid <NUM> around the outer surface <NUM> of the rotors <NUM>.

Turning to <FIG>, an exemplary method is disclosed of directing fluid <NUM> in the compressor <NUM> for the embodiment illustrated in <FIG>. The method includes block <NUM> of receiving the fluid <NUM> at the first port <NUM> of the housing <NUM>. In an example, block <NUM> further includes controlling flow in the first port <NUM> through a flow control orifice <NUM> (which may be the same as orifice <NUM> in <FIG>). The method further includes block <NUM> of directing the fluid <NUM> in the compressor <NUM>, from the first port <NUM>, to the compression chamber <NUM>. According to an example, block <NUM> further includes injecting the fluid <NUM> from the first port <NUM> directly into the compression chamber <NUM> proximate one rotor <NUM> and distal the other rotor <NUM>. At block <NUM> the compressor is activated to distribute the fluid about the rotors <NUM>.

Turning to <FIG>, an exemplary method is disclosed of directing fluid <NUM> in the compressor <NUM> for the example illustrated in <FIG>. Similar to the exemplary method in <FIG>, the exemplary method of <FIG> includes block <NUM> of receiving the fluid <NUM> at the first port <NUM> of the housing <NUM>. The method of <FIG> includes block <NUM> of directing the fluid <NUM>, from the first port <NUM>, to the compression chamber <NUM>. In an embodiment, block <NUM> further includes controlling flow in the passage <NUM> through a flow control orifice <NUM>. In an example, block <NUM> further includes injecting the fluid <NUM> through the first port <NUM>, through a passage <NUM> in one rotor <NUM>, and into the compression chamber <NUM>. Then, at block <NUM> the compressor is activated to distribute the fluid about the rotors <NUM>.

Thus, in the above disclosed examples, the working fluid <NUM> 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 examples enable the utilization of pure refrigerant as the working fluid <NUM> in the components of the system <NUM>, including the condenser <NUM>, evaporator <NUM>, etc..

Turning now to <FIG> an embodiment of a refrigerant system <NUM> is illustrated. The embodiment of <FIG> includes all of the features illustrated in the system <NUM> illustrated in <FIG>. In <FIG>, the fluid <NUM> is disposed within each of the plurality of bearing chambers <NUM> for providing lubrication to the plurality of bearing packs <NUM>, thus providing pure refrigerant lubricated (PRL) bearings. A plurality of bearing lubrication ports generally referred to as <NUM> extend through the housing <NUM> and into each of the plurality of bearing chambers <NUM>.

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 <NUM> in <FIG>). A discharge side (downstream) lubrication port 300b includes a discharge side (downstream) flow control orifice 301b (which may be the same as orifice <NUM> in <FIG>).

The condenser conduit <NUM> fluidly connects the condenser <NUM> to the plurality of bearing lubrication ports <NUM>. From this configuration, the plurality of bearing lubrication ports <NUM> are configured for injecting the fluid <NUM> into each of the plurality of bearing chambers <NUM> when the compressor <NUM> is running, to thereby provide lubrication to the plurality of bearing packs <NUM>. In one embodiment the plurality of bearing lubrication ports <NUM> include a respective plurality flow control orifices <NUM> to reduce a flow volume or rate from the condenser <NUM> as may be needed.

In one embodiment, the condenser conduit <NUM> includes a forward branch 310a and an aft branch 310b for injecting in parallel the fluid <NUM> 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 <NUM> for injecting in parallel the fluid to the bearing chambers <NUM> on each branch 310a, 310b. This configuration enables the condenser <NUM> to feed the fluid <NUM> to the compressor <NUM> from the single condenser conduit <NUM>.

As further illustrated in <FIG>, for each rotor <NUM> the compressor <NUM> includes a lubricant drain port generally referred to as <NUM> fluidly connected to the evaporator by an evaporator conduit <NUM>. The lubricant drain port <NUM> is for draining the fluid <NUM> from the plurality of bearing chambers <NUM> of the respective rotor <NUM> when the compressor <NUM> is running. In one embodiment, each lubricant drain port <NUM> extends into the respective aft bearing chamber 200b and is fluidly connected to the respective forward bearing chamber 200a through the respective aft bearing chamber 200b.

As illustrated in <FIG>, a further method is disclosed of directing fluid <NUM> in the compressor <NUM> in the refrigerant system <NUM>. The method includes block <NUM> of receiving the fluid <NUM> from the compressor <NUM> in the refrigerant system <NUM>, through a condenser conduit <NUM>, at the plurality of bearing lubrication ports <NUM>. The method includes block <NUM> of directing the fluid <NUM> through the plurality of bearing lubrication ports <NUM> to the plurality of bearing chambers <NUM>. From this configuration the fluid <NUM> is injected, when the compressor <NUM> is running, to the plurality of bearing packs <NUM> in the respective plurality of bearing chambers <NUM>. According to an embodiment, box <NUM> may further include controlling flow through the plurality of bearing lubrication ports <NUM> with a respective plurality of flow control orifices <NUM>. Then, at block <NUM> the compressor is activated to distribute the fluid about the rotors <NUM>. That is, the fluid <NUM> is inject to one side of the bearing packs <NUM> and is flow through the bearing packs <NUM> to lubricate each of the bearing packs <NUM>.

According to an embodiment, for each rotor <NUM>, the method includes block <NUM> of draining the fluid <NUM> through the lubricant drain port <NUM> from the plurality of bearing chambers <NUM> when the compressor <NUM> is running. According to an embodiment, for each rotor <NUM> block <NUM> further includes draining the fluid <NUM> from the plurality of chambers <NUM> through the aft bearing chamber <NUM>, into the evaporator conduit <NUM>, and to the evaporator <NUM> in the refrigerant system <NUM>.

According to the above disclosure, for example in <FIG>, <FIG> and <FIG>, pure refrigerant lubricated (PRL) bearings are used in a screw compressor to support the loads on the rotors. The PRL bearings operate with a relatively low viscosity lubricant, such as liquid refrigerant as the working fluid. The liquid refrigerant as the working fluid is drawn from the chiller condenser and injected directly to each individual bearings or pack of bearings. The liquid flow can be adjusted by using flow restriction devices, such as an orifice.

With the above disclosed examples and 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 examples and embodiments, the working fluid, instead of oil, is used for lubricating bearings and rotors.

Claim 1:
A direct-drive refrigerant screw compressor (<NUM>), comprising:
a housing (<NUM>);
a compression chamber (<NUM>) in the housing (<NUM>);
a pair of rotors (<NUM>), each rotor of the pair of rotors (<NUM>) being rotationally disposed in the compression chamber (<NUM>) and including an outer surface (<NUM>) with a screw-geared profile;
wherein, for each rotor, the compressor (<NUM>) includes:
a plurality of bearing packs (<NUM>) disposed within a respective plurality of bearing chambers (<NUM>); and
a working fluid (<NUM>) disposed within each of the plurality of bearing chambers (<NUM>), the working fluid (<NUM>) providing oil-free lubrication to the plurality of bearing packs (<NUM>), wherein the working fluid (<NUM>) is refrigerant;
characterized in that:
for each rotor, the compressor (<NUM>) includes:
a plurality of bearing lubrication ports (<NUM>) extending through the housing (<NUM>) and into each of the plurality of bearing chambers (<NUM>), and configured for injecting the working fluid (<NUM>) into each of the plurality of bearing chambers (<NUM>) when the compressor (<NUM>) is running,
wherein for each rotor:
the plurality of bearing lubrication ports (<NUM>) include a respective plurality of flow control orifices (<NUM>) to reduce a flow volume or rate from a condenser (<NUM>),
wherein the respective plurality of flow control orifices (<NUM>) are in the compressor housing (<NUM>);
the plurality of bearing chambers (<NUM>) include a forward bearing chamber (200a) and an aft bearing chamber (200b); and
the plurality of bearing lubrication ports (<NUM>) include a forward bearing lubrication port (300a) and an aft bearing lubrication port (300b) configured for directing the working fluid (<NUM>) into the respective plurality of bearing chambers (<NUM>).