PORTED SHROUD ON RADIALLY NESTED DUAL STATE COMPRESSOR

Description

This application claims the benefit of Indian Provisional Patent Application No. 202411092802, filed Nov. 27, 2024, the entire contents of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to systems and techniques for producing conditioned air for a vehicle, and more particularly, to compressor systems and techniques for producing compressed vapor refrigerant.

BACKGROUND

A vapor cycle system may cool a fresh air stream using a refrigerant. The vapor cooling system compresses and condenses the refrigerant from a relatively low-pressure vapor to a relatively high-pressure liquid, which then expands and evaporates to remove heat from the fresh air stream.

SUMMARY

A vapor cycle system (VCS) may monitor and control the temperatures of systems and/or components within a vehicle. A VCS may include one or more centrifugal compressors which compresses and condenses a refrigerant flowing within the VCS from a relative-low pressure vapor to a relatively high-pressure fluid. In some examples, a compressor system of a VCS may include multiple centrifugal compressors coupled in series to cause the compressor system to output the refrigerant at a specific pressure ratio (e.g., a ratio of the pressure of the refrigerant at an output of the compressor system to the pressure of the refrigerant at an input of the compressor system). When multiple compressors are coupled in series, each compressor may receive the refrigerant from an output of a preceding compressor in the series and output the refrigerant directly into a succeeding compressor in the series.

Other compressor systems including multiple compressors coupled in series may include two separate compressor wheels that are coupled along a longitudinal axis or a dual-stage compressor wheel with separate impellers on opposite sides of the compressor wheel. Such designs may require increased space within a vehicle, increased weight allowances, increased packaging requirements, and increased production cost relative to a compressor system with a single compressor. The disclosure describes an example compressor system with a nested compressor architecture. One compressor wheel may be positioned radially within and longitudinally aligned with another compressor wheel along a longitudinal axis of a compressor of the example compressor system. The compressor wheels may be fluidically connected to allow the compressor wheels to run in series.

Compressor systems may be limited in their range of operational mass flow rates based on the pressure ratio across the compressor, in part due to surge conditions. In surge conditions the compressor system may be unable to maintain continuous flow, leading to instability and reduced performance. A ported shroud surrounding a second wheel of the two separate compressor wheels may allow some of the fluid in the compressor to exit the main flow path and recirculate back to an inlet of the compressor. By relieving pressure and enabling a controlled recirculation, the compressor can continue stable operation at an increased range of pressure ratios and mass flow rates without stalling or surging.

The example compressor system may provide several advantages over other compressor systems. The example compressor systems described herein may exhibit reduced space requirements, complexity, weight requirements, and/or packaging space compared to another compressor system with multiple compressors or compressor wheels coupled in series. Additionally, the example ported shroud of the example compressor system described herein may increase the performance and/or efficiency of the example compressor system relative to other example compressor systems.

In some examples, the disclosure is directed to a compressor comprising: a first compressor wheel comprising: a first chamber configured to retain a medium; a first impeller disposed within the first chamber, wherein the first impeller is configured to revolve around a longitudinal axis of the compressor and within the first chamber; and a diffuser fluidically connected to the first chamber and configured to output the medium from the first chamber; and a second compressor wheel comprising: a second chamber disposed radially outwards of the first chamber relative to the longitudinal axis, wherein the second chamber is separated from the first chamber by a first outer wall of the first chamber, and wherein the second chamber is configured to receive the outputted medium from the first chamber; a second impeller disposed within the second chamber, wherein the second impeller is configured to revolve around the longitudinal axis of the compressor within the second chamber; and one or more apertures disposed in a wall of the second chamber, wherein the one or more apertures are configured to allow fluid to recirculate from within the second impeller to an inlet of the second impeller.

In some examples, the disclosure is directed to a compressor comprising: a first compressor wheel comprising: a first chamber configured to retain a medium; a first impeller disposed within the first chamber, wherein the first impeller is configured to revolve around a longitudinal axis of the compressor and within the first chamber; and a diffuser fluidically connected to the first chamber and configured to output the medium from the first chamber; and a second compressor wheel comprising: a second chamber disposed radially outwards of the first chamber relative to the longitudinal axis, wherein the second chamber is separated from the first chamber by a first outer wall of the first chamber, and wherein the second chamber is configured to receive the outputted medium from the first chamber; a second impeller disposed within the second chamber, wherein the second impeller is configured to revolve around the longitudinal axis of the compressor within the second chamber; and one or more apertures disposed in a wall of the second chamber, wherein the one or more apertures are configured to allow fluid to recirculate from within the second chamber to an inlet of the second chamber.

In some examples, the disclosure is directed to a vapor cooling system comprising: a condenser; an evaporator; an expansion device; and a compressor fluidically coupled to one of more of the condenser or the evaporator and to the expansion device to form a refrigerant circuit, wherein the compressor comprises: a first compressor wheel comprising: a first chamber configured to retain a medium; a first impeller disposed within the first chamber, wherein the first impeller is configured to revolve around a longitudinal axis of the compressor and within the first chamber; and a diffuser fluidically connected to the first chamber and configured to output the medium from the first chamber; and a second compressor wheel comprising: a second chamber disposed radially outwards of the first chamber relative to the longitudinal axis, wherein the second chamber is separated from the first chamber by a first outer wall of the first chamber, and wherein the second chamber is configured to receive the outputted medium from the first chamber; a second impeller disposed within the second chamber, wherein the second impeller is configured to revolve around the longitudinal axis of the compressor within the second chamber; and one or more apertures disposed in a wall of the second chamber, wherein the one or more apertures are configured to allow fluid to recirculate from within the second chamber to an inlet of the second chamber.

The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE FIGURES

The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

FIG. 1 is a block diagram illustrating a system for generating conditioned air that includes an example vapor cooling system (VCS).

FIG. 2 is a conceptual diagram illustrating an example vapor cycle compressor (VCC).

FIG. 3 is a conceptual diagram illustrating a cross-sectional view of the example centrifugal compressor of FIG. 2, the cross-section being taken along line A-A of FIG. 2.

FIG. 4A is a conceptual diagram illustrating a cross-sectional view of the example centrifugal compressor of FIG. 2, the cross-section being taken along line B-B of FIG. 3.

FIG. 4B is a conceptual diagram illustrating a cross-sectional view of the example centrifugal compressor of FIG. 2, the cross-section being take along line C-C of FIG. 3.

FIG. 5 is a conceptual diagram illustrating a magnified view of the example VCC of FIG. 2.

FIG. 6 is a conceptual diagram illustrating another magnified view of the example VCC of FIG. 2.

FIGS. 7A-7B are conceptual diagrams illustrating an example arrangement of ribs in a ported shroud.

FIGS. 8A-8B are conceptual diagrams illustrating another example arrangement of ribs in a ported shroud.

FIG. 9 is a flow diagram illustrating an example process of manufacturing an example compressor.

Like reference characters refer to like elements throughout the figures and description.

DETAILED DESCRIPTION

Various examples discussed herein describe vapor cooling systems, vapor compression systems, centrifugal compressors, centrifugal compressor systems, and centrifugal compressor components that include two or more compressor wheels coupled in series and in a nested configuration. The example systems and components discussed herein also include a ported shroud surrounding one of the compressor wheels.

A centrifugal compressor system is configured to drive one or more impellers of one or more compressor wheels using a compressor motor to compress a vapor refrigerant to a higher pressure. Compressor wheels may be coupled in series to increase a pressure ratio generated by the compressor system. In such examples, a first compressor wheel may compress a refrigerant and may output the refrigerant directly into a second compressor wheel. The second compressor wheel may then further compress the refrigerant, thereby increasing the pressure ratio of the refrigerant. Multiple impellers of multiple compressor wheels coupled in series may be driven by a same compressor motor.

In some examples, a centrifugal compressor system with multiple compressor wheels coupled in series may position multiple compressor wheels along a longitudinal axis. For example, a first-stage compressor wheel may be proximal to a second-stage compressor wheel. Such positioning may increase the length and space requirements for the compressor system. In some examples, a centrifugal compressor system may increase the pressure ratio via inclusion of a dual-stage compressor wheel, where the compressor wheel includes two separate impellers disposed on opposite faces of the compressor wheel. A compressor system with a dual-stage compressor requires a housing with increased space allocations to direct refrigerant towards both impellers, thereby increasing the length, width, and complexity of the compressor system.

The disclosure describes a compressor system with two or more compressor wheels in a nested configuration. For example, one compressor wheel is disposed radially within another compressor wheel. The compressor wheels of the example compressor system described herein may be longitudinally overlapping, thereby reducing the length and volume of the compressor system. The housing of the compressor system may direct refrigerant from the outlet of one compressor wheel into the outlet of a radially outward compressor wheel, thereby fluidically coupling the compressor wheels in series. The compressor wheels may be driven by a single drive shaft and/or may be formed into a single component, thereby reducing complexity and cost requirements to manufacture the compressor system.

The compressor system also includes a ported shroud which increases the efficiency of the compressor system. Compressor systems may have limited ranges of operating states based on combinations of mass flow rates and pressure ratios of the compressors. For example, if a flow rate is very low while a pressure ratio is very high, the compressor may experience surge conditions, decreasing the efficiency of the compressor. In order to ensure consistent flow rates a ported shroud surrounding a wheel the compressor may allow some of the fluid in the compressor to exit the main flow path and recirculate back to an inlet of the compressor. By relieving pressure and enabling a controlled recirculation, the compressor can continue stable operation at an increased range of pressure ratios and mass flow rates without stalling or surging.

The example compressor system may provide several advantages over other compressor systems. The example compressor systems described herein may exhibit reduced space requirements, complexity, weight requirements, and/or packaging space compared to another compressor system with multiple compressors or compressor wheels coupled in series. Additionally, the example ported shroud of the example compressor system described herein may increase the performance and efficiency of the example compressor system relative to other example compressor systems.

Vapor cooling systems, compressors, compressor systems, and compressor components discussed herein may be used to produce conditioned air for a variety of applications. In some examples, vapor cooling systems discussed herein may be used to cool pressurized air, such as for a pressurized cabin or avionics systems of an aircraft. In some examples, vapor cooling systems, including vapor-cooled compression systems, may be used, for aircraft and non-aircraft implementations, to cool liquid, non-pressurized air, etc., in accordance with one or more of the various techniques of this disclosure. In another example, vapor cooling systems, including vapor-cooled compression systems, may be used, for aircraft and non-aircraft implementations, to cool equipment, such as through direct contact-cooling of equipment.

FIG. 1 is a block diagram illustrating an example system 100 for generating conditioned air that includes a vapor cooling system (VCS) 104. The conditioned air may be used to cool volumes or components of various cabins or avionics systems 122. Cabin/avionics 122 may be a compartment of a vehicle (e.g., an aircraft, an automobile, a spacecraft, a watercraft, etc.) that includes an internal environment and/or one or more avionics systems that receive cooled air for cooling equipment. For example, cabin/avionics 122 may be configured to house people, cargo, and the like, in the internal environment. It will be understood that avionics generally relate to aircraft, spacecraft, etc., and that other systems may include other electronic systems/control systems configured for cooling. Thus, while described as cabin/avionics 122, the techniques of this disclosure are not so limited, and a person skilled in the art will understand that the systems described herein may be employed in a variety of contexts without significantly departing from structures and mechanics described herein.

VCS 104 includes a vapor cycle compressor (VCC) 112, a condenser 106, an expansion device 108 (e.g., an expansion valve), and an evaporator 110 fluidically coupled to each other through pressurized refrigerant supply lines to form a refrigerant circuit. A variety of refrigerants may be used in VCS 104, as will be explained further below.

VCC 112 may be configured to receive vapor refrigerant from evaporator 110 and compress and pump vapor refrigerant to condenser 106. VCC 112 may include a centrifugal compressor system configured to receive the vapor refrigerant at an inlet pressure and discharge the vapor refrigerant at a higher outlet pressure. VCC 112 may include one or more compression stages and an electrically driven motor. The motor may be configured to receive electrical power, such as from a motor controller 120, and generate mechanical power to drive the one or more compression stages. Condenser 106 may be configured to receive saturated vapor refrigerant from VCC 112, condense the vapor refrigerant, and discharge saturated refrigerant to an expansion device 108. Condenser 106 may be cooled by environmental air, such as ram air flow, from a ram air system 102, or another fluid such as fuel or heat transport fluids.

Expansion device 108 may be configured to control flow of refrigerant to evaporator 110 and reduce a pressure of saturated refrigerant prior to entry into evaporator 110. Expansion device 108 may be an orifice, tube, metered valve, or other device configured to reduce a pressure of a saturated refrigerant. Evaporator 110 may be configured to receive cabin pressure air, such as from an air supply system 124, remove heat from cabin air using a refrigerant, and discharge cabin air to cabin/avionics 122. On a refrigerant side, evaporator 110 may be configured to receive saturated refrigerant, absorb heat from the cabin air, vaporize the refrigerant, and discharge superheated vapor refrigerant.

System 100 includes a control system 114 for controlling various conditions of VCS 104, such as refrigerant flow rate, refrigerant vapor composition, refrigerant temperature, and the like. Control system 114 may be configured to monitor and/or operate one or more process control components of system 100. For example, control system 114 may be communicatively coupled to any of air supply system 124, ram air system 102, VCC 112, expansion device 108, or any other component of system 100. Control system 114 may also be communicatively coupled to instrumentation, such as flow meters, temperature sensors, and pressure sensors, and configured to receive measurement signals from the instrumentation. For example, control system 114 may be configured to receive measurement signals for various parameters of VCS 104, such as a speed of VCC 112, temperature of cabin air leaving evaporator 110, or a superheat of vapor refrigerant entering VCC 112, determine a mismatch between the measurement signals and a setpoint for the corresponding parameter, and send a control signal to one or more components of system 100 to reduce the mismatch and return the parameter to within the setpoint. Control system 114 may include any of a wide range of devices, including processors (e.g., one or more microprocessors, one or more application specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), or the like), servers, desktop computers, notebook (i.e., laptop) computers, tablet computers, and the like.

Control system 114 may include a motor controller 120 configured to control a motor of VCC 112. As discussed above, a motor may provide mechanical power to impellers of VCC 112, and therefore modulate flow rate of refrigerant through VCS 104. The speed of VCC 112 may correspond to various temperature setpoints of VCS 104, such as cooling demands of evaporator 110 and inlet superheat of the vapor refrigerant into VCC 112. To control a speed of VCC 112, motor controller 120 may be configured to send control signals to VCC 112 to control an amount of electrical power to the motor of VCC 112, such as from an APU or other power supply. Control system 114 may include a vapor controller 116 configured to control a vapor composition of the refrigerant in VCS 104. To control a vapor composition of the refrigerant, vapor controller 116 may be configured to send control signals to expansion device 108 and/or evaporator 110 to control a position of expansion device 108 and/or a position of a bypass valve of evaporator 110, such as by closing expansion device 108 to increase a superheat of the refrigerant entering VCC 112. Control system 114 may include a pressure/flow controller 118 configured to control pressure and/or flow of supply air to evaporator 110. In some examples, pressure/flow controller 118 may be configured to control air supply system 124 to generate a particular flow of supply air from air supply system 124. For example, pressure/flow controller 118 may be configured to send control signals to air supply system 124 to control a pressure of supply air, such as by controlling an amount of bleed air or a speed of a load compressor (via an APU) or cabin air compressor. In some examples, pressure/flow controller 118 may be configured to control ram air system 102 in order to receive a particular flow of supply air from ram air system 102.

Vapor cooling system (e.g., vapor compression systems) discussed herein may include a centrifugal compressor to compress a vapor refrigerant and cool various components of the compressor using the vapor refrigerant as a cooling medium. For example, a compressor motor, shaft bearings, and other components of the centrifugal compressor that receive power and/or experience friction may produce heat that needs to be removed. Rather than remove this heat using external cooling, which may be heavy or inefficient to operate, centrifugal compressors described herein may use the incoming vapor refrigerant to cool various components of the centrifugal compressor, thereby reducing or eliminating external cooling of the centrifugal compressor.

FIG. 2 is a conceptual diagram illustrating an example VCC 112. VCC 112 may include a centrifugal compressor 202. VCC 112 may extend along a longitudinal axis 208 and may include a centrifugal compressor 202 (also referred to herein as “compressor 202”) disposed within a compressor housing 210 of VCC 112. Compressor 202 may include a first compressor wheel 216 nested radially within a second compressor wheel 220. VCC 112 may direct refrigerant 205 through from inlet port 204 of housing 210 through centrifugal compressor 202 (e.g., through both first compressor wheel 216 and second compressor wheel 220 in series) and out of one or more outlet port(s) 206 of housing 210. Refrigerant 205 may enter VCC 112 at inlet port 204 from evaporator 110 of VCS 104 and exit VCC 112 at outlet port(s) 206 into condenser 106 of VCS 104. VCC 112 includes one or more apertures 254 and a cavity 250 configured to allow refrigerant 205 to recirculate from within second compressor wheel 220 to an inlet of second compressor wheel 220. While FIG. 2 illustrates compressor 202 as including two nested compressor wheels (i.e., first compressor wheel 216 and second compressor wheel 220), other example compressors 202 described herein may include three or more nested compressor wheels with one or more apertures and/or cavities forming a recirculation path at the inlet of any one or more of the nested compressor wheels.

Compressor 202 may include a compressor body 203 extending along and around longitudinal axis 208. Compressor body 203 may define a cylindrical body around longitudinal axis 208. First compressor wheel 216 may be disposed radially outward of compressor body 203. First compressor wheel 216 may be affixed to compressor body 203. A housing of first compressor wheel 216 defining a first chamber may be affixed to compressor body 203 and, in some examples, an impeller of first compressor wheel 216 may be affixed to compressor body 203. Second compressor wheel 220 may be affixed to first compressor wheel 216 and may, by extension, be affixed to compressor body 203.

Compressor body 203 may define a channel 211 extending at least partially through compressor body 203. Channel 211 may be configured to retain a drive shaft 212 extending from a centrifugal motor. Compressor 202 may include features disposed within channel 211 or on compressor body 203 which may removably or permanently affix compressor 202 to drive shaft 212. When compressor 202 is affixed to drive shaft 212, rotation of drive shaft 212 may cause compressor 202 to rotate about longitudinal axis 208, thereby causing impellers within first compressor wheel 216 and second compressor wheel 220 to compress refrigerant 205.

First compressor wheel 216 may be disposed radially outwards of compressor body 203 relative to longitudinal axis 208. First compressor wheel 216 may define a first chamber configured to retain refrigerant 205. The first chamber may extend from inlet 214A to outlet 218A. First compressor wheel 216 may include an impeller disposed within the first chamber. The impeller may include one or more blades configured to rotate about longitudinal axis 208. Refrigerant 205 may enter first compressor wheel 216 via inlet 214A and exit first compressor wheel 216 via outlet 218A. Each of inlet 214A and outlet 218A may extend at least partially around longitudinal axis 208. For example, inlet 214A and/or outlet 218A may define a complete ring around longitudinal axis 208.

Second compressor wheel 220 may be disposed radially outwards of first compressor wheel 216. Second compressor wheel 220 may define a second chamber configured to retain refrigerant 205. The second chamber may be separated from the first chamber of first compressor wheel 216 via an outer wall of the first chamber and/or an inner wall of the second chamber. Although apertures 254 and cavity 250 are illustrated in an outer wall of the second chamber, in some examples, one or more apertures and/or cavities may be formed in an inner wall of the second chamber to form a recirculation path from inside the second chamber to the inlet of the second chamber. The second chamber may extend from inlet 214B to outlet 218B. Second compressor wheel 220 may include a second impeller disposed within the second chamber. The second impeller may include one or more blades configured to rotate about longitudinal axis 208. Refrigerant 205 may flow from outlet 218A of first compressor wheel 216 into second compressor wheel 220 via inlet 214B and exit second compressor wheel 220 via outlet 218B. Each of inlet 214B and outlet 218B may extend at least partially around longitudinal axis 208. For example, inlet 214B and/or outlet 218B may define a complete ring around longitudinal axis 208.

Housing 210 may define one or more channels 221 fluidically connecting outlet 218A to inlet 214B. Channel(s) 221 may be fully enclosed and may revolve at least partially around longitudinal axis 208. For example, as illustrated in FIG. 2, channel(s) 221 may define a torus shape radially outwards of compressor 202. Refrigerant 205 may exit outlet 218B and into outlet port 206 of VCC 112.

Outlet port 206 may be configured to output refrigerant 205 out of VCC 112. Outlet port 206 may define one or more openings fluidically coupled to a downstream component within the refrigeration circuit (e.g., condenser 106). In some examples, as illustrated in FIG. 2, outlet port 206 defines a torus shape radially outwards of compressor 202 and channel(s) 221 are disposed radially outwards of and/or around outlet port 206.

Centrifugal compressors described herein may be configured to form a relatively tight containment to hermetically seal the vapor refrigerant within the vapor compression system. For example, portions of housing 210 may be sealed to form an enclosure for compressor 202. Portions of housing 210 (e.g., portion(s) defining inlet port 204, portion(s) defining channel(s) 221, portion(s) defining outlet port 206) may be affixed to each other via one or more mechanisms or fixation features including, but are not limited to, bolts, screws, welds, adhesives, or the like. Housing 210 may hermetically seal refrigerant 205 from an environment outside of VCC 112 aside from inlet port 204 and outlet port 206

Refrigerant 205 may include a low-pressure refrigerant (e.g., a refrigerant having a relatively low saturation vapor pressure). For example, the refrigerant gas may be R-1233zd, r236fa, or r245fa, or a similar low-pressure refrigerant, as described herein.

A compressor motor may be coupled to drive shaft 212 and may be configured to rotate drive shaft 212 to rotate compressor 202. The centrifugal motor may include windings of a stator coupled to compressor 202 and/or housing 210 and a rotor coupled to drive shaft 212. Windings of the stator may be configured to receive an electrical signal from motor controller 120 and generate a dynamic magnetic field to drive the rotor. In some examples, the compressor motor may be configured to rotate compressor 202 at about 80,000 rotations per minute (RPM) or greater. For example, the compressor motor may be configured to spin compressor 202 at approximately 120,000 RPM.

One or more apertures 254 may be disposed in a wall of second chamber 404. In the example of FIG. 2, apertures 254 are disposed in an outer wall of second chamber 404 disposed radially outwards of the second impeller. Apertures 254 may be configured to allow fluid to recirculate from within second chamber 404 to inlet 214B of second chamber 404. For example, apertures 254 may be fluidically connected to second chamber 404 on one side, and may be fluidically connected to inlet 214B on another side through cavity 250. Apertures 254 and cavity 250 may define a recirculation path for fluid from within second chamber 404 to inlet 214B. In this way, abnormal pressure events (e.g., stall, surge) may be prevented or mitigated by allowing pressurized fluid to flow from within the main flow path of second chamber 404 and back to inlet 214B. This enables VCC 112 to operate efficiently over a broader range of conditions, improving low-end performance and extending the surge margin without negatively affecting high-end flow capacity. In some examples, one or more of apertures 254 and cavity 250 may extend at least partially around longitudinal axis 208. For example, apertures 254 may be a single aperture defining a complete ring around longitudinal axis 208. In some examples, cavity 250 may define a complete ring around longitudinal axis 208. In some examples, apertures 254 may define one or more slots in a wall of second chamber 404 extending circumferentially around longitudinal axis 208 in defined arc-lengths. In some examples, cavity 250 may include a plurality of cavities, wherein each cavity is formed in a wall of second chamber 404 such that each cavity fluidically connects a respective aperture of apertures 254 with inlet 214B.

Including apertures 254 on radially nested compressor wheels (e.g., first compressor wheel 216 and second compressor wheel 220) may offer additional benefits over inclusion on another compressor system with multiple compressors or compressor wheels coupled in series. For example, the apertures 254 in a ported shroud on a radially nested compressor wheel may be smaller than apertures included in non-radially nested wheels, while achieving the same flow area. For example, an inlet opening of apertures 254 from second chamber 404 may define a longitudinal length (right-to-left distance in FIG. 2) and a circumferential distance (distance into or out of page in FIG. 2 around a circumference of second chamber 404). Because of the distance of apertures 254 from longitudinal axis 208, the circumferential distance of apertures 254 may be much larger than the circumferential distance available on apertures included in non-radially nested wheels, allowing for the same or increased overall opening area (e.g., longitudinal length multiplied by circumferential distance) given the same longitudinal length. Having a smaller necessary longitudinal length may reduce the amount of machining necessary to form an effective recirculation path via e.g., apertures 254. Furthermore, a smaller longitudinal length may increase the structural integrity of the wall of second chamber 404 in which apertures 254 and cavity 250 are disposed, compared to examples of apertures included in non-radially nested wheels.

Additionally, apertures 254 in a ported shroud on a radially nested compressor wheel may allow more flexibility in the selection of a port angle than apertures included in non-radially nested wheels. The port angle may be defined by an angle between an axis of fluid flow through second chamber 404 at the location of apertures 254, and an axis defined by a length of apertures 254, as discussed in more detail below. Apertures 254 that define a port angle greater than ninety degrees may be more effective at removing separation bubbles from the impellers, and may be more effective at facilitating recirculation flow from the impeller back to the inlet. However, apertures that define a port angle greater than ninety degrees may take up more longitudinal space in the compressor than apertures angled at 90 degrees with respect to the longitudinal axis. Compressors with non-radially nested wheels may take up significantly more space in a longitudinal direction than nested wheels according to the present disclosure. Therefore, compressors with non-radially nested wheels may limit the port angle to save longitudinal space, whereas according to the present disclosure, apertures 254 may be formed with any angle through the wall of second chamber 404 connecting second chamber 404 to cavity 250.

FIG. 3 is a conceptual diagram illustrating a cross-sectional view of the example centrifugal compressor 202 of VCC 112 of FIG. 2, the cross-section being taken along line A-A of FIG. 2. As illustrated in FIG. 3, first compressor wheel 216 may include a first impeller 302 disposed within a first chamber 402 and second compressor wheel 220 may include a second impeller 308 within a second chamber 404. First chamber 402 may extend from inlet 214A to outlet 218A and may include first diffuser 306A disposed at outlet 218A. Second chamber 404 may extend from inlet 214B to outlet 218B and may include second diffuser 306B disposed at outlet 218B. First chamber 402 and second chamber 404 may be separated by wall 312. In some examples, as illustrated in FIG. 3, second chamber 404 and second impeller 308 may be at least partially shrouded by wall 314.

Wall 314 may be a ported shroud around second chamber 404 and second impeller 308. For example, one or more apertures 254 may constitute ports through wall 314 configured to allow fluid to recirculate from within second chamber 404 to inlet 214B of second chamber 404.

First compressor wheel 216 may be disposed radially outwards of compressor body 203 relative to longitudinal axis 208 and may include first chamber 402, first impeller 302 disposed within first chamber 402, and first diffuser 306A coupled to the first chamber at outlet 218A. First chamber 402 may be enclosed from inlet 214A to outlet 218A and around the circumference of First chamber 402. First chamber 402 may be configured to retain refrigerant 205 entering compressor 202 from inlet port 204 of housing 210. First impeller 302 may be disposed within first chamber 402. In some examples, as illustrated in FIG. 3, first impeller 302 may be integral to first chamber 402. First impeller 302 may include a plurality of blades, each blade extending from inlet 214A towards outlet 218A. In some examples, each blade may extend from inlet 214A to outlet 218A. Each blade may extend at least partially or entirely from an outer surface of compressor body 203 defining a radially inner surface of the first chamber to wall 312 defining a radially outward surface of first chamber 402. Wall 312 may be an outer wall of first chamber 402.

When compressor 202 rotates about longitudinal axis 208, the blades of first impeller 302 impart kinetic energy to and increase speed of refrigerant 205 within first chamber 402. The blades of first impeller 302 may define a fillet 304 at the radially-outward-most edges of the blades. Fillet 304 may reduce stress concentration at the edges of the blades and increase longevity of first impeller 302. As illustrated in FIG. 3, fillet 304 may vary in width (e.g., may increase in width) along the longitudinal length of each blade.

First compressor wheel 216 may include first diffuser 306A disposed within first chamber 402 at or near outlet 218A. In some examples, first diffuser 306A is disposed outside of first compressor wheel 216 and is fluidically coupled to first chamber 402, e.g., at outlet 218A. First diffuser 306A may reduce the speed of refrigerant 205 exiting first chamber 402, thereby increase the pressure of refrigerant 205. First diffuser 306A may remain stationary relative to first impeller 302 and may cause refrigerant 205 exiting first impeller 302 to decelerate, which may lead to an increase in static pressure of refrigerant 205. First diffuser 306A may include one or more feature (e.g., vanes) which may cause refrigerant 205 to decelerate.

Second compressor wheel 220 includes a second chamber 404 extending from inlet 214B to outlet 218B, second impeller 308 disposed within second chamber 404, and second diffuser 306B coupled to second chamber 404 at outlet 218B. Refrigerant 205 may flow along channel(s) 221 of housing 210 from outlet 218A and into second chamber 404 via inlet 214B. Second chamber 404 may be isolated from the first chamber by wall 312. Wall 312 inhibits flow of refrigerant 205 between the first chamber and second chamber 404 within compressor 202.

Second impeller 308 includes a plurality of blades extending from inlet 214B towards outlet 218B. In some examples, each blade extends from inlet 214B to outlet 218B. Each blade may define a fillet 310 at a radially-outward-most edge, e.g., to reduce stress concentration at the edge of the blade. A width of fillet 310 may vary along a longitudinal length of the blade.

Second compressor wheel 220 includes second diffuser 306B coupled to second chamber 404 at or near outlet 218B. In some examples, second diffuser 306B may be disposed outside of compressor 202 but may be fluidically connected to second compressor wheel 220, e.g., at outlet 218B. Second compressor wheel 220 functions in a same way as first compressor wheel 216 to pressure refrigerant 205 contained within second chamber.

In some examples, second compressor wheel 220 may not be shrouded, such that a portion of housing 210 defines an outer wall (e.g., wall 314) of second chamber 404. In some examples, as illustrated in FIG. 3, second compressor wheel 220 is shrouded, such that a wall 314 integral to second compressor wheel 220 extends from inlet 214B to outlet 218B and around an entire outer circumference of second compressor wheel 220. Shrouding second compressor wheel 220 may increase the efficiency of second compressor wheel 220 by reducing the effects of friction on refrigerant 205 and/or by reducing unintended loss of refrigerant 205 from within second compressor wheel 220. In examples where second compressor wheel 220 is not shrouded, one or more apertures 254 and cavity 250 may be disposed in the portion of housing 210 defining the outer wall. For example, the one or more apertures 254 and cavity 250 may define a recirculation path within housing 210 for fluid to recirculate from inside second chamber 404 to inlet 214B of second chamber 404. Although apertures 254 and cavity 250 are described herein as being disposed in a shrouded wall of second chamber 404, it may be understood that the techniques and examples herein are equally applicable to a compressor with apertures 254 and cavity 250 disposed within a portion of housing 210 that defines a wall of second chamber 404.

First compressor wheel 216 and second compressor wheel 220 may be manufactured separately or as a single component. In some examples, a manufacturing system may manufacture first compressor wheel 216 and second compressor wheel 220 separately, nest first compressor wheel 216 within second compressor wheel 220, and affix first compressor wheel 216 to second compressor wheel 220. In some examples, a manufacturing system forms second compressor wheel 220 directly onto first compressor wheel 216. For example, the manufacturing system may form second impeller 308 directly on top of wall 312 and then form wall 314 directly onto second impeller 308. The manufacturing system may form one or more of first compressor wheel 216 or second compressor wheel 220 via three-dimensional (3D) printing or other additive manufacturing techniques.

FIG. 4A is a conceptual diagram illustrating a cross-sectional view of the example centrifugal compressor of FIG. 2, the cross-section being taken along line B-B of FIG. 3. As illustrated in FIG. 4A, first compressor wheel 216 and second compressor wheel 220 are disposed radially outwards of compressor body 203. Second compressor wheel 220 is disposed radially outwards of first compressor wheel 216 and is separated from first compressor wheel 216 by wall 312.

First compressor wheel 216 includes first impeller 302 disposed within first chamber 402. First impeller 302 includes a plurality of blades 403. Each of blades 403 may extend from an outer surface of compressor body 203 to wall 312. As illustrated in FIG. 4A, each of blades 403 may define a curvature along the cross-sectional length of blades 403 from compressor body 203 to wall 312. The curvature of blades 403 may facilitate transmission of energy from drive shaft 212 to refrigerant 205 within first chamber 402, thereby increasing pressure ratio for first compressor wheel 216. First impeller 302 may include any number of blades 403. First impeller 302 may include twelve blades 403, as illustrated in FIG. 4A, less than twelve blades 403, or more than twelve blades 403. Blades 403 may be equally distributed around a circumference of first impeller 302.

Second compressor wheel 220 includes second impeller 308 disposed within a second chamber 404. As illustrated in FIG. 4A, second chamber 404 is disposed radially outwards of first chamber 402 and is separated from first chamber 402 by wall 312. In some examples, as illustrated in FIG. 4A, second compressor wheel 220 may be shrouded, wherein wall 314 of second chamber 404 extends from inlet 214B to outlet 218B and around an entire circumference of second chamber 404. In some examples, wall 314 is a ported shroud. For example, one or more apertures 254 may constitute ports through wall 314 configured to allow fluid to recirculate from within second chamber 404 to inlet 214B of second chamber 404. Second impeller 308 includes a plurality of blades 405. Each of blades 405 may extend from wall 312 to wall 314 and/or an outer circumference of second chamber 404. Blades 405 may be affixed to and/or integral to the rest of compressor 202 (e.g., to wall 312). Second impeller 308 may have less than, twelve, or more than twelve blades 405. Blades 405 may be equally spaced around the circumference of second impeller 308. Each of blades 405 define a curvature from wall 312 to wall 314. The curvature for blades 405 may be the same as or different the curvature for blades 403. The curvature for blades 405 may be in the same direction as the curvature for blades 403, e.g., to improve compression of refrigerant 205 within compressor 202.

FIG. 4B is a conceptual diagram illustrating a cross-sectional view of the example centrifugal compressor 202 of FIG. 2, the cross-section being take along line C-C of FIG. 3. The cross-section of compressor 202 along line C-C illustrates cross-sections of first chamber 402, first impeller 302, and first diffuser 306A around outlet 218A of first compressor wheel 216. First diffuser 306A may include a plurality of vanes 406 distributed around a circumference of first diffuser 306A.

First chamber 402 may be fluidically coupled to first diffuser 306A and/or first diffuser 306A may be disposed at least partially within first chamber 402. At or around outlet 218A, refrigerant 205 exits from first chamber 402 and into first diffuser 306A. Rotation of first compressor wheel 216 about longitudinal axis 208 may cause blades 403 of first impeller 302 to impart kinetic energy to refrigerant 205 and increase the speed of refrigerant 205 travelling through first compressor wheel 216. When refrigerant 205 enters first diffuser 306A, vanes 406 of first diffuser 306A impedes flow of refrigerant 205 and reduces the speed of refrigerant 205. The reduction of speed of refrigerant 205 within first diffuser 306A increases the static pressure of refrigerant 205 (e.g., due to continuous flow of refrigerant 205 traveling at higher speeds into first diffuser 306A from within first chamber 402. Thus, refrigerant 205 exiting first diffuser 306A at outlet 218A may be at a higher pressure than refrigerant 205 entering first compressor wheel 216 at inlet 214A.

As illustrated in FIG. 4B, each of vanes 406 may define a curvature along a length of the vanes 406. The curvature of vanes 406 may be different from the curvature of blades 403 of first impeller 302. For example, vanes 406 and blades 403 may curve in different directions or define same or different radii of curvature. The curvature of vanes 406 increases resistance to the flow of refrigerant 205 through first diffuser 306A, thereby further reducing the speed of refrigerant 205 and increasing the pressure of refrigerant 205.

While not illustrated in FIG. 4B, second diffuser 306B of second compressor wheel 220 may increase the pressure of refrigerant 205 in a same manner as first diffuser 306A. For example, second diffuser 306B may include vanes configured to reduce the speed of refrigerant 205 within second diffuser 306B. The vanes of second diffuser 306B may define curvatures similar or different from curvatures of blades 405 of second impeller 308, e.g., to further reduce speed of refrigerant 205 within second diffuser 306B and increase the pressure of refrigerant 205 exiting second compressor wheel 220.

FIG. 5 is a conceptual diagram illustrating magnified view 240 of the example VCC 112 of FIG. 2. VCC 112 may include a first compressor wheel nested radially within a second compressor wheel, and one or more apertures 254 configured to allow fluid (e.g., refrigerant 205) to recirculate from within second chamber 404 to an inlet of second chamber 404.

VCC 112 may direct refrigerant 205 through centrifugal compressor 202 (e.g., through both the first compressor wheel and second compressor wheel in series) and out of one or more outlet port(s). The first compressor wheel may define a first chamber 402 configured to retain refrigerant 205 and a first impeller disposed within first chamber 402. Refrigerant 205 may enter first chamber 402 via inlet 214A and exit first chamber 402 via outlet 218A.

The second compressor wheel may be disposed radially outwards of the first compressor wheel. The second compressor wheel may define second chamber 404 configured to retain refrigerant 205. Second chamber 404 may be separated from first chamber 402 of the first compressor wheel via an outer wall of first chamber 402 and/or an inner wall of second chamber 404. Although apertures 254 and cavity 250 are illustrated in an outer wall 314 of second chamber 404, in some examples, one or more apertures and/or cavities may be formed in an inner wall of second chamber 404 to form a recirculation path 507 from inside second chamber 404 to inlet 214B of second chamber 404. In some examples, outer wall 314 may be a ported shroud around second chamber 404 and second impeller 308. For example, one or more apertures 254 may constitute ports through outer wall 314 configured to allow fluid to recirculate from within second chamber 404 to inlet 214B of second chamber 404. Outer wall 314 may shroud second chamber 404 from inlet 214B to outlet 218B and around a circumference of second chamber 404.

Second chamber 404 may extend from inlet 214B to outlet 218B. The second compressor wheel may include second impeller 308 disposed within second chamber 404. Second impeller 308 may include one or more blades. A proximal end of the one or more blades of second impeller 308 may define a leading edge 514 of second impeller 308, and a distal end of the one or more blades of second impeller 308 may define a trailing edge 518. In some examples, leading edge 514 is located at inlet 214B and trailing edge 518 is located at outlet 218B. In some examples, leading edge 514 and trailing edge 518 are not located precisely at inlet 214B and outlet 218B, respectively. Refrigerant 205 may flow from outlet 218A of first compressor wheel 216 into second compressor wheel 220 via inlet 214B and exit second compressor wheel 220 via outlet 218B.

Housing 210 may define one or more channels 221 fluidically connecting outlet 218A to inlet 214B. Channel(s) 221 may be fully enclosed and may revolve at least partially around longitudinal axis 208. For example, as illustrated in FIG. 2, channel(s) 221 may define a torus shape radially outwards of compressor 202. Refrigerant 205 may exit outlet 218B and into outlet port 206 of VCC 112.

One or more apertures 254 may be disposed in a wall of second chamber 404. In the example of FIG. 5, apertures 254 are disposed in an outer wall 314 of second chamber 404. Outer wall 314 and apertures 254 are disposed radially outwards of second impeller 308. Cavity 250 may be disposed radially outwards of outer wall 314 and/or apertures 254. Apertures 254 and cavity 250 may be configured to allow fluid to recirculate from within second chamber 404 to inlet 214B of second chamber 404. For example, apertures 254 may be fluidically connected to second chamber 404 at one or more inlet openings of apertures 254, and apertures 254 may be fluidically connected to cavity 250 at one or more outlet openings of apertures 254. Cavity 250 may fluidically connect apertures 254 with channels 221 at or near an inlet 214B of second chamber 404.

The fluidic connections between second chamber 404, apertures 254, cavity 250, and channels 221/inlet 214B may define recirculation path 507. Therefore, recirculation path 507 may be configured to allow fluid to recirculate from within second chamber 404 to inlet 214B. In this way, abnormal pressure events (e.g., stall, surge) may be prevented or mitigated by allowing pressurized refrigerant 205 to flow from within the main flow path of second chamber 404 and back to inlet 214B along recirculation path 507.

Second impeller 308 may define a meridional length, m_L, from leading edge 514 to trailing edge 518. For example, meridional length, m_L, may be defined by a longitudinal path of fluid through second impeller 308 from leading edge 514 to trailing edge 518 as seen in the example of FIG. 5. In some examples, apertures 254 may be disposed in a wall of second chamber 404 along the meridional length, m_L. For example, apertures may be disposed in outer wall 314 of second chamber 404 in a position that fluidically connects cavity 250 with fluid in chamber 404 in the path of the fluid along meridional length, m_L. Because meridional length, m_L, may be defined by the distance between leading edge 514 and trailing edge 518, apertures 254 may be disposed along a path of refrigerant 205 after refrigerant 205 has passed leading edge 514 in chamber 404. In this way, pressure abnormalities that may arise in chamber 404 may be mitigated by apertures 254 through recirculation path 507. In some examples, apertures 254 may be disposed in or near a throat of second impeller 308. For example, apertures 254 may be disposed in outer wall 314 of second chamber 404 along meridional length, m_L, between five and twenty five percent of the meridional length, m_L, from leading edge 514 to trailing edge 518. In some examples, apertures 254 may be disposed in outer wall 314 of second chamber 404 along meridional length, m_L, between ten and fifteen percent of the meridional length, m_L, from leading edge 514 to trailing edge 518.

FIG. 6 is a conceptual diagram illustrating an example second chamber 604 and recirculation path 607. Features illustrated in FIG. 6 may be substantially similar to like-named features of earlier figures. For example, apertures 654 may be substantially similar to apertures 554 of FIG. 5. As described above, a compressor may include a first compressor wheel nested radially within a second compressor wheel, and one or more apertures 654 disposed within a wall around the second compressor wheel. The second compressor wheel may define second chamber 604 configured to retain refrigerant 605 and a second impeller disposed within second chamber 604. During normal operation, refrigerant 605 may enter second chamber 604 via inlet 614 and exit second chamber 604 via outlet 618.

One or more apertures 654 may be disposed in a wall of second chamber 604, and be configured to allow fluid (e.g., refrigerant 605) to recirculate from within second chamber 604 to an inlet 614 of second chamber 604. In the example of FIG. 6, apertures 654 are disposed in outer wall 630 of second chamber 604. Outer wall 630 and apertures 654 may be disposed radially outwards of second chamber 604. Cavity 650 may be disposed radially outwards of outer wall 630 and/or apertures 654. Apertures 654 and cavity 650 may be configured to allow fluid to recirculate from within second chamber 604 to inlet 614 of second chamber 604. For example, apertures 654 may be fluidically connected to second chamber 604 at one or more inlet openings of apertures 654, and apertures 654 may be fluidically connected to cavity 650 at one or more outlet openings of apertures 654. Cavity 650 may fluidically connect apertures 654 with a channel at or near an inlet 614 of second chamber 604.

Recirculation path 607 may be configured to allow fluid to recirculate from within second chamber 604 to inlet 614. For example, the fluidic connections between second chamber 604, apertures 654, cavity 650, and inlet 614 may define recirculation path 607. In this way, abnormal pressure events (e.g., stall, surge) may be prevented or mitigated by allowing pressurized refrigerant 605 to flow from within the main flow path of second chamber 604 and back to inlet 614 along recirculation path 607. Cavity 650 may define only smooth angles along recirculation path 607. For example, as fluid travels along recirculation path 607, the fluid does not encounter any sharp corners, which could potentially block flow from the lower flow path areas to higher flow path areas. For example, from a lower flow path area of apertures 654 to a higher flow path area of cavity 650, or from a lower flow path area of cavity 650 to a higher flow path area of inlet 614.

In some examples, cavity 650 includes pocket 652. Pocket 652 may be disposed radially outwards of outer wall 630 and/or apertures 654 and behind a flow path of fluid in recirculation path 607. For example, as fluid flows through an outlet opening of apertures 654, it may curve along recirculation path 607 back towards inlet 614. Pocket 652 may be located radially outwards of outer wall 630 in an opposite direction from the curve of recirculation path 607 out of apertures 654. Pocket 652 may act as a pressure buffer that resists fluid flow from channel 621 in a reverse direction along recirculation path 607 during normal operation. Pocket 652 may also allow smooth fluid flow through apertures 654 and into cavity 650 without forcing the fluid through any sharp corners.

Apertures 654 may form an angle with respect to a path of fluid flow through second chamber 604. This may be referred to as a port angle, θ. In some examples, the port angle, θ, may be defined by an angle between a path of fluid flow at inlet 614 and an axis of apertures 654. In some examples, port angle, θ, may be defined by an angle between an axis of apertures 654 and a path of fluid flow through second chamber 604 at the location of apertures 654. For example, the second impeller in second chamber 604 may define a meridional length from a leading edge of the second impeller to a trailing edge of the second impeller. Apertures 654 may be disposed in a wall of second chamber 604 a distance along the meridional length. Apertures 654 may also define aperture axis 656 along the primary path of fluid flow through apertures 654 from second chamber 604 to cavity 650. Fluid flow through second chamber 604 may define a flow axis tangential to the path of fluid flow at any given point of the fluid flow path along the meridional length. For example, fluid flow through second chamber 604 may define flow axis 658 at a location along the meridional length where apertures 654 are disposed in a wall of second chamber 604. Thus, port angle, θ, may be defined by an angle between a path of fluid flow through apertures 654 and a path of fluid flow through second chamber 604 at the location of apertures 654. In the example of FIG. 6, the port angle, θ, is defined by an angle between aperture axis 656 and flow axis 658. In some examples, port angle, θ, may form a ninety degree angle.

In some examples, apertures 654 may form an obtuse angle with respect to a path of fluid flow through second chamber 604. For example, apertures 654 may be angled such that apertures 654 define a port angle greater than ninety degrees. Apertures 654 so angled may be more effective at removing separation bubbles from the impellers, preventing apertures 654 form becoming blocked, and allowing more effective at facilitating recirculation flow from the impeller back to the inlet, than apertures that form ninety degree angles with respect to fluid flow in the second chamber.

FIGS. 7A-7B are conceptual diagrams illustrating an example arrangement of ribs 710 in a ported shroud. FIG. 7A illustrates an expanded view of one or more example apertures 754A-754N (together, apertures 754) and a cavity 750 in the ported shroud. FIG. 7B illustrates a conceptual diagram illustrating an isometric view of an example centrifugal compressor with a cross-sectional taken along a line B-B as in the example of FIG. 3.

Features illustrated in FIGS. 7A-7B may be substantially similar to like-named features of earlier figures. For example, apertures 754 may be substantially similar to apertures 554 of FIG. 5. As described above, a compressor may include a first compressor wheel nested radially within a second compressor wheel, and one or more apertures 754 disposed within a wall around the second compressor wheel. The first compressor wheel may define a first chamber 702 configured to retain a fluid and a first impeller disposed within first chamber 702. The second compressor wheel may define second chamber 704 configured to retain a fluid (e.g., refrigerant) and a second impeller disposed within second chamber 704.

One or more apertures 754 may be disposed in a wall of second chamber 704, and be configured to allow fluid (e.g., refrigerant) to recirculate from within second chamber 704 to an inlet of second chamber 704. In the example of FIG. 7, apertures 754 are disposed in outer wall 730 of second chamber 704. Outer wall 730 and apertures 754 may be disposed radially outwards of second chamber 704. Cavity 750 may be disposed radially outwards of outer wall 730 and/or apertures 754. Apertures 754 and cavity 750 may be configured to allow fluid to recirculate from within second chamber 704 to an inlet of second chamber 704. For example, apertures 754 may be fluidically connected to second chamber 704 at one or more inlet openings of apertures 754, and apertures 754 may be fluidically connected to cavity 750 at one or more outlet openings of apertures 754. Cavity 750 may fluidically connect apertures 754 with a channel at or near an inlet of second chamber 704. Cavity 750 may include a cross-sectional cavity area 751 for the recirculation path. Cavity area 751 may be in the range of 5% to 15% of an area of aperture 754.

In some examples, as discussed above, one or more of apertures 754 and cavity 750 may extend at least partially around longitudinal axis 708. In the example of FIG. 7B, cavity 750 defines a complete ring around longitudinal axis 708, and apertures 754 define a plurality of slots in outer wall 730 of second chamber 604. Although only apertures 754A, 754B, and 754N are labeled, the example of FIG. 7B includes more than three apertures 754. In some examples, the compressor may include any number of one or more apertures. The plurality of slots of apertures 754 may extend circumferentially around longitudinal axis 708 in defined arc-lengths. In some examples, each of the slots of apertures 754 may be evenly spaced around the circumference of outer wall 730. Outer wall 730 may be a ported shroud around second chamber 704.

In some examples, the compressor includes a plurality of ribs 710A-710N (together, ribs 710) in outer wall 730. Ribs 710 may reinforce outer wall 730. In the example of FIG. 7B, each of the plurality of ribs 710 is disposed between each of the plurality of apertures 754. An arc-length of an aperture slot may be defined by the circumferential length of an aperture between successive ribs of ribs 710. In some examples, each of apertures 754 may include an arc spanning an angle of between 60 degrees and 80 degrees. Although only ribs 710A, 710B, and 710N are labeled, the example of FIG. 7B includes more than three ribs 710. In some examples, the compressor may include any number of ribs. In some examples, the compressor may include at least three ribs to stabilize outer wall 730. In some examples, ribs 710 may be evenly distributed around a circumference of outer wall 730.

The second impeller disposed within second chamber 704 may include a plurality of blades 705A-705N (together, blades 705). Each of blades 705 may extend from an inner wall of second chamber 704 to outer wall 730 of second chamber 704. Blades 705 may be equally spaced around the circumference of the second impeller. Apertures 754 and ribs 710 may be arranged circumferentially in outer wall 730 such that, as the second impeller (and thereby also blades 705) revolves around longitudinal axis 708, at least a portion of apertures 754 is always disposed in a portion of outer wall 730 between each of blades 705. In this way, each separate path between blades 705 that fluid may take through the second impeller is always connected to a recirculation path through apertures 754 and cavity 750 back to an inlet of second chamber 704.

In some examples, the compressor may reinforce outer wall 730 without ribs 710. For example, outer wall 730 may be structured such that ribs 710 are not formed, but outer wall 730 may still be attached to a housing of the compressor.

FIGS. 8A-8B are conceptual diagrams illustrating another example arrangement of ribs connected to a ported shroud. FIG. 8A illustrates an expanded view of one or more example apertures in the ported shroud. FIG. 8B illustrates a conceptual diagram illustrating an isometric view of an example centrifugal compressor with a cross-section taken along a line B-B as in the example of FIG. 3.

Features illustrated in FIGS. 8A-8B may be substantially similar to like-named features of earlier figures. For example, aperture 854 may be substantially similar to apertures 554 of FIG. 5. As described above, a compressor may include a first compressor wheel nested radially within a second compressor wheel, and an aperture 854 disposed within a wall around the second compressor wheel. The first compressor wheel may define a first chamber 802 configured to retain a fluid and a first impeller disposed within first chamber 802. The second compressor wheel may define second chamber 804 configured to retain a fluid (e.g., refrigerant) and a second impeller disposed within second chamber 804.

Aperture 854 may be disposed in a wall of second chamber 804, and be configured to allow fluid (e.g., refrigerant) to recirculate from within second chamber 804 to an inlet of second chamber 804. In the example of FIGS. 8A-8B, aperture 854 is disposed in outer wall 830 of second chamber 804. Outer wall 830 and aperture 854 may be disposed radially outwards of second chamber 804. Cavity 850 may be disposed radially outwards of outer wall 830 and/or aperture 854. Aperture 854 and cavity 850 may be configured to allow fluid to recirculate from within second chamber 804 to an inlet of second chamber 804. For example, aperture 854 may be fluidically connected to second chamber 804 at one or more inlet openings 858 of aperture 854, and aperture 854 may be fluidically connected to cavity 850 at one or more outlet openings 860 of aperture 854. Cavity 850 may fluidically connect aperture 854 with a channel at or near an inlet of second chamber 804. In some examples, aperture 854 may have a width 856 of 10 to 20%. In some examples, aperture 854 may maintain a constant width 856 from inlet opening 858 to outlet opening 860.

In some examples, as discussed above, aperture 854 and cavity 850 may extend at least partially around longitudinal axis 808. In the example of FIG. 8B, aperture 854 forms a single slot defining a complete ring around longitudinal axis 808. For example, aperture 854 may be disposed in outer wall 830 along an entire circumference of outer wall 830. In some examples, cavity 850 may define a complete ring around longitudinal axis 808.

In some examples, the compressor includes a plurality of ribs 810A-810N (together, ribs 810) supporting outer wall 830. Ribs 810 may reinforce outer wall 830. In the example of FIG. 8B, The plurality of ribs 810 extend radially outward from outer wall 830 through the recirculation path. Although only ribs 810A, 810B, and 810N are labeled, the example of FIG. 8B includes more than three ribs 810. In some examples, the compressor may include any number of ribs. In some examples, the compressor may include at least three ribs to stabilize outer wall 830.

FIG. 9 is a flow diagram illustrating an example process of manufacturing an example compressor 202 of VCC 112. While FIG. 9 illustrates a process for manufacturing compressor 202 including two compressor wheels (i.e., first compressor wheel 216, second compressor wheel 220), the process may be applied to form compressor 202 with three or more compressor wheels.

A manufacturing system may form first chamber 402 of first compressor wheel 216 around longitudinal axis 208 (902). The manufacturing system may form compressor body 203 around longitudinal axis 208. Compressor body 203 may define channel 211 extending from a first end of compressor body 203 to a second end of compressor body 203. Channel 211 may be sized to receive and/or retain drive shaft 212 connecting compressor 202 to a motor of VCC 112. The manufacturing system may form and/or affix walls defining first chamber to compressor body 203, e.g., such that first chamber 402 is defined radially outwards of compressor body 203. The manufacturing system may form the walls directly onto a surface of compressor body 203, e.g., via additive manufacturing. In some examples, the manufacturing system forms the walls separately and subsequently affixes the walls to the surface of compressor body 203, e.g., via welding, fixation mechanisms, or application of an adhesive. The walls may define the internal dimensions of first chamber 402. First chamber 402 may not be fully enclosed, e.g., to facilitate insertion and/or manufacture of first impeller 302 in first chamber 402.

The manufacturing system may form walls of first chamber 402 to define an inlet 214A and an outlet 218A. In some examples, the manufacturing system may shape first chamber 402 to include a mixed flow exducer, e.g., such that outlet 218A extends in both a longitudinal direction 508 along longitudinal axis 208 and in a radial direction 510.

The manufacturing system may dispose first impeller 302 within first chamber 402 (904). First impeller 302 may be disposed within first chamber 402 and may extend from a radially-inward-most surface of first chamber 402 towards or to a radially-outward-most surface of first chamber 402. In some examples, the manufacturing system forms blades 403 of first impeller 302 directly within first chamber 402. For example, the manufacturing system may form blades 403 directly onto a surface of first chamber 402, e.g., an outer surface of compressor body 203. In some examples, the manufacturing system forms blades 403 separately and affixes blades 403 to one or more surfaces of first chamber 402 (e.g., to the outer surface of compressor body 203) via welding, one or more fixation features, an adhesive, or the like. The manufacturing system may form each blade 403 to define a fillet 304 along a radially-outward-most edge of the blade 403. Fillet 304 may define a constant width 502 or may define a varying width 502 along the length of the blade.

In some examples, the manufacturing system may form and/or affix vanes 406 of diffuser 306A into first chamber 402, e.g., at a position downstream of first impeller 302. The manufacturing system may form and/or affix vanes 406 in a similar manner as blades 403 of first impeller 302. For example, the manufacturing system may form vanes 406 and/or blades 403 via an additive manufacturing technique.

After first impeller 302 is disposed within and affixed to one or more surfaces of first chamber 402, the manufacturing system may form and/or affix wall 312 to first chamber 402, e.g., to fully enclose first chamber 402 around a circumference of first compressor wheel. First chamber 402 may define inlet 214A and outlet 218A to allow for flow of refrigerant 205 through first chamber 402.

The manufacturing system may form second chamber 404 of second compressor wheel 220 (906). The manufacturing system may form second chamber 404 into a torus shape. Second chamber 404 may a recess radially inwards of an inner wall (e.g., wall 312) of second chamber 404. The recess may be sized to retain first compressor wheel 216 at a same longitudinal position as second chamber 404 and allow first compressor wheel 216 to be nested within second chamber 404. The manufacturing system may form second chamber 404 in a same or similar process as first chamber 402. In some examples, the manufacturing system may define second chamber 404 to include a mixed flow exducer.

The manufacturing system may dispose second impeller 308 within second chamber 404 (908). The manufacturing system may dispose second impeller 308 within second chamber 404 in a same or similar process as first impeller 302 within first chamber 402. Blades 405 of second impeller 308 may define similar or different dimensions as blades 403 of first impeller 302. Blades 405 may define fillets 310 of same or different widths 512 as widths 502 of blades 403. In some examples, after disposing blades 405 within second chamber 404, the manufacturing system may form wall 314 radially outward of second impeller 308 to enclose second chamber 404 around a circumference of second compressor wheel 220 and/or to shroud second impeller 308. Second chamber 404 may define inlet 214B and outlet 218B to allow for flow of refrigerant 205 through second chamber 404.

In some examples, the manufacturing system forms and/or disposes vanes of diffuser 306B within second chamber 404. The vanes may be disposed downstream of blades 405 of second impeller 308. The manufacturing system may form the vanes in accordance with the process described above with respect to diffuser 306A of first compressor wheel 216.

The manufacturing system may affix first compressor wheel 216 to second compressor wheel 220, wherein first compressor wheel 216 is nested within second compressor wheel 220 (910). First compressor wheel 216 and second compressor wheel 220 may be separate components. First compressor wheel 216 may define a same or shorter length along longitudinal axis 208 as second compressor wheel 220. First compressor wheel 216 may define a smaller radius than second compressor wheel 220. First compressor wheel 216 may be sized to be at least partially nested within the recess defined by second compressor wheel 220. The manufacturing system may affix first compressor wheel 216 to second compressor wheel 220 via welding, one or more fixation features (e.g., screws, bolts, clips, or the like), one or more adhesives, or the like. When first compressor wheel 216 is affixed to second compressor wheel 220, rotation of first compressor wheel 216 about longitudinal axis 208 causes second compressor wheel 220 to rotate about longitudinal axis 208. An outer wall 312 of first chamber 402 and an inner wall 312 of second chamber 404 may be affixed to form a single wall 312 separating first chamber 402 from second chamber 404.

The manufacturing system may form one or more apertures 254 in a wall of second chamber 404 (912). For example, the manufacturing system may form one or more apertures 254 in an outer wall 314 disposed radially outward from second chamber 404. Outer wall 314 may be a ported shroud around second chamber 404. For example, one or more apertures 254 may constitute ports through wall 314. Apertures 254 and a cavity 250 configured to allow refrigerant 205 to recirculate from within second chamber 404 to inlet 214B of second chamber 404. For example, apertures 254 may be fluidically connected to second chamber 404 on one side, and may be fluidically connected to inlet 214B on another side through cavity 250. Apertures 254 and cavity 250 may define a recirculation path 507 for fluid from within second chamber 404 to inlet 214B.

In some examples, one or more of apertures 254 and cavity 250 may be formed to extend at least partially around longitudinal axis 208. For example, apertures 254 may be a single aperture defining a complete ring around longitudinal axis 208. In some examples, cavity 250 may define a complete ring around longitudinal axis 208. In some examples, apertures 254 may define one or more slots in a wall of second chamber 404 extending circumferentially around longitudinal axis 208 in defined arc-lengths. In some examples, cavity 250 may include a plurality of cavities, wherein each cavity is formed in a wall of second chamber 404 such that each cavity fluidically connects a respective aperture of apertures 254 with inlet 214B.

In some examples, the manufacturing system may form a plurality of ribs 710A-710N (together, ribs 710) to reinforce outer wall 730. In some examples, each of the plurality of ribs 710 is disposed between each of the plurality of apertures 754. In some examples, each of a plurality of ribs 810 is disposed within a portion of cavity 850. In some examples, ribs may be formed both between each of a plurality of apertures and within portions of a cavity. In some examples, ribs 710 and/or ribs 810 may be evenly distributed around a circumference of a wall around the second chamber.

In some examples, apertures 254 may be formed in a wall of second chamber 404 along a meridional length, m_L. For example, apertures may be formed in outer wall 314 of second chamber 404 in a position that fluidically connects cavity 250 with fluid in chamber 404 in the path of the fluid along meridional length, m_L. Because meridional length, m_L, may be defined by the distance between leading edge 514 and trailing edge 518, apertures 254 may be formed along a path of refrigerant 205 after refrigerant 205 has passed leading edge 514 in chamber 404. In some examples, apertures 254 may be formed in or near a throat of second impeller 308. For example, apertures 254 may be formed in outer wall 314 of second chamber 404 along meridional length, m_L, between five and twenty five percent of the meridional length, m_L, from leading edge 514 to trailing edge 518. In some examples, apertures 254 may be formed in outer wall 314 of second chamber 404 along meridional length, m_L, between ten and fifteen percent of the meridional length, m_L, from leading edge 514 to trailing edge 518.

In some examples, cavity 550 may be formed to define only smooth angles along recirculation path 507. For example, as fluid travels along recirculation path 507, the fluid does not encounter any sharp corners, which could potentially block flow from the lower flow path areas to higher flow path areas. For example, from a lower flow path area of apertures 554 to a higher flow path area of cavity 550, or from a lower flow path area of cavity 550 to a higher flow path area of inlet 214B.

In some examples, the manufacturing system may form a pocket 652 as part of cavity 650. Pocket 652 may be formed radially outwards of outer wall 630 and/or apertures 654 and behind a flow path of fluid in recirculation path 607. For example, as fluid flows through an outlet opening of apertures 654, it may curve along recirculation path 607 back towards inlet 614. Pocket 652 may be formed radially outwards of outer wall 630 in an opposite direction from the curve of recirculation path 607 out of apertures 654. Pocket 652 may act as a pressure buffer that resists fluid flow from channel 621 in a reverse direction along recirculation path 607 during normal operation. Pocket 652 may also allow smooth fluid flow through apertures 654 and into cavity 650 without forcing the fluid through any sharp corners.

The manufacturing system may form apertures 654 with a port angle, θ, defined by an angle between a path of fluid flow through apertures 654 and a path of fluid flow through second chamber 604 at the location of apertures 654. For example, in the example of FIG. 6, the port angle, θ, is defined by an angle between aperture axis 656 and flow axis 658. In some examples, apertures 654 may be formed with an obtuse angle with respect to a path of fluid flow through second chamber 604. For example, apertures 654 may be formed such that apertures 654 define a port angle greater than ninety degrees.

The manufacturing system may position compressor 202 within housing 210 of VCC 112 (914). Housing 210 may direct refrigerant 205 into compressor 202, between compressor wheels of compressor 202, and away from compressor 202. Housing may extend around compressor 202 and may define one or more channels 221 linking compressor wheels. The manufacturing system may position compressor 202 within at least a portion of housing 210 and form the remainder of housing 210 around compressor 202. For example, housing 210 may be formed from multiple components and the manufacturing system may connected the multiple components around compressor 202 to form a single, continuous housing 210. Together, housing 210 and compressor 202 may define VCC 112 of system 100, as illustrated in FIG. 1. In some examples, housing 210 may be disassembled and reassembled, e.g., to facilitate maintenance and replacement of components of VCC 112.

In some examples, one or more apertures 254 and cavity 250 may be disposed in a portion of housing 210 defining a wall around second chamber 404. For example, the one or more apertures 254 and cavity 250 may define a recirculation path within housing 210 for fluid to recirculate from inside second chamber 404 to inlet 214B of second chamber 404. Although apertures 254 and cavity 250 are described herein as being disposed in a shrouded outer wall (e.g., a ported shroud) of second chamber 404, it may be understood that the techniques and examples herein are equally applicable to a compressor with apertures 254 and cavity 250 disposed within a portion of housing 210 that defines a wall of second chamber 404. Cavity 250 may define a cross-sectional area about three to eight times a cross-sectional area of one of apertures 254.

A “vehicle” may be an aircraft, a land vehicle such as an automobile, or a water vehicle such as a ship or a submarine. An “aircraft” as described and claimed herein may include any fixed-wing or rotary-wing aircraft, airship (e.g., dirigible or blimp buoyed by helium or other lighter-than-air gas), suborbital spaceplane, spacecraft, expendable or reusable launch vehicle or launch vehicle stage, or other type of flying device. An “aircraft” as described and claimed herein may include any crewed or uncrewed craft (e.g., uncrewed aerial vehicle (UAV), flying robot, or automated cargo or parcel delivery drone or other craft).

The following examples may illustrate one or more of the techniques of this disclosure.

Example 1: a compressor comprising: a first compressor wheel comprising: a first chamber configured to retain a medium; a first impeller disposed within the first chamber, wherein the first impeller is configured to revolve around a longitudinal axis of the compressor and within the first chamber; and a diffuser fluidically connected to the first chamber and configured to output the medium from the first chamber; and a second compressor wheel comprising: a second chamber disposed radially outwards of the first chamber relative to the longitudinal axis, wherein the second chamber is separated from the first chamber by a first outer wall of the first chamber, and wherein the second chamber is configured to receive the outputted medium from the first chamber; a second impeller disposed within the second chamber, wherein the second impeller is configured to revolve around the longitudinal axis of the compressor within the second chamber; and one or more apertures disposed in a wall of the second chamber, wherein the one or more apertures are configured to allow fluid to recirculate from within the second chamber to an inlet of the second chamber.

Example 2: the compressor of example 1, wherein the second impeller defines a meridional length from a leading edge of the second impeller to a trailing edge of the second impeller, and wherein the one or more apertures are disposed in the wall along the meridional length.

Example 3: the compressor of example 2, wherein the one or more apertures are disposed in the wall of the second chamber along the meridional length between ten and fifteen percent of the meridional length from the leading edge to the trailing edge.

Example 4: the compressor of any of examples 1-3, further comprising a cavity disposed radially outwards of a second outer wall disposed radially outwards of the second impeller, wherein the cavity is fluidically connected to the second chamber via the one or more apertures, and wherein the cavity defines a recirculation path configured to allow the fluid to recirculate from within the second chamber to the inlet of the second chamber.

Example 5: the compressor of example 4, wherein the cavity defines a cross-sectional area for the recirculation path about three to eight times a cross-sectional area of at least one aperture of the one or more apertures.

Example 6: the compressor of example 4, wherein the cavity defines only smooth angles along the recirculation path.

Example 7: the compressor of any of examples 1-6, wherein the one or more apertures form an obtuse angle with respect to a path of fluid flow at the inlet of the second chamber.

Example 8: the compressor of any of examples 1-7, wherein the one or more apertures comprise one or more slots in a second outer wall disposed radially outwards of the second impeller along a circumference of the second outer wall.

Example 9: the compressor of any of examples 1-8, wherein the one or more apertures comprise a single slot in a second outer wall disposed radially outwards of the second impeller along the entirety of a circumference of the second outer wall.

Example 10: the compressor of any of examples 1-9, wherein the one or more apertures comprises a plurality of apertures in a second outer wall disposed radially outwards of the second impeller, and wherein the compressor further comprises a plurality of ribs in the second outer wall between each of the plurality of apertures.

Example 11: the compressor of example 10, wherein the plurality of ribs comprises at least 3 ribs.

Example 12: the compressor of any of examples 1-11, further comprising: a cavity disposed radially outwards of a second outer wall disposed radially outwards of the second impeller, wherein the cavity is fluidically connected to the second chamber via the one or more apertures, wherein the cavity defines a recirculation path configured to allow the fluid to recirculate from within the second chamber to the inlet of the second chamber, and wherein the one or more apertures comprises a single slot in the second outer wall along the entirety of a circumference of the second outer wall; and a plurality of ribs extending radially outward from the second outer wall through the recirculation path.

Example 13: the compressor of any of examples 1-12, wherein the second impeller comprises a plurality of blades arranged circumferentially around the second impeller, and wherein the one or more apertures are arranged circumferentially in the wall of the second chamber such that, as the second impeller revolves around the longitudinal axis, at least a portion of the one or more apertures is always disposed in a portion of the wall between each of the plurality of blades.

Example 14: the compressor of any of examples 1-13, wherein a second outer wall disposed radially outwards of the second impeller shrouds the second chamber from the inlet of the second chamber to an outlet of the second chamber and around a circumference of the second chamber.

Example 15: a vapor cooling system comprising: a condenser; an evaporator; an expansion device; and a compressor fluidically coupled to one of more of the condenser or the evaporator and to the expansion device to form a refrigerant circuit, wherein the compressor comprises: a first compressor wheel comprising: a first chamber configured to retain a medium; a first impeller disposed within the first chamber, wherein the first impeller is configured to revolve around a longitudinal axis of the compressor and within the first chamber; and a diffuser fluidically connected to the first chamber and configured to output the medium from the first chamber; and a second compressor wheel comprising: a second chamber disposed radially outwards of the first chamber relative to the longitudinal axis, wherein the second chamber is separated from the first chamber by a first outer wall of the first chamber, and wherein the second chamber is configured to receive the outputted medium from the first chamber; a second impeller disposed within the second chamber, wherein the second impeller is configured to revolve around the longitudinal axis of the compressor within the second chamber; and one or more apertures disposed in a wall of the second chamber, wherein the one or more apertures are configured to allow fluid to recirculate from within the second chamber to an inlet of the second chamber.

Example 16: the compressor of example 15, wherein the second impeller defines a meridional length from a leading edge of the second impeller to a trailing edge of the second impeller, and wherein the one or more apertures are disposed in the wall along the meridional length between ten and fifteen percent of the meridional length from the leading edge to the trailing edge.

Example 17: the compressor of any of examples 15 and 16, further comprising a cavity disposed radially outwards of a second outer wall disposed radially outwards of the second impeller, wherein the cavity is fluidically connected to the second chamber via the one or more apertures, and wherein the cavity defines a recirculation path configured to allow the fluid to recirculate from within the second chamber to the inlet of the second chamber.

Example 18: the compressor of any of examples 15-17, wherein the one or more apertures form an obtuse angle with respect to a path of fluid flow at the inlet of the second chamber.

Example 19: the compressor of any of examples 15-18, wherein the one or more apertures comprises a plurality of slots in a second outer wall disposed radially outwards of the second impeller along a circumference of the second outer wall, and wherein the compressor further comprises a plurality of ribs in the second outer wall between each of the plurality of apertures.

Example 20: the compressor of any of examples 15-19, wherein the one or more apertures comprise a single slot in a second outer wall disposed radially outwards of the second impeller along the entirety of a circumference of the second outer wall.

Various examples of the disclosure have been described. These and other examples are within the scope of the following claims.