Patent Application
20170022984
The invention relates to a compressor, and more specifically to a compressor having a porous flow controller configured to meter a return flow of liquid oil from a high pressure side of the compressor to a low pressure side of the compressor.
Compressors used in refrigeration and air conditioning systems such as swashplate type compressors and scroll compressors, for example, typically include a lubricating oil mist suspended in a gaseous refrigerant medium. Such compressors are often employed in automotive air conditioning systems. In a typical automotive air conditioning system, the oil-refrigerant mixture enters the compressor through a suction port and is compressed therein. The compressed, high pressure oil-refrigerant mixture exits the compressor through a discharge port to travel through a refrigeration circuit before returning to the suction port to begin another cycle through the compressor and the refrigeration circuit.
Although the oil circulates through the entire refrigeration circuit, it is only needed in the compressor to lubricate the moving parts therein. Oil that remains suspended in the refrigerant as it travels throughout the refrigeration circuit can reduce the performance of the refrigeration circuit. For example, oil that travels through a heat exchanger in the refrigeration circuit is known to wet internal surfaces of the heat exchanger. Such a heat exchanger may function as an evaporator or a condenser of the refrigeration system, for example. Oil disposed on the internal surfaces of the heat exchanger reduces the heat transfer rate between the heat exchanger and the refrigerant. Accordingly, the compressor and other components of the refrigeration or the air conditioning system must have additional capacity to overcome the reduced heat transfer rate caused by oil flowing throughout the refrigeration circuit.
Also, oil that remains suspended in the refrigerant flowing through the refrigeration circuit is not available to lubricate the moving parts of the compressor. The compressor is susceptible to increased wear and seizure potential as a result of the reduced amount of available lubricating oil.
To combat these problems, an oil separator can be added to the compressor to facilitate separation of the oil from the refrigerant before the refrigerant exits the compressor. As a non-limiting example, the oil separator may be a centrifugal type separator that separates the oil from the refrigerant by causing the oil and refrigerant mixture to follow a curved flow path such as following the interior surface of a substantially cylindrical chamber. A swirling movement of the refrigerant and oil mixture applies a centrifugal force on the oil in the mixture, thereby separating the heavier oil from the gaseous refrigerant. Such an oil separator is disclosed in U.S. Patent Application Publication No. 2010/0101269, the entire disclosure of which is hereby incorporated herein by reference. Once the oil has been separated from the refrigerant, the oil may be caused to flow to a sump or other similar collecting means whereby the oil can be reintroduced into the suction side of the compressor.
The single orifice formed between and fluidly coupling the high pressure side 82 to the low pressure side 81 of the compressor 80 allows the liquid oil to flow back to the low pressure side 81 for subsequent lubrication of the internal components of the compressor such as the reciprocating pistons of a swash-plate type compressor, for example. However, the introduction of such an orifice also provides an additional flow path between the high pressure side 82 and the low pressure side 81 of the compressor 80, potentially allowing the recently compressed refrigerant having an increased pressure to flow through the orifice and back to the low pressure side 81 of the compressor 80 having a lower pressure, thereby reducing an efficiency of the compressor 80.
Such an orifice is typically selected to be narrow enough to cause the oil flowing therethrough to experience a desired pressure drop while also preventing a large amount of the gaseous refrigerant from flowing through the orifice and back to the low pressure side 81 of the compressor 80. However, the relative narrowness of the single orifice may present the problem of debris within the high pressure side 82 of the compressor 80 flowing to and clogging the single orifice, thereby preventing recirculation of the oil within the compressor 80. Accordingly, a filter 86 may be installed immediately upstream of the single orifice to filter out any debris having the potential to enter the low pressure side 81 of the compressor 80 or potentially clog the single orifice. Accordingly, the introduction of the single relatively small orifice adds cost and complexity to the oil metering process by requiring that an additional component in the form of the filter 86 be installed upstream of the single orifice. Furthermore, the insert 85 having the single orifice is typically formed as a precision machined part that is disposed within the conduit 84. Such precision machined parts add further cost and complexity in manufacturing the compressor having the single orifice for metering the flow of the oil.
It would therefore be desirable to produce a low cost porous part acting as both a filter element and a flow controller for metering a flow of liquid oil from the high pressure side of the compressor to the low pressure side of the compressor.
Compatible and attuned with the present invention, a porous flow controller for metering a flow of liquid oil from a high pressure side to a low pressure side of a compressor while also acting as a filter has surprisingly been discovered.
In one embodiment of the invention, a compressor comprises a housing having a hollow interior for communicating a fluid therethrough, the hollow interior of the housing divided into a low pressure side and a high pressure side. The compressor further comprises a porous flow controller fluidly coupling the high pressure side to the low pressure side. The porous flow controller is configured to meter a flow of the fluid from the high pressure side to the low pressure side.
In another embodiment of the invention, a compressor comprises a housing having a hollow interior for communicating a fluid comprising a mixture of a gas and a lubricant therethrough, the hollow interior of the housing divided into a low pressure side and a high pressure side. The compressor further comprises a compression mechanism, wherein the low pressure side is disposed upstream of the compression mechanism and the high pressure side is disposed downstream of the compression mechanism. The compressor further comprises a porous flow controller fluidly coupling the high pressure side to the low pressure side. The porous flow controller is configured to meter a flow of the liquid from the high pressure side to the low pressure side. An oil separator is disposed in the high pressure side of the housing.
A method of operating a compressor is also disclosed, the method comprising the steps of: providing a compressor having a housing with a hollow interior for communicating a fluid mixture of a gas and a lubricant therethrough, the hollow interior of the housing divided into a low pressure side and a high pressure side; separating at least a portion of the lubricant from the fluid mixture within the high pressure side; and metering a flow of the at least a portion of the lubricant from the high pressure side to the low pressure side through a porous flow controller.
The above, as well as other objects and advantages of the invention, will become readily apparent to those skilled in the art from reading the following detailed description of a preferred embodiment of the invention when considered in the light of the accompanying drawings:
The following detailed description and appended drawings describe and illustrate various embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner. In respect of the methods disclosed, the steps presented are exemplary in nature, and thus, the order of the steps is not necessary or critical.
An interior of the housing 2 may be divided into a low pressure side 5 and a high pressure side 6. The phrase “low pressure side” refers to any opening, void, chamber, or other fluid communicating passageway forming a hollow interior of the housing 2 and disposed upstream of the compression mechanism 10 in a direction of a flow of the fluid mixture through the interior of the housing 2. The low pressure side 5 of the housing 2 may also commonly be referred to as a suction side of the housing 2, as desired. The low pressure side 5 of the interior of the housing 2 may include a low pressure compartment 11 disposed upstream of and in fluid communication with a compression chamber 13 formed in the housing 2, wherein the compression chamber 13 is a portion of the housing 2 having the compression mechanism 10 disposed therein. The phrase “high pressure side” refers to any opening, void, chamber, or other fluid communicating passageway forming a hollow interior of the housing 2 and disposed downstream of the compression mechanism 10 in the direction of flow of the fluid mixture through the interior of the housing 2. The high pressure side 6 of the housing 2 may also commonly be referred to as a discharge side of the housing 2, as desired. The high pressure side 6 of the interior of the housing 2 may include a high pressure compartment 12 disposed downstream of and in fluid communication with the compression chamber 13 having the compression mechanism 10 disposed therein. As should be understood, a pressure of the fluid mixture is increased by the compression mechanism 10, hence the fluid mixture will have a higher pressure when flowing through the high pressure side 6 of the compressor 1 than it does when flowing through the low pressure side 5 of the compressor 1.
The swashplate type compressor 1 illustrated in
It should be understood that the low pressure compartment 11 and the high pressure compartment 12 may be included in any type of compressor 1 in addition to the swashplate type compressor illustrated in
The oil separator 20 is disposed within the interior of the housing 2 on the high pressure side 6 thereof and downstream of the compression mechanism 10 in the direction of fluid flow. The oil separator 20 may for instance be disposed in a chamber 50 formed within the high pressure side 6 of the housing 2 downstream of and in fluid communication with the high pressure compartment 12, as best shown in
The oil separator 20 may be any known or yet unknown feature or component disposed within housing 2 of the compressor 1 and suitable for separating the liquid oil from the gaseous refrigerant in which it is suspended. For example, the oil separator 20 may be a centrifugal type oil separator wherein the fluid is caused to flow in a circular or swirled pattern to cause the heavier oil to be forced outwardly toward an inner wall of the housing 2 in comparison to the gaseous refrigerant, thereby separating a quantity of the oil from the refrigerant. One exemplary centrifugal type oil separator is disclosed in U.S. Pat. No. 7,060,122 to Bhatia et al., hereby incorporated herein by reference in its entirety, which discloses an oil separator comprising an impingement surface formed on an inner wall of the housing. The inner wall is curved to cause the fluid flowing therethrough to have a substantially spiral-shaped flow path, thereby causing the fluid to strike the inner wall of the housing as it spirals through the oil separator.
Another exemplary oil separator is disclosed in U.S. Pat. Appl. Publ. No. 2010/0101269 to Theodore, J R et al. (hereinafter “the Theodore document”), hereby incorporated herein by reference in its entirety.
Other forms of oil separators in addition to the centrifugal type separators described hereinabove may be used while remaining within the scope of the present invention. For example, the oil separator 20 may be a horizontal type oil separator or a vertical type oil separator, as desired. The oil separator 20 may also include a textured surface to increase a surface area of the oil separator exposed to the fluid mixture, thereby promoting increased separation of the liquid oil from the fluid mixture. The oil separator 20 may for example include a knurled surface or an anodized surface, as desired. In all cases, the oil separator 20 must be capable of separating at least a portion of the liquid oil from the fluid mixture to allow the liquid oil to accumulate at a desired position within the housing 2 of the compressor 1, as described in greater detail hereinafter.
The oil separator 20 may be positioned within the housing 2 in a variety of different locations and at a variety of different orientations, depending on the type of compressor used, the relative positioning of the components thereof, and the desired flow characteristics of the fluid being compressed by the compressor 1. For example, in some embodiments, the chamber 50 having the oil separator 20 disposed therein may be formed in the housing 2 immediately between and in direct fluid communication with each of the low pressure compartment 11 and the high pressure compartment 12. In other embodiments, the chamber 50 having the oil separator 20 disposed therein may be formed at a periphery of the housing 2 within a conduit or other passageway routed to be in fluid communication with each of the low pressure compartment 11 and the high pressure compartment 12 by means of conduits or other fluid flow paths, as desired. As shown in
The chamber 50 having the oil separator 20 disposed therein may include a mixture inlet 52, a gas outlet 54, and an oil outlet 56. The mixture inlet 52 provides fluid communication between the compression mechanism 10 and the chamber 50. The mixture inlet 52 may provide direct fluid communication between the chamber 50 and the high pressure compartment 12, for example. As shown in
Each of the mixture inlets 52 may be positioned and oriented in a manner wherein the fluid mixture is directed through each of the mixture inlets 52 and toward a separating means of the oil separator 20. For example, each of the mixture inlets 52 illustrated in
The oil outlet 56 may be formed in the housing 2 at a position wherein the accumulated liquid oil separated out of the fluid mixture may enter the oil outlet 56 and proceed on to the low pressure side 5 of the interior of the housing 2. Accordingly, the oil outlet 56 may be formed in the housing 2 at a position wherein the liquid oil is caused to flow following its separation from the gaseous refrigerant. For example, with reference to
The oil outlet 56 may be a conduit or passageway fluidly coupling the chamber 50 to the low pressure side 5 of the interior of the housing 2. The oil outlet 56 may fluidly couple the chamber 50 to the low pressure compartment 11, for example. The porous flow controller 40 is disposed within the oil outlet 56 to extend across an entirety of the cross-section thereof. For example, if the oil outlet 56 has a substantially circular cross-section, the porous flow controller 40 will have a substantially cylindrical or disk-like shape, as shown in
In the embodiment shown, the porous flow controller 40 is formed from sintered metal powder. The metal powder may be any metal powder suitable for undergoing a sintering process. Suitable metal powder materials may include metals and metal alloys such as aluminium, brass, 316L stainless steel, 304L stainless steel, low alloy carbon steel, and plain carbon steel, as non-limiting examples. The porous flow controller 40 may be formed to have a desired degree of porosity by pre-selecting each of a size and a shape of the metal powder grains undergoing the sintering process, a compression force applied to the metal powder grains, and a temperature and a time at which the sintering process is carried out. Accordingly, the completed porous flow controller 40 may be formed to have a desired degree of porosity wherein a fluid may be communicated therethrough by means of a plurality of fluid flow paths formed by the cooperation of the interconnected pores. The interconnectedness of the pores and the size of the pores formed within the porous flow controller 40 may also be preselected to promote desirable flow characteristics of a fluid passing therethrough. It should be understood that the porous flow controller 40 should have a porosity sufficient to allow a fluid such as the liquid oil accumulated in the chamber 50 to pass through the porous flow controller 40 from one end thereof to an opposite end thereof.
Although the porous flow controller 40 has been described as being formed in a sintering process using a metal powder material, it should be understood that other forms of porous elements capable of communicating a fluid therethrough may also be used without departing from the scope of the present invention. For example, the porous flow controller 40 may be formed by a plurality of particles formed into a porous structure by means of a bonding process such as adhesive bonding. Alternatively, the porous flow controller 40 may be formed by a plurality of interconnected pores formed in a solid material by a liquid foaming or replication casting process, as desired. Such processes may include the introduction of gases or the removal of solids from a liquid or molten material in order to create pore spaces within the molten material once the molten material has cured or solidified. Furthermore, in place of particles or grains, the material forming the porous flow controller 40 may comprise a plurality of fibers interconnected in a manner that creates a porous structure. Additionally, the particles, grains, or fibers forming the porous flow controller 40 may also be formed from a ceramic, a glass (e.g. glass flits), or a polymer, including both thermoset and thermoplastic polymers, as desired. A material and method used to form the porous flow controller 40 may be selected to ensure that the grains, particle, or fibers comprising the porous flow controller 40 are not caused to disassociate from the porous flow controller 40 during use thereof to prevent such materials from wearing or clogging any other components of the compressor 1.
The porous flow controller 40 may include a coupling structure formed thereon for coupling the porous flow controller 40 to the housing 2 of the compressor 1. The coupling means may for example be threading formed on the porous flow controller 40 configured to cooperate with threading formed on an interior wall of the housing 2 forming the oil outlet 56. In other embodiments, the porous flow controller 40 may advantageously be produced to not have a coupling means formed thereon due to the porous flow controller 40 being capable of being formed to have any suitable shape or size for extending across the cross-section of the oil outlet 56. The porous flow controller 40 may for instance have a shape and size suitable for being press-fit into the oil outlet 56. For example, the porous flow controller 40 illustrated in
In use, the fluid mixture of liquid oil and gaseous refrigerant is first caused to enter the compressor 1 through the suction port thereof before then entering the low pressure compartment 11. As shown in
The liquid mixture comprising the gaseous refrigerant and an increased percentage of the oil then flows into the chamber 50 having the oil separator 20 disposed therein through each of the mixture inlets 52. Each of the mixture inlets 52 may be positioned relative to the oil separator 20 to cause the fluid mixture to encounter the oil separator 20 before the fluid mixture exits the chamber 50, As illustrated in
While the fluid mixture having a lowered percentage of the oil suspended therein exits the chamber 50 through the gas outlet 54 the oil may simultaneously be caused to accumulate at or to flow towards the oil outlet 56. Depending on the configuration of the housing 2 and the shape of the chamber 50, the oil may be caused to flow to the oil outlet 56 by means of gravity feeding or by means of the flow of the fluid mixture forcing the oil in a direction towards the oil outlet 56. As explained hereinabove, the chamber 50 may also include one or more sumps or reservoirs for accumulating the oil or may include one or more passageways leading to secondary chambers for accumulating the oil.
The accumulated liquid oil flows into the oil outlet 56 where it encounters the porous flow controller 40 disposed therein. The porous flow controller 40 has a pre-selected porosity to allow a pre-selected mass flow rate of the liquid oil to pass therethrough. A mass flow rate of the liquid oil through the porous flow controller 40 may be estimated by the following equation:
wherein m is the mass flow rate through the porous flow controller 40, k is the permeability of the porous flow controller 40, μ is the kinematic viscosity of the fluid flowing through the porous flow controller 40, (dp/dx) is the pressure gradient in a direction of flow of the fluid through the porous flow controller 40, A is the flow cross-sectional area through the porous flow controller 40, and ρ is the density of the fluid flowing through the porous flow controller 40.
The permeability k and the pressure gradient (dp/dx) of the porous flow controller 40 may be a function of a porosity of the porous flow controller 40 as well as the flow tortuosity of the fluid flow paths formed within the porous flow controller 40. Accordingly, the porous flow controller 40 may be formed in a sintering process to have a pre-selected value of permeability k and pressure gradient (dp/dx) by varying factors such as the size and shape of the grains being sintered, the pressure applied to the grains during compaction, and the temperature and the time of the sintering process. Furthermore, the liquid oil used to lubricate the compressor 1 is selected to have known values of kinematic viscosity μ and density ρ. Accordingly, the mass flow rate m of the fluid through the porous flow controller 40 may be selected by varying one or both of the cross-sectional area A and a length of the porous flow controller 40 in a direction of the flow therethrough. The size and shape of the porous flow controller 40 may therefore be selected to produce both a desired mass flow rate m of the liquid oil through the porous flow controller 40 as well as a desired pressure drop in the liquid oil as it passes from the high pressure side 6 to the low pressure side 5 of the housing 2. As such, the size and shape of the porous flow controller 40 may be selected to correspond to a desired operating pressure range of the compressor 1 and to maintain a desired flow rate of the liquid oil to the low pressure side 5 of the housing 2.
The plurality of fluid flow paths formed through the porous flow controller 40 allows the compressor 1 to be produced without requiring an additional filter element placed between the high pressure side 6 and the low pressure side 5 of the housing 2. Such filter elements are typically disposed immediately upstream of a narrow orifice connecting the high pressure side to the low pressure side, wherein the orifice is relatively narrow to prevent a large quantity of the gaseous refrigerant included in the fluid mixture from returning to the low pressure side instead of proceeding to a discharge port of the compressor. The narrowness of the orifice may allow small debris circulating through the compressor to entirely clog the orifice and prevent the return of the lubricating liquid oil to the interior components of the compressor, hence a filter element must be placed upstream of the orifice to ensure continued operation of the compressor. In contrast, the plurality of fluid flow paths allow the porous flow controller 40 to also function as a filter element because even if one or more of the distinct fluid flow paths formed therein is clogged by debris, the liquid oil may still flow around the debris via the unclogged portions of adjacent fluid flow paths. Accordingly, the inclusion of the porous flow controller 40 between the low pressure side 5 and the high pressure side 6 advantageously allows for the compressor 1 to be manufactured without the inclusion of a filter element disposed upstream of the orifice in a direction of a flow of the liquid oil through the oil outlet 56, thereby reducing a cost and complexity of manufacturing the compressor 1. The porous flow controller 40 therefore allows for the flow of the liquid oil to travel directly from the high pressure side 6 to the low pressure side 5 while minimizing an incidence of the gaseous refrigerant flowing back to the low pressure side 5 through the porous flow controller 40.
The ability of the porous flow controller 40 to easily be manufactured to have a pre-selected shape, size, and permeability also advantageously allows for the porous flow controller 40 to be adapted for use with a large variety of different compressors having different configurations and operating parameters. For example, the porous flow controller 40 may be selected to have desirable characteristics based on a flow rate of the liquid oil through the porous flow controller 40, a difference in pressure between the high pressure side 6 and the low pressure side 5, and a configuration of the relevant components of the compressor 1. The porous flow controller 40 may be formed to have a cross-sectional shape suitable for extending across any existing conduit used to fluidly couple the high pressure side 6 to the low pressure side 5 of a given compressor 1, thereby allowing the porous flow controller 40 to be manufactured to be press-fit into such a conduit without the formation of additional coupling means on the porous flow controller 40. The porous flow controller 40 may also be formed to have a size, shape, and permeability sufficient to impart a desired pressure drop to the liquid oil as it passes from the high pressure side 6 to the low pressure side 5 of the housing 2, thereby allowing for a controlled metering of the liquid oil based on the operating parameters of the compressor 1 such as the difference in pressure of the fluid mixture between the high pressure side 6 and the low pressure side 5.
The use of the porous flow controller 40 may also allow for a smaller quantity of the oil to be present in the fluid mixture because a smaller quantity of the oil is caused to exit the compressor 1 due to the precise metering of the oil by the porous flow controller 40. A reduction of the quantity of oil exiting the compressor 1 may improve an efficiency of other components included in a refrigeration circuit having the compressor 1 because refrigerant devoid of the oil has a greater heat exchange capacity than does the fluid mixture.
From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications to the invention to adapt it to various usages and conditions.
