This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
HVAC&R systems are used in a variety of settings and for many purposes. For example, HVAC&R systems may include a vapor compression refrigeration cycle (e.g., a refrigerant circuit having a condenser, an evaporator, a compressor, and/or an expansion device) configured to condition an environment. The vapor compression refrigeration cycle may include a compressor that is configured to direct refrigerant through various components of the refrigerant circuit. In some cases, a pressure of refrigerant at various positions along the refrigerant circuit may fluctuate during operation of the vapor compression refrigeration cycle. Accordingly, a compression ratio (e.g., a ratio between a low or suction pressure and a high or discharge pressure) of the compressor may be adjusted to maintain operating parameters of the vapor compression refrigeration cycle at target levels. To adjust the compression ratio of the compressor, a speed of one or more rotors of the compressor may be adjusted via a motor or another suitable drive. Additionally, a volume ratio of the compressor may be adjusted based on the compression ratio to maintain a performance of the compressor.
Existing compressors may be configured to adjust the volume ratio in response to a given compression ratio via stepwise control of a piston between one or more positions. Additionally or alternatively, a proportional valve may be utilized to supply a fluid into a piston chamber to adjust the position of the piston. Unfortunately, existing techniques for controlling the volume ratio of the compressor may be limited based on the finite number of positions of the piston and/or may increase costs by including additional components, such as the proportional valve and corresponding control devices.
In an embodiment of the present disclosure, a volume ratio control system for a compressor includes a chamber formed within a housing of the compressor, where the chamber is in fluid communication with a high pressure side of the compressor, a piston disposed within the chamber, where the piston includes a cavity in fluid communication with a low pressure side of the compressor, and a biasing device disposed within the chamber and configured to enable movement of the piston in response to a pressure differential between the low pressure side of the compressor and the high pressure side of the compressor falling below a threshold value.
In another embodiment of the present disclosure, a heating, ventilation, air conditioning, and/or refrigeration (HVAC&R) system includes a compressor configured to circulate a refrigerant through a refrigerant circuit and a volume ratio control system configured to adjust a volume ratio of the compressor. The volume ratio control system includes a chamber formed in a housing of the compressor and in fluid communication with a high pressure side of the compressor, a piston disposed within the chamber, where the piston includes a cavity in fluid communication with a low pressure side of the compressor, and a biasing device disposed within the cavity, where the biasing device is configured to enable movement of the piston in response to a pressure differential between the low pressure side of the compressor and the high pressure side of the compressor falling below a threshold value.
In a further embodiment of the present disclosure, a volume ratio control system for a compressor includes a chamber formed within a housing of the compressor, where the chamber includes a first portion in fluid communication with a high pressure side of the compressor and a second portion in fluid communication with a low pressure side of the compressor and a rod extending through an opening of the housing separating the first portion and the second portion of the chamber, where the rod is fixed within the chamber with respect to an axis defining a length of the chamber. The volume ratio control system also includes a piston disposed within the first portion of the chamber, where the piston includes a cavity in fluid communication with the second portion of the chamber, and where the rod is configured to be at least partially disposed within the cavity of the piston, and a biasing device disposed within the cavity between the rod and an interior surface of the piston, where the biasing device is configured to enable movement of the piston in response to a pressure differential between the low pressure side of the compressor and the high pressure side of the compressor falling below a threshold value.
One or more specific embodiments of the present disclosure will be described below. These described embodiments are only examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
As discussed above, a vapor compression refrigeration cycle may include a compressor that is configured to circulate a refrigerant through a refrigerant circuit of the vapor compression refrigeration cycle. In some cases, various operating parameters of the refrigerant may fluctuate during operation of the vapor compression refrigeration cycle. A compression ratio of the compressor may be adjusted in order to maintain and/or adjust operating parameters of the refrigerant within the refrigerant circuit toward target levels. The compression ratio of the compressor may be controlled via a motor that supplies torque to one or more rotors of the compressor. Therefore, an operating speed of the motor is adjusted in order to control the compression ratio to be a target value. Further, a volume ratio of the compressor may be adjusted based on the compression ratio in order to maintain a performance (e.g., an efficiency) of the compressor during operation. Indeed, in some cases, an amount of refrigerant drawn into the compressor may exceed an amount that achieves the target compression ratio. Accordingly, the volume ratio may be adjusted by enabling refrigerant to bypass a compression portion of the compressor in order to reduce the volume ratio. Similarly, an amount of refrigerant drawn into the compressor may be less than an amount that achieves the target compression ratio. In such instances, the volume ratio may be adjusted by blocking refrigerant from bypassing the compression portion in order to increase the volume ratio of the compressor.
Existing compressors may control the volume ratio of the compressor using a piston that may be adjusted to a finite number of positions. For example, the piston may be in fluid communication with a high pressure side of the compressor to enable the refrigerant to bypass the compression portion of the compressor based on the position of the piston. Further, some existing compressors may include a proportional valve that directs a working fluid toward a piston chamber to generate movement of the piston, thereby providing control over the position of the piston. However, such existing systems may be limited in controlling the volume ratio and/or may increase costs of the vapor compression refrigeration cycle.
As such, embodiments of the present disclosure are directed to an improved volume ratio control system that may enhance control of the volume ratio of the compressor without including relatively expensive components. For instance, the volume ratio control system of the present disclosure may include a biasing device, such as a spring, to control a position of a piston disposed within a chamber of the compressor. The chamber and/or the piston may be in fluid communication with both a low pressure portion (e.g., suction side) of the compressor and a high pressure portion (e.g., discharge side) of the compressor, such that a pressure differential is generated within the chamber and/or across the piston. Under some operating conditions, the pressure differential within the chamber and/or across the piston may exceed a threshold, thereby causing the piston to move in a first direction to adjust the volume ratio of the compressor (e.g., increase the volume ratio of the compressor in response to an increase in compression ratio). When the pressure differential falls below the threshold, the biasing device may cause the piston to move in a second direction, opposite the first direction, to adjust the volume ratio of the compressor (e.g., decrease the volume ratio of the compressor in response to a reduction in compression ratio). The piston may be configured to move in the second direction to expose openings that enable refrigerant to bypass a compression portion (e.g., at least a portion of a compression chamber) of the compressor, such that the volume ratio is reduced when the piston exposes or does not cover the openings. Similarly, the volume ratio of the compressor may be increased when the piston moves in the first direction to cover and/or block the openings, thereby reducing the amount of refrigerant that bypasses the compression portion. The volume ratio control system of the present disclosure is thus a passive system that utilizes the pressure differential within the chamber and a biasing force applied to the piston by the biasing device in order to adjust the volume ratio of the compressor. Indeed, the volume ratio control system may be infinitely variable, such that the piston may move toward virtually any position within the chamber and is not limited to predetermined or discrete positions.
Turning now to the drawings,
In some embodiments, the vapor compression system 14 may use one or more of a variable speed drive (VSDs) 52, a motor 50, the compressor 32, the condenser 34, the expansion valve or device 36, and/or the evaporator 38. The motor 50 may drive the compressor 32 and may be powered by a variable speed drive (VSD) 52. The VSD 52 receives alternating current (AC) power having a particular fixed line voltage and fixed line frequency from an AC power source, and provides power having a variable voltage and frequency to the motor 50. In other embodiments, the motor 50 may be powered directly from an AC or direct current (DC) power source. The motor 50 may include any type of electric motor that can be powered by a VSD or directly from an AC or DC power source, such as a switched reluctance motor, an induction motor, an electronically commutated permanent magnet motor, or another suitable motor.
The compressor 32 compresses a refrigerant vapor and delivers the vapor to the condenser 34 through a discharge passage. In some embodiments, the compressor 32 may be a screw compressor. The compressor 32 includes a fluid (e.g., oil) that lubricates components of the compressor. The refrigerant vapor delivered by the compressor 32 to the condenser 34 may transfer heat to a cooling fluid (e.g., water or air) in the condenser 34. The refrigerant vapor may condense to a refrigerant liquid in the condenser 34 as a result of thermal heat transfer with the cooling fluid. The refrigerant liquid from the condenser 34 may flow through the expansion device 36 to the evaporator 38. In the illustrated embodiment of
The refrigerant liquid delivered to the evaporator 38 may absorb heat from another cooling fluid, which may or may not be the same cooling fluid used in the condenser 34. The refrigerant liquid in the evaporator 38 may undergo a phase change from the refrigerant liquid to a refrigerant vapor. As shown in the illustrated embodiment of
As discussed above, embodiments of the present disclosure are directed to an improved volume ratio control system for a compressor, such as the compressor 32. The volume ratio control system may include a piston and a rod (e.g., a stationary rod) disposed within a chamber of the compressor. The piston may be disposed within at least a portion of the chamber that is exposed to a high pressure side of the compressor. For example, the high pressure side may be a discharge side of the compressor, such that an exterior surface of the piston is also exposed to the discharge side of the compressor (e.g., a discharge pressure of the compressor). In some embodiments, the exterior surface of the piston may be additionally or alternatively be exposed to an oil pressure of the compressor. Further, a cavity of the piston may be in fluid communication with a low pressure side of the compressor. For example, the low pressure side may be a suction side of the compressor (e.g., a suction pressure of the compressor), thereby exposing an interior surface of the piston to the suction side of the compressor. As such, a pressure differential force may be applied to the piston as opposing pressure forces applied to the exterior surface and the interior surface of the piston vary. The pressure differential force may at least partially control a position of the piston with respect to the chamber and/or the rod. Additionally, a biasing device, such as a spring, may be disposed in the cavity between the piston and the rod. The biasing device may direct movement of the piston (e.g., with respect to the rod) when the pressure differential force falls below a threshold value. As used herein, the threshold value of the pressure differential force may be a function of a biasing force of the biasing device and/or a position of the piston within the chamber (and/or with respect to the rod). Indeed, the threshold value of the pressure differential force may change based at least on a current length and/or a current level of extension of the biasing device. For instance, the biasing force exerted by the biasing device may change as the biasing device extends and/or contracts from a natural or unbiased position (e.g., the biasing force increases as the biasing device moves further from the natural or unbiased position).
In any case, the volume ratio control system of the present disclosure is passive in that the volume ratio control system adjusts the volume ratio of the compressor as a result of the pressure differential established between the chamber and the cavity of the piston, which may be indicative of the compression ratio of the compressor. In other words, additional mechanical components, such as valves, motors, and/or other devices, may not be included to adjust the volume ratio of the compressor. Further, the volume ratio control system is generally infinitely variable because a position of the piston within the chamber is not limited to stepwise or predetermined positions. Therefore, the volume ratio control system enables accurate and/or precise volume ratio control of the compressor without including relatively expensive components that add costs to the vapor compression system 14.
For example,
As shown in the illustrated embodiment of
The volume ratio control system 102 is configured to adjust an amount of the refrigerant within the compressor 100 that flows through the openings 110 and bypasses at least the portion 114 of the compression chamber 109. For example, the volume ratio control system 102 includes a piston 116 (e.g., an annular piston) disposed within a chamber 118 formed into the housing 112. The chamber 118 may be in fluid communication with the openings 110 and may extend into a first portion 120 of the housing 112 that is proximate to the low pressure side 104. Additionally, the chamber 118 may extend into a second portion 122 of the housing 112 that is proximate to the high pressure side 106. In any case, the piston 116 is configured to move within the chamber 118 to block and/or expose the openings 110 to control the amount of refrigerant bypassing the portion 114 of the compression chamber 109.
As is described in further detail herein, movement of the piston 116 within the chamber 118 may be passively controlled by a biasing device 124 (e.g., a spring) and/or a pressure differential between a cavity 126 formed within the piston 116 (e.g., fluidly coupled to the low pressure side 104 of the compressor 100, such as via ports, conduits, etc.) and at least a portion 128 of the chamber 118 (e.g., fluidly coupled to the high pressure side 106 of the compressor 100, such as via a discharge line 135). In some embodiments, the volume ratio control system 102 includes a rod 129 (e.g., a stationary rod) disposed within the chamber 118 and within the cavity 126 of the piston 116. As shown in the illustrated embodiment of
In any case, the biasing device 124 and the pressure differential between the cavity 126 and the portion 128 of the chamber 118 may enable movement of the piston 116 within the chamber 118 and/or with respect to the rod 129. For instance, the cavity 126 may include a relatively low pressure associated with refrigerant entering the compressor 100 on the low pressure side 104, whereas the portion 128 of the chamber 118 may include a relatively high pressure associated with refrigerant exiting the compressor 100 on the high pressure side 106. The pressure differential between the cavity 126 and the portion 128 of the chamber 118 may direct movement of the piston 116 within the chamber 118 upon reaching and/or exceeding a threshold pressure differential (e.g., a variable pressure differential threshold). For example, when the pressure differential is at and/or exceeds the threshold pressure differential, a force is exerted on the piston 116 to direct movement of the piston 116 in a first direction 130 along an axis 132 defining a length 134 (see, e.g.,
Further, the biasing device 124 exerts a force on the piston 116 that may direct movement of the piston 116 in a second direction 136, opposite the first direction 130, along the axis 132 when the pressure differential between the cavity 126 and the portion 128 falls below the pressure differential threshold (e.g., a variable pressure differential threshold). For example, the biasing device 124 may include target parameters that apply a target biasing force on the piston 116 at various positions within the chamber 118 to enable movement of the piston 116 in the second direction 136 when the pressure differential between the cavity 126 and the portion 128 falls below the pressure differential threshold for the given position of the piston 116 within the chamber 118. Parameters of the biasing device 124 that may be selected or modified to achieve a desired biasing force or range of biasing forces may include a material (e.g., metal, polymer) of the biasing device 124, a coil diameter of the biasing device 124, an internal diameter of the biasing device 124, an external diameter of the biasing device 124, a coil pitch of the biasing device 124, a number of coils of the biasing device 124, a spring rate of the biasing device 124, a free length of the biasing device 124, a block length of the biasing device 124, another suitable parameter of the biasing device 124, or any combination thereof. In any case, the pressure differential between the cavity 126 and the portion 128 and the target biasing force of the biasing device 124 may passively direct movement of the piston 116 within the chamber 118 to adjust the volume ratio of the compressor 100.
Further, the rod 129 may form a seal between the additional portion 133 of the chamber 118 and the portion 128 of the chamber 118 to maintain a pressure differential that is substantially equal to a pressure differential between the low pressure side 104 and the high pressure side 106 of the compressor 100. In some embodiments, the rod 129 includes the passage 131 that enables fluid communication between the additional portion 133 of the chamber 118 and the cavity 126. Accordingly, a pressure within the cavity 126 may be substantially equal to the suction pressure of the compressor 100 (e.g., the additional portion 133 of the cavity 126 is exposed to the low pressure side 104 of the compressor 100). Additionally, the portion 128 of the chamber 118 may be fluidly coupled to the high pressure side 106 of the compressor 100 via the discharge line 135 and/or fluidly coupled to the openings 110.
Thus, a first pressure force (e.g., represented by arrow 156) may be applied to an interior surface 158 of the piston 116, where the first pressure force is indicative of the low (e.g., suction) pressure of the compressor 100. A second pressure force (e.g., represented by arrow 160) may be applied to an exterior surface 162 of the piston 116, where the second pressure force is indicative of the high (e.g., discharge, oil) pressure of the compressor 100. The first (e.g., low) pressure force is less than the second (e.g., high) pressure force, such that a pressure differential force (e.g., a difference between the first pressure force and the second pressure force) may be applied to the piston 116 in the first direction 130. Moreover, a biasing force (e.g., represented by arrow 164) may be applied to the piston 116 by the biasing device 124 in the second direction 136 opposite the first direction 130. Accordingly, when the pressure differential force exceeds the biasing force, the piston 116 moves in the first direction 130 toward an end 166 of the portion 128 of the chamber 118 that is proximate to the openings 110. The piston 116 may cover and/or block one or more of the openings 110, such that the volume ratio of the compressor 100 increases. Similarly, when the pressure differential force is less than the biasing force, the biasing device 124 enables the piston 116 to move in the second direction 136 away from the end 166 of the portion 128 of the chamber 118 proximate to the openings 110. Thus, one or more of the openings 110 may be exposed or uncovered, such that refrigerant may bypass the portion 114 of the compression chamber 109 and reduce the volume ratio of the compressor 100.
As shown in the illustrated embodiment, the piston 116 includes a first segment 168 and a second segment 170 that are each configured to move (e.g., jointly) in the first direction 130 and the second direction 136 within the portion 128 of the chamber 118. For example, the first segment 168 and the second segment 170 may be a single piece that forms the piston 116. The first segment 168 may include a first radial thickness 172 that is greater than a second radial thickness 174 of the second segment 170. In some embodiments, an overall diameter 176 of the piston 116 corresponds to a diameter 178 of the portion 128 of the chamber 118. For instance, the overall diameter 176 may be slightly less than the diameter 178 to enable the piston 116 to move along the axis 132 within the portion 128 of the chamber 118.
As shown in the illustrated embodiment of
In some embodiments, the biasing device 124 (e.g., a spring) may be disposed within the cavity 126 of the piston 116 between the rod 129 and an internal surface 186 of the piston 116. The rod 129 may be substantially stationary within the chamber 118, such that the piston 116 is configured to move along at least a portion of a length 188 of the rod 129. For example, the rod 129 may be coupled to the opening 150 of the chamber 118 separating the portion 128 and the additional portion 133. In some embodiments, the rod 129 may be coupled to the opening 150 via threads, as mentioned above, via bolts or other fasteners, via a weld, or via another suitable coupling technique that enables the rod 129 to maintain a position with respect to the chamber 118. Further, the biasing device 124 may be coupled to an end 190 of the rod 129, such as welded to the end 190, fastened to the end 190 via fasteners (e.g., screws, bolts, or other suitable fasteners), or coupled to the end 190 via another suitable technique. In any case, the biasing device 124 exerts a force on an end 192 of the piston 116 (e.g., such as the interior surface 158) in the second direction 136 or toward a natural position (e.g., unbiased position) of the biasing device 124. As the piston 116 is directed in the first direction 130, the biasing device 124 may compress against the end 188 of the rod 129 and exert a greater force on the piston 116. In some embodiments, the rod 129 may also act as a guide for the biasing device 124 as it compresses and decompresses due to variations in the pressure differential. For example, the biasing device 124 may be configured to move along an outer surface 194 of the rod 129 as the piston 116 moves within the portion 128 of the chamber 118. In any case, the pressure differential threshold that drives movement of the piston 116 may vary based on an amount of compression of the biasing device 124 and/or a current length of the biasing device 124 compared to a natural or unbiased length of the biasing device 124.
As the pressure differential between the cavity 126 and the portion 128 of the chamber 118 decreases, the biasing device 124 may direct the piston 116 to move in the second direction 136 by applying a force on the piston 116 in the second direction 136. For example,
As discussed above, an amount of force exerted on the piston 116 by the biasing device 124 may be based on a position of the piston 116 within the portion 128 of the chamber 118 relative to the axis 132, an amount of extension and/or compression of the biasing device 124, parameters of the basing device 124 itself, other suitable parameters, or any combination thereof. For instance, parameters of the biasing device 124 that may contribute to the magnitude of the biasing force applied to the piston 116 may include a material (e.g., metal, polymer) of the biasing device 124, a coil diameter of the biasing device 124, an internal diameter of the biasing device 124, an external diameter of the biasing device 124, a coil pitch of the biasing device 124, a number of coils of the biasing device 124, a spring rate of the biasing device 124, a free length of the biasing device 124, a block length of the biasing device 124, another suitable parameter of the biasing device 124, or any combination thereof.
In any case, both the pressure differential within the cavity 126 of the piston 116 and the portion 128 of the chamber 118 applying a force on the exterior surface 162 of the piston 116 in the first direction 130 and the biasing force applied to the piston 116 by the biasing device 124 in the second direction 136 control movement and the position of the piston 116 within the chamber 118. The pressure differential threshold for directing movement of the piston 116 in the first direction 130 may vary based on the position of the piston 116 and/or the level of extension and/or compression of the biasing device 124. As such, the piston 116 may be positioned (e.g., stationary) at virtually any location within the portion 128 of the chamber 118 relative to the axis 132 when the opposing forces applied by the pressure differential and the biasing device 124 are substantially equal. Thus, the volume ratio control system 102 of the present disclosure may enable infinitely or substantially infinitely variable control of the volume ratio of the compressor 100.
As set forth above, embodiments of the present disclosure may provide one or more technical effects useful in controlling a volume ratio of a compressor. For example, embodiments of the present disclosure are directed to an improved volume ratio control system that may operate passively and enable infinitely variable control of the volume ratio. The volume ratio control system may include a piston disposed within at least a portion of a chamber of the compressor that is fluidly coupled to a high pressure side (e.g., discharge side or oil pressure) of the compressor. The piston may include a cavity that is fluidly coupled to a low pressure side (e.g., suction side) of the compressor. Further, a rod and a biasing device may be disposed within the cavity of the piston. As the compressor operates, a pressure differential may be established between the cavity of the piston and the chamber. When the pressure differential exceeds a threshold, the pressure differential may exert a force on the piston in a first direction causing the piston to block or cover openings that enable refrigerant to bypass at least a portion of a compression chamber of the compressor. As such, a volume ratio of the compressor is increased. When the pressure differential falls below the threshold, the biasing device may apply a force to the piston in a second direction, opposite the first direction, to unblock or expose the openings. As such, the pressure ratio of the compressor is reduced. In any case, the volume ratio control system enables passive control of the volume ratio of the compressor, which reduces costs and also enhances control over the volume ratio of the compressor. The technical effects and technical problems in the specification are examples and are not limiting. It should be noted that the embodiments described in the specification may have other technical effects and can solve other technical problems.
While only certain features and embodiments of the invention have been illustrated and described, many modifications and changes may occur to those skilled in the art (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters (e.g., temperatures, pressures, etc.), mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described (i.e., those unrelated to the presently contemplated best mode of carrying out the invention, or those unrelated to enabling the claimed invention). It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation.
The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function] . . . ” or “step for [perform]ing [a function] . . . ”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).
This application is a U.S. National Stage Application of PCT International Application No. PCT/US2021/012451, entitled “VOLUME RATIO CONTROL SYSTEM FORA COMPRESSOR,” filed Jan. 7, 2021, which claims priority to and the benefit of U.S. Provisional Application No. 62/958,204, entitled “VOLUME RATIO CONTROL SYSTEM FOR A COMPRESSOR,” filed Jan. 7, 2020, each of which is hereby incorporated by reference in its entirety for all purposes.
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