Parallel compressor unit

Abstract

The invention provides a parallel compressor unit. The parallel compressor unit comprises a parallel unit and an oil separator, the parallel unit comprises two horizontal compressors which are connected in parallel; an air inlet of the oil separator is respectively connected with exhaust ports of the two horizontal compressors through branch pipes; an oil return port of the oil separator is connected with air suction ports of the two horizontal compressors in a one-to-one correspondence manner through two oil return pipelines; each oil return pipeline is provided with a slope structure enabling the axis of the pipeline to change in a fluctuating mode. According to the parallel compressor assembly, the gradient structure is arranged in the oil return channel, oil and condensed liquid refrigerants in exhausted gas of the running compressor are prevented from possibly flowing back into the stopped compressor due to gravity, and therefore the problem of oil shortage caused by the fact that lubricating oil of the running compressor is migrated to the stopped compressor is solved; the gradient structure of the oil return channel does not influence the balance of lubricating oil between the two compressors during operation, and the problem of oil shortage of the compressors is avoided.

Description

Technical Field

[0001] This invention relates to the field of compressor technology, and more specifically, to a parallel compressor unit. Background Technology

[0002] In industrial sectors such as refrigeration and air conditioning, parallel compressor units are widely used due to their ability to flexibly adjust capacity and improve system reliability and energy efficiency. However, these systems consistently face a critical and challenging technical problem during long-term operation—the reliable recovery and balanced distribution of refrigeration oil, i.e., the oil return problem.

[0003] Currently, this problem mainly manifests in two typical operating conditions. First, when the unit is operating under partial load or when only one compressor is under maintenance, often only one compressor is running. In this situation, a large amount of refrigerant oil migrates with the refrigerant circulation and gradually accumulates in the compressor and its connected piping, causing the oil level in the running compressor's oil sump to drop continuously, preventing sufficient lubricating oil return. If this "oil shortage on the operating side" is not corrected in time, it will directly lead to poor lubrication of internal moving parts of the compressor (such as bearings and scroll plates), resulting in abnormal mechanical wear, overheating, and even seizure, seriously threatening equipment safety and lifespan.

[0004] Secondly, even under full-load conditions with both compressors operating in parallel, the risk of uneven oil return still exists. Typically, systems are equipped with oil separators and shared return oil lines to collect and distribute lubricating oil. However, in actual operation, due to complex factors such as differences in resistance characteristics between parallel branches, installation differences, and airflow disturbances, oil return is prone to distribution deviation at the branching point, resulting in uneven lubricating oil return to both compressors. Over time, the compressor on the side with less oil return will gradually fall into a chronic oil shortage state, and its mechanical wear risk will quietly accumulate.

[0005] While existing technologies attempt to alleviate these problems by adding complex oil level control, frequent oil circuit switching, or forced oil equalization circulation, these often lead to a significant increase in system complexity, cost, and failure rate, and still struggle to achieve stable and adaptive balanced oil return under varying operating conditions. Therefore, developing a simple, responsive parallel compressor unit oil return pipeline system that can adapt to both single-sided and double-sided simultaneous operation, fundamentally ensuring that each compressor always receives the necessary and balanced lubrication, has become an urgent technical challenge in this field.

[0006] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0007] To address the problems in the prior art, the present invention aims to provide a parallel compressor unit that does not require solenoid valves, thereby reducing costs and simplifying control and oil return lines.

[0008] The present invention provides a parallel compressor unit, including a parallel compressor unit and an oil separator; The parallel unit includes two horizontal compressors connected in parallel; The air inlet of the oil separator is connected to the exhaust ports of the two horizontal compressors through multiple branch pipes. The oil return port of the oil separator is connected to the suction ports of the two horizontal compressors one by one through two oil return pipes. Each of the aforementioned return oil pipelines is equipped with a slope structure that causes the pipeline axis to undulate.

[0009] According to some embodiments of the present invention, the slope structure is an inverted U-shaped pipe section or a V-shaped inclined pipe section.

[0010] According to some embodiments of the present invention, the apex of the slope structure provided on the two return oil pipes is at the same height relative to the horizontal installation reference plane.

[0011] According to some embodiments of the present invention, the slope structure provided on the two return oil pipes is mirror-symmetrical with respect to a plane perpendicular to the horizontal installation reference plane.

[0012] According to some embodiments of the present invention, the height of the apex of the slope structure relative to the horizontal bottom of the return oil pipe is H, the inner diameter of the return oil pipe in the section where the slope structure is provided is D, and satisfies: H > 2D.

[0013] According to some embodiments of the present invention, taking the lowest point or starting point of the slope structure of one of the return oil pipelines as a reference point, a virtual line is formed by connecting the reference point with the highest point of the slope structure of the other return oil pipeline. The angle formed by the virtual line and the horizontal plane is Θ, and the angle Θ is greater than the maximum tilt angle allowed by the parallel compressor unit under installation and operation conditions.

[0014] According to some embodiments of the present invention, the parallel compressor unit further includes a throttling device, which is connected in series on the oil return pipe between the oil separator's oil return port and the slope structure.

[0015] According to some embodiments of the present invention, the throttling device is a capillary tube.

[0016] The parallel compressor assembly of this invention, by setting a slope structure in the oil return channel, prevents oil and condensed liquid refrigerant in the exhaust of the running compressor from flowing back into the stopped compressor due to gravity. This prevents the oil shortage problem caused by the migration of lubricating oil from the running compressor to the stopped compressor and prevents the "liquid slugging" phenomenon that may occur when the stopped compressor is restarted. At the same time, the slope structure of the oil return channel does not affect the lubricating oil balance between the two compressors in operation, avoiding the compressor from suffering from oil shortage problems. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without inventive effort. Furthermore, the drawings are merely illustrative diagrams of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0018] Figure 1 This is a schematic diagram of a parallel compressor unit according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the slope structure according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the slope structure according to another embodiment of the present invention. Detailed Implementation

[0019] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that this disclosure will be more comprehensive and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0020] In this specification, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics represented in connection with that embodiment or example, which are included in at least one embodiment or example of this specification. Furthermore, the specific features, structures, materials, or characteristics represented may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples represented in this specification, as well as the features of different embodiments or examples.

[0021] Throughout this specification, when it is said that a device is "connected" to another device, this includes not only "direct connection" but also "indirect connection" by placing other components in between. Terms indicating relative space, such as "below" and "above," are used to more easily explain the relationship of one device relative to another illustrated in the figures. These terms refer not only to their meaning in the figures but also to other meanings or operations of the device in use. For example, if the device in the figures is rotated, a device previously described as "below" another device may now be described as "above" another device. Therefore, the exemplary term "below" encompasses both above and below. The device may be rotated 90° or other angles, and the terms representing relative space are interpreted accordingly.

[0022] Although the terms first, second, etc., are used in some instances herein to refer to various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, first interface and second interface, etc., are used. Furthermore, as used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context indicates otherwise. It should be further understood that the terms “comprising,” “including,” indicate the presence of the stated feature, step, operation, element, component, item, kind, and / or group, but do not exclude the presence, occurrence, or addition of one or more other features, steps, operations, elements, components, items, kinds, and / or groups. The terms “or” and “and / or” as used herein are interpreted as inclusive, or mean any one or any combination thereof. Thus, “A, B, or C” or “A, B, and / or C” means “any one of: A; B; C; A and B; A and C; B and C; A, B, and C.” Exceptions to this definition will only occur if the combination of elements, functions, steps, or operations is inherently mutually exclusive in some way.

[0023] Although not fully defined, all terms, including technical and scientific terms used herein, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this specification pertains. Terms defined in commonly used dictionaries shall be further interpreted as having a meaning consistent with the relevant technical literature and the content of this present instruction, and shall not be over-interpreted as having an ideal or overly formulaic meaning unless otherwise defined.

[0024] The parallel compressor unit of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments are not intended to limit the scope of protection of the present invention.

[0025] The present invention provides a parallel compressor unit, which aims to optimize the oil return and operational reliability of multi-compressor systems, especially parallel units using horizontal compressors.

[0026] Figure 1 This is a schematic diagram of a parallel compressor unit according to an embodiment of the present invention. Specifically, the parallel compressor unit includes a parallel compressor unit and an oil separator 2. The parallel compressor unit includes two horizontal compressors connected in parallel, such as... Figure 1 The horizontal compressors 11 and 12 in the system have an oil separator with an inlet, an outlet B, and an oil return port. The inlet of the oil separator 2 is connected to the outlet of the horizontal compressors 11 and 12 via two branch pipes, or the outlets of the horizontal compressors 11 and 12 are connected to the inlet of the oil separator 2 via two branch pipes. After efficient separation by the oil separator 2, the refrigerant gas flows out from the outlet B and enters the system condenser, while the separated refrigeration oil is discharged from the oil return port of the oil separator 2.

[0027] The oil return port of oil separator 2 is connected to the suction ports of horizontal compressors 11 and 12 via two oil return pipes. The oil return port also has a port A for connecting to the main suction pipe. The two independent oil return pipes form the oil return paths for the two horizontal compressors (the direction of the refrigerant oil flow is as follows). Figure 1 As indicated by the arrow, this ensures that the oil separated from the exhaust of each horizontal compressor can be returned to the horizontal compressor in a targeted manner, making it possible to achieve oil balance.

[0028] Each return oil pipeline is equipped with a slope structure that causes the pipeline axis to undulate, such as... Figure 1The slope structures 31 and 32 are used in the oil return channel. The oil return channel typically uses easily bendable copper tubing. Slope structures 31 and 32 form fluid control elements on the oil return paths of the two horizontal compressors. During operation of the horizontal compressors, the flow of refrigerant gas and gravity work together to promote stable return of the refrigeration oil, overcoming resistance. When a single horizontal compressor is shut down, this structure effectively utilizes gravity to form a physical barrier, preventing oil return or liquid refrigerant from the operating side from flowing back into the shut-down compressor, thus ensuring the lubrication needs of the operating compressor and avoiding the risk of liquid slugging.

[0029] Figure 2 and Figure 3 The following are schematic diagrams of the slope structure in different embodiments. Figure 2 The slope structure (31a and 32a) of the embodiment is an inverted U-shaped pipe section, that is, a continuous curved section is set on the return oil pipe that first climbs upward and then turns downward, and its shape is similar to an inverted "U".

[0030] Figure 3 The slope structure (31b and 32b) of the embodiments is a V-shaped inclined pipe section, that is, the slope structure of the return oil pipeline is a continuous, unidirectional inclined straight line or gently folded line with a constant large slope, and its cross-sectional flow channel is shaped like one side of the "V".

[0031] Preferably, the apex of the slope structure on the two return oil pipes is at the same height relative to the horizontal installation reference plane. That is, the peak value of the maximum gravitational potential energy that the oil needs to overcome during the process of flowing from the return oil port of the oil separator 2 to the suction ports of the horizontal compressor 11 and the horizontal compressor 12 is exactly the same. The two parallel return oil paths eliminate the difference in oil flow rate caused by the different path heights.

[0032] More preferably, the slope structure provided on the two return oil pipes is relative to a plane perpendicular to the horizontal installation reference plane, see [reference]. Figure 3 The two return oil pipes, starting from the bifurcation point of the oil separator 2 and extending to the compressor suction port, include, but are not limited to, the climbing angle, bending radius, descent slope, pipe length, and even the relative positions of bends and joints being mirror-symmetrical about a plane. This structure ensures that the inertial force changes and local resistance impacts of the oil flowing towards the suction ports of horizontal compressors 11 and 12 are approximately the same. When both horizontal compressors are running on both sides, the refrigerant oil in the oil pipes enters the gas pipes, which are symmetrically arranged on both sides, and the refrigerant oil returns evenly to the compressors on both sides with the airflow.

[0033] In this embodiment, the height of the apex of the slope structure (the highest point of the pipe wall) relative to the horizontal bottom of the return oil pipe (the lowest point of the pipe wall) is H. The inner diameter of the return oil pipe in the section with the slope structure is D, and H > 2D. If the value of H is too small (e.g., close to or less than D), under certain conditions, liquid may directly cross the slope structure due to capillary action or a slight pressure difference, causing crossflow, thus preventing the slope structure from effectively isolating the compressor on the shutdown side.

[0034] Using the lowest point or starting point of the slope structure of one of the return oil pipelines as a reference point, a virtual line is formed connecting this reference point and the highest point of the slope structure of the other return oil pipeline. The angle formed by this virtual line and the horizontal plane is Θ, which is greater than the maximum allowable tilt angle of the parallel compressor unit under installation and operating conditions. Typically, the maximum allowable tilt angle of the parallel compressor unit under operating conditions is ~28°, meaning that the angle Θ can be 30° or 35°, etc. The above structural design ensures that even when the parallel compressor unit is installed or transported at an angle, the pipeline still has sufficient natural slope, allowing the oil to flow in the designated direction (usually the oil separator or the operating side) under gravity, rather than accumulating in low-lying areas.

[0035] In another embodiment, the parallel compressor unit further includes a throttling device 4, which can be a capillary tube. The throttling device 4 is connected in series on the oil return pipe between the oil separator's oil return port and the slope structure. The throttling device 4 can further control the oil return flow rate and prevent excessive oil return. The parallel compressor unit of the present invention does not require a solenoid valve, reducing costs and simplifying control and oil return piping, avoiding oil return problems caused by solenoid valve failure. Liquid refrigerant can be stored in the low-level oil return pipe after shutdown, reducing the liquid load during compressor startup, making compressor restart easier, and reducing vibration and noise during startup.

[0036] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention and should not be construed as limiting the specific implementation of the invention to these descriptions. It will be apparent to those skilled in the art that this application is not limited to the details of the above exemplary embodiments, and that the application can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be embraced within this application. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A parallel compressor unit, characterized in that, Including parallel generating units and oil separators; The parallel unit includes two horizontal compressors connected in parallel; The air inlet of the oil separator is connected to the exhaust ports of the two horizontal compressors via branch pipes. The oil return port of the oil separator is connected to the suction ports of the two horizontal compressors one by one through two oil return pipes. Each of the aforementioned return oil pipelines is equipped with a slope structure that causes the pipeline axis to undulate.

2. The parallel compressor unit according to claim 1, characterized in that, The slope structure is an inverted U-shaped pipe section or a V-shaped inclined pipe section.

3. The parallel compressor unit according to claim 1, characterized in that, The apex of the slope structure installed on the two return oil pipelines is at the same height relative to the horizontal installation reference surface.

4. The parallel compressor unit according to claim 1, characterized in that, The slope structure set on the two oil return pipes is mirror-symmetrical with respect to a plane perpendicular to the horizontal installation reference plane.

5. The parallel compressor unit according to claim 3, characterized in that, The height of the apex of the slope structure relative to the horizontal bottom of the return oil pipe is H, and the inner diameter of the return oil pipe in the section where the slope structure is provided is D, and satisfies: H > 2D.

6. The parallel compressor unit according to claim 5, characterized in that, Using the lowest point or starting point of the slope structure of one of the return oil pipelines as a reference point, a virtual line is formed by connecting the reference point with the highest point of the slope structure of the other return oil pipeline. The angle formed by the virtual line and the horizontal plane is Θ, and the angle Θ is greater than the maximum tilt angle allowed by the parallel compressor unit under installation and operation conditions.

7. The parallel compressor unit according to claim 1, characterized in that, It also includes a throttling device, which is connected in series on the return oil pipe between the oil separator's return port and the slope structure.

8. The parallel compressor unit according to claim 7, characterized in that, The throttling device is a capillary tube.

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