Shutdown device and control method for air-suspension variable-frequency centrifugal water chilling unit

Abstract

The invention provides an air-suspension variable-frequency centrifugal water chilling unit shutdown device and a control method. The shutdown device is installed on an air-suspension variable-frequency centrifugal water chilling unit system. The air-suspension variable-frequency centrifugal water chilling unit system comprises an evaporator, a compressor, a condenser, a first-stage throttling valve, an economizer, a second-stage throttling valve, a hot gas bypass valve and a shutdown valve, wherein the hot gas bypass valve is connected with the condenser and the evaporator, and the shutdown device comprises a compressor and a shutdown valve. The compressor has the beneficial effects that the pressure balance pipeline and the shutdown valve need to be arranged on the compressor, the shutdown valve is arranged at the proper position in the pressure balance pipeline, and the pressure balance pipeline is used for communicating the exhaust pipeline of the compressor with the air inlet pipeline; and high pressure in the exhaust pipeline is discharged to the low pressure side of the air inlet pipeline, so that permanent damage to a compressor bearing and a sealing system caused by back flushing of gas in the exhaust pipeline to the compressor is avoided, and the service life of the compressor is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the field of control, and in particular relates to a shutdown device and a control method for an air-suspended variable-frequency centrifugal chiller. Background Art

[0002] The air-suspended variable frequency centrifugal chiller adopts a dynamic pressure air-suspended centrifugal refrigeration compressor. The compressor adopts dynamic pressure air-floating bearing technology, which relies on the high-speed rotation of the rotor to form an air film. It does not require lubricating oil and air supply system, so that the compressor shaft is suspended in the air, reducing the efficiency loss, vibration and noise caused by mechanical friction. Therefore, the compressor bearing plays a very critical role as a key component for the stable operation of the compressor.

[0003] The compressor operation process is divided into three phases: startup, normal operation, and shutdown. During the startup phase, the compressor speed accelerates from zero to a hovering speed, and the compressor shaft enters a suspended state. During normal operation, the compressor adjusts its operating speed based on different load requirements. During operation, there is no direct physical contact between the compressor shaft and bearings. During the shutdown phase, the shaft coasts from the suspended state until it comes to a complete stop.

[0004] During the startup and shutdown process of the air-suspended variable-frequency centrifugal chiller, due to the pressure difference in the system itself, a sudden shutdown under high-pressure ratio conditions may cause the compressor to reverse, thereby causing damage to the compressor. Summary of the Invention

[0005] In view of this, the present invention aims to propose an air-suspended variable-frequency centrifugal chiller shutdown device and control method to solve the problem in the related art that during the shutdown process of the air suspension system, the gas in the exhaust pipe backflows to the compressor, causing damage to the compressor bearings and sealing system.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] In the first aspect, the present invention provides a shutdown device for an air-suspended variable frequency centrifugal chiller. The shutdown device is installed to an air-suspended variable frequency centrifugal chiller system. The air-suspended variable frequency centrifugal chiller system includes an evaporator, a compressor, a condenser, a first-level throttle valve, an economizer, a second-level throttle valve, a hot gas bypass valve and a shutdown valve connecting the condenser and the evaporator. The shutdown device includes a compressor and a shutdown valve. A shutdown valve is installed on the compressor. The two ends of the compressor are respectively connected to the evaporator and the condenser. The evaporator and the condenser are connected through a hot gas bypass valve. The evaporator is also connected to the economizer through a second-level throttle valve, and the condenser is also connected to the economizer through a first-level throttle valve.

[0008] Furthermore, the air suspension variable frequency centrifugal chiller system also includes a control panel and a frequency conversion cabinet. The frequency conversion cabinet is also installed on one side of the evaporator, and the control panel is also installed on one side of the frequency conversion cabinet.

[0009] Furthermore, the shutdown valve is a normally open solenoid valve.

[0010] In a second aspect, based on the same concept, the present invention further provides a method for controlling a shutdown device of an air-suspended variable-frequency centrifugal chiller, comprising the following steps:

[0011] When the unit receives the shutdown command of the air suspension compressor, it immediately opens the hot gas bypass valve;

[0012] Then determine the relationship between the compressor operating speed and the preset shutdown speed;

[0013] If the operating speed is less than or equal to the preset shutdown speed, the shutdown valve on the compressor will be opened and the compressor will be shut down after the preset shutdown time.

[0014] When the operating speed is greater than the preset shutdown speed, it is necessary to determine the relationship between the current compressor pressure ratio and the preset shutdown pressure ratio;

[0015] If the current pressure ratio is greater than the preset shutdown pressure ratio, the operating speed of the compressor is controlled to reduce the speed according to the preset speed. As the operating speed of the compressor decreases, the current pressure ratio of the compressor decreases accordingly;

[0016] If the current pressure ratio of the compressor is less than or equal to the preset shutdown pressure ratio or the compressor operating speed drops to the preset shutdown time speed, the shutdown valve will be opened and the compressor will be shut down for a preset time delay.

[0017] Furthermore, the current pressure ratio of the compressor is condensing pressure / evaporating pressure.

[0018] Furthermore, the preset shutdown speed is 10800 rpm.

[0019] Furthermore, the preset shutdown pressure ratio is 1.8.

[0020] Furthermore, the preset downtime value is 5s.

[0021] Compared with the prior art, the air suspension variable frequency centrifugal chiller shutdown device and control method described in the present invention have the following advantages:

[0022] The present invention describes an air-suspended variable-frequency centrifugal chiller shutdown device and control method. The present invention requires a pressure balancing pipeline and a shutdown valve to be set on the compressor. The shutdown valve is configured at a suitable position in the pressure balancing pipeline. The function of the pressure balancing pipeline is to connect the exhaust pipeline of the compressor with the intake pipeline. When shutting down, the high pressure in the exhaust pipeline is unloaded to the low-pressure side of the intake pipeline by opening the shutdown valve, thereby preventing the gas in the exhaust pipeline from backflowing to the compressor, causing permanent damage to the compressor bearings and sealing system, and ensuring the service life of the compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0024] Figure 1 This is a schematic diagram of an air suspension variable frequency centrifugal chiller system according to an embodiment of the present invention;

[0025] Figure 2 Schematic diagram of a compressor shutdown control method according to an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of a specific implementation flow of the compressor shutdown control method according to an embodiment of the present invention;

[0027] Figure 4 A side view schematic diagram of an air suspension variable frequency centrifugal chiller system according to an embodiment of the present invention;

[0028] Figure 5 This is a schematic top view of an air suspension variable frequency centrifugal chiller system according to an embodiment of the present invention;

[0029] Figure 6 This is a front view schematic diagram of an air suspension variable frequency centrifugal chiller system according to an embodiment of the present invention.

[0030] Description of reference numerals:

[0031] 1. Evaporator; 2. Compressor; 3. Condenser; 4. First-stage throttle valve; 5. Economizer; 6. Second-stage throttle valve; 7. Hot gas bypass valve; 8. Shutdown valve; 9. Control panel; 10. Frequency converter cabinet. DETAILED DESCRIPTION

[0032] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0033] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0034] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0035] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0036] like Figures 1 to 6 As shown, a shutdown device for an air-suspended variable-frequency centrifugal chiller is installed in the air-suspended variable-frequency centrifugal chiller system. The air-suspended variable-frequency centrifugal chiller system mainly consists of an evaporator 1, a compressor 2, a condenser 3, a primary throttle valve 4, an economizer 5, a secondary throttle valve 6, a hot gas bypass valve 7 connecting the condenser 3 and the evaporator 1, and a shutdown valve 8. The shutdown device mainly consists of a compressor 2, a shutdown valve 8, and matching pipelines. A shutdown valve 8 is installed on the compressor 2. The two ends of the compressor 2 are respectively connected to the evaporator 1 and the condenser 3. The evaporator 1 and the condenser 3 are connected through the hot gas bypass valve 7. The evaporator 1 is also connected to the economizer 5 through the secondary throttle valve 6, and the condenser 3 is also connected to the economizer 5 through the primary throttle valve 4. The air-suspended variable-frequency centrifugal chiller system also includes a control panel 9 and a frequency conversion cabinet 10. The frequency conversion cabinet 10 is also installed on one side of the evaporator 1, and the control panel 9 is also installed on one side of the frequency conversion cabinet 10. The shutdown valve uses a normally open solenoid valve. When there is a sudden power outage, the shutdown valve will automatically switch from a closed state to an open state to achieve a balance between the intake and exhaust pressures, avoiding damage to the compressor bearings and sealing system caused by an unexpected power outage.

[0037] A method for controlling a shutdown device of an air-suspended variable-frequency centrifugal chiller comprises the following steps:

[0038] When the unit receives the air suspension compressor shutdown command, it immediately opens the hot gas bypass valve 7 to reduce the pressure difference between the condenser 3 and the evaporator 1, and at the same time reduce the current pressure ratio (condensing pressure / evaporating pressure) of the compressor 2.

[0039] The relationship between the operating speed of compressor 2 and the preset shutdown speed is then determined. If the operating speed is less than or equal to the preset shutdown speed, the shutdown valve on the shutdown device of compressor 2 is opened, and compressor 2 is shut down for a preset shutdown time. If the operating speed is greater than the preset shutdown speed, the relationship between the current pressure ratio of the compressor and the preset shutdown pressure ratio is determined. If the current pressure ratio is greater than the preset shutdown pressure ratio, the operating speed of the air suspension compressor is controlled to decrease at a preset speed (60 rpm per second in this embodiment). As the operating speed of compressor 2 decreases, the current pressure ratio of compressor 2 decreases accordingly. If the current pressure ratio of compressor 2 is less than or equal to the preset shutdown pressure ratio or the operating speed of compressor 2 drops to the preset shutdown time speed, the shutdown valve 8 on the compressor shutdown device is opened, and compressor 2 is shut down for a preset shutdown time. By opening the shutdown valve 8, the high pressure in the compressor exhaust line is discharged to the low pressure side of the intake line, preventing gas in the exhaust line from backflowing into compressor 2 and damaging the compressor bearings and sealing system. Among them, in this embodiment, the preset shutdown speed is 10800 rpm, the preset shutdown pressure ratio is 1.8, and the preset shutdown time is 5s. These preset values are set to ensure that the wear between the compressor bearings and the foil is minimized when the compressor is shut down, meeting the requirements of smooth shutdown of the compressor.

[0040] The present invention requires a pressure balancing pipeline and a shutdown valve to be set on the compressor. The shutdown valve is configured at a suitable position in the pressure balancing pipeline. The function of the pressure balancing pipeline is to connect the exhaust pipeline of the compressor with the intake pipeline. When shutting down, the shutdown valve is opened to unload the high pressure in the exhaust pipeline to the low-pressure side of the intake pipeline, thereby preventing the gas in the exhaust pipeline from backflowing into the compressor and causing permanent damage to the compressor bearings and sealing system, thereby ensuring the service life of the compressor.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An air suspension variable frequency centrifugal chiller shutdown device, characterized by: The shutdown device is installed in an air suspension variable frequency centrifugal chiller system. The air suspension variable frequency centrifugal chiller system comprises an evaporator (1), a compressor (2), a condenser (3), a primary throttle valve (4), an economizer (5), a secondary throttle valve (6), a hot gas bypass valve (7) and a shutdown valve (8) connected to the condenser (3) and the evaporator (1). The shutdown device comprises a compressor (2) and a shutdown valve (8). The compressor (2) is provided with a shutdown valve (8). The two ends of the compressor (2) are respectively connected to the evaporator (1) and the condenser (3). The evaporator (1) and the condenser (3) are connected via the hot gas bypass valve (7). The evaporator (1) is also connected to the economizer (5) via the secondary throttle valve (6). The condenser (3) is also connected to the economizer (5) via the primary throttle valve (4).

2. The air suspension variable frequency centrifugal chiller shutdown device according to claim 1, characterized in that: The air suspension variable frequency centrifugal chiller system further comprises a control panel (9) and a frequency conversion cabinet (10). The frequency conversion cabinet (10) is further installed on one side of the evaporator (1), and the control panel (9) is further installed on one side of the frequency conversion cabinet (10).

3. The air suspension variable frequency centrifugal chiller shutdown device according to claim 1, characterized in that: The shutdown valve (8) is a normally open electromagnetic valve.

4. A method for controlling a shutdown device of an air-suspended variable-frequency centrifugal chiller, characterized in that: The following steps are involved: When the unit receives the shutdown instruction of the air suspension compressor (2), the hot gas bypass valve (7) is immediately opened; Then, determining the relationship between the operating speed of the compressor (2) and the preset shutdown speed; If the operating speed is less than or equal to the preset shutdown speed, the shutdown valve (8) on the compressor (2) is opened, and the compressor (2) is shut down after a preset shutdown time. When the operating speed is greater than the preset shutdown speed, it is necessary to determine the relationship between the current pressure ratio of the compressor (2) and the preset shutdown pressure ratio; If the current pressure ratio is greater than the preset shutdown pressure ratio, the operating speed of the compressor (2) is controlled to reduce the speed according to the preset speed, and as the operating speed of the compressor (2) decreases, the current pressure ratio of the compressor (2) decreases accordingly; If the current pressure ratio of the compressor (2) is less than or equal to the preset shutdown pressure ratio or the operating speed of the compressor (2) drops to a preset shutdown time speed, the shutdown valve (8) is opened and the compressor (2) is shut down for a preset time delay.

5. The method for controlling the shutdown device of an air-suspension variable-frequency centrifugal chiller according to claim 4, characterized in that: The current pressure ratio of the compressor (2) is condensing pressure / evaporating pressure.

6. The method for controlling a shutdown device of an air-suspension variable-frequency centrifugal chiller according to claim 4, characterized in that: The preset shutdown speed is 10800 rpm.

7. The method for controlling a shutdown device of an air-suspension variable-frequency centrifugal chiller according to claim 4, characterized in that: The preset shutdown pressure ratio is 1.

8.

8. The method for controlling a shutdown device of an air-suspension variable-frequency centrifugal chiller according to claim 4, characterized in that: The default downtime is 5s.

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