Energy and internal volume ratio adjustment methods for screw compressors

Abstract

This invention belongs to the field of compressor control technology and relates to a method for adjusting the energy and internal volume ratio of a screw compressor. The compressor is equipped with both an internal volume ratio valve and an energy valve. When operating conditions and load change, the adjustment method determines the load adjustment scheme by judging the relationship between the actual operating internal volume ratio εv and the optimal volume ratio εv_aim, and the actual load position L0 and the maximum reference load position L0_max. Load adjustment is preferentially performed through the internal volume ratio valve. When εv approaches εv_aim, adjustment is then performed through the energy valve to achieve both meeting load requirements and maintaining the optimal internal volume ratio. This method ensures the internal volume ratio valve is positioned at the optimal internal volume ratio, helping to avoid over-compression or under-compression and the resulting power consumption, thus achieving energy saving and reducing consumption. It also reduces noise and vibration caused by over-compression or under-compression.

Description

Technical Field

[0001] This invention relates to a method for adjusting the energy and internal volume ratio of a screw compressor, belonging to the field of compressor control technology. Background Technology

[0002] Screw compressors are widely used in refrigeration, air conditioning, and industrial gas compression. Their operating efficiency depends on two key adjustment capabilities: energy regulation, which adjusts the compressor's discharge volume according to changes in external load; and internal volume ratio regulation, which adjusts the matching degree between the compressor's final compression pressure and discharge pressure to avoid energy loss caused by over-compression or under-compression.

[0003] In existing technologies, the adjustment schemes for screw compressors are mainly classified into the following categories: The first type is a compressor equipped only with an energy slide valve, without an internal volume ratio adjustment mechanism. This solution cannot adjust the internal volume ratio according to changes in operating conditions, and is prone to over-compression or under-compression under varying operating conditions, resulting in increased power consumption, vibration, and noise.

[0004] The second type is compressors that are only equipped with internal volume ratio valves but lack energy valves. For example, invention patent application CN116085260A discloses a compressor internal volume ratio adjustment device and method. This solution only has internal volume ratio valves and lacks energy valves. Therefore, it is necessary to configure frequency converters and frequency conversion motors to achieve flow regulation. The use of frequency conversion start-up and flow control increases the cost.

[0005] The third category is automatic energy regulation and manual adjustment of internal volume ratio. For example, invention patent application CN108035877A discloses a screw compressor internal volume ratio adjustment mechanism. In this solution, the internal volume ratio needs to be set manually, which cannot respond to changes in operating conditions in real time, resulting in obvious adjustment lag, which also leads to increased energy consumption and vibration and noise problems.

[0006] The fourth category includes systems capable of both automatic energy regulation and automatic volume ratio regulation. For example, the invention patent with authorization announcement number CN116928916B discloses a method for automatically and steplessly adjusting the volume ratio of a screw compressor. While this solution achieves automatic regulation of both, it primarily addresses the issue of the compressor disengaging from the energy valve during volume ratio regulation, thus failing to maintain full load. It does not solve the problem of volume ratio mismatch and high energy consumption caused by load adjustment when the compressor is operating at partial load.

[0007] In all the aforementioned prior art, when the compressor needs load regulation, the internal volume ratio valve does not operate; load regulation is achieved solely through the energy valve. When the compressor operates at partial load for extended periods, this load regulation method relying solely on the energy valve can lead to severe over-compression and under-compression, thereby increasing power consumption and exacerbating compressor vibration and noise. Summary of the Invention

[0008] The purpose of this invention is to provide a new technical solution to improve or solve the technical problems existing in the prior art as described above.

[0009] The technical solution provided by this invention is as follows: A method for adjusting the energy and internal volume ratio of a screw compressor, wherein the compressor is equipped with both an internal volume ratio slide valve and an energy slide valve, comprising the following steps: S1. Calculate the optimal volume ratio εv_aim and the corresponding maximum reference load L0_max based on the compressor's operating conditions; obtain the actual operating volume ratio εv and actual load L0 of the compressor. S2. When the external load changes, compare the relationship between the deviation of the actual operating volume ratio εv and the optimal volume ratio εv_aim and the allowable deviation A, as well as the relationship between the actual load position L0 and the maximum reference load position L0_max. When the external load increases: If |εv-εv_aim|≤A and L0<L0_max, directly drive the energy slide valve to perform the load increase action; If |εv-εv_aim|>A, then first adjust the internal volume ratio slide valve to make εv approach εv_aim; when |εv-εv_aim|≤A, if the load still does not meet the demand, then drive the energy slide valve to perform the load increase action. If L0 = L0_max, then stop the loading action; When the external load remains constant: neither the internal volume ratio valve nor the energy valve operates; When the external load decreases: If |εv-εv_aim|≤A, directly drive the energy slide valve to perform a load reduction action; If |εv-εv_aim|>A, then first adjust the internal volume ratio slide valve to make εv approach εv_aim; when |εv-εv_aim|≤A, if the load still exceeds the demand, then drive the energy slide valve to perform load reduction. Where A is the allowable deviation, and its value ranges from 0.05 to 0.15.

[0010] Based on the above technical solution, the present invention can be further improved as follows.

[0011] Furthermore, the optimal volume ratio εv_aim is calculated based on the intake pressure, exhaust pressure, and characteristics of the compressible working fluid under operating conditions, using the following formula: εv_aim=(Pd / Ps)^(1 / κ); Where Pd is the exhaust pressure under operating conditions, Ps is the intake pressure under operating conditions, and κ is the isentropic exponent of the compressed working fluid.

[0012] Using the above formula, the theoretically optimal volume ratio under the current operating conditions can be calculated based on the real-time suction and discharge pressures of the compressor, combined with the thermophysical properties of the working fluid.

[0013] Furthermore, the formula for calculating the maximum reference bit L0_max is as follows: L0_max=[εv_max-εv_min-(εv_aim-εv_min)·S2 / S1] / (εv_max-εv_min); Where εv_max is the maximum adjustable value of the internal volume ratio, εv_min is the minimum adjustable value of the internal volume ratio; S1 is the maximum stroke of the energy slide valve; S2 is the maximum stroke of the internal volume ratio slide valve.

[0014] Using the above formula, the corresponding maximum reference load L0_max can be calculated based on the optimal volume ratio εv_aim under the current operating conditions and the compressor's own structural parameters (volume ratio adjustment range, maximum stroke of energy slide valve and volume ratio slide valve). This provides a dynamic upper limit reference for the load increase action of energy slide valve, which helps to meet the load demand while avoiding volume ratio mismatch caused by excessive load increase of energy slide valve, thereby reducing the risk of over-compression or under-compression.

[0015] Furthermore, the formula for calculating the actual operating volume ratio εv is as follows: εv=(εv_max-εv_min)·S / S2+εv_min; Where εv_max is the maximum adjustable content-volume ratio, and εv_min is the minimum adjustable content-volume ratio. S represents the actual stroke of the volumetric spool valve; S2 represents the maximum stroke of the volumetric spool valve.

[0016] The above formula can linearly convert the actual stroke S of the volume ratio slide valve into the current actual volume ratio εv, which allows the control system to obtain the specific value of εv in real time and compare it with the target optimal volume ratio εv_aim, providing a basis for determining whether the volume ratio needs to be adjusted and the direction of adjustment.

[0017] Furthermore, in step S2, the increase or decrease of the external load is determined by comparing the actual suction pressure of the compressor with the set suction pressure. When the actual inhalation pressure Ps is greater than the set inhalation pressure Ps 设 When this occurs, it is determined to be an increase in external load; When the actual inhalation pressure Ps is less than the set inhalation pressure Ps 设 When this occurs, it is determined that the external load has decreased; When the actual inhalation pressure Ps equals the set inhalation pressure Ps 设 When the external load remains unchanged, it is determined that the external load is constant.

[0018] By comparing the actual inspiratory pressure Ps with the set inspiratory pressure Ps 设 Determining the direction of external load changes is a direct and fast-responding load detection method. Changes in suction pressure can reflect load fluctuations relatively quickly, and using this as a trigger condition for load adjustment helps to match the compressor's discharge capacity with actual demand and reduces response delay.

[0019] Furthermore, in step S2, the increase or decrease of the external load is determined by comparing the actual evaporation temperature T with the set evaporation temperature T. 设 To determine: When the actual evaporation temperature T is greater than the set evaporation temperature T 设 When this occurs, it is determined to be an increase in external load; When the actual evaporation temperature T is less than the set evaporation temperature T 设 When this occurs, it is determined that the external load has decreased; When the actual evaporation temperature T equals the set evaporation temperature T 设 When the external load remains unchanged, it is determined that the external load is constant.

[0020] Furthermore, in step S2, the increase or decrease of the external load is determined by comparing the actual outlet water temperature Ts with the set outlet water temperature Ts. 设 To determine: When the actual outlet water temperature Ts is greater than the set outlet water temperature Ts 设 When this occurs, it is determined to be an increase in external load; When the actual outlet water temperature Ts is less than the set outlet water temperature Ts 设 When this occurs, it is determined that the external load has decreased; When the actual outlet water temperature Ts is equal to the set outlet water temperature Ts 设 When the external load remains unchanged, it is determined that the external load is constant.

[0021] Furthermore, the internal volume ratio slide valve controls the increase or decrease of the internal volume ratio through the internal volume ratio adjusting piston, and the energy slide valve controls the increase or decrease of the load through the energy adjusting piston; the energy adjusting piston and the internal volume ratio adjusting piston are respectively located in two sealed and isolated independent cavities through the partition.

[0022] The technical solution provided by this invention has the following advantages compared with the prior art: 1. When operating conditions and load change, this invention determines the load adjustment scheme by judging the relationship between the actual operating volume ratio εv and the optimal volume ratio εv_aim, and the actual load position L0 and the maximum reference load position L0_max. Load adjustment is preferentially performed through the volume ratio slide valve. When εv approaches εv_aim, adjustment is then performed through the energy slide valve to achieve both meeting load requirements and maintaining the optimal volume ratio. This method ensures the volume ratio slide valve is positioned at the optimal volume ratio, helping to avoid over-compression or under-compression and the resulting power consumption, thus achieving energy saving and consumption reduction. It also reduces noise and vibration caused by over-compression or under-compression.

[0023] 2. This invention can automatically adjust the energy output and internal volume ratio of the compressor according to operating conditions and load changes. Whether the compressor is fully loaded or partially loaded, the adjustment method of this invention can respond promptly to external changes without lag. Compared to solutions that require inverters and variable frequency motors, this invention eliminates the need for inverters and variable frequency motors, significantly improving the operating efficiency of the compressor at full and partial loads, reducing energy consumption, minimizing compressor vibration and noise, and simultaneously simplifying operation and reducing costs.

[0024] Furthermore, even when the compressor is operating at a partial load position for an extended period, the present invention can still simultaneously adjust the discharge volume and internal volume ratio, which helps maintain high operating efficiency across the entire operating range, further reducing energy consumption and vibration and noise. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the screw compressor of the present invention; Figure 2 This is a logic diagram of the present invention that determines the increase or decrease of external load and makes adjustments by comparing the actual suction pressure of the compressor with the set suction pressure. Figure 3 This is a logic diagram of the present invention that determines the increase or decrease of external load and makes adjustments by comparing the actual evaporation temperature with the set evaporation temperature. Figure 4 This is a logic diagram of the present invention, which determines the increase or decrease of external load and makes adjustments by comparing the actual outlet water temperature with the set outlet water temperature.

[0027] In the diagram, 1 is the energy regulating piston; 2 is the partition plate; 3 is the internal volume ratio regulating piston; 4 is the internal volume ratio slide valve; 5 is the energy slide valve; 6 is the first oil circuit interface; 7 is the second oil circuit interface; 8 is the third oil circuit interface; and 9 is the fourth oil circuit interface. Detailed Implementation

[0028] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the objects described and do not imply any priority in order or any specific technical meaning. Furthermore, the concepts of "connection" and "linkage" mentioned in this application, unless otherwise specified, are considered to include both direct connection (linkage) and indirect connection (linkage).

[0029] When interpreting the description of this application, it should be clarified that terms such as "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," indicating directions or positional relationships, are based on the perspective and layout shown in the accompanying drawings. They are intended to facilitate explanation and simplify the description process, and are not absolute limitations on the actual location, construction method, or operating mode of the described device or element. Therefore, these terms should not be construed as restrictive interpretations of the content of this application.

[0030] The principles and features of the present invention are described below with reference to examples. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0031] like Figure 1 As shown, a method for regulating the energy and internal volume ratio of a screw compressor is disclosed. The compressor is equipped with an internal volume ratio slide valve 4 and an energy slide valve 5. The internal volume ratio slide valve 4 is controlled by an internal volume ratio regulating piston 3 to increase or decrease the internal volume ratio, and the energy slide valve 5 is controlled by an energy regulating piston 1 to increase or decrease the load. A partition 2 separates the energy regulating piston 1 and the internal volume ratio regulating piston 3 into two independent, sealed cavities, ensuring that their actions do not interfere with each other. The internal volume ratio slide valve 4 is driven by the internal volume ratio regulating piston 3, and the energy slide valve 5 is driven by the energy regulating piston 1. When the operating conditions or load change, the pressure on both sides of the energy regulating piston 1 is adjusted through the first oil circuit interface 6 and the second oil circuit interface 7, driving the energy regulating piston 1 to move together with the energy slide valve 5 to achieve energy regulation. The pressure on both sides of the internal volume ratio regulating piston 3 is adjusted through the third oil circuit interface 8 and the fourth oil circuit interface 9, driving the internal volume ratio regulating piston 3 to move together with the internal volume ratio slide valve 4 to achieve internal volume ratio regulation. Includes the following steps: S1. Calculate the optimal volume ratio εv_aim and the corresponding maximum reference load L0_max based on the compressor's operating conditions; obtain the actual operating volume ratio εv and actual load L0 of the compressor. S2. When the external load changes, compare the relationship between the deviation of the actual operating volume ratio εv and the optimal volume ratio εv_aim and the allowable deviation A, as well as the relationship between the actual load position L0 and the maximum reference load position L0_max. When the external load increases: If |εv-εv_aim|≤A and L0<L0_max, directly drive the energy slide valve 5 to perform the load increase action; If |εv-εv_aim|>A, then first adjust the internal volume ratio slide valve 4 to make εv approach εv_aim; when |εv-εv_aim|≤A, if the load still does not meet the demand, then drive the energy slide valve 5 to perform the load increase action. If L0 = L0_max, then stop the loading action; When the external load remains constant: neither the internal volume ratio valve 4 nor the energy valve 5 operates; When the external load decreases: If |εv-εv_aim|≤A, directly drive the energy slide valve 5 to perform a load reduction action; If |εv-εv_aim|>A, then first adjust the internal volume ratio slide valve 4 to make εv approach εv_aim; when |εv-εv_aim|≤A, if the load still exceeds the demand, then drive the energy slide valve 5 to perform load reduction. The phrase "load still exceeds demand" means that, after the internal volume ratio adjustment is completed, the current exhaust volume is still greater than the actual external load demand. The phrase "load still does not meet demand" means that, after the internal volume ratio adjustment is completed, the current exhaust volume is still less than the actual external load demand.

[0032] Wherein, A is the allowable deviation, which is determined based on experience. In this embodiment, the allowable deviation A ranges from 0.05 to 0.15, preferably 0.1.

[0033] More specifically: The optimal volume ratio εv_aim is calculated based on the intake pressure, exhaust pressure, and characteristics of the compressible working fluid under operating conditions. The calculation formula is as follows: εv_aim=(Pd / Ps)^(1 / κ); Where Pd is the exhaust pressure under operating conditions, Ps is the intake pressure under operating conditions, and κ is the isentropic exponent of the compressed working fluid.

[0034] Using the above formula, the theoretically optimal volume ratio under the current operating conditions can be calculated based on the real-time suction and discharge pressures of the compressor, combined with the thermophysical properties of the working fluid.

[0035] The formula for calculating the maximum reference position L0_max is as follows: L0_max=[εv_max-εv_min-(εv_aim-εv_min)·S2 / S1] / (εv_max-εv_min); Where εv_max is the maximum adjustable value of the internal volume ratio, and εv_min is the minimum adjustable value of the internal volume ratio; S1 is the maximum stroke of energy slide valve 5; and S2 is the maximum stroke of internal volume ratio slide valve 4.

[0036] Using the above formula, the corresponding maximum reference load L0_max can be calculated based on the optimal volume ratio εv_aim under the current operating conditions and the compressor's own structural parameters (volume ratio adjustment range, maximum stroke of energy slide valve 5 and volume ratio slide valve 4). This provides a dynamic upper limit reference for the load increase action of energy slide valve 5, which helps to meet the load demand while avoiding volume ratio mismatch caused by excessive load increase of energy slide valve 5, thereby reducing the risk of over-compression or under-compression.

[0037] The current content volume ratio is the actual operating content volume ratio εv. The actual operating content volume ratio εv is obtained by calculating the position of the content volume ratio slide valve 4 after measuring its position using the content volume ratio slide valve 4 position sensor.

[0038] The formula for calculating the actual operating volume ratio εv is as follows: εv=(εv_max-εv_min)·S / S2+εv_min; Where εv_max is the maximum adjustable content-volume ratio, and εv_min is the minimum adjustable content-volume ratio. S represents the actual stroke of valve 4 with respect to its internal volume ratio; S2 represents the maximum stroke of valve 4 with respect to its internal volume ratio.

[0039] Using the above formula, the actual stroke S of the volume ratio slide valve 4 can be linearly converted into the current actual volume ratio εv, which makes it easier for the control system to obtain the specific value of εv in real time, and compare it with the target optimal volume ratio εv_aim, so as to provide a basis for judging whether the volume ratio needs to be adjusted and the direction of adjustment.

[0040] In step S2, the increase or decrease of the external load is determined by comparing the actual suction pressure of the compressor with the set suction pressure. When the actual inhalation pressure Ps is greater than the set inhalation pressure Ps 设 When this occurs, it is determined to be an increase in external load; When the actual inhalation pressure Ps is less than the set inhalation pressure Ps 设 When this occurs, it is determined that the external load has decreased; When the actual inhalation pressure Ps equals the set inhalation pressure Ps 设 When the external load remains unchanged, it is determined that the external load is constant.

[0041] Determining the direction of external load changes by comparing the actual suction pressure with the set suction pressure is a direct and fast-responding load detection method. Changes in suction pressure can reflect load fluctuations relatively quickly, and using this as a trigger condition for load adjustment helps to match the compressor's discharge capacity with actual demand and reduces response delay.

[0042] It should be noted that in actual use, the direction of change in external load can also be determined by relevant parameters such as evaporation temperature or outlet water temperature. Evaporation temperature refers to the saturation temperature of the refrigerant when it boils and vaporizes in the evaporator; it corresponds one-to-one with the suction pressure and is an important parameter reflecting changes in the evaporator-side load. Outlet water temperature refers to the actual temperature of the refrigerant when it leaves the evaporator (cooling mode) or condenser (heating mode); it directly reflects changes in the user's demand for cooling or heating.

[0043] For example, in another embodiment, the evaporation temperature is used as the criterion. In step S2, the increase or decrease of the external load is determined by comparing the actual evaporation temperature T with the set evaporation temperature T. 设 To judge, such as Figure 3 As shown: When the actual evaporation temperature T is greater than the set evaporation temperature T 设 When this occurs, it is determined to be an increase in external load; When the actual evaporation temperature T is less than the set evaporation temperature T 设 When this occurs, it is determined that the external load has decreased; When the actual evaporation temperature T equals the set evaporation temperature T 设 When the external load remains unchanged, it is determined that the external load is constant.

[0044] like Figure 4 As shown, in another embodiment, the outlet water temperature is used as the criterion. In step S2, the increase or decrease of the external load is determined by comparing the actual outlet water temperature Ts with the set outlet water temperature Ts. 设 To determine: When the actual outlet water temperature Ts is greater than the set outlet water temperature Ts 设 When this occurs, it is determined to be an increase in external load; When the actual outlet water temperature Ts is less than the set outlet water temperature Ts 设 When this occurs, it is determined that the external load has decreased; When the actual outlet water temperature Ts is equal to the set outlet water temperature Ts 设 When the external load remains unchanged, it is determined that the external load is constant.

[0045] like Figure 2 As shown, by comparing the actual suction pressure Ps of the compressor with the set suction pressure Ps 设The method for determining the increase or decrease of the external load and making adjustments is as follows: Periodically check the actual suction pressure Ps of the compressor and compare it with the preset suction pressure Ps: If Ps > Ps 设 It was determined that an additional load was needed; If Ps = Ps 设 The load is determined to be matched, and no adjustment is made. If Ps < Ps 设 It was determined that the load needed to be reduced.

[0046] When Ps > Ps is detected 设 When this occurs, the system issues an overload command and performs the following judgment and adjustment steps: If |εv-εv_aim|≤A, it indicates that the current content product ratio is already in a matching state, and the energy slide valve 5 is directly driven to perform the load increase action; If |εv-εv_aim|>A, it indicates that the current volume ratio deviates significantly from the target value. Therefore, the volume ratio valve 4 is first adjusted to make εv approach εv_aim. If the load still does not meet the demand after |εv-εv_aim|≤A, the energy valve 5 is then driven to perform an additional load operation. After the load operation is complete, return and re-check Ps and Ps. 设 Repeat the above process until Ps = Ps 设 .

[0047] When Ps < Ps is detected 设 When this occurs, the system issues a load reduction command and performs the following judgment and adjustment steps: If |εv-εv_aim|≤A, it indicates that the current content product ratio is already in a matched state, and the energy slide valve 5 is directly driven to unload. If |εv-εv_aim|>A, it indicates that the current content volume ratio deviates significantly from the target value. Therefore, the content volume ratio valve 4 is first driven to adjust εv towards εv_aim until |εv-εv_aim|≤A. Then, the energy valve 5 is driven to reduce the load. After the load reduction action is completed, return and re-check the relationship between Ps and Ps set, repeat the above process until Ps = Ps 设 .

[0048] When Ps = Ps is detected 设 When the current actual suction pressure matches the set value, the compressor discharge volume matches the external load. At this time, neither the internal volume ratio valve 4 nor the energy valve 5 operates, and the system maintains its current operating state.

[0049] It should be noted that in this invention, "load increase" refers to increasing the compressor's discharge volume, that is, the energy slide valve 5 moves in the direction of increasing discharge volume, thereby increasing the compressor's cooling or heating capacity; "load decrease" refers to reducing the compressor's discharge volume, that is, the energy slide valve 5 moves in the direction of decreasing discharge volume, thereby reducing the compressor's cooling or heating capacity.

[0050] The "internal volume ratio adjustment" refers to changing the ratio of the compressor's internal compression final pressure to the suction pressure by moving the internal volume ratio slide valve 4 according to changes in operating conditions, so as to match the compressor's internal pressure with the discharge pipe pressure and avoid over-compression or under-compression; the "energy adjustment" refers to changing the compressor's discharge volume by moving the energy slide valve 5 according to changes in external load, so as to meet load requirements.

[0051] When operating conditions and loads change, this invention determines a load adjustment scheme by judging the relationship between the actual operating volume ratio εv and the optimal volume ratio εv_aim, and the actual load position L0 and the maximum reference load position L0_max. Load adjustment is preferentially performed through the volume ratio slide valve 4. When εv approaches εv_aim, adjustment is then performed through the energy slide valve 5 to achieve both meeting load requirements and maintaining the optimal volume ratio. This method ensures that the volume ratio slide valve 4 is positioned at the optimal volume ratio, helping to avoid over-compression or under-compression and the resulting power consumption, thus achieving energy saving and reducing consumption. It also reduces noise and vibration caused by over-compression or under-compression.

[0052] Taking 80% load as an example, according to theoretical calculations, after adopting the adjustment method of this invention, compared with the scheme without volume ratio adjustment, the coefficient of performance (COP) is expected to increase by about 12% to 35%, vibration can be reduced by about 3%, and noise can be reduced by about 3 to 5 dBA. It should be noted that the energy-saving effect varies under different operating conditions. The above data are the expected range under typical operating conditions, and the actual effect may vary depending on the specific operating conditions and compressor model.

[0053] This invention can automatically adjust the energy output and internal volume ratio of the compressor according to operating conditions and load changes. Whether the compressor is fully loaded or partially loaded, the adjustment method of this invention can respond promptly to external changes without lag. Compared to solutions that require inverters and variable frequency motors, this invention eliminates the need for inverters and variable frequency motors, significantly improving the operating efficiency of the compressor at both full and partial loads, reducing energy consumption, minimizing compressor vibration and noise, and simultaneously simplifying operation and reducing costs.

[0054] Furthermore, even when the compressor is operating at a partial load position for an extended period, the present invention can still simultaneously adjust the discharge volume and internal volume ratio, which helps maintain high operating efficiency across the entire operating range, further reducing energy consumption and vibration and noise.

[0055] 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 within the protection scope of the present invention.

Claims

1. A method for adjusting the energy and internal volume ratio of a screw compressor, wherein the compressor is equipped with both an internal volume ratio slide valve and an energy slide valve, characterized in that, Includes the following steps: S1. Calculate the optimal volume ratio εv_aim and the corresponding maximum reference load L0_max based on the compressor's operating conditions; obtain the actual operating volume ratio εv and actual load L0 of the compressor. S2. When the external load changes, compare the relationship between the deviation of the actual operating volume ratio εv and the optimal volume ratio εv_aim and the allowable deviation A, as well as the relationship between the actual load position L0 and the maximum reference load position L0_max. When the external load increases: If |εv-εv_aim|≤A and L0<L0_max, directly drive the energy slide valve to perform the load increase action; If |εv-εv_aim|>A, then first adjust the internal volume ratio slide valve to make εv approach εv_aim; when |εv-εv_aim|≤A, if the load still does not meet the demand, then drive the energy slide valve to perform the load increase action. If L0 = L0_max, then stop the loading action; When the external load remains constant: neither the internal volume ratio valve nor the energy valve operates; When the external load decreases: If |εv-εv_aim|≤A, directly drive the energy slide valve to perform a load reduction action; If |εv-εv_aim|>A, then first adjust the internal volume ratio slide valve to make εv approach εv_aim; when |εv-εv_aim|≤A, if the load still exceeds the demand, then drive the energy slide valve to perform load reduction. Where A is the allowable deviation, and its value ranges from 0.05 to 0.

15.

2. The method for adjusting the energy and internal volume ratio of a screw compressor according to claim 1, characterized in that, The optimal volume ratio εv_aim is calculated based on the intake pressure, exhaust pressure, and characteristics of the compressed working fluid under operating conditions. The calculation formula is as follows: εv_aim=(Pd / Ps)^(1 / κ); Where Pd is the exhaust pressure under operating conditions, Ps is the intake pressure under operating conditions, and κ is the isentropic exponent of the compressed working fluid.

3. The method for adjusting the energy and internal volume ratio of a screw compressor according to claim 1, characterized in that, The formula for calculating the maximum reference position L0_max is as follows: L0_max=[εv_max-εv_min-(εv_aim-εv_min)·S2 / S1] / (εv_max-εv_min); Where εv_max is the maximum adjustable value of the internal volume ratio, and εv_min is the minimum adjustable value of the internal volume ratio; S1 is the maximum stroke of the energy slide valve; and S2 is the maximum stroke of the internal volume ratio slide valve.

4. The method for adjusting the energy and internal volume ratio of a screw compressor according to claim 1, characterized in that, The formula for calculating the actual operating volume ratio εv is as follows: εv=(εv_max-εv_min)·S / S2+εv_min; Where εv_max is the maximum adjustable content-volume ratio, and εv_min is the minimum adjustable content-volume ratio. S represents the actual stroke of the volumetric spool valve; S2 represents the maximum stroke of the volumetric spool valve.

5. The method for adjusting the energy and internal volume ratio of a screw compressor according to any one of claims 1-4, characterized in that, In step S2, the increase or decrease of the external load is determined by comparing the actual suction pressure Ps of the compressor with the set suction pressure Ps 设 : When the actual intake pressure Ps is greater than the set intake pressure Ps 设 an increase in external load is determined. When the actual intake pressure Ps is smaller than the set intake pressure Ps 设 , it is determined that the external load is reduced. When the actual intake pressure Ps is equal to the set intake pressure Ps 设 the external load is determined to be constant.

6. The method for adjusting the energy and internal volume ratio of a screw compressor according to any one of claims 1-4, characterized in that, In step S2, the increase or decrease of the external load is determined by comparing the actual evaporation temperature T with the set evaporation temperature T. 设 To determine: When the actual evaporation temperature T is greater than the set evaporation temperature T 设 When this occurs, it is determined to be an increase in external load; When the actual evaporation temperature T is less than the set evaporation temperature T 设 When this occurs, it is determined that the external load has decreased; When the actual evaporation temperature T equals the set evaporation temperature T 设 When the external load remains unchanged, it is determined that the external load is constant.

7. The method for adjusting the energy and internal volume ratio of a screw compressor according to any one of claims 1-4, characterized in that, In step S2, the increase or decrease of the external load is determined by comparing the actual outlet water temperature Ts with the set outlet water temperature Ts. 设 To determine: When the actual outlet water temperature Ts is greater than the set outlet water temperature Ts 设 When this occurs, it is determined to be an increase in external load; When the actual outlet water temperature Ts is less than the set outlet water temperature Ts 设 When this occurs, it is determined that the external load has decreased; When the actual outlet water temperature Ts is equal to the set outlet water temperature Ts 设 When the external load remains unchanged, it is determined that the external load is constant.

8. The method for adjusting the energy and internal volume ratio of a screw compressor according to claim 1, characterized in that, The internal volume ratio slide valve controls the increase or decrease of the internal volume ratio through the internal volume ratio adjusting piston, and the energy slide valve controls the increase or decrease of the load through the energy adjusting piston; the energy adjusting piston and the internal volume ratio adjusting piston are respectively located in two sealed and isolated independent cavities through the partition.

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