A control method for regulating optimal supplementary gas intermediate pressure of a two-stage compression screw machine set

Abstract

The present application relates to the technical field of compressor, especially to a control method for adjusting optimal intermediate pressure of supplementary air of two-stage compression screw unit. The intermediate pressure is generated in the supplementary air inlet of the compressor unit, and the compressor is controlled to make the intermediate pressure reach the optimal value. However, the method needs to obtain different optimal numerical parameters according to different real conditions of the compressor, and obtain the optimal correction coefficient "d" according to the intermediate pressure calculation formula P=SQRT(a*b)*d. Then, the intermediate pressure deviation between the intermediate pressure calculation value and the intermediate pressure measured value is determined according to the numerical value of "d". Finally, the high and low pressure rotating speed of the compressor is accurately controlled according to the deviation value, so that the intermediate pressure is in the optimal state. Through the method, the energy efficiency of the unit in the whole operating range can be guaranteed to reach the optimum, and the overall energy efficiency is improved by about 2%-3%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of compressor, in particular to a control method for adjusting optimal intermediate pressure of supplementary air of a two-stage compression screw compressor unit. BACKGROUND

[0002] The two-stage screw compressor unit mainly consists of a low-pressure stage screw compressor, a high-pressure stage screw compressor, an oil separator, an oil cooler and an economizer, etc. The components are connected through corresponding pipelines, valves, delivery pumps and control elements, and together with a condenser and an evaporator, they form a complete refrigeration compression system.

[0003] The main path of the refrigeration cycle is as follows: the low-pressure stage screw refrigeration compressor sucks in low-pressure refrigerant vapor from the evaporator, and discharges the compressed refrigerant vapor to the high-pressure stage screw refrigeration compressor. The oil-gas mixture enters the oil separator after being compressed twice. The refrigerant vapor separated from the oil separator flows to the condenser, and is condensed into refrigerant liquid, which then flows to the economizer to be supercooled. The supercooled high-pressure refrigerant liquid passes through a throttling valve, and then enters the evaporator to absorb the heat of the coolant liquid to boil and evaporate. The obtained refrigerant vapor is sucked into the low-pressure stage screw refrigeration compressor, completing the refrigeration cycle. The lubricating oil separated from the oil separator enters the oil cooler, and is cooled and filtered before being delivered to the low-pressure stage screw refrigeration compressor and the high-pressure stage screw refrigeration compressor for recycling.

[0004] The two-stage screw compressors on the market are all provided with a supplementary air inlet. The unit determines whether to supplement air to the unit according to the actual use condition, so as to realize high energy efficiency operation under harsh conditions.

[0005] The supplementary air amount of the existing two-stage screw compressor unit is controlled according to the superheat degree of the air sucked by the supplementary air inlet, and the intermediate pressure is not controlled. Therefore, it is necessary to design a control method for controlling the intermediate supplementary air pressure at the optimal point of the unit energy efficiency. SUMMARY

[0006] In order to solve the above technical problems, the purpose of the present application is to provide a control method for adjusting optimal supplementary air intermediate pressure of a two-stage compression screw compressor unit. Through this control method, the energy efficiency of the unit in the entire operating range can be guaranteed to reach the best, and the overall energy efficiency can be improved by about 2%-3%.

[0007] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0008] A control method for adjusting optimal supplementary air intermediate pressure of a two-stage compression screw compressor unit, the control method comprising the following steps:

[0009] S1, first according to the different real-time of compressor, the current compressor internal each numerical parameter is obtained, and the best intermediate pressure correction coefficient is obtained according to intermediate pressure calculation value formula;

[0010] Intermediate pressure calculation value formula: P=SQRT (a*b) *d, wherein: "a" is the low pressure of compressor, "b" is the high pressure of compressor, "d" is the intermediate pressure correction coefficient;

[0011] S2, according to the best intermediate pressure correction coefficient "d" calculated, and according to the numerical value of "d", the intermediate pressure deviation of intermediate pressure calculation value and intermediate pressure measured value is determined;

[0012] Intermediate pressure deviation formula: Δp=P4-P3=SQRT (a*b) *d-c;Wherein: "P4" is the intermediate pressure calculation value, "P3" is the intermediate pressure measured value;

[0013] S3, according to Δp to control the high and low pressure rotating speed of compressor:

[0014] 1) when Δp>m kpa: the measured intermediate pressure is less than the theoretical best intermediate pressure value, the high pressure rotating speed is loaded through the judgment period, and immediately loaded e turns, waits t seconds for the judgment period, and judges whether Δp is greater than m Kpa again;If still greater than m Kpa, the high pressure rotating speed continues to load e turns, and the cycle is repeated until Δp is no longer greater than m Kpa;Execute other logic;Wherein, "e" is the loading deviation;

[0015] 2) when Δp<-m kpa: the measured intermediate pressure is greater than the theoretical best intermediate pressure value, the high pressure rotating speed is unloaded through the judgment period, and immediately unloaded f turns, waits t seconds for the judgment period, and judges whether Δp is less than-m Kpa again;If still less than-m Kpa, the high pressure rotating speed continues to unload f turns, and the cycle is repeated until Δp is no longer less than-m Kpa;Execute other logic;Wherein, "f" is the unloading deviation;

[0016] 3) when-m Kpa≥Δp≥m Kpa, the high / low pressure rotating speed remains unchanged, and the high pressure rotating speed deviation remains unchanged;Until Δp>m kpa or Δp<-m kpa, execute 1) or 2) control logic.

[0017] Further, the application also discloses that the unit comprises a compressor, a lubricating oil separator, a condenser, an economizer plate exchanger and an evaporator which are sequentially communicated with the exhaust port of the compressor to form a main loop, and the main loop is finally communicated to the suction port of the compressor; wherein, the main loop is externally connected with a secondary loop, the secondary loop is communicated from the condenser to the economizer plate exchanger and finally communicated to the air supplement port of the compressor;The screw unit adopts the method to adjust the best air supplement intermediate pressure.

[0018] Preferably, a throttling component is arranged on the main circuit, and the throttling component is arranged between the economizer heat exchanger and the evaporator.

[0019] Further, the application also discloses a computer device, a memory, a processor and a computer program stored in the memory, the processor executes the computer program to realize the method.

[0020] Further, the application also discloses a computer readable storage medium, and the computer readable storage medium stores a computer program or instructions, and the computer program or instructions are executed by a processor to realize the method.

[0021] Further, the application also discloses a computer program product, and the computer program product comprises a computer program or instructions, and the computer program or instructions are executed by a processor to realize the method.

[0022] In conclusion, the application has the following advantages:

[0023] The control method needs to acquire various information values of the compressor of the unit, so that the optimal intermediate pressure correction coefficient is derived, the intermediate pressure deviation is confirmed according to the coefficient, and the high and low pressure rotating speeds of the compressor are specifically adjusted according to the size of the deviation. The logic of the control method can guarantee that the energy efficiency of the unit can reach the best in the whole operating range, and the energy efficiency of the whole machine is improved by about 2%-3%. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Fig. 1 is a structural schematic diagram of the unit of the application;

[0025] Figure 2 Fig. 2 is a secondary compression refrigeration cycle diagram;

[0026] Fig. 1 is a structural schematic diagram of the unit of the application; DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0028] In the description of this application, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0029] It should also be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0030] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0031] like Figures 1-2 As shown, the present invention is a control method for adjusting the optimal intermediate pressure of the gas injection. The method performs intermediate pressure control and adjustment on the compressor 1 of a two-stage compression screw compressor unit. The unit includes a compressor 1 and a lubricating oil separator 2, a condenser 3, an economizer plate heat exchanger 4 and an evaporator 5 connected in sequence to the exhaust port of the compressor 1, and finally connected to the intake port of the compressor 1 to form a main circuit 6. A throttling component 8 is provided on the main circuit 6, which is located between the economizer and the evaporator 5.

[0032] Among them, a secondary circuit 7 is also connected to the main circuit 6. The secondary circuit 7 is connected from the condenser 3 to the economizer plate heat exchanger 4 and finally to the air supply port of the compressor 1.

[0033] Since the structure and circuit distribution of the above-mentioned units are all existing technologies, their structure will not be described in detail.

[0034] Because intermediate pressure is generated in the air inlet of compressor 1, compressor 1 needs to be controlled and adjusted to achieve the optimal value of intermediate pressure. The magnitude of intermediate pressure is related to the speed of the low / high pressure stage. According to the design of our compressor 1, the current fixed low / high speed ratio is 1.2. At this speed ratio, it is suitable for design differential pressure conditions. However, when operating under other non-standard conditions, the intermediate air inlet pressure at this speed ratio will change, and its actual value will deviate from the optimal intermediate air inlet pressure value, resulting in an intermediate pressure deviation. However, since the low / high pressure speed ratio g is already fixed, the optimal intermediate pressure value under the current operating conditions can only be adjusted by adjusting the high pressure stage speed deviation.

[0035] The specific steps for controlling the optimal intermediate pressure value include:

[0036] S1, first according to the different real-time of compressor 1, the current compressor 1 inside each numerical parameter is obtained, and the best intermediate pressure correction coefficient is obtained according to the intermediate pressure calculation value formula;

[0037] The intermediate pressure calculation value formula is P=SQRT(a*b)*d, wherein "a" is the low pressure of compressor 1, "b" is the high pressure of compressor 1, and "d" is the intermediate pressure correction coefficient;

[0038] S2, according to the best intermediate pressure correction coefficient "d" obtained by calculation, and according to the numerical value of "d", the intermediate pressure deviation of the intermediate pressure calculation value and the intermediate pressure measured value is determined;

[0039] The intermediate pressure deviation formula is Δp=P4-P3=SQRT(a*b)*d-c, wherein "P4" is the intermediate pressure calculation value, and "P3" is the intermediate pressure measured value;

[0040] S3, according to Δp, the high and low pressure rotating speed of compressor 1 is controlled:

[0041] a) when Δp>m kpa: the measured intermediate pressure is less than the theoretical best intermediate pressure value, the high pressure rotating speed is loaded through the judgment period, and immediately loaded e turns (can be set), waits t seconds for the judgment period, and judges whether Δp is greater than m kpa again; if it is still greater than m kpa, the high pressure rotating speed continues to load e turns (can be set), and the cycle is repeated until Δp is no longer greater than m kpa; other logic is executed; wherein "e" is the loading deviation;

[0042] b) when Δp<-m kpa: the measured intermediate pressure is greater than the theoretical best intermediate pressure value, the high pressure rotating speed is unloaded through the judgment period, and immediately unloaded f turns (can be set), waits t seconds for the judgment period, and judges whether Δp is less than-m kpa again; if it is still less than-m kpa, the high pressure rotating speed continues to unload f turns (can be set), and the cycle is repeated until Δp is no longer less than-m kpa; other logic is executed; wherein "f" is the unloading deviation;

[0043] c) when-m kpa≥Δp≥m kpa, the high / low pressure rotating speed remains unchanged, and the high pressure rotating speed deviation remains the current value; until Δp>m kpa or Δp<-m kpa, 1 or 2 control logic is executed.

[0044] This control method needs to obtain the information values of the compressor of the unit first, so that the best intermediate pressure correction coefficient is obtained, the intermediate pressure deviation is confirmed according to the coefficient, and the high and low pressure rotating speed of the compressor is adjusted according to the size of the deviation. Figure TwoThe obtained data can show that the logic of the control method can ensure that the energy efficiency of the unit in the whole operating range can reach the best, and the whole machine energy efficiency is improved by about 2%-3%.

[0045] Table 1 is the definition of each control point of the compressor

[0046]

[0047] As shown in the following table, “2.50” refers to the built-in volume ratio of the compressor 1 of the applicant, “Q” is the heating capacity, “P” is the input power, “cop” refers to the energy efficiency, and “0 / 70” refers to the evaporation temperature / condensation temperature.

[0048] Table 2 is a description diagram of each real-time parameter of the compressor of the unit of the application

[0049]

[0050] The above is the description of the embodiments of the application, through the above description of the disclosed embodiments, the person skilled in the art can realize or use the application. Various modifications of these embodiments will be apparent to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method for adjusting the optimal intermediate pressure of the injection gas in a two-stage screw compressor unit, characterized in that, The control method includes the following steps: S1. First, based on the different actual conditions of the compressor, obtain the various numerical parameters inside the compressor, and then obtain the optimal intermediate pressure correction coefficient according to the intermediate pressure calculation formula. The formula for calculating intermediate pressure is: P=SQRT(a*b)*d, where: "a" is the low pressure of the compressor, "b" is the high pressure of the compressor (1), and "d" is the intermediate pressure correction coefficient; S2. Based on the calculated optimal intermediate pressure correction coefficient "d", and based on the value of "d", determine the intermediate pressure deviation between the calculated intermediate pressure value and the measured intermediate pressure value; The formula for intermediate pressure deviation is: Δp = P4 - P3 = SQRT(a*b) * dc; where "P4" is the calculated value of intermediate pressure and "P3" is the measured value of intermediate pressure. S3. Control the high and low pressure speeds of the compressor based on Δp: 1) When Δp > m kPa: This means that the measured intermediate pressure is less than the theoretical optimal intermediate pressure value. The high-pressure stage speed is loaded through the judgment cycle, that is, it is immediately loaded with e revolutions, waits for t seconds of judgment cycle, and then judges again whether Δp is greater than m kPa. If it is still greater than m kPa, the high-pressure stage speed continues to be loaded with e revolutions, and this cycle continues until Δp is no longer greater than m kPa; then other logic is executed; where "e" is the loading deviation. 2) When Δp < -m kPa: This means that the measured intermediate pressure is greater than the theoretical optimal intermediate pressure value. The high-pressure stage speed is unloaded through the judgment cycle, that is, it is immediately unloaded by f revolutions, waits for t seconds of judgment cycle, and then judges again whether Δp is less than -m kPa. If it is still less than -m kPa, the high-pressure stage speed continues to unload by f revolutions, and this cycle continues until Δp is no longer less than -m kPa; then other logic is executed; where "f" is the unloading deviation. 3) When -m Kpa≥Δp≥m Kpa, the speed of the high / low pressure stage remains unchanged, and the speed deviation of the high pressure stage remains unchanged at the current value; until Δp>m kpa or Δp<-m kpa, execute control logic 1) or 2).

2. A two-stage compression screw compressor unit, the unit comprising a compressor (1) and a lubricating oil separator (2), a condenser (3), an economizer plate heat exchanger (4), and an evaporator (5) sequentially connected to the exhaust port of the compressor (1), and ultimately connected to the intake port of the compressor (1) to form a main circuit (6); wherein, A secondary circuit (7) is also connected to the main circuit (6), the secondary circuit (7) is connected from the condenser (3) to the economizer plate heat exchanger (4) and finally to the air supply port of the compressor (1); the screw compressor unit is characterized in that the optimal air supply intermediate pressure is adjusted by the method described in claim 1.

3. A two-stage compression screw compressor unit according to claim 2, characterized in that, The main circuit is provided with a throttling component (8), which is located between the economizer plate heat exchanger (4) and the evaporator (5).

4. A computer device, comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the method of claim 1.

5. A computer-readable storage medium having a computer program or instructions stored thereon, characterized in that, When the computer program or instructions are executed by a processor, they implement the method of claim 1.

6. A computer program product, comprising a computer program or instructions, characterized in that, When the computer program or instructions are executed by a processor, they implement the method of claim 1.

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