A gas volume composite regulation method based on a reciprocating piston air compressor

Abstract

The application provides a gas volume composite regulation method based on a reciprocating piston air compressor, which comprises the following steps: the air compressor is regulated to preferentially use frequency conversion regulation, when the running frequency of the air compressor is reduced to a lower limit and the gas volume still cannot match the gas consumption, the air compressor is switched to half-load operation, that is, half of the air inlet valves are closed to reduce the gas volume and match smaller gas consumption. The gas volume composite regulation mode of the air compressor can maximize the gas volume regulation range, can make the gas volume of the air compressor better match the gas consumption of the bottle blowing line, can improve the loading rate of the air compressor, can directly reduce the waste of energy caused by unloading and idling, and can further ensure the gas production efficiency of the equipment and reduce the average running power due to the avoidance of frequent switching between loading and unloading.

Description

Technical Field

[0001] This invention relates to the field of PET (Polyethylene Terephthalate) blow molding, and more particularly to a method for combined air volume regulation based on a reciprocating piston air compressor. Background Technology

[0002] During bottle blowing production, the demand for compressed air fluctuates frequently and significantly. Therefore, air compressors need to constantly adjust their output to match this fluctuation and ensure stable operating pressure. Fixed-frequency air compressors regulate flow by opening and closing the inlet valve, but this method is inefficient, and repeated unloading / loading wastes a significant amount of energy. Variable-frequency drive (VFD) air compressors adjust the motor speed via a frequency converter to regulate output, ensuring that output matches demand. Theoretically, they can achieve 100% load under continuous air demand. However, in practice, due to the lower limit of the compressor's operating frequency and the fact that air demand sometimes falls below the minimum output adjustable by the VFD, and because there are limitations on the frequency adjustment speed to ensure stable operation, the air compressor still frequently loads / unloads when air demand fluctuates significantly, wasting energy.

[0003] When using frequency converters for reciprocating piston air compressors in bottle blowing, cost considerations generally prevent the direct use of variable frequency motors. Instead, a common motor with a forced cooling fan is typically used. To ensure normal motor operation, the lower frequency limit is at most 25Hz, while selecting a fully variable frequency motor is extremely expensive. Angle-type piston air compressors, such as V-type, W-type, and L-type compressors, cannot achieve inertial force balance, resulting in significant vibration during operation. This vibration intensifies at low frequencies, limiting the lower frequency limit to as low as 37Hz. The smaller the frequency conversion range of the air compressor, i.e., the smaller the range of air output adjustment, the more difficult it is to match fluctuations in air consumption, and the more prone it is to unloading. Due to the high cost of variable frequency motors and the structural limitations of the air compressor itself, further lowering the lower frequency limit to increase the air output adjustment range is currently not feasible. Summary of the Invention

[0004] Purpose of the invention: In order to solve the technical problem of insufficient air volume adjustment range of reciprocating piston air compressors in the prior art, an air volume composite adjustment method based on reciprocating piston air compressors is invented. That is, based on frequency conversion regulation, when the air compressor operating frequency is reduced to the lower limit and the air production still cannot match the air consumption, the air compressor is switched to half-load operation, that is, half of the intake valve is closed to reduce the air production and match the smaller air consumption.

[0005] This invention includes the following steps:

[0006] Step S101: Uninstall startup, increase running frequency to the lower limit;

[0007] Step S102: Run at full load and full speed;

[0008] Step S103, full load stage, variable frequency speed control operation;

[0009] Step S104, speed-limited operation;

[0010] Step S105: Switch to half-load operation;

[0011] Step S106, half-load stage, variable frequency speed control operation;

[0012] Step S107, half-load stage, speed-limited operation;

[0013] Step S108: Switch to uninstallation and run;

[0014] Step S109: When running at half load and high speed, switch back to full load.

[0015] Step S101 includes: during startup, the air compressor is in an unloaded state, that is, both sets of intake valves are closed; during startup, the frequency rises from 0 Hz to the allowable lower limit frequency, and the startup process lasts for Y seconds.

[0016] Step S102 includes: After the air compressor starts, a test is performed. If P1 < P2 - P3 is satisfied, the system switches to full-load operation and the operating frequency is quickly adjusted to the upper limit to maintain full-speed operation, ensuring that the exhaust pressure approaches the target pressure as soon as possible; where P1 represents the exhaust pressure of the air compressor, P2 represents the target pressure used, and P3 represents the allowable deviation range of the target pressure.

[0017] Step S103 includes: performing a detection; if |P2-P1|≤P3 is satisfied, the air compressor enters the flow control frequency conversion mode, with Q1 as the set value of the frequency converter and Q2 as the feedback value of the frequency converter. When the air consumption is greater than the air production, the system reduces the operating frequency, thereby reducing the air compressor speed to reduce the air production, thus lowering the exhaust pressure and moving closer to the target pressure; when the air consumption is less than the air production, the system increases the operating frequency, thereby increasing the air compressor speed to increase the air production, thus raising the exhaust pressure and moving closer to the target pressure.

[0018] Step S103 includes: performing a detection; if |P2-P1|≤P3 is satisfied, the air compressor enters the pressure control frequency conversion mode, with P2 as the set value of the frequency converter and P1 as the feedback value of the frequency converter. The frequency converter adjusts the operating frequency of the air compressor through PID mode according to the changes in the set value and the feedback value to ensure constant pressure operation of the air compressor.

[0019] In step S103, the PID mode includes a proportional unit P, an integral unit I, and a derivative unit D. The relationship between the input e(t) and the output u(t) is as follows:

[0020] u(t)=kp[(e(t)+1 / TI∫e(t)dt+TD*de(t) / dt]

[0021] Where kp is the proportional coefficient, TI is the integral time constant, TD is the derivative time constant, d is the derivative sign, input e(t) represents the calculated deviation between the inverter feedback value and the set value, and u(t) represents the operating frequency;

[0022] When the theoretical calculation result of the air compressor output Q2 deviates from the actual result, the calculation result of Q2 is corrected: when Q1 > Q2, theoretically P1 should decrease; if P1 increases, it means that the calculated value of Q2 is greater than the actual value, then Q is corrected once. 2＝ Q2 + △Q; When Q1 < Q2, theoretically P1 should increase. If P1 decreases, it means that the calculated value of Q2 is less than the actual value, so execute Q2 = Q2 - △Q once.

[0023] The calculation method for the deviation △Q between the theoretical and actual air output Q2 of the air compressor: Within the cycle time T, calculate the pressure difference △P. Based on the air tank volume V, the deviation air output △Q = △P * V (60 / T). If the flow meter fails, the pressure control frequency conversion mode is adopted, with P2 as the set value of the frequency converter and P1 as the feedback value of the frequency converter.

[0024] Step S104 includes: performing a detection; if P1 > P2 + P3, the air compressor quickly adjusts its operating frequency to the lower limit, maintains low-speed operation, and reduces the amount of air produced.

[0025] Step S105 includes: when the operating frequency has been adjusted to the lower limit, the air consumption is still less than the air output of the air compressor, and the pressure continues to rise, a test is performed. If P2 > P4 - X, where X represents a preset value, the system switches from full load to half load, that is, one of the two sets of intake valves is closed, reducing the air output by half. At the moment of switching to half load, the frequency needs to be increased from the lower limit to a higher level and maintained for a period of time (e.g., 10 seconds). Each time half load is switched, a different set of intake valves is used.

[0026] Step S106 includes: performing a detection; if |P2-P1|≤P3 is satisfied, the air compressor resumes the automatic frequency conversion adjustment stage based on flow rate changes; when the air consumption is greater than the air production, the system reduces the operating frequency, thereby reducing the air compressor speed to reduce the air production, thus lowering the exhaust pressure and moving closer to the target pressure; when the air consumption is less than the air production, the system increases the operating frequency, thereby increasing the air compressor speed to increase the air production, thus raising the exhaust pressure and moving closer to the target pressure.

[0027] Step S107 includes: performing a test; if P1 > P2 + P3, the air compressor quickly adjusts its operating frequency to the lower limit, maintains low-speed operation, reduces the amount of gas produced as soon as possible, and avoids further pressure increase.

[0028] Step S108 includes: When switching to half-load, if the air compressor's air output is still greater than the air consumption and the pressure continues to rise, a test is performed. If P1 > P4, the air compressor closes the remaining set of working intake valves, and the air compressor enters the unloading state. In the unloading state, the air compressor runs idle and does not produce air. After the air consumption resumes, the exhaust pressure continues to drop. A test is performed. If P1 < P2, the system returns to half-load operation from unloading.

[0029] Step S109 includes: when running at half load, if the operating frequency exceeds the limit frequency and the duration exceeds the set time, the system automatically switches back to full load. At the moment of switching to full load, the operating frequency is adjusted to the lower limit and maintained for a period of time (e.g., 10 seconds).

[0030] Beneficial effects: This invention maximizes the air volume adjustment range through a combination of frequency conversion and half-load air volume regulation. This allows for better matching of the air compressor's output with the air consumption of the bottle blowing line, improving the air compressor's load rate, directly reducing energy waste from unloading and idling. Furthermore, by avoiding frequent switching between loading and unloading, it further ensures the equipment's air production efficiency and reduces average operating power. Operational tests have verified that its performance is stable and reliable, demonstrating high application value. Attached Figure Description

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0032] Figure 1 This is a structural diagram of a reciprocating piston air compressor.

[0033] Figure 2 This is a flowchart of the method of the present invention. Detailed Implementation

[0034] This invention provides a composite air volume regulation method based on a reciprocating piston air compressor. By separately controlling the air valves on both sides of the air compressor cylinder, when the air compressor frequency adjustment to the lower limit still cannot match the air demand, the intake valve on one side of the cylinder is closed, causing the piston to change from bidirectional to unidirectional work within the cylinder, reducing air production by half and achieving a wider range of air volume regulation. Through better matching of air compressor output with production line air consumption, the air compressor's loading rate is improved, frequent loading / unloading switching is reduced, and energy waste is minimized.

[0035] The air volume compound regulation method based on a reciprocating piston air compressor of the present invention includes the following steps:

[0036] Step a. After the air compressor starts, it runs at full speed and full load. When the operating pressure reaches near the target pressure, the operating frequency is adjusted by comparing the deviation between the target pressure and the operating pressure or by the deviation between the air consumption and the air production to ensure the balance between the air production and the air consumption.

[0037] Step b. When the air compressor is running at full load, the pressure will inevitably rise when the air consumption decreases rapidly or falls below the lower limit of the air consumption adjustment of the frequency converter under full load. When the pressure approaches the unloading value, the system will automatically switch to half-load operation.

[0038] Step c. When the air compressor is running at half load, if the air consumption continues to decrease, and the frequency is adjusted to the lower limit, the air compressor's air output still cannot match the air consumption. Then the pressure continues to rise. After reaching the unloading value, the air compressor closes all air valves and stops producing air.

[0039] Step d. After the air compressor is unloaded, production resumes and air usage will inevitably decrease. When the pressure drops to the target pressure, the system will automatically resume half-load frequency regulation operation.

[0040] Step e. When the air compressor is running at half load, if the air consumption increases rapidly or exceeds the maximum air production that can be adjusted at half load, the pressure will continue to drop. In this case, you should switch back to full load in time.

[0041] Step f. When the air compressor is running at half load, if the air consumption is close to half of the air compressor's full load capacity, the air compressor will run at a higher frequency. Once this condition occurs, the system needs to automatically switch from half load to full load operation.

[0042] Step g. At the moment of switching from full load to half load, the air output drops by half. At this time, the system needs to simultaneously increase the speed of the air compressor to slow down the decrease in air output and avoid the pressure dropping too quickly, resulting in insufficient air supply pressure.

[0043] Step h. At the moment of switching from half load to full load, the gas production increases by half. If the pressure is high at this time, the speed of the air compressor must be reduced simultaneously to slow down the increase in gas production and avoid the pressure rising too quickly, which would cause the unit to unload.

[0044] Step I. In order to balance the working time of the air valves and ensure consistent lifespan, the air valves should be operated in rotation each time the half-load is switched. It is not possible to always have one side of the air valves working.

[0045] To better understand the above technical solution, a preferred control method of the present invention is provided below:

[0046] Parameter explanation:

[0047] P1: Air compressor discharge pressure; P2: Target operating pressure.

[0048] P3: Allowable deviation range of target pressure P4: Unloading pressure of air compressor

[0049] Q1: Air consumption of air-using equipment Q2: Air output of air compressor

[0050] Q3: Rated full-load air output of the air compressor; f: Operating frequency of the air compressor

[0051] Parameter acquisition:

[0052] P2: Set according to the usage requirements of gas-using equipment.

[0053] P1: Acquired through sensor measurement.

[0054] P3: Set according to the gas usage on site.

[0055] P4: Set according to the usage requirements of gas-using equipment.

[0056] Q1: Install a flow meter for testing.

[0057] Q3: Actual air output of the air compressor at full load 50Hz

[0058] Full-load Q gas production: (f / 50)*Q3

[0059] Half-load Q gas production: (f / 50)*Q3 / 2

[0060] The basic logic of the control method:

[0061] Because the efficiency of an air compressor is higher at full load than at half load, and because increasing the compressor's operating speed accelerates piston ring wear and increases the frequency of valve opening and closing, it is necessary to avoid operating the air compressor at high speed under half load to ensure the lifespan of vulnerable parts. The basic logic of the system is to prioritize the use of variable frequency speed control, and only switch to half-load regulation when variable frequency speed control cannot meet the adjustment needs. Only when the air consumption is much less than half of the full-load air consumption, for the sake of system stability, is it permissible to maintain half-load operation.

[0062] Running at full speed:

[0063] When P1 < P2 - P3, the system forces the inverter's "set value" to be higher than the "feedback value" to ensure the air compressor runs at full speed of 50Hz until P1 = P2.

[0064] Speed ​​limit operation:

[0065] When P1 > P2 + P3, the system forces the inverter's "set value" to be less than the "feedback value" to ensure that the air compressor frequency drops until it operates at the lower limit frequency, thus avoiding switching to half-load or no-load operation.

[0066] Automatic frequency conversion speed control:

[0067] When |P2-P1|≤P3, the "flow control frequency converter mode" is adopted, that is, Q1 is used as the "set value" of the frequency converter and Q2 is used as the "feedback value" of the frequency converter. The frequency converter adjusts the operating frequency of the air compressor through PID mode according to the changes of the set value and the feedback value to ensure the constant pressure operation of the air compressor.

[0068] The PID mode includes a proportional unit P, an integral unit I, and a derivative unit D. The relationship between the input e(t) and the output u(t) is as follows:

[0069] u(t)=kp[(e(t)+1 / TI∫e(t)dt+TD*de(t) / dt]

[0070] Where kp is the proportional coefficient, TI is the integral time constant, TD is the derivative time constant, d is the derivative sign, input e(t) represents the calculated deviation between the inverter feedback value and the set value, and u(t) represents the operating frequency;

[0071] When the theoretical calculation result of the air compressor output Q2 deviates from the actual result, the calculation result of Q2 is corrected: when Q1 > Q2, theoretically P1 should decrease; if P1 increases, it means that the calculated value of Q2 is greater than the actual value, and Q2 should be adjusted once. 2＝ Q2 + △Q; When Q1 < Q2, theoretically P1 should increase. If P1 decreases, it means that the calculated value of Q2 is less than the actual value, and Q2 = Q2 - △Q should be executed once.

[0072] The calculation method for the deviation △Q between the theoretical and actual air compressor output Q2: Within the cycle time T (unit: s), calculate the pressure difference △P (unit: bar), based on the air tank volume V (unit: m³). 3 ), Deviation gas volume △Q=△P*V(60 / T) (unit: Nm 3 / min); If the flow meter malfunctions, the "pressure control frequency conversion mode" is used, in which P2 is used as the "set value" of the frequency converter and P1 is used as the "feedback value" of the frequency converter.

[0073] Switch to uninstall:

[0074] When P1 > P4, the system closes all intake valves of the air compressor, stops producing air, and enters the unloading state.

[0075] Switching from full load to half load:

[0076] When running at full load: When P2 > P4-X, the system automatically switches to half load operation. At the moment of switching, the system forces the inverter's "set value" to be greater than the "feedback value", quickly raises the frequency to near the upper limit, and then resumes automatic frequency conversion adjustment; X represents the preset value, and the larger the air tank, the smaller X is set.

[0077] Half-load to full-load switching (two operating conditions):

[0078] Operating Condition 1: During half-load operation, the production air consumption suddenly increases rapidly. When P2-P1>P3, the system automatically switches back to full-load operation. At the moment of switching, the system forces the inverter's "set value" to be higher than the "feedback value" to ensure that the air compressor runs at full speed until P1=P2.

[0079] Operating Condition 2: During half-load operation, when |P2-P1|≤P3, the inverter's operating frequency is stably running in a higher range, and the system automatically switches back to full-load inverter operation; if at the moment of switching from half-load to full-load, P1>P2, the system forces the inverter's "set value" to be less than the "feedback value" to ensure that the air compressor frequency drops to the lower limit and then resumes automatic inverter regulation.

[0080] Uninstall and switch to semi-loaded:

[0081] When the system is unloaded, the production line resumes gas usage. Once P1 < P2, the system switches to half-load operation.

[0082] Balancing valve operating time:

[0083] The presence of the piston rod inevitably results in a larger volume on the non-piston rod side of the cylinder. This means that under half-load conditions, the non-piston rod side will be used for power production, resulting in slightly higher gas output than the piston rod side. However, since the piston rod's volume occupies a small proportion of the total compression chamber volume, this difference in gas volume is actually negligible. If only one set of valves is used, it can easily lead to inconsistent valve lifespans. Therefore, it is recommended to switch to the other set of valves each time half-load conditions are changed to ensure more consistent valve operating times.

[0084] Example

[0085] according to Figure 1 and Figure 2 As shown, this embodiment provides a method for combined air volume regulation based on a reciprocating piston air compressor, including: a pressure sensor 4 for controlling the pressure of the air compressor 2 is installed on the air tank 3, and a flow meter 5 is installed between the air tank 3 and the air-consuming device 6. The air compressor 2 is selected as Shangai brand M410-16040, an M-type reciprocating air compressor with an air volume of 16m³ / s. 3 The compressor operates at a speed of 160 kW per minute, with a rated pressure of 4.0 MPa. Two sets of intake valves can be controlled independently, allowing for half-load / full-load switching to adjust the air output. The accompanying control cabinet 1 features frequency conversion control, allowing adjustment of the air output by changing the compressor speed. The system is set to a target pressure of 3.1 MPa, a differential pressure of 0.1 MPa, and an unloading pressure of 3.3 MPa.

[0086] S101 uninstallation and startup, running frequency increased to the lower limit:

[0087] To achieve light-load startup and avoid impacting the power grid during startup, the air compressor is in an unloaded state during startup, meaning both sets of intake valves are closed; the frequency rises from 0Hz to the allowable lower limit frequency (25Hz) during startup, and the startup process lasts for 15 seconds.

[0088] S102 is running at full load and full speed:

[0089] After the air compressor starts, the system detects that P1 < P2 - P3, that is, the exhaust pressure < 3.0 MPa. Since the pressure deviates from the lower limit of use, the system switches to full-load operation and quickly adjusts the operating frequency to the upper limit (50 Hz) to maintain full-speed operation and ensure that the exhaust pressure approaches the target pressure as soon as possible.

[0090] During full-load operation of S103, variable frequency speed regulation is applied according to flow rate changes:

[0091] If the system detects that |P2-P1| ≤ P3, meaning the exhaust pressure is between 3.0 and 3.2 MPa, the air compressor enters the automatic frequency conversion adjustment stage based on flow rate changes. When the air consumption exceeds the air production, the system reduces the operating frequency, thereby reducing the air compressor speed to decrease the air production and lower the exhaust pressure, bringing it closer to the target pressure. Conversely, when the air consumption is less than the air production, the system increases the operating frequency, thereby increasing the air compressor speed to increase the air production and raise the exhaust pressure, bringing it closer to the target pressure.

[0092] Pressure-controlled frequency conversion mode can also be used at this stage, adjusting the operating frequency by utilizing the deviation between the target pressure and the operating pressure.

[0093] S104 operates at a limited speed:

[0094] When the air consumption decreases rapidly and the pressure rises, if the system detects that P1 > P2 + P3, i.e., the exhaust pressure > 3.2 MPa, the air compressor will quickly adjust its operating frequency to the lower limit (25 Hz) to maintain low-speed operation, reduce the air production as soon as possible, and avoid further pressure increase.

[0095] S105 switches to half-load operation:

[0096] When the operating frequency has been adjusted to the lower limit, but the air consumption is still less than the air compressor's output, and the pressure continues to rise, the system detects that P2 > P4 - X (preset value X is 0.05 MPa), i.e., the exhaust pressure > 3.25 MPa. The system then switches from full load to half load, closing one set of intake valves and reducing the air output by half. To avoid a rapid decrease in air output leading to a rapid drop in pressure, the frequency needs to be increased from the lower limit to a higher level (around 38 Hz) and maintained for several seconds at the moment of switching to half load. Additionally, to maintain consistent valve lifespan, a new set of intake valves should be used each time half load is switched.

[0097] During the half-load phase of S106, variable frequency speed control is applied according to flow rate changes:

[0098] If the system detects that |P2-P1| ≤ P3, meaning the exhaust pressure is between 3.0 and 3.2 MPa, the air compressor resumes its automatic frequency conversion adjustment phase based on flow rate changes. When air consumption exceeds air production, the system reduces its operating frequency, thereby reducing the air compressor speed to decrease air production and lower the exhaust pressure, bringing it closer to the target pressure. Conversely, when air consumption is less than air production, the system increases its operating frequency, thereby increasing the air compressor speed to increase air production and raise the exhaust pressure, bringing it closer to the target pressure.

[0099] S107 operates at a limited speed during the half-load phase:

[0100] When the air consumption decreases rapidly and the pressure rises, if the system detects that P1 > P2 + P3, i.e., the exhaust pressure > 3.2 MPa, the air compressor will quickly adjust its operating frequency to the lower limit (25 Hz) to maintain low-speed operation, reduce the air production as soon as possible, and avoid further pressure increase.

[0101] S108 Switch to Uninstallation and Run:

[0102] When switching to half-load operation, if the air compressor's output still exceeds the demand, the pressure continues to rise. The system detects that P1 > P4 (exhaust pressure > 3.3 MPa), and the air compressor closes the remaining set of operating intake valves, entering unload mode. In unload mode, the air compressor runs idle without producing air. Once demand resumes, the exhaust pressure continues to drop, and the system detects that P1 < P2 (exhaust pressure < 3.1 MPa), at which point the system returns to half-load operation.

[0103] When the S109 is running at half load and high speed, switch back to full load:

[0104] Because the efficiency of an air compressor is higher at full load than at half load, and increasing the compressor's operating speed will accelerate piston ring wear and increase the number of valve opening and closing times, it is necessary to avoid operating the air compressor at high speed under half load to ensure the life of vulnerable parts. Therefore, when operating at half load, if the operating frequency exceeds the limit frequency (38Hz is recommended) and the duration exceeds the set time (1-2 minutes), the system will automatically switch back to full load. To avoid the problem of excessively rapid increase in air output and pressure rise during the switch to full load, the operating frequency should be adjusted to the lower limit (25Hz) and maintained for several seconds at the moment of switching to full load.

[0105] This example provides a method for combined air volume regulation based on a reciprocating piston air compressor. Based on frequency conversion regulation, when the compressor's operating frequency drops to its lower limit and the air production still cannot match the air demand, the compressor switches to half-load operation, i.e., closing half of the intake valve to reduce air production and match the smaller air demand. This invention maximizes the air volume regulation range of the air compressor through combined frequency conversion and half-load regulation, enabling better matching between the compressor's air production and the air demand of the bottle blowing line, improving the compressor's load rate, and directly reducing energy waste from unloading and idling. Furthermore, by avoiding frequent switching between loading and unloading, it further ensures the equipment's air production efficiency and reduces average operating power. The control method described in this invention has a simple program, reliable control, and has proven to be effective in practice, demonstrating high application value.

[0106] In its specific implementation, this application provides a computer storage medium and a corresponding data processing unit. The computer storage medium is capable of storing a computer program, which, when executed by the data processing unit, can run the invention's content regarding a method for combined air volume regulation based on a reciprocating piston air compressor, as well as some or all of the steps in various embodiments. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0107] Those skilled in the art will clearly understand that the technical solutions in the embodiments of the present invention can be implemented using computer programs and their corresponding general-purpose hardware platforms. Based on this understanding, the technical solutions in the embodiments of the present invention, or the parts that contribute to the prior art, can be embodied in the form of computer programs, i.e., software products. These computer program software products can be stored in a storage medium and include several instructions to cause a device containing a data processing unit (which may be a personal computer, server, microcontroller, MUU, or network device, etc.) to execute the methods described in various embodiments or certain parts of the embodiments of the present invention.

[0108] This invention provides a method for combined air volume regulation based on a reciprocating piston air compressor. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for combined air volume regulation based on a reciprocating piston air compressor, characterized in that, Includes the following steps: Step S101: Uninstall startup, increase running frequency to the lower limit; Step S102: Run at full load and full speed; Step S103, full load stage, variable frequency speed control operation; Step S104, speed-limited operation; Step S105: Switch to half-load operation; Step S106, half-load stage, variable frequency speed control operation; Step S107, half-load stage, speed-limited operation; Step S108: Switch to uninstallation and run; Step S109: When running at half load and high speed, switch back to full load; Step S105 includes: when the operating frequency has been adjusted to the lower limit, the air consumption is still less than the air compressor output, and the pressure continues to rise, a test is performed. If P2 > P4 - X, where X represents a preset value, the system switches from full load to half load, that is, one of the two sets of intake valves is closed, reducing the air output by half. At the moment of switching to half load, the frequency needs to be increased from the lower limit to a higher limit and maintained for a period of time. Each time half load is switched, a different set of intake valves is used. Step S106 includes: performing a detection; if |P2-P1| ≤ P3, the air compressor resumes the automatic frequency conversion adjustment stage based on flow rate changes; when the air consumption is greater than the air production, the system reduces the operating frequency, thereby reducing the air compressor speed to reduce the air production, thus lowering the exhaust pressure and moving closer to the target pressure; when the air consumption is less than the air production, the system increases the operating frequency, thereby increasing the air compressor speed to increase the air production, thus raising the exhaust pressure and moving closer to the target pressure. Step S107 includes: performing a detection; if P1 > P2 + P3 is satisfied, the air compressor quickly adjusts its operating frequency to the lower limit, maintains low-speed operation, reduces the amount of gas produced as soon as possible, and avoids further pressure increase. Step S108 includes: When switching to half-load, if the air compressor's air output is still greater than the air consumption and the pressure continues to rise, a test is performed. If P1 > P4, the air compressor closes the remaining set of working intake valves, and the air compressor enters the unloading state. In the unloading state, the air compressor runs idle and does not produce air. After the air consumption resumes, the exhaust pressure continues to drop. A test is performed. If P1 < P2, the system returns to half-load operation from unloading. P1 is the air compressor's exhaust pressure, P2 is the target pressure, P3 is the allowable deviation range of the target pressure, and P4 is the air compressor's unloading pressure.

2. The method according to claim 1, characterized in that, Step S101 includes: during startup, the air compressor is in an unloaded state, that is, both sets of intake valves are closed; during startup, the frequency rises from 0 Hz to the allowable lower limit frequency, and the startup process lasts for Y seconds.

3. The method according to claim 2, characterized in that, Step S102 includes: After the air compressor starts, a test is performed. If P1 < P2 - P3 is satisfied, the system switches to full-load operation and the operating frequency is quickly adjusted to the upper limit to maintain full-speed operation, ensuring that the exhaust pressure approaches the target pressure as soon as possible; where P1 represents the exhaust pressure of the air compressor, P2 represents the target pressure used, and P3 represents the allowable deviation range of the target pressure.

4. The method according to claim 3, characterized in that, Step S103 includes: performing a detection; if |P2-P1| ≤ P3, the air compressor enters the flow control frequency conversion mode, with Q1 as the set value of the frequency converter and Q2 as the feedback value of the frequency converter. When the air consumption is greater than the air production, the system reduces the operating frequency, thereby reducing the air compressor speed to reduce the air production, thus lowering the exhaust pressure and moving closer to the target pressure; when the air consumption is less than the air production, the system increases the operating frequency, thereby increasing the air compressor speed to increase the air production, thus raising the exhaust pressure and moving closer to the target pressure. Q1 is the air consumption of the air-using equipment, and Q2 is the air production of the air compressor.

5. The method according to claim 3, characterized in that, Step S103 includes: performing a detection; if |P2-P1|≤ P3 is satisfied, the air compressor enters the pressure control frequency conversion mode, with P2 as the set value of the frequency converter and P1 as the feedback value of the frequency converter. The frequency converter adjusts the operating frequency of the air compressor through PID mode according to the changes in the set value and the feedback value to ensure the constant pressure operation of the air compressor.

6. The method according to claim 5, characterized in that, In step S103, the PID mode includes a proportional unit P, an integral unit I, and a derivative unit D. The relationship between the input e(t) and the output u(t) is as follows: u(t)=kp[(e(t)+1 / TI∫e(t)dt+TD*de(t) / dt], Where kp is the proportional coefficient, TI is the integral time constant, TD is the derivative time constant, d is the derivative sign, input e(t) represents the calculated deviation between the inverter feedback value and the set value, and u(t) represents the operating frequency; When the theoretical calculation result of the air compressor output Q2 deviates from the actual result, the calculation result of Q2 is corrected: when Q1 > Q2, theoretically P1 should decrease; if P1 increases, it means that the calculated value of Q2 is greater than the actual value, then Q is corrected once. 2= Q2 + △Q; When Q1 < Q2, theoretically P1 should increase. If P1 decreases, it means that the calculated value of Q2 is less than the actual value, so execute Q2 = Q2 - △Q once; Q1 is the gas consumption of the gas-using equipment. The calculation method for the deviation △Q between the theoretical and actual air output Q2 of the air compressor: Within the cycle time T, calculate the pressure difference △P. Based on the air tank volume V, the deviation air output △Q = △P*V (60 / T). If the flow meter fails, the pressure control frequency conversion mode is adopted, with P2 as the set value of the frequency converter and P1 as the feedback value of the frequency converter.

7. The method according to claim 4 or 6, characterized in that, Step S104 includes: performing a detection; if P1 > P2 + P3, the air compressor quickly adjusts its operating frequency to the lower limit, maintains low-speed operation, and reduces the amount of air produced.

8. The method according to claim 7, characterized in that, Step S109 includes: when running at half load, if the operating frequency exceeds the limit frequency and the duration exceeds the set time, the system automatically switches back to full load. At the moment of switching to full load, the operating frequency is adjusted to the lower limit and maintained for a period of time.

Images