Diaphragm compressor oil mass self-balancing system and control method

Abstract

According to the diaphragm compressor oil mass self-balancing system and the control method, the needed oil supplementing amount and the working state of a diaphragm compressor are calculated and judged through measurement data of exhaust pressure, transient oil pressure and the oil supplementing amount, and data are measured through a pressure sensor and a flow meter and transmitted to a control unit; the required oil supplementing amount is calculated, the working state of the diaphragm compressor is judged, the opening degree of a proportional overflow valve on an oil supplementing loop is controlled, accurate automatic control over the hydraulic oil amount of an oil cavity of the diaphragm compressor and dynamic balance of the oil amount are achieved, and the problem that an executing mechanism acts too frequently can be solved through the oil supplementing method; the overflow valve realizes the change of the oil discharge pressure along with the exhaust pressure, and avoids the problem caused by higher oil pressure. The problem that the diaphragm flaps the cylinder due to the fact that the oil quantity of the oil cavity is reduced under the conditions of starting, working condition change, piston ring abrasion and the like can be effectively solved.

Description

Technical Field

[0001] The present invention belongs to the field of compressors and relates to a diaphragm compressor oil quantity self-balancing system and a control method thereof. Background Art

[0002] In a diaphragm compressor, a diaphragm divides it into a gas chamber and an oil chamber. The diaphragm is deformed by hydraulic oil driven by a piston to achieve gas compression. It has the advantages of good sealing performance, large compression ratio, and high purity of compressed gas. It is commonly used for compressing clean gas, high-purity gas, toxic and dangerous gas, etc., and is a key equipment for gas pressurization in various industries. The high maintenance cost caused by the diaphragm life problem of the diaphragm compressor is one of the important factors restricting its development.

[0003] When the diaphragm compressor is operating, the hydraulic oil inevitably leaks from the piston ring, resulting in a decrease in the hydraulic oil quantity in the oil chamber. If the oil is not replenished in time, the diaphragm of the diaphragm compressor will not contact the wall surface of the gas-side diaphragm chamber, increasing the clearance volume and reducing the gas volume. When the oil quantity in the chamber is small, the phenomenon of "diaphragm hitting the cylinder" will occur, reducing the diaphragm life. Therefore, a plunger pump must be set in the diaphragm compressor to replenish hydraulic oil into the oil chamber in time. The plunger pump is driven by an eccentric wheel at the crankshaft end and forms a certain phase difference with the piston movement of the diaphragm compressor. Usually, oil replenishment is carried out during the suction stage of the compressor.

[0004] The stroke volume of the plunger pump is designed according to the empirical leakage amount of the hydraulic oil in the compressor cylinder. Generally, it is larger than the leakage amount of the hydraulic oil. However, in order to avoid excessive oil replenishment leading to an increase in the power consumption of the compressor, the stroke volume of the plunger pump is often designed with an empirical value relative to the volume ratio of the oil chamber. There is an upper limit to the oil replenishment amount of the plunger pump, and there are the following situations where the oil quantity in the cylinder still decreases under the existing oil replenishment. When the piston ring of the diaphragm compressor or the plunger pump is damaged more severely, the leakage amount of the hydraulic oil increases and the oil replenishment amount decreases, resulting in a decrease in the oil quantity in the cylinder. During the starting stage, the pressure of the diaphragm compressor gradually builds up. At this time, the compression amount of the hydraulic oil is less than that in the design condition, and the oil discharge amount of the oil cylinder is greater than the oil replenishment amount, resulting in a decrease in the oil quantity in the cylinder. However, as the pressure gradually builds up, the oil replenishment amount and the oil discharge amount reach balance. When the operating condition of the compressor fluctuates, such as the exhaust pressure decreases, the oil discharge pressure also decreases, resulting in a larger oil discharge amount compared with the design condition. When the oil replenishment amount is fixed, the oil quantity in the chamber decreases. The plunger pump designed according to traditional experience cannot meet the oil replenishment amount required in the above situations, and the volumetric efficiency and diaphragm life of the diaphragm compressor will be affected. Summary of the Invention

[0005] The object of the present invention is to provide a diaphragm compressor oil quantity self-balancing system and a control method, so as to overcome the problem of diaphragm flapping caused by the reduction of the hydraulic oil quantity in the oil chamber of the diaphragm compressor under conditions such as starting, working condition changes, and piston ring wear in the prior art. The present invention realizes the precise control and automatic adjustment of the oil replenishment quantity, prevents problems such as diaphragm flapping caused by less oil replenishment quantity, improves the adaptability of the diaphragm compressor to working condition changes, provides more time for fault diagnosis and response such as piston ring wear, and ensures the stable operation of the diaphragm compressor in different working condition stages.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: A diaphragm compressor oil quantity self-balancing system includes a first plunger pump, a second plunger pump, and a proportional overflow valve. The first plunger pump and the second plunger pump are connected in parallel. The inlets of the first plunger pump and the second plunger pump are communicated with the crankcase of the diaphragm compressor, and the outlets of the first plunger pump and the second plunger are communicated with the oil chamber of the diaphragm compressor. The proportional overflow valve is arranged between the outlet of the second plunger pump and the crankcase of the diaphragm compressor.

[0007] Preferably, check valves are arranged at the outlet ends of the first plunger pump and the second plunger pump.

[0008] Preferably, an overflow valve is further included, and the overflow valve is arranged between the oil chamber and the crankcase.

[0009] Preferably, the phase angle between the first plunger pump and the second plunger pump is 0°.

[0010] Preferably, a control unit is further included. The control unit is connected to the proportional overflow valve. A transient oil pressure sensor arranged on the oil chamber and an exhaust pressure sensor communicated with the air chamber are also included. Both the transient oil pressure sensor and the exhaust pressure sensor are connected to the control unit 11.

[0011] Preferably, the stroke volume of the first plunger pump is designed according to the leakage amount of the hydraulic oil along the gap of the piston ring of the diaphragm compressor. The leakage amount of the hydraulic oil of the diaphragm compressor along the gap of the piston ring conforms to the following calculation formula:

[0012] In the formula, m l is the leakage amount at the gap of piston 4; is the density of the hydraulic oil; is the unilateral clearance value of the ring; d is the clearance diameter of the ring; l is the clearance length; is the leakage pressure difference on both sides of the clearance in the length direction; is the dynamic viscosity of the hydraulic oil; The stroke volume of the first plunger pump:

[0013] In the formula, is the design coefficient representing the volume margin, which is greater than 1; is the density under the oil inlet state of the first plunger pump.

[0014] Preferably, the ratio of the stroke volume of the second plunger pump to the piston stroke volume of the diaphragm compressor is set to 3% - 30%. When the design working condition pressure of the diaphragm compressor is relatively high and the ratio of the total oil cavity volume to the piston stroke volume is relatively high, a larger value is selected for the above ratio.

[0015] A control method for the oil quantity self - balancing system of a diaphragm compressor includes the following steps: When the diaphragm compressor is in the designed working state, the proportional overflow valve on the oil replenishing return circuit of the second plunger pump is in the fully open state; When the wear amount at the piston of the diaphragm compressor increases or the wear at the plunger clearance of the first plunger pump increases, the leakage amount at the piston clearance of the diaphragm compressor increases or the oil replenishing amount in the oil cavity decreases, and the hydraulic oil quantity in the oil cavity of the diaphragm compressor decreases; When the diaphragm compressor is in the initial starting stage and the measured exhaust pressure is less than the exhaust pressure under the designed working condition, the first plunger pump and the second plunger pump work together to replenish oil to the oil cavity of the diaphragm compressor simultaneously.

[0016] Preferably, when the measured exhaust pressure is equal to the exhaust pressure under the designed working condition, the maximum oil pressure in the oil cavity of the diaphragm compressor is equal to or slightly greater than the designed oil discharge pressure, the minimum oil pressure is close to the suction pressure, the oil discharge amount is less than or equal to the maximum oil replenishing amount of the first plunger pump under the designed working condition of the diaphragm compressor, and the proportional overflow valve on the oil replenishing return circuit of the second plunger pump is in the fully open state; The overflow mass calculation formula of the overflow valve on the oil discharge pipeline is as follows:

[0017] In the formula, is the overflow mass of the overflow valve; is the overflow time of the overflow valve; is the flow coefficient; is the effective flow area corresponding to the valve opening; is the pressure difference across the valve orifice of the overflow valve, which is the difference between the oil discharge pressure of the diaphragm compressor and the tank pressure here; is the density of the hydraulic oil.

[0018] Preferably, when the diaphragm compressor is in the starting stage or the operating pressure is in a lower working condition, measure the exhaust pressure p gd less than the exhaust pressure under the designed working condition pgd ’; Specifically, when 0.2 p gd ’ < p gd < p gd ’, calculate the hydraulic oil overflow mass according to the transient oil pressure measured by the transient oil pressure sensor in the previous cycle; the oil replenishment mass required by the diaphragm compressor in the current cycle is equal to the sum of the overflow mass and the leakage amount at the piston gap; if the required oil replenishment amount is less than or equal to the maximum oil replenishment amount provided by the first plunger pump, the first plunger pump replenishes oil to the oil chamber of the diaphragm compressor, and the proportional overflow valve on the oil replenishment circuit of the second plunger pump is in the fully open state; if the required oil replenishment amount is greater than the maximum oil replenishment amount provided by the first plunger pump, the first plunger pump and the second plunger pump work together to replenish oil to the oil chamber of the diaphragm compressor at the same time, and the opening formula of the proportional overflow valve is as follows: .

[0019] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention provides a diaphragm compressor oil quantity self-balancing system. By setting two plunger pumps, calculating and judging the required oil replenishment amount and the working state of the diaphragm compressor through the measured data of the exhaust pressure, transient oil pressure and oil replenishment amount, and combining with the PLC control unit to control the oil replenishment amount of the plunger pump, the accurate automatic control of the oil quantity in the oil chamber of the diaphragm compressor is realized, and the problem of too frequent actions in the control process is avoided; the problems such as diaphragm slapping the cylinder caused by the reduction of the hydraulic oil quantity in the oil chamber of the diaphragm compressor in case of starting, working condition change, piston ring wear, etc. are solved. The overflow valve can effectively avoid the large concentrated stress at the corresponding intake and exhaust holes when the diaphragm contacts the gas side due to the large oil-gas pressure difference, ensuring the smoothness and reliability of the diaphragm compressor in different working condition stages. In addition, the present invention can help judge the cause of the fault of less oil quantity and provide early warning for the problems of piston ring wear and plunger wear of the plunger pump.

[0020] A control method for the diaphragm compressor oil quantity self-balancing system of the present invention uses the measured data of the pressure sensor and the flowmeter to be transmitted to the control unit, calculates the required oil replenishment amount and judges the working state of the diaphragm compressor, controls the opening of the proportional overflow valve on the oil replenishment circuit, realizes the accurate automatic control of the hydraulic oil quantity in the oil chamber of the diaphragm compressor and the dynamic balance of the oil quantity, and the proposed oil replenishment method can reduce the problem of too frequent actions of the actuator; the overflow valve realizes the change of the oil discharge pressure with the exhaust gas pressure, avoiding the problems caused by too high oil pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the diaphragm compressor oil quantity self-balancing system in the embodiment of the present invention.

[0022] Figure 2This is a schematic diagram of the oil replenishment control process for a diaphragm compressor in an embodiment of the present invention.

[0023] Figure 3 This is a flowchart of the specific process of oil replenishment control under different conditions in an embodiment of the present invention.

[0024] In the figure, 1 is a diaphragm; 21 is a cylinder head; 22 is an air chamber; 23 is an oil chamber; 24 is a cylinder block; 3 is an overflow valve; 4 is a piston; 5 is a filter screen; 6 is a crankcase; 71 is a first plunger pump; 72 is a second plunger pump; 81 is a first one-way valve; 82 is a second one-way valve; 91 is a mass flowmeter; 92 is a transient oil pressure sensor; 93 is an exhaust pressure sensor; 10 is a proportional overflow valve; 11 is a control unit; 12 is an oil replenishment pipeline; 13 is an oil replenishment circuit; 14 is an oil discharge pipeline. Specific embodiments

[0025] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0027] On the one hand, the present invention, as Figure 1As shown in the figure, a self-balancing system for the oil quantity of a diaphragm compressor oil is provided. The diaphragm compressor includes a cylinder block 24 and a cylinder head 21. A crankcase 6 is arranged inside the cylinder block 24. The crankcase 6 is connected to a piston cylinder. A piston 4 is arranged inside the piston cylinder. The upper end of the piston cylinder is connected to an oil chamber 23. A diaphragm 1 is arranged on the oil chamber 23. The cylinder head 21 is arranged on the oil chamber 23. The diaphragm 1 isolates the air chamber formed by the oil chamber 23 and the cylinder head 21. The self-balancing system includes a first plunger pump 71, a second plunger pump 72, a proportional overflow valve 10, a make-up oil pipeline 12, a make-up oil circuit 13, an overflow valve 3, the crankcase 6, a transient oil pressure sensor 92, an exhaust pressure sensor 93, a flowmeter 91, and a PLC control unit 11. The first plunger pump 71 and the second plunger pump 72 are respectively connected to the oil chamber 23 of the diaphragm compressor and the crankcase 6 through the make-up oil pipeline 12. A first one-way valve 81 and a second one-way valve 82 are respectively arranged on the make-up oil pipeline 12 at the outlet ends of the first plunger pump 71 and the second plunger pump 72. The make-up oil circuit 13 connects the second plunger pump 72 and the crankcase 6. The proportional overflow valve 10 is arranged on the make-up oil circuit 13. The opening degree of the proportional overflow valve 10 is controlled by the PLC control unit 11. The input signals of the PLC control unit 11 are the measurement data of the transient oil pressure sensor 92, the exhaust pressure sensor 93, and the mass flowmeter 91. During the oil drainage stage of the diaphragm compressor, the overflow valve 3 drains the excess hydraulic oil to the crankcase 6 along the oil drainage pipeline 14. The second plunger pump 72 adjusts the make-up oil quantity according to the instructions of the PLC control unit 11 to make the hydraulic oil quantity in the oil chamber 23 of the diaphragm compressor reach dynamic balance.

[0028] Specifically, the plunger pump is composed of a parallel connection of a first plunger pump 71 and a second plunger pump 72. The phase angles of the first plunger pump 71 and the second plunger pump 72 are 0°. After the first plunger pump 71 and the second plunger pump 72 are respectively driven by eccentric wheels and pass through the first one-way valve 81 and the second one-way valve 81 on their respective oil paths, they flow into the oil chamber 23 of the diaphragm compressor during the suction stage of the diaphragm compressor.

[0029] Specifically, the leakage quantity of the hydraulic oil of the diaphragm compressor along the gap at the piston ring conforms to the following calculation formula:

[0030] In the formula, is the leakage quantity at the gap of the piston 4, and the unit is kg • s -1 ; ρ is the density of the hydraulic oil, and the unit is kg • m -3 ; δ is the value of the unilateral clearance of the ring, and the unit is m; d is the diameter of the ring gap, and the unit is m; l is the length of the gap, and the unit is m; is the leakage pressure difference on both sides of the gap in the length direction, and the unit is Pa; μis the dynamic viscosity of the hydraulic oil, with the unit of Pa • s.

[0031] Specifically, the stroke volume of the first plunger pump 71 can be described by the following formula:

[0032] In the formula, is the designed stroke volume of the first plunger pump 71, with the unit of m 3 ; Since the hydraulic oil is compressible, to ensure that the oil replenishment amount can meet the requirements of the diaphragm compressor, is the design coefficient, greater than 1, representing the volume margin; is the density of the first plunger pump 71 under the oil inlet state, with the unit of kg • m -3 .

[0033] Specifically, the ratio of the stroke volume of the second plunger pump 72 to the stroke volume of the piston 4 of the diaphragm compressor is set to 3% - 30%; when the design working condition pressure of the diaphragm compressor is relatively high and the ratio of the total volume of the oil chamber to the piston stroke volume is relatively high, a larger value is selected for the above ratio.

[0034] An oil replenishment control method for an oil quantity self - balancing system of a diaphragm compressor is implemented using the above - mentioned oil quantity self - balancing system of the diaphragm compressor; the oil replenishment control process is as Figure 2 , and specifically includes the following steps: When the diaphragm compressor is in the designed working state, the proportional overflow valve on the oil replenishment return circuit of the second plunger pump is in the fully open state; When the wear amount at the piston of the diaphragm compressor increases or the wear at the plunger gap of the first plunger pump increases, the leakage amount at the piston gap of the diaphragm compressor increases or the oil replenishment amount in the oil chamber decreases, and the hydraulic oil quantity in the oil chamber of the diaphragm compressor decreases; When the diaphragm compressor is in the initial starting stage and the measured exhaust pressure is less than the exhaust pressure under the designed working condition, the first plunger pump and the second plunger pump work together to replenish oil to the oil chamber of the diaphragm compressor simultaneously.

[0035] Specifically, as Figure 3 shown in C1, when the diaphragm compressor is in the designed working state, specifically, the measured exhaust pressure p gd is equal to the exhaust pressure under the designed working condition p gd ’, the maximum oil pressure in the oil chamber of the diaphragm compressor p omax is equal to or slightly greater than the designed oil discharge pressure p od ’, and the minimum oil pressure p omin is close to the suction pressure pgs ’, the oil discharge volume m od is less than or equal to the maximum oil make-up volume of the first piston pump 71 under the design conditions of the diaphragm compressor m os1max : Set the proportional overflow valve 10 on the oil make-up circuit 13 of the second piston pump 72 to the fully open state, that is, the opening degree x is 1.

[0036] The overflow mass calculation formula of the overflow valve 3 on the oil discharge pipeline 14 is as follows:

[0037] In the formula, is the overflow mass of the overflow valve 3, and the unit is kg; is the overflow time of the overflow valve 3, and the unit is s; is the flow coefficient; is the effective flow area corresponding to the valve opening, and the unit is m 2 ; is the pressure difference across the valve port of the overflow valve 3, here it is the difference between the oil discharge pressure and the tank pressure of the diaphragm compressor, and the unit is Pa; is the density of the hydraulic oil, and the unit is kg • m -3 .

[0038] C2, when the wear amount at the piston 4 of the diaphragm compressor increases or the wear at the piston clearance of the first piston pump 71 increases, the leakage amount at the piston clearance of the diaphragm compressor increases or the oil make-up amount in the oil chamber decreases, and the hydraulic oil amount in the oil chamber 23 of the diaphragm compressor decreases; specifically, when the diaphragm compressor changes from the normal working state of p gd = p gd ’ p omax ≥ p od ’ to p gd = p gd ’ p gd ’ < p omax < p od ’ later: a. Calculate the oil make-up mass based on the flow rate measured by the oil make-up flowmeter in the previous cycle m os , if the oil make-up mass m os is equal to the oil make-up volume of the first piston pump under the design conditions mos ', representing the increase in the wear of the piston ring of the diaphragm compressor: the hydraulic oil overflow mass is calculated based on the transient oil pressure measured by the pressure sensor in the previous cycle m od , calculate the leakage amount of the previous cycle m ol = m os - m od ; The amount of oil required for the diaphragm compressor in this cycle m osn The amount is the actual leakage of hydraulic oil at the piston ring gap m ol Oil spill volume under design conditions m od 'sum (i.e. m osn = m ol + m od '); The first plunger pump 71 and the second plunger pump 72 work together to simultaneously replenish oil to the diaphragm compressor oil chamber 23 to reach the required oil replenishment amount; The calculation formula for the opening of the proportional relief valve 10 applicable to condition a in working condition C2 is as follows:

[0039] In the formula, x is the opening of the proportional relief valve 10d, in m; k is a geometric constant, which is related to the valve core structure; m os2max is the maximum oil replenishment mass of the second plunger pump 72, calculated according to the oil replenishment and discharge pressure and stroke volume of the plunger pump, in kg; m osn is the amount of oil replenishment required for the diaphragm compressor, in kg; m os1max is the maximum oil replenishment mass of the first plunger pump 71, calculated according to the oil replenishment and discharge pressure and stroke volume of the plunger pump, in kg; t is the overflow time of the proportional overflow valve, in s; C d is the flow coefficient; A is the effective flow area corresponding to the valve opening, in m 2 ;△ p is the pressure difference across the valve port of the proportional relief valve 10, which is the difference between the oil replenishment pressure of the diaphragm compressor and the oil tank pressure, in Pa; ρ is the density of hydraulic oil, in kg • m -3 ; b. If the oil filling qualitym os Less than the oil replenishment amount under the design operating condition of the first plunger pump m os ’, representing an increase in the hydraulic oil leakage at the plunger clearance of the first plunger pump 71. According to the actual leakage amount of the hydraulic oil at the piston ring clearance measured by the pressure sensor in the previous cycle m ol , if the actual leakage amount m ol is equal to the leakage amount under the design operating condition m ol ’: The oil replenishment amount required for the diaphragm compressor in this cycle m osn is the oil replenishment amount under the design operating condition of the first plunger pump 71 m os ’ (i.e., m osn = m os ’); c, if the oil replenishment mass m os is less than the oil replenishment amount under the design operating condition of the first plunger pump 71 m os ’, and according to the actual leakage amount of the hydraulic oil at the piston 4 clearance measured by the pressure sensor in the previous cycle m ol is greater than the leakage amount under the design operating condition m ol ’: The oil replenishment amount required for the diaphragm compressor in this cycle m osn is the sum of the oil replenishment amount under the design operating condition of the first plunger pump 71 m os ’ and the difference between the actual leakage amount at the piston 4 clearance of the diaphragm compressor m ol and the design leakage amount m ol ’ (i.e., m osn = m os ’ + m ol - m ol ’). The first plunger pump 71 and the second plunger pump 72 work together to replenish oil to the oil chamber 23 of the diaphragm compressor to reach the required oil replenishment amount; The opening formula of the proportional overflow valve 10 applicable to cases b and c in operating condition C2 is as follows:

[0040] In the formula, is the maximum oil replenishment mass of the first plunger pump 71. Under this operating condition, the wear amount at the plunger clearance of the first plunger pump increases, and the maximum oil replenishment mass is the actual oil replenishment amount of the first plunger pump 71 m os , with the unit of kg.

[0041] When the maximum oil pressure of the diaphragm compressor after oil replenishment regulation under the operating condition C2 p omax is greater than or equal to the designed oil discharge pressure ≥ p od ’, continue to maintain the above oil replenishment regulation method; when the required oil replenishment amount m osn reaches twice the required oil replenishment amount under the designed operating condition m os ’, the wear problems of the piston ring of the diaphragm compressor and the plunger of the first plunger pump 71 are serious, and a fault repair warning value is created based on the above-mentioned oil replenishment amount.

[0042] C3. When the diaphragm compressor is in the initial starting stage, measure the exhaust pressure p gd is less than the exhaust pressure under the designed operating condition p gd ’; specifically, when p gd <0.2 p gd ’: the proportional overflow valve 10 on the oil replenishment return circuit of the second plunger pump 72 is in the closed state, that is, the opening degree x is 0; the first plunger pump 71 and the second plunger pump 72 work together to replenish oil to the oil chamber 23 of the diaphragm compressor at the same time, and the oil replenishment mass is calculated based on the oil replenishment flow measured by the mass flowmeter 91 on the oil replenishment pipeline 12 m os ; after oil replenishment, the piston 4 of the diaphragm compressor moves upward to the top dead center to compress the gas. When the piston 4 moves to the top dead center, the diaphragm compressor starts to discharge oil. When the piston 4 reaches the top dead center and moves downward into the expansion stage, the overflow mass of the overflow valve is calculated based on the transient oil pressure measured by the transient oil pressure sensor 92 m od , if the overflow mass of the diaphragm compressor m od is less than or equal to the actual oil replenishment mass m os , maintain the above oil replenishment control method.

[0043] C4. When the diaphragm compressor is in the starting stage or the operating pressure is low, measure the exhaust pressure pgd less than the exhaust pressure under the design condition p gd ’; specifically, when 0.2 p gd ’ < p gd < p gd ’: Calculate the hydraulic oil overflow mass according to the transient oil pressure measured by the pressure sensor 92 in the previous cycle ; the mass of oil to be supplemented required by the diaphragm compressor in the current cycle is equal to the overflow mass and the designed leakage amount at the piston gap m ol ’; if the required oil replenishment amount is less than or equal to the maximum oil replenishment amount provided by the first plunger pump 71 , the first plunger pump 71 replenishes oil to the oil chamber 23 of the diaphragm compressor, and the proportional overflow valve 10 on the oil replenishment circuit 13 of the second plunger pump 72 is in the fully open state, that is, the opening degree x is 1; if the required oil replenishment amount is greater than the maximum oil replenishment amount provided by the first plunger pump 71 , the first plunger pump 71 and the second plunger pump 72 work together to replenish oil to the oil chamber 23 of the diaphragm compressor at the same time, and the opening degree calculation formula of the proportional overflow valve 10 is as follows: .

[0044] The present invention provides a diaphragm compressor oil quantity self - balancing system and control method. By setting two plunger pumps, calculating and judging the required oil replenishment amount and the working state of the diaphragm compressor through the measurement data of the exhaust pressure, transient oil pressure and oil replenishment amount, and combining with the PLC control unit to control the oil replenishment amount of the plunger pump, the precise automatic control of the oil quantity in the oil chamber of the diaphragm compressor is realized, and the problem of too frequent actions in the control process is avoided; it solves the problems such as diaphragm flapping caused by the reduction of the hydraulic oil quantity in the oil chamber of the diaphragm compressor in cases such as starting, working condition change, piston ring wear, etc. The overflow valve can effectively avoid the large concentrated stress at the corresponding intake and exhaust holes when the diaphragm contacts the gas side due to a large oil - gas pressure difference, ensuring the smoothness and reliability of the diaphragm compressor during different working condition stages. In addition, the present invention can help judge the cause of the fault of less oil quantity, provide an early warning for piston ring wear and plunger wear of the plunger pump. This system can realize the precise control and automatic adjustment of the oil replenishment amount, prevent problems such as diaphragm flapping caused by less oil replenishment amount, improve the adaptability of the diaphragm compressor to working condition changes, provide more time for fault diagnosis and response such as piston ring wear, and ensure the stable operation of the diaphragm compressor during different working condition stages.

Claims

1. An oil quantity self-balancing system for diaphragm compressor, characterized in that, It includes a first plunger pump (71), a second plunger pump (72) and a proportional overflow valve (10). The first plunger pump (71) and the second plunger pump (72) are in parallel. The inlet ports of the first plunger pump (71) and the second plunger pump (72) are connected to the crankcase of the diaphragm compressor. The outlet ports of the first plunger pump (71) and the second plunger pump (72) are connected to the oil chamber of the diaphragm compressor. The proportional overflow valve (10) is arranged between the outlet port of the second plunger pump (72) and the crankcase of the diaphragm compressor.

2. The oil quantity self-balancing system of a diaphragm compressor oil according to claim 1, characterized in that Check valves are arranged at the outlet ends of the first plunger pump (71) and the second plunger pump (72).

3. The oil quantity self-balancing system for diaphragm compressor oil according to claim 1, characterized in that It also includes an overflow valve (3), and the overflow valve (3) is arranged between the oil chamber (23) and the crankcase (6).

4. A diaphragm compressor oil quantity self-balancing system according to claim 1, characterized in that, The phase angle between the first plunger pump (71) and the second plunger pump (72) is 0°.

5. The oil quantity self-balancing system for diaphragm compressor oil according to claim 1, characterized in that, It also includes a control unit (11). The control unit (11) is connected to the proportional overflow valve (10). It also includes a transient oil pressure sensor (92) arranged on the oil chamber (23) and an exhaust pressure sensor (93) connected to the air chamber (22). Both the transient oil pressure sensor (92) and the exhaust pressure sensor (93) are connected to the control unit (11).

6. The oil quantity self-balancing system of a diaphragm compressor according to claim 1, characterized in that, The stroke volume of the first plunger pump is designed according to the leakage amount of the hydraulic oil along the gap of the piston ring (4) of the diaphragm compressor. The leakage amount of the hydraulic oil of the diaphragm compressor along the gap of the piston ring conforms to the following calculation formula: Wherein, m l is the leakage volume at the piston clearance 1 ; ρ is the density of the hydraulic oil; δ is the value of the unilateral annular clearance, with the unit of m; d is the diameter of the annular clearance; l is the clearance length; △ p l is the leakage pressure difference on both sides of the clearance in the length direction; μ is the dynamic viscosity of the hydraulic oil. The stroke volume of the first plunger pump: In the formula, is the designed stroke volume of the first plunger pump; is the design coefficient, greater than 1; is the density in the oil inlet state of the first plunger pump; the ratio of the stroke volume of the second plunger pump to the piston stroke volume of the diaphragm compressor is set to 3% - 30%.

7. A control method for the oil quantity self-balancing system of the diaphragm compressor oil described in claim 5, characterized in that, It includes the following steps: When the diaphragm compressor is in the designed working state, the proportional overflow valve on the oil replenishing circuit of the second plunger pump is in the fully open state. When the wear amount at the piston of the diaphragm compressor increases or the wear amount at the plunger gap of the first plunger pump increases, the leakage amount at the piston gap of the diaphragm compressor increases or the oil replenishing amount in the oil chamber decreases, and the hydraulic oil amount in the oil chamber of the diaphragm compressor decreases. When the diaphragm compressor is in the initial starting stage, if the measured exhaust pressure is less than the exhaust pressure under the designed working condition, the first plunger pump and the second plunger pump work together to replenish oil to the oil chamber of the diaphragm compressor at the same time.

8. The control method of the oil quantity self-balancing system of the diaphragm compressor oil as claimed in claim 7, wherein When the measured exhaust pressure is equal to the exhaust pressure under the designed working condition, the maximum oil pressure in the oil chamber of the diaphragm compressor is equal to or slightly greater than the designed oil discharge pressure, the minimum oil pressure is close to the suction pressure, and the oil discharge amount is less than or equal to the maximum oil replenishing amount of the first plunger pump under the designed working condition of the diaphragm compressor. The proportional overflow valve on the oil replenishing circuit of the second plunger pump is in the fully open state. The calculation formula for the overflow mass of the overflow valve on the oil discharge pipeline is as follows: Wherein, is the overflow mass of the overflow valve; is the overflow time of the overflow valve; is the flow coefficient; is the effective flow area corresponding to the valve opening; is the pressure difference across the valve port of the overflow valve, which is the difference between the oil discharge pressure of the diaphragm compressor and the tank pressure here; is the density of the hydraulic oil.

9. The control method of the oil quantity self-balancing system for the diaphragm compressor oil according to claim 7, characterized in that When the diaphragm compressor changes from the state in normal operation p gd = p gd ’ p omax ≥ p od ’ to p gd = p gd ’ p gd ’ < p omax < p od ’, the oil replenishment mass m os is calculated according to the flow rate measured by the oil replenishment flowmeter in the previous cycle. If the oil replenishment mass m os still equals the designed oil replenishment volume m os ’ of the first plunger pump, the hydraulic oil overflow mass m od is calculated according to the transient oil pressure measured by the pressure sensor in the previous cycle, and the leakage volume m ol = m os - m od ; the required oil replenishment volume m osn of the diaphragm compressor in this cycle is the sum of the actual leakage volume m ol of the hydraulic oil at the piston ring gap and the designed overflow oil volume m od ’; the first plunger pump and the second plunger pump work together to replenish oil to the oil chamber of the diaphragm compressor until the required oil replenishment volume is reached; the opening formula of the proportional overflow valve is as follows: In the formula, x is the opening degree of the proportional overflow valve; k is a geometric constant related to the spool structure; m os2max is the maximum oil replenishment mass of the second plunger pump; m osn is the required oil replenishment amount of the diaphragm compressor; m os1max is the maximum oil replenishment mass of the first plunger pump, calculated according to the oil replenishment and discharge pressure and the stroke volume of the plunger pump; t is the overflow time of the proportional overflow valve; C d is the flow coefficient; A is the effective flow area corresponding to the valve opening; △ p is the pressure difference across the valve port of the proportional overflow valve, which is the difference a between the oil replenishing pressure of the diaphragm compressor and the tank pressure here; ρ is the density of the hydraulic oil.

10. The control method of the oil quantity self-balancing system for the diaphragm compressor oil according to claim 7, characterized in that, When the diaphragm compressor is in the starting stage or under the condition of relatively low operating pressure, measure the exhaust pressure p gd less than the exhaust pressure under the design condition p gd ’; specifically, when 0.2 p gd ’ < p gd < p gd ’, calculate the mass of hydraulic oil overflow according to the transient oil pressure measured by the transient oil pressure sensor in the previous cycle; the mass of oil to be supplemented for the diaphragm compressor in the current cycle is equal to the sum of the overflow mass and the leakage amount at the piston clearance; if the required oil replenishment amount is less than or equal to the maximum oil replenishment amount provided by the first plunger pump, the first plunger pump replenishes oil to the oil chamber of the diaphragm compressor, and the proportional overflow valve on the oil replenishment circuit of the second plunger pump is in the fully open state; if the required oil replenishment amount is greater than the maximum oil replenishment amount provided by the first plunger pump, the first plunger pump and the second plunger pump work together to replenish oil to the oil chamber of the diaphragm compressor at the same time, and the opening formula of the proportional overflow valve is as follows: 。

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