Control method of multi-stage liquid-driven piston compressor system

Abstract

The invention discloses a control method of a multi-stage liquid-driven piston compressor system. The control method comprises the following steps: step 1, calculating geometric parameters of each stage of compressor; secondly, the pressure of the air inlet end is recognized through an acquisition card, and the pressure ratio of each stage is calculated according to the required exhaust pressure value, the compressor stage number and other parameters; thirdly, the rotating speed ratio of each stage of compressor is calculated according to the pressure ratio, the volume of each stage of cylinder and the number of cylinders; fourthly, the maximum compressor rotating speed is screened out according to the rotating speed ratio of all stages of compressors with the maximum motor power and the maximum pump station oil pressure parameter as limits; and fifthly, the reversing frequency value of a reversing mechanism is calculated according to the rotating speed of each stage of compressor, and therefore the effect of changing design working conditions is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of compressors, and more particularly to a control method for a multi-stage liquid-driven piston compressor system. Background Art

[0002] Hydrogen is a secondary energy source with a wide range of sources, clean and low-carbon, flexible and efficient, and rich application scenarios. Hydrogen energy is a key medium for China's energy structure transformation. As professional equipment for filling hydrogen fuel cells, hydrogen refueling stations currently have two filling standards of 35MPa and 70MPa according to the different hydrogen supply pressure levels. Operating in a high-pressure environment makes the components extremely easy to damage. Due to the wide explosion range of hydrogen, the compression process is required to be pollution-free, which further restricts the development of hydrogen compressors. Therefore, the development of highly reliable and pollution-free hydrogen compressors has become the key to promoting the development of the hydrogen energy industry. Liquid-driven piston compressors have the advantages of being able to start and stop with load, high volumetric efficiency, few wearing parts, and simple maintenance. They are one of the main application forms of hydrogen compressors in future hydrogen refueling stations.

[0003] As the core power component of the hydrogen refueling station, the operating efficiency of the compressor determines the operating efficiency of the entire system. The operating efficiency of the compressor mainly depends on the design conditions and operating conditions. When the operating conditions are the same as the design conditions, the unit is in an efficient operating state. Since the sources of hydrogen at the hydrogen refueling station include hydrogen production from industrial tail gas and hydrogen production from natural gas, the hydrogen pressure received by the hydrogen refueling station is not fixed, and the compressor often needs to work under non-design conditions. At this time, the compressor efficiency is low, which makes the overall efficiency of the pressurization system low, resulting in poor economic efficiency of the hydrogen refueling station.

[0004] There are two ways to adjust the working conditions, namely, adjusting the geometric structure and adjusting the control method. However, adjusting the geometric structure is costly and can easily cause safety hazards, so there is an urgent need for a corresponding control system for the liquid-driven compressor of the hydrogen refueling station. There is no mature control scheme and control system in China, which makes the hydrogen refueling station in a situation of low reliability and poor economy for a long time, which seriously hinders the layout of my country's hydrogen energy industrialization.

[0005] Due to the variety of gas transmission sources, the intake pressure is often different from the design working condition. Most of the liquid-driven piston compressors in hydrogen refueling stations operate under a certain working condition (speed) at the time of design. Liquid-driven piston compressors often operate under non-working conditions. At this time, the compressor exhaust temperature is too high, the pump station oil pressure is high, and the service life of parts is greatly reduced, resulting in low unit reliability and poor economy. It is impossible to make corresponding adjustments for different suction pressures. Summary of the invention

[0006] The object of the present invention is to provide a control method for a multi-stage liquid-driven piston compressor system, in order to solve the technical problems existing in the background technology.

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

[0008] A control method for a multi-stage liquid-driven piston compressor system, comprising:

[0009] The first step is to calculate the geometric parameters of each stage of the compressor;

[0010] The second step is to identify the pressure at the inlet end through the acquisition card, and calculate the pressure ratio of each stage according to the required exhaust pressure value and the number of compressor stages and other parameters;

[0011] The third step is to calculate the speed ratio of each compressor according to the compression ratio, cylinder volume at each level, and the number of cylinders;

[0012] The fourth step is to select the maximum compressor speed according to the speed ratio of each level of compressors, with the maximum motor power and the maximum oil pressure parameters of the pump station as the limit;

[0013] The fifth step is to calculate the commutation frequency value of the commutation mechanism according to the rotation speed of each level of compressor, so as to achieve the effect of changing the design working condition.

[0014] In some embodiments, the first step of calculating geometric parameters of each stage of the compressor includes:

[0015] V=π*d 2 *1

[0016] Where: V is the cylinder volume, d is the cylinder radius, and l is the cylinder stroke.

[0017] In some embodiments, the second step is to identify the pressure at the air inlet end through the acquisition card, and calculate the pressure ratio of each stage according to the required exhaust pressure value and the number of compressor stages and other parameters; including:

[0018]

[0019] Where: ε is the pressure ratio, p 1s is the pressure at the first stage inlet, p 2d is the pressure at the secondary exhaust end.

[0020] In some embodiments, the third step is to calculate the speed ratio of each compressor according to the compression ratio, the cylinder volume of each stage, and the number of cylinders; including:

[0021]

[0022] In the formula: n is the compression speed, V is the compressor cylinder volume, g is the number of compressor cylinders, ε is the pressure ratio, the superscript 1 represents the first stage, and the superscript 2 represents the second stage.

[0023] In some embodiments, the fourth step, taking the maximum power of the motor and the maximum oil pressure parameters of the pump station as restrictions, and screening out the maximum compressor speed according to the speed ratios of the compressors at various levels, includes:

[0024]

[0025] Where: P is the motor power, V is the compressor cylinder volume, g is the number of compressor cylinders, n is the compression speed, p is the intake pressure, k is the process index, ε is the pressure ratio, η ad is the adiabatic efficiency, ηd is the mechanical efficiency;

[0026] p omax =(p d -p s )×S+p omin

[0027] Where: p o is the oil pressure of the pump station, p s is the pressure at the inlet end, p d is the pressure at the exhaust end, and S is the end surface area of ​​the compressor cylinder.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The control method of the multi-stage liquid-driven piston compressor system designed in the present invention can change the design working condition from a specific point to a range, thereby widening the operating condition range of the liquid-driven piston compressor, allowing the unit to operate efficiently under different working conditions, thereby improving the working efficiency of the system.

[0030] (2) By adjusting the pressure ratio, the maximum oil pressure required under the same conditions is reduced, reducing the cost of the oil pump; the exhaust pressure is reduced, which increases the service life of the seals. Overall, the construction and operation costs of the unit are reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Flow chart of multi-stage liquid-driven piston compressor;

[0032] Figure 2 Control logic diagram of a multi-stage liquid-driven piston compressor. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below in conjunction with the drawings in the preferred embodiments of the present application. In the drawings, the same or similar reference numerals throughout represent the same or similar parts or parts with the same or similar functions. The described embodiments are part of the embodiments of the present application, not all of the embodiments. The embodiments described below with reference to the drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limitations on the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0034] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0035] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, or it can be an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0036] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are orientations or positional relationships based on the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0037] In addition, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, for example, a process, method, system, product, or display that includes a series of steps or elements is not necessarily limited to those steps or elements explicitly listed but may include other steps or elements not explicitly listed or inherent to such process, method, product, or display.

[0038] The following will be combined Figure 1-Figure 2 , a control method for a multi-stage liquid-driven piston compressor system involved in an embodiment of the present application is described in detail. It is worth noting that the following embodiments are only used to explain the present application and do not constitute a limitation on the present application.

[0039] Embodiment 1:

[0040] like Figure 1-2As shown, a control method for a multi-stage liquid-driven piston compressor system is used to control the multi-stage liquid-driven piston compressor system. The flow chart of the multi-stage liquid-driven piston compressor system is shown in Figure 1 As shown, it includes a motor 1, a transmission mechanism 2, a two-way oil pump 3, an oil tank 4, an oil overflow valve 5, a one-way valve 6, an oil replenishment pump 7, a first-stage compressor reversing valve 8, a second-stage compressor reversing valve 9, a pressure sensor 10, a first-stage compressor 11, a second-stage compressor 12, and an automatic control system 13.

[0041] The main shaft of the motor 1 is connected to the main shafts of the two-way oil pump 3 and the oil replenishment pump 7 through the transmission mechanism 2. The two-way oil pump 3 is responsible for the main oil supply of the oil circuit, and the oil replenishment pump 7 is responsible for preventing the hydraulic oil pressure in the oil circuit from being too low, causing the pipeline to be flattened by air. Since both have large loads and need to withstand large torsional forces, the transmission mechanism 2 is made of solid steel. When the two-way oil pump 3 is on the oil supply side, the pipeline is subjected to a higher pressure of 30Mpa. Between the two-way oil pump 3, the oil overflow valve 5, the check valve 6, the first-stage compressor reversing valve 8, and the first-stage compressor 11, a hydraulic hose resistant to ultra-high pressure is used to connect to reduce the pipeline resistance received during oil supply and reduce the pulsation of oil supply pressure. The oil replenishment pump 7 is on the return oil side, and the pressure in the pipeline is generally 2-3Mpa. Ordinary thin-walled steel pipes are used for hard connection between the oil replenishment pump 7, the oil overflow valve 5, and the check valve 6. The length of the steel pipe used is short to avoid pipeline resonance affecting the operation of the pump. The same is true for the secondary compressor.

[0042] The automatic control system 13 is connected to the pressure sensor 10 using a two-core signal line to obtain relevant pressure parameters. The automatic control system 13 is connected to the first-stage compressor reversing valve 8 and the second-stage compressor reversing valve 9 using a four-core signal line, two cores of which provide power supply and two cores of which input control signals.

[0043] The control method of the multi-stage liquid-driven piston compressor system designed in the present application uses an acquisition card to identify the signal of the pressure sensor at the air inlet, transmits the signal to the control system, uses the program in the control system to calculate the reasonable rotation speed of the first and second stage compressors, and adjusts the mechanism for controlling the pump speed to achieve pressure ratio adjustment. Thereby, the working condition of the high pressure ratio of the compressor piston is improved, the cylinder exhaust temperature is reduced, and the efficiency of the unit is improved; the maximum oil pressure of the oil cylinder is reduced, and the service life of the pump station is increased. Since the cost of the pump station is proportional to the maximum oil pressure, the reduction in oil pressure also reduces the cost of the pump station. Through this control system, the operating range of the liquid-driven piston compressor is widened, the cost of the liquid-driven compressor system is reduced, and the efficient operation of the liquid-driven compressor is achieved.

[0044] The control logic diagram of the multi-stage liquid-driven piston compressor of the present invention is as follows: Figure 2 shown.

[0045] The first step is to calculate the geometric parameters of each compressor stage (exhaust pressure p 2d, cylinder capacity V1, V2, etc.).

[0046] V=π*d 2 *1

[0047] Where: V is the cylinder volume, d is the cylinder radius, and l is the cylinder stroke.

[0048] The second step is to identify the pressure at the inlet end through the acquisition card (p 1s ), and calculate the pressure ratio (ε) of each stage according to the required exhaust pressure value and the number of compressor stages and other parameters.

[0049]

[0050] Where: ε is the pressure ratio, p 1s is the pressure at the first stage inlet, p 2d is the pressure at the secondary exhaust end.

[0051] The third step is to calculate the speed ratio of each compressor stage based on the compression ratio, cylinder volume at each stage, number of cylinders (g1, g2) and other parameters.

[0052]

[0053] In the formula: n is the compression speed, V is the compressor cylinder volume, g is the number of compressor cylinders, ε is the pressure ratio, the superscript 1 represents the first stage, and the superscript 2 represents the second stage.

[0054] The fourth step is to use the maximum power of the motor (P) and the maximum oil pressure of the pump station (p omax ) and other parameters are used as restrictions, and the maximum compressor speed is selected according to the speed ratio of each level of compressor.

[0055]

[0056] Where: P is the motor power, V is the compressor cylinder volume, g is the number of compressor cylinders, n is the compression speed, p is the intake pressure, k is the process index, ε is the pressure ratio, η ad is the adiabatic efficiency and ηd is the mechanical efficiency.

[0057] p omax =(p d -p s )×S+p omin

[0058] Where: p o is the oil pressure of the pump station, p s is the pressure at the inlet end, p d is the pressure at the exhaust end, and S is the end surface area of ​​the compressor cylinder.

[0059] The fifth step is to calculate the commutation frequency value of the commutation mechanism according to the rotation speed of each level of compressor, so as to achieve the effect of changing the design working condition.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A control method for a multi-stage liquid-driven piston compressor system, characterized in that: include: The first step is to calculate the geometric parameters of each stage of the compressor; The second step is to identify the pressure at the inlet end through the acquisition card, and calculate the pressure ratio of each stage according to the required exhaust pressure value and the number of compressor stages and other parameters; The third step is to calculate the speed ratio of each compressor according to the compression ratio, cylinder volume at each level, and the number of cylinders; The fourth step is to select the maximum compressor speed according to the speed ratio of each level of compressors, with the maximum motor power and the maximum oil pressure parameters of the pump station as the limit; The fifth step is to calculate the commutation frequency value of the commutation mechanism according to the rotation speed of each level of compressor, so as to achieve the effect of changing the design working condition.

2. The control method of a multi-stage liquid-driven piston compressor system according to claim 1, characterized in that: The first step is to calculate the geometric parameters of each stage of the compressor; including: V=π*d 2 *l Where: V is the cylinder volume, d is the cylinder radius, and l is the cylinder stroke.

3. The control method of a multi-stage liquid-driven piston compressor system according to claim 1, characterized in that: The second step is to identify the pressure at the inlet end through the acquisition card, and calculate the pressure ratio of each stage according to the required exhaust pressure value and the number of compressor stages and other parameters; include: Where: ε is the pressure ratio, p 1s is the pressure at the first stage inlet, p 2d is the pressure at the secondary exhaust end.

4. The control method of a multi-stage liquid-driven piston compressor system according to claim 1, characterized in that: The third step is to calculate the speed ratio of each compressor according to the compression ratio, the cylinder volume of each level, and the number of cylinders; including: In the formula: n is the compression speed, V is the compressor cylinder volume, g is the number of compressor cylinders, ε is the pressure ratio, the superscript 1 represents the first stage, and the superscript 2 represents the second stage.

5. The control method of a multi-stage liquid-driven piston compressor system according to claim 1, characterized in that: The fourth step is to select the maximum compressor speed according to the speed ratio of each level of compressors with the maximum motor power and the maximum oil pressure parameters of the pump station as restrictions; including: Where: P is the motor power, V is the compressor cylinder volume, g is the number of compressor cylinders, n is the compression speed, p is the intake pressure, k is the process index, ε is the pressure ratio, η ad is the adiabatic efficiency, η d for mechanical efficiency; p omax =(p d -p s )×S+p omin Where: p o is the oil pressure of the pump station, p s is the pressure at the inlet end, p d is the pressure at the exhaust end, and S is the end surface area of ​​the compressor cylinder.

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