High-precision and wide-adaptability gas flow control device and method

Abstract

The invention discloses a high-precision wide-adaptability gas flow control device and method.The device comprises at least two pressure reducing valves, a proportional valve, a flow meter, a buffer tank and a first back pressure valve which are sequentially connected, the front end of the first pressure reducing valve is communicated with a gas source, and a pressure sensor is arranged on a connecting pipeline of the gas flow control device; the gas flow control device has the advantage that high-dynamic and high-precision gas flow control is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric pile, and particularly relates to a high-precision wide-adaptive gas flow control device and method. BACKGROUND

[0002] Energy is the driving force for the development of human society, and the development of energy technology is one of the important indicators to measure the economic development level and living standard of a country. Every progress of human society is inseparable from the breakthrough and innovation of energy technology. However, the existing energy structure and unreasonable use of human beings have brought heavy damage to human society: environmental problems such as acid rain, greenhouse effect, global warming, air pollution and ozone layer destruction are forcing human beings to pay attention to the transformation of energy structure. And seeking new energy technology with high efficiency, cleanness and sustainability is also a problem that all countries in the world must face and pay attention to.

[0003] Fuel cell is an electrochemical device that can effectively control the chemical reaction of fuel and oxidant and convert the chemical energy into electric energy, and is an energy converter that converts the chemical energy in fuel into electric energy, and is known as the fourth power generation method after thermal power, hydroelectric power and nuclear power. Although fuel cell is called battery, it is actually different from battery. Battery belongs to the category of energy storage device, while fuel cell does not store energy, and is essentially only an energy converter, which is more like a generator.

[0004] Compared with the traditional power generation method, fuel cell has its special features: in the reaction process, the energy conversion process of fuel cell has no open fire combustion activity, so the energy conversion efficiency is not limited by Carnot cycle. In addition, fuel cell also has the advantages of fuel diversification, low noise, clean exhaust, small environmental pollution, good maintainability and high reliability. The test of fuel cell involves multiple aspects, including performance, durability, safety, etc. Fuel cell test system is used to test fuel cell, which includes fuel system, air system and heat management system, etc. For the use of gas, a flow controller is generally used to issue, but for large flow system, the range of flow controller is limited, so multiple flow controllers are used, which requires internal space of the bench, and greatly increases the cost.

[0005] Chinese patent publication No. CN111106366A discloses a fuel cell stack test bench and a back pressure control method thereof. The test bench includes a hydrogen system and an air system. The hydrogen system is communicated with the hydrogen inlet of the fuel cell stack through an inlet pipeline. The air system is communicated with the air inlet of the fuel cell stack through an inlet pipeline. The inlet pipeline is provided with a flow meter for detecting the flow thereof. The hydrogen outlet and the air outlet of the fuel cell stack are provided with an outlet pipeline. The outlet pipeline is provided with a first back pressure valve and a second back pressure valve in parallel. The back pressure range of the first back pressure valve is smaller than that of the second back pressure valve. The pipeline section between the inlet pipeline or / and the outlet pipeline and the first back pressure valve and the second back pressure valve is provided with a pressure sensor for detecting the pressure thereof. The back pressure control method utilizes double back pressure valves, two-way control, and different flow to quickly realize back pressure control. Higher precision control is realized, and a larger power range is covered, thereby saving the test bench cost of the customer. However, the test range of each flow controller is limited, so that large range flow test cannot be performed, that is, high dynamic gas flow control cannot be realized. The flow control is affected by various interferences such as supply pressure fluctuation and use end pressure fluctuation, so that high precision gas flow control is difficult to realize. SUMMARY

[0006] The technical problem to be solved by the present application is how to realize high dynamic and high precision gas flow control of a fuel cell test bench.

[0007] The present application solves the above technical problem by the following technical means: a high precision and wide adaptability gas flow control device, comprising at least two pressure reducing valves, a proportional valve, a flow meter, a buffer tank and a first back pressure valve connected in sequence. The front end of the first pressure reducing valve is communicated with a gas source. The connection pipeline of the gas flow control device is provided with a pressure sensor.

[0008] The present application reduces the influence of gas source pressure fluctuation by series connection of pressure reducing valves, ensures stable gas pressure entering the proportional valve, increases the volume of the whole system by the buffer tank, further improves the stability of the pressure and reduces the difficulty of pressure control. The proportional valve can realize flow control by adjusting the valve opening, thereby realizing large range flow test. The overall scheme realizes high dynamic and high precision gas flow control.

[0009] Further, the high precision and wide adaptability gas flow control device further comprises a first PID controller, and the rear end of the first back pressure valve is connected with the first PID controller.

[0010] Further, the high precision and wide adaptability gas flow control device further comprises a second back pressure valve. One end of the second back pressure valve is connected to the front end of the proportional valve, and the other end of the second back pressure valve is connected with a second PID controller.

[0011] Further, a pressure sensor is arranged on the line between the gas source and the pressure reducing valve, the line between the pressure reducing valve and the proportional valve, the line between the flow meter and the buffer tank, and the line in front of the second back pressure valve.

[0012] The application also provides a method for controlling the gas flow of a high-precision and wide-adaptive gas flow control device, comprising the following steps:

[0013] S1, fixing the back end pressure of the last pressure reducing valve;

[0014] S2, recording the pipeline flow corresponding to the different valve openings of the proportional valve under the same pressure, and fitting to obtain the curve function corresponding to the valve opening and flow of the proportional valve under the pressure; in the same way, the curve function corresponding to the valve opening and flow of the proportional valve under different pressures is obtained;

[0015] S3, collecting the coefficients of the curve functions fitted under different pressures, which reflect the valve opening of the proportional valve;

[0016] S4, fitting the coefficients and the corresponding pressures to obtain a function about the pressure and the valve opening of the proportional valve as a feedforward for valve adjustment, and adjusting the valve opening of the proportional valve.

[0017] Further, S1 comprises:

[0018] The proportional valve is connected to one end of the second back pressure valve, and the other end of the second back pressure valve is connected to the second PID controller; the second PID controller receives the deviation between the set pressure value and the real-time collected back end pressure of the pressure reducing valve, and adjusts the back end pressure of the pressure reducing valve, so that the back end pressure of the pressure reducing valve is fixed as the set pressure value.

[0019] Further, S2 comprises:

[0020] The pipeline flow corresponding to the valve opening of the proportional valve under the pressure P1 is recorded, and the curve function y=k1x corresponding to the valve opening and flow of the proportional valve under the pressure P1 is fitted, wherein x is the valve opening of the proportional valve, and y is the pipeline flow; in the same way, the curve function y=k n x corresponding to the valve opening and flow of the proportional valve under the pressure Pn is obtained, wherein Pn pressure refers to the nth pressure set value, k1 is the corresponding coefficient under the pressure P1, and k n is the corresponding coefficient under the pressure Pn, which reflects the valve opening of the proportional valve.

[0021] Further, S4 comprises:

[0022] The coefficients k1, k2, …, k n and the corresponding pressures P1, P2, …, P nA function of the pressure and the proportional valve opening degree is obtained as a feedforward of the valve adjustment, and the proportional valve opening degree is adjusted.

[0023] Further, S4 further comprises:

[0024] The system set pressure value is obtained, the proportional valve opening degree is adjusted according to the function relation of the pressure and the proportional valve opening degree, meanwhile, the second PID controller receives the deviation between the set pressure value and the real-time collected back-end pressure of the pressure reducing valve, and adjusts the back-end pressure of the pressure reducing valve, so that the back-end pressure of the pressure reducing valve is fixed as the set pressure value.

[0025] Further, the selection of the proportional valve depends on the flow capacity coefficient Cv, and the larger the flow capacity coefficient Cv is, the better the performance of the proportional valve is, so that the proportional valve with the flow capacity coefficient Cv exceeding a preset value is selected, and the calculation method of the flow capacity coefficient Cv is:

[0026] Cv=Kv*1.156

[0027] Wherein, Kv V is the flow coefficient;

[0028] When P'2>P'1 / 2,

[0029] When P'2≤P'1 / 2,

[0030] Wherein, Q N represents the standard flow, P'1 represents the inlet pressure, P'2 represents the outlet pressure, ΔP represents the pressure difference between the inlet and the outlet, and ρ N represents the standard density, and T1 represents the medium temperature.

[0031] The advantages of the present application are:

[0032] (1) When the valve opening degree is fixed, different source pressures will cause different flow rates, so when the source pressure fluctuates, the valve is difficult to instantaneously suppress the flow fluctuation, which will cause the whole system to shake, so it is necessary to reduce the fluctuation of the source pressure to increase the stability of the system, the present application reduces the influence of the fluctuation of the gas source pressure by connecting the pressure reducing valve in series, increases the volume of the system by adding a buffer tank, and the increase of the volume of the system can buffer the change of the pressure, further improve the stability of the pressure and reduce the difficulty of pressure control. The proportional valve can control the flow by adjusting the valve opening degree, and the whole scheme realizes high dynamic and high precision gas flow control.

[0033] (2) The second back pressure valve is drawn from the front end of the proportional valve and is connected to the second PID controller, which can control the pressure at the front end of the proportional valve and further reduce the pressure fluctuation. The first back pressure valve is used to control the pressure of the whole system and can provide different pressures to the system to ensure the adaptability of the proportional valve plus flowmeter control flow scheme in different environments.

[0034] (3) Different source pressures will cause different opening degrees of the proportional valve, which makes it difficult for the conventional PID direct regulation to be applicable in the whole pressure range. Therefore, the application mainly introduces a flow control method, which calculates the current required opening degree of the valve through the current front and rear end pressures and the required flow to be controlled, directly opens the proportional valve to this opening degree, and lets the PID regulate the partial flow, thereby quickly realizing large-range flow release. The valve opening degree under different pressures is fed forward and the PID is used to control the flow, thereby realizing more accurate flow control. The whole control mode environment is convenient to build, and the control mode is convenient and efficient.

[0035] (4) The application also sets a selection method for the proportional valve. Cv is an important index of the proportional valve, which measures the flow capacity of the valve. It is necessary to ensure that the Cv of the valve matches the flow requirement, avoids large pressure drop caused by too small Cv, or low control precision caused by too large Cv, and selects a more suitable proportional valve through the method, which is conducive to the stable operation of the system.

[0036] (5) Another advantage of the application is that compared with the traditional flow controller, the conventional method controls the flow rate slowly, but under the strategy of the application, for large flow control, it can achieve faster rate, simpler structure and lower cost control. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 A structure schematic view of a high-precision wide-adaptive gas flow control device disclosed by the application embodiment 1;

[0038] Figure 2 A structure schematic view of a high-precision wide-adaptive gas flow control device disclosed by the application embodiment 2;

[0039] Figure 3 A flow chart of a method of a high-precision wide-adaptive gas flow control device disclosed by the application embodiment 3;

[0040] Figure 4 A test example result schematic view of a method of a high-precision wide-adaptive gas flow control device disclosed by the application embodiment 3. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0042] Example 1

[0043] like Figure 1 As shown, embodiment 1 of the present invention provides a high-precision and wide-adaptability gas flow control device, comprising at least two pressure reducing valves 2, a proportional valve 3, a flow meter 4, a buffer tank 5 and a first back pressure valve 6 connected in sequence. The front end of the first pressure reducing valve 2 is connected to the gas source 1, and a pressure sensor 7 is provided on the connecting pipeline of the gas flow control device. Most gas sources 1 are supplied by air compressors or gas cylinders. The two pressure reducing valves 2 in series can effectively reduce the impact of pressure fluctuations of the gas source 1 and ensure the stability of the gas pressure entering the proportional valve 3. The proportional valve 3 is used in conjunction with the flow meter 4 to control the flow by controlling the opening of the high-precision proportional valve 3. The flow meter 4 is used to monitor and feedback the actual flow. The buffer tank 5 is used to increase the volume of the entire system, which can further improve the stability of the pressure and reduce the difficulty of pressure control. The first back pressure valve 6 is used to control the pressure of the entire system and can provide different pressures to the system to ensure the adaptability of the solution of proportional valve 3 plus flow meter 4 to control the flow in different environments.

[0044] The high-precision and wide-adaptability gas flow control device further includes a first PID controller (not shown), and the rear end of the first back-pressure valve 6 is connected to the first PID controller.

[0045] The line between the gas source 1 and the pressure reducing valve 2, the line between the pressure reducing valve 2 and the proportional valve 3, and the line between the flow meter 4 and the buffer tank 5 are all provided with a pressure sensor 7. The pressure sensor 7 is used to monitor the pressure in the pipeline at the installation point.

[0046] In this embodiment, two pressure reducing valves 2 are used. Regarding the operating principle of the two-stage pressure reducing valve 2: The supply pressure effect (SPE) of the pressure reducing valve 2 is usually provided by the manufacturer. The SPE is usually expressed as a ratio or percentage, which is used to describe the change in outlet pressure caused by a change in inlet pressure. For example, if a certain pressure reducing valve 2 states that the SPE is 1:100 or 1%, the outlet pressure will increase by 1 psi for every 100 psi drop in inlet pressure. The degree of change in the outlet pressure of the pressure reducing valve 2 can be estimated using the following formula:

[0047] ΔP(outlet) = ΔP(inlet) × SPE

[0048] The outlet pressure variation of the two-stage pressure regulating valve configuration can be calculated by multiplying the inlet pressure difference by the SPE of each pressure regulating valve. The following equation illustrates the calculation method:

[0049] ΔP(outlet) = ΔP(inlet) x SPE1 x SPE2

[0050] That is, the outlet pressure fluctuation of the two-stage pressure reducing valve 2 is much smaller than the inlet pressure fluctuation, and the two-stage pressure reducing effectively filters the inlet pressure fluctuation.

[0051] Through the above technical solutions, the application reduces the influence of the pressure fluctuation of the gas source 1 through the series connection of the pressure reducing valve 2, ensures the stability of the gas pressure of the proportional valve 3, increases the volume of the buffer tank 5, further improves the stability of the pressure and reduces the difficulty of pressure control. The proportional valve 3 can control the flow by adjusting the valve opening, thereby realizing large-range flow testing, and the overall scheme realizes high-dynamic and high-precision gas flow control.

[0052] Embodiment 2

[0053] As shown in Figure 2 , the embodiment 2 of the application is adjusted on the basis of the embodiment 1, and the difference between the embodiment 2 and the embodiment 1 is that:

[0054] The high-precision wide-adaptive gas flow control device further comprises a second back pressure valve 8, one end of the second back pressure valve 8 is connected to the front end of the proportional valve 3, and the other end of the second back pressure valve 8 is connected with the second PID controller. A pressure sensor 7 is arranged on the line in front of the second back pressure valve 8. The second back pressure valve 8 is led out from the front end of the proportional valve 3 and connected with the second PID controller (not shown in the figure), which can control the pressure in front of the proportional valve 3 and further reduce the pressure fluctuation.

[0055] Embodiment 3

[0056] Based on the embodiment 2, the stable gas after the two-stage pressure reducing valve 2 passes through the proportional valve 3 and the flowmeter 4, the different flow is realized by controlling the opening of the proportional valve 3, the first back pressure valve 6 at the rear end can be used to control different pressures, and the front-end pressure reducing valve 2 can control different inlet pressures by adjusting the knob. Therefore, the conventional PID parameters are difficult to adapt to the fast and stable control of the flow under different front and rear pressures, and thus the flow can be controlled by the valve opening feedforward under different pressures plus PID, so that the embodiment 3 of the application provides a high-precision wide-adaptive gas flow control device, as shown in Figure 3 , comprising the following steps:

[0057] S1, fixing the rear-end pressure of the last pressure reducing valve 2; the specific process is as follows:

[0058] The front end of the proportional valve 3 is connected to one end of the second back pressure valve 8, and the other end of the second back pressure valve 8 is connected to the second PID controller; the second PID controller receives the deviation between the set pressure value and the rear end pressure of the pressure reducing valve 2 collected in real time, and adjusts the rear end pressure of the pressure reducing valve 2 so that the rear end pressure of the pressure reducing valve 2 is fixed to the set pressure value.

[0059] S2. Record the pipeline flow corresponding to different valve openings of the proportional valve 3 under the same pressure, and obtain the curve function corresponding to the valve opening and flow of the proportional valve 3 under the pressure by fitting. In the same way, obtain the curve function corresponding to the valve opening and flow of the proportional valve 3 under different pressures. The specific process is as follows:

[0060] Record the pipeline flow rate corresponding to the valve opening of the proportional valve 3 under pressure P1, and fit the curve function y=k1x corresponding to the valve opening and flow rate of the proportional valve 3 under pressure P1, where x is the valve opening of the proportional valve 3 and y is the pipeline flow rate; in the same way, obtain the curve function y=k1x corresponding to the valve opening and flow rate of the proportional valve 3 under pressure Pn n x, where Pn pressure refers to the nth pressure setting value, k1 is the coefficient corresponding to pressure P1, k n It is the coefficient corresponding to the pressure Pn, which reflects the valve opening of the proportional valve 3.

[0061] S3, collecting coefficients of the curve function obtained by fitting under different pressures, where the coefficients reflect the valve opening of the proportional valve 3;

[0062] S4. The fitting coefficient and the corresponding pressure are used to obtain a function of pressure and valve opening of proportional valve 3, which is used as the feedforward of valve regulation to adjust the valve opening of proportional valve 3. The specific process is as follows:

[0063] Fitting coefficients k1, k2, ..., k n and the corresponding pressures P1, P2, ..., P n A function of pressure and valve opening of proportional valve 3 is obtained and used as feedforward for valve regulation to adjust the valve opening of proportional valve 3.

[0064] S5. Obtain the pressure value set by the system, and adjust the valve opening of the proportional valve 3 according to the functional relationship between the pressure and the valve opening of the proportional valve 3. At the same time, the second PID controller receives the deviation between the set pressure value and the rear end pressure of the pressure reducing valve 2 collected in real time, and adjusts the rear end pressure of the pressure reducing valve 2 so that the rear end pressure of the pressure reducing valve 2 is fixed to the set pressure value.

[0065] As a further improved technical solution, the selection of the proportional valve 3 depends on its flow capacity coefficient Cv, the larger the flow capacity coefficient Cv, the better the performance of the proportional valve 3, so the proportional valve 3 with the flow capacity coefficient Cv exceeding the preset value is selected, and the calculation method of the flow capacity coefficient Cv is:

[0066] Cv=Kv*1.156

[0067] Wherein, K V is the flow coefficient (unit m 3 / h);

[0068] When P'2>P'1 / 2,

[0069] When P'2≤P'1 / 2,

[0070] Wherein, Q N represents the standard flow (unit mN 3 / h), P'1 represents the inlet pressure (unit bar), P'2 represents the outlet pressure (unit bar), ΔP represents the pressure difference between inlet and outlet (unit bar), ρ N represents the standard density (unit kg / m 3 ), T1 represents the medium temperature (T1=273+t) unit K. T1 represents the thermodynamic temperature, and t represents the Celsius degree

[0071] As Figure 4 shown, a test example is given, under which the feedforward plus PID closed-loop control flow is 500NLPM-3500NLPM-500NLPM, and it can be seen that the overall flow fluctuation is very small, and the gas flow fluctuation is ±10NLPM.

[0072] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A high-precision and wide-adaptability gas flow control device, characterized in that: It includes at least two pressure reducing valves, a proportional valve, a flow meter, a buffer tank and a first back pressure valve connected in sequence. The front end of the first pressure reducing valve is connected to the gas source, and a pressure sensor is provided on the connecting pipeline of the gas flow control device.

2. A high-precision and wide-adaptability gas flow control device according to claim 1, characterized in that: It also includes a first PID controller, and the rear end of the first back pressure valve is connected to the first PID controller.

3. A high-precision and wide-adaptability gas flow control device according to claim 1, characterized in that: It also includes a second back-pressure valve, one end of which is connected to the front end of the proportional valve, and the other end of the second back-pressure valve is connected to the second PID controller.

4. A high-precision and wide-adaptability gas flow control device according to claim 3, characterized in that: Pressure sensors are provided on the line between the gas source and the pressure reducing valve, the line between the pressure reducing valve and the proportional valve, the line between the flow meter and the buffer tank, and the line at the front end of the second back pressure valve.

5. A method for applying a high-precision and wide-adaptability gas flow control device according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, fix the rear end pressure of the last pressure reducing valve; S2. Record the pipeline flow corresponding to different valve openings of the proportional valve at the same pressure, and obtain a curve function corresponding to the valve opening and flow of the proportional valve at the pressure by fitting; obtain the curve function corresponding to the valve opening and flow of the proportional valve at different pressures in the same way; S3. Collect coefficients of the curve function obtained by fitting under different pressures, where the coefficients reflect the valve opening of the proportional valve; S4. The fitting coefficient and the corresponding pressure are used to obtain a function of pressure and the valve opening of the proportional valve, which is used as a feedforward for valve regulation to adjust the valve opening of the proportional valve.

6. The method of a high-precision and wide-adaptability gas flow control device according to claim 5, characterized in that: S1 includes: The front end of the proportional valve is connected to one end of the second back pressure valve, and the other end of the second back pressure valve is connected to the second PID controller; the second PID controller receives the deviation between the set pressure value and the rear end pressure of the pressure reducing valve collected in real time, and adjusts the rear end pressure of the pressure reducing valve so that the rear end pressure of the pressure reducing valve is fixed to the set pressure value.

7. The method of a high-precision and wide-adaptability gas flow control device according to claim 5, characterized in that S2 include: Record the pipeline flow rate corresponding to the valve opening of the proportional valve under pressure P1, and fit the curve function y=k1x corresponding to the valve opening and flow rate under pressure P1, where x is the valve opening of the proportional valve and y is the pipeline flow rate; in the same way, obtain the curve function y=k1x corresponding to the valve opening and flow rate under pressure Pn n x, where Pn pressure refers to the nth pressure setting value, k1 is the coefficient corresponding to pressure P1, k n It is the coefficient corresponding to the pressure Pn, which reflects the valve opening of the proportional valve.

8. The method of a high-precision and wide-adaptability gas flow control device according to claim 7, characterized in that S4 include: Fitting coefficients k1, k2, ..., k n and the corresponding pressures P1, P2, ..., P n A function of pressure and proportional valve opening is obtained and used as feedforward for valve regulation to adjust the valve opening of the proportional valve.

9. The method of a high-precision and wide-adaptability gas flow control device according to claim 6, characterized in that: S4 and later also include: The pressure value set by the system is obtained, and the valve opening of the proportional valve is adjusted according to the functional relationship between the pressure and the valve opening of the proportional valve. At the same time, the second PID controller receives the deviation between the set pressure value and the rear end pressure of the pressure reducing valve collected in real time, and adjusts the rear end pressure of the pressure reducing valve so that the rear end pressure of the pressure reducing valve is fixed to the set pressure value.

10. The method of a high-precision and wide-adaptability gas flow control device according to claim 5, characterized in that: The selection of the proportional valve depends on its flow capacity coefficient Cv. The larger the flow capacity coefficient Cv, the better the performance of the proportional valve. Therefore, a proportional valve with a flow capacity coefficient Cv exceeding a preset value is selected. The flow capacity coefficient Cv is calculated as follows: Cv=Kv*1.156 Among them, K V is the flow coefficient; When P2'>P1' / 2, When P2'≤P1' / 2, Among them, Q N represents the standard flow rate, P1' represents the inlet pressure, P2' represents the outlet pressure, ΔP represents the inlet and outlet pressure difference, ρ N Indicates standard density, and T1 indicates medium temperature.

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