Gas-water separation water hammer buffer transient calculation method based on engineering thermodynamics

Abstract

The invention discloses a transient calculation method for a gas-water separation water hammer buffer based on engineering thermodynamics, belongs to the technical field of hydraulic transient calculation, and can solve the problem that an existing method cannot reflect transient hydraulic characteristics of the gas-water separation water hammer buffer. The method comprises the following steps: S1, constructing a first relational expression between the pressure of mixed gas and the volume flow rate of water flowing into a tank, and a second relational expression between the pressure of the mixed gas, the volume flow rate of the water flowing into the tank and the temperature of the mixed gas; s2, constructing a third relational expression of the mixed gas temperature, the mixed gas volume and the mixed gas pressure, and a fourth relational expression of the volume flow of the water body flowing into the tank and the mixed gas volume; s3, combining the relational expressions to form an equation set, and constructing a function expression of the volume flow rate of the water body flowing into the tank, the temperature of the mixed gas and the total energy of the mixed gas; and S4, according to the equation set, solving the function expression to obtain a calculated value of the volume flow of the water body flowing into the tank. The method is used for hydraulic transient calculation.

Description

Technical Field

[0001] This invention relates to a transient calculation method for a gas-water separation water hammer buffer based on engineering thermodynamics, belonging to the field of hydraulic transient calculation technology. Background Technology

[0002] With the rapid development of large-capacity, long-distance, high-pressure, and complex hydraulic systems such as pumping stations, hydropower stations, and irrigation systems, significant hydraulic transient problems inevitably arise during operation, such as power outages and large load changes. The resulting drastic fluctuations in pipeline pressure can lead to substantial engineering hazards, including noise generation, pipeline fatigue failure, and leakage of hydraulic components. In severe cases, pipe bursts, turbine runaway, or even backflow and reverse rotation may occur. To reduce water hammer accidents, current engineering practices primarily involve installing various water hammer protection measures in the system, such as water hammer relief valves, surge tanks, pressure regulating wells, air valves, and various combinations of protection. Among these, pressure regulating tanks are a commonly used and effective pressure stabilizing device that can significantly reduce water hammer, especially suitable for high-lift, long-distance hydraulic systems. However, due to the contact between gas and water phases, the gas can easily dissolve in the water. After the water and gas mix, they come into long-term contact with the inner wall of the pressure regulating tank, pipes, valves and other metal parts, which can easily corrode the inner wall and shorten the service life of the equipment. At the same time, the initial pressure of the gas must be set according to the pressure under steady-state conditions of the hydraulic system, and the initial gas pressure cannot be increased alone, which limits its widespread use in hydraulic systems.

[0003] Therefore, a novel gas-water separation pressure regulating buffer device has emerged in the prior art, which can effectively improve the aforementioned problems existing in conventional pressure regulating tanks. For example... Figure 1 As shown, this air-water separation water hammer buffer consists of an upper high-pressure air tank, a lower air-water mixing tank, multiple connecting pipes, and solenoid valves. During normal operation of the hydraulic system, the solenoid valves are closed. When system conditions change, causing hydraulic transients, during pressure reduction, if the pressure drop at a point on the main pipeline relative to the head of the pressure gauge at the main pipeline connection exceeds a set value, or if the delay time relative to the moment the main pipeline valve begins to close exceeds a set value, the solenoid valve opens and remains open. At this time, the gas in the high-pressure air tank and the gas in the air-water mixing tank flow together. The high-pressure gas in the high-pressure air tank is pushed to the upper part of the air-water mixing tank connected to the main pipeline, thereby injecting water from the air-water mixing tank into the main pipeline. Ultimately, this achieves reliable real-time water replenishment to the main pipeline from the air-water mixing tank and storage of high-pressure water in the working pipeline, thus preventing water hammer damage.

[0004] As a new type of water hammer protection measure, there is no suitable calculation model for the gas-water separation water hammer buffer in the water transient process. If the test method is used, not only there is a certain risk and huge cost, but also for large and complex pipe network, due to the influence of other elements in the test process, the transient hydraulic characteristics of the element may not be truly reflected. And due to the gas-water separation water hammer buffer in the water transient process, it is also difficult to use numerical simulation method for numerical calculation. SUMMARY

[0005] The application provides a gas-water separation water hammer buffer transient calculation method based on engineering thermodynamics, which can solve the problem that the existing method cannot truly reflect the transient hydraulic characteristics of the gas-water separation water hammer buffer.

[0006] The application provides a gas-water separation water hammer buffer transient calculation method based on engineering thermodynamics, which comprises the following steps:

[0007] S1, a first relationship between the mixed gas pressure after gas mixing in the high-pressure gas tank and the gas-water mixing tank of the gas-water separation water hammer buffer and the water body volume flow into the tank is constructed, and a second relationship between the mixed gas pressure, the water body volume flow into the tank and the mixed gas temperature is constructed;

[0008] S2, a third relationship between the mixed gas temperature, the mixed gas volume and the mixed gas pressure is constructed, and a fourth relationship between the water body volume flow into the tank and the mixed gas volume is constructed;

[0009] S3, the first relationship, the second relationship, the third relationship and the fourth relationship are combined to form an equation group, and a function expression between the water body volume flow into the tank, the mixed gas temperature and the total energy of the mixed gas is constructed;

[0010] S4, according to the equation group, and using Newton iteration method to solve the function expression, the calculation value of the water body volume flow into the tank is obtained.

[0011] Optionally, the first relationship between the mixed gas pressure after gas mixing in the high-pressure gas tank and the gas-water mixing tank of the gas-water separation water hammer buffer and the water body volume flow into the tank in S1 comprises the following steps:

[0012] According to the first law of thermodynamics, a fifth relationship between the internal energy difference of the mixed gas after gas mixing in the high-pressure gas tank and the gas-water mixing tank of the gas-water separation water hammer buffer and the work done by the mixed gas to the outside is constructed;

[0013] constructing a sixth relationship between the mixed gas pressure, the volume flow rate of the water flowing into the tank and the work done by the mixed gas to the outside, and constructing a seventh relationship between the mixed gas pressure, the volume flow rate of the water flowing into the tank and the internal energy difference of the mixed gas;

[0014] determining a first relationship between the mixed gas pressure and the volume flow rate of the water flowing into the tank according to the fifth relationship, the sixth relationship and the seventh relationship.

[0015] Optionally, the S1 comprises constructing a second relationship between the mixed gas pressure, the volume flow rate of the water flowing into the tank and the temperature of the mixed gas, specifically comprising:

[0016] constructing an eighth relationship between the temperature of the mixed gas and the work done by the mixed gas to the outside;

[0017] determining a second relationship between the mixed gas pressure, the volume flow rate of the water flowing into the tank and the temperature of the mixed gas according to the sixth relationship and the eighth relationship.

[0018] Optionally, the S4 specifically comprises:

[0019] S41, obtaining a flow difference between the volume flow rate of the water flowing into the tank in the current iteration and the volume flow rate of the water flowing into the tank in the previous iteration according to the equation set and using the Newton iteration method to solve the function expression;

[0020] S42, calculating a relative error between the iterations according to the flow difference;

[0021] S43, determining whether the relative error between the iterations is less than or equal to an error threshold, if yes, stopping the iteration to obtain a calculated value of the volume flow rate of the water flowing into the tank, if not, repeating S41 to S43.

[0022] Optionally, the S42 specifically comprises:

[0023] calculating a ratio of the flow difference to the volume flow rate of the water flowing into the tank in the current iteration, and taking an absolute value of the ratio as the relative error between the iterations.

[0024] Optionally, after the S4, the method further comprises:

[0025] determining a calculated value of the volume increment of the mixed gas according to the calculated value of the volume flow rate of the water flowing into the tank.

[0026] Optionally, after the S4, the method further comprises:

[0027] Substitute the calculated value of the water volume flow rate into the equation set to obtain the calculated value of the mixed gas pressure, the calculated value of the mixed gas temperature, and the calculated value of the mixed gas volume.

[0028] Optionally, before the S1, the method further comprises:

[0029] Optionally, before the S1, the method further comprises:

[0030] Optionally, the high-pressure gas tank and the gas-water mixing tank are both adiabatic containers.

[0031] The beneficial effects that can be produced by the present application include:

[0032] The gas-water separation water hammer buffer transient calculation method based on engineering thermodynamics provided by the present application can accurately calculate the transient parameter calculation value of the water separation water hammer buffer by constructing an equation set of the four parameters of the mixed gas pressure, the water volume flow rate into the tank, the mixed gas temperature, and the mixed gas volume after the gas in the high-pressure gas tank and the gas-water mixing tank of the gas-water separation water hammer buffer is mixed, then constructing a functional expression of the water volume flow rate into the tank, the mixed gas temperature, and the total energy of the mixed gas, combining the equation set, and using the Newton iteration method to solve the functional expression. Further, the calculated value of the water volume flow rate into the tank is substituted into the equation set to obtain the calculated value of the mixed gas pressure, the calculated value of the mixed gas temperature, and the calculated value of the mixed gas volume. These transient parameters can truly reflect the transient hydraulic characteristics of the gas-water separation water hammer buffer. The calculation process of the method is simple, and the cost is relatively low. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 A gas-water separation water hammer buffer structure diagram provided by the prior art;

[0034] Figure 2 A gas-water separation water hammer buffer transient calculation method flowchart provided by the embodiment of the present application;

[0035] Figure 3 A gas-water separation water hammer buffer hydraulic system diagram provided by the embodiment of the present application;

[0036] Figure 4 A schematic diagram of the gas flow rate in the gas-water separation water hammer buffer during the pump power-off valve closing process provided by the embodiment of the present application;

[0037] Figure 5 A schematic diagram of the gas volume in the gas-water separation water hammer buffer during the pump power-off valve closing process provided by the embodiment of the present application;

[0038] Figure 6 A schematic diagram of the gas pressure in the air-water separation water hammer buffer changing with time during the pump power-off valve closing process is provided for the embodiment of the present application;

[0039] Figure 7 A schematic diagram of the 1-fork point pressure changing with time during the pump power-off valve closing process is provided for the embodiment of the present application;

[0040] Figure 8 A schematic diagram of the pump rotating speed changing with time during the pump power-off valve closing process is provided for the embodiment of the present application;

[0041] Figure 9 A schematic diagram of the hydraulic system envelope during the pump power-off valve closing process is provided for the embodiment of the present application.

[0042] Reference signs:

[0043] 10, air-water separation water hammer buffer; 11, high-pressure gas tank; 12, air-water mixed tank; 13, electromagnetic valve. DETAILED DESCRIPTION

[0044] The present application will be described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0045] The embodiment of the present application provides a transient calculation method of an air-water separation water hammer buffer based on engineering thermodynamics, as shown in Figure 2 and Figure 3 The method comprises the following steps.

[0046] S1, a first relationship between the mixed gas pressure after the gas mixing of the high-pressure gas tank 11 and the air-water mixed tank 12 in the air-water separation water hammer buffer 10 and the water body volume flow into the tank is constructed, and a second relationship between the mixed gas pressure, the water body volume flow into the tank and the mixed gas temperature is constructed.

[0047] The first relationship between the mixed gas pressure after the gas mixing of the high-pressure gas tank 11 and the air-water mixed tank 12 in the air-water separation water hammer buffer 10 and the water body volume flow into the tank is constructed, and the second relationship between the mixed gas pressure, the water body volume flow into the tank and the mixed gas temperature is constructed, specifically comprising:

[0048] (1) according to the first law of thermodynamics, a fifth relationship between the internal energy difference of the mixed gas after the gas mixing of the high-pressure gas tank 11 and the air-water mixed tank 12 in the air-water separation water hammer buffer 10 and the work done by the mixed gas to the outside is constructed.

[0049] According to the first law of thermodynamics, the energy equation of the gas mixing process and the water body interaction is established, as shown below:

[0050] ;

[0051] wherein, The heat absorbed by the gas from the outside world, since the gas boundary is adiabatic, so ; The total energy difference of the mixed gas, ignoring the kinetic energy and potential energy of the gas in the research object, so The internal energy difference of the mixed gas , that is ; The specific enthalpy of the mixed gas flowing out; The mass of the mixed gas flowing out, The specific enthalpy of the mixed gas flowing in; The mass of the mixed gas flowing in; The velocity of the mixed gas flowing out; The velocity of the mixed gas flowing in; The work done by the mixed gas to the outside world.

[0052] In the present application, for the whole air-water separation water hammer buffer 10, since there is no gas flowing in and out, the above-mentioned mixed gas flowing out mass , mixed gas flowing in mass , mixed gas flowing out velocity , mixed gas flowing in velocity are all 0.

[0053] Further, the fifth relationship between the internal energy difference of the mixed gas and the work done by the mixed gas to the outside world is obtained, as follows: .

[0054] (2) The sixth relationship between the mixed gas pressure, the volume flow rate of the water flowing into the tank, and the work done by the mixed gas to the outside world is constructed, and the seventh relationship between the mixed gas pressure, the volume flow rate of the water flowing into the tank, and the internal energy difference of the mixed gas is constructed.

[0055] The work done by the mixed gas to the outside world is generally obtained as follows:

[0056] ;

[0057] Wherein, is the mixed gas pressure; is the expansion / compression volume of the mixed gas.

[0058] According to the above formula, the work done by the mixed gas to the outside world in time is calculated, and the mixed gas pressure , the volume flow rate of the water flowing into the tank , and the work done by the mixed gas to the outside world The sixth relation between them is as follows:

[0059] ;

[0060] in, The volumetric flow rate of the water entering the tank; The initial pressure of the gas inside the gas-water mixing tank 12.

[0061] Mixed gas pressure Flow rate of water into the tank Energy difference with the mixed gas The seventh relation between them is as follows:

[0062] ;

[0063] in, The initial specific thermodynamic energy of the gas mixture; The volumetric flow rate of water entering the air-water mixing tank 12 at the previous moment.

[0064] The initial specific thermodynamic energy of the above-mentioned mixed gas The following formula is used to derive:

[0065] ,

[0066] in, The initial specific thermodynamic energy of the gas inside the gas-water mixing tank 12. The initial specific thermodynamic energy of the gas inside the high-pressure gas tank 11. The initial gas mass in the gas-water mixing tank 12, The initial gas mass in the high-pressure gas tank 11.

[0067] (3) Determine the first relationship between the pressure of the mixed gas and the volumetric flow rate of the water flowing into the tank based on the fifth, sixth and seventh relationships.

[0068] Mixed gas pressure Volumetric flow rate of water flowing into the tank The first relation between them is shown below:

[0069] .

[0070] The aforementioned second relationship between the mixed gas pressure, the volumetric flow rate of water entering the tank, and the mixed gas temperature specifically includes:

[0071] (1) Constructing the temperature of the mixed gas Work done by the gas mixture on the outside The eighth relation between them.

[0072] The eighth relationship is shown as follows:

[0073] ;

[0074] wherein, is the specific heat capacity of the mixed gas at constant volume, is the mass of the mixed gas.

[0075] (2) The second relationship between the mixed gas pressure , the water volume flow rate flowing into the tank and the mixed gas temperature is determined according to the sixth relationship and the eighth relationship.

[0076] The second relationship is shown as follows:

[0077] .

[0078] S2, a third relationship between the mixed gas temperature, the mixed gas volume and the mixed gas pressure is constructed, and a fourth relationship between the water volume flow rate flowing into the tank and the mixed gas volume is constructed.

[0079] The third relationship between the mixed gas temperature , the mixed gas volume and the mixed gas pressure is shown as follows:

[0080] ;

[0081] wherein, is the mixed gas volume; is the mixed gas temperature; is the gas volume constant.

[0082] The mass of the mixed gas after the adiabatic air charging is obtained according to the following equation:

[0083] .

[0084] The fourth relationship between the water volume flow rate flowing into the tank and the mixed gas volume is shown as follows:

[0085] ;

[0086] wherein, is the gas volume in the high-pressure gas tank 11 at the initial moment; is the gas volume in the gas-water mixing tank 12 at the initial moment.

[0087] S3, the first relationship, the second relationship, the third relationship and the fourth relationship form a set of equations, and a function expression between the water volume flow into the tank, the mixed gas temperature and the total energy of the mixed gas is constructed.

[0088] The function expression between the water volume flow into the tank , the mixed gas temperature and the total energy of the mixed gas is as follows:

[0089] .

[0090] S4, according to the set of equations, and using Newton iteration method to solve the function expression, the calculation value of the water volume flow into the tank is obtained.

[0091] Specifically, it includes:

[0092] S41, according to the set of equations, and using Newton iteration method to solve the function expression, the flow difference between the water volume flow into the tank in the current iteration and the water volume flow into the tank in the previous iteration is obtained.

[0093] The flow difference is obtained by using Newton-Raphson method (i.e. Newton iteration method).

[0094] The flow difference is obtained by the following formula:

[0095] ;

[0096] Wherein, is the internal energy of the gas in the tank after the initial high-pressure gas tank 11 and the gas-water mixing tank 12 are adiabatically mixed.

[0097] S42, the relative error between the iterations is calculated according to the flow difference.

[0098] Specifically, the ratio of the flow difference to the water volume flow into the tank in the current iteration is calculated, and the absolute value of the ratio is taken as the relative error between the iterations.

[0099] S43, it is judged whether the relative error between the iterations is less than or equal to the error threshold value, if yes, the iteration is stopped, and the calculation value of the water volume flow into the tank is obtained, if not, S41 to S43 are repeatedly executed.

[0100] According to the relative error between the iterations , it is judged whether the iteration in this time step is ended. If , it returns to S41; otherwise, the iteration is ended.

[0101] Wherein, is a preset error threshold value.

[0102] Furthermore, prior to S1, the method further includes:

[0103] Determine whether the solenoid valve 13 between the high-pressure gas tank 11 and the gas-water mixing tank 12 in the gas-water separation water hammer buffer 10 is open. If it is open, execute S1.

[0104] Both the high-pressure gas tank 11 and the gas-water mixing tank 12 are insulated containers.

[0105] First, set the opening parameters for solenoid valve 13.

[0106] Specifically, when a hydraulic system experiences a hydraulic transient pressure drop, if the pressure at a certain point on the main pipeline decreases relative to the piezometer head at the main pipeline connection... Greater than the set value Or the delay time relative to the moment when the main pipeline valve begins to close. Greater than the set value If so, solenoid valve 13 opens and remains open. Introducing state parameters. This is used to characterize the switching state of solenoid valve 13. The switching state parameters of solenoid valve 13... Determine using the following method:

[0107] If the gas-water separation water hammer buffer 10 is in working condition, then Otherwise, let This indicates that solenoid valve 13 is closed.

[0108] Then, determine whether solenoid valve 13 is open.

[0109] Specifically, determine the parameters Is it true? If so... If true, that is This indicates that the solenoid valve 13 between the high-pressure gas tank 11 and the gas-water mixing tank 12 is open, and the gases from the two tanks mix instantly, forming a single unit. If It is false, that is This indicates that the gas-water mixing tank 12 is used as a regular pressure regulating tank.

[0110] Multiple electromagnetic control valves are used to connect the high-pressure gas tank 11 and the gas-water mixing tank 12 to ensure that once opened, it remains open, so that the high-pressure gas tank 11 and the gas-water mixing tank 12 can be regarded as a whole tank, that is, completely connected, and the gases in the two tanks are instantly and completely mixed.

[0111] Furthermore, after S4, the method further includes:

[0112] Based on the volumetric flow rate of the water flowing into the tank The calculated value determines the volume increment of the mixed gas. The calculated value of the mixed gas volume increment is calculated according to the following formula:

[0113] ;

[0114] Wherein, is the mixed gas volume increment.

[0115] Further, after S4, the method further comprises:

[0116] The calculated value of the mixed gas pressure, the calculated value of the mixed gas temperature and the calculated value of the mixed gas volume are obtained by substituting the calculated value of the water volume flow into the equation group.

[0117] Specifically, the calculated value of the mixed gas pressure is obtained by substituting the calculated value of the water volume flow into the first relationship formula; the calculated value of the mixed gas volume is obtained by substituting the calculated value of the water volume flow into the fourth relationship formula; and the calculated value of the mixed gas temperature is obtained by substituting the calculated value of the mixed gas pressure and the calculated value of the mixed gas volume into the third relationship formula.

[0118] In actual application, the calculation process can be divided into two kinds according to whether the electromagnetic valve 13 between the high-pressure gas tank 11 and the gas-water mixing tank 12 is opened: if the electromagnetic valve 13 is not opened, only the gas-water mixing tank 12 works (used as a conventional pressure regulating tank), and the same calculation method as the conventional pressure regulating tank is adopted; if the electromagnetic valve 13 is opened, the calculation method in the present application is adopted.

[0119] The calculation method of the present application makes the following assumptions: the high-pressure gas tank 11 and the gas-water mixing tank 12 are rigid containers, and the influence of the macroscopic speed and the position height of the gas in the high-pressure gas tank 11 and the gas-water mixing tank 12 is ignored.

[0120] The ideal gas in the tank is air.

[0121] A plurality of electromagnetic control valves are used to connect the high-pressure gas tank 11 and the gas-water mixing tank 12, so as to ensure that once opened, it remains in the opened state, and the high-pressure gas tank 11 and the gas-water mixing tank 12 can be approximately regarded as a whole container, i.e. completely connected, at this time the gas in the two tanks is instantaneously completely mixed;

[0122] The high-pressure gas tank 11 and the gas-water mixing tank 12 can be assumed to be adiabatic containers, or the heat transfer through the tank wall can be calculated according to the actual situation.

[0123] Another embodiment of the present application provides a gas-water separation water hammer buffer hydraulic system, as shown by the upstream and downstream reservoirs, pipelines, water pumps, valves, and two sets of gas-water separation water hammer buffers 10. To reduce the pressure drop amplitude after the valve in the event of an accident, two gas-water separation water hammer buffers 10 are respectively arranged at the 1-fork point and the 5-fork point. Among them, the liquid surface elevations of the upstream and downstream reservoirs are 16 m and 25.5 m respectively, the total length of the pipeline is 40000 m, the rated head of the water pump is 53 m, and the rated speed is 1480 r / min. When the pump is powered off, the two-stage valve after the pump is a butterfly valve, and the closing law is 3 s fast closing 85% stroke, the remaining 15% stroke is closed in 10 s, the total valve closing time is 13 s, and the pressure of the main nodes of the hydraulic system, and the variation law of the gas pressure, flow rate, temperature and volume in the gas-water separation water hammer buffer 10 are calculated according to the method provided by the present application.

[0124] In this embodiment, the volume of the high-pressure gas tank 11 in the gas-water separation water hammer buffer 10 at the 1-fork point is 8m 3 , the initial pressure is 60.3 mH2O, the volume of the gas-water mixing tank 12 is 23m 3 , and the gas volume is 0.5m 3 . The volume of the high-pressure gas tank 11 in the gas-water separation water hammer buffer 10 at the 5-fork point is 10m 3 , the initial pressure is 32.6 mH2O, the volume of the gas-water mixing tank 12 is 19m 3 , and the gas volume is 1m 3 .

[0125] The related results of the transient hydraulic characteristics of the gas-water separation water hammer buffer 10 during the valve closing process when the pump is powered off are shown in Figures 4 to 9 , which are the gas flow rate in the gas-water separation water hammer buffer 10 versus time, the gas volume and pressure in the gas-water separation water hammer buffer 10 versus time, the pressure at the 1-fork point versus time, the pump speed versus time, and the hydraulic system envelope diagram during the valve closing process when the pump is powered off, wherein, Figure 9 the blue line in represents the maximum pressure head envelope, the green line represents the minimum pressure head envelope, the gray line represents the liquid level envelope, and the red line represents the hydraulic slope envelope.

[0126] The final calculation results of the calculation method provided by the present application show that cavitation does not occur in the entire hydraulic system. The pressure at the 5-fork point is the lowest, which is still higher than the elevation of about 1m. The minimum residual water in the gas-water separation water hammer buffer 10 at the 1-fork point is 1m 3 , and the minimum residual water in the gas-water separation water hammer buffer 10 at the 5-fork point is 1m 3Compared with the traditional pressure regulating tank, the air-water separation water hammer buffer 10 can greatly save the total volume of the tank. When the air-water separation water hammer buffer 10 is used for water hammer protection, the volume of the air-water separation water hammer buffer 10 can be effectively reduced by reasonably selecting the volume of each tank and the initial pressure of the high-pressure gas tank 11, and cavitation does not occur in the entire hydraulic system.

[0127] It should be noted that the installation position of the air-water separation water hammer buffer 10 is finally determined after calculation with reference to the setting of the ordinary pressure regulating tank.

[0128] The volume, diameter of the high-pressure gas tank 11 and the initial value of the gas volume in the air-water mixed tank 12 need to be selected according to the calculation results of the stable working condition of the hydraulic system, with reference to the setting requirements of the ordinary pressure regulating tank and combined with the actual engineering experience, and finally determined through the calculation results of the hydraulic transient.

[0129] The gas pressure in the high-pressure gas tank 11 can be determined according to the calculation results of the pressure at the stable working condition node of the hydraulic system, and the initial value is about 1.1 times of the pressure at the node, and finally determined through the calculation results of the hydraulic transient.

[0130] The gas pressure in the high-pressure gas tank 11 can also be reduced by increasing the initial pressure of the high-pressure gas tank 11.

[0131] In addition, it should be noted that the order of each step can be adjusted appropriately during actual calculation according to actual needs, which is not limited herein.

[0132] The present application can accurately calculate the transient parameter calculation value of the water separation water hammer buffer by constructing the equation group among the four parameters of the mixed gas pressure, the water volume flow into the tank, the mixed gas temperature and the mixed gas volume after the gas in the high-pressure gas tank 11 and the air-water mixed tank 12 is mixed, constructing the functional expression between the water volume flow into the tank, the mixed gas temperature and the total energy of the mixed gas, combining the equation group and using Newton iteration method to solve the functional expression. Further, the calculation value of the water volume flow into the tank is substituted into the equation group to obtain the calculation value of the mixed gas pressure, the calculation value of the mixed gas temperature and the calculation value of the mixed gas volume. These transient parameters can truly reflect the transient hydraulic characteristics of the air-water separation water hammer buffer 10. The calculation process of the method is simple and the cost is low.

[0133] The above is only several embodiments of the present application, and does not limit the present application in any form. Although the preferred embodiments are disclosed above, the present application is not limited thereto. Any person skilled in the art can make some changes or modifications to the disclosed technical content without departing from the scope of the technical solution of the present application, which are equivalent to equivalent embodiments and belong to the scope of the technical solution.

Claims

1. A method for calculating a water hammer buffer transient based on engineering thermodynamics for gas-water separation, characterized by, The method comprises: S1, constructing a first relationship between the mixed gas pressure after gas mixing in the high-pressure gas tank and the water tank and the water volume flow into the tank in the air-water separation water hammer buffer, and constructing a second relationship between the mixed gas pressure, the water volume flow into the tank and the mixed gas temperature; S2, constructing a third relationship between the mixed gas temperature, the mixed gas volume and the mixed gas pressure, and constructing a fourth relationship between the water volume flow into the tank and the mixed gas volume; S3, forming an equation group by combining the first relationship, the second relationship, the third relationship and the fourth relationship, and constructing a function expression between the water volume flow into the tank, the mixed gas temperature and the total energy of the mixed gas; S4, solving the function expression according to the equation group and using Newton iteration method to obtain the calculation value of the water volume flow into the tank.

2. The method of claim 1, wherein, The S1 of constructing the first relationship between the mixed gas pressure after gas mixing in the high-pressure gas tank and the water tank and the water volume flow into the tank in the air-water separation water hammer buffer specifically comprises: According to the first law of thermodynamics, a fifth relationship between the internal energy difference of the mixed gas after gas mixing in the high-pressure gas tank and the water tank and the work done by the mixed gas to the outside is constructed; A sixth relationship between the mixed gas pressure, the water volume flow into the tank and the work done by the mixed gas to the outside is constructed, and a seventh relationship between the mixed gas pressure, the water volume flow into the tank and the internal energy difference of the mixed gas is constructed; The first relationship between the mixed gas pressure and the water volume flow into the tank is determined according to the fifth relationship, the sixth relationship and the seventh relationship.

3. The method of claim 2, wherein, The S1 of constructing the second relationship between the mixed gas pressure, the water volume flow into the tank and the mixed gas temperature specifically comprises: An eighth relationship between the mixed gas temperature and the work done by the mixed gas to the outside is constructed; The second relationship between the mixed gas pressure, the water volume flow into the tank and the mixed gas temperature is determined according to the sixth relationship and the eighth relationship.

4. The method of claim 1, wherein, The S4 specifically comprises: S41, according to the equation group and using Newton iteration method to solve the function expression, the flow difference between the water volume flow into the tank in the current iteration and the water volume flow into the tank in the previous iteration is obtained; S42, the relative error between the front and back iterations is calculated according to the flow difference; S43, it is judged whether the relative error between the front and back iterations is less than or equal to an error threshold value, if yes, the iteration is stopped, and the calculation value of the water volume flow into the tank is obtained, if not, S41 to S43 are repeatedly executed.

5. The method of claim 4, wherein, The S42 is specifically: The ratio of the flow difference to the water volume flow into the tank in the current iteration is calculated, and the absolute value of the ratio is taken as the relative error between the front and back iterations.

6. The method of claim 1, wherein, After the S4, the method further comprises: The calculation value of the mixed gas volume increment is determined according to the calculation value of the water volume flow into the tank.

7. The method of claim 1, wherein, After the S4, the method further comprises: The calculated value of the mixed gas pressure, the calculated value of the mixed gas temperature and the calculated value of the mixed gas volume are obtained by substituting the calculated value of the flow volume of the water body into the tank into the equation set.

8. The method of claim 1, wherein, Before the S1, the method further comprises: Before the S1, the method further comprises:

9. The method of claim 1, wherein, If the electromagnetic valve between the high-pressure gas tank and the gas-water mixing tank in the gas-water separation water hammer buffer is opened, the S1 is executed. The high-pressure gas tank and the gas-water mixing tank are both adiabatic containers.

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