Transient calculation method for gas-water separation water hammer buffer based on engineering thermodynamics

Abstract

The application discloses a kind of based on engineering thermodynamics gas-water separation water hammer buffer transient calculation method, belong to the technical field of hydraulic transient calculation, can solve the problem that existing method cannot reflect gas-water separation water hammer buffer transient hydraulic characteristics.Said method includes: S1, constructs the first relationship of mixed gas pressure and the volume flow rate of water body flowing into tank, and the second relationship of mixed gas pressure, the volume flow rate of water body flowing into tank and mixed gas temperature;S2, constructs the third relationship of mixed gas temperature, mixed gas volume and mixed gas pressure, and the fourth relationship of the volume flow rate of water body flowing into tank and mixed gas volume;S3, simultaneously solve the above-mentioned relationship formula formation equation group, and construct the function expression of the volume flow rate of water body flowing into tank, mixed gas temperature and mixed gas total energy;S4, according to equation group, and function expression is solved, obtains the calculation value of the volume flow rate of water body flowing into tank.The application 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 novel water hammer protection measure, there is currently no applicable computational model for this gas-water separation water hammer buffer during hydraulic transient processes. Using experimental methods not only carries inherent risks and is extremely costly, but also, for large and complex pipe networks, the combined influence of other components during the experiment may prevent a true reflection of the component's transient hydraulic characteristics. Furthermore, due to the presence of a two-phase (gas and water) problem during hydraulic transients, numerical simulation methods are also difficult to apply to numerical calculations of the gas-water separation water hammer buffer. Summary of the Invention

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

[0006] This invention provides a transient calculation method for a water hammer buffer in gas-water separation based on engineering thermodynamics, the method comprising:

[0007] S1. Construct a first relationship between the pressure of the mixed gas after mixing the gas in the high-pressure gas tank and the gas-water mixing tank in the gas-water separation water hammer buffer and the volumetric flow rate of the water flowing into the tank; and construct a second relationship between the pressure of the mixed gas, the volumetric flow rate of the water flowing into the tank and the temperature of the mixed gas.

[0008] S2. Construct a third relationship between the temperature of the mixed gas, the volume of the mixed gas, and the pressure of the mixed gas, and construct a fourth relationship between the volumetric flow rate of the water flowing into the tank and the volume of the mixed gas;

[0009] S3. Combine the first relation, the second relation, the third relation, and the fourth relation to form a system of equations, and construct a functional expression between the volumetric flow rate of the water flowing into the tank, the temperature of the mixed gas, and the total energy of the mixed gas.

[0010] S4. Based on the set of equations and using Newton's iteration method to solve the function expression, the calculated value of the volumetric flow rate of the water flowing into the tank is obtained.

[0011] Optionally, the first relationship between the pressure of the mixed gas after mixing in the high-pressure gas tank and the gas-water mixing tank in the gas-water separation water hammer buffer in step S1 and the volumetric flow rate of the water flowing into the tank specifically includes:

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

[0013] A sixth relationship is established between the pressure of the mixed gas, the volumetric flow rate of the water flowing into the tank, and the work done by the mixed gas on the outside. A seventh relationship is also established between the pressure of the mixed gas, the volumetric flow rate of the water flowing into the tank, and the internal energy difference of the mixed gas.

[0014] The first relationship between the pressure of the mixed gas and the volumetric flow rate of the water flowing into the tank is determined based on the fifth, sixth, and seventh relationships.

[0015] Optionally, the second relationship between the mixed gas pressure, the volumetric flow rate of the water entering the tank, and the mixed gas temperature is constructed in step S1, specifically including:

[0016] Construct an eighth equation relating the temperature of a gas mixture to the work done by the gas mixture on its surroundings;

[0017] The second relationship between the mixed gas pressure, the volumetric flow rate of the water flowing into the tank, and the mixed gas temperature is determined based on the sixth and eighth relationships.

[0018] Optionally, S4 specifically includes:

[0019] S41. Based on the set of equations and using Newton's iteration method to solve the function expression, obtain the flow rate difference between the volumetric flow rate of water flowing into the tank in the current iteration and the volumetric flow rate of water flowing into the tank in the previous iteration.

[0020] S42. Calculate the relative error between the previous and subsequent iterations based on the flow difference;

[0021] S43. Determine whether the relative error between the previous and subsequent iterations is less than or equal to the error threshold. If yes, stop the iteration and obtain the calculated value of the volumetric flow rate of the water flowing into the tank. If no, repeat S41 to S43.

[0022] Optionally, S42 specifically includes:

[0023] Calculate the ratio of the flow difference to the volumetric flow rate of water entering the tank in the current iteration, and use the absolute value of the ratio as the relative error between the previous and subsequent iterations.

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

[0025] The calculated value of the volume increment of the mixed gas is determined based on the calculated value of the volumetric flow rate of the water flowing into the tank.

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

[0027] Substituting the calculated value of the volumetric flow rate of the water flowing into the tank into the system of equations, we obtain the calculated values ​​of the mixed gas pressure, the mixed gas temperature, and the mixed gas volume.

[0028] Optionally, prior to S1, the method further includes:

[0029] Determine whether the solenoid valve between the high-pressure gas tank and the gas-water mixing tank in the gas-water separator water hammer buffer is open. If it is open, execute S1.

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

[0031] The beneficial effects that this invention can produce include:

[0032] This invention provides a transient calculation method for a gas-water separation water hammer buffer based on engineering thermodynamics. It constructs a system of equations relating four parameters: the pressure of the mixed gas after mixing in the high-pressure gas tank and the gas-water mixing tank; the volumetric flow rate of the water flowing into the tank; the temperature of the mixed gas; and the volume of the mixed gas. Then, it constructs functional expressions relating the volumetric flow rate of the water flowing into the tank, the temperature of the mixed gas, and the total energy of the mixed gas. Combining these equations and solving the functional expressions using Newton's iteration method, the transient parameters of the water separation water hammer buffer can be accurately calculated. Furthermore, substituting the calculated value of the volumetric flow rate of the water flowing into the tank into the equations yields the calculated values ​​of the mixed gas pressure, temperature, and volume. These transient parameters accurately reflect the transient hydraulic characteristics of the gas-water separation water hammer buffer. This method is simple to calculate and has low cost. Attached Figure Description

[0033] Figure 1 A schematic diagram of a water hammer buffer structure for gas-liquid separation provided by existing technology;

[0034] Figure 2 A flowchart of the transient calculation method for a water hammer buffer in gas-water separation provided in an embodiment of the present invention;

[0035] Figure 3 A hydraulic system diagram of a gas-water separation water hammer buffer provided in an embodiment of the present invention;

[0036] Figure 4 A schematic diagram illustrating the change in gas flow rate over time within the gas-water separation water hammer buffer during the pump power-off valve closure process, provided in an embodiment of the present invention.

[0037] Figure 5 This is a schematic diagram illustrating the change in gas volume over time within the gas-water separation water hammer buffer during the pump power-off valve closure process, as provided in an embodiment of the present invention.

[0038] Figure 6 A schematic diagram illustrating the change of gas pressure over time in the gas-water separation water hammer buffer during the pump power failure valve closure process, as provided in an embodiment of the present invention.

[0039] Figure 7 This is a schematic diagram illustrating the pressure change at point 1 over time during the pump power-off valve closure process, as provided in an embodiment of the present invention.

[0040] Figure 8 A schematic diagram illustrating the change of pump speed over time during the pump de-energization valve closure process, provided in an embodiment of the present invention.

[0041] Figure 9 This is a schematic diagram of the hydraulic system envelope during the valve closure process after a pump power failure, provided as an embodiment of the present invention.

[0042] Figure label:

[0043] 10. Gas-water separator water hammer buffer; 11. High-pressure gas tank; 12. Gas-water mixing tank; 13. Solenoid valve. Detailed Implementation

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

[0045] This invention provides a transient calculation method for a gas-water separation water hammer buffer based on engineering thermodynamics, such as... Figure 2 and Figure 3 As shown, the method includes:

[0046] S1. Construct a first relationship between the pressure of the mixed gas after the gas in the high-pressure gas tank 11 and the gas-water mixing tank 12 in the gas-water separation water hammer buffer 10 and the volumetric flow rate of the water flowing into the tank. Construct a second relationship between the pressure of the mixed gas, the volumetric flow rate of the water flowing into the tank and the temperature of the mixed gas.

[0047] The first relationship between the pressure of the mixed gas after mixing in the high-pressure gas tank 11 and the gas-water mixing tank 12 in the above-mentioned gas-water separation water hammer buffer 10 and the volumetric flow rate of the water flowing into the tank specifically includes:

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

[0049] Based on the first law of thermodynamics, the energy equation for the interaction between the gas mixing process and the water body is established as follows:

[0050] ;

[0051] in, This represents the heat absorbed by the gas from its surroundings. Since the gas boundary is adiabatic, therefore... ; The total energy difference of the mixed gas is taken as the factor, and the kinetic and potential energy of the gas within the object of study are neglected. Therefore, Only the internal energy difference of the mixed gas ,Right now ; The specific thermodynamic energy of the outflowing mixed gas; The mass of the mixed gas outflow. The specific thermodynamic energy of the gas mixture flowing in; The mass of the mixed gas flowing in; The outflow velocity of the mixed gas; The inflow velocity of the mixed gas; The work done by the gas mixture on the surroundings.

[0052] In this invention, regarding the gas-water separation water hammer buffer 10 as a whole, since there is no gas flow in or out, the aforementioned mixed gas outflow quality is... Mass of mixed gas flowing in Flow rate of mixed gas Flow rate of mixed gas All are 0.

[0053] This leads to the internal energy difference of the mixed gas. Work done by the gas mixture on the outside The fifth relation between them is as follows:

[0054] .

[0055] (2) Construct the sixth relationship between the pressure of the mixed gas, the volumetric flow rate of the water flowing into the tank and the work done by the mixed gas on the outside, and construct the seventh relationship between the pressure of the mixed gas, the volumetric flow rate of the water flowing into the tank and the internal energy difference of the mixed gas.

[0056] Work done by the gas mixture on the outside It is generally derived using the following formula:

[0057] ;

[0058] in, The pressure of the mixed gas; The volume of the gas mixture during expansion / compression.

[0059] Based on the above formula, calculate in The work done by the gas mixture on the outside within a time interval Then the pressure of the mixed gas is obtained. Flow rate of water into the tank Work done by the gas mixture on the outside The sixth relation between them is as follows:

[0060] ;

[0061] in, The volumetric flow rate of the water entering the tank; The initial pressure of the gas inside the gas-water mixing tank 12.

[0062] Mixed gas pressure Flow rate of water into the tank Energy difference with the mixed gas The seventh relation between them is as follows:

[0063] ;

[0064] 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.

[0065] The initial specific thermodynamic energy of the above-mentioned mixed gas The following formula is used to derive:

[0066] ,

[0067] 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.

[0068] (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.

[0069] Mixed gas pressure Volumetric flow rate of water flowing into the tank The first relation between them is shown below:

[0070] .

[0071] 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:

[0072] (1) Constructing the temperature of the mixed gas Work done by the gas mixture on the outside The eighth relation between them.

[0073] The eighth relation is shown below:

[0074] ;

[0075] in, The specific heat capacity at constant volume of the gas mixture. The mass of the mixed gas.

[0076] (2) Determine the pressure of the mixed gas according to the sixth and eighth relations. Flow rate of water into the tank With the temperature of the mixed gas The second relation between them.

[0077] The second relation is shown below:

[0078] .

[0079] S2. Construct a third relationship between the temperature, volume and pressure of the mixed gas, and a fourth relationship between the volumetric flow rate of the water flowing into the tank and the volume of the mixed gas.

[0080] Mixed gas temperature Volume of mixed gas With the pressure of the mixed gas The third relation between them is shown below:

[0081] ;

[0082] in, The volume of the mixed gas; The temperature of the mixed gas; is the gas volume constant.

[0083] Mass of mixed gas after adiabatic gas injection The following formula is used to derive:

[0084] .

[0085] Volumetric flow rate of water flowing into the tank With the volume of the mixed gas The fourth relation between them is shown below:

[0086] ;

[0087] in, The initial gas volume inside the high-pressure gas tank 11; The initial gas volume is the volume of gas in the gas-water mixing tank 12.

[0088] S3. Combine the first, second, third, and fourth relations to form a system of equations, and construct a functional expression relating the volumetric flow rate of the water entering the tank, the temperature of the mixed gas, and the total energy of the mixed gas.

[0089] Volumetric flow rate of water flowing into the tank Temperature of mixed gas Total energy of the mixed gas The function expressions between them are shown below:

[0090] .

[0091] S4. Based on the system of equations and using Newton's iterative method to solve the function expression, the calculated value of the volumetric flow rate of the water flowing into the tank is obtained.

[0092] Specifically, it includes:

[0093] S41. Based on the system of equations and by using Newton's iteration method to solve the function expression, obtain the flow rate difference between the volumetric flow rate of water flowing into the tank in the current iteration and the volumetric flow rate of water flowing into the tank in the previous iteration.

[0094] The flow difference is obtained using the Newton-Raphson method (i.e., Newton's iteration method). .

[0095] Traffic difference The following formula is used to derive:

[0096] ;

[0097] in, The internal energy of the gas inside the initial high-pressure gas tank 11 and the gas-water mixing tank 12 after thermal mixing.

[0098] S42. Calculate the relative error between the previous and subsequent iterations based on the flow difference.

[0099] Specifically, the ratio of the flow difference to the volumetric flow rate of water entering the tank in the current iteration is calculated, and the absolute value of the ratio is used as the relative error between the previous and subsequent iterations.

[0100] S43. Determine whether the relative error between the previous and subsequent iterations is less than or equal to the error threshold. If yes, stop the iteration and obtain the calculated value of the volumetric flow rate of the water flowing into the tank. If no, repeat S41 to S43.

[0101] Based on the relative error between iterations Determine whether the iteration within this time step has ended. If If the condition is met, return to S41; otherwise, the iteration ends.

[0102] in, This is the preset error threshold.

[0103] Furthermore, prior to S1, the method further includes:

[0104] 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.

[0105] Both the high-pressure gas tank 11 and the gas-water mixing tank 12 are insulated containers.

[0106] First, set the opening parameters for solenoid valve 13.

[0107] 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:

[0108] If the gas-water separation water hammer buffer 10 is in working condition, then Otherwise, let This indicates that solenoid valve 13 is closed.

[0109] Then, determine whether solenoid valve 13 is open.

[0110] 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.

[0111] 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.

[0112] Furthermore, after S4, the method further includes:

[0113] 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 is shown in the following formula:

[0114] ;

[0115] in, This represents the volume increment of the mixed gas.

[0116] Furthermore, after S4, the method further includes:

[0117] Substituting the calculated volumetric flow rate of the water flowing into the tank into the equations, we obtain the calculated values ​​of the mixed gas pressure, mixed gas temperature, and mixed gas volume.

[0118] Specifically, the volumetric flow rate of the water flowing into the tank. Substituting the calculated value into the first relational expression, we can obtain the pressure of the mixed gas. The calculated value; the volumetric flow rate of the water flowing into the tank. Substituting the calculated value into the fourth relation, we can obtain the volume of the mixed gas. The calculated value; the pressure of the mixed gas Calculated values ​​and mixed gas volume Substituting the calculated value into the third relational expression, we can obtain the temperature of the mixed gas. The calculated value.

[0119] In practical applications, the calculation process can be divided into two types depending on whether the solenoid valve 13 between the high-pressure gas tank 11 and the gas-water mixing tank 12 is open: if the solenoid valve 13 is not open, only the gas-water mixing tank 12 works (used as a conventional pressure regulating tank), and the same calculation method as that for conventional pressure regulating tanks is adopted; if the solenoid valve 13 is open, the calculation method in this invention is adopted.

[0120] The calculation method of the present invention 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 velocity and position height of the gas in the high-pressure gas tank 11 and the gas-water mixing tank 12 is ignored.

[0121] The ideal gas inside the container is air.

[0122] 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. The high-pressure gas tank 11 and the gas-water mixing tank 12 can be regarded as a single container, that is, completely connected. At this time, the gases in the two tanks are instantly and completely mixed.

[0123] The high-pressure gas tank 11 and the gas-water mixing tank 12 can be assumed to be insulated containers, or the heat transfer through the tank wall can be calculated according to the actual situation.

[0124] Another embodiment of the present invention provides a hydraulic system for a gas-water separation water hammer buffer, such as... Figure 3 As shown, the system consists of upstream and downstream reservoirs, pipelines, pumps, valves, and two sets of gas-water separation water hammer buffers 10. To reduce the pressure drop after the valves during an accident, two gas-water separation water hammer buffers 10 are installed at points 1 and 5 respectively. The upstream and downstream reservoir liquid level elevations are 16 m and 25.5 m, respectively. The total pipeline length is 40,000 m, and the pump's rated head is 53 m with a rated speed of 1480 r / min. When the pump is de-energized, the two-stage valves downstream of the pump are butterfly valves, with a closing pattern of 85% rapid closure in 3 seconds and the remaining 15% closure in 10 seconds, for a total valve closure time of 13 seconds. Based on the method provided by this invention, the pressure at the main nodes of the hydraulic system, as well as the changes in gas pressure, flow rate, temperature, and volume within the gas-water separation water hammer buffers 10, are calculated.

[0125] In this embodiment, the high-pressure gas tank 11 in the gas-water separation water hammer buffer 10 at the fork point has a volume of 8m³. 3 The initial pressure is 60.3 mH2O, and the volume of gas-water mixing tank 12 is 23 m³. 3 The gas volume is 0.5 m³. 3 The high-pressure gas tank 11 in the gas-water separation water hammer buffer 10 at the 5th intersection has a volume of 10m³. 3 The initial pressure is 32.6 mH2O, and the volume of gas-water mixing tank 12 is 19 m³. 3 The gas volume is 1m³ 3 .

[0126] The transient hydraulic characteristics of the gas-water separation water hammer buffer 10 during the pump power failure and valve closure process are as follows: Figures 4 to 9 The figures shown are: gas flow rate over time in the gas-water separation water hammer buffer 10 during the pump de-energization valve closure process; gas volume and pressure over time in the gas-water separation water hammer buffer 10 during the closure process; pressure over time at point 1; pump speed over time; and hydraulic system envelope diagram. Figure 9 The blue line represents the maximum head envelope, the green line represents the minimum head envelope, the gray line represents the liquid level envelope, and the red line represents the hydraulic gradient envelope.

[0127] The final calculation results of the calculation method proposed in this invention show that cavitation does not occur in the entire hydraulic system. The pressure is lowest at point 5, but it is still about 1m above the elevation at that point. At point 1, the minimum residual water in the air-water separation water hammer buffer 10 is 1m. 3 At the 5-fork point, the air-water separation water hammer buffer has a minimum residual water level of 1m³. 3When using the gas-water separation water hammer buffer 10 for protection, the total volume of the tank can be significantly reduced compared to the traditional pressure regulating tank. By using the gas-water separation water hammer buffer 10 for water hammer protection and rationally selecting the volume of each tank and the initial pressure of the high-pressure gas tank 11, the volume of the gas-water separation water hammer buffer 10 can be effectively reduced, while ensuring that cavitation does not occur in the entire hydraulic system.

[0128] It should be noted that the installation position of the gas-water separation water hammer buffer 10 was determined after calculation, with reference to the setting of a common pressure regulating tank.

[0129] The initial values ​​of the volume and diameter of the high-pressure gas tank 11 and the gas volume in the gas-water mixing tank 12 need to be selected based on the calculation results of the hydraulic system's stable operating conditions, with reference to the setting requirements of ordinary pressure regulating tanks, and combined with practical engineering experience. Finally, they are determined through hydraulic transient calculation results.

[0130] The gas pressure inside the high-pressure gas tank 11 can be determined based on the pressure calculation results at the node of the hydraulic system under stable operating conditions. The initial value is about 1.1 times the pressure at the node, and the final value is determined based on the calculation results of hydraulic transients.

[0131] The gas pressure inside the high-pressure gas tank 11 can also be reduced by increasing the initial pressure of the high-pressure gas tank 11, thereby reducing the volume of the high-pressure gas tank 11.

[0132] It should also be noted that the order of each step can be adjusted appropriately according to actual needs during the calculation process, and no restrictions are imposed here.

[0133] This invention constructs a set of equations relating four parameters in the gas-water separation water hammer buffer 10: the pressure of the mixed gas after mixing in the high-pressure gas tank 11 and the gas-water mixing tank 12, the volumetric flow rate of the water flowing into the tank, the temperature of the mixed gas, and the volume of the mixed gas. Then, it constructs functional expressions relating the volumetric flow rate of the water flowing into the tank, the temperature of the mixed gas, and the total energy of the mixed gas. Combining these equations and solving the functional expressions using Newton's iteration method, the transient parameters of the water separation water hammer buffer can be accurately calculated. Furthermore, substituting the calculated value of the volumetric flow rate of the water flowing into the tank into the equations yields the calculated values ​​of the mixed gas pressure, temperature, and volume. These transient parameters accurately reflect the transient hydraulic characteristics of the gas-water separation water hammer buffer 10. This method is simple to calculate and has low cost.

[0134] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within 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 and the water volume flow into the tank in a high-pressure gas tank and a gas-water mixing tank in a gas-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; the first relationship is as follows: ； wherein, is the initial specific thermodynamic energy of the mixture gas; is the pressure of the mixture gas; is the initial pressure of the gas in the gas-water mixing tank; is the volume flow rate of the water flowing into the tank; is the volume flow rate of the water flowing into the tank at the previous time. The second relationship is as follows: ； wherein, is the mass of the mixture gas; is the specific heat capacity of the mixture gas at constant volume, is the temperature of the mixture gas; 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; the third relationship is as follows: ； wherein, is the gas volume constant; is the mixed gas volume; The fourth relationship is as follows: ； wherein, Vgas0 is the gas volume in the gas-water mixing tank at the initial moment; Vgas0 is the gas volume in the gas-water mixing tank at the initial moment; 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, according to the equation group, and using Newton iteration method to solve the function expression, obtaining the calculation value of the water volume flow into the tank; The S4 specifically comprises: S41, according to the equation group, and using Newton iteration method to solve the function expression, obtaining 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; S42, calculating the relative error of the front and back iterations according to the flow difference; S43, judging whether the relative error of the front and back iterations is less than or equal to an error threshold, if yes, stopping iteration, and obtaining the calculation value of the water volume flow into the tank, if not, repeating S41 to S43; The function expression is as follows: ； wherein, is the total energy of the mixture gas.

2. The method of claim 1, wherein, In the S1, the first relationship between the mixed gas pressure after gas mixing and the water volume flow into the tank in a high-pressure gas tank and a gas-water mixing tank in a gas-water separation water hammer buffer is specifically constructed as follows: According to the first law of thermodynamics, a fifth relationship between the internal energy difference of the mixed gas after gas mixing and the work done by the mixed gas to the outside in a high-pressure gas tank and a gas-water mixing tank in a gas-water separation water hammer buffer 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, In the S1, the second relationship between the mixed gas pressure, the water volume flow into the tank, and the mixed gas temperature is specifically constructed as follows: 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 S42 is specifically as follows: The absolute value of the ratio of the flow difference to the water volume flow into the tank in the current iteration is calculated as the relative error of the front and back iterations.

5. The method of claim 1, wherein, After the S4, the method further comprises: According to the calculated value of the water inflow volume flow rate, a calculated value of the mixed gas volume increment is determined.

6. The method of claim 1, wherein, After the S4, the method further comprises: The calculated value of the water inflow volume flow rate 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.

7. The method of claim 1, wherein, Before the S1, the method further comprises: It is judged whether 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, and if opened, the S1 is executed.

8. The method of claim 1, wherein, The high-pressure gas tank and the gas-water mixing tank are both adiabatic containers.

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