Method for determining valve opening curve and valve opening control method for vent valve in natural gas vent system

Abstract

The present invention provides a method for determining the opening curve of a vent valve of a natural gas venting system, a valve opening control method and a control system. The method for determining the opening curve includes: 1) determining the vent valve opening, the Mach number of the gas at the outlet of the vent riser and the sound pressure level at the vent observation point at the initial moment; 2) judging whether the Mach number is less than the rated Mach number and the sound pressure level is less than the rated sound pressure level; if the valve adjustment amplitude value is determined, the vent valve opening is the current opening plus the valve adjustment amplitude value; if not, the vent valve opening is the current opening; 3) judging whether the vent valve opening is greater than 100%; if the vent valve opening at the current time step is 100%; if not, the vent valve opening at the current time step is the vent valve opening at step 2); 4) obtaining the gas Mach number and the sound pressure level at the vent observation point at the next time step, repeating steps 2)-3) to determine the vent valve opening at the next time step; 5) determining the vent valve opening at different venting moments according to the vent valve opening at each time step, and obtaining the vent valve opening curve.

Description

Technical Field

[0001] The present invention relates to the field of natural gas transmission technology, and in particular to a method for determining a vent valve opening curve of a natural gas vent system, a method for controlling the opening of a vent valve of a natural gas pipeline vent system, and a device for controlling the opening of a vent valve of a natural gas pipeline vent system. Background Art

[0002] The natural gas venting system is an important part of the natural gas pipeline station and valve room, and is an important guarantee facility for the safe and reliable operation of the natural gas pipeline. When the natural gas pipeline is put into operation, emergency response, maintenance and repair of equipment and facilities, it is often necessary to carry out natural gas venting operations, that is, to discharge all or part of the natural gas in a certain section of the pipeline or a station into the atmosphere through the natural gas venting system, and to inject inert gases such as nitrogen into the pipeline to replace the residual natural gas. The venting valve is a key component in the natural gas venting system. During the venting process, the pressure drop rate of the vented pipe section will change with time differently depending on the adjustment method of the venting valve opening, and the parameters such as the natural gas Mach number, noise, and flow rate (volume) at the outlet of the venting riser will also change significantly. During the natural gas venting operation, it is usually necessary to control the pressure drop rate of the vented pipe section, the venting volume, and the venting time by adjusting the opening of the venting valve. In addition, in order to reduce the adverse effects such as noise, low temperature, and riser vibration generated during the venting process, it is necessary to study the opening control of the venting valve.

[0003] At present, in the actual gas pipeline venting project, the venting operation is usually required to be completed within a certain period of time, so the venting flow rate cannot be too small. At the same time, considering the noise generated during venting and the reaction force on the venting riser, the venting flow rate cannot be too large. On-site staff generally observe the venting riser outlet noise, venting flame height or riser vibration, etc., and manually operate the vent valve based on experience, and control the venting process by controlling the vent valve opening. This operation has the following three defects:

[0004] (1) The staff controls the venting process by manually operating the vent valve. Since they cannot accurately understand the specific flow state of the gas during the venting process, the valve opening operation (valve adjustment time and valve adjustment range) is completely dependent on operating experience. The formulation of the valve opening plan lacks accurate judgment criteria. The valve opening plan is affected by factors such as the operating experience and business level of the vent valve operator and the environment around the vent pipe.

[0005] (2) The noise and vibration generated during the venting process will pose a threat to the health of the operator. The operator cannot continuously control the vent valve and can only use one-stage venting or step-by-step venting. The maximum discharge flow cannot be reduced to the greatest extent, and the health hazards caused by noise cannot be effectively avoided.

[0006] (3) During the venting process, there is no early warning for harmful parameters such as venting noise and riser vibration. If the harmful parameters exceed the standard, it will cause harm to personnel and the environment.

[0007] In summary, there are great limitations in adjusting the vent valve based on experience alone. Therefore, it is necessary to further study the opening control of the vent valve during the venting process and develop an optimal opening control scheme suitable for different venting operation scenarios, so as to achieve flexible and precise adjustment of the vent valve to the venting operation process. Summary of the invention

[0008] The object of the present invention is to provide a method for determining a valve opening curve of a vent valve in a natural gas vent system; the valve opening curve determined by the method can well guide the valve opening operation of the vent valve in the natural gas vent system, thereby achieving a relatively large and relatively stable vent flow rate while the noise meets the specified requirements, and completing the venting operation faster.

[0009] The object of the present invention is to provide a vent valve control method and control device for a natural gas venting system, which can achieve a relatively large and relatively stable vent flow rate while the noise meets the specified requirements during the venting operation, and complete the venting operation quickly.

[0010] In order to achieve the above objectives, the present invention provides the following three technical solutions.

[0011] In a first aspect, the present invention provides a method for determining a vent valve opening curve of a natural gas vent system, wherein the method comprises:

[0012] 1) Determine the opening of the vent valve at the initial moment, the Mach number of the vent riser outlet gas and the sound pressure level of the vent observation point; obtain the step length of each time step; wherein the Mach number of the vent riser outlet gas and the sound pressure level of the vent observation point at the initial moment are used as the Mach number of the vent riser outlet gas and the sound pressure level of the vent observation point in the first time step;

[0013] 2) judging whether the Mach number of the gas at the outlet of the venting riser at the current time step is less than the rated Mach number and the sound pressure level at the venting observation point is less than the rated sound pressure level;

[0014] If it is satisfied, the valve adjustment amplitude value is determined, and the opening of the vent valve is the current opening plus the valve adjustment amplitude value;

[0015] If not satisfied, the opening of the vent valve remains at the current opening;

[0016] 3) determining whether the opening of the vent valve obtained in step 2) is greater than 100%;

[0017] If yes, then determine that the opening of the vent valve at the current time step is 100%;

[0018] If not, then determine the opening of the vent valve at the current time step to be the opening of the vent valve obtained in step 2);

[0019] 4) Obtain the Mach number of the gas at the outlet of the venting standpipe and the sound pressure level at the venting observation point at the next time step, and repeat steps 2 to 3) to determine the opening of the venting valve at the next time step until the opening of the venting valve at the end of the venting is determined;

[0020] 5) According to the determined opening of the vent valve at each time step, the opening of the vent valve corresponding to different venting times is obtained, thereby obtaining the vent valve opening curve.

[0021] According to the determination method provided in the first aspect, preferably, the end time of venting is determined based on actual venting experience, for example, whether the venting process is stopped is judged based on the pressure of the vented main pipe section. When the average pressure of the vented pipe section is less than 0.01 MPa (gauge pressure), the venting process ends and the calculation ends.

[0022] According to the determination method provided in the first aspect, preferably, determining the valve adjustment amplitude value includes:

[0023] When the sequence number of the current time step is greater than the rated time step number, the valve adjustment amplitude value is determined based on the absolute value of the rate of change of the sound pressure level at the venting observation point and the absolute value of the rate of change of the Mach number of the gas at the standpipe outlet;

[0024] More preferably, the step of determining the valve adjustment amplitude value based on the absolute value of the rate of change of the sound pressure level at the venting observation point and the absolute value of the rate of change of the Mach number of the gas at the standpipe outlet comprises:

[0025] Determine the first valve adjustment amplitude value according to the absolute value of the rate of change of the sound pressure level at the venting observation point and the absolute value of the rate of change of the Mach number of the gas at the standpipe outlet;

[0026] Determine whether the first valve adjustment amplitude value is greater than the first rated valve adjustment amplitude value;

[0027] If it is satisfied, the valve adjustment amplitude value is equal to the first rated valve adjustment amplitude value;

[0028] If not, the valve adjustment amplitude value is equal to the first valve adjustment amplitude value;

[0029] Further preferably, the absolute value of the rate of change of the sound pressure level is determined by the following formula:

[0030]

[0031] Where, k1 is the absolute value of the rate of change of the sound pressure level at the emptying observation point, dimensionless; Lp1 and Lp2 are the sound pressure levels at the emptying observation point at the current time step and the previous time step, dB; Δτ is the time step, min;

[0032] Further preferably, the absolute value of the rate of change of the Mach number is determined by the following formula:

[0033]

[0034] Where k2 is the absolute value of the rate of change of the Mach number of the gas at the standpipe outlet, dimensionless; Ma1 and Ma2 are the Mach numbers of the gas at the standpipe outlet at the current time step and the previous time step, dimensionless; Δτ is the time step, min;

[0035] Further preferably, the first valve adjustment amplitude value is determined according to the following formula:

[0036] Value_tf=a×(k1+k2)+b

[0037] Wherein, Value_tf is the valve amplitude value, %; k1 is the absolute value of the rate of change of the sound pressure level at the venting observation point; k2 is the absolute value of the rate of change of the Mach number at the standpipe outlet; a is the coefficient, ranging from 500 to 1000; b is the coefficient, ranging from 0.1 to 0.5.

[0038] Further preferably, the first rated valve adjustment amplitude value may have a value range of 0.5%-5% (assuming that the opening degree when fully open is 100%).

[0039] According to the determination method provided in the first aspect, preferably, determining the valve adjustment amplitude value includes:

[0040] When the sequence number of the current time step is less than or equal to the rated time step number, the valve adjustment amplitude value is equal to the second rated valve adjustment amplitude value;

[0041] More preferably, the second rated valve adjustment amplitude value may have a value range of 0.1%-0.5% (based on the fully open opening being 100%).

[0042] According to the determination method provided in the first aspect, preferably, the step of obtaining the Mach number of the gas at the outlet of the venting riser and the sound pressure level of the venting observation point includes:

[0043] Obtain the flow rate, mass flow, density and temperature of the gas at the outlet of the vent riser;

[0044] Determine the Mach number of the gas at the venting standpipe outlet based on the flow rate of the gas at the venting standpipe outlet;

[0045] The sound pressure level at the venting observation point is determined based on the flow rate, mass flow rate, density and temperature of the venting riser outlet gas; more preferably, the sound pressure level at the venting observation point is determined by the following formula:

[0046] W a =ηW m

[0047]

[0048] L w =10log 10 W a +120

[0049] L p =L w +DI-10log 10 (4πr 2 )

[0050] Among them, when the outlet gas of the venting riser is subsonic flow, When the gas at the outlet of the venting riser is at the critical sound velocity, it is determined based on the relationship between the acoustic efficiency and the sound pressure ratio of the noise generated by supercritical flow (i.e., choked flow), see Figure 2 ; Wherein, the sound pressure ratio is the ratio of the gas pressure at the vent riser outlet to the atmospheric pressure;

[0051] Where W a is the total sound power, in W; W m is the mechanical flow power, unit W; η is the acoustic efficiency, unit dimensionless; U is the flow rate of the gas at the outlet of the venting riser, unit m / s; m is the mass flow rate of the gas at the outlet of the venting riser, unit kg / s; ρ is the density of the gas at the outlet of the venting riser, unit kg / m 3 ; ρ0 is the atmospheric density, kg / m 3 ; T is the temperature of the gas at the outlet of the venting riser, unit K; T0 is the atmospheric temperature, unit K; K a is the sound power coefficient, usually 5×10 -5 ;M a is the Mach number of the gas at the outlet of the venting standpipe, unit is dimensionless; L w is the total sound power level of the airflow at the vent riser outlet, in dB; L p is the sound pressure level at the venting observation point, in dB; DI is the directivity index, in dB, usually -6 for subsonic flow (Mach number less than 1 is subsonic flow), and -1 for critical sound speed (Mach number ≥ 1 is critical sound speed); r is the distance from the venting observation point to the venting riser outlet, in m, usually 50 m;

[0052] Further preferably, obtaining the flow rate, mass flow rate, density and temperature of the vent riser outlet gas comprises:

[0053] According to the flow rate and density of the gas at the vent riser outlet and the inner diameter of the vent riser, the mass flow rate of the gas at the vent riser outlet is determined by the following formula:

[0054]

[0055] Where U is the flow rate of the gas at the venting riser outlet, in m / s; m is the mass flow rate of the gas at the venting riser outlet, in kg / s; ρ is the density of the gas at the venting riser outlet, in kg / m 3 ; d is the inner diameter of the venting riser, unit: m;

[0056] Further preferably, obtaining the flow rate, mass flow rate, density and temperature of the vent riser outlet gas comprises:

[0057] The flow rate and density of the gas at the outlet of the venting riser are determined by dynamic simulation of the venting process of the natural gas transmission pipeline; for example:

[0058] 1) Establish a dynamic simulation model of the natural gas pipeline venting process;

[0059] The basic differential equation for isothermal steady-state flow in the gas pipeline section is:

[0060] The continuity equation, momentum equation, and energy equation are:

[0061]

[0062]

[0063]

[0064] Where ρ is the gas density, kg / m 3 ; τ is the microelement time, s; A is the flow area of ​​the pipe section, m 2 ; M is the gas mass flow rate in the pipe section, kg / s; x is the microelement distance, m; P is the gas pressure, Pa; d is the inner diameter of the pipe section, m; λ is the friction coefficient, which can be calculated according to the Colebrook formula; h is the enthalpy of the gas, J / kg; s is the altitude, m; g is the acceleration of gravity, m / s 2 ; K is the total heat transfer coefficient, W / (m 2 ·K); T is the gas temperature, K; T0 is the ambient temperature, K;

[0065] 2) Determine boundary conditions

[0066] The boundary condition of the riser outlet is: first use the outlet pressure equal to the atmospheric pressure as the boundary condition. If the calculated outlet velocity is less than or equal to the local sound velocity, it means that the pressure boundary condition is reasonable for the current time step; otherwise, switch the outlet boundary condition to the outlet velocity equal to the local sound velocity.

[0067] The boundary conditions at the closed end of the gas transmission trunk line are: the mass flow rate at the closed end is 0; the gas state change at the closed end is a polymorphic process, and the polymorphic process index n can be determined based on the initial conditions and the final conditions (the final temperature is equal to the ambient temperature, and the final pressure is equal to the atmospheric pressure). The calculation formula is:

[0068] Where, T ini and T env are respectively the initial gas temperature and the ambient temperature before the trunk line is vented, K; P ini and P env are the initial gas pressure and atmospheric pressure before the trunk line is vented, Pa; n is the polytropic process index;

[0069] The boundary conditions at the vent valve are: satisfying the pressure drop formula, temperature drop formula and mass flow balance formula, as shown below:

[0070]

[0071]

[0072] M in -M out =0

[0073] Among them, P in and P out Respectively represent the gas pressure at the inlet and outlet of the resistance element, Pa; K v is the valve flow coefficient; ρ in and ρ out Respectively represent the gas density at the inlet and outlet of the resistance element, kg / m 3 ;Q in and Q out Respectively represent the actual gas volume flow rate at the inlet and outlet of the resistance element, m 3 / s;T in and T out Respectively represent the inlet and outlet gas temperatures of the resistance element, K; M in and M out Respectively represent the gas mass flow rate at the inlet and outlet of the resistance element, kg / s; D in and D out Respectively represent the gas JT effect coefficient at the inlet and outlet of the resistance element, K / MPa;

[0074] 3) The implicit central difference algorithm is used to discretely solve the dynamic simulation model of the natural gas pipeline venting process to determine the flow rate and density of the gas at the venting riser outlet.

[0075] According to the determination method provided in the first aspect, preferably, the rated sound pressure level ranges from 70-80 dB.

[0076] According to the determination method provided in the first aspect, preferably, the rated Mach number ranges from 0.7 to 0.8.

[0077] According to the determination method provided in the first aspect, preferably, the valve opening range at the initial moment is 30%-50%.

[0078] According to the determination method provided in the first aspect, preferably, the step length of each time step ranges from 30 to 120 seconds.

[0079] In a second aspect, the present invention provides a method for controlling the opening of a vent valve in a natural gas vent system, wherein the method comprises:

[0080] The opening control of the vent valve of the natural gas vent system is performed according to the vent valve opening curve of the natural gas vent system determined by the vent valve opening curve determination method of the natural gas vent system.

[0081] According to the determination method provided in the second aspect, preferably, the method further comprises:

[0082] Before controlling the opening of the natural gas venting system venting valve according to the natural gas venting system venting valve opening curve determined by the natural gas venting system venting valve opening curve determination method, the natural gas venting system venting valve is first controlled to open to a valve opening degree at an initial moment.

[0083] In a third aspect, the present invention provides a natural gas venting system venting valve opening control system, the system comprising:

[0084] Vent valve opening curve determining device: used to implement the above-mentioned method for determining the vent valve opening curve of the natural gas vent system, and determine the vent valve opening curve of the natural gas vent system;

[0085] Vent valve controller: connected to the vent valve of the natural gas vent system, used to adjust the opening of the vent valve, and connected to the automatic control device through cables;

[0086] Automatic control device: used to control the vent valve controller to adjust the vent valve opening, so as to realize the above-mentioned vent valve opening control method of the natural gas vent system;

[0087] Communication cable: used to realize communication between the vent valve opening curve determination device and the automatic control device, and between the automatic control device and the vent valve controller.

[0088] According to the determination method provided in the third aspect, preferably, the vent valve controller is further used to feed back the vent valve opening information to the automatic control device; and the automatic control device is further used to receive and store the vent valve actual opening information fed back by the vent valve controller.

[0089] According to the determination method provided in the third aspect, preferably, the natural gas venting system vent valve opening control system is further provided with pressure sensors, temperature sensors, flow meters and other equipment for collecting pressure, temperature and flow data at the vent riser outlet; the automatic control device is further used to receive and store data collected by pressure sensors, temperature sensors, flow meters and other equipment; the vent valve opening curve determination device is further used to compare these data with simulation data, and based on the analysis of errors, continuously improve the established natural gas venting system vent valve opening curve determination method.

[0090] According to the determination method provided in the third aspect, preferably, the natural gas venting system venting valve opening control system also includes a power supply for providing power guarantee to devices requiring power supply in the natural gas venting system venting valve opening control system.

[0091] Compared with the prior art, the technical solution provided by the present invention has the following technical effects:

[0092] (1) The technical solution provided by the present invention enables the venting process to maintain the venting flow rate within a relatively large and relatively stable range while the noise meets the specified requirements, thereby shortening the venting time, thereby reducing the impact of the venting operation on the gas supply to users through the pipeline, and reducing the economic losses caused by the venting operation to the pipeline operator and downstream users.

[0093] (2) The technical solution provided by the present invention can effectively control the noise generated during the venting process by adjusting the vent valve opening multiple times to avoid the adverse impact of excessive noise on the environment, can achieve nearly uniform flow venting and reduce the maximum discharge flow, can better ensure that the gas flow state during the entire venting process is subsonic flow, can effectively avoid or reduce the occurrence of vent pipe vibration, ice blockage and other phenomena, and protect the vent pipeline and related equipment.

[0094] (3) The technical solution provided by the present invention is applicable to the determination of the valve opening curve and valve opening control of the vent valve under different venting situations (different initial conditions of the vented pipe section, pipe section parameters, etc.) and venting operation types (such as single-side venting of a single pipe section, middle venting of two pipe sections, etc.).

[0095] (4) The technical solution provided by the present invention can realize automatic adjustment of the valve opening by an automatic control system during the venting process without the need for manual operation by the operator, thereby avoiding the threat to the health of the operator caused by noise and vibration generated during the venting process.

[0096] (5) The technical solution provided by the present invention determines the vent valve opening according to the gas flow state during the venting process and then controls the vent valve opening according to the determined vent valve opening curve, and is not affected by factors such as the surrounding environment of the vent pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0097] Figure 1 A flow chart of a method for determining a vent valve opening curve of a natural gas vent system provided in one embodiment of the present invention.

[0098] Figure 2 This is a graph showing the relationship between the acoustic efficiency and the sound pressure ratio of noise generated by supercritical flow (i.e., choked flow).

[0099] Figure 3 A schematic diagram of a vent valve opening control system for a natural gas vent system provided in one embodiment of the present invention.

[0100] Figure 4 This is a schematic diagram of the natural gas venting system in Example 1 of the present invention.

[0101] Figure 5 This is a flow chart of the steps for determining the opening degree of the vent valve at each time step in Example 1 of the present invention.

[0102] Figure 6 This is a flow chart for determining the valve adjustment amplitude value in Example 1 of the present invention.

[0103] Figure 7 It is the vent valve opening curve diagram of Example 1, Comparative Example 1 and Comparative Example 2.

[0104] Figure 8 The figure is a diagram of the valve adjustment amplitude values ​​at each venting time in Example 1, Comparative Example 1 and Comparative Example 2.

[0105] Fig. 9 Flow rate diagram of the riser outlet gas at each venting time of Example 1, Comparative Example 1 and Comparative Example 2.

[0106] Fig.10 The Mach number diagram of the standpipe outlet gas at each venting time of Example 1, Comparative Example 1, and Comparative Example 2.

[0107] Fig.11 The sound pressure level diagram of the riser outlet gas at each venting time of Example 1, Comparative Example 1, and Comparative Example 2.

[0108] Fig.12 The mass flow diagram of the riser outlet gas at each venting time of Example 1, Comparative Example 1 and Comparative Example 2.

[0109] Fig.13 The vented main line pressure diagram at each venting time of Example 1, Comparative Example 1 and Comparative Example 2 is shown. DETAILED DESCRIPTION

[0110] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0111] See also Figure 1 A specific embodiment of the present invention provides a method for determining a vent valve opening curve of a natural gas vent system, wherein the method comprises:

[0112] Step A1: determining the opening of the vent valve at the initial moment, the Mach number of the vent riser outlet gas and the sound pressure level of the vent observation point; obtaining the step length of each time step; wherein the Mach number of the vent riser outlet gas and the sound pressure level of the vent observation point at the initial moment are used as the Mach number of the vent riser outlet gas and the sound pressure level of the vent observation point in the first time step;

[0113] Step A2: determining whether the Mach number of the gas at the outlet of the venting riser at the current time step is less than the rated Mach number and the sound pressure level at the venting observation point is less than the rated sound pressure level;

[0114] If it is satisfied, the valve adjustment amplitude value is determined, and the opening of the vent valve is the current opening plus the valve adjustment amplitude value;

[0115] If not satisfied, the opening of the vent valve remains at the current opening;

[0116] Step A3: Determine whether the opening of the vent valve obtained in step A2 is greater than 100%;

[0117] If yes, then determine that the opening of the vent valve at the current time step is 100%;

[0118] If not, then determine that the opening of the vent valve at the current time step is the opening of the vent valve obtained in step A2;

[0119] Step A4: obtaining the Mach number of the gas at the outlet of the venting standpipe and the sound pressure level at the venting observation point at the next time step, and repeating steps A2 to A3 to determine the opening of the venting valve at the next time step until the opening of the venting valve at the end of the venting is determined;

[0120] Step A5: According to the determined opening of the vent valve at each time step, the opening of the vent valve corresponding to different venting moments is obtained, thereby obtaining a vent valve opening curve.

[0121] In the process of determining the opening curve of the vent valve of the natural gas venting system, a balance point of the valve opening is found when recursing at each time layer of the program, so that the venting operation can shorten the venting time as much as possible while meeting the noise regulations to ensure safe and smooth venting.

[0122] Furthermore, the venting end time is determined based on actual venting experience. For example, whether the venting process is stopped is judged based on the pressure of the vented main pipe section. When the average pressure of the vented pipe section is less than 0.01 MPa (gauge pressure), the venting process ends and the calculation ends.

[0123] Further, in step A2, determining the valve adjustment amplitude value includes:

[0124] When the sequence number of the current time step is greater than the rated time step number, the valve adjustment amplitude value is determined based on the absolute value of the rate of change of the sound pressure level at the venting observation point and the absolute value of the rate of change of the Mach number of the gas at the standpipe outlet;

[0125] Furthermore, the step of determining the valve adjustment amplitude value based on the absolute value of the rate of change of the sound pressure level at the venting observation point and the absolute value of the rate of change of the Mach number of the gas at the standpipe outlet includes:

[0126] Determine the first valve adjustment amplitude value according to the absolute value of the rate of change of the sound pressure level at the venting observation point and the absolute value of the rate of change of the Mach number of the gas at the standpipe outlet;

[0127] Determine whether the first valve adjustment amplitude value is greater than the first rated valve adjustment amplitude value;

[0128] If it is satisfied, the valve adjustment amplitude value is equal to the first rated valve adjustment amplitude value;

[0129] If not, the valve adjustment amplitude value is equal to the first valve adjustment amplitude value;

[0130] Furthermore, the absolute value of the rate of change of the sound pressure level is determined by the following formula:

[0131]

[0132] Where, k1 is the absolute value of the rate of change of the sound pressure level at the emptying observation point, dimensionless; Lp1 and Lp2 are the sound pressure levels at the emptying observation point at the current time step and the previous time step, dB; Δτ is the time step, min;

[0133] Furthermore, the absolute value of the rate of change of the Mach number is determined by the following formula:

[0134]

[0135] Where k2 is the absolute value of the rate of change of the Mach number of the gas at the standpipe outlet, dimensionless; Ma1 and Ma2 are the Mach numbers of the gas at the standpipe outlet at the current time step and the previous time step, dimensionless; Δτ is the time step, min;

[0136] Furthermore, the first valve adjustment amplitude value is determined according to the following formula:

[0137] Value_tf=a×(k1+k2)+b

[0138] Wherein, Value_tf is the valve adjustment amplitude value; k1 is the absolute value of the rate of change of the sound pressure level at the venting observation point; k2 is the absolute value of the rate of change of the Mach number at the standpipe outlet; a is a coefficient, and the available value range is 500-1000 (the value is 1000 in a specific implementation); b is a coefficient, and the available value range is 0.1-0.5 (the value is 0.5 in a specific implementation).

[0139] Furthermore, the first rated valve adjustment amplitude value may range from 0.5% to 5% (with the fully open opening being 100%); in a specific embodiment, the value is 5%;

[0140] By observing the changing law of the total sound pressure (noise) and Mach number at the standpipe outlet during the venting process, it can be seen that if the valve opening is not adjusted during the venting process, the changing law of the total sound pressure (noise) and Mach number at the standpipe outlet is: it will increase immediately at the initial moment of venting, and then gradually decrease; through the analysis of this law, an optimal technical solution is proposed in which the valve adjustment amplitude value of the above-mentioned venting process is determined according to the changing rate of the total sound pressure (noise) and Mach number at the standpipe outlet during the venting process; when the absolute value of the changing rate of the total sound pressure (noise) and Mach number at the standpipe outlet is large, taking a larger value of the valve adjustment amplitude can better offset the trend of the rapid decrease of noise and Mach number, and when the absolute value of the changing rate is small, taking a smaller value of the valve adjustment amplitude can better ensure that the values ​​of noise and Mach number during the valve opening adjustment process do not exceed the specified requirements; in order to avoid drastic changes in flow parameters due to excessive adjustment of the valve opening as much as possible, the maximum adjustment amplitude of the valve is set.

[0141] Further, in step A2, determining the valve adjustment amplitude value includes:

[0142] When the sequence number of the current time step is less than or equal to the rated time step number, the valve adjustment amplitude value is equal to the second rated valve adjustment amplitude value;

[0143] At the initial moment of venting, the change rate of the total sound pressure (noise) and Mach number at the standpipe outlet is large, and their values ​​are in a state of violent fluctuation. It is inconvenient to determine the valve adjustment amplitude value according to the change rate of the total sound pressure (noise) and Mach number at the standpipe outlet during the venting process. Based on this, an optimal practical solution of setting the valve adjustment amplitude value to a fixed value is proposed.

[0144] Furthermore, the second rated valve adjustment amplitude value may have a value range of 0.1%-0.5% (based on the fully open opening being 100%).

[0145] Furthermore, the steps of obtaining the Mach number of the gas at the venting riser outlet and the sound pressure level at the venting observation point include:

[0146] Obtain the flow rate, mass flow, density and temperature of the gas at the outlet of the vent riser;

[0147] Determine the Mach number of the gas at the venting standpipe outlet based on the flow rate of the gas at the venting standpipe outlet;

[0148] The sound pressure level at the venting observation point is determined based on the flow rate, mass flow rate, density and temperature of the gas at the venting riser outlet; further, the sound pressure level at the venting observation point is determined by the following formula:

[0149] W a =ηW m

[0150]

[0151] L w =10log 10 W a +120

[0152] L p =L w +DI-10log 10 (4πr 2 )

[0153] Among them, when the outlet gas of the venting riser is subsonic flow, When the gas at the outlet of the venting riser is at the critical sound velocity, it is determined based on the relationship between the acoustic efficiency and the sound pressure ratio of the noise generated by supercritical flow (i.e., choked flow), see Figure 2 ; Wherein, the sound pressure ratio is the ratio of the gas pressure at the vent riser outlet to the atmospheric pressure;

[0154] Where W a is the total sound power, in W; W m is the mechanical flow power, unit W; η is the acoustic efficiency, unit dimensionless; U is the flow rate of the gas at the outlet of the venting riser, unit m / s; m is the mass flow rate of the gas at the outlet of the venting riser, unit kg / s; ρ is the density of the gas at the outlet of the venting riser, unit kg / m 3 ; ρ0 is the atmospheric density, kg / m 3 ; T is the temperature of the gas at the outlet of the venting riser, unit K; T0 is the atmospheric temperature, unit K; K a is the sound power coefficient, usually 5×10 -5 ;Ma is the Mach number of the gas at the outlet of the venting standpipe, unit is dimensionless; L w is the total sound power level of the airflow at the vent riser outlet, in dB; L p is the sound pressure level at the venting observation point, in dB; DI is the directivity index, in dB, usually -6 for subsonic flow (Mach number less than 1 is subsonic flow), and -1 for critical sound speed (Mach number ≥ 1 is critical sound speed); r is the distance from the venting observation point to the venting riser outlet, in m, usually 50 m;

[0155] In a specific embodiment, obtaining the flow rate, mass flow rate, density, and temperature of the vent riser outlet gas includes:

[0156] According to the flow rate and density of the gas at the vent riser outlet and the inner diameter of the vent riser, the mass flow rate of the gas at the vent riser outlet is determined by the following formula:

[0157]

[0158] Wherein, U is the flow rate of the gas at the outlet of the venting riser, in m / s; m is the mass flow rate of the gas at the outlet of the venting riser, in kg / s; ρ is the density of the gas at the outlet of the venting riser, in kg / m3; d is the inner diameter of the venting riser, in m;

[0159] In a specific embodiment, obtaining the flow rate, mass flow rate, density, and temperature of the vent riser outlet gas includes:

[0160] The flow rate and density of the gas at the outlet of the venting riser are determined by dynamic simulation of the venting process of the natural gas transmission pipeline; for example:

[0161] 1) Establish a dynamic simulation model of the natural gas pipeline venting process;

[0162] The basic differential equation for isothermal steady-state flow in the gas pipeline section is:

[0163] The continuity equation, momentum equation, and energy equation are:

[0164]

[0165]

[0166]

[0167] Where ρ is the gas density, kg / m 3 ; τ is the microelement time, s; A is the flow area of ​​the pipe section, m 2; M is the gas mass flow rate in the pipe section, kg / s; x is the microelement distance, m; P is the gas pressure, Pa; d is the inner diameter of the pipe section, m; λ is the friction coefficient, which can be calculated according to the Colebrook formula; h is the enthalpy of the gas, J / kg; s is the altitude, m; g is the acceleration of gravity, m / s 2 ; K is the total heat transfer coefficient, W / (m 2 ·K); T is the gas temperature, K; T0 is the ambient temperature, K;

[0168] In the basic differential equation of isothermal steady-state flow in a gas pipeline section, the pressure drop in the pipeline section consists of three parts: friction pressure drop, potential pressure drop, and pressure drop caused by kinetic energy change. The gas velocity in the venting pipeline is very fast, and the gas kinetic energy changes greatly (the maximum difference in gas velocity between the bottom of the riser and the riser outlet is 200m / s). In order to more accurately calculate the gas flow parameters, the pressure drop caused by kinetic energy change is considered in the model.

[0169] 2) Determine boundary conditions

[0170] The boundary condition of the riser outlet is: first use the outlet pressure equal to the atmospheric pressure as the boundary condition. If the calculated outlet velocity is less than or equal to the local sound velocity, it means that the pressure boundary condition is reasonable for the current time step; otherwise, switch the outlet boundary condition to the outlet velocity equal to the local sound velocity.

[0171] In a venting riser with a constant diameter, the gas velocity will not be higher than the local sound velocity. Based on this, the present invention proposes the above-mentioned riser outlet boundary condition, which takes into account the switching of the pressure boundary condition and the velocity boundary condition at the venting riser outlet, and the gas velocity result is more accurate.

[0172] The boundary conditions at the closed end of the gas transmission trunk line are: the mass flow rate at the closed end is 0; the gas state change at the closed end is a polymorphic process, and the polymorphic process index n can be determined based on the initial conditions and the final conditions (the final temperature is equal to the ambient temperature, and the final pressure is equal to the atmospheric pressure). The calculation formula is:

[0173] Where, T ini and T env are the initial gas temperature and ambient temperature before the trunk line is vented, K; P ini and P env are the initial gas pressure and atmospheric pressure before the trunk line is vented, Pa; n is the polytropic process index;

[0174] The boundary conditions at the vent valve are: satisfying the pressure drop formula, temperature drop formula and mass flow balance formula, as shown below:

[0175]

[0176]

[0177] M in -M out =0

[0178] Among them, P in and P out Respectively represent the gas pressure at the inlet and outlet of the resistance element, Pa; K v is the valve flow coefficient; ρ in and ρ out Respectively represent the gas density at the inlet and outlet of the resistance element, kg / m 3 ;Q in and Q out Respectively represent the actual gas volume flow rate at the inlet and outlet of the resistance element, m 3 / s;T in and T out Respectively represent the inlet and outlet gas temperatures of the resistance element, K; M in and M out Respectively represent the gas mass flow rate at the inlet and outlet of the resistance element, kg / s; D in and D out Respectively represent the gas JT effect coefficient at the inlet and outlet of the resistance element, K / MPa;

[0179] 3) The implicit central difference algorithm is used to discretely solve the dynamic simulation model of the natural gas pipeline venting process to determine the flow rate and density of the gas at the venting riser outlet;

[0180] The implicit central difference method is used to solve the dynamic simulation model of the venting process. It is applicable to both the trunk pipe section and the short pipe section of the venting system. The calculation stability is unconditionally met, the selection of the time step is not restricted, and the calculation efficiency is high.

[0181] Further, the rated sound pressure level is 70-80dB.

[0182] Further, the rated Mach number is 0.7-0.8.

[0183] Furthermore, the valve opening at the initial moment is 30%-50%.

[0184] Furthermore, the step length of each time step is 30-120s.

[0185] Furthermore, the Mach number is determined by the following formula:

[0186]

[0187] Where Ma is the Mach number, dimensionless; v is the gas velocity, m / s; a is the local sound speed, m / s.

[0188] A specific embodiment of the present invention provides a method for controlling the opening of a vent valve in a natural gas vent system, wherein the method comprises:

[0189] The opening control of the vent valve of the natural gas venting system is performed according to the vent valve opening curve of the natural gas venting system determined by the embodiment of the method for determining the vent valve opening curve of the natural gas venting system.

[0190] Furthermore, the method further comprises:

[0191] Before controlling the opening of the natural gas venting system venting valve according to the natural gas venting system venting valve opening curve determined by the embodiment of the natural gas venting system venting valve opening curve determination method, the natural gas venting system venting valve is first controlled to open to the valve opening degree at the initial moment.

[0192] like Figure 3 As shown, the embodiment of the present invention also provides a natural gas venting system venting valve opening control system, the system comprising:

[0193] The vent valve opening curve determining device 31 is used to implement the method for determining the vent valve opening curve of the natural gas vent system described in each method embodiment, and determine the vent valve opening curve of the natural gas vent system;

[0194] Vent valve controller 32: connected to the vent valve of the natural gas vent system, used to adjust the opening of the vent valve, and connected to the automatic control device through a cable;

[0195] Automatic control device 33: used to control the vent valve controller 31 to adjust the vent valve opening, so as to implement the vent valve opening control method of the natural gas vent system described in each method embodiment;

[0196] Communication cable 34 : used to realize communication between the vent valve opening curve determination device 31 and the automatic control device 33 , and between the automatic control device 33 and the vent valve controller 32 .

[0197] Among them, the vent valve opening curve determining device 31 (a computer capable of implementing the method for determining the vent valve opening curve of the natural gas vent system described in each method embodiment can be selected) performs simulation to determine the vent valve opening curve of the natural gas vent system before venting and transmits the vent valve opening curve to the automatic control device 33 using the communication cable 34. The vent valve controller 32 is an actuator of the vent valve opening control system of the natural gas vent system. It is installed on the vent valve of the natural gas vent system and is connected to the automatic control device 33 through the communication cable 34. During the venting process, the vent valve controller 42 adjusts the vent valve opening degree according to the instruction of the automatic control device 43. The automatic control device 43 is the core of the vent valve opening control system of the natural gas vent system. During the venting process, the automatic control device 43 forms a control instruction of the vent valve controller 42 based on the vent valve opening curve of the natural gas vent system to control the vent valve controller 42 to adjust the opening degree of the vent valve, so that the vent valve opening degree is controlled according to the vent valve opening control method of the natural gas vent system described in each method embodiment.

[0198] Furthermore, the vent valve controller 32 is further used to feed back the vent valve opening information to the automatic control device 33 ; the automatic control device 33 is further used to receive and store the vent valve actual opening information fed back by the vent valve controller 32 .

[0199] Furthermore, the natural gas venting system vent valve opening control system is further equipped with pressure sensors, temperature sensors, flow meters and other equipment to collect pressure, temperature and flow data at the vent riser outlet; the automatic control device 33 is further used to receive and store data collected by pressure sensors, temperature sensors, flow meters and other equipment; the vent valve opening curve determination device 31 is further used to compare these data with simulation data, and based on the analysis of errors, continuously improve the established natural gas venting system vent valve opening curve determination method.

[0200] Furthermore, the natural gas venting system venting valve opening control system also includes a power supply for providing power guarantee to devices requiring power supply in the natural gas venting system venting valve opening control system.

[0201] Example 1

[0202] A method for controlling the opening of a vent valve in a natural gas vent system, the method being used to control Figure 4 The figure shows the opening process of the vent valve in the single-pipe section single-side vent system.

[0203] The basic parameters of the trunk and vent system pipelines are shown in Table 1, the gas composition is shown in Table 2, the initial pressure and initial temperature of the gas before the trunk section is vented are 2MPa and 286K respectively, the total heat transfer coefficient of the pipeline is 1.1W / (m2·K), the ambient temperature is the atmospheric temperature, assumed to be 278K, and the relationship between the vent valve flow coefficient and the opening is shown in Table 3.

[0204] Table 1 Main and vent system pipeline parameters

[0205] Vent mains Vent pipeline Vent riser Length(m) 8000 6 20 Pipe diameter(mm) 660 200 200 Wall thickness(mm) 10.3 7.5 7.5 Roughness(mm) 0.01 0.46 0.46

[0206] Table 2 Composition of natural gas from vented air source

[0207] Natural gas composition Mole fraction (%) Methane (C1) 97.5 Ethane (C2) 0.2 Propane (C3) 0.2 <![CDATA[Nitrogen (N2)]]> 1.6 <![CDATA[Carbon dioxide (CO2)]]> 0.5

[0208] Table 3 Relationship between valve flow coefficient and opening

[0209] Opening 100 90 80 70 60 50 40 30 20 10 5 Flow coefficient K_V 1000 760 500 350 220 150 110 80 40 20 10

[0210] The method includes:

[0211] 1. Determine the opening of the vent valve at each time step; Figure 5 As shown, it is specifically implemented in the following way:

[0212] 1.1. Construct a dynamic simulation model of the venting process; determine the opening of the venting valve at the initial moment; determine the Mach number of the venting standpipe outlet gas and the sound pressure level of the venting observation point in the first time step;

[0213] Specifically, in the dynamic simulation model of the venting process constructed in this embodiment,

[0214] 1) The simulation model is:

[0215] The basic differential equation for isothermal steady-state flow in the gas pipeline section is:

[0216] The continuity equation, momentum equation, and energy equation are:

[0217]

[0218]

[0219]

[0220] Where ρ is the gas density, kg / m 3 ; τ is the microelement time, s; A is the flow area of ​​the pipe section, m 2 ; M is the gas mass flow rate in the pipe section, kg / s; x is the microelement distance, m; P is the gas pressure, Pa; d is the inner diameter of the pipe section, m; λ is the friction coefficient, which can be calculated according to the Colebrook formula; h is the enthalpy of the gas, J / kg; s is the altitude, m; g is the acceleration of gravity, m / s 2 ; K is the total heat transfer coefficient, W / (m 2 ·K); T is the gas temperature, K; T0 is the ambient temperature, K;

[0221] 2) The boundary conditions are:

[0222] The boundary condition of the riser outlet is: first use the outlet pressure equal to the atmospheric pressure as the boundary condition. If the calculated outlet velocity is less than or equal to the local sound velocity, it means that the pressure boundary condition is reasonable for the current time step; otherwise, switch the outlet boundary condition to the outlet velocity equal to the local sound velocity.

[0223] The boundary conditions at the closed end of the gas transmission trunk line are: the mass flow rate at the closed end is 0; the gas state change at the closed end is a polymorphic process, and the polymorphic process index n can be determined based on the initial conditions and the final conditions (the final temperature is equal to the ambient temperature, and the final pressure is equal to the atmospheric pressure). The calculation formula is:

[0224] Where, T ini and T env are respectively the initial gas temperature and the ambient temperature before the trunk line is vented, K; P ini and P env are the initial gas pressure and atmospheric pressure before the trunk line is vented, Pa; n is the polytropic process index;

[0225] The boundary conditions at the vent valve are: satisfying the pressure drop formula, temperature drop formula and mass flow balance formula, as shown below:

[0226]

[0227]

[0228] M in -M out =0

[0229] Among them, P in and P out Respectively represent the gas pressure at the inlet and outlet of the resistance element, Pa; K v is the valve flow coefficient; ρ in and ρ out Respectively represent the gas density at the inlet and outlet of the resistance element, kg / m 3 ;Q in and Q out Respectively represent the actual gas volume flow rate at the inlet and outlet of the resistance element, m 3 / s;T in and T out Respectively represent the inlet and outlet gas temperatures of the resistance element, K; M in and M out Respectively represent the gas mass flow rate at the inlet and outlet of the resistance element, kg / s; D in and D out Respectively represent the gas JT effect coefficient at the inlet and outlet of the resistance element, K / MPa;

[0230] Specifically, in this embodiment, the opening degree of the vent valve at the initial moment is 50%;

[0231] Specifically, the implicit central difference algorithm is used to discretely solve the established dynamic simulation model of the venting process of the natural gas transmission pipeline, and the flow rate and density of the gas at the outlet of the venting riser in the first time step are determined; the mass flow rate and temperature of the gas at the outlet of the venting riser are obtained; the Mach number of the gas at the outlet of the venting riser is determined based on the flow rate of the gas at the outlet of the venting riser; the sound pressure level of the venting observation point is determined based on the flow rate, mass flow rate, density and temperature of the gas at the outlet of the venting riser; wherein the sound pressure level of the venting observation point is determined by the following formula:

[0232] W a =ηW m

[0233]

[0234] L w =10log 10 W a +120

[0235] L p =L w +DI-10log 10 (4πr 2 )

[0236] Among them, when the outlet gas of the venting riser is subsonic flow, When the gas at the outlet of the venting riser is at the critical sound velocity, it is determined based on the relationship between the acoustic efficiency and the sound pressure ratio of the noise generated by supercritical flow (i.e., choked flow), see Figure 2 ;

[0237] Where Wa is the total sound power, in W; Wm is the mechanical flow power, in W; η is the acoustic efficiency, in dimensionless units; U is the flow rate of the gas at the venting riser outlet, in m / s; m is the mass flow rate of the gas at the venting riser outlet, in kg / s; ρ is the density of the gas at the venting riser outlet, in kg / m3; ρ0 is the atmospheric density, in kg / m3; T is the temperature of the gas at the venting riser outlet, in K; T0 is the atmospheric temperature, in K; Ka is the acoustic power coefficient , taking the value as 5×10-5; Ma is the Mach number of the gas at the vent standpipe outlet, unit is dimensionless; Lw is the total sound power level of the airflow at the vent standpipe outlet, unit is dB; Lp is the sound pressure level at the vent observation point, unit is dB; DI is the directivity index, unit is dB, usually the subsonic flow takes the value of -6 (Mach number less than 1 is subsonic flow), the critical sound speed takes the value of -1 (Mach number ≥1 is critical sound speed); r is the distance from the vent observation point to the vent standpipe outlet, unit is m, taking 50m.

[0238] 1.2. Determine whether the Mach number of the gas at the outlet of the venting riser is less than 0.8 and the sound pressure level at the venting observation point is less than 80 dB at the current time step; if so, execute step 1.3; if not, execute step 1.4.

[0239] 1.3. Determine the valve adjustment amplitude value. The opening of the vent valve is the current opening plus the valve adjustment amplitude value.

[0240] Specifically, the process of determining the valve adjustment amplitude value is as follows: Figure 6 As shown, including:

[0241] 1.3.1. Determine whether the sequence number of the current time step is greater than 10; if not, execute step 1.3.2; if yes, execute step 1.3.2;

[0242] 1.3.2. The valve adjustment amplitude is equal to 0.5% (the opening when fully open is 100%);

[0243] 1.3.3. Determine the first valve adjustment amplitude value Value_tf; wherein the first valve adjustment amplitude value is based on the absolute value of the rate of change of the sound pressure level at the venting observation point and the absolute value of the rate of change of the Mach number of the gas at the standpipe outlet, and is determined by the following formula:

[0244] Value_tf=a×(k1+k2)+b

[0245] Where Value_tf is the valve amplitude value; k1 is the absolute value of the rate of change of the sound pressure level at the venting observation point; k2 is the absolute value of the rate of change of the Mach number at the standpipe outlet; a is the coefficient, which is 1000; b is the coefficient, which is 0.5.

[0246] 1.3.4. Determine whether the first valve adjustment amplitude value is greater than 5%; if so, execute step 1.3.5; if not, execute step 1.3.6;

[0247] Step 1.3.5, the valve adjustment amplitude value is equal to 5%;

[0248] Step 1.3.6, the valve adjustment amplitude value is equal to the first rated valve adjustment amplitude value.

[0249] 1.4. The opening of the vent valve remains at the current opening.

[0250] 1.5. Determine whether the opening of the vent valve is greater than 100%; if so, proceed to step 1.6; if not, proceed to step 1.7.

[0251] 1.6. Determine that the opening of the vent valve at the current time step is 100%.

[0252] 1.7. Determine the opening of the vent valve at the current time step as the opening of the vent valve at this time.

[0253] 1.8. Enter the next time step to determine the opening of the vent valve;

[0254] Specifically, the Mach number of the gas at the vent riser outlet in the first time step and the sound pressure level of the venting observation point are determined in the same manner as step 1.1, and the flow rate and density of the gas at the vent riser outlet in the next time step are determined in the same manner; and steps 1.2 to 1.7 are repeated to determine the opening of the vent valve in the next time step until the opening of the vent valve at the end of venting is determined; wherein, the end of venting is when the average pressure of the vented pipe section is less than 0.01MPa (gauge pressure).

[0255] 2. According to the determined opening of the vent valve at each time step, the opening of the vent valve corresponding to different venting times is obtained, thereby obtaining the vent valve opening curve;

[0256] In this embodiment, the vent valve opening curve is determined as follows: Figure 7 As shown in the figure, the valve adjustment amplitude value at each venting time is as follows Figure 8 shown.

[0257] 3. Control the opening of the vent valve of the natural gas vent system to quickly open it to the valve opening at the initial moment, and then control the opening of the vent valve of the natural gas vent system according to the vent valve opening curve of the natural gas vent system.

[0258] Comparative Example 1

[0259] The vent valve in Example 1 was developed and controlled in a 30-min linear full-open manner. The vent valve opening curve is as follows: Figure 7 As shown in the figure, the calculated valve adjustment amplitude value at each venting time is as follows Figure 8 shown.

[0260] Comparative Example 2

[0261] The vent valve in Example 1 was developed and controlled in a manner of linearly opening from 30 minutes to 60%. The vent valve opening curve is as follows: Figure 7 As shown in the figure, the calculated valve adjustment amplitude value at each venting time is as follows Figure 8 shown.

[0262] The vent valve is controlled according to the vent valve opening control method of the natural gas vent system provided in Example 1, the vent valve is controlled according to the vent valve opening control method of the natural gas vent system provided in Comparative Example 1, and the vent valve is controlled according to the vent valve opening control method of the natural gas vent system provided in Comparative Example 2. The flow rate, Mach number, sound pressure level, and mass flow rate of the riser outlet gas at each venting time are as follows: Fig. 9 , Fig.10 , Fig.11 , Fig.12 As shown in the figure, the vented main line pressure at each venting time is as follows: Fig.13 shown.

[0263] Depend on Figure 9-13 It can be seen that the vent valve opening control method of the natural gas vent system provided by the present invention can achieve a relatively large and stable vent flow rate when the noise meets the specified requirements during the venting operation, and complete the venting operation quickly. Compared with the 30-minute linear full opening method or the 30-minute linear opening to 60% method, the effect is better.

[0264] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for determining a vent valve opening curve of a natural gas vent system, wherein: The method includes: 1) Determine the opening of the vent valve at the initial moment, the Mach number of the vent riser outlet gas and the sound pressure level of the vent observation point; obtain the step length of each time step; wherein the Mach number of the vent riser outlet gas and the sound pressure level of the vent observation point at the initial moment are used as the Mach number of the vent riser outlet gas and the sound pressure level of the vent observation point in the first time step; 2) judging whether the Mach number of the gas at the outlet of the venting riser is less than the rated Mach number and the sound pressure level at the venting observation point is less than the rated sound pressure level at the current time step; If it is satisfied, the valve adjustment amplitude value is determined, and the opening of the vent valve is the current opening plus the valve adjustment amplitude value; If not satisfied, the opening of the vent valve remains at the current opening; 3) determining whether the opening of the vent valve obtained in step 2) is greater than 100%; If yes, then determine that the opening of the vent valve at the current time step is 100%; If not, then determine the opening of the vent valve at the current time step to be the opening of the vent valve obtained in step 2); 4) obtaining the Mach number of the gas at the outlet of the venting standpipe and the sound pressure level at the venting observation point at the next time step, and repeating steps 2) to 3) to determine the opening of the venting valve at the next time step until the opening of the venting valve at the end of the venting is determined; 5) According to the determined opening of the vent valve at each time step, the opening of the vent valve corresponding to different venting times is obtained, thereby obtaining the vent valve opening curve; Among them, determining the valve adjustment amplitude value includes: When the sequence number of the current time step is greater than the rated time step number, the valve adjustment amplitude value is determined based on the absolute value of the rate of change of the sound pressure level at the venting observation point and the absolute value of the rate of change of the Mach number of the gas at the standpipe outlet; When the sequence number of the current time step is less than or equal to the rated time step number, the valve adjustment amplitude value is equal to the second rated valve adjustment amplitude value; The step of determining the valve adjustment amplitude value based on the absolute value of the rate of change of the sound pressure level at the venting observation point and the absolute value of the rate of change of the Mach number of the gas at the standpipe outlet includes: Determine the first valve adjustment amplitude value according to the absolute value of the rate of change of the sound pressure level at the venting observation point and the absolute value of the rate of change of the Mach number of the gas at the standpipe outlet; Determine whether the first valve adjustment amplitude value is greater than the first rated valve adjustment amplitude value; If it is satisfied, the valve adjustment amplitude value is equal to the first rated valve adjustment amplitude value; If not, the valve adjustment amplitude value is equal to the first valve adjustment amplitude value; The first valve adjustment amplitude value is determined according to the following formula: Value_tf=a×(k1+k2)+b Wherein, Value_tf is the amplitude value of the valve adjustment, %; k1 is the absolute value of the rate of change of the sound pressure level at the venting observation point, dimensionless; k2 is the absolute value of the rate of change of the Mach number at the standpipe outlet, dimensionless; a is the coefficient, ranging from 500 to 1000; b is the coefficient, ranging from 0.1 to 0.5; Among them, the opening degree when fully open is 100%, and the first rated valve adjustment amplitude value can be in the range of 0.5%-5% Wherein, taking the fully open opening as 100%, the available value range of the second rated valve adjustment amplitude value is 0.1%-0.5%.

2. According to the method of claim 1, the absolute value of the rate of change of the sound pressure level is determined by the following formula: Where k1 is the absolute value of the rate of change of the sound pressure level at the emptying observation point, dimensionless; Lp1 and Lp2 are the sound pressure levels at the emptying observation point at the current time step and the previous time step, respectively, dB; Δτ is the time step, min.

3. According to the method of claim 1, the absolute value of the rate of change of the Mach number is determined by the following formula: Where k2 is the absolute value of the rate of change of the Mach number of the gas at the standpipe outlet, dimensionless; Ma1 and Ma2 are the Mach numbers of the gas at the standpipe outlet in the current time step and the previous time step, dimensionless; Δτ is the time step, min.

4. The method according to claim 1, wherein: The steps for obtaining the Mach number of the gas at the outlet of the venting standpipe and the sound pressure level at the venting observation point include: Obtain the flow rate, mass flow, density and temperature of the gas at the outlet of the vent riser; Determine the Mach number of the gas at the venting standpipe outlet based on the flow rate of the gas at the venting standpipe outlet; The sound pressure level at the venting observation point is determined based on the flow velocity, mass flow rate, density, temperature of the gas at the venting riser outlet and the distance from the venting observation point to the venting riser outlet.

5. The method according to claim 1, wherein: The available value range of rated sound pressure level is 70-80dB; The available range of rated Mach number is 0.7-0.

8.

6. The method according to claim 1, wherein: The valve opening at the initial moment is 30%-50%; The available value range of each time step is 30-120s.

7. A method for controlling the opening of a vent valve in a natural gas vent system, wherein: The method includes: The opening control of the vent valve of the natural gas vent system is performed according to the vent valve opening curve of the natural gas vent system determined by the method for determining the vent valve opening curve of the natural gas vent system according to any one of claims 1 to 6.

8. The method according to claim 7, wherein: The method further comprises: According to the natural gas venting system venting valve opening curve determined by the natural gas venting system venting valve opening curve determination method according to any one of claims 1 to 6, the natural gas venting system venting valve opening control is performed, and the valve opening of the natural gas venting system venting valve is first controlled to open to the valve opening degree at the initial moment.

9. A vent valve opening control system for a natural gas vent system, the system comprising: Vent valve opening curve determining device: used to implement the method for determining the vent valve opening curve of a natural gas vent system as described in any one of claims 1 to 6, and determine the vent valve opening curve of the natural gas vent system; Vent valve controller: The vent valve controller is the actuator of the vent control system, connected to the vent valve of the natural gas vent system, used to adjust the opening of the vent valve, and connected to the automatic control device through cables; Automatic control device: used to control the vent valve controller to adjust the vent valve opening, so as to realize the vent valve opening control method of the natural gas vent system according to claim 7 or 8; Communication cable: used to realize communication between the vent valve opening curve determination device and the automatic control device, and between the automatic control device and the vent valve controller.

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