CN113987696B - Numerical calculation method for critical flow release process of high-pressure gas container with break - Google Patents
Numerical calculation method for critical flow release process of high-pressure gas container with break Download PDFInfo
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Abstract
The invention discloses a calculation method of working medium state parameters in a container with a break, which can calculate the state of working medium in the container at any moment after the initial state of working medium in the container is calculated by the geometric dimension of the break when the container is broken and the working medium in the container is leaked, thereby providing effective theoretical calculation reference data for quantitative risk assessment after the high-pressure container is broken and leaked. The physical mechanism of gas-liquid two-phase critical flow leakage is fully considered in the method; the interphase action and interphase transfer, such as wall heat transfer, friction effect, interphase heat transfer mass transfer (condensation) and other processes, and uncoupled pressure vessel discharge and break critical flow leakage are fully considered, and the gas-liquid two-phase critical flow release mechanism of the pressure vessel is comprehensively described.
Description
Technical Field
The invention belongs to the technical field of container leakage safety, and particularly relates to a calculation method for working medium state parameters in a container with a break.
Background
In the fields of chemical industry and nuclear power, a pressure vessel for storing high-temperature high-pressure single-phase working medium (gas) is quite common equipment. In practical engineering application, when the pressure container walls are broken to generate penetrating cracks, high-temperature and high-pressure working media can leak to the atmosphere through the penetrating cracks on the container walls. The gas can be condensed, a gas-liquid two-phase critical flow is formed at the break, and the occurrence of the critical flow limits the discharge rate of working media in the break accident. In the pressure vessel decompression and discharge process, the temperature and pressure of working medium in the pressure vessel can be continuously reduced, even condensation can occur, and gas-liquid two phases are formed. The decompression and discharge process of the high-pressure gas container is closely related to the critical flow leakage process at the break of the pressure container and the critical flow discharge process of the high-pressure gas container, and in the two processes, the gas is condensed to form gas-liquid two phases. The simulated decompression discharging process and the critical flow discharging process are more complex. The method accurately calculates the decompression discharging process of the pressure vessel with the break and the critical flow leakage rate at the break of the pressure vessel, is a core for describing the critical flow discharging process of the high-pressure gas vessel, and is important for safety accident analysis in the fields of chemical industry and nuclear power.
The core of the numerical calculation of the release process of the high-pressure gas container with the break is the decompression discharge of working medium in the pressure container and the leakage of critical flow in the break. And calculating a pressure vessel decompression emission model and a break critical flow release model which need to be coupled, and describing the flow and transfer processes (heat transfer and mass transfer) of working media at the two positions of the pressure vessel and the break to obtain thermodynamic states (pressure, temperature, dryness and speed) of the working media at the two positions of the pressure vessel and the break and the wall surface temperature of the pressure vessel.
At present, the numerical calculation of the release process of the high-pressure gas container mainly has the following defects: 1. the existing related calculation programs all rely on empirical relation to calculate the leakage rate, and the physical mechanism of critical flow leakage at the break of the pressure vessel is not considered; 2. the existing calculation procedures of pressure reduction discharge and crack critical flow leakage of a related pressure vessel depend on a simplified model, and interphase acting force and interphase transmission, such as gas-liquid two-phase interphase acting force (drag force and virtual mass force), interphase heat and mass transfer (condensation), wall heat transfer, friction and inlet effect and the like are not fully considered. 3. The existing related calculation program does not couple the pressure vessel decompression discharge and the breach critical flow leakage, and does not fully describe the release mechanism of the pressure vessel with the breach.
Disclosure of Invention
According to the method, when the container is broken and the critical flow leakage occurs in the container, the state of the working medium in the container at any moment after the initial state of the working medium in the container is calculated when the leakage occurs can be calculated through the geometric dimension of the broken opening, so that effective theoretical calculation reference data are provided for quantitative risk assessment after the broken opening leakage occurs in the high-pressure container.
In order to realize the technical content, the invention is realized by adopting the following technical scheme:
A numerical calculation method for a critical flow release process of a high-pressure gas container with a break is realized by the following steps:
S1: initial condition setting, including setting a time step deltat and a space step deltaz; obtaining geometric parameters of a container, and obtaining a volume V, a diameter D and a height H; obtaining geometric parameters of the break, including the width W of the break flow channel, the height COD of the break flow channel and the length l of the flow channel; obtaining initial calculation thermodynamic parameters of working medium when the container is just beginning to generate break leakage, including initial pressure of working medium Initial dryness/>, working substanceWorking medium initial temperature/>
S2: setting an initial critical mass flow rate;
S3: determining the working medium state at the inlet of the break;
s4: calculating two-phase flow parameters in the break;
S5: determining a critical section;
s6: calculating the pressure of working medium in the container;
S7: calculating the heat exchange amount in the container;
s8: calculating a system temperature of the container;
S9: and (2) circulating the steps S2-S8 until the pressure in the container and the ambient pressure reach balance, and ending calculation.
Compared with the prior art, the invention has the following technical advantages:
1. The method fully considers the physical mechanism of gas-liquid two-phase critical flow leakage at the break of the pressure vessel;
2. The inter-phase acting force and inter-phase transmission, such as gas-liquid two-phase acting force (drag force and virtual mass force), inter-phase heat transfer and mass transfer (condensation), wall heat transfer, friction and inlet effect, and the like are fully considered.
3. The invention fully considers the pressure vessel decompression discharge and the breach critical flow leakage process, and comprehensively explains the gas-liquid two-phase critical flow release mechanism of the pressure vessel with the breach.
Drawings
FIG. 1 is a flow chart of a calculation method of the present invention;
FIG. 2 is a schematic diagram of the present invention;
FIG. 3 illustrates an example of verification of the effect of the control according to an embodiment of the present invention.
Detailed Description
The invention has the whole technical conception that: the core idea of the numerical calculation of the release process of the high-pressure gas container with the break is to calculate the numerical values of the decompression and discharge process of the working medium in the pressure container and the critical flow leakage process of the working medium in the break. The integral calculation thought comprises a pressure vessel decompression emission model and a break critical flow leakage model which are coupled, namely, the flow and transfer processes (heat transfer and mass transfer) of working media at the two positions of the pressure vessel and the break are described, and thermodynamic states (pressure, temperature and dryness) of the working media at the two positions of the pressure vessel and the break are obtained, and the release rate at the break and the wall surface temperature of the pressure vessel are obtained. The calculation method is used for analyzing the thermodynamic parameter change of the working medium in the pressure vessel when the wall surface of the vessel has penetrability cracks in the high-pressure gas pressure vessel, the release rate of the working medium, the thermodynamic state of the working medium at the break outlet and the wall surface temperature of the pressure vessel. The working medium related to the calculation method is saturated and overheated single-phase gas, and in the release process, the single-phase gas is likely to be condensed at the pressure vessel and the break to form gas-liquid two phases.
The following describes the invention in detail with reference to the drawings.
Referring to fig. 1, the invention discloses a numerical calculation method for a critical flow release process of a high-pressure gas container with a break, which is realized by the following steps:
s1: initial condition setting, including setting time step and space step; obtaining geometric parameters of a container, and obtaining a volume V, a diameter D and a height H; obtaining geometric parameters of the break, including the width W of the break flow channel, the height COD of the break flow channel and the length l of the flow channel; acquiring initial calculation thermodynamic parameters of working medium when the container is just started to generate crack leakage, wherein the initial thermodynamic parameters comprise initial pressure of the working medium, initial dryness of the working medium and initial temperature of the working medium;
S2: setting an initial critical mass flow rate;
S3: determining the working medium state at the inlet of the break;
s4: calculating two-phase flow parameters in the break;
S5: determining a critical section;
s6: calculating the pressure of working medium in the container;
S7: calculating the heat exchange amount in the container;
s8: calculating a system temperature of the container;
S9: and (2) circulating the steps S2-S8 until the pressure in the container and the ambient pressure reach balance, and ending calculation.
Wherein, the time discrete Δt in step S1 is calculated by the pressure vessel depressurizing emission model. The pressure vessel depressurization model needs to take three factors into consideration: in the decompression discharging process, the condensing of single-phase steam, the discharging speed of working medium in the pressure vessel and the heat conduction process between the working medium and the wall surface of the vessel are realized. The pressure vessel depressurization discharge process is a transient process, and therefore, a time discretization of the calculation process is required. The discrete thought of the pressure vessel discharge process is as follows, i.e. the calculation process is divided into I time steps, and the thermodynamic state of the working medium in the vessel is assumed to be kept unchanged in one time step, and in this time step, the upstream pressure vessel discharge calculation model provides the same initial conditions for the critical flow discharge process calculation at the break.
The spatial dispersion deltaz is subjected to numerical value presetting through critical flow release simulation at the break. The critical flow release process at the break needs to take four factors into consideration: thermodynamic parameters of working medium at the break entrance, condensation of working medium in the critical flow leakage process, wall heat transfer and determination of critical section. The working medium flows in at the opening entrance, reaches a critical state at the opening exit, and then diffuses to the outside. Assuming a flow channel length L and assuming a one-dimensional flow, the flow channel is discretized into spatially equally long J sections, with calculations being performed in a stepwise manner from the J-th section to the j+1 section.
And step S3, determining the working medium state at the break entrance. Working medium in the container leaks outwards through the break, and has inlet resistance loss when entering the break, wherein a pressure P calculation formula after the inlet resistance loss is as follows:
the P calculated from equation (1) is known and other state parameters required for subsequent calculations can be solved according to the methods presently disclosed.
Wherein,
Δp e —the loss of inlet resistance of working medium from the container into the break, pa;
c, an inlet resistance loss coefficient can be obtained by looking up a table according to the shape of the break;
-calculating the critical mass flow rate for the J-th time step, kg/(m 2 S), the critical mass flow rate for the first calculation being determined by step S1;
ρ e -density of working substance at break in kg/m 3, value equal to working substance density in container
P-the pressure of the working medium after entering the break, pa;
p J -internal pressure of the J-th time step after the container is broken and leaked, pa;
Step S4, calculating two-phase flow parameters in the break, and to obtain the critical flow leakage flow of the two phases, making two assumptions, namely considering the flow of the working medium to be one-dimensional, and considering the pressure and the speed of the gas-liquid two phases on the flow section to be equal and uniformly distributed, wherein a critical two-phase flow leakage equation in the break can be obtained based on the two assumptions:
solving equation (2) to obtain the pressure P n and the flow velocity of the working medium in the discretized nth section flow channel And temperature/>
Wherein,
The mixed density of working media in the N-1 th section of flow channels in the N sections of equal length flow channels in a space discretization mode, kg/m 3, the value of which can be expressed by the density/>, of dry saturated steam of the N-1 section of flow channelsDensity of saturated water/>And dryness/>Calculating to obtain;
p n-1, the pressure of working medium in the N-1 th section of flow channel in the N sections of equal length flow channels with space discretization, pa, the pressure P 1 in the 1 st section of flow channel is the pressure P obtained in the step S6;
p n, the pressure of working medium in the nth section of flow passage in the N sections of equal-length flow passages with space discretization, pa;
-partial differentiation of speed of working medium to pressure under isothermal condition in N-1 th section of flow channel in N sections of equal length flow channels of space discretization;
T n-1, namely the temperature of the working medium in the N-1 th section of flow passage in the N sections of equal length flow passages with the space discretization, and K, wherein the value of the temperature can be obtained by the pressure P n-1 of the working medium in the N-1 th section of flow passage;
the temperature K of the working medium in the nth section of flow passage in the N sections of equal-length flow passages with discretized space; /(I) Partial differentiation of speed of working medium to temperature under isobaric condition in the N-1 th section of flow channel in the N sections of equal length flow channels of the space discretization;
The values of J/kg, which are the mixed enthalpy of the working medium in the N-1 th section of flow passage in the N sections of equal length flow passages with the discretized space, can be obtained by the pressure P n-1 and the temperature/>, of the working medium in the N-th section of flow passage Determining;
Partial differentiation of the mixing enthalpy of the working medium to the pressure under the isothermal condition in the N-1 th section of flow passage in the N sections of equal-length flow passages with the discretization in space;
c p -constant pressure specific heat capacity of mixed working medium, J/(kg.K);
-the along-the-way rate of change of the fracture cross section, m;
ρ—density of gas-liquid mixture in the container, kg/m 3;
phi m, namely heat exchange quantity J of mixed working medium in the container;
Phi e, namely heat exchange quantity J of working medium at the container opening;
-enthalpy of saturated liquid corresponding to pressure P n-1 in the N-1 th section of flow channel in the N sections of equal length flow channels in a space discretization mode, J/kg;
The speed, m/s, of the working medium in the N-1 th section of flow passage in the N sections of equal-length flow passages with the space discretization can be calculated by the following formula:
Wherein,
-Calculating the critical mass flow rate for the J-th time step, kg/(m 2 S), the critical mass flow rate for the first calculation being determined by step S1.
Step S5 determines a critical section, and when determinant det (a) =0 of coefficient matrix a, the breach leakage reaches a critical flow, which is improved by the present invention as follows:
And under each time step, after each step calculation of one space step, judging once, and if the calculation result meets the formula (4) (4), considering that the working medium in the break reaches the critical value in the ith section of flow passage under the assumed critical mass flow rate G c. In practice, however, for a breach flow path of a high pressure vessel, the actual critical flow occurs at the exit of the breach flow path; comparing the critical flow occurrence position determined by the above process with the actual critical flow occurrence position, if the critical flow occurrence position is smaller than the actual critical flow occurrence position, reducing the set value of the critical mass flow rate, and if the critical flow occurrence position is larger than the actual critical flow occurrence position, increasing the set value of the mass flow rate, so that the critical mass flow rate is further corrected:
Wherein:
-critical mass flow rate after correction, kg/(m 2 s);
-critical mass flow rate before correction, kg/(m 2 s);
correction value of Δg c——Gc(k), kg/(m 2 ·s);
-critical flow occurrence position, m;
L is the length of the break runner, m;
Will result in After which it is taken as new/>, step S2The calculations of steps S3 to S5 are repeated until the value is equal to the value of/>On the premise that the actual critical flow occurrence position is equal to the calculated critical flow occurrence position, the calculation in step S6 is entered, and the/>I.e. the critical mass flow rate/>, which is the critical mass flow rate obtained when the critical occurs in the breach flow passageThis/>As well as the initial value calculated for the next time step.
Step S6: calculating the pressure of working medium in the container, and for the container with a break, calculating the pressure of the working medium in the container by using the pressure calculation model as follows:
Wherein:
p J-1 -internal pressure of the J-1 th time step after the container is broken and leaked, pa, and the pressure calculated for the first time is determined by the step S1;
-density of working medium in the container at the J-th time step after the container is broken and leaked, kg/m 3;
v g -the specific volume of dry saturated steam corresponding to the pressure P J in the working medium in the container, m 3/kg, can be calculated from the pressure P J-1;
v l -the specific volume of saturated liquid corresponding to the pressure P J in the working medium in the container, m 3/kg, can be calculated by the pressure P J;
-the quality of the working medium of the J-th time step after the container is broken and leaked, and the quality calculated for the first time is determined by the step S1;
p J -internal pressure of the J-th time step after the container is broken and leaked, pa;
-calculating the critical mass flow rate for the J-th time step, kg/(m 2 S), the critical mass flow rate for the first calculation being determined by step S1;
A e -crack entrance area, m 2, the value of which is determined by step S1;
v vol -container body volume, m 3, the value of which is determined by step S1;
-differentiating the pressure in the container by the density of the working medium in the container; the specific volumes of saturated liquid and dry saturated steam under the corresponding pressure of P J-1 in the formula can be calculated by the known working medium pressure P J-1, and the related calculation method can be realized by following the prior art.
Step S7, calculating the heat exchange amount in the container: the heat exchange of the working medium in the container is divided into heat conduction of the container body and heat exchange between the inner wall surface of the container and the working medium in the container, and the relative speed between the working medium in the container and the inner wall surface of the container is approximately negligible, so that the heat exchange between the inner wall surface of the container and the working medium in the container is considered to be performed by heat conduction, and a heat exchange model of the working medium in the container can be obtained:
Wherein:
Q vg -heat exchange quantity, J;
t w -wall temperature, K;
t f, the temperature of the gas-liquid mixed working medium, K;
R v -thermal resistance of the wall surface of the container, K.W -1;
R f -gas-liquid mixed working medium heat conduction resistance, K.W -1;
Δt, namely the set time step, s;
D-diameter of container, m;
delta-thickness of container, m;
k v -coefficient of thermal conductivity of the vessel, W/(mK);
H-the height of the vessel, m;
a f, the contact area of the gas-liquid mixed working medium and the fluid, m 2;
K f -the heat conductivity coefficient of the gas-liquid mixed working medium, W/(m.K).
S8, calculating the system temperature of the container, wherein the system temperature calculation of the container comprises three parts, and the first part is the gas phase working medium temperature in the container; the second part is the temperature of liquid phase working medium in the container; the third part is the container body temperature.
Wherein the first part: the temperature of the gas phase working medium in the container is determined by firstly requiring the enthalpy change of the working medium, and the calculation formula is as follows:
The enthalpy value of the working medium can be obtained after the enthalpy change of the working medium in the container is determined:
hJ＝hJ-1+Δh(9)
the relationship among the superheat degree, enthalpy change and constant pressure specific heat capacity of the gas phase working medium is as follows:
The calculation formula of the superheat degree of the gas phase working medium can be obtained by the combined type (8), (9) and (10):
If the enthalpy of the working medium is smaller than or equal to the enthalpy of the dry saturated steam state, the temperature T g of the gas-phase working medium in the container still takes the saturation temperature corresponding to the pressure P J; otherwise, the superheat degree needs to be considered, and the superheat degree is calculated by the following formula:
Tg＝Tgsat+ΔTg(12)
a second part: the temperature T l of the liquid phase working medium in the container is equal to the saturation temperature corresponding to the known pressure P J;
Third section: the container body temperature is calculated by the following formula:
in the method, in the process of the invention,
Δh—enthalpy change of working medium in the vessel, J/kg;
Q vg -the heat exchange quantity of the working medium in the container with the outside through the container is obtained by the step S4;
v vol -container body volume, m 3, the value of which is determined by step S1;
h J-1, namely J-1 time step working medium enthalpy value after the container is broken and leaked, J/kg;
Δρ g —gas phase Density for the J-th time step after breach leakage of the vessel Gas phase Density by the J-1 th time step/>The difference between kg/m 3,/>And/>Can be calculated from P J and P J-1;
-calculating the critical mass flow rate for the J-th time step, kg/(m 2 S), the critical mass flow rate for the first calculation being determined by step S2;
a e -crack entrance area, m 2;
-density of working medium in the container, kg/m 3;
h J, namely working medium enthalpy value J/kg of the J th time step after the container is broken and leaked;
DeltaT g -the superheat degree of the gas phase working medium in the container, K;
h gsat -the enthalpy value of the corresponding dry saturated steam at the pressure P J in the vessel, J/kg, which value can be determined from P J;
c pg -constant pressure specific heat capacity of gas phase working medium in the container, J/(kg.K), the value of which can be obtained by P J;
T g -the temperature of the gas phase working medium in the container, K;
t l -the temperature of the gas phase working medium in the container, K;
T gsat -the corresponding saturation temperature under the pressure P J in the container, K, the value of which can be determined by P J;
-container body temperature at the J-th time step after container breach leakage, K, container body temperature at the time of initial calculation/> Taking the temperature of the working medium in the container, wherein the value of the temperature can be obtained by calculating the initial pressure of the working medium obtained in the step 1;
-the temperature, K, of the body of the container at the J-th time step after the container has been breached;
m v -the mass of the container body, kg;
c pv -constant pressure specific heat capacity of the container body, J/(kg. K);
Step S9: circulating the steps S2-S8 until the pressure in the container and the ambient pressure reach balance, ending calculation, and outputting the temperature T g of the gas-phase working medium, the temperature T l of the liquid-phase working medium, the working medium pressure P J and the dryness of the gas-phase working medium in the container at each time step Leakage flow/>Leakage flow/>
The calculation process of the break leakage under one time step from the step S2 to the step S8 comprises two parts of critical flow calculation of working media in the break and calculation of physical parameters in the container, after the calculation process from the step S2 to the step S8 is completed, the calculation process returns to the step S2 to enter the calculation of the next time step, the processes from the step 2 to the step 9 are repeatedly carried out, and the calculation is finished until the pressure in the container and the environmental pressure reach balance. At the same time, the temperature T g of the gas phase working medium, the temperature T l of the liquid phase working medium, the working medium pressure P J and the dryness of the internal phase working medium of the container under each time step are recorded and outputLeakage flow/>Wherein leakage flow/>Calculated according to the following formula:
Wherein,
-Leakage flow of fluid through the break at the J-th time step, kg/(s);
A e -crack entrance area, m 2, the value of which is determined by step S1;
A e -crack entrance area, m 2, the value of which is determined by step S1;
-ratio of the opening to the inlet/outlet area;
By/>, at the J-th time step The critical leakage mass flow rate obtained was repeatedly corrected for kg/(m 2 s).
The effect of the present invention will be described below with reference to specific calculation objects, by taking the pressure vessel with a break as shown in fig. 2 as an example, the temperature T g of the gas phase working medium, the temperature T l of the liquid phase working medium, the working medium pressure P J, and the dryness are calculated according to the calculation from step 1 to step 9Leakage flow/>
Fig. 3 shows the change condition of the temperature of the gas-liquid mixed working medium (namely, the fluid temperature) within the period of 0-65s after the container is broken and leaked, and according to the calculation result of the program shown in fig. 3, the calculation result and the experimental result are well matched, so that the accuracy and the effectiveness of the program are proved.
In order to check the reliability of the calculation result of the present invention, the calculation result of the numerical value of the present invention was compared with test data, and the comparison result is shown in fig. 3.
The practical working condition experiment verification conditions comprise crack parameters, working medium state parameters in a container, container geometric parameters and measurement parameters.
Crack parameters: the crack length l is 10mm, the crack inlet width W is 23.1mm, the crack outlet width W is 17.2mm, the crack flow channel inlet height COD is 0.16mm, the crack flow channel outlet height COD is 0.12mm,
Working medium state parameters in the container: the initial pressure is 3.2MPa, the temperature of the working medium is 3.2MPa, the corresponding saturation temperature is added with the superheat degree of 1K, and the dryness of the container is 1 (namely, full liquid phase) when the container just has break leakage;
Container geometry parameters: the volume is 3.1L, the material is stainless steel, the length is 160mm, the inner diameter of the container is 30mm, and the wall thickness is 10;
Measuring parameters: the temperature change in the container was measured during the period from the onset of breach leak to 65 s.
Program calculation parameter setting: setting crack parameters, working medium state parameters in the container, geometric parameters of the container and measurement parameters according to test working conditions, setting the space step length to be deltaz=l/100, and drawing the temperature of the working medium in the container for 0-65s after calculation.
The present invention may also be applied to any storage medium that is configured with computer readable instructions that, when executed by one or more processors, cause the one or more processors to perform the overall method for calculating a value of a critical flow discharge process for a breached high pressure gas container of the present invention.
From the above description of the embodiments, it will be clear to those skilled in the art that the above-described embodiment method may be implemented by means of software plus a necessary general hardware platform, but of course may also be implemented by means of hardware, but in many cases the former is a preferred embodiment. Based on this understanding, the technical solution of the present application may be embodied essentially or in a part contributing to the prior art in the form of a software product stored in a storage medium such as (ROM/RAM), comprising instructions for causing a terminal (which may be a mobile phone, a computer, a server or a network device, etc.) to perform the method according to the embodiments of the present application.
While the embodiments of the present application have been described above with reference to the drawings, the present application is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many modifications may be made thereto by those of ordinary skill in the art without departing from the spirit of the present application and the scope of the appended claims, which are to be accorded the full scope of the present application as defined by the following description and drawings, or by any equivalent structures or equivalent flow changes, or by direct or indirect application to other relevant technical fields.
The above embodiments are only for illustrating the present invention, not for limiting the present invention, and various changes and modifications may be made by one of ordinary skill in the relevant art without departing from the spirit and scope of the present invention, and therefore, all equivalent technical solutions are also within the scope of the present invention, and the scope of the present invention is defined by the claims.
Claims (6)
1. A numerical calculation method for a critical flow release process of a high-pressure gas container with a break is characterized by comprising the following steps of: the method is realized by the following steps:
S1: initial condition setting, including setting a time step deltat and a space step deltaz; obtaining geometric parameters of a container, and obtaining a volume V, a diameter D and a height H; obtaining geometric parameters of the break, including the width W of the break flow channel, the height COD of the break flow channel and the length l of the flow channel; obtaining initial calculation thermodynamic parameters of working medium when the container is just beginning to generate break leakage, including initial pressure of working medium Initial dryness/>, working substanceWorking medium initial temperature/>
S2: setting an initial critical mass flow rate;
S3: determining the working medium state at the inlet of the break;
S3, determining the working medium state at the break entrance, wherein the calculation formula of the pressure P after the resistance loss of the break entrance is as follows:
Wherein,
Δp e —the loss of inlet resistance of working medium from the container into the break, pa;
C-inlet drag loss coefficient;
-calculating the critical mass flow rate for the J-th time step, kg/(m 2 s);
ρ e —density of working medium when entering the break, kg/m 3;
p-the pressure of the working medium after entering the break, pa;
p J -internal pressure of the J-th time step after the container is broken and leaked, pa;
s4: calculating two-phase flow parameters in the break;
The S4: calculating two-phase flow parameters in the fracture, and constructing a critical two-phase flow leakage equation in the fracture: Solving the equation (2) to obtain the pressure P n, flow rate/>, of the working medium in the discretized nth section flow channel And temperature/>
Wherein,
-The mixing density of working media in the N-1 th section of flow channel in the N sections of equal length flow channels with discretized space is kg/m 3;
p n-1 -the pressure Pa of working medium in the N-1 th section of flow passage in the N sections of equal-length flow passages with space discretization;
p n, the pressure of working medium in the nth section of flow passage in the N sections of equal-length flow passages with space discretization, pa; -partial differentiation of speed of working medium to pressure under isothermal condition in N-1 th section of flow channel in N sections of equal length flow channels of space discretization;
t n-1 -the temperature of the working medium in the N-1 th section of the flow channel in the N sections of equal length flow channels with space discretization, K;
the temperature K of the working medium in the nth section of flow passage in the N sections of equal-length flow passages with discretized space;
Partial differentiation of speed of working medium to temperature under isobaric condition in the N-1 th section of flow channel in the N sections of equal length flow channels of the space discretization;
-mixing enthalpy of working medium in the N-1 th section of flow channel in the N sections of equal length flow channels in a space discretization mode, J/kg;
Partial differentiation of the mixing enthalpy of the working medium to the pressure under the isothermal condition in the N-1 th section of flow passage in the N sections of equal-length flow passages with the discretization in space;
c p -constant pressure specific heat capacity of mixed working medium, J/(kg.K);
-the along-the-way rate of change of the fracture cross section, m;
ρ—density of gas-liquid mixture in the container, kg/m 3;
Phi m, namely heat exchange quantity J of mixed working medium in the container;
Phi e, namely heat exchange quantity J of working medium at the container opening;
-enthalpy of saturated liquid corresponding to pressure P n-1 in the N-1 th section of flow channel in the N sections of equal length flow channels in a space discretization mode, J/kg;
The speed of working medium in the N-1 th section of flow channel in the N sections of equal length flow channels in a space discretization mode is m/s;
S5: determining a critical section;
S5: determining a critical section; judging critical conditions for each space step under each time step, if the critical conditions are met, considering that working media in the break reach a critical flow occurrence position under the critical mass flow rate, then comparing the critical flow occurrence position with the outlet position of the actual break flow channel, if the critical flow occurrence position is inconsistent with the outlet position of the actual break flow channel, correcting the critical flow rate, and repeating the steps S2 to S5 until the critical flow occurrence position is consistent with the outlet position of the actual break flow channel, wherein the critical mass flow rate of the critical flow occurrence position is the critical mass flow rate when the critical flow occurs in the break flow channel;
S6: calculating the pressure of working medium in the container; s6: calculating the pressure of working medium in a container, wherein a pressure calculation model of the working medium in the container is as follows:
Wherein:
P J-1 -internal pressure of J-1 time step after breach leakage of the container, pa;
-density of working medium in the container at the J-th time step after the container is broken and leaked, kg/m 3;
v g -the specific volume of dry saturated steam corresponding to the pressure P J in the working medium in the vessel, m 3/kg;
v l -the specific volume of saturated liquid corresponding to the pressure P J in the working medium in the container, m 3/kg;
-the quality of the working medium at the J-th time step after the container is broken and leaked;
p J -internal pressure of the J-th time step after the container is broken and leaked, pa;
-calculating the critical mass flow rate for the J-th time step, kg/(m 2 s);
a e -crack entrance area, m 2;
v vol -container body volume, m 3;
-differential of the density of the working medium in the container to the pressure in the container, P J-1 being the specific volume of saturated liquid and dry saturated vapor under pressure;
S7: calculating the heat exchange amount in the container;
the S7: calculating heat exchange quantity in the container by adopting a working medium heat exchange model in the container as follows:
Wherein:
Q vg -heat exchange quantity, J;
t w -wall temperature, K;
t f, the temperature of the gas-liquid mixed working medium, K;
R v -thermal resistance of the wall surface of the container, K.W -1;
R f -gas-liquid mixed working medium heat conduction resistance, K.W -1;
Δt-time step, s;
D-diameter of container, m;
delta-thickness of container, m;
k v -coefficient of thermal conductivity of the vessel, W/(mK);
H-the height of the vessel, m;
a f, the contact area of the gas-liquid mixed working medium and the fluid, m 2;
k f -the heat conductivity coefficient of the gas-liquid mixed working medium, W/(m.K);
s8: calculating a system temperature of the container;
S8: calculating the system temperature of the container, including calculating the gas phase working medium temperature T g, the liquid phase working medium temperature T l and the container body temperature
S9: and (2) circulating the steps S2-S8 until the pressure in the container and the ambient pressure reach balance, and ending calculation.
2. The method for calculating the critical flow release process value of the broken high-pressure gas container according to claim 1, wherein the method comprises the following steps: the critical judgment condition in the S5 is thatIf the critical judgment condition is met, the working medium in the break reaches the critical state in the ith section of flow channel under the critical mass flow rate; if the critical flow generation position is inconsistent with the outlet position of the actual breach flow path, the critical mass flow rate correction formula is as follows:
Wherein:
-critical mass flow rate after correction, kg/(m 2 s);
-critical mass flow rate before correction, kg/(m 2 s);
correction value of Δg c——Gc(k), kg/(m 2 ·s);
-critical flow occurrence position, m;
L-the length of the break runner, m.
3. The method for calculating the critical flow release process value of the broken high-pressure gas container according to claim 1, wherein the method comprises the following steps: when the temperature T g of the gas phase working medium in the container is calculated, if the enthalpy value of the working medium is smaller than or equal to the enthalpy value of the dry saturated steam state, the temperature T g of the gas phase working medium in the container still takes the saturation temperature corresponding to the pressure P J, and if the enthalpy value of the working medium is larger than the enthalpy value of the dry saturated steam state, T g＝Tgsat+ΔTg
Wherein T gsat is the corresponding saturation temperature, K, of the pressure P J in the container; delta T g is the superheat degree of the gas phase working medium in the container, K.
4. The method for calculating the critical flow release process value of the broken high-pressure gas container according to claim 1, wherein the method comprises the following steps: the temperature of the container bodyThe following formula is adopted for calculation:
in the method, in the process of the invention,
Q vg -the heat exchange quantity of working medium in the container with the outside through the container;
-the temperature, K, of the body of the container at the J-th time step after the container has been breached;
-the temperature, K, of the body of the container at the J-th time step after the container has been breached;
m v -the mass of the container body, kg;
c pv -constant pressure specific heat capacity of the vessel body, J/(kg.K).
5. The method for calculating the critical flow release process value of the broken high-pressure gas container according to claim 1, wherein the method comprises the following steps: the S9: circulating the steps S2-S8 until the pressure in the container and the ambient pressure reach balance, ending calculation, and outputting the temperature T g of the gas-phase working medium, the temperature T l of the liquid-phase working medium, the working medium pressure P J and the dryness of the gas-phase working medium in the container at each time stepLeakage flow/>Leakage flow/>
Wherein the leakage flow rateCalculated according to the following formula:
Wherein,
-Leakage flow of fluid through the break at the J-th time step, kg/(s);
a e -crack entrance area, m 2;
a e -crack entrance area, m 2;
-ratio of the opening to the inlet/outlet area;
By/>, at the J-th time step The critical leakage mass flow rate obtained was corrected for kg/(m 2 s).
6. A storage medium storing computer readable instructions which, when executed by one or more processors, cause the one or more processors to perform the method of calculating the critical flow discharge process value of a breached high pressure gas container as defined in any of claims 1-5.
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