CN113987696A - Method for calculating critical flow release process value of high-pressure gas container with crevasse - Google Patents

Method for calculating critical flow release process value of high-pressure gas container with crevasse Download PDF

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CN113987696A
CN113987696A CN202111112467.1A CN202111112467A CN113987696A CN 113987696 A CN113987696 A CN 113987696A CN 202111112467 A CN202111112467 A CN 202111112467A CN 113987696 A CN113987696 A CN 113987696A
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殷松涛
王海军
刘启航
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Xian Jiaotong University
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Abstract

The invention discloses a method for calculating the state parameters of working media in a container with a break, which can calculate the state of the working media in the container at any time through the geometric dimension of the break when the working media in the container leak when the container has the break and the working media in the container leak, and provides effective theoretical calculation reference data for the quantitative risk evaluation after the break leaks in a high-pressure container. The method fully considers the gas-liquid two-phase critical flow leakage physical mechanism; the releasing mechanism of the gas-liquid two-phase critical flow of the pressure container is comprehensively explained by fully considering the processes of interphase action and interphase transmission, such as wall surface heat transfer, friction effect, interphase heat and mass transfer (condensation) and the like, and the leakage of the discharging and breaking critical flow of the uncoupled pressure container.

Description

Method for calculating critical flow release process value of high-pressure gas container with crevasse
Technical Field
The invention belongs to the technical field of container leakage safety, and particularly relates to a method for calculating working medium state parameters in a container with a crevasse.
Background
In the fields of chemical engineering and nuclear power, a pressure container for storing high-temperature and high-pressure single-phase working media (gas) is very common equipment. In practical engineering application, when the pressure vessel walls are cracked to generate penetrating cracks, the high-temperature and high-pressure working medium can leak to the atmosphere side through the penetrating cracks on the vessel walls. The gas can be condensed to form gas-liquid two-phase critical flow at the break, and the occurrence of the critical flow limits the discharge rate of the working medium in the break accident. In the pressure vessel decompression discharge process, the temperature and the pressure of working medium in the pressure vessel can be continuously reduced, even condensation can occur, and gas-liquid two-phase is formed. The decompression and discharge process of the high-pressure gas container is closely related to the critical flow leakage process at the opening of the pressure container and the critical flow release process of the high-pressure gas container, and in the two processes, gas can be condensed to form a gas phase and a liquid phase. The simulated decompression discharge process and the critical flow leakage process are more complicated. The accurate calculation of the decompression discharge process of the pressure container with the break and the critical flow leakage rate of the pressure container at the break is the core for describing the critical flow release process of the high-pressure gas container, and is of great importance for safety accident analysis in the fields of chemical engineering and nuclear power.
The core of numerical calculation in the releasing 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-reducing discharge model and a crevasse critical flow release model which need to be coupled with the pressure container, describing the flowing and transferring processes (heat transfer and mass transfer) of working media at two positions of the pressure container and the crevasse, and obtaining the thermodynamic states (pressure, temperature, dryness and speed) of the working media at the two positions of the pressure container and the crevasse and the wall surface temperature of the pressure container.
The numerical calculation of the release process of the high-pressure gas container at present mainly has the following defects: 1. the existing related calculation programs all depend on empirical relations to calculate the leakage rate, and the physical mechanism of the critical flow leakage at the pressure container fracture is not considered; 2. the existing related pressure vessel decompression discharge and breach critical flow leakage calculation programs all depend on simplified models, and the interphase acting force and interphase transmission are not fully considered, such as gas-liquid two-phase interphase acting force (drag force and virtual mass force), interphase heat and mass transfer (condensation), wall surface heat transfer, friction, inlet effect and the like. 3. The existing related calculation procedures do not couple the pressure vessel decompression discharge and the breach critical flow leakage, and the release mechanism of the pressure vessel with the breach is not fully described.
Disclosure of Invention
Aiming at the problems, the invention provides a method for calculating the state parameters of the working medium in the container with the crevasse, when the container is crevasse and the working medium in the container generates critical flow leakage, the state of the working medium in the container at any time can be calculated by the initial state of the working medium in the container when leakage occurs through the geometrical size of the crevasse, and effective theoretical calculation reference data is provided for the quantitative evaluation of the risk after the crevasse leakage occurs in the high-pressure container.
In order to realize the technical content, the invention adopts the following technical scheme:
a numerical calculation method for critical flow release process of a high-pressure gas container with a break opening is realized by the following steps:
s1: setting initial conditions, including setting a time step length delta t and a space step length delta z; acquiring geometric parameters of the container, such as volume V, diameter D and height H; acquiring the geometric parameters of a crevasse, including the width W of a crevasse runner, the height COD of the crevasse runner and the length l of the runner; obtaining initial calculation thermodynamic parameters of the working medium when the container is just subjected to breach leakage, including the initial pressure of the working medium
Figure BDA0003274352270000021
Initial dryness of working medium
Figure BDA0003274352270000022
Initial temperature of working medium
Figure BDA0003274352270000023
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 breaking port;
s5: determining a critical section;
s6: calculating the pressure of the working medium in the container;
s7: calculating the heat exchange amount in the container;
s8: calculating a system temperature of the vessel;
s9: and circulating the steps S2-S8 until the pressure in the container is balanced with the ambient pressure, and finishing the calculation.
Compared with the prior art, the invention has the following technical beneficial effects:
1. the method fully considers the gas-liquid two-phase critical flow leakage physical mechanism at the pressure container break opening;
2. the interphase acting force and the interphase transmission are fully considered, 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, inlet effect and the like.
3. The invention fully considers the processes of pressure vessel decompression discharge and critical flow leakage of the break port, and comprehensively explains the gas-liquid two-phase critical flow release mechanism of the pressure vessel with the break port.
Drawings
FIG. 1 is a flow chart of a computing method of the present invention;
FIG. 2 is a schematic representation of an embodiment of the present invention;
FIG. 3 shows an example of the verification and comparison effect of the embodiment of the present invention.
Detailed Description
The overall technical concept of the invention is as follows: the core idea of numerical calculation of the release process of the high-pressure gas container with the crevasses is numerical calculation of a working medium decompression and discharge process in the pressure container and a working medium critical flow leakage process in the crevasses. The overall calculation idea comprises a coupling pressure container decompression discharge model and a crevasse critical flow leakage model, namely describing the flow and transfer process (heat transfer and mass transfer) of working media at two positions of the pressure container and the crevasse to obtain the thermodynamic states (pressure, temperature and dryness) of the working media at the two positions of the pressure container and the crevasse, the release rate at the crevasse and the wall surface temperature of the pressure container. The calculation method is used for analyzing the thermodynamic parameters of the working medium in the pressure container, the release rate of the working medium, the thermodynamic state of the working medium at a crevasse outlet and the wall temperature of the pressure container when the wall surface of the pressure container has a penetrating crack. The working medium related to the calculation method is saturated and overheated single-phase gas, and during the release process, the single-phase gas is likely to be condensed at the pressure container and the crevasses to form a gas-liquid two-phase.
The present invention will be described in more detail with reference to the accompanying drawings.
Referring to fig. 1, the invention discloses a numerical calculation method for critical flow release process of a high-pressure gas container with a break, which is realized by the following steps:
s1: setting initial conditions, including setting time step length and space step length; acquiring geometric parameters of the container, such as volume V, diameter D and height H; acquiring the geometric parameters of a crevasse, including the width W of a crevasse runner, the height COD of the crevasse runner and the length l of the runner; acquiring initial calculation thermodynamic parameters of a working medium when the container is just subjected to breach leakage, wherein the initial calculation thermodynamic parameters comprise the initial pressure of the working medium, the initial dryness of the working medium and the 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 breaking port;
s5: determining a critical section;
s6: calculating the pressure of the working medium in the container;
s7: calculating the heat exchange amount in the container;
s8: calculating a system temperature of the vessel;
s9: and circulating the steps S2-S8 until the pressure in the container is balanced with the ambient pressure, and finishing the calculation.
In step S1, the time dispersion Δ t is calculated by the pressure vessel decompression and discharge model. The pressure vessel decompression and discharge model needs to consider three factors: the condensation of single-phase steam, the discharge rate of the working medium in the pressure vessel and the heat conduction process of the working medium and the wall surface of the vessel are carried out in the decompression discharge process. The pressure vessel decompression and discharge process is a transient process, so that the time discretization of the calculation process is needed. The discrete idea of the pressure container discharge process is that the calculation process is divided into I time steps, the thermodynamic state of the working medium in the container is assumed to be kept unchanged in one time step, and in the time step, the upstream pressure container release calculation model provides the same initial conditions for the critical flow release process calculation at the breach.
The spatial dispersion Δ z is numerically preset by critical flow release simulation at the break. The critical flow release process at the fracture needs to consider four factors: thermodynamic parameters of working medium at a crevasse inlet, condensation of the working medium in the critical flow leakage process, wall heat transfer and determination of a critical section. The working medium flows in at the inlet of the break opening, reaches a critical state at the outlet of the break opening and then diffuses to the outside. Assuming that the flow channel length is L and the flow is considered one-dimensional, the flow channel is discretized into J segments of equal spatial length, and the calculation is performed in a stepwise manner from the J-th segment to the J + 1-th segment.
And step S3, determining the working medium state at the inlet of the crevasse. Working medium in the container leaks outwards through the crevasse, and has inlet resistance loss when entering the crevasse, wherein the pressure P calculation formula after the inlet resistance loss is as follows:
Figure BDA0003274352270000051
as is known, P calculated by equation (1) can be solved for other state parameters required for subsequent calculations according to methods that have been disclosed so far.
Wherein,
ΔPe-inlet resistance loss, Pa, of working medium from the container into the break;
c is the inlet resistance loss coefficient, which can be obtained by looking up a table according to the shape of the crevasse;
Figure BDA0003274352270000052
-the critical mass flow rate for the jth time step calculation, kg/(m)2S), the initially calculated critical mass flow rate is determined by step S1;
ρedensity of working medium entering the crevasse, kg/m3Of a value equal to the density of the working medium in the vessel
Figure BDA00032743522700000610
P is the pressure, Pa, after the working medium enters the crevasse;
PJ-internal pressure, Pa, at jth time step after breach leakage of the container;
step S4, calculating two-phase flow parameters in the crevasses, and making two assumptions about equal and uniform pressure and velocity of gas-liquid phases of the working medium on a flow section to obtain the leakage flow of the two-phase critical flow, wherein the flow of the working medium is considered to be one-dimensional, and the pressure and velocity of the working medium on the flow section are considered to be equal, so that an inner critical two-phase flow leakage equation of the crevasses can be obtained based on the two assumptions:
Figure BDA0003274352270000061
solving equation (2) can obtain pressure P of working medium in the discretized nth section of flow passagenVelocity of flow
Figure BDA0003274352270000062
And temperature
Figure BDA0003274352270000063
Wherein,
Figure BDA0003274352270000064
Figure BDA0003274352270000065
Figure BDA0003274352270000066
Figure BDA0003274352270000067
-the mixing density of the working medium in the (N-1) th flow channel in the N-section equal-length flow channels which are discretized in space is kg/m3The value of which can be determined by the density of the dry saturated steam of the n-1 section flow channel
Figure BDA0003274352270000068
Density of saturated water
Figure BDA0003274352270000069
Degree of dryness
Figure BDA0003274352270000071
Calculating to obtain;
Pn-1-the pressure of working medium in the (N-1) th section of flow channel in the N sections of equal-length flow channels which are discretized in space, Pa, and the pressure P in the 1 st section of flow channel1Taking the pressure P obtained in the step S6;
Pnthe pressure, Pa, of the working medium in the nth section of the flow channel in the N sections of the equal-length flow channels which are discretized in space;
Figure BDA0003274352270000072
partial differential of the speed of the working medium under the isothermal condition in the (N-1) th flow channel in the N sections of equal-length flow channels in the spatial discretization manner on the pressure;
Tn-1the value of the temperature K of the working medium in the (N-1) th section of flow passage in the N sections of equal-length flow passages which are discretized in space can be determined by the pressure P of the working medium in the (N-1) th section of flow passagen-1Obtaining;
Figure BDA0003274352270000073
the temperature K of the working medium in the nth section of flow channel in the N sections of equal-length flow channels which are discretized in space;
Figure BDA0003274352270000074
partial differential of working medium speed to temperature under isobaric condition in the N-1 section of flow channel in the N sections of equal-length flow channels in the spatial discretization;
Figure BDA0003274352270000075
the enthalpy of mixing of the working medium in the (N-1) th flow channel in the N spatially discretized equal-length flow channels can be J/kg, and the value of the enthalpy of mixing can be determined from the enthalpy of mixing of the working medium in the nth flow channelPressure P of working mediumn-1And temperature
Figure BDA0003274352270000076
Determining;
Figure BDA0003274352270000077
partial differential of the mixing enthalpy of the working medium under the isothermal condition in the (N-1) th flow channel in the N sections of equal-length flow channels in the spatial discretization manner on the pressure;
cpthe specific heat capacity at constant pressure of the mixed working medium, J/(kg. K);
Figure BDA0003274352270000078
-the rate of change of the break cross-section along the path, m;
rho-density of gas-liquid mixed working medium in container, kg/m3；
φm-the heat exchange capacity of the mixed working medium in the vessel, J;
φethe heat exchange amount of the working medium at the opening of the container J;
Figure BDA0003274352270000079
pressure P in the N-1 section of flow channel in the N sections of equal-length flow channels in the spatial discretizationn-1Enthalpy of the corresponding saturated liquid, J/kg;
Figure BDA0003274352270000081
the velocity m/s of the working medium in the (N-1) th flow channel in the N sections of equal-length flow channels which are discretized in space can be calculated by the following formula:
Figure BDA0003274352270000082
wherein,
Figure BDA0003274352270000083
-the critical mass flow rate for the jth time step calculation, kg/(m)2S), the initially calculated critical mass flow rate is determined by step S1.
Step S5 determines a critical cross section, and when the determinant det (a) of the coefficient matrix a is 0, the breach leakage reaches the critical flow, which is improved as follows:
Figure BDA0003274352270000084
in each time step, after each space step is calculated, a judgment is made, and if the calculation result meets the above formula (4) (4), the assumed critical mass flow rate G is considered to becAnd the working medium in the break reaches the critical value in the ith section of the flow passage. In practice, however, for a breaching channel of a high pressure vessel, the actual critical flow occurs at the exit point of the breaching channel; comparing the critical flow occurrence position determined in 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, the set value of the critical mass flow rate is decreased, and if the critical flow occurrence position is larger than the actual critical flow occurrence position, the set value of the mass flow rate is increased, so that the critical mass flow rate is further corrected:
Figure BDA0003274352270000085
wherein:
Figure BDA0003274352270000086
-corrected critical mass flow rate, kg/(m)2·s)；
Figure BDA0003274352270000087
The critical mass flow rate before correction, kg/(m)2·s)；
ΔGc——Gc(k)Correction value of (1), kg/(m)2·s)；
Figure BDA0003274352270000091
-critical flow occurrence location, m;
l is the length of the broken opening flow passage m;
will obtain
Figure BDA0003274352270000092
Thereafter, it is regarded as new in step S2
Figure BDA0003274352270000093
Repeating the calculation from step S3 to step S5, and repeating the steps until the value is within a certain size
Figure BDA0003274352270000094
On the premise, the calculation in step S6 is performed when the actual critical flow occurrence position is equal to the calculated critical flow occurrence position, and the calculation is performed
Figure BDA0003274352270000095
Namely the critical mass flow rate when critical occurs in the broken-opening flow passage
Figure BDA0003274352270000096
This is achieved by
Figure BDA0003274352270000097
And also as an initial value for the next time step calculation.
Step S6: calculating the pressure of working medium in the container, and for the container with the crevasse, the pressure calculation model of the working medium in the container is as follows:
Figure BDA0003274352270000098
in the formula:
PJ-1-internal pressure, Pa, at time step J-1 after breach leak of the container, the initial calculated pressure being determined by step S1;
Figure BDA0003274352270000099
-density of working medium in container at jth time step after breach leakage of container, kg/m3；
vg-pressure P in working medium in vesselJCorresponding specific volume of dry saturated steam, m3/kg, obtainable from pressure PJ-1Calculating to obtain;
vl-pressure P in working medium in vesselJCorresponding specific volume of saturated liquid, m3/kg, obtainable from pressure PJCalculating to obtain;
Figure BDA00032743522700000910
the dryness of the working medium of the J-th time step after the breach leakage of the container occurs is determined by the step S1;
PJ-internal pressure, Pa, at jth time step after breach leakage of the container;
Figure BDA0003274352270000101
-the critical mass flow rate for the jth time step calculation, kg/(m)2S), the initially calculated critical mass flow rate is determined by step S1;
Aecrack entrance area, m2The value thereof is determined by step S1;
Vvolvolume of the container body, m3The value thereof is determined by step S1;
Figure BDA0003274352270000102
the differential of the density of the working medium in the container to the pressure in the container; p used in the formulaJ-1The specific volumes of the saturated liquid and the dry saturated steam under the corresponding pressures can be respectively controlled by the known working medium pressure PJ-1And (4) obtaining the calculation, wherein the related calculation method can be realized by following the prior art.
Step S7 calculates the amount of heat exchange in the container: the heat transfer of working medium is divided into the heat conduction including the container body and the heat transfer between working medium in container internal wall face and the container, because the relative velocity between working medium in the container and the container internal wall face is approximate can be neglected, so consider that the heat transfer between working medium in container internal wall face and the container also carries out with heat conduction, can obtain the heat transfer model of working medium in the container:
Figure BDA0003274352270000103
in the formula:
Figure BDA0003274352270000104
Qvg-heat exchange amount, J;
Tw-wall temperature, K;
Tf-gas-liquid mixed working medium temperature, K;
Rvthermal conductivity and resistance of the container wall, K.W-1；
Rf-heat conduction resistance of gas-liquid mixed working medium, K.W-1；
Delta t is time difference, namely the set time step length, s;
d-vessel diameter, m;
δ — container thickness, m;
kv-the thermal conductivity of the vessel, W/(m · K);
h-vessel height, m;
Af-contact area of gas-liquid mixed working medium and fluid, m2；
kfThe heat conductivity coefficient of the gas-liquid mixed working medium, W/(m.K).
Step 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 temperature of the gas-phase working medium in the container; the second part is the temperature of the liquid phase working medium in the container; the third part is the vessel body temperature.
Wherein the first part: the temperature of the gas-phase working medium in the container is determined, the temperature of the gas-phase working medium is required to be the enthalpy change of the working medium, and the calculation formula is as follows:
Figure BDA0003274352270000111
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:
Figure BDA0003274352270000112
the calculation formula of the superheat degree of the gas-phase working medium obtained by the joint vertical type (8), (9) and (10) is as follows:
Figure BDA0003274352270000113
if the enthalpy value of the working medium is less than or equal to that of the dry saturated steam state, the temperature T of the gas phase working medium in the containergPressure P is still takenJThe corresponding saturation temperature; 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: temperature T of liquid phase working medium in containerlAt a value equal to the known pressure PJThe corresponding saturation temperature;
and a third part: the container body temperature is calculated by the following formula:
Figure BDA0003274352270000121
in the formula,
delta h is enthalpy change of working medium in the container, J/kg;
Qvgthe heat exchange quantity between the working medium in the container and the outside through the container is obtained in step S4;
Vvolvolume of the container body, m3The value thereof is determined by step S1;
hJ-1the enthalpy value of the working medium J-1 time step after the container leaks at the breach, J/kg;
Δρg-gas phase density at jth time step after breach leakage of container
Figure BDA0003274352270000122
Gas phase density to J-1 time step
Figure BDA0003274352270000123
Difference of kg/m3，
Figure BDA0003274352270000124
And
Figure BDA0003274352270000125
can be composed of PJAnd PJ-1Calculating to obtain;
Figure BDA0003274352270000126
-the critical mass flow rate for the jth time step calculation, kg/(m)2S), the initially calculated critical mass flow rate is determined by step S2;
Aecrack entrance area, m2；
Figure BDA0003274352270000127
Density of working fluid in vessel, kg/m3；
hJThe enthalpy value of the working medium at the J-th time step after the container leaks at the breach, J/kg;
ΔTgthe superheat degree of the gas-phase working medium in the container, K;
hgsat-pressure in the container PJThe lower corresponding enthalpy value of the dry saturated steam, J/kg, can be selected from PJObtaining;
cpgthe constant pressure specific heat capacity of the gas phase working medium in the container, J/(kg. K), can be selected from PJObtaining;
Tg-temperature of the gaseous working medium in the vessel, K;
Tl-temperature of the gaseous working medium in the vessel, K;
Tgsat-pressure in the container PJLower corresponding saturation temperature, K, which may be represented by PJObtaining;
Figure BDA0003274352270000131
-the container body temperature at the jth time step after breach leakage of the container, K, the container body temperature at the time of the initial calculation
Figure BDA0003274352270000132
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;
Figure BDA0003274352270000133
-container body temperature, K, at jth time step after breach leakage of the container;
mv-mass of the container body, kg;
cpvthe specific heat capacity at constant pressure of the container body is J/(kg. K);
step S9: the steps S2-S8 are circulated until the pressure in the container and the ambient pressure reach balance, the calculation is finished, and the temperature T of the gas-phase working medium in the inner part of the container at each time step is outputgTemperature T of liquid phase working mediumlPressure P of working mediumJDryness and degree of dryness
Figure BDA0003274352270000134
Leakage flow rate
Figure BDA0003274352270000135
Leakage flow rate
Figure BDA0003274352270000136
And (3) from step S2 to step S8, the calculation process of the breach leakage under a time step comprises two parts of critical flow calculation of working medium in the breach and physical parameter calculation in the container, after the calculation process from step S2 to step S8 is completed, the step S2 is returned to enter the calculation of the next time step, the process from step 2 to step 9 is repeated until the pressure in the container and the ambient pressure reach balance, and the calculation is finished. Simultaneously, the temperature T of the gas-phase working medium in the inner phase of the container at each time step length is recorded and outputgTemperature T of liquid phase working mediumlPressure P of working mediumJDryness and degree of dryness
Figure BDA0003274352270000137
Leakage flow rate
Figure BDA0003274352270000138
Wherein the leakage flow rate
Figure BDA0003274352270000139
Calculated according to the following formula:
Figure BDA00032743522700001310
wherein,
Figure BDA00032743522700001311
-the leakage flow of fluid through the breach at jth time step, kg/(s);
Aecrack entrance area, m2The value thereof is determined by step S1;
Aecrack entrance area, m2The value thereof is determined by step S1;
Figure BDA0003274352270000141
-ratio of inlet and outlet areas of the break;
Figure BDA0003274352270000142
at the J-th time step by
Figure BDA0003274352270000143
Repeatedly corrected critical leakage mass flow rate, kg/(m)2·s)。
The effect of the present invention will be described with reference to specific calculation objects, taking the pressure vessel with a break as shown in fig. 2 as an example, the temperature T of the gas-phase working medium is calculated according to the calculation of steps 1 to 9gTemperature T of liquid phase working mediumlPressure P of working mediumJDryness and degree of dryness
Figure BDA0003274352270000144
Leakage flow rate
Figure BDA0003274352270000145
Fig. 3 shows the change of the gas-liquid mixed working medium temperature (i.e. the fluid temperature) in the time period of 0-65s after the container is breached and leaked, according to the graph shown in fig. 3, the calculation result and the experimental result of the program are well matched, and the accuracy and the effectiveness of the program are proved.
In order to check the reliability of the calculation results of the present invention, the numerical calculation results of the present invention were compared with the test data, and the comparison results are shown in fig. 3.
The actual working condition experimental verification conditions comprise crack parameters, working medium state parameters in the container, geometric parameters of the container and measurement parameters.
Crack parameters: the length l of the crack is 10mm, the width W of the crack inlet is 23.1mm, the width W of the crack outlet is 17.2mm, the height COD of the inlet of the crevasse runner is 0.16mm, the height COD of the outlet of the crevasse runner 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 when the container is just broken and leaked is 1 (namely, all liquid phase);
vessel geometry: 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 from the time when the breach leakage just started to 65 s.
Program calculation parameter settings: besides setting crack parameters, working medium state parameters in the container, geometric parameters of the container and measurement parameters according to test working conditions, setting space step length delta z as l/100, and drawing the working medium temperature in the container in 0-65s after calculation.
The present invention may also be embodied in a storage medium comprising any one of a number of computer readable instructions which, when executed by one or more processors, cause the one or more processors to perform the method for calculating a critical flow release process value for a breached high pressure gas vessel, as generally described herein.
Through the above description of the embodiments, those skilled in the art will clearly understand that the method of the above embodiments can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware, but in many cases, the former is a better implementation manner. Based on such understanding, the technical solutions of the present application may be embodied in the form of a software product, which is stored in a storage medium (ROM/RAM), and includes several instructions for enabling a terminal (which may be a mobile phone, a computer, a server, or a network device) to execute the methods according to the embodiments of the present application.
The embodiments of the present application have been described above with reference to the drawings, but the present application is not limited to the above-mentioned embodiments, which are only illustrative and not restrictive, and those skilled in the art can make many changes and modifications without departing from the spirit and scope of the present application and the protection scope of the claims, and all changes and modifications that come within the meaning and range of equivalency of the claims are to be embraced within their scope.
The above embodiments are only for illustrating the invention and are not to be construed as limiting the invention, and those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention, therefore, all equivalent technical solutions also belong to the scope of the invention, and the scope of the invention is defined by the claims.

Claims (12)

1. A method for calculating a critical flow release process value 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: setting initial conditions, including setting a time step length delta t and a space step length delta z; acquiring geometric parameters of the container, such as volume V, diameter D and height H; acquiring the geometric parameters of a crevasse, including the width W of a crevasse runner, the height COD of the crevasse runner and the length l of the runner; obtaining initial calculation thermodynamic parameters of the working medium when the container is just subjected to breach leakage, including the initial pressure of the working medium
Figure FDA0003274352260000011
Initial dryness of working medium
Figure FDA0003274352260000012
Initial temperature of working medium
Figure FDA0003274352260000013
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 breaking port;
s5: determining a critical section;
s6: calculating the pressure of the working medium in the container;
s7: calculating the heat exchange amount in the container;
s8: calculating a system temperature of the vessel;
s9: and circulating the steps S2-S8 until the pressure in the container is balanced with the ambient pressure, and finishing the calculation.
2. The method of claim 1, wherein the method comprises the steps of: and S3, determining the working medium state at the inlet of the break port, wherein the pressure P after the resistance loss of the inlet of the break port is calculated according to the formula:
Figure FDA0003274352260000021
wherein,
ΔPe-inlet resistance loss, Pa, of working medium from the container into the break;
c-inlet drag loss coefficient;
Figure FDA0003274352260000022
-the critical mass flow rate for the jth time step calculation, kg/(m)2·s)；
ρeDensity of working medium entering the crevasse, kg/m3；
P is the pressure, Pa, after the working medium enters the crevasse;
PJ-internal pressure, Pa, at jth time step after breach leak of the container.
3. The method of claim 1, wherein the method comprises the steps of: the step S4: calculating two-phase flow parameters in the break port, and constructing a critical two-phase flow leakage equation in the break port:
Figure FDA0003274352260000023
solving equation (2) can obtain pressure P of working medium in the discretized nth section of flow passagenVelocity of flow
Figure FDA0003274352260000024
And temperature
Figure FDA0003274352260000025
Wherein,
Figure FDA0003274352260000026
Figure FDA0003274352260000027
Figure FDA0003274352260000031
Figure FDA0003274352260000032
-the mixing density of the working medium in the N-1 th flow passage in the N-section equal-length flow passages with the hollow dispersion is kg/m3；
Pn-1The pressure, Pa, of the working medium in the (N-1) th flow passage in the N sections of equal-length flow passages which are spatially discretized;
Pnthe pressure, Pa, of the working medium in the nth section of the flow channel in the N sections of the equal-length flow channels which are discretized in space;
Figure FDA0003274352260000033
partial differential of the speed of the working medium under the isothermal condition in the (N-1) th flow channel in the N sections of equal-length flow channels in the spatial discretization manner on the pressure;
Tn-1the temperature K of the working medium in the (N-1) th flow channel in the N sections of equal-length flow channels which are discretized in space;
Figure FDA0003274352260000034
the temperature K of the working medium in the nth section of flow channel in the N sections of equal-length flow channels which are discretized in space;
Figure FDA0003274352260000035
partial differential of working medium speed to temperature under isobaric condition in the N-1 section of flow channel in the N sections of equal-length flow channels in the spatial discretization;
Figure FDA0003274352260000036
the enthalpy of mixing of working media in the (N-1) th flow channel in the N sections of equal-length flow channels which are spatially discretized is J/kg;
Figure FDA0003274352260000037
partial differential of the mixing enthalpy of the working medium under the isothermal condition in the (N-1) th flow channel in the N sections of equal-length flow channels in the spatial discretization manner on the pressure;
cpthe specific heat capacity at constant pressure of the mixed working medium, J/(kg. K);
Figure FDA0003274352260000041
-the rate of change of the break cross-section along the path, m;
rho-density of gas-liquid mixed working medium in container, kg/m3；
φm-the heat exchange capacity of the mixed working medium in the vessel, J;
φethe heat exchange amount of the working medium at the opening of the container J;
Figure FDA0003274352260000042
pressure P in the N-1 section of flow channel in the N sections of equal-length flow channels in the spatial discretizationn-1Enthalpy of the corresponding saturated liquid, J/kg;
Figure FDA0003274352260000043
the speed m/s of the working medium in the (N-1) th flow channel in the N sections of equal-length flow channels which are discretized in space.
4. The method of claim 1, wherein the method comprises the steps of: the step S5: determining a critical section; and (2) performing critical condition judgment on each space step length under each time step length, if the critical judgment condition is met, determining that the working medium in the crevasse reaches a critical flow generation position under the critical mass flow rate, then comparing the critical flow generation position with the outlet position of the actual crevasse flow channel, if the critical flow generation position is inconsistent with the outlet position of the actual crevasse flow channel, correcting the critical flow rate, and repeating the steps from S2 to S5 until the critical flow generation position is consistent with the outlet position of the actual crevasse flow channel, wherein the critical mass flow rate at the critical flow generation position is the critical mass flow rate when the critical occurs in the crevasse flow channel.
5. The method of claim 4, wherein the method comprises the steps of: the critical judgment condition is
Figure FDA0003274352260000044
If the critical judgment condition is met, the working medium in the break reaches the critical state in the ith section of the flow channel under the critical mass flow rate; if the critical flow occurrence position is inconsistent with the outlet position of the actual crevasse flow channel, the critical mass flow rate correction formula is as follows:
Figure FDA0003274352260000051
wherein:
Figure FDA0003274352260000052
-corrected critical mass flow rate, kg/(m)2·s)；
Figure FDA0003274352260000053
The critical mass flow rate before correction, kg/(m)2·s)；
ΔGc——Gc(k)Correction value of (1), kg/(m)2·s)；
Figure FDA0003274352260000054
-critical flow occurrence location, m;
l is the length of the broken opening flow passage m.
6. The method of claim 1, wherein the method comprises the steps of: the step S6: calculating the pressure of the working medium in the container, wherein the pressure calculation model of the working medium in the container is as follows:
Figure FDA0003274352260000055
in the formula:
PJ-1-internal pressure, Pa, at J-1 time step after breach leakage of the container;
Figure FDA0003274352260000056
-density of working medium in container at jth time step after breach leakage of container, kg/m3；
vg-pressure P in working medium in vesselJCorresponding specific volume of dry saturated steam, m3/kg；
vl-pressure P in working medium in vesselJCorresponding specific volume of saturated liquid, m3/kg；
Figure FDA0003274352260000057
Working medium dryness of the J-th time step after the container is subjected to breach leakage;
PJ-internal pressure, Pa, at jth time step after breach leakage of the container;
Figure FDA0003274352260000061
-the critical mass flow rate for the jth time step calculation, kg/(m)2·s)；
AeCrack entrance area, m2；
VvolVolume of the container body, m3；
Figure FDA0003274352260000062
Differential of density of working medium in the vessel with respect to pressure in the vessel, PJ-1Is the specific volume of saturated liquid and dry saturated vapor under pressure.
7. The method of claim 1, wherein the method comprises the steps of: the step S7: calculating the heat exchange quantity in the container by adopting a working medium heat exchange model in the container as follows:
Figure FDA0003274352260000063
in the formula:
Figure FDA0003274352260000064
Qvg-heat exchange amount, J;
Tw-wall temperature, K;
Tf-gas-liquid mixed working medium temperature, K;
Rvthermal conductivity and resistance of the container wall, K.W-1；
Rf-heat conduction resistance of gas-liquid mixed working medium, K.W-1；
Δ t-step of time, s;
d-vessel diameter, m;
δ — container thickness, m;
kv-the thermal conductivity of the vessel, W/(m · K);
h-vessel height, m;
Af-contact area of gas-liquid mixed working medium and fluid, m2；
kfThe heat conductivity coefficient of the gas-liquid mixed working medium, W/(m.K).
8. The method of claim 1, wherein the method comprises the steps of: the step S8: calculating the system temperature of the container, including calculating the temperature T of the gaseous working medium in the containergTemperature T of liquid phase working medium in containerlAnd temperature of the container body
Figure FDA0003274352260000071
9. The method of claim 8, wherein the method comprises the steps of: calculating the gas phase working medium temperature T in the containergWhen the enthalpy value of the working medium is less than or equal to that of the dry saturated steam state, the temperature T of the gas phase working medium in the containergPressure P is still takenJCorresponding to the saturation temperature, T if the enthalpy of the working medium is greater than the enthalpy of the dry saturated steam stateg＝Tgsat+ΔTg
Wherein, TgsatIs the pressure P in the containerJThe lower corresponding saturation temperature, K; delta TgIs the superheat degree K of the gas phase working medium in the container.
10. The method of claim 8, wherein the method comprises the steps of: the temperature of the container body
Figure FDA0003274352260000072
Calculated using the following formula:
Figure FDA0003274352260000073
in the formula,
Qvgthe working medium in the container passes through the heat exchange quantity between the container and the outside;
Figure FDA0003274352260000074
-the container body temperature at jth time step, K, after breach leakage of the container;
Figure FDA0003274352260000075
-container body temperature, K, at jth time step after breach leakage of the container;
mv-mass of the container body, kg;
cpvthe specific heat capacity at constant pressure of the container body is J/(kg. K).
11. The method of claim 1, wherein the method comprises the steps of: the step S9: the steps S2-S8 are circulated until the pressure in the container and the ambient pressure reach balance, the calculation is finished, and the temperature T of the gas-phase working medium in the inner part of the container at each time step is outputgTemperature T of liquid phase working mediumlPressure P of working mediumJDryness and degree of dryness
Figure FDA0003274352260000081
Leakage flowMeasurement of
Figure FDA0003274352260000082
Leakage flow rate
Figure FDA0003274352260000083
Wherein the leakage flow rate
Figure FDA0003274352260000084
Calculated according to the following formula:
Figure FDA0003274352260000085
wherein,
Figure FDA0003274352260000086
-the leakage flow of fluid through the breach at jth time step, kg/(s);
Aecrack entrance area, m2；
AeCrack entrance area, m2；
Figure FDA0003274352260000087
-ratio of inlet and outlet areas of the break;
Figure FDA0003274352260000088
at the J-th time step by
Figure FDA0003274352260000089
Corrected critical leakage mass flow rate, kg/(m)2·s)。
12. A storage medium having computer readable instructions stored thereon which, when executed by one or more processors, cause the one or more processors to perform a method of calculating a critical flow release process value for a breached high pressure gas vessel as claimed in any one of claims 1 to 11.
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