CN107590336A - Method for numerical simulation of the fuel gas pipeline leakage to internal flow - Google Patents
Method for numerical simulation of the fuel gas pipeline leakage to internal flow Download PDFInfo
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Abstract
Method for numerical simulation the invention discloses fuel gas pipeline leakage to internal flow, it is related to gas technology field；Its analogy method is as follows：Establish simulation softward；Fuel gas pipeline leakage models and simulation analysis；Fuel gas pipeline leakage Numerical Value Result Analysis；Before and after the present invention is to fuel gas pipeline leakage, the change of pipeline interior flow field is analyzed；According to CFD Fluid Mechanics Computation knowledge, fuel gas pipeline leakage is simulated with Fluent, according to Hydrodynamics Theory, the characteristics of analysis obtains gas pipeline interior flow field before and after fuel gas pipeline leakage；According to Hydrodynamics Theory, the characteristics of analysis obtains gas pipeline interior flow field before and after fuel gas pipeline leakage；According to CFD Fluid Mechanics Computation knowledge, the fuel gas pipeline leakage under different leak conditions is simulated, inlet pressure is bigger, then easier generation leakage accident；Leakage aperture is bigger, and area with high mercury proportion also increases around leak.
Description
Technical field：
Method for numerical simulation the present invention relates to fuel gas pipeline leakage to internal flow, belongs to gas technology field.
Background technology：
Current gas pipeline transport is existing, and oneself turns into the most convenient, economic means of transportation.But when gas pipeline because soil is rotten
Erosion, when the reason such as pipeline aging or the destruction of its other party leaks, the position of leakage point can not be such as detected in time, will
Influence is speedily carried out rescue work the time, thus probe into the Release and dispersion rule of gas pipeline for being accurately positioned of leakage point, leak strick precaution etc. all
Tool is of great significance.And after leakage accident occurs, if the parameter of source of leaks can be determined with the most short time, so as to
Further division emergency evacuation region, then it can start emergency response for policymaker and foundation is provided, so as to reduce property damage
Become estranged casualties.
Nowadays as the industries such as China's rapid development of economy, petrochemical industry grow stronger day by day, it is engaged in hazardous chemical production
The scale of manufacture is increasing, and the transport of gas pipeline, use is also more and more, to be let out so as to which there occurs the combustion gas of enormous amount
Leakage accident.Why fearful fuel gas pipeline leakage is, is because it can make big once it is very huge to leak damaging property
Personnel's property of area is on the hazard.Only 2016 it is annual in all parts of the country monthly because accident caused by fuel gas pipeline leakage just
Reach more than 70, in numerous accidents, many accidents are due to rescue not in time or can not accurately determine accident generative center
Specifying information, cause the hysteresis quality and purposelessly property of rescue.Therefore, researching and analysing for fuel gas pipeline leakage accident
It is very necessary.
China is in the starting stage in the related research topic of dangerous material leakage accident at present, and association area is in reason
By conceptual phase, for product leakage accident of once causing danger, personnel withdraw property transfer distance and there is no determination theoretical foundation.
Up to now, the statistics in ERG2000 that China uses at present or that the U.S., Canada's joint work out, due to not having
Specific transfer distance, after generation accident, the transfer of personnel and property often according to the experience of site disposal personnel, error compared with
Greatly.It is difficult to find when not only leaking, when being exactly that many gas pipeline accidents occur, also can only carries out evacuating personnel with sensation,
Cause people to cause great loss, consume a large amount of manpower and materials, or even pay the cost of life.
In order to realize safe operation burning line, it is necessary to possess abundant gas pipeline scientific theory and advanced
Technical method.Safety precaution for China's burning line mainly by way of inspection, and when leak occur after to leakage ground
By the way of the positioning of point is then detected or punched using ground detector, take longer and can not well realize and be accurately positioned.
Therefore, in order to reduce causality loss, reduce row's Check times of leakage point, urgent need is entered to the leakage process of burning line
Row is probed into, to prevent pipe leakage accident.
Domestic and international present Research analysis：
After dangerous matter sources leak, quickly and accurately determine that the parameter information of dangerous matter sources is extremely important, at some
Under conditions of burst, or the parameter of source of leaks is determined in the case of Limited information with the most short time, so as to further
Emergency evacuation region is divided, starting emergency response for policymaker provides foundation, therefore the source parameter of the dangerous matter sources to leaking suddenly
Research can support emergency response decision-making, so as to reduce property loss and casualties.Leakage accident can not only so be covered
Source strength inverse in the problem in science that is contained, while studied by the problem of key issue under leakage accident, for can be with
Really realize under Sudden Leakage emergency conditions, the solution to leakage provides scheme.
Some typical Leakage of City Gas Pipeline accidents of recent domestic, digital startling one by one, personnel's wound
Die heaviness, resource significant wastage.And at home, in January, 2017, within the short time less than one month, only China just occurs
42 gas accidentses, cause injured 9 people of more than 60 people dead altogether, personal injury and property loss are caused to resident, society is caused
Economic loss and the wasting of resources.The reason for simultaneously serious analysis pipeline accident occurs should be paid attention to strongly and safeguard measure could more
The good generation for preventing such disaster.
In the experiment research on pipe leakage, external scholar just expands system early in 20 end of the centurys
Research, the main research of gas leakage process is the calculating of released gas rate.The research development of leak model is more early,
Levenspiel exists《Engineering fluid flows and heat transfer》In propose storage tank and occur to let out when the fracture of pipeline total cross-section and hole leakage
The computation model of leakage quantity；Nigeria scholar Olorunmaiye and British scholar Catlin use method of characteristic and fluid force respectively
Method calculates released gas rate when High Pressure Gas Transmitting Pipeline is completely severed.
And in recent years, domestic related scholar have also been made the experimental study of correlation, and intensity is leaked to combustion gas aperture and macropore
Determination test platform, the leakage intensity under different pore size is measured.Maintenance data acquisition system and Gas Clam underground gas
On-line computing model, the small hole leaking to caused by the mesolow burning line of city due to reasons such as corrosion carry out Experimental Research, used
The experimental system of full size, distribution Diffusion Law of the analysis natural gas in soil, the leakage concentration for showing gas are in the time
S type curvilinear motions, good data supporting is provided for experiment from now on and analog study.But these experimental studies are also all
It is the approximate experiment imitated in laboratory, is not gas leakage emulation experiment truly, due to combustion gas (combustion gas master
Refer to natural gas, main component is methane) there is the characteristics of inflammable and explosive, real experiment has very big danger.Take and
Instead of research is all built upon what is inquired on the basis of numerical simulation mostly.
The current research to fuel gas pipeline leakage problem in the world is simultaneously immature.Conventional research is generally only with hypothesis
Condition founding mathematical models only add some simple influence factors progress sunykatuib analyses.The country is to gas pipeline leakage
Numbered analog simulation and the specificity analysis of diffusion need to be goed deep into improving afterwards.
The content of the invention：
In view of the above-mentioned problems, the technical problem to be solved in the present invention is to provide fuel gas pipeline leakage to internal flow
Method for numerical simulation.
The fuel gas pipeline leakage of the present invention is as follows to the method for numerical simulation of internal flow, its analogy method：
Step 1：Establish simulation softward：
After the completion of modeling, mesh generation is carried out；It can be divided into following 3 step using the simulation of FLUENT softwares：(1), preceding place
In the reason stage, completed with Gambit；(2) stage, is solved, is completed with fluent；(3), post-processing stages, completed with tecplot；
Completed in pretreatment stage using front processor Gambit softwares, wherein the unstructured grid generation journey contained
Sequence generates grid for relative complex geometry, and it can generate grid, but people under two-dimensional geometry body and three-dimensional geometry body
The grid of work generation is smaller than the grid number generated in software, also can be smaller in the consumption of internal memory；And simulate what is calculated
Process part-solution stage uses Fluent softwares, and operation solves equation, setting fluent material and physical property comprising selection, set
Determine boundary parameter and solve control parameter, solve discrete equation, result visualization；For post-processing stages, for no office
The grid of portion's encryption can be post-processed using tecplot, and for there is the grid of local cypher to use what is carried in Fluent
Post-processing function is handled；
Step 2：Fuel gas pipeline leakage models and simulation analysis：
2.1st, FLUENT numerical simulation calculations and operation：
Analog simulation is carried out using Fluent, the first step carries out the foundation of physical model in Gambit, then carries out net
The division of lattice, the selection of boundary condition is set, after exporting Mesh files, can be carried out in next step；Second step selects in Fluent
Equation, required model, and further conditions setting and control parameter, and start to calculate are solved, obtaining a result to be carried out down
Single stepping；The file that 3rd step preserves after Fluent is solved is imported in Tecplot and post-processed；
2.1.1 FLUENT solvers and setting：
Fluent provides two kinds of solver types, and a kind of is the solver based on pressure, and another kind is based on density
Solver；Using the solver based on pressure；
2.1.2 FLUENT running environment is set：
In the setting for opening the running environment of Fluent softwares, it can be seen that need to set calculating reference pressure and gravity
Two options；In Fluent, pressure is relative to the relative pressure of operation reference pressure, that is, relative pressure；With reference to
Pressure is atmospheric environmental pressure, is set to standard atmospheric pressure 101325Pa, and reference pressure position selection acquiescence point (0,0,0) is carried out
Research；
Setting above is realized in Fluent, transient simulation is then selected in General again, is weighed in leakage process
The change of power has a great influence for leakage process, therefore need to consider that gravity influences；Due to gas leakage speed, so opening
Open Gravity and the -9.8m/s that acceleration of gravity is Y direction is set2；
2.1.3 FLUENT computation models select：
When running environment is set, after the selection of solver form is fixed, selection computation model, it uses turbulence model, so
Energy equation, k- ε equations and component transport equation are opened in Models afterwards, selects component delivery model, and define component and be
Methane and air；Because Fluent itself is accompanied with material database, so directly selecting；It is of course also possible to as needed certainly
Define the parameter and attribute of new material or the existing material of modification；
2.1.4, FLUENT primary condition and boundary condition are set：
The primary condition that simulation calculates is set as：Before gas pipeline is in non-leak condition, concentration and speed are all zero,
After air is full of in flow field and keeps stable state, gas pipeline to be in non-leak condition, pressure entrance 0.4Mpa, internal diameter
Ignore, flowed into 1m/s speed；
2.1.5, FLUENT solves parameter setting：
Analog simulation is carried out using Fluent, the first step carries out the foundation of physical model, stroke of grid in Gambit
Divide, the selection of boundary condition；Second step selects to solve equation, required model, and further conditions setting in Fluent
And control parameter, and start to calculate；The file preserved after finally Fluent is solved is imported in Tecplot to be located after progress
Reason, directly displays image or image is played to viewing frame by frame, the specific data that Fluent preserves included in file also may be used
Call wherein；Just primary condition and boundary condition are initialized after being provided with, then set step-length to be simulated
Calculate；
2.2nd, straight tube and T tube models are established and picture exports：
It is conceptual modelling using 2 kinds of modeler models, one；Two be parametric modeling, with both approaches, and by straight tube,
T rows pipe and complicated pipe carry out practical operation modeling procedure；All it is to try every possible means to control during using Numerical Methods Solve governing equation
Equation carries out discrete on area of space, then solves obtained discrete equation group；Want the discrete controlling party in spatial domain
Journey, it is necessary to use grid；
2.2.1, straight tube pipeline internal model is established and picture exports：
The illustraton of model before straight tube is not revealed is first established, because model and model before leakage after leakage, let out except adding one
Dew point parameter, remaining basic parameter is identical, and for straight tube, the pipe that T is managed under these simple scenarios only establishes model before its leakage,
In complicated pipe, the model after leakage before it is revealed specifically is established, to be that the data analysis of next step exports picture.
Straight tube pipeline first establishes straight tube pipeline model；The DM modules that straight tube model is carried by ANSYS are established, and are utilized
Gambit softwares draw straight tube two dimensional model figure by straight tube pipeline model size is established；Then in the attempting of workbench,
Carry out mesh generation；
Solve and set in fluent, after having calculated, make the pressure cloud atlas before leakage, speed cloud atlas；By tonogram
As can be seen that straight tube inlet pressure is maximum, overpressure tapers into flowing, minimum to reaching during outlet；By with reality
Test the requirement of Comparative result and Gambit to mesh quality in itself, grid division；After mesh generation is completed, specified boundary
Condition types and zoning type, specific boundary condition are arranged in Fluent and carried out, and finishing above work can will
The output of Mesh files preserves；
2.2.2, T pipelines internal model is established and picture exports：
Solve and set in Fluent, after having calculated, make the pressure cloud atlas before leakage, speed cloud atlas, by tonogram
As can be seen that in T row pipe T fonts junction, pressure has significant change, and pressure significantly increases at pressure ratio smooth flow；
The foundation of complicated pipeline model and picture output before and after 2.3 leakages：
2.3.1, model is established before complicated pipeline internal leakage：
The DM modules that complicated tube model is carried by ANSYS are established, and straight tube two dimensional model is drawn using Gambit software sizes
Scheme, two dimensional model figure before specific complicated pipe leakage；In the attempting of workbench, mesh generation is carried out；
3.3.2, internal simulation after complicated pipe leakage：Two dimensional model after the specific complicated pipe leakage of foundation；Then establish
Two dimensional model figure after specific complicated pipe leakage；In the attempting of workbench, mesh generation is carried out.
Step 3: fuel gas pipeline leakage Numerical Value Result Analysis：
3.1st, CFD numerical simulation results are analyzed：
On the basis of second step, the data being calculated are simulated according to fluent softwares, it is analyzed and reveals factor
Influence, and obtain a result；
3.2nd, numerical simulation result is analyzed：
(1), internal simulation result after straight pipeline leakage：
Scaled residual plot is made using ANSYS14.0；Post-processing makes in straight tube pipeline methane concentration at any time
Between variation diagram；Figure is leaked by straight tube, it is clear that the change of methane concentration over time, occurs obvious in leakage point
Change, at the 125th second, leakage point was gradually stablized；
(2), internal simulation result after T pipe leakages：
The DM modules that T rows tube model is carried by ANSYS are established, and in the attempting of workbench, carry out mesh generation, should
Scaled residual plot is made with ANSYS14.0；Post-processing makes methane concentration in T row pipelines and changes over time figure；
Schemed by T row pipe leakages, the change of methane concentration over time, significant change occurs in leakage point, was leaked at the 125th second
Point is gradually stable；
(3), internal simulation result after complicated pipe leakage：
Due to having built up illustraton of model, so directly being analyzed on the basis of second step；Solve and set in fluent,
After having calculated, the pressure cloud atlas before leakage, speed cloud atlas are made；
Comprehensive analysis, the pipeline interior flow field analysis before the leakage of T rows pipe and after the leakage of complicated pipe draw main conclusions：
Before leakage, internal pipe pressure vector, velocity is maximum in entrance, is tapered into the flowing of combustion gas, to outlet
When reach minimum；After revealing, its internal pressure vector, velocity varies widely, when it is in leakage point,
Significant change can all occur for pressure and speed, over time, gradually stable in the methane concentration change of leakage point.
3.3rd, pipe leakage influence factor：
3.3.1 pipeline pressure changes the influence to leakage：
In Practical Project, pipeline pressure is bigger, easier generation leakage accident, and now temperature and speed in pipeline
Equivalent also increases therewith.
3.3.2 influence of the varying aperture to leakage, is leaked：
When pipeline pressure is certain, and leak aperture is smaller, leaked into the unit interval at leak in soil environment
Combustion gas gas mass flow reduce, so as to which range of scatter in same time in soil is smaller, the danger zone of leakage
It is smaller.And conversely, leakage aperture is bigger, area with high mercury proportion also increases around leak.
Preferably, the turbulence model is standard k-ε turbulence model.
Compared with prior art, beneficial effects of the present invention are：Before and after fuel gas pipeline leakage, pipeline interior flow field
Change is analyzed；The Geometric Modeling process of pipeline is carried out to fuel gas pipeline leakage problem, mesh generation is carried out, finally uses
Fluent is post-processed after having solved with Tecplot, and then gas pipeline interior flow field is divided with the picture drawn
Analysis, and detailed analysis is done to the influence factor of leakage；Analysis is comprehensive, and can carry out later period maintenance.
Brief description of the drawings：
For ease of explanation, the present invention is described in detail by following specific implementations and accompanying drawing.
Fig. 1 is straight tube illustraton of model in the present invention；
Fig. 2 is straight tube two dimensional model figure in the present invention；
Fig. 3 is straight tube mesh generation figure in the present invention；
Fig. 4 is T row tube model figures in the present invention；
Fig. 5 is illustraton of model before complicated pipe leakage in the present invention
Fig. 6 is two dimensional model figure before complicated pipe leakage in the present invention
Fig. 7 is mesh generation figure before complicated pipe leakage in the present invention；
Fig. 8 is illustraton of model after complicated pipe leakage in the present invention；
Fig. 9 is two dimensional model figure after complicated pipe leakage in the present invention；
Figure 10 is mesh generation figure after complicated pipe leakage in the present invention；
Figure 11 is simulation drawing after straight tube leakage in the present invention；
Figure 12 leaks simulation drawing for T rows pipe in the present invention.
Embodiment：
It is specific below by what is shown in accompanying drawing to make the object, technical solutions and advantages of the present invention of greater clarity
Embodiment describes the present invention.However, it should be understood that these descriptions are merely illustrative, and it is not intended to limit the model of the present invention
Enclose.In addition, in the following description, the description to known features and technology is eliminated, to avoid unnecessarily obscuring the present invention's
Concept.
As shown in Figures 1 to 12, present embodiment uses following technical scheme：
First, hydrodynamics basic theories and simulation softward：
1.1st, hydrodynamics basic theories：
In fluid mechanics problem research, there are three most basic laws of conservation, including the conservation of mass, the conservation of momentum, energy
Measure conservation.The present invention applies several basic fluid mechanics equations, and fluid flow applications turbulence state, while uses turbulent flow
Boltzman transport equation Boltzmann is calculated.
It is fuel gas inside gas pipeline, due to the compressibility of combustion gas, so the flowing of combustion gas is not in pipeline
Stationary flow.After given inlet pressure, the decline of pressure when being flowed with combustion gas in gas pipeline, combustion gas is inside pipeline
Density also slowly reducing, its speed is also gradually reduced, and the change of combustion gas density is negligible not only in low pressure pipeline
Meter.Therefore, it is respectively pressure p, density p, flow velocity u, temperature T to influence the parameter of right feed channel leakage flow to have 4, and they are same
When be coordinate (z.y.x) and time t function, to try to achieve this tittle, be then related to several basic fluid forces introduced below
Learn equation.
1.1.1, continuity equation：
Because any flow field problem must all is fulfilled for the conservation of mass law of motion, so the law can be expressed as, during unit
The increase of quality in interior fluid infinitesimal, equal to the net quality that the micro unit is flowed into same time interval.Can by this law
To draw mass-conservation equation, commonly referred to as continuity equation.
Continuity equation is specific expression form of the mass conservation law in hydrodynamics, and any flow field problem all must
Mass conservation law must be met, i.e., it embodies increased fluid mass and the fluid mass of reduction by a series of mode
It is the same：
The density of ρ---- gas, kg/m in formula3；
T---- time, s；
uiSpeed (u, v, w) on---- directions of (x, y, z) three, m/s.
The continuity equation of special flowing is expressed as follows.
Incompressible gas flows：
Steady gas flows：
1.2.1, the equation of momentum：
The equation of momentum (Navier Stokes equation) will be used by studying any type of motion, and be otherwise known as N-S side
Journey.Because the flowing of combustion gas meets Newton's second law, meet the equation of motion, so the equation of momentum can be expressed as：It is micro-
The momentum of fluid is equal to various power sums of the external influence on the micro unit to the rate of change of time in first body.The equation with
The momentum conservation equation on i directions is derived based on Newton's second law.
The dynamic viscosity of wherein μ --- fluid, Pas；
P --- absolute pressure, Pa；
G --- acceleration of gravity, m/s2。
It can then be write as natural gas line：
Wherein D---- internal diameter of the pipeline, m；
The pressure of flowing gas, Pa in P---- Gas Pipe；
F---- mass force, N；
G---- acceleration of gravity, m2/s；
θ---- inclination angle between pipeline and level, rad；
λ---- frictional resistant coefficient.
1.1.3 energy equation：
Because combustion gas is flowed in pipeline certainly with the flowing of energy, so being related to energy equation.Energy equation is determined
Rule is to include the philosophy that the running system of heat exchange must is fulfilled for.Energy equation law can be expressed as：In micro unit
The increment rate of energy be equal to net hot-fluid momentum into micro unit plus muscle power with face power to micro unit work done, then basis
The first law of thermodynamics, i.e. law of conservation of energy, the energy equation of fuel gas flow can be obtained：
Wherein H---- unit mass gas liberated heat, J/kg；
E---- gas internal energy, J/kg；
Z---- pipeline location height, m；
The enthalpy of h---- gas, J/kg.
1.1.4, The Ideal-Gas Equation：
When institute's learning gas is perfect gas, that is, the own vol of gas molecule is have ignored, regards them as matter
Point；Disregard molecular potential, the collision occurred between molecule and between molecule and wall is perfectly elastic, does not cause kinetic energy to damage
Lose, the equation of gas state is：
P=ρ RT (1-7)
And when actually combustion gas is under the environmental condition of standard, the equation of gas state is：
P=Z ρ RT (1-8)
Wherein Z-- com-pressible factors,
P-- absolute pressures, Pa；
V-- gas specific volumes, m3·kg-1；
R-- universal gas constants, Jkg-3·K-1；
T-- thermodynamic temperatures, K.
When gas pressure meets PPC-1<<2 or TTC-1>2 at the same time ppc-1During ＜ l, you can regard as managing
Think gas.The critical pressure Pc of combustion gas (methane) gas is 4.59Mpa, and critical humidity TC is -82.6 DEG C, and mould in this experiment
The gas pipeline of plan is combustion gas (methane) conveyance conduit of urban inner, and its discharge pressure is typically between 0.2-0.4Mpa, far
Much smaller than critical pressure, thus can position be considered as perfect gas.
(1) preferable Incompressible gas density equation：
In Incompressible gas, the density of gas is solely dependent upon operating pressure, and in Fluent settings, operation pressure
Power can generally be set to standard atmospheric pressure, so as to which in incompressible model, the density of gas is normal atmosphere pressure
Density value.
(2), ideal compressible gas density equation：
Whether the gas of flowing there is compressibility can be weighed with Mach number M, as shown by the equation：
M≡u/c (1-10)
Wherein U-- gas flow rates, m/s-1；
C-- velocities of sound m/s-1。
When Mach number is far smaller than 1 (M ＜ 0.1), the compressibility of gas can be ignored, while the density of gas
It can be considered not with pressure change, but when M is close to 1, it is necessary to consider that compressibility influences to caused by gas density.
For compressibility gas, its density solves mode as shown by the equation：
Wherein：The gauge pressure of P --- each infinitesimal, Pa.
It can be seen that add shadow of the gauge pressure on each infinitesimal to density in the method that compressible gas density calculates
Ring so that density with infinitesimal gauge pressure it is different and different.
1.2nd, Equations of Turbulence：
For Equations of Turbulence, this paper selection standard k- ε two-equation models are solved, and such two-equation model helps
There is the problem of end stream fluid distance change and end stream time cumulation in transmitting procedure in solving, flowed suitable for pipeline
Gas port.Standard k-ε equations are mutually used for reference derivation by experimental phenomena and empirical equation and formed, and are a semiclassical equations,
It is widely used in flow of fluid field because the turbulent range of its calculating precisely, applicable is wide.
Standard k- ε both sides in time averaging model claim model more to be economized on resources than other two-equation models and maximum
Limit ensure that the precision of calculating, therefore be the preferred model that simple turbulent motion is directed in this simulation calculation.In k- ε
In model, k is rapid energy, and ε is the dissipative shock wave of rapid energy, and both reflect characteristic velocity and characteristic length scales, mainly passed through respectively
Two additional equations are solved to determine turbulent flow viscosity coefficient, and assume to simplify using Boussinesq, seek contact turbulent stress：
K equations：
ε equations：
Wherein Cε=0.09, Cε1=1.44, Cε2=1.92, CD=0.8, rapid energy k and rapid energy dissipative shock wave ε turbulent flow Pu Lang
Special number is：σk=1.0, σε=1.3, and υt=CμK2/ε。
K-- tubulence energies, J；
ε -- turbulence dissipation rate.
1.3rd, Fluid Mechanics Computation：
Fluid Mechanics Computation, it is that CFD (computational fluid dynamics) is modern age hydrodynamics and meter
The product of calculation machine combination of sciences, and for having research method most commonly seen in 3 in hydrodynamics, it is to calculate fluid respectively
Mechanics, theoretical fluid mechanics and experimental fluid mechanics, they are the Main Basiss and theoretical direction of Study of Fluid mechanics.Wherein
Theory analysis can provide required foundation and data for experimental study, and needed for testing and can then being provided for numerically modeling
The data and result of calculation wanted, numerical simulation are then one kind of quantitative inquiry experiment, and these characteristics determine calculating fluid force
Learn the advantage in research work.
The electronic computers of CFD mono- are instrument, are carried out using the mathematical method of various discretizations, the problem of Fluid Mechanics
Numerical experiment, computer mould, which fits, to be researched and analysed, to solve various practical problems.
CFD general principle is to apply Numerical Methods Solve Nonlinear differential eguations, and this equation group passes through simultaneous matter
Amount, momentum, energy and self-defined scalar equation obtain, so as to show flow location form, the improvement and amplification of implementation process device.
1.4th, simulation softward is established：
Fluent is to be in one of rank first, more common CFD software bag now, and current fluid is built
One of the most frequently used software in mould.
After the completion of modeling, mesh generation is carried out.Fluent mesh generation has many advantages, and it can enough be carried
For flexible grid characteristics, a variety of grids can be supported so that user can use unstructured and structuring with unrestricted choice
For grid to divide sufficiently complex geometrical issues, the mesh adaption characteristic that Fluent is provided can be utilized in solution procedure by
It is middle that grid is optimized according to the result of calculation obtained.
Fluent softwares are easy to left-hand seat for beginner, and user can be allowed to define more arbitrary boundary conditions, such as flow
Entrance and export boundary condition, wall boundary condition etc., the component of a variety of local Descartes and cylindrical-coordinate system can be used
Input, all boundary conditions can change with room and time, including axial symmetry and cyclically-varying etc..It can be used to
The relevant industry of the various fields such as the energy, space flight.It possesses a variety of mathematics physics models, analysis method and discrete mode, so as to
Meet that the computational accuracy in research field, reliability and stability etc. require.Fluent application is quite varied, fits
For various fields such as flow of fluid, chemical reactions, such as analog approach is compressible with the flowing of incompressible fluid；Or
The various problems such as stable state and Transient Flow.
It can be divided into following 3 step using the simulation of FLUENT softwares：
1st, pretreatment stage, completed with Gambit；
2nd, the stage is solved, is completed with fluent；
3rd, post-processing stages, completed with tecplot.
Completed in pretreatment stage using front processor Gambit softwares, wherein the unstructured grid generation journey contained
Sequence effectively can generate grid for relative complex geometry, and it can give birth under two-dimensional geometry body and three-dimensional geometry body
Into grid, but manually generated grid is smaller than the grid number generated in software, also can be smaller in the consumption of internal memory.
And simulate the process part-solution stage calculated and use Fluent softwares, operation solves equation, setting fluid material comprising selection
Material and physical property, setting boundary parameter and solution control parameter, solve discrete equation, result visualization etc..For post-processing rank
Section, can be post-processed for the grid of no local cypher using tecplot, and for there is the use of the grid of local cypher
The post-processing function carried in Fluent is handled.
Table 1-1 CFD softwares are simulated
Two：Fuel gas pipeline leakage models and simulation analysis：
2.1st, FLUENT numerical simulation calculations and operation：
Analog simulation is carried out using Fluent, the first step carries out the foundation of physical model in Gambit, then carries out net
The division of lattice, the selection of boundary condition is set, after exporting Mesh files, can be carried out in next step.Second step selects in Fluent
Equation, required model, and further conditions setting and control parameter, and start to calculate are solved, this is almost to analog result
There is conclusive effect, next step operation can be carried out by obtaining a result.The file that 3rd step preserves after Fluent is solved
Import in Tecplot and post-processed；
2.1.1 FLUENT solvers and setting：
Fluent provides two kinds of solver types, and a kind of is the solver based on pressure, and another kind is based on density
Solver.Both solvers have identical to solve object, and the governing equation of the solution used in them is exactly the side in step 1
Journey, they are continuity equation, the equation of momentum, energy equation and the rapids of describing mass conservation, the conservation of momentum and the conservation of energy
Flow equation.Although two kinds of solvers are all suitable for most of flowing solutions, for some specific mobility status, selection
One kind in two kinds of solvers is probably that solving result is more accurate；Using the solver based on pressure.
2.1.2 FLUENT running environment is set：
In the setting for opening the running environment of Fluent softwares, it can be seen that need to set calculating reference pressure and gravity
Two options.In Fluent, pressure is relative to the relative pressure of operation reference pressure, that is, relative pressure.With reference to
Pressure is atmospheric environmental pressure, is set to standard atmospheric pressure 101325Pa, and reference pressure position selection acquiescence point (0,0,0) is carried out
Research.
Setting above is realized in Fluent, transient simulation (Transient) is then selected in General again, lets out
The change of gravity has a great influence for leakage process during leakage, therefore need to consider that gravity influences (not considering buoyancy effect).By
In gas leakage speed, so opening Gravity and setting the -9.8m/s that acceleration of gravity is Y direction2。
2.1.3 FLUENT computation models select：
When running environment is set, solver form is selected after determining it is necessary to select computation model, the problem of consideration
Have：Whether computation model considers heat transfer (present invention does not consider to conduct heat), and fluid flow state is laminar flow or turbulent flow (using rapid
Stream), if it is multiphase flow (no), if having phase transformation (no), if chemical constituent change and chemical reaction be present (herein not
Consider that chemical change occurs for leakage), if consider radiation (no) etc..Because the present invention uses turbulence model, so selection
The standard k-ε turbulence model being most widely used, Standard law of wall can be used, its coexponent can be acquiescence index, then
Energy equation (Energy), k- ε equations and component transport equation (Species Transport), selection are opened in Models
Component delivery model (Species Transport), and it is methane and air (methane-air) to define component.Due to
Fluent itself is accompanied with material database, it is possible to directly selects.It is of course also possible to self-defined new material as needed
Or the parameter and attribute of the existing material of modification；
2.1.4, FLUENT primary condition and boundary condition are set：
Primary condition is flow field problem flow regime of every on initial time flow field.It is in initial time, combustion gas
The state that each is put in flow field in pipeline internal model.The primary condition that present invention simulation calculates is set as：At gas pipeline
Before non-leak condition, concentration and speed are all zero, and air is full of in flow field and keeps stable state, gas pipeline is in not
After leak condition, pressure entrance 0.4Mpa, internal diameter is ignored, and is flowed into 1m/s speed.
Because pressure inside natural gas line be present, and the external world is normal atmosphere (An), pressure differential between the two be present, so
Coboundary and right margin select pressure export boundary condition, and pressure value is standard atmospheric pressure.
Boundary condition be divided into it is a variety of, it is different according to problem and change.And the flowing shape of the fluid in flow field at any time
State will meet the boundary condition of setting.
Tube wall selects wall boundary condition wall.Set if not specifying, fluent gives tacit consent to the institute except entrance and exit automatically
It is wall to have interface, and the present invention uses default value, and the specific setting of each boundary condition see the table below shown in 2-1.
Table 2-1 boundary conditions are set
2.1.5, FLUENT solves parameter setting：
The present invention carries out analog simulation using Fluent, and the first step carries out foundation, the grid of physical model in Gambit
Division, the selection of boundary condition；Second step selects to solve equation, required model in Fluent, and further sets border
Condition and control parameter, and start to calculate；The file preserved after finally Fluent is solved is imported in Tecplot and carried out
Post processing, directly displays image or image is played to viewing frame by frame, Fluent preserves the specific data included in file
Also can call wherein.Take caliber D=25mm (not considering pipe thickness), leak is circular ideal, orifice diameter d=
10mm, leak pipeline center pressure are 0.4MPa, and environment and fuel gas temperature take 300K.Calculated using leakage model for small holes, and
Determined using transient simulation mode.Can initializes to primary condition and boundary condition after arrangement above is completed, so
Set step-length to carry out simulation calculating afterwards, straight tube is related in the present invention, the simulation of T rows pipe and complicated pipe has carried out altogether 500 steps receipts
Hold back.
2.2nd, straight tube and T tube models are established and picture exports：
It is conceptual modelling (conceptual modeling, CM) using two kinds of modeler models, one, it is mainly used to describe
The generalities structure of one unit.Using conceptual data model, database designer can in the incipient stage of design,
Main attention is used to understand and describe real world, and some the technical problems for being related to DBMS are postponed till design rank
Section goes to consider.The CM conceptual modelling functions that the present invention uses are effective supplements of two-dimentional sketch and 3 d geometric modeling and complete
It is kind；It is effective supplement of two-dimentional sketch and 3 d geometric modeling and perfect；Two be parametric modeling (Parametric
Modeling, PM), parametric modeling is parameter (variable) rather than numeral is established and the model of analysis, by simply changing
New model just can be established and analyzed to parameter value in model.The parameter of parametric modeling can be not only geometric parameter, also may be used
To be the property parameters such as temperature, material.In the geometric modeling system of parametrization, the sphere of action of design parameter is geometry mould
Type.Set using parameter modification and functional relation come the adjustment of implementation model size, save the substantial amounts of modeling work time.
The present invention uses both approaches, and carrys out practical operation modeling procedure by straight tube, T rows pipe and complicated pipe.Using numerical method
When solving governing equation, all it is to try every possible means to carry out governing equation on area of space discrete, then solves obtained discrete side
Journey group.Want the discrete in spatial domain, it is necessary to use grid.Develop a variety of discrete to the progress of each region
To generate the method for grid, grid generation technique is referred to as.When the problem of different, uses different numerical solutions, required net
Case form, which has, necessarily to be distinguished, but the method for generating grid is substantially coincident.At present, grid separation structure grid and non-knot
The major class of network forming lattice two.Simply, structured grid spatially compares specification, is such as often to a quadrilateral area, grid
Column distribution is embarked on journey into, line and alignment are obvious.And there is no obvious line in spatial distribution to unstrctured grid
And alignment.
2.2.1, straight tube pipeline internal model is established and picture exports：
The illustraton of model before straight tube is not revealed is first established, because model and model before leakage after leakage, let out except adding one
Dew point parameter, remaining basic parameter is identical, and for straight tube, the pipe that T is managed under these simple scenarios only establishes model before its leakage,
Laid a solid foundation to be established for the model of following complicated pipe；In complicated pipe, the mould after leakage before it is revealed specifically is established
Type, to export picture for the data analysis of next step.
Straight tube pipeline is most common a kind of situation in gas pipeline, therefore first establishes straight tube pipeline model.Choose straight tube
Pipe range 1000mm, diameter 25mm combustion gas (main component is methane) pipeline are as research object, and straight tube internal diameter is ignored, with 1m/
S speed is flowed into, the model established before straight tube does not leak, and specific straight tube simulation is illustrated in fig. 1 shown below；
The DM modules that straight tube model is carried by ANSYS are established, and are drawn directly according to Fig. 1 illustrated dimensions using Gambit softwares
Pipe two dimensional model figure, specific straight tube two dimensional model figure are illustrated in fig. 2 shown below；
Then in the attempting of workbench, mesh generation is carried out, as a result straight tube mesh generation is as shown in Figure 3；
Solve and set in fluent, after having calculated, make the pressure cloud atlas before leakage, speed cloud atlas；By tonogram
As can be seen that straight tube inlet pressure is maximum, overpressure tapers into flowing, minimum to reaching during outlet.
By with experimental result contrast and the Gambit requirements to mesh quality in itself, grid division.Mesh generation is complete
After, specified boundary condition types and zoning type, specific boundary condition are arranged in Fluent and carried out, finish with
Mesh files are exported and preserved by upper work can.
Pipeline A specific method after leakage and operation are identical with before leakage, therefore the not model after leakage is established herein,
Can directly it be drawn analyze data in next step.
2.2.2, T pipelines internal model is established and picture exports：
T rows pipe mainly studies the situation of gas pipeline junction, under study for action, chooses T-shaped pipe range pipe pipe range 1000mm,
Short tube pipe range 500mm, diameter 25mm combustion gas (main component is methane) pipeline are ignored as research object, T row bores,
Flowed into 1m/s speed, specific T rows tube model is as shown in Figure 4；
Solve and set in Fluent, after having calculated, make the pressure cloud atlas before leakage, speed cloud atlas, by tonogram
As can be seen that in T row pipe T fonts junction, pressure has significant change, and pressure significantly increases at pressure ratio smooth flow.
There are significant change, and speed ratio smooth flow in T row pipe T fonts junction, speed it can be seen from hodograph
It is that speed significantly increases.
The foundation of complicated pipeline model and picture output before and after 2.3 leakages：
2.3.1 model is established before complicated pipeline internal leakage：
Complexity pipe is the simplification of actual gas pipeline, there is a straight tube, the basis of T row pipes, can establish the mould of complicated pipeline
Type.Choose natural gas line and as shown above, and choose complicated pipe pipe as complicated pipe research object, the true pipeline of natural gas
Road shape as shown in the figure (size marking is as follows), diameter 25mm combustion gas (main component is methane) pipeline as research object,
T row bores are ignored, and are flowed into 1m/s speed, and model is as shown in Figure 5 before specific complicated pipe leakage；
The DM modules that complicated tube model is carried by ANSYS are established, and are drawn using Gambit softwares according to Fig. 5 illustrated dimensions
Straight tube two dimensional model figure, two dimensional model figure is as shown in Fig. 6 before specific complicated pipe leakage；
In the attempting of workbench, mesh generation is carried out, for plane and axisymmetric flow field problem, it is only necessary to
Generate surface grids.For three-dimensional problem, surface grids also can be first divided, then are extended to body, establish is two-dimentional combustion due to the present invention
Feed channel is simulated, so pertaining only to surface grids.Mesh generation is as shown in Figure 7 before specific complicated pipe leakage；
3.3.2, internal simulation after complicated pipe leakage：
Two dimensional model figure is as shown in Figure 8 after specific complicated pipe leakage；Two dimensional model figure is such as after specific complicated pipe leakage
Shown in Fig. 9；In the attempting of workbench, mesh generation is carried out, as a result as shown in Figure 10.
3rd, fuel gas pipeline leakage Numerical Value Result Analysis：
3.1st, CFD numerical simulation results are analyzed：
Because gas pipeline starts to leak moment, fuel gas flow is non-stable, so being entered with unstable state to gas leakage
Row sunykatuib analysis, changed with time rule with observing natural gas line internal leakage.Present invention analysis is with pipeline pressure P=
0.4MPa, caliber D=25mm, leak the methane concentration distribution rule under labor steady state of flow exemplified by the d=10mm of aperture
Rule.From straight tube, the simulation drawing of T rows pipe and complicated pipe can see, after gas leakage, the methane concentration near pipe internal leakage mouth
Very big, but increase over time, because combustion gas and air have density contrast, the speed of leakage is slowly stablized, speed and
Concentration decline quickly, finally slowly tends towards stability.The present invention is mainly on the basis of second step, according to fluent software moulds
Intend the data being calculated, analyze the influence of its leakage factor (pipeline pressure and the aspect of pipe diameter two), and obtain a result.
3.2 numerical simulation results are analyzed：
Fired below with pipeline pressure P=0.4MPa, caliber D=25mm, leakage aperture d=10mm for model labor
After feed channel leakage, the change of internal pipe pressure and speed.
Analog result importing Tecplot now is carried out into post processing can be to obtain molar fraction of methane etc. at different moments
It is worth line distribution, equality of temperature is with depressing, and the volume that identical mole of gas accounts for is same, so the molar fraction of methane is equal to methane
Mass fraction.
(1) internal simulation result after straight pipeline leakage：
Choose straight tube pipe range 1000mm, diameter 25mm, combustion gas (main component is methane) pipeline that leakage aperture is 10mm
As research object, straight tube internal diameter is ignored, and is flowed into 1m/s speed, is simulated after specific straight tube leakage as shown in figure 11：
Scaled residual plot is made using ANSYS14.0；Post-processing makes in straight tube pipeline methane concentration at any time
Between variation diagram；Figure is leaked by straight tube, it is clear that the change of methane concentration over time, occurs obvious in leakage point
Change, at the 125th second, leakage point was gradually stablized；
(2) internal simulation result after T pipe leakages：
As shown in figure 12, T-shaped pipe range pipe pipe range 1000mm, short tube pipe range 500mm, diameter 25mm are chosen, leakage aperture is
10mm combustion gas (main component is methane) pipeline is ignored as research object, T row bores, is flowed into 1m/s speed, tool
The leakage simulation of body T rows pipe is as shown in figure 12；
The DM modules that T rows tube model is carried by ANSYS are established, and in the attempting of workbench, carry out mesh generation, should
Scaled residual plot is made with ANSYS14.0；Post-processing makes methane concentration in T row pipelines and changes over time figure；
Schemed by T row pipe leakages, the change of methane concentration over time, significant change occurs in leakage point, was leaked at the 125th second
Point is gradually stable.
(3) internal simulation result after complicated pipe leakage：
Due to having built up illustraton of model, so directly being analyzed on the basis of second step.
Scaled residual plot is made using ANSYS14.0, carries out 576 steps altogether；Solve and set in fluent, meter
After having calculated, the pressure cloud atlas before leakage, speed cloud atlas are made；
Comprehensive analysis, by upper figure straight tube, the pipeline interior flow field before the leakage of T rows pipe and after the leakage of complicated pipe is analyzed
Go out main conclusions：Before leakage, internal pipe pressure vector, velocity is maximum in entrance, gradual with the flowing of combustion gas
Diminish, it is minimum to reaching during outlet；After revealing, its internal pressure vector, velocity varies widely, when it
In leakage point, significant change can all occur for pressure and speed, over time, change in the methane concentration of leakage point
It is gradually stable.
3.3rd, pipe leakage influence factor：
Influence natural gas leaking factor it is a lot, specifically describe as shown in such as following table 3-1 (specifically mainly from pipeline pressure,
The aspect of leakage hole size two is studied, and gas is assumed to methane in pipe, actual fluent simulations option elect as methane-
Air)；
The influence factor of table 3-1 gas pipeline leakages
3.3.1 pipeline pressure changes the influence to leakage：
Gas pipeline conveys the distance difference of natural gas and the difference of paving mode because residing environment is different so that
The design pressure of its pipeline is not quite similar.Long-distance transmission pipeline pressure is higher, but typically not over 3.6Mpa, and city
Internal natural gas transportation due to consideration that building is intensive, typically changing by the reason such as personnel activity's complexity, discharge pressure
Between 0.2-0.4Mpa, and the mode for conveying then low pressure for entering the civil natural gas such as residential building is carried out.It follows that pipeline
Pressure is one of important indicator of natural gas line conveying, therefore the pass between researching natural gas Release and dispersion and pipeline pressure
It is particularly important to the safe construction of pipe network and quick row Check.This simulation mainly for the fuel gas pipeline leakage situation in city,
Therefore main research pipeline pressure fuel gas pipeline leakage situation in the range of 0.5Mpa or so.Simulate a diameter of 25mm day
During right feed channel rupture (d=25mm), the pressure under the asynchronous leakage situation of pressure, (the present invention selection of speed cloud atlas
Pipeline entry pressure is 2kpa, 0.3Mpa, 0.4Mpa, and 3 kinds of different inlet pressure gas pipelines are simulated, and (face is simulated
Complicated pipe studied), while set to other specification is unified：Gas pipeline diameter 25mm, leak bore dia 10mm).
When pipeline entry pressure is 2kpa：The concentration of entrance is maximum at the beginning, increases over time, concentration is slow in pipe
Slow increase, during to 450 steps (125s), concentration reaches maximum in pipe.It is warm in pipeline junction temperature step-down, remainder pipe
Degree is very average.
In Practical Project, pipeline pressure is bigger, easier generation leakage accident, and now temperature and speed in pipeline
Equivalent also increases therewith.Therefore, pipeline that be larger to pressure rating carries out strict management, usually to strengthen for pipe
The maintenance work in road.
3.3.2 influence of the varying aperture to leakage, is leaked：
When pipeline pressure is certain, and leak aperture is smaller, leaked into the unit interval at leak in soil environment
Combustion gas gas mass flow reduce, so as to which range of scatter in same time in soil is smaller, the danger zone of leakage
It is smaller.And conversely, leakage aperture is bigger, area with high mercury proportion also increases around leak.Therefore when pipeline have compared with
During gross leak hole, its leak condition is more dangerous.
So it could be assumed that, in Practical Project, strengthen management and protection to gas pipeline, reduction is let out to try one's best
Small opening footpath is comparatively more intuitively to prevent the relatively effective measures that pipeline accident occurs.
On the whole, it is right according to analog result figure by the numerical simulation to being revealed before and after gas pipeline interior flow field
The various factors for influenceing gas pipeline leakage is analyzed, and so as to draw a conclusion, to prevent pipeline leakage accident, and is
Investigation after accident occurs provides theoretical foundation.
Present embodiment has following features：
(1) according to CFD Fluid Mechanics Computation knowledge, fuel gas pipeline leakage is simulated with Fluent, by straight tube, T rows
The leakage concentration of pipe and complicated pipe is showed with picture, and theoretical foundation is provided for later research.
(2) according to Hydrodynamics Theory, the characteristics of analysis obtains gas pipeline interior flow field before and after fuel gas pipeline leakage.
According to Hydrodynamics Theory, the characteristics of analysis obtains gas pipeline interior flow field before and after fuel gas pipeline leakage.Can be with by tonogram
Find out, straight tube inlet pressure is maximum, and overpressure tapers into flowing, minimum to reaching during outlet；In T row pipe T fonts
Junction, pressure has significant change, and pressure significantly increases at pressure ratio smooth flow.Combustion gas is let out with the progress of leakage
Area with high mercury proportion also increases around small opening.
(3) according to CFD Fluid Mechanics Computation knowledge, the fuel gas pipeline leakage under different leak conditions is simulated, entered
Mouth pressure is bigger, then easier generation leakage accident；It is bigger to leak aperture, area with high mercury proportion around leak
Increase.
It is obvious to a person skilled in the art that the invention is not restricted to the details of above-mentioned one exemplary embodiment, Er Qie
In the case of without departing substantially from spirit or essential attributes of the invention, the present invention can be realized in other specific forms.Therefore, nothing
By from the point of view of which point, embodiment all should be regarded as exemplary, and be nonrestrictive, the scope of the present invention is by institute
Attached claim rather than described above limit, it is intended that will fall in the implication and scope of the equivalency of claim
All changes include in the present invention.Any reference in claim should not be considered as to the involved right of limitation
It is required that.
Moreover, it will be appreciated that although the present specification is described in terms of embodiments, not each embodiment is only
Comprising an independent technical scheme, this narrating mode of specification is only that for clarity, those skilled in the art should
When using specification as an entirety, the technical solutions in the various embodiments may also be suitably combined, forms people in the art
The other embodiment that member is appreciated that.
Claims (2)
1. fuel gas pipeline leakage is to the method for numerical simulation of internal flow, it is characterised in that：Its analogy method is as follows：
Step 1：Establish simulation softward：
After the completion of modeling, mesh generation is carried out；It can be divided into following 3 step using the simulation of FLUENT softwares：(1), pre-treatment rank
Section, is completed with Gambit；(2) stage, is solved, is completed with fluent；(3), post-processing stages, completed with tecplot；
Completed in pretreatment stage using front processor Gambit softwares, wherein the unstructured grid generation program contained is phase
Grid is generated to the geometry of complexity, it can generate grid under two-dimensional geometry body and three-dimensional geometry body, but manually generated
Grid it is smaller than the grid number generated in software, also can be smaller in the consumption of internal memory；And simulate the processing unit calculated
Divide-solve the stage to use Fluent softwares, operation includes selection solution equation, setting fluent material and physical property, setting border ginseng
Number and solution control parameter, solve discrete equation, result visualization；For post-processing stages, for the net of no local cypher
Lattice can be post-processed using tecplot, and for there is the grid of local cypher to use the post-processing function carried in Fluent
Handled；
Step 2：Fuel gas pipeline leakage models and simulation analysis：
2.1st, FLUENT numerical simulation calculations and operation：
Analog simulation is carried out using Fluent, the first step carries out the foundation of physical model in Gambit, then carries out grid
Division, the selection of boundary condition is set, after exporting Mesh files, can be carried out in next step；Second step selects to solve in Fluent
Equation, required model, and further conditions setting and control parameter, and start to calculate, obtaining a result can be carried out in next step
Operation；The file that 3rd step preserves after Fluent is solved is imported in Tecplot and post-processed；
2.1.1, FLUENT solvers and setting：
Fluent provides two kinds of solver types, and a kind of is the solver based on pressure, and another kind is the solution based on density
Device；Using the solver based on pressure；
2.1.2, FLUENT running environment is set：
In the setting for opening the running environment of Fluent softwares, it can be seen that need to set two choosings of calculating reference pressure and gravity
；In Fluent, pressure is relative to the relative pressure of operation reference pressure, that is, relative pressure；Reference pressure is
Atmospheric environmental pressure, is set to standard atmospheric pressure 101325Pa, and reference pressure position selection acquiescence point (0,0,0) is studied；
Setting above is realized in Fluent, then selects transient simulation in General again, gravity changes in leakage process
Change has a great influence for leakage process, therefore need to consider that gravity influences；Due to gas leakage speed, so opening
Gravity simultaneously sets the -9.8m/s that acceleration of gravity is Y direction2；
2.1.3FLUENT computation model selects：
When running environment is set, after the selection of solver form is fixed, selection computation model, it uses turbulence model, Ran Hou
Energy equation, k- ε equations and component transport equation are opened in Models, selects component delivery model, and it is methane to define component
And air；Because Fluent itself is accompanied with material database, so directly selecting；It is it is of course also possible to self-defined as needed
The parameter and attribute of new material or the existing material of modification；
2.1.4, FLUENT primary condition and boundary condition are set：
The primary condition that simulation calculates is set as：Before gas pipeline is in non-leak condition, concentration and speed are all zero, in flow field
Full of air and stable state is kept, after gas pipeline is in non-leak condition, pressure entrance 0.4Mpa, internal diameter is ignored, with
1m/s speed flows into；
2.1.5, FLUENT solves parameter setting：
Analog simulation is carried out using Fluent, the first step carries out the foundation of physical model, the division of grid, border in Gambit
The selection of condition；Second step selects to solve equation, required model in Fluent, and further conditions setting and control are joined
Number, and start to calculate；The file preserved after finally Fluent is solved is imported in Tecplot and post-processed, directly aobvious
Diagram picture plays image viewing frame by frame, and the specific data that Fluent preserves included in file can also be called wherein；
Just primary condition and boundary condition are initialized after being provided with, then set step-length to carry out simulation calculating；
2.2nd, straight tube and T tube models are established and picture exports：
It is conceptual modelling using 2 kinds of modeler models, one；Two be parametric modeling, with both approaches, and passes through straight tube, T row pipes
Carry out practical operation modeling procedure with complicated pipe；All it is to try every possible means to exist governing equation during using Numerical Methods Solve governing equation
Carry out discrete on area of space, then solve obtained discrete equation group；Want the discrete in spatial domain, it is necessary to make
Use grid；
2.2.1, straight tube pipeline internal model is established and picture exports：
The illustraton of model before straight tube is not revealed is first established, because model and model before leakage after leakage, except adding a leak point
Parameter, remaining basic parameter is identical, and for straight tube, the pipe that T is managed under these simple scenarios only establishes model before its leakage, in complexity
Guan Zhong, the model that specifically establish after the preceding leakage of its leakage, to be that the data analysis of next step exports picture；
Straight tube pipeline first establishes straight tube pipeline model；The DM modules that straight tube model is carried by ANSYS are established, and utilize Gambit softwares
Straight tube two dimensional model figure is drawn by straight tube pipeline model size is established；Then in the attempting of workbench, carry out grid and draw
Point；
Solve and set in fluent, after having calculated, make the pressure cloud atlas before leakage, speed cloud atlas；Can be with by tonogram
Find out, straight tube inlet pressure is maximum, and overpressure tapers into flowing, minimum to reaching during outlet；By being tied with experiment
Fruit contrasts and the Gambit requirements to mesh quality in itself, grid division；After mesh generation is completed, specified boundary condition class
Type and zoning type, specific boundary condition are arranged in Fluent and carried out, and finish above work can by Mesh files
Output preserves；
2.2.2, T pipelines internal model is established and picture exports：
Solve and set in Fluent, after having calculated, make the pressure cloud atlas before leaking, speed cloud atlas can be with by tonogram
Find out, in T row pipe T fonts junction, pressure has significant change, and pressure significantly increases at pressure ratio smooth flow；
The foundation of complicated pipeline model and picture output before and after 2.3 leakages：
2.3.1, model is established before complicated pipeline internal leakage：
The DM modules that complicated tube model is carried by ANSYS are established, and straight tube two dimensional model figure, tool are drawn using Gambit software sizes
Two dimensional model figure before body complexity pipe leakage；In the attempting of workbench, mesh generation is carried out；
3.3.2, internal simulation after complicated pipe leakage：Two dimensional model after the specific complicated pipe leakage of foundation；Then establish specific
Two dimensional model figure after complicated pipe leakage；In the attempting of workbench, mesh generation is carried out；
Step 3: fuel gas pipeline leakage Numerical Value Result Analysis：
3.1st, CFD numerical simulation results are analyzed：
On the basis of second step, the data being calculated are simulated according to fluent softwares, it is analyzed and reveals the influence of factor,
And obtain a result；
3.2nd, numerical simulation result is analyzed：
(1), internal simulation result after straight pipeline leakage：
Scaled residual plot is made using ANSYS14.0；Post-processing makes in straight tube pipeline methane concentration anaplasia at any time
Change figure；By straight tube leakage figure, it is clear that the change of methane concentration over time, occurs significant change in leakage point,
At the 125th second, leakage point was gradually stablized；
(2), internal simulation result after T pipe leakages：
The DM modules that T rows tube model is carried by ANSYS are established, and in the attempting of workbench, carry out mesh generation, application
ANSYS14.0 makes scaled residual plot；Post-processing makes methane concentration in T row pipelines and changes over time figure；By T
Row pipe leakage is schemed, the change of methane concentration over time, leakage point occur significant change, at the 125th second leakage point by
Gradually stablize；
(3), internal simulation result after complicated pipe leakage：
Due to having built up illustraton of model, so directly being analyzed on the basis of second step；Solve and set in fluent, calculated
Afterwards, the pressure cloud atlas before leakage, speed cloud atlas are made；
Comprehensive analysis, the pipeline interior flow field analysis before the leakage of T rows pipe and after the leakage of complicated pipe draw main conclusions：Revealing
Before, internal pipe pressure vector, velocity is maximum in entrance, is tapered into the flowing of combustion gas, to reaching during outlet
It is minimum；After revealing, its internal pressure vector, velocity varies widely, when it is in leakage point, pressure and speed
Significant change can all occur for degree, over time, gradually stable in the methane concentration change of leakage point；
3.3rd, pipe leakage influence factor：
3.3.1 pipeline pressure changes the influence to leakage：
In Practical Project, pipeline pressure is bigger, easier generation leakage accident, and now temperature and speed equivalent in pipeline
Increase therewith；
3.3.2 influence of the varying aperture to leakage, is leaked：
When pipeline pressure is certain, and leak aperture is smaller, the unit interval interior combustion leaked at leak in soil environment
Gas gas mass flow reduces, and so as to which the range of scatter in same time in soil is smaller, the danger zone of leakage is also smaller；
And conversely, leakage aperture is bigger, area with high mercury proportion also increases around leak.
2. fuel gas pipeline leakage according to claim 1 is to the method for numerical simulation of internal flow, it is characterised in that：
The turbulence model is standard k-ε turbulence model.
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