CN103646143B - A kind of method of LPG storage tank coating protection system performance analysis under fire hazard environment - Google Patents

Abstract

The invention discloses the method for LPG storage tank coating protection system performance analysis under a kind of fire hazard environment, its step is as follows: 1: the wavelet finite element model of LPG storage tank coating passive protection system performance evaluation under structure fire hazard environment, 2: the small echo finite elements of LPG storage tank coating passive protection system under structure fire hazard environment: 3: the overall small echo finite elements column of LPG storage tank coating passive protection system under structure fire hazard environment, 4: carry out numerical evaluation, 5: the experiment test carrying out fire hazard environment LPG storage tank coating protection system, 6: select best small echo finite elements by analysis result, 7: change the type of the type of fire, the materials and structures of coating and flame, carry out numerical analysis, thus the coating protection mechanism of LPG storage tank under fire hazard environment can be searched out, 8: existing LPG storage tank coating protection system is designed and optimized, thus the explosion hazard of LPG storage tank under fire hazard environment can be reduced.

Description

A kind of method of LPG storage tank coating protection system performance analysis under fire hazard environment

Technical field:

The present invention relates to LPG storage tank coating passive protection system under fire hazard environment, specifically, relating to the method for LPG storage tank coating protection system performance analysis under the fire hazard environment for analyzing coating passive protection system performance, adopting coupled soil wavelet finite element analytical approach.

Background technology:

Under fire hazard environment, LPG storage tank is exposed in flame, pressure in storage tank increases, the temperature of tank skin increases, intensity reduces simultaneously, after fire certain time, tank skin will produce breach, and inflammable and explosive LPG will leak, and will cause the blast of LPG storage tank, once produce the fire explosion of LPG storage tank, by destroying the equipment, buildings etc. of oil play, making oil play suffer huge economic loss, the injures and deaths of personnel seriously in situation, will be caused, meanwhile, the fire explosion of LPG storage tank also can cause the pollution of environment.Therefore, be necessary that the loss taking the anti-guarantor's measure of corresponding safety that the fire explosion of LPG storage tank is produced reduces high minimum.

Fire is all generally burst accident, situation is very urgent, and therefore, under the effect of Initiative Defence System, still some can not be moistening for the outside surface of LPG storage tank shell, when spray equipment pressure is under-supply even cannot start due to fault time, just do not reach the object of moistening LPG storage tank outside surface.Therefore, under fire hazard environment, the setting of passive LPG fire prevention system is very necessary, fireproofing passiveness system can make LPG storage tank shell keep low state within the time that fire continues several hours by the coating acting on LPG storage tank outside surface, thus LPG storage tank can be made to be in the state of a safety, for fireman's fire extinguishing that is on the scene provides rescue time.

Under fire hazard environment, the explosion hazard of LPG storage tank depends primarily on the change of LPG temperature and pressure in tank and the change of LPG storage tank shell stress.When internal pressure and storage tank shell stress have exceeded the strength degree of tank skin, storage tank will crack, and the LPG of leakage runs into naked light and will light, and causes further rie, if do not lighted steam cloud formation density being greater than air, running into naked light will blast; Especially, when LPG storage tank generation entirety is broken, boiling liquid expanding-vapor explosion will be there is.Under fire hazard environment, the temperature and pressure of gas phase LPG, the temperature and pressure of liquid phase LPG and the temperature of solid storage tank shell and stress have very important impact for the danger of storage tank, and there is cross influence effect, and there is a lot of influence factors, such as, the intensity of flame, the characteristic of LPG medium, the concentration of flue gas, the materials and structures etc. of wind direction and storage tank, therefore, the Changing Pattern of LPG temperature and pressure and tank skin stress in storage tank should be studied, thus effectively can analyze coating fireproofing passiveness mechanism, the flameproof effect of coating fireproofing passiveness system can be studied exactly, guarantee the security of LPG storage tank under fire hazard environment.

In recent years, domestic and international related science man have studied the thermodynamics response storage tank fire hazard environment from different angles, and inquire into regard to the explosion-proof early warning mechanism of storage tank, but, report is rarely had to the research of the protective mechanism of storage tank coating passive protection system, therefore, under analysing in depth fire hazard environment, LPG storage tank coating fireproofing passiveness mechanism has very important theory significance for the security improving storage tank.Under fire hazard environment, the response pattern of LPG storage tank LPG temperature and pressure and storage tank shell stress under the protection of coating only relies on physical test to be more difficult, mainly be more difficult control around under fire hazard environment, such as, the concentration change of temperature, wind-force, flue gas has larger randomness etc.Therefore, the technology of numerical simulation of a kind of advanced person should be sought to carry out the research of storage tank coating fireproofing passiveness mechanism.The LPG of the liquid and gas under fire hazard environment in LPG storage tank and storage tank shell STRESS VARIATION have stronger non-linear, utilize traditional finite element technique to carry out numerical simulation and will produce numerical oscillation, and wavelet finite element technology has stronger advantage in process strong nonlinearity problem, utilize wavelet finite element to study efficiency and the accuracy that coating fireproofing passiveness mechanism can improve calculating.

Summary of the invention:

The invention provides the method for LPG storage tank coating protection system performance analysis under a kind of fire hazard environment, wavelet finite element theory is applied in the research of LPG storage tank coating fireproofing passiveness mechanism under fire hazard environment, wavelet finite element unit is constructed using wavelet function as interpolating function, the thermodynamics response model of LPG storage tank LPG under fire hazard environment is solved, and obtain the Changing Pattern of storage tank shell stress, and the thermodynamics of LPG storage tank inner LPG in fire hazard environment studied under the fireproofing passiveness system of different coating materials and structures and the response pattern of storage tank shell stress, thus optimum coating fireproofing passiveness system can be designed, guarantee the security of LPG storage tank under fire hazard environment.

A () utilizes mass-conservation equation, momentum conservation equation and energy conservation equation to build LPG tank inside LPG temperature-responsive model under fire hazard environment; RNGk-ε model is utilized to describe the turbulence model of LPG in LPG storage tank under fire hazard environment; Utilize VOF model to describe gas phase and liquid phase LPG diphasic flow, and utilize three parameter state equations to describe quality and the energy conversion of gas-liquid two-phase.Heat transfer is the major way that coating heat transmits, and then constructs the heat conduction model of coating, utilizes theory of elasticity to build LPG storage tank shell stress response model under corresponding fire hazard environment simultaneously.

B (), according to the actual conditions of LPG storage tank coating fireproofing passiveness system under fire hazard environment, the theoretical model built in integrating step (a), constructs corresponding small echo finite elements.Then, construct the wavelet finite element column of LPG storage tank coating fireproofing passiveness system under fire hazard environment, and utilize Lagrangian method to solve wavelet finite element column.

C () builds LPG storage tank coating fireproofing passiveness test macro under fire hazard environment, the pressure of LPG utilizes pressure transducer to test, the temperature of LPG utilizes temperature sensor to test, and the stress of LPG storage tank shell utilizes strain gauge to test, and test macro as shown in Figure 1.

By test result and wavelet finite element simulation result are compared, the correctness of checking wavelet finite element method.Then, carry out the convergence of Wavelet finite element method, find out degree of accuracy the highest, the small echo finite elements that solution procedure is the most stable, thus accuracy and the stability of calculating can be improved.

C () utilizes wavelet finite element technology to further investigate LPG storage tank coating fireproofing passiveness mechanism under fire hazard environment, respectively to LPG storage tank under different fire hazard environment, the temperature and pressure Changing Pattern of LPG tank inside LPG and the variation of stress of storage tank shell under different coating materials, different coating structures, different flame models, and carry out verification experimental verification, thus favourable theoretical foundation can be provided for the optimization of coating fireproofing passiveness system.

Advantage of the present invention is:

From point of theory, under fire hazard environment in LPG storage tank coating protection system performance analysis, the temperature and pressure of gas phase and liquid phase LPG and the change of storage tank shell temperature and stress all present stronger nonlinear characteristic, traditional finite element is utilized to solve to it defect that there will be numerical oscillation or even distortion, and the multiresolution analysis characteristic of wavelet analysis and finite element method closely combine by wavelet finite element technology, can select to analyze yardstick accordingly according to the Variation Features of physical quantity, thus the deficiency of conventional finite element when solving nonlinear problem can be made up, improve the precision and efficiency analyzed.

From application point, in depth study the response pattern can analyzing LPG storage tank LPG temperature and pressure and storage tank shell stress under coating fireproofing passiveness systemic effect preferably of LPG storage tank coating fireproofing passiveness mechanism under fire hazard environment, thus effectively can prevent LPG storage tank breaking out of fire explosion accident.And the influence factor of LPG storage tank coating passive protection mechanism is a lot of under LPG storage tank Fire Conditions, therefore, a large amount of numerical experiments should be carried out, the temperature and pressure of the LPG of LPG storage tank under fire hazard environment under different coating structure and composition and the stress response rule of storage tank shell are analyzed, thus rational coating passive protection system can be designed.

By the end of so far, the blast of LPG storage tank there occurs up to a hundred, and in explosion accident, have people's injures and deaths up to ten thousand, economic loss is huge, and in addition, in blast process, the poison gas of release seriously pollutes environment.Therefore, the Changing Pattern of wavelet finite element to LPG tank inside LPG temperature, pressure and tank skin stress in fire hazard environment under coating fireproofing passiveness systemic effect is utilized to study, effectively can analyze LPG storage tank coating passive protection mechanism under fire hazard environment, can ensure that fire hazard environment LPG storage tank can keep safety at certain hour, thus provide the time for fireman's fire extinguishing that is on the scene, and then can avoid exploding the injures and deaths of the economic loss that causes and personnel due to LPG storage tank.

Accompanying drawing explanation

LPG storage tank coating passive protection system Performance Test System under Fig. 1 fire hazard environment of the present invention.

1 data acquisition system (DAS) 2 temperature sensor 3 pressure transducer 4 strain gauge

5LPG storage tank shell

The technology path of Fig. 2 the present invention research.

The physical model of Fig. 3 LPG storage tank

1 gas phase 2LPG storage tank 3 coating 4 liquid phase LPG

The top of storage tank is gas phase LPG, and the bottom of storage tank is liquid phase LPG, and storage tank outer wall is coating.

Embodiment:

This research mainly utilizes the method for simulation analysis and experimental test to disclose LPG storage tank coating fireproofing passiveness mechanism under fire hazard environment,

Step 1: the wavelet finite element model of LPG storage tank coating passive protection system performance evaluation under structure fire hazard environment

A () builds LPG tank temperature and the corresponding mathematical model of pressure.

RNGk-ε model is for analyzing under fire hazard environment LPG turbulent flow rule in tank, and Turbulent Kinetic mode is as follows:

$\frac{\∂k}{\∂t}+\frac{\∂\left(k{u}_i\right)}{\∂x_i}=\frac{1}{\mathrm{\ρ}}(\mathrm{\μ}+\frac{{\mathrm{\μ}}_T}{{\mathrm{\σ}}_k})\frac{\∂}{{\∂x}_j}\left(\frac{\∂k}{\∂x_j}\right)+\frac{G_k+S_k}{\mathrm{\ρ}}-\mathrm{\ϵ}---\left(1\right)$

The transmission equation of turbulent dissipation speed is as follows:

$\frac{\∂k}{\∂t}+\frac{\∂\left(\mathrm{\ϵ}{u}_i\right)}{\∂x_i}=\frac{1}{\mathrm{\ρ}}(\mathrm{\μ}+\frac{{\mathrm{\μ}}_T}{{\mathrm{\σ}}_{\mathrm{\ϵ}}})\frac{\∂}{\∂x_j}\left(\frac{\∂\mathrm{\ϵ}}{{\∂x}_j}\right)+C_1\frac{\mathrm{\ϵ}}{k}{G}_k-C_2\frac{{\mathrm{\ϵ}}^2}{k}---\left(2\right)$

In formula, G _krepresent Turbulent Kinetic item, its mathematical model is as follows:

G _k=2μ _TD _ijD _ij(3)

In formula, D _ijrepresent mean strain rate tensor, its mathematical model is as follows:

$D_{\mathrm{ij}}=\frac{1}{2}(\frac{{\∂u}_i}{\∂x_j}+\frac{\∂u_j}{\∂x_i})---\left(4\right)$

VOF model mainly comprises several model, respectively: continuity model, and momentum model and VOF convection model.Continuous model is as follows:

$\frac{\∂\stackrel{\→}{u}}{\∂x}+\frac{\∂\stackrel{\→}{v}}{\∂y}=0---\left(5\right)$

In formula, represent the speed component in x direction; represent the speed component in y direction.

X direction momentum model is as follows:

$\frac{\∂\stackrel{\→}{u}}{\∂t}+\frac{\∂\stackrel{\→}{u}\stackrel{\→}{u}}{\∂x}+\frac{\∂\stackrel{\→}{v}\stackrel{\→}{v}}{\∂x}=\frac{\∂}{\∂x}\left[2(\mathrm{\μ}+{\mathrm{\μ}}_T)\frac{\∂\stackrel{\→}{u}}{\∂x}\right]+\frac{\∂}{\∂y}\left[2(\mathrm{\μ}+{\mathrm{\μ}}_T)(\frac{\∂\stackrel{\→}{v}}{\∂x}+\frac{\∂\stackrel{\→}{u}}{\∂y})\right]-\frac{1}{\mathrm{\ρ}}\frac{\∂p}{\∂x}---\left(6\right)$

In formula, μ represents kinematic viscosity, μ _trepresent motion eddy viscosity, ρ represents the density of fluid.

Y direction momentum model is as follows:

$\frac{\∂\stackrel{\→}{v}}{\∂t}+\frac{\∂\stackrel{\→}{u}\stackrel{\→}{v}}{\∂x}+\frac{\∂\stackrel{\→}{v}\stackrel{\→}{v}}{\∂y}=\frac{\∂}{\∂y}\left[2(\mathrm{\μ}+{\mathrm{\μ}}_T)\frac{\∂\stackrel{\→}{v}}{\∂y}\right]+\frac{\∂}{\∂x}(\frac{\∂\stackrel{\→}{v}}{\∂y}+\frac{\∂\stackrel{\→}{u}}{\∂x})-\frac{1}{\mathrm{\ρ}}\frac{\∂p}{\∂y}+g---\left(7\right)$

In formula, g represents acceleration of gravity, and p represents mean pressure.

VOF convection model is as follows:

$\frac{\∂{\mathrm{\α}}_g}{\∂t}+u_i\frac{\∂{\mathrm{\α}}_g}{\∂x_i}=0---\left(8\right)$

$\frac{\∂{\mathrm{\α}}_l}{\∂t}+u_i\frac{\∂{\mathrm{\α}}_l}{\∂x_i}=0---\left(9\right)$

In formula, α _gand α _lrepresent the volume fraction of gas phase and liquid phase LPG respectively, u _irepresent speed component, x _idenotation coordination, i=x, y.

ρ=α _lρ _l+α _gρ _g(10)

μ=α _lμ _l+α _gμ _g(11)

μ _T=α _lμ _Tl+α _gμ _Tg(12)

The quality of gas-liquid two-phase and energy conversion utilize three parameter state equation analysis, and its expression formula is as follows:

$P=\frac{\mathrm{RT}}{v-b}-\frac{a\left(T\right)}{(v-0.5b)(v+3c)}---\left(13\right)$

In formula, a (T) represents the function of temperature, pressure and coefficient of excentralization, and b represents the function of temperature and pressure, and c represents the 3rd parameter.

The computing formula of these three parameters of a (T), b and ccan is as follows:

$a\left(T\right)={\mathrm{\Ω}}_a\frac{R^2{T}_c^2}{P_c}\mathrm{\α}\left(T\right)---\left(14\right)$

$b={\mathrm{\Ω}}_b\frac{R{T}_c}{P_c}---\left(15\right)$

$c={\mathrm{\Ω}}_c\frac{P_c{v}_c}{R{T}_c}---\left(16\right)$

Make a (T _c)=1, can obtain following equation:

${\mathrm{\Ω}}_a=3{\stackrel{\‾}{{\mathrm{\ξ}}_c}}^2-1.5{\mathrm{\Ω}}_b{\mathrm{\Ω}}_c+(3{\mathrm{\Ω}}_c-0.5{\mathrm{\Ω}}_b)({\mathrm{\Ω}}_b+1)---\left(17\right)$

${\mathrm{\Ω}}_b^3+(1.25-3\stackrel{\‾}{{\mathrm{\ξ}}_c}){\mathrm{\Ω}}_b^2+(3{\stackrel{\‾}{{\mathrm{\ξ}}_c}}^2-1.5{\stackrel{\‾}{{\mathrm{\ξ}}_c}}^2+0.5){\mathrm{\Ω}}_b-{\stackrel{\‾}{{\mathrm{\ξ}}_c}}^3=0---\left(18\right)$

$3{\mathrm{\Ω}}_c=1-3\stackrel{\‾}{{\mathrm{\ξ}}_c}+1.5{\mathrm{\Ω}}_b---\left(19\right)$

Wherein, Ω _bfor the least root of equation (18), computing formula as follows:

$\stackrel{\‾}{{\mathrm{\ξ}}_c}=0.329-0.077\mathrm{\ω}+0.021{\mathrm{\ω}}^2---\left(20\right)$

In formula, ω represents coefficient of excentralization.

B () builds coating heat conduction model

The heat conduction model of coating is as follows:

$\frac{{\∂}^{2}T}{\∂x^2}+\frac{{\∂}^{2}T}{\∂y^2}=0---\left(21\right)$

The boundary condition of heat transfer is as follows:

$-\mathrm{\λ}\frac{\∂T}{\∂\stackrel{\→}{n}}=\mathrm{\α}(T-T_f){|}_s---\left(22\right)$

In formula, α represents convective heat-transfer coefficient, W/ (m ²k); λ represents heat-conduction coefficient, W/ (mK); T _frepresent the temperature of environment, K; represent the normal vector on border.

C () builds the stress response model of storage tank shell

Under fire hazard environment LPG storage tank shell due to raise temperature will produce thermal expansion, and then generation thermal stress, the initial strain ε of LPG storage tank shell ₀can be calculated by formula below:

ε ₀=α(T-T ₀)[111000] ^T(23)

In formula, α represents thermal expansivity; T ₀represent the initial temperature of tank skin, K; T represents the transient temperature of tank skin under fire hazard environment, K.

Stress-strain relation is as follows:

$\stackrel{\→}{\mathrm{\σ}}=D(\stackrel{\→}{\mathrm{\ϵ}}-{\stackrel{\→}{\mathrm{\ϵ}}}_0)---\left(24\right)$

In formula, D represents elastic coefficient matrix.

The temperature-responsive model temperature solution of gas-liquid phase LPG and pressure solution are used as the initial value of LPG storage tank shell temperature and the calculating of stress response model, thus can effectively solve the coupling model of LPG tank temperature-pressure-stress gas-liquid-solid.

Step 2: the small echo finite elements of LPG storage tank coating passive protection system under structure fire hazard environment

By wavelet scaling function φ ¹(α) and φ ²(β) subspace is differentiated in generation more with , the tensor product of subspace can generate high order spatial, and expression formula is as follows:

$V_j=V_j^1\⊗V_j^2---\left(25\right)$

In formula, V _jrepresent tensor space, j=0,1 ..., N-1; represent Kronecker symbol, α and β represents local coordinate.

The form that wavelet scaling function on subspace can be expressed as:

High order spatial { V _jon scaling function can be expressed as:

Using wavelet scaling function as interpolating function, temperature funtion T (α, β) can be expressed as:

In formula, represent wavelet coefficient; (α, β) represents the local coordinate of small echo finite elements node, and it is as follows with the relation of overall coordinate (x, y, z):

$\mathrm{\α}=\frac{x-x_1}{x_2-x_1}---\left(30\right)$

$\mathrm{\β}=\frac{y-y_1}{y_2-y_1}---\left(31\right)$

In formula, x ₁and x ₂the minimum value of small echo finite elements x coordinate and maximal value; y ₁and y ₂represent minimum value and the maximal value of small echo finite elements y coordinate.

According to equation (21) and (22), the potential function of corresponding small echo finite elements can be obtained:

${\mathrm{\Π}}^e\left(T\right){\∫}_{\mathrm{Se}}\left\{\frac{\mathrm{\λ}}{2}\right[{\left(\frac{\∂T}{\∂\mathrm{\α}}\right)}^2+{\left(\frac{\∂T}{\∂\mathrm{\β}}\right)}^2\left]\right\}\mathrm{d\αd\β}+{\∫}_{\mathrm{\Γe}}\frac{1}{c_h}\frac{\∂T}{\∂n}\mathrm{dl}---\left(32\right)$

In formula, e represents small echo finite elements; S represents the volume of small echo finite elements; Γ represents the surface area of small echo finite elements.

Make δ Π ^e(T)=0 can obtain the corresponding differential equation:

$\underset{\mathrm{se}}{\∫\∫}\mathrm{\λ}(\frac{\∂W}{\∂\mathrm{\α}}\frac{\∂T}{\∂\mathrm{\α}}+\frac{\∂W}{\∂\mathrm{\β}}\frac{\∂T}{\∂\mathrm{\β}})\mathrm{d\αd\β}+\underset{\mathrm{\Γe}}{\∫}\frac{W}{c_h}\frac{\∂T}{\∂n}=0---\left(33\right)$

In formula, W represents weight function, and form is as follows: W _{m, n, l}=φ _m(α) φ _n(β)=Φ _m,n.

In formula, m and n represents the exponent number of wavelet scaling function, m and n=0,1,2 ..., N-2.

Equation (29) and (33) are updated to equation (32), the column of small echo finite elements can be obtained:

${\stackrel{\→}{N}}^e{\stackrel{\·\·}{\stackrel{\→}{a}}}^e+{\stackrel{\→}{K}}^e{\stackrel{\→}{a}}^e={\stackrel{\→}{P}}^e---\left(34\right)$

In formula, represent the differential coefficient column vector of unknown wavelet coefficient; represent the heat absorption capacity coefficient matrix of small echo finite elements; represent the heat transfer matrix of small echo finite elements; represent the thermal force matrix of small echo finite elements, corresponding expression formula is as follows:

${\stackrel{\→}{N}}_{m,n;i,j}^e={\∫}_0^1{\∫}_0^1\mathrm{\λ}{\mathrm{\Φ}}_{m,n}{\mathrm{\Φ}}_{i,j}\mathrm{d\αd\β}---\left(35\right)$

${\stackrel{\→}{K}}_{m,n;i,j}^e={\∫}_0^1{\∫}_0^1\mathrm{\λ}(\frac{\∂{\mathrm{\Φ}}_{m,n}}{\∂\mathrm{\α}}\frac{\∂{\mathrm{\Φ}}_{i,j}}{\∂\mathrm{\α}}+\frac{\∂{\mathrm{\Φ}}_{m,n}}{\∂\mathrm{\β}}\frac{\∂{\mathrm{\Φ}}_{i,j}}{\∂\mathrm{\β}})\mathrm{d\αd\β}+{\∫}_0^1{\∫}_0^1{\mathrm{\Φ}}_{m,n}{\mathrm{\Φ}}_{i,j}\mathrm{d\αd\β}---\left(36\right)$

${\stackrel{\→}{P}}_{m,n,l}^e={\∫}_0^1{\∫}_0^1\mathrm{\λ}{\mathrm{\Φ}}_{m,n}\mathrm{d\αd\β}+{\∫}_0^1{\∫}_0^1{\mathrm{\Φ}}_{m,n}{T}_f\mathrm{d\αd\β}---\left(37\right)$

Step 3: the overall small echo finite elements column of LPG storage tank coating passive protection system under structure fire hazard environment

By to the synthesis of cell matrix and the process of boundary condition, the small echo finite elements column of entire system can be obtained:

$\stackrel{\→}{N}\stackrel{\·\·}{\stackrel{\→}{T}}+\stackrel{\→}{K}\stackrel{\→}{T}=\stackrel{\→}{P}---\left(38\right)$

In formula, represent overall heat capacity matrix; represent overall heat transfer matrix; represent thermal force matrix.

Step 4: carry out numerical evaluation, the algorithm flow of coating wavelet finite element is as follows:

First, carry out the Initialize installation of algorithm, mainly comprise:

Step1: determine fire model (pond fire, jet bubble reactor and radiation fire), the starting condition of LPG storage tank under input fire hazard environment.The physical dimension of input LPG storage tank, the thermodynamic property parameter of LPG, the material property parameter (density, elastic modulus, Poisson ratio and coefficient of heat conductivity) of LPG storage tank shell; The composition of input coating and thickness, thermodynamic property parameter (coefficient of heat conductivity, specific heat, density, thermal diffusion coefficient).

Step2: the type (Daubechies small echo, B-spline small echo, the second small echo, Qu Bo and ridge ripple etc.) selecting wavelet function, the exponent number of input wavelet function.

Step3: according to matrix of coefficients N and K of formula (35) ~ (37) define system.

Step4: definition initial temperature vector T ₀.

Step5: select the time step △ t solved.

Step6: definition coefficient of efficiency matrix K, its expression formula is as follows:

$\stackrel{\‾}{K}=\frac{N}{\mathrm{\Δt}}+\mathrm{\ξK}---\left(39\right)$

In formula, ξ is the adjustment factor of computational accuracy.

Step7: triangle decomposition is carried out to coefficient of efficiency matrix K,

For each circulation, proceed as follows:

Step1: Heat of Formation load vectors P _n+1.

Step2: generate effectively vector expression formula is as follows:

${\stackrel{\‾}{Q}}_{n+1}=[\frac{N}{\mathrm{\Δt}}-(1-\mathrm{\λ})K]T_n+(1-\mathrm{\λ})P_n+\mathrm{\λ}{P}_{n+1}---\left(40\right)$

Step3: calculate T _n+1formula by following:

${\mathrm{LEL}}^T{\mathrm{\φ}}_{n+1}={\stackrel{\‾}{Q}}_{n+1}---\left(41\right)$

Secondly, the temperature and pressure of liquid and gas LPG is gone out according to LPG tank temperature and the corresponding calculated with mathematical model of pressure.

Finally, the stress of LPG storage tank shell under fire hazard environment is gone out according to the temperature variation of Tank and the pressure change calculations of gas phase LPG.

Step 5: the experiment test carrying out fire hazard environment LPG storage tank coating protection system, the result of test and wavelet finite element simulation result as shown in Figure 1, compare by experiment schematic diagram, the computational accuracy of checking wavelet finite element.

Step 6: the small echo finite elements being preferred for LPG storage tank coating protection system performance testing under fire hazard environment, the type and the exponent number that change wavelet function carry out convergence, select best small echo finite elements by analysis result.

Step 7: change the type of the type of fire, the materials and structures of coating and flame, carry out numerical analysis, thus the coating protection mechanism of LPG storage tank under fire hazard environment can be searched out.

Step 8: existing LPG storage tank coating protection system is designed and optimized, thus the explosion hazard of LPG storage tank under fire hazard environment can be reduced.

Claims (1)

1. the method for LPG storage tank coating protection system performance analysis under fire hazard environment, is characterized in that: its step is as follows: step 1: the wavelet finite element model building LPG storage tank coating passive protection system performance evaluation under fire hazard environment, comprising:

A () builds LPG tank temperature and the corresponding mathematical model of pressure: utilize model to describe under fire hazard environment LPG turbulent flow rule in tank; Utilize VOF mould to describe gas phase and liquid phase LPG diphasic flow, mainly comprise continuity model, momentum model, VOF convection model; Described quality and the energy conversion of gas-liquid two-phase by three parameter state equations, parametric equation is as follows:

(1)

In formula, represent the function of temperature, pressure and coefficient of excentralization, represent the function of temperature and pressure, represent the 3rd parameter;

B () builds coating heat conduction model

C () builds the stress response model of storage tank shell

Under fire hazard environment LPG storage tank shell due to raise temperature will produce thermal expansion, and then generation thermal stress, by calculating the initial strain of LPG storage tank shell , corresponding strees strain model can be built;

In the process solved, the temperature-responsive model temperature solution of gas-liquid phase LPG and pressure solution are used as the initial value of LPG storage tank shell temperature and the calculating of stress response model, thus can effectively solve the coupling model of LPG tank temperature-pressure-stress gas-liquid-solid;

Step 2: the small echo finite elements of LPG storage tank coating passive protection system under structure fire hazard environment:

By wavelet scaling function with generate and differentiate subspace more with , the tensor product of subspace can generate high order spatial, to provide respectively on subspace and wavelet scaling function on high order spatial;

Using wavelet scaling function as interpolating function, construct corresponding temperature funtion , derive the potential function of small echo finite elements, then derive the corresponding differential equation, finally can obtain small echo finite elements column;

Step 3: the overall small echo finite elements column of LPG storage tank coating passive protection system under structure fire hazard environment,

By to the synthesis of cell matrix and the process of boundary condition, the small echo finite elements column of entire system can be obtained;

Step 4: carry out numerical evaluation, the algorithm flow of coating wavelet finite element is as follows:

First, carry out the Initialize installation of algorithm, comprise: determine that fire model comprises pond fire, jet bubble reactor and radiation fire, the starting condition of LPG storage tank under input fire hazard environment, the physical dimension of input LPG storage tank, the thermodynamic property parameter of LPG, the material property parameter of LPG storage tank shell, density, elastic modulus, Poisson ratio and coefficient of heat conductivity; The composition of input coating and thickness, thermodynamic property parameter coefficient of heat conductivity, specific heat, density, thermal diffusion coefficient, select the type of wavelet function, Daubechies small echo, B-spline small echo, the second small echo, Qu Bo and ridge ripple, the exponent number of input wavelet function; The matrix of coefficients of define system; Definition initial temperature vector; Select the time step solved; Definition coefficient of efficiency matrix; To coefficient of efficiency matrix carry out triangle decomposition;

For each circulation, operation comprises: Heat of Formation load vectors; Generate effectively vector; Calculate the temperature circulated each time;

Secondly, the temperature and pressure of liquid and gas LPG is gone out according to LPG tank temperature and the corresponding calculated with mathematical model of pressure;

Finally, the stress of LPG storage tank shell under fire hazard environment is gone out according to the temperature variation of Tank and the pressure change calculations of gas phase LPG;

Step 5: the experiment test carrying out fire hazard environment LPG storage tank coating protection system, compares the result of test and wavelet finite element simulation result, the computational accuracy of checking wavelet finite element;

Step 6: the small echo finite elements being preferred for LPG storage tank coating protection system performance testing under fire hazard environment, the type and the exponent number that change wavelet function carry out convergence, select best small echo finite elements by analysis result;

Step 7: change the type of the type of fire, the materials and structures of coating and flame, carry out numerical analysis, thus the coating protection mechanism of LPG storage tank under fire hazard environment can be searched out;

Step 8: existing LPG storage tank coating protection system is designed and optimized, thus the explosion hazard of LPG storage tank under fire hazard environment can be reduced.