CN-121997829-A - Pipeline multiphase flow simulation method supporting slug flow

CN121997829ACN 121997829 ACN121997829 ACN 121997829ACN-121997829-A

Abstract

The invention discloses a pipeline multiphase flow simulation method supporting slug flow, and relates to the field of pipeline multiphase flow simulation. The method comprises the steps of geometric information input and grid generation, boundary and initial condition setting, physical parameter calculation and interpolation table construction, control equation dispersion and solving, time step control and convergence judgment. The method has the core improvement that sectional staggered grid modeling is adopted to adapt to complex geometric pipelines, a volume fraction self-adaptive correction mechanism is introduced to optimize a interphase drag model, the problem of drag underestimation under low volume fraction is solved, the volume fraction is corrected through a remapping strategy, and conservation is guaranteed. The invention has the advantages of considering calculation efficiency and prediction precision, avoiding numerical oscillation and divergence, being applicable to gas-liquid slug transient simulation of long-distance and complex geometric pipelines and providing support for optimization of pipeline systems and risk early warning.

Inventors

WANG DUO
ZHAO HONGGANG

Assignees

海仿(上海)科技有限公司

Dates

Publication Date: 20260508
Application Date: 20260128

Claims (8)

1. The pipeline multiphase flow simulation method supporting slug flow is characterized by comprising the following steps of: S1, inputting geometric parameters of a pipeline, dividing the pipeline into a plurality of geometric sections along the axial direction according to the characteristics of the cross section and the inclination angle of the pipeline, discretizing the geometric sections by adopting a staggered grid system containing a speed control body VCV and a pressure control body PCV, wherein the VCV is used for solving a momentum equation, the PCV is used for solving a mass/pressure/energy equation, and an inlet-outlet boundary is defined; S2, setting boundary and initial conditions, namely applying pressure or mass flow boundary conditions on the inlet and outlet boundary, and setting VCV speed distribution and PCV pressure, temperature and volume fraction initial fields at the initial moment; S3, physical parameter calculation and interpolation table construction, namely determining transport medium components, performing phase balance calculation, solving balance state parameters of each phase under different temperature and pressure, and constructing a rapid interpolation table; s4, discretizing and solving a control equation, namely constructing a closed one-dimensional control equation set based on a two-fluid model and a section average method, discretizing space and time, calculating wall friction force and interphase drag force, correcting, and judging convergence, wherein the corrected volume fraction after solving meets conservation constraint; and S5, controlling and ending the time step, namely dynamically updating the time step according to the stability condition, advancing the solving time, ending the calculation when the solving time reaches the preset ending time, and otherwise, returning to the S4 iteration.
2. The method of claim 1, wherein the geometric parameters in S1 include a total number of geometric segments, an inner diameter/outer diameter/length/inclination angle/material property of each segment, when the inner diameter of each adjacent geometric segment is changed, the area mutation is treated by utilizing gas-liquid two-phase flux conservation, the height of each VCV center point is calculated according to the inclination angle of the pipeline, and when the VCV is positioned at the connection of geometric segments with different inclination angles, the volume of the VCV in the two segments is used as the gravity term in the interpolation weight calculation momentum equation.
3. The method of claim 1, wherein the closed one-dimensional control equation set in S4 includes a continuity equation, a momentum equation, an energy equation, and a pressure equation, specifically as follows: continuity equation: ; momentum equation: ; Energy equation: ; The pressure equation: ; Wherein, the At the collection Represents a certain phase of gas or liquid; Time, distance along the process, volume fraction, density, flow rate, pressure, internal energy and enthalpy, respectively; Respectively, the gravity constants are that the pipeline is Height and pipe inclination angle; The phase change rates are respectively the phase change rates, Friction between the phase and the pipe wall, Relative to each other Phase-to-phase drag and tube wall heat transfer rate; The phase change rate is calculated by Bendiksen model, the interphase drag force and the pipe wall friction force can be constructed by hydraulic model in pipeline flow, and the expression is: ; ; Wherein the method comprises the steps of 、 The volume of the VCV and the contact area between the gas phase and the wall surface, the gas phase and the liquid phase and the contact area between the liquid phase and the wall surface in the VCV are respectively; 、 The friction coefficient and reynolds number, respectively.
4. The method of claim 3, wherein the interphase drag force in S4 employs a volume fraction adaptive correction mechanism by first establishing correction parameters The expression is: ; Correcting the inter-phase friction coefficient ; C is an empirical constant calibrated by a bayesian optimization algorithm, preferably c=0.01.
5. The method of claim 4, wherein the correcting the volume fraction in S4 after each iteration step is completed is performed by a remapping strategy, expressed as: 。
6. The method of claim 1, wherein the spatial discretization in S4 is implemented by using a finite volume method, the flux of the flow term surface is configured by using a windward format, the pressure gradient is configured by using a central differential format, the linear equation set is solved by using a catch-up method, and the time discretization is implemented by using an implicit Euler format, and the decoupling of pressure and momentum is implemented by using a SIMPLE algorithm.
7. The method of claim 1, wherein the equilibrium state parameters in S3 include phase density, viscosity, mass fraction, partial derivative of density with respect to temperature and pressure, phase fraction, specific heat capacity, and heat transfer coefficient, and wherein when the physical parameters in S4 are updated, the PCV is traversed to calculate the gas-liquid two-phase viscosity at the VCV center point by linear interpolation using Flash Table update parameters.
8. The method of claim 1, wherein the convergence criterion in S4 is that each initial residual of the set of linear equations is less than a predetermined threshold.

Description

Pipeline multiphase flow simulation method supporting slug flow Technical Field The invention relates to the technical field of pipeline multiphase flow simulation, in particular to a pipeline multiphase flow simulation method supporting slug flow, which is suitable for gas-liquid slug flow transient simulation of long-distance and complex geometric pipelines in the industrial fields of petroleum exploitation, chemical industry and the like. Background The application of the pipeline transportation multiphase fluid is wide in the fields of petroleum exploitation, chemical industry and other industries. In long-distance conveying or large-dip-angle pipelines, slug flow is a typical unsteady flow type, and is represented by the fact that gas-liquid two phases alternately form high-speed liquid plugs and bubble clusters, so that pressure and flow in the pipelines are severely fluctuated, conveying efficiency is reduced, equipment vibration and corrosion are easily caused, even safety accidents are aggravated, and therefore accurate prediction and effective control of the slug flow are very important. The existing pipeline transient multiphase flow simulation is mainly divided into a three-dimensional simulation technology and a one-dimensional simulation technology. The three-dimensional simulation technology can capture gas-liquid interface dynamic and local flow details with high precision, but has the advantages of high consumption of calculation resources and long time consumption, is difficult to be suitable for full-scale simulation of industrial-grade long-distance pipelines, reduces calculation complexity through section average treatment based on a simplified framework of a two-fluid model and the like, is suitable for long-distance transportation pipeline engineering application, and has obvious defects that firstly, the conservation of phase volume fraction is difficult to ensure, the easy deviation of the gas-liquid two-phase volume fraction is 1, numerical oscillation is caused, even divergence is solved, secondly, a friction pressure drop model highly depends on experience parameters, errors are large under the strong unsteady and nonuniform flow pattern of slug flow, prediction accuracy and robustness are influenced, thirdly, complicated geometric adaptability is insufficient, the traditional method assumes that the pipeline is uniform and straight pipe, complex topologies such as dip angle mutation and sectional area change are difficult to process, and generation and propagation characteristics of slug flow under real working conditions cannot be accurately reflected. Disclosure of Invention Aiming at the problems that the existing one-dimensional simulation technology has poor conservation of phase volume fraction, a friction pressure drop model depends on empirical parameters and complex geometric adaptability is insufficient in slug flow simulation, the invention provides a pipeline multiphase flow simulation method supporting slug flow, and the simulation accuracy and numerical stability are improved. The invention solves the technical problems through the following technical proposal, which comprises the following steps: S1, inputting geometric parameters of a pipeline, dividing the pipeline into a plurality of geometric sections along the axial direction according to the characteristics of the cross section and the inclination angle of the pipeline, discretizing the geometric sections by adopting a staggered grid system containing a speed control body VCV and a pressure control body PCV, wherein the VCV is used for solving a momentum equation, the PCV is used for solving a mass/pressure/energy equation, and an inlet-outlet boundary is defined; S2, setting boundary and initial conditions, namely applying pressure or mass flow boundary conditions on the inlet and outlet boundary, and setting VCV speed distribution and PCV pressure, temperature and volume fraction initial fields at the initial moment; S3, physical parameter calculation and interpolation table construction, namely determining transport medium components, performing phase balance calculation, solving balance state parameters of each phase under different temperature and pressure, and constructing a rapid interpolation table; s4, discretizing and solving a control equation, namely constructing a closed one-dimensional control equation set based on a two-fluid model and a section average method, discretizing space and time, calculating wall friction force and interphase drag force, correcting, and judging convergence, wherein the corrected volume fraction after solving meets conservation constraint; and S5, controlling and ending the time step, namely dynamically updating the time step according to the stability condition, advancing the solving time, ending the calculation when the solving time reaches the preset ending time, and otherwise, returning to the S4 iteration. Further, the geometric parameters in S1 comprise the tota