Search

CN-121747727-B - Small flame modeling method considering curvature and differential diffusion for hydrogen-rich fuel flashback

CN121747727BCN 121747727 BCN121747727 BCN 121747727BCN-121747727-B

Abstract

The invention discloses a small flame modeling method considering curvature and differential diffusion aiming at hydrogen-rich fuel tempering, and belongs to the field of energy and combustion engineering. The method comprises the steps of utilizing ULF software to solve a one-dimensional premixed small flame equation to establish a database, mapping the database to a control parameter space (mixing fraction, process variable, enthalpy and hydrogen mass fraction) through an OpenFOAM mapping program, wherein the hydrogen mass fraction characterizes a curvature effect, introducing a difference diffusion term when solving a control parameter equation set, and obtaining a thermochemical variable through table lookup. According to the invention, the influence of the curvature effect and the differential diffusion effect on the tempering process is considered for the first time, and the hydrogen mass fraction is used as a curvature agent variable, so that the tempering speed prediction precision is remarkably improved. The number of solving equations is reduced through dimension reduction treatment, the calculation efficiency is improved while the accuracy is ensured, and the method is suitable for tempering process simulation of all gas fuels.

Inventors

  • WEN XU
  • Yan Yunxiao

Assignees

  • 中国科学技术大学

Dates

Publication Date
20260508
Application Date
20260226

Claims (10)

  1. 1. A method of modeling a small flame for hydrogen rich fuel flashback that takes into account curvature and differential diffusion, comprising the steps of: step 1, solving a one-dimensional premixed small flame equation to obtain a laminar flow small flame database under different working conditions; step 2, mapping the laminar small flame database to a control parameter space by using a mapping program, wherein the control parameter space comprises a mixing fraction, a process variable, enthalpy and a hydrogen mass fraction, the mixing fraction represents an equivalent ratio, the process variable represents a reaction progress, the enthalpy represents heat loss, and the hydrogen mass fraction represents curvature; Step 3, designing a calculation domain and dividing grids according to experimental data to establish a discretization mathematical model, solving an equation set comprising a control parameter equation set, a density equation, a speed equation and a pressure equation, adding a difference diffusion term when solving the control parameter equation set, acquiring components, temperature, a chemical reaction source term and the difference diffusion term through looking up a small flame table, and carrying out pressure correction.
  2. 2. The method for modeling a small flame considering curvature and differential diffusion for hydrogen-rich fuel flashback according to claim 1, wherein in the step 1, the one-dimensional premixed small flame equation comprises a component equation, a temperature equation and a reaction progress gradient variable equation, and the working conditions comprise different temperatures, different equivalence ratios and different curvatures.
  3. 3. The method for modeling a small flame considering curvature and differential diffusion for hydrogen rich fuel flashback as defined in claim 1, wherein in the step 2, the process variables are component mass fractions of key products and key reactants, the hydrogen mass fraction is used for characterizing curvature effects, and flame thickening factors, efficiency factors and flame detector coefficients are calculated and stored in a mapping process.
  4. 4. The method of modeling a small flame for hydrogen rich fuel flashback taking into account curvature and differential diffusion according to claim 1, wherein in step 3, the differential diffusion term is solved separately and mapped to a control parameter space during the mapping process.
  5. 5. The method of modeling a small flame for hydrogen rich fuel flashback taking into account curvature and differential diffusion of claim 1, wherein step 3 comprises: Step 3.1, designing a calculation domain and dividing grids; Step 3.2, discretizing the mathematical model to obtain an equation set; step 3.3, solving a density equation and a speed equation to obtain a density and speed estimated value; Step 3.4, solving a control parameter equation set to obtain a control parameter predicted value; Step 3.5, looking up a small flame table to obtain a thermochemical variable; Step 3.6, solving a pressure equation and carrying out pressure-speed correction; And 3.7, judging convergence or ending time, otherwise, advancing a time step and repeating the steps 3.3-3.6.
  6. 6. The method of modeling a small flame for hydrogen rich fuel flashback taking into account curvature and differential diffusion of claim 5, wherein the expression of the control parameter equation set is: , Wherein, the Is the amount of spatial averaging that is performed, Represents the average quantity of Farve, Is the density; The method comprises the steps of obtaining variables to be solved, wherein the variables comprise process variables, mixing fractions, hydrogen mass fractions and enthalpy; Refers to a gradient operator; representing a velocity vector; representing time, E is an efficiency factor, F is a thickening factor, Is a flame detector; Is the term of differential diffusion, Wherein Is the difference in the diffusion coefficient and, Is the diffusion coefficient at the sub-grid scale, Is the specific heat capacity of constant pressure, Is the thermal conductivity; is the source item corresponding to the variable.
  7. 7. The method of modeling a small flame for hydrogen rich fuel flashback, taking into account curvature and differential diffusion of claim 6, In the enthalpy equation is the thermal diffusivity In the remaining equations are mass diffusion coefficients , And 0 in the enthalpy equation and the mixed fraction equation.
  8. 8. The method of modeling a small flame for hydrogen rich fuel flashback, taking into account curvature and differential diffusion according to claim 1, wherein in step 3, the mixing score is calculated using Bilger mixing score formula: , Wherein, the 、 And The partial mixing fractions of carbon element, hydrogen element and oxygen element are respectively, the subscripts fu and ox respectively represent pure fuel and pure air fluid, 、 And Representing the relative atomic masses of the elements carbon, hydrogen and oxygen.
  9. 9. The method of modeling a small flame for hydrogen rich fuel flashback taking into account curvature and differential diffusion of claim 1, wherein the process variable is carbon monoxide mass fraction Mass fraction with carbon dioxide And (2) sum: C is a process variable.
  10. 10. The method of modeling a small flame for hydrogen rich fuel flashback taking into account curvature and differential diffusion as defined in claim 1, wherein the method is applicable to numerical simulation of flashback process for all gaseous fuels.

Description

Small flame modeling method considering curvature and differential diffusion for hydrogen-rich fuel flashback Technical Field The invention belongs to the field of energy and combustion engineering, and particularly relates to a small flame modeling method considering curvature and differential diffusion for hydrogen-rich fuel tempering. Background Along with the continuous increase of the demand of reducing carbon emission in the world, hydrogen energy is widely focused and discussed due to the characteristics of cleanliness, high energy density and the like, but because the flame propagation speed of hydrogen combustion is very fast, the hydrogen is extremely easy to generate tempering phenomenon in the application process, and once tempering occurs, great damage is generated to a burner, and casualties can be caused in severe cases, so that how to reduce the occurrence of tempering is realized, and understanding of the tempering occurrence process becomes a place of important attention of researchers. In the field of energy and combustion engineering at present, a solution modeling process of a tempering process generally adopts a large vortex simulation method of computational fluid mechanics, a combustion model selects a limited chemical reaction rate model, and a table-building simplified model comprising a detailed limited chemical reaction rate model, a small flame model and the like is adopted, and compared with the detailed limited chemical reaction model, the small flame model replaces a component equation set by solving a control parameter equation set, so that the number of solved equations is reduced, the consumption of computational resources is reduced, and the time for solving and calculating is shortened. In the tempering process, the differential diffusion effect and the curvature effect have great influence on the flame structure and the tempering speed, the differential diffusion effect can influence the component distribution and further influence the content of fuel, so that the chemical reaction speed and the flame structure are changed, the fuel can be preferentially diffused to a positive curvature area, higher equivalent ratio and temperature can be formed in the positive curvature area, and the negative curvature area is just opposite, so that the curvature effect can influence the flame structure and the tempering speed. So considering the curvature effect and the differential diffusion effect improves the accuracy of the prediction of the tempering process by researchers, but at present, no method simultaneously considers the differential diffusion effect and the influence of the curvature effect in the tempering process. Disclosure of Invention In order to overcome the defects of the prior art, the invention provides a small flame modeling method which considers curvature and differential diffusion for tempering hydrogen-rich fuel, and simultaneously considers the influence of curvature effect and differential diffusion effect in the tempering process. The invention solves the tempering process by using the small flame model, uses the hydrogen mass fraction to represent the curvature, considers the curvature effect in the tempering process, and can reproduce the tempering process with higher precision and faster calculation rate. The invention realizes high-precision numerical solution of the tempering process of the hydrogen-rich fuel, and can process the numerical solution of the tempering process of all gas fuels. In order to achieve the above purpose, the invention adopts the following technical scheme: A small flame modeling method considering curvature and differential diffusion for hydrogen-rich fuel flashback comprises the following steps: step 1, solving a one-dimensional premixed small flame equation to obtain a laminar flow small flame database under different working conditions; step 2, mapping the laminar small flame database to a control parameter space by using a mapping program, wherein the control parameter space comprises a mixing fraction, a process variable, enthalpy and a hydrogen mass fraction, the mixing fraction represents an equivalent ratio, the process variable represents a reaction progress, the enthalpy represents heat loss, and the hydrogen mass fraction represents curvature; Step 3, designing a calculation domain and dividing grids according to experimental data to establish a discretization mathematical model, solving an equation set comprising a control parameter equation set, a density equation, a speed equation and a pressure equation, adding a difference diffusion term when solving the control parameter equation set, acquiring components, temperature, a chemical reaction source term and the difference diffusion term through looking up a small flame table, and carrying out pressure correction. Compared with the prior art, the invention has the beneficial effects that: The small flame model considering curvature and differential diffusion firs