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CN-121766210-B - Numerical calculation method for calculating hydrogen-ammonia mixing turbulence combustion stretching rate

CN121766210BCN 121766210 BCN121766210 BCN 121766210BCN-121766210-B

Abstract

The invention discloses a numerical calculation method for calculating a hydrogen-ammonia mixing turbulence combustion stretching rate, and belongs to the field of clean energy combustion numerical simulation calculation. The method comprises the steps of constructing a small flame database based on a one-dimensional reactant-product equation and combining strain rate parameterization, mapping the database to a track variable space of a mixing fraction, a reaction progress variable and a normalized hydrogen mass fraction to generate a small flame lookup table, adopting a large vortex simulation solution control equation, obtaining components, a chemical source item, a differential diffusion item and a tensile rate item through the lookup table, and quantifying the differential diffusion effect and the tensile effect through priori verification and posterior verification comparison experimental data. According to the invention, the small flame model is expanded and optimized, so that the difference diffusion effect is considered, and meanwhile, the stretching effect is further considered, so that the mass fraction distribution of main components in the hydrogen-ammonia blending premix flame can be accurately predicted, and theoretical support is provided for the design and optimization of the hydrogen-ammonia burner.

Inventors

  • WEN XU
  • GAO BINGQIAN

Assignees

  • 中国科学技术大学

Dates

Publication Date
20260508
Application Date
20260302

Claims (8)

  1. 1. A numerical calculation method for calculating a hydrogen-ammonia blending turbulent combustion stretch ratio, comprising: Step 1, constructing a small flame database based on a one-dimensional reactant-product equation and in combination with strain rate parameterization; Step 2: mapping the small flame database to a track variable space of a mixing fraction, a reaction progress variable and a normalized hydrogen mass fraction, generating a small flame lookup table, wherein the normalized hydrogen mass fraction is used as a track variable for representing a stretching effect, and the normalized hydrogen mass fraction is used as a target variable for representing a stretching effect , Is the mass fraction of hydrogen The mixed fractional area exceeding the flammability limit is calculated by extrapolation, and the small flame lookup table comprises efficiency factors, thickening factors and flame sensor parameters of the artificial thickening flame model; Step 3, adopting large vortex simulation to solve a control equation, obtaining components, chemical source items, differential diffusion items and stretching rate items through table lookup, and substituting the components, the chemical source items, the differential diffusion items and the stretching rate items into the control equation for iterative solution until convergence; And 4, comparing experimental data through priori verification and posterior verification, quantifying a difference diffusion effect and a stretching effect, directly inputting the experimental data into a small flame lookup table through priori verification, comparing output components with the experimental data, and comparing the experimental data with the experimental data through large vortex simulation output results through posterior verification.
  2. 2. The numerical calculation method for calculating a turbulent combustion elongation of hydrogen-ammonia blending according to claim 1, wherein in step 1: The equivalent ratio covers the global equivalent ratio of 1.6 of the hydrogen-ammonia blending experimental condition; The strain rate covers the upper and middle branches of the sigmoid curve to characterize the stretching effect.
  3. 3. The numerical calculation method for calculating a turbulent combustion elongation of hydrogen-ammonia blending according to claim 1, wherein in step 2: Mixing fraction The method comprises the following steps: ; Wherein, the And The partial mixing fractions of the hydrogen element and the oxygen element in the main components, For the elemental hydrogen to be of relative atomic mass, The elemental oxygen relative atomic mass, subscript ox is the oxidant stream, subscript fuel is the fuel stream; reaction progress variable mass fraction Defined as the mass fraction of water 。
  4. 4. The numerical calculation method for calculating a turbulent combustion elongation of hydrogen-ammonia blending according to claim 1, wherein in step 3: The control equation includes the component transport equation: ; Wherein, the And Respectively an efficiency function, a thickening factor and a flame sensor, Is the diffusion coefficient, extracted from a small flame look-up table with/without differential diffusion/stretching effects, t is time, In order to achieve an average density of the particles, For the solution in the i-direction, Is the sub-grid vortex diffusivity, the main component k is selected as H 2 、NH 3 、H 2 O and O 2 , For its corresponding Farve average mass fraction of the main component k, Is the Farve average speed in the i direction, For Farve average source terms of component k, Is the amount of spatial averaging that is performed, Representing the Farve average quantity obtained by large vortex simulation solution.
  5. 5. The numerical calculation method for calculating a hydrogen-ammonia blending turbulent combustion stretching ratio according to claim 1, wherein the differential diffusion effect quantization formula in step 4 is: ; Wherein, the Items and items The terms are diffusion terms in the principal component equations respectively, Is a defined differential diffusion parameter.
  6. 6. The numerical calculation method for calculating a turbulent combustion elongation of hydrogen-ammonia blending according to claim 1, wherein the elongation effect quantization formula in step 4 is: ; Wherein, the In order to be a term of the elongation, In order to be a term of the strain rate, Is a curvature term, wherein, In order to achieve a flame displacement velocity, Is a curvature.
  7. 7. The numerical calculation method for calculating a turbulent combustion elongation of hydrogen-ammonia blending according to claim 1, wherein in step 3: The calculation domain adopts a cylindrical structure and comprises a central hydrogen-ammonia fuel jet flow, an annular pilot nozzle and an outer nitrogen isolation area, and the grid is of a non-orthogonal structure.
  8. 8. The numerical method for calculating a turbulent combustion draw ratio for hydrogen-ammonia blending according to claim 1, wherein a hydrogen-ammonia blending mechanism comprising 31 components and 203 reactions is employed in step 1.

Description

Numerical calculation method for calculating hydrogen-ammonia mixing turbulence combustion stretching rate Technical Field The invention belongs to the field of clean energy combustion numerical simulation calculation, and particularly relates to a numerical calculation method for calculating a hydrogen-ammonia mixing turbulence combustion stretching rate. Background Today, the problem of carbon emissions from conventional fossil fuels is of great concern, and the study of clean energy is becoming urgent. However, ammonia, one of the clean energy sources, has zero carbon emission potential, but is also facing a series of challenges to be addressed, such as low flammability, low radiation intensity, and high nitrogen oxide emissions. Research shows that by mixing and burning ammonia with hydrogen partially cracked, characteristics similar to those of methane fuel can be achieved, and the above challenges are solved to a certain extent. However, in a turbulent hydrogen-ammonia premixed flame of high intensity, the flame is pushed into the thin reaction zone of the premixing zone, and strong stretching effects in the form of curvature and strain are expected to occur, with a large impact on flame structure and flame characteristics, creating a great challenge in modeling the premixed hydrogen-ammonia turbulent flame. Therefore, in order for such a hydrogen-ammonia blending flame having a remarkable stretching effect to function safely and efficiently in an energy system, it is important to calculate the stretching ratio in turbulent combustion of hydrogen-ammonia blending by a numerical method. At present, the solution modeling process of hydrogen-ammonia blending combustion generally adopts a large vortex simulation method of computational fluid mechanics, and for premixed flames, a small differential diffusion flame model is adopted to predict component distribution changes caused by different hydrogen and ammonia diffusivities in combination with an artificial thickening flame model, however, the process ignores stretching effects. In addition, for some models that consider the stretching effect, such as scalar dissipation ratio based on progress variables, OH mass fraction, H radical mass fraction, or H 2 mass fraction, all used to simulate methane or hydrogen flame, it was not fully validated in hydrogen-ammonia-blending flames with strong differential diffusion effects, i.e., no method currently can consider both differential diffusion and the effect of stretching in a hydrogen-ammonia-blending turbulent premix flame. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a technical scheme of a numerical calculation method for calculating the hydrogen-ammonia mixing turbulence combustion stretching rate. According to the invention, the differential diffusion small flame model considering the stretching ratio is coupled with the artificial thickening flame model, and the mass fraction of main components in the hydrogen-ammonia mixing turbulence premixed flame is simulated and predicted by combining a detailed chemical reaction mechanism. The technical scheme of the invention is as follows: a numerical calculation method for calculating a hydrogen-ammonia blending turbulent combustion stretch ratio, comprising the steps of: Step 1, constructing a small flame database based on a one-dimensional reactant-product equation and in combination with strain rate parameterization; Step 2, mapping the database to a track variable space of the mixing fraction, the reaction progress variable and the normalized hydrogen mass fraction to generate a small flame lookup table; Step 3, adopting large vortex simulation to solve a control equation, and obtaining components, chemical source items, differential diffusion items and stretching rate items through table lookup; And 4, comparing experimental data through priori verification and posterior verification, and quantifying a differential diffusion effect and a stretching effect. In the above technical solution, in step 1: The equivalent ratio covers the global equivalent ratio of 1.6 of the hydrogen-ammonia blending experimental condition; The strain rate covers the upper and middle branches of the sigmoid curve to characterize the stretching effect. In the above technical solution, in step 2: Mixing fraction The method comprises the following steps: Wherein, the AndThe partial mixing fractions of the hydrogen element and the oxygen element in the main components,For the elemental hydrogen to be of relative atomic mass,The elemental oxygen relative atomic mass, subscript ox is the oxidant stream, subscript fuel is the fuel stream; reaction progress variable mass fraction Defined as the mass fraction of water; Normalized hydrogen mass fraction,Is the mass fraction of hydrogenIs a maximum value of (a). In the above technical solution, in step 2: Performing extrapolation calculation on a mixed fraction area exceeding the flammability limit;