CFD-based combustion chamber staged air supply structure optimization method

Abstract

The invention relates to the technical field of combustion chamber air supply structures, in particular to a CFD-based combustion chamber graded air supply structure optimization method. Three key tuyere design parameters including the height, the length and the included angle of a secondary air inlet are systematically optimized by establishing a three-dimensional model of a coke oven combustion chamber and utilizing CFD numerical simulation, the optimal value of each parameter is determined by adopting a control variable method to reduce the nitrogen oxide concentration of an outlet and improve the longitudinal temperature uniformity of a flame path as targets, and the optimal value of the secondary air inlet is calculated. Finally, the nitrogen oxide emission is greatly reduced under the optimal parameter combination, meanwhile, the temperature distribution in the flame path is more uniform, a local high-temperature area is avoided, the combustion efficiency is improved, and the environmental pollution is reduced; the technical problems that in the prior art, how specific structure parameters of a secondary air system of a coke oven combustion chamber affect flowing in a vertical flame path of a coke oven, and research on combustion and NOx generation mechanisms is not sufficient, so that the content of NOx discharged in the coke oven combustion chamber is large, and temperature distribution is not uniform are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of combustion chamber air supply structure, and particularly relates to a combustion chamber staged air supply structure optimization method based on CFD. BACKGROUND

[0002] Coke is an indispensable raw material in the steel industry. China, as the world's largest coke producer, has a huge annual constant. However, the coke production process is accompanied by serious air pollution. Nitrogen oxides (NOx) are one of the main environmental pollutants. Long-term exposure to NOx can cause respiratory diseases and may form acid rain. The coke oven combustion chamber is the main area of NOx generation. The high-temperature combustion process is the key to the formation of NOx. In order to reduce the generation of NOx in the combustion process, the main measures usually taken include reducing the average combustion temperature, avoiding local high temperature and reducing the oxygen concentration in the reaction zone. The current mainstream low-oxygen combustion technology includes fuel staging, air staging and flue gas recirculation, etc. Among them, the air staging technology is concerned due to its low cost, strong compatibility and accurate control. It creates a poor oxygen condition in the main combustion zone by sending combustion air into the combustion zone in stages, and inhibits the generation of thermal NOx.

[0003] Although the air staging technology shows potential in reducing NOx, its effect depends largely on the structural parameters of the secondary air system, such as the secondary air height, the inlet size and the incident angle, etc. Existing researches are mostly focused on the overall influence of air staging on NOx emission, and the specific structural parameters of the secondary air system on the flow, combustion and NOx generation mechanism in the coke oven vertical fire channel are not fully studied, resulting in more NOx emission and uneven temperature distribution in the coke oven combustion chamber. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a combustion chamber staged air supply structure optimization method based on CFD, which solves the technical problem that the specific structural parameters of the secondary air system of the coke oven combustion chamber affect the flow, combustion and NOx generation mechanism in the coke oven vertical fire channel, resulting in more NOx emission and uneven temperature distribution in the coke oven combustion chamber.

[0005] To solve the above technical problems, the present application provides the following technical scheme: a combustion chamber staged air supply structure optimization method based on CFD, including a fire channel as a combustion chamber, and a primary air inlet, a secondary air inlet, a coke oven gas inlet and an outlet arranged in the fire channel. The optimization method includes the following steps: A coke oven combustion chamber three-dimensional model is established according to a target coke oven vertical fire channel. The secondary air inlet includes three adjustable air port design parameters, i.e. the secondary air inlet height from the bottom of the fire channel, the length of the inlet channel and the included angle between the inlet and the fire channel wall. CFD is constructed based on the three-dimensional model of the combustion chamber of the coke oven, and the grid is divided, the boundary conditions are set, and the control equation is configured; Taking the reduction of the concentration of nitrogen oxides at the outlet of the three-dimensional model of the combustion chamber of the coke oven and the improvement of the longitudinal temperature uniformity of the flue as the optimization objectives, the optimal values of three tuyere design parameters, i.e., the inlet height of the secondary air, the length of the inlet channel, and the included angle between the inlet and the flue wall, are obtained through the control variable method; CFD simulation verification is performed according to the optimal values of the three tuyere design parameters, and the optimal values of the three tuyere design parameters are determined according to the verification effect.

[0006] As preferred, the specific steps of the grid division are: The calculation domain of the three-dimensional model of the combustion chamber of the coke oven is discretized by using a structured grid mainly composed of hexahedrons; A number of key flow regions in the three-dimensional model of the combustion chamber of the coke oven are determined, and local grid refinement is performed to obtain a number of grid models with different grid numbers; The outlet temperature, the average heating wall temperature, and the concentration of nitrogen oxides at the outlet under a number of different grid numbers are compared, and the grid model with the relative error of each parameter being lower than the error threshold is selected for subsequent simulation.

[0007] As preferred, the boundary conditions include: The preheating temperature of the coke oven gas and the preheating temperature of the combustion air are set; The fuel inlet and the primary air inlet are set as mass flow inlets, and the fuel mass flow and the mass ratio of the primary air to the total air are set respectively; The secondary air inlet is set as a mass flow inlet, and the mass ratio of the secondary air to the total air is set, and the sum of the mass ratio of the primary air to the total air and the mass ratio of the secondary air to the total air is 1; The outlet can be set as a pressure outlet, and all the walls at the outlet are set as no-slip walls; A certain numerical heat flux density is applied to the heating wall surface close to the carbonization chamber The top and bottom walls close to the carbonization chamber are set as heat dissipation surfaces, and a numerical heat flux density less than is applied The remaining walls close to the carbonization chamber are set as adiabatic.

[0008] As preferred, the control equation includes: The turbulent flow equation is used to simulate the turbulent flow combined with the extendable wall function; The non-premixed combustion model is used to simulate the turbulent combustion process of the coke oven gas and air, and the component concentration is determined by solving the mixture fraction transport equation; The discrete coordinate model is used to simulate the radiation heat transfer at high temperature; Based on Zeldovich mechanism, a thermal NO generation model is set up; A steady-state solver based on pressure is adopted, the pressure-velocity coupling adopts the SIMPLE algorithm, and the momentum and energy equations adopt the second-order upwind format discretization.

[0009] As preferred, the turbulent flow equation is Realizable k-ε turbulent flow equation.

[0010] As preferred, the specific steps of obtaining the optimal values of the three air port design parameters of the secondary air inlet height, the length of the inlet channel and the angle between the inlet and the fire channel wall by the control variable method are as follows: The length L of the secondary air inlet channel and the angle a between the inlet and the fire channel wall are fixed as two air port design parameters, and a plurality of secondary air inlet heights h with different values are set for CFD simulation; The height h of the secondary air inlet and the angle a between the inlet and the fire channel wall are fixed as two air port design parameters, and a plurality of lengths L of the secondary air inlet channel with different values are set for CFD simulation; The height h of the secondary air inlet and the length L of the secondary air inlet channel are fixed as two air port design parameters, and a plurality of angles a between the inlet and the fire channel wall with different values are set for CFD simulation; According to the highest temperature in the fire channel, the outlet nitrogen oxide concentration, the temperature standard deviation and the bottom temperature of the fire channel in the simulation results, the optimal values of the three air port design parameters of the secondary air inlet height, the length of the inlet channel and the angle between the inlet and the fire channel wall are obtained.

[0011] The application also provides a CFD-based combustion chamber staged air supply structure optimization system, comprising a processor and a memory, the memory is used for storing a computer program, and the computer program is executed by the processor to realize the CFD-based combustion chamber staged air supply structure optimization method.

[0012] Through the above technical scheme, the application provides a CFD-based combustion chamber staged air supply structure optimization method, which has at least the following beneficial effects: 1、The application establishes a three-dimensional model of a coke oven combustion chamber and uses CFD numerical simulation to systematically optimize three key air port design parameters of the height, length and angle of the secondary air inlet, so as to reduce the outlet nitrogen oxide concentration and improve the longitudinal temperature uniformity of the fire channel, determine the optimal values of the parameters by using the control variable method, and finally realize a significant reduction in nitrogen oxide emission under the optimal parameter combination, and the temperature distribution in the fire channel is more uniform, local high-temperature zones are avoided, the combustion efficiency is improved, and environmental pollution is reduced, and the method replaces the traditional experiment by numerical simulation, significantly reduces the optimization cost and time, and provides an efficient and reliable technical means for industrial application.

[0013] 2. This invention uses a structured grid to locally refine key flow regions, and combines grid independence verification to ensure simulation accuracy. At the same time, it reasonably sets boundary conditions, including mass flow inlet, pressure outlet, and walls with different heat flux densities, to accurately reflect the actual flow and heat transfer conditions in the combustion chamber. This refined pre-processing setting effectively improves the reliability of CFD simulation, lays a solid foundation for parameter optimization, and makes the final optimized results more practical in engineering. It can stably achieve the goals of low nitrogen emissions and uniform temperature field in practical applications.

[0014] 3. This invention, by configuring an advanced system of governing equations, including a Realizable k-ε turbulence model, a non-premixed combustion model, a discrete coordinate radiation model, and a NO generation model based on the Zeldovich mechanism, and using the SIMPLE algorithm and a second-order upwind scheme for solution, accurately describes the flow, combustion, and pollutant generation processes within the combustion chamber. This complete physical model can precisely capture key physical phenomena, and by combining the control variable method to systematically analyze the influence of each parameter, it achieves the best balance in multi-objective optimization, providing a reliable theoretical basis and technical support for developing efficient and low-pollution combustion chamber air supply structures. Attached Figure Description

[0015] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the physical model of the coke oven flue of the present invention; Figure 2 This is a schematic diagram of the mesh independence verification structure of the present invention; Figure 3 This is a schematic diagram showing the temperature distribution, O2 mole fraction distribution, and NO mole fraction distribution of the YOZ section and XOZ section in the fire channel at different secondary air inlet heights. Figure 4 The curves showing the changes in the maximum temperature inside the flue and the NO concentration at the outlet under different secondary air inlet heights; Figure 5 The curves showing the variation of average temperature and standard deviation of temperature at the bottom 0.5-meter section of the fire duct at different secondary air inlet heights are presented. Figure 6 The temperature distribution, turbulent kinetic energy distribution, and NO mole fraction distribution at the YOZ section of the flue are shown for different secondary air inlet lengths. Figure 7 The curves show the changes in secondary air inlet velocity and average flue gas velocity in the flue under different secondary air inlet lengths. Figure 8The outlet NO concentration and the standard deviation of the flue temperature change curve under different secondary air inlet lengths; Figure 9 The temperature distribution of the YOZ section, the H2 molar fraction distribution of the XOZ section and the NO molar fraction distribution in the flue under different secondary air inlet angles; Figure 10 The highest temperature in the flue and the outlet NO concentration change curve under different secondary air inlet angles. DETAILED DESCRIPTION

[0016] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below in combination with the drawings and specific embodiments. The implementation process of how to apply technical means to solve technical problems and achieve technical effects can be fully understood and implemented.

[0017] Coke oven site experiments face challenges such as high temperature, long cycle and parameter delay. In order to solve the technical problems that the existing technology does not fully study how the specific structural parameters of the secondary air system of the coke oven combustion chamber affect the flow, combustion and NOx generation mechanism in the vertical flue of the coke oven, resulting in more NOx emissions and uneven temperature distribution in the coke oven combustion chamber, the present application provides a combustion chamber staged air supply structure optimization method based on CFD. The CFD (Computational Fluid Dynamics Model) numerical simulation is used as a powerful tool for in-depth understanding and optimization of the coke oven combustion process, so as to obtain a systematic and accurate optimization method. The method can be used for parameterized modeling, multi-physical field simulation and sensitivity analysis of the key geometric parameters of the coke oven combustion chamber staged air supply structure, especially the secondary air inlet, so as to determine the optimal structure configuration. Under the premise of ensuring the quality of coke, the minimization of NOx emission and the uniformization of temperature distribution are realized. The method accurately optimizes the height, length and angle of the secondary air inlet through parameterized modeling, systematic CFD simulation and multi-objective evaluation, so as to effectively reduce the NOx emission of the coke oven combustion chamber and improve the uniformity of its temperature distribution. The following takes a 6-meter-high coke oven chamber vertical flue as the research object to specifically explain the detailed steps of the present application: S1: According to the target coke oven vertical flue, a coke oven combustion chamber three-dimensional model is established, and the height, length and angle of the secondary air inlet are all set as adjustable parameters: Firstly, the accurate geometric dimensions of the target coke oven vertical flue are collected, please refer to Figure 1As shown, a schematic diagram of a coke oven vertical flue physical model is shown, wherein (a) is the original vertical flue structure, (b) is the air staged combustion chamber structure with the addition of the secondary air inlet, the total height of the flue is 5100mm, composed of the ascending flue and the descending flue, connected by the upper cross-hole and the lower circulating window, and the combustion chamber bottom is provided with a primary air inlet with a size of 72mm x 120mm, a coke oven gas (COG) inlet with a diameter of 50mm, and an outlet located in the side wall of the descending flue.

[0018] Based on the above dimensions, a three-dimensional entity model of the vertical flue can be established using software such as three-dimensional SpaceClaim, and then a secondary air inlet is created on the inner side wall of the ascending flue. The key structural parameters of the secondary air inlet include the secondary air inlet height (h) from the bottom of the flue, the length (L) of the inlet channel, and the angle (a) between the inlet and the flue wall. These three parameters are set as independent design variables, i.e. adjustable design parameters. Through parameterization driving, these design variables can be easily modified to generate different geometric models for subsequent simulation analysis. After the model is established, necessary simplification can also be performed to ensure the quality of the subsequent mesh and the calculation efficiency.

[0019] S2: Set up a computational fluid dynamics model, including mesh division, boundary condition setting and control equation configuration; The coke oven combustion chamber three-dimensional model constructed in S1 step is imported into icem software for mesh division. The calculation domain can be discretized using structured mesh mainly composed of hexahedron. Then several key flow regions in the coke oven combustion chamber three-dimensional model are determined, such as the coke oven gas inlet, primary air inlet, secondary air inlet and outlet, etc. Local mesh encryption is then performed to obtain several grid models with different grid quantities. Subsequently, mesh independence verification is performed, and the outlet temperature, average heating wall temperature and outlet nitrogen oxide concentration (taking NO concentration as an example) under several different grid quantities are compared, Figure 2 The grid independence verification structure diagram is shown, which gives the outlet temperature, average heating wall temperature and outlet NO concentration under four different grid quantities (93.7 million, 139.4 million, 237.3 million and 334.1 million). According to the figure, when the grid quantity reaches 237.3 million, the relative error of each parameter is less than the error threshold, for example, the error threshold is set to 1%. At this time, the grid model is selected for all subsequent simulations to balance the calculation accuracy and efficiency.

[0020] The boundary conditions are set as follows: the coke oven gas can be preheated to a gas preheating temperature, such as about 50℃, and the combustion air can be preheated to an air preheating temperature, such as about 1100℃. The fuel inlet and the primary air inlet are set as mass flow inlets, and the fuel mass flow can be set to 7.02kg / h, and the primary air accounts for about 50% (mass ratio) of the total air. The secondary air inlet can also be set as a mass flow inlet, and the remaining 50% of the air is provided, i.e., the secondary air accounts for about 50% (mass ratio) of the total air, i.e., the sum of the primary air and the secondary air accounts for 1 of the total air. The outlet can be set as a pressure outlet, and all the walls at the outlet are set as no-slip walls, and a certain value of heat flux density is applied to the heating wall near the carbonization chamber , which is generally set to 7500W / m2. The top and bottom walls near the carbonization chamber can be set as heat sinks, and a heat flux density of less than , which is generally set to 5500W / m2, is applied. The remaining walls near the carbonization chamber are set as adiabatic.

[0021] The following control equation system is configured in the solver of software such as ANSYS Fluent for calculation and simulation: the Realizable k-ε turbulence equation is used in combination with the extendable wall function to simulate turbulent flow; the non-premixed combustion model is used to simulate the turbulent combustion process of coke oven gas and air, and the component concentration is determined by solving the mixture fraction transport equation; the discrete ordinate (DO) model is used to simulate the radiation heat transfer at high temperature; based on the Zeldovich mechanism, a thermal NO generation model is set for convenience of observation, and only thermal NO (accounting for more than 95%) is considered, i.e., the content of outlet NO is used as a basis for subsequent data screening. The solver uses a pressure-based steady-state solver, the pressure-velocity coupling uses the SIMPLE algorithm, and the momentum and energy equations use a second-order upwind format.

[0022] S3: The effects of the height, length and angle of the secondary air inlet on combustion and pollutant emission are studied by the control variable method, in order to reduce the outlet nitrogen oxide concentration (since NO is the main component, the NO concentration data is used for subsequent analysis) and improve the longitudinal temperature uniformity of the flue (measured by the temperature distribution standard deviation) as the optimization target. The effects of the three wind port design parameters of the secondary air inlet are systematically studied by the control variable method, as follows: 1. The process of analyzing the secondary air inlet height h is as follows: fix the two structure parameters L and a, and set several different h values, such as h=1.53m, 2.04m, 2.55m, 3.06m, 3.57m and 4.08m, Figure 3 ​(a) temperature distribution in YOZ cross-section, (b) O2 mole fraction distribution, and (c) NO mole fraction distribution in XOZ cross-section, from Figure 3 , Figure 4 and Figure 5 It can be found that with the increase of h, the combustion zone is obviously separated into primary combustion zone and secondary combustion zone. The primary combustion zone burns under lean oxygen condition, resulting in the decrease of oxygen concentration in this region, which inhibits the reaction of N2 and O2 to generate NO. At the same time, the highest temperature in the flue decreases from 2340 K (h = 1.53 m) to 2140 K (h = 4.08 m), and the outlet nitrogen oxide concentration (taking NO concentration as an example) decreases significantly from 1304 ppm to 281 ppm. The temperature standard deviation systematically decreases with the increase of h, indicating that the temperature uniformity is improved. However, the increase of h also causes the temperature fluctuation at the bottom of the flue, and the bottom temperature reaches the highest value of 1682 K at h = 3.06 m, which can meet the demand. The continuous increase of h, such as to 3.57 m and 4.08 m, leads to the gradual decrease of the bottom temperature, and too low bottom temperature may affect the coking of the corresponding carbonization chamber, so a relatively optimal value of h, i.e. 3.06 m, can be determined.

[0023] 2. The process of analyzing the secondary air inlet length L is as follows: fixing h = 3.06 m and a, setting several different L values, such as taking L = 140 mm, 160 mm, 180 mm, 200 mm, 220 mm and 240 mm as examples, Figure 6 (a) temperature distribution in YOZ cross-section, (b) turbulent kinetic energy distribution, and (c) NO mole fraction distribution in XOZ cross-section, from Figure 6 , Figure 7 and Figure 8 It can be found that the increase of L leads to the increase of the cross-sectional area of the secondary air inflow, and the inlet velocity decreases from 6.7 m / s to 3.9 m / s, thereby reducing the average flow velocity of the flue gas in the flue (from 1.02 m / s to 0.95 m / s). The decrease of flow velocity weakens the turbulent mixing intensity, leading to the weakening of the combustion intensity in the secondary combustion zone, the contraction of the high-temperature zone, and the decrease of the average temperature from 1731 K (L = 140 mm) to 1708 K (L = 240 mm). This collectively leads to the decrease of NO generation, and the outlet NO concentration decreases approximately linearly from 434 ppm to 374 ppm. The temperature standard deviation reaches the minimum value at L = 180 mm, indicating that the temperature distribution is the most uniform at this time. When L exceeds 180 mm, the temperature uniformity deteriorates, so L = 180 mm can be determined as a relatively optimal value.

[0024] 3. The process of analyzing the secondary air angle α (i.e., the angle between the secondary air inlet and the flue wall) is as follows: With h = 3.06m and L = 180mm fixed, several different α values ​​are set, for example, α = 60°, 55°, 50°, 45°, 40°, and 35°. Figure 9 (a) shows the temperature distribution at the YOZ cross section within the flue, (b) shows the H2 mole fraction distribution at the XOZ cross section, and (c) shows the NO mole fraction distribution. Figure 9 and Figure 10 It can be observed that as α decreases, the flame in the secondary combustion zone gradually deviates towards the right wall, posing a risk of corrosion. However, a smaller α results in a more uniform distribution of combustible components (such as H2) within the rising flue, delaying the combustion reaction and preventing the formation of localized high-temperature zones. This suppresses the formation of thermal NO, and both the maximum flue temperature and the outlet NO concentration decrease as α decreases, with the outlet NO concentration dropping from 400 ppm (α=60°) to 283 ppm (α=30°). Therefore, it is necessary to select a suitable angle that meets specific requirements, taking into account both NO emission reduction and preventing flame adhesion to the wall.

[0025] S4: Analyze the influence of each parameter and determine the optimal value of each of the three vent design parameters: Based on the sensitivity analysis results of S3, optimize the selection of each parameter. Height h has the most significant effect on NO emission reduction. When h=3.06m, it can achieve significant NO emission reduction (compared to the lowest point), maintain good temperature uniformity, and keep the bottom temperature at a relatively high level, avoiding the risk of insufficient heat at the bottom. Therefore, the optimal height h is determined. opt =3.06m. The length L primarily affects flow velocity and mixing, which in turn affects combustion intensity and temperature uniformity. When L = 180mm, the temperature distribution is most uniform, while NO emissions are also at a low level. Therefore, determining the optimal length L... opt =180mm. The angle α affects the mixing path and flame morphology. When α=45°, a good balance can be achieved between effectively reducing NO emissions (compared to a larger angle) and avoiding severe flame adhesion to the wall (compared to a smaller angle). Therefore, the optimal angle α can be determined. opt =45°.

[0026] S5: Verify the optimal parameters among the three air outlet design parameters to confirm the optimization effect: Based on the optimization results of step S4, determine the optimal combination of secondary air structure parameters as: h opt =3.06m, L opt =180mm, α opt= 45°. Based on this optimal combination, the final CFD simulation verification was carried out. The results show that: the outlet concentration is reduced to 342 ppm; compared with the baseline condition without adopting the staged air supply, the NO emission reduction reaches up to 80.3%; compared with other working conditions in the single-factor optimization process, this combination achieves the best comprehensive effect in terms of NO emission reduction and temperature uniformity; the maximum temperature in the flue is 2156 K, which is reduced by 46 K compared with the baseline condition; the longitudinal temperature distribution uniformity in the flue is also improved; after all the indicators meet the requirements, this parameter can be set as the optimal structural parameter of the secondary air inlet of the staged air supply system of the coke oven combustion chamber.

[0027] In summary, the optimal structural parameter of the secondary air inlet of the staged air supply system of the coke oven combustion chamber is successfully obtained through systematic parameterization research, accurate CFD simulation and multi-objective optimization. By applying the optimal parameter combination, the NOx emission can be greatly reduced and the temperature distribution can be optimized under the premise of ensuring the normal operation of the coke oven and the coking quality, which provides an effective technical means for the green and efficient operation of the coke oven.

[0028] Those skilled in the art can understand that all or part of the steps of the above-mentioned embodiment methods can be completed by programs instructing related hardware, therefore, the present application can adopt a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer usable program codes.

[0029] Each embodiment in the specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between each embodiment can be referred to each other. For the above embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the part of the method embodiment.

[0030] The above embodiments are described in detail, and the principles and implementation manners of the present application are described by applying specific examples. The above embodiment is only used to help understand the method and core idea of the present application; at the same time, for those skilled in the art, according to the idea of the present application, the specific implementation manner and application range can be changed; in summary, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A CFD-based method for optimizing the staged air supply structure of a combustion chamber, comprising a flue serving as the combustion chamber, and a primary air inlet, a secondary air inlet, a coke oven gas inlet, and an outlet disposed within the flue, characterized in that, The optimization method includes the following steps: A three-dimensional model of the coke oven combustion chamber is established based on the vertical fire channel of the target coke oven. The secondary air inlet includes three adjustable air outlet design parameters: the height of the secondary air inlet from the bottom of the fire channel, the length of the inlet channel, and the angle between the inlet and the fire channel wall. A CFD model was constructed based on a 3D model of the coke oven combustion chamber, and the mesh was generated, boundary conditions were set, and control equations were configured. With the optimization objectives of reducing the concentration of nitrogen oxides at the outlet in the three-dimensional model of the coke oven combustion chamber and improving the longitudinal temperature uniformity of the flue, the optimal values ​​of three tuyer design parameters—secondary air inlet height, inlet channel length, and the angle between the inlet and the flue wall—were obtained by controlling the variable method. The optimal values ​​of the three air outlet design parameters were verified by CFD simulation, and the optimal values ​​of the three air outlet design parameters were determined based on the verification results.

2. The method for optimizing the staged air supply structure of the combustion chamber according to claim 1, characterized in that, The specific steps for dividing the grid are as follows: The computational domain of the three-dimensional model of the coke oven combustion chamber is discretized using a structured mesh dominated by hexahedrons; Several key flow regions in the three-dimensional model of the coke oven combustion chamber were identified, and local mesh refinement was performed to obtain several mesh models with different numbers of meshes. The outlet temperature, average heated wall temperature, and outlet nitrogen oxide concentration were compared under several different grid numbers, and the grid model with the relative error of each parameter being lower than the error threshold was selected for subsequent simulation.

3. The method for optimizing the staged air supply structure of the combustion chamber according to claim 1, characterized in that, The boundary conditions include: Set the preheating temperature of coke oven gas and the preheating temperature of combustion air. Set the fuel inlet and primary air inlet as mass flow inlets, and set the fuel mass flow rate and the mass ratio of primary air to total air volume, respectively; Set the secondary air inlet as the mass flow inlet, and set the mass ratio of secondary air to total air volume, and the sum of the mass ratio of primary air to total air volume and the mass ratio of secondary air to total air volume is 1. The outlet can be set as a pressure outlet, and all walls at the outlet can be set as non-slip walls. Apply a certain heat flux density to the heating wall surface near the carbonization chamber. The top and bottom walls near the carbonization chamber are designated as heat dissipation surfaces, while applying a value less than [value missing]. heat flux density The remaining walls near the carbonization chamber will be insulated.

4. The method for optimizing the staged air supply structure of the combustion chamber according to claim 1, characterized in that, The governing equations include: Turbulent flow is simulated using turbulence equations combined with extended wall functions; A non-premixed combustion model was used to simulate the turbulent combustion process of coke oven gas and air, and the component concentrations were determined by solving the mixing fraction transport equation. A discrete coordinate model is used to simulate radiative heat transfer at high temperatures; Based on the Zeldovich mechanism, a generation model for thermal NO was established; A pressure-based steady-state solver is used, the pressure-velocity coupling is performed using the SIMPLE algorithm, and the momentum and energy equations are discretized using a second-order upwind scheme.

5. The method for optimizing the staged air supply structure of the combustion chamber according to claim 4, characterized in that, The turbulence equation is a Realizable k-ε turbulence equation.

6. The method for optimizing the staged air supply structure of the combustion chamber according to claim 1, characterized in that, The specific steps for obtaining the optimal values ​​of the three air outlet design parameters—secondary air inlet height, inlet channel length, and the angle between the inlet and the fire channel wall—using the controlled variable method are as follows: Two air outlet design parameters were fixed: the length L of the secondary air inlet channel and the angle α between the inlet and the fire channel wall. CFD simulations were performed with several different values ​​for the secondary air inlet height h. Two air outlet design parameters, namely the secondary air inlet height h and the angle α between the inlet and the fire channel wall, were fixed, and CFD simulations were performed with several different values ​​for the length L of the secondary air inlet channel. Two air outlet design parameters, namely the secondary air inlet height h and the secondary air inlet channel length L, were fixed, and CFD simulations were performed with several different values ​​of the angle α between the inlet and the fire channel wall. Based on the simulation results, the optimal values ​​of three air outlet design parameters were obtained: the highest temperature inside the flue, the nitrogen oxide concentration at the outlet, the temperature standard deviation, and the temperature at the bottom of the flue. The optimal values ​​of these parameters were obtained: the height of the secondary air inlet, the length of the inlet channel, and the angle between the inlet and the flue wall.

7. A system for implementing the CFD-based combustion chamber staged air supply structure optimization method according to any one of claims 1-6, characterized in that, It includes a processor and a memory, the memory being used to store a computer program, which, when executed by the processor, implements the CFD-based combustion chamber staged air supply structure optimization method as described in any one of claims 1-6.

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