Statistical evaluation method for combustion air ratio in different positions of flame tube
By using computational fluid dynamics to track the mixture fraction and oxygen mass fraction of the combustor intake, the empirical problem of combustion air ratio assessment is solved, and the scientific and optimized design of the combustion chamber is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-01-18
- Publication Date
- 2026-04-07
AI Technical Summary
The existing statistical analysis methods for the combustion air ratio are too empirical, which limits the development of combustion chamber design methodology, especially in the forward design of new combustion chambers where there is a lack of objective evaluation methods.
Computational fluid dynamics numerical simulation technology was used to track the mixing fraction and oxygen mass fraction of the air entering at different positions in the flame tube based on the transport equation of the Euler field. The solution was combined with conventional combustion chamber simulation software, and the integral was performed at the combustion chamber outlet to obtain the mass percentage of air participating in combustion.
It enables objective assessment of the combustion air ratio, supports traceability analysis and airflow distribution optimization in the combustion chamber design process, and improves the scientific nature and accuracy of the design.
Smart Images
Figure CN115081347B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aviation gas turbine combustor design technology, and more specifically, to a statistical evaluation method for the proportion of combustion air in the intake at different positions of the flame tube. Background Technology
[0002] Due to limitations in materials and cooling technology, the overall air-fuel ratio in the combustion chamber of an aero-gas turbine is far lower than the stoichiometric ratio, and the fuel-air mixture can only undergo combustion chemical reactions within a very narrow air-fuel ratio range (equivalent ratio α ≈ 0.5–2.5). To achieve stable operation of the engine and combustion chamber over a wide operating range, the flame tube design generally employs methods such as... Figure 1 The diagram illustrates a zoned airflow organization method. Its basic principle is that air entering the combustion chamber flows into the flame tube through air inlets at different locations, thus forming different functional zones within the flame tube, including the main combustion zone, the intermediate zone (also known as the afterburning zone), and the mixing zone. The air flowing into the flame tube is mainly divided into head intake, main combustion port intake, intermediate port intake, mixing port intake, and cooling air (divided into front-stage cooling air, middle-stage cooling air, and rear-stage cooling air). The relative proportions of air flow from different intake ports constitute the combustion chamber airflow distribution design, a crucial aspect of the combustion chamber design process.
[0003] The main purposes of airflow distribution are twofold: first, to ensure that an appropriate amount of air flows into the combustion zone (main combustion zone and afterburner zone) to ensure stable and efficient combustion under different operating conditions; and second, to achieve efficient mixing of cold and hot airflows in the mixing zone to ensure uniformity of the combustion chamber outlet temperature. To achieve the first purpose, the concept of "combustion air" needs to be introduced into airflow distribution, which is the relative flow rate of air participating in the combustion reaction in the flame tube. It is generally believed that combustion air includes head intake air flowing in from the swirler (2), main combustion port intake air flowing in from the main combustion port (3), and cooling air flowing in from the cooling port (front and middle section cooling air). The proportion of air flowing in from different positions participating in combustion is also different. Taking the intake air from the main combustion port (3) as an example, it is generally believed that only 40% to 50% of the air flowing through the main combustion port (3) recirculates back into the combustion zone to participate in combustion. However, this proportion is only an empirical value, and obviously, the actual recirculation proportion is also different for different combustion chambers due to the influence of the momentum ratio of the intake air from the main combustion port.
[0004] Current statistical analysis methods for combustion air are too empirical, limiting the development of combustion chamber design methodologies. In particular, for the forward design of novel combustion chambers, an objective statistical analysis method for combustion air is urgently needed. Therefore, this invention aims to design and provide a statistical evaluation method for the proportion of combustion air in the intake air at different positions of the flame tube, in order to solve the aforementioned problems. Summary of the Invention
[0005] The purpose of this invention is to provide a statistical evaluation method for the proportion of combustion air in the air intake at different positions of the flame tube, based on solving the above-mentioned problems. The method of this invention is based on computational fluid dynamics numerical simulation technology, which marks the air flowing into the flame tube at different positions, and establishes transport equations based on Eulerian fields for the mixture fraction and oxygen mass fraction. The established transport equations are solved synchronously with conventional combustion simulation software for the combustion chamber. In post-processing, the percentage of air mass participating in combustion in the air stream can be obtained by integrating the oxygen mass in the air flowing into the marked response positions at the combustion chamber outlet.
[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a statistical evaluation method for the proportion of combustion air in different intake positions of a flame tube, comprising the following steps:
[0007] S1. The calculation domain inside and outside the flame tube is discretized by using a multi-inlet separate air intake method. The entire calculation domain has one outlet and multiple air inlets.
[0008] S2. Based on the computational domain described in step S1, establish the corresponding transport equation to track the mixing fraction of the air flowing into a specific inlet i of the flame tube and the mass fraction of oxygen it carries, i.e.:
[0009]
[0010]
[0011] Where ρ is the density of the local gas in the flow field, U is the velocity vector, D is the component diffusion coefficient, t is the physical time corresponding to the flow field simulation, and z air,i Y represents the mass fraction of the local gas inflow of the specific inlet that needs to be tracked. O2,i and These represent the mass fraction of oxygen carried by the air flowing into the specific inlet being tracked, within the local gas composition, and its chemical reaction rate.
[0012] in, Defined as:
[0013]
[0014] Among them, Y O2 and Y represents the total oxygen mass fraction and its chemical reaction rate in the local mixed gas, respectively. O2 and Provided by the combustion model in the numerical simulation of the combustion chamber;
[0015] S3. Based on the discretization and numerical solution of the two transport equations (1) and (2) in step S2, the mixing fraction z of the air flowing into the specific inlet i of the flame tube of interest in the flow field is obtained. air,i and the mass fraction of oxygen it carries, Y O2,i Spatial distribution;
[0016] Then for z air,i and Y O2,i The two physical quantities are integrated at the combustion chamber outlet to obtain the percentage of combustion air flowing into the air at a specific inlet of the flame tube of interest:
[0017]
[0018] in, The integral of the dot product of the area vector of the infinitesimal element on section A; This represents the mass fraction of oxygen in pure air.
[0019] Furthermore, the outlet mentioned in step S1 is the flame tube outlet; the multiple air inlets include the head air inlet, the main combustion hole air inlet, the mixing hole air inlet, and the cooling hole air inlet.
[0020] Furthermore, the transport equation (2) in step S2 consists of a time partial derivative term, a spatial convection term, a diffusion term, and a source term.
[0021] Furthermore, the source term in the transport equation for the oxygen mass fraction carried by the specific inlet air is determined based on the total oxygen mass fraction in the local computational domain, its reaction source term, and the oxygen mass fraction carried by the specific inlet air.
[0022] In summary, the present invention has the following beneficial effects:
[0023] The method of this invention is based on the Euler transport equation in computational fluid dynamics, establishing a corresponding transport equation to track the mixing fraction and oxygen mass fraction of the air entering at the location of interest. Simultaneously, to mark the air flowing into the combustion chamber from different intake positions, the calculation employs a separate intake method to simplify and discretize the airflow path within the combustion chamber. By integrating the marked air mixing fraction and its oxygen mass fraction at the combustion chamber outlet, the proportion of combustion-participating air in the marked air can be obtained. This overcomes the problem that current statistical analysis methods for combustion air are too empirical, limiting the development of combustion chamber design methodologies. Furthermore, this method can be used for combustion air source tracing analysis and optimized airflow distribution design in the design process of aero-gas turbine combustion chambers. Attached Figure Description
[0024] Figure 1 This is a schematic diagram of the combustion chamber structure;
[0025] Figure 2 This is a schematic diagram of the computational domain for numerical simulation based on separate air intake.
[0026] In the diagram: 1. Diffuser; 2. Swirl; 3. Main combustion port; 4. Mixing port; 5. Front cooling port; 6. Mid-stage cooling port; 7. Rear cooling port; 8. Head air inlet; 9. Front cooling gas inlet; 10. Main combustion port air inlet; 11. Mid-stage cooling gas inlet; 12. Mixing gas inlet; 13. Rear cooling gas inlet; 14. Combustion chamber outlet. Detailed Implementation
[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] Example: A statistical evaluation method for the proportion of combustion air in the air intake at different positions of the flame tube, based on Figure 1 The combustion chamber shown is illustrated using air flowing into the main combustion port (3) as an example. The main combustion port inlet (10) is labeled as inlet 1, and the corresponding air-mixing fraction and oxygen mass fraction are labeled as z. air,1 and Y O2,1 This includes the following steps:
[0029] Step 1: To Figure 1 The conventional combustion chamber structure shown is simplified to obtain, as shown below. Figure 2 The calculation area for the multi-inlet flame tube is shown below;
[0030] Step 2: Adding specific techniques to the preprocessing of the combustion chamber flow combustion simulation.
[0031]
[0032] The initial and boundary conditions; where z air,1 and Y O2,1 All initial values are set to 0; in the boundary condition settings, the value at the main combustion orifice inlet is set to z. air,1 =1 and Set other entry points to z air,1 =0 and Y O2,1 =0;
[0033] Step 3: Perform numerical simulation calculations on the flow field structure inside the combustion chamber to obtain the steady-state flow field structure of the combustion chamber; based on the simulation results, perform statistical analysis of the equation definition at the combustion chamber outlet (14) to obtain the percentage of air flowing into the main combustion hole that participates in the combustion chemical reaction inside the flame tube.
[0034] This specific embodiment is merely an explanation of the present invention and is not intended to limit it. Those skilled in the art, after reading this specification, can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of the present invention. For example, replacing the main combustion port inlet in the above steps with a head air inlet allows for the determination of the percentage of combustion air in the head air intake of the flame tube. Therefore, any technical modifications made to the technical solution based on the technical concept proposed in this invention fall within the protection scope of the claims of the present invention.
Claims
1. A statistical evaluation method for the proportion of combustion air in the air intake at different positions of the flame tube, characterized by: Includes the following steps: S1. The calculation domain inside and outside the flame tube is discretized by using a multi-inlet separate air intake method. The entire calculation domain has one outlet and multiple air inlets. S2. Based on the computational domain described in step S1, establish the corresponding transport equations to track specific inlets of the flame tube. The mixture fraction of the incoming air and the mass fraction of oxygen it carries, namely: in, It is the density of the local gas in the flow field. It is a velocity vector. It is the component diffusion coefficient. This is the physical time corresponding to the flow field simulation. Characterizes the proportion of local gas mixture in the air flowing into a specific inlet that needs to be tracked. and These represent the mass fraction of oxygen carried by the air flowing into the specific inlet being tracked, within the local gas composition, and its chemical reaction rate. in, Defined as: in, and These represent the total oxygen mass fraction and its chemical reaction rate in the local mixed gas, respectively. and Provided by the combustion model in the numerical simulation of the combustion chamber; S3. Based on the discretization and numerical solution of the two transport equations (1) and (2) in step S2, the specific inlet of the flame tube of interest in the flow field is obtained. The mixing fraction of the incoming air and the mass fraction of oxygen it carries Spatial distribution; Then to and The two physical quantities are integrated at the combustion chamber outlet to obtain the percentage of combustion air flowing into the air at a specific inlet of the flame tube of interest: in, cross section The integral of the dot product of the area vector of the infinitesimal element; This represents the mass fraction of oxygen in pure air.
2. The statistical evaluation method for the proportion of combustion air in different intake positions of a flame tube according to claim 1, characterized in that: The outlet mentioned in step S1 is the flame tube outlet; the multiple air inlets include the head air inlet, the main combustion hole air inlet, the mixing hole air inlet, and the cooling hole air inlet.
3. The statistical evaluation method for the proportion of combustion air in different intake positions of a flame tube according to claim 1, characterized in that: The transport equation (2) in step S2 consists of a time partial derivative term, a spatial convection term, a diffusion term, and a source term.
4. The statistical evaluation method for the proportion of combustion air in different intake positions of a flame tube according to claim 3, characterized in that: The source term in the transport equation for the oxygen mass fraction carried by the specific inlet air is determined based on the total oxygen mass fraction in the local computational domain, its reaction source term, and the oxygen mass fraction carried by the specific inlet air.