A method of characterizing the contribution of gas jet flow and flame chemistry in gaseous fuel jet turbulent combustion

Abstract

The method for characterizing the component effect of gas jet flow and flame chemical reaction in gas fuel jet turbulent combustion belongs to the field of internal combustion engines. In the process of gas fuel jet turbulent combustion, the gas fuel jet interacts with the flame. Vorticity is used to characterize the gas jet flow characteristics, and OH mass fraction is used to characterize the flame chemical reaction characteristics. In order to compare the respective effects of gas jet turbulent flow and flame chemical reaction in jet turbulent combustion, the dimensionless coefficients K v and K OH (wherein v represents vorticity, and OH represents OH mass fraction) are introduced based on vorticity and OH mass fraction, and K is defined as the ratio of the characteristic parameters (vorticity, OH mass fraction) in the jet turbulent combustion at the same time to the characteristic parameters of a single reference state (free jet, premixed combustion). The jet flow and flame combustion are decoupled, and the respective component effects in the jet turbulent combustion are further characterized.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine technology, and more specifically, to a method for characterizing the component effects of gas jet flow and flame chemical reaction in turbulent combustion of gaseous fuel jets. Background Technology

[0002] Currently, the use of low-carbon and zero-carbon gaseous fuels (natural gas, hydrogen, ammonia) is a key means to resolve the contradiction between energy conservation and emissions in various power plants. Gaseous fuels such as methane and ammonia are difficult to ignite and have low combustion rates, requiring ignition by other fuels to improve combustion. As the gaseous fuel jet propagates forward, it comes into contact with an already burning flame and is ignited; under the action of the high-pressure jet, the premixed flame develops into a turbulent combustion flame. The process of high-speed gaseous fuel jet ultimately forming turbulent combustion involves two complex issues: turbulent flow and combustion (chemical reaction). The gaseous jet turbulence, flame, and ambient mixture interact and transfer energy, with kinetic, chemical, and thermal energy cascading through the process. The interaction between the high-speed clean fuel jet and the premixed flame determines the combustion process, which in turn affects the stability and efficiency of in-cylinder combustion. Therefore, studying gaseous jet turbulent combustion has significant practical implications.

[0003] Current research on gaseous fuel jet combustion typically separates the high-speed jet from the premixed flame, analyzing their individual effects on jet combustion. This involves analyzing the penetration distance and velocity of the free jet, and the flame radius and thickness of the premixed flame to observe their influence on jet combustion. These calculations are complex, extensive, time-consuming, and labor-intensive. The free jet, representing the high-pressure impact motion of gas, is a flow field, and its influence on jet combustion is primarily studied by analyzing vorticity. The premixed flame, representing a pure chemical reaction, is a chemical field, and its influence on jet combustion is primarily studied by analyzing the OH mass fraction. However, vorticity and OH mass fraction have different units and physical properties, therefore, directly comparing their magnitudes cannot characterize the relative strength of the jet's and combustion's effects on jet combustion.

[0004] Jet combustion is not a simple coupling of the physical momentum of a free jet and premixed combustion. Therefore, how to decouple the free jet from premixed combustion to characterize the strength of its effect on jet combustion is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the problems existing in the background technology, a method is proposed to characterize the component effects of gas jet flow and flame chemical reaction in turbulent combustion of gaseous fuel jets.

[0006] A method for characterizing the component effects of gas jet flow and flame chemical reaction in turbulent combustion of gaseous fuel jets, characterized by comprising the following steps:

[0007] The jet turbulence combustion generator includes a nozzle 1, a combustion chamber 2, and an ignition needle 3. Both the nozzle and ignition needle are located on the axis of the combustion chamber, with the bottom of the nozzle inside the chamber and the ignition needle at the center. The direction of the high-speed gas jet is defined as the z-axis, with the origin and zero point set at the nozzle outlet. The ignition time is set to zero. Three-dimensional models of three different flow field modes—free gas jet, premixed flame, and jet combustion—are established by controlling the states of the nozzle and ignition needle.

[0008] Vorticity is used to characterize the free jet flow characteristics, and OH mass fraction is used to characterize the premixed flame chemical reaction characteristics. The combustion chamber is divided into n equal parts (n approaches infinity) perpendicular to the nozzle direction, forming n planes. The vorticity and OH mass fraction on the n planes are calculated and summed. The vorticity of the free jet field and the OH mass fraction of the premixed flame field within the combustion chamber space are calculated.

[0009] The vorticity of the i-th plane in the combustion chamber of the free jet field and the OH mass fraction in the combustion chamber of the premixed flame field are respectively: In the formula, x represents the parameter under a single reference state (free jet, premixed combustion); A i Represents the area of ​​plane i; Let be the point-average vorticity of the i-th plane of the free jet; The average OH mass fraction at points on the i-th plane of the premixed flame; Let be the vorticity of the i-th plane of the free jet; denoted as OH mass fraction in the i-th plane of the premixed flame. The total vorticity of the free jet field and the total OH mass fraction of the premixed flame field, i.e., the sum of the vorticity and OH mass fraction on n planes, are: In the formula, l is the length of the combustion chamber; The fitted curve of surface vorticity of the free jet field versus combustion chamber height; The fitted curve of surface OH mass fraction in the premixed flame field versus combustion chamber height; V x The total vorticity of the free jet field; OH x This represents the total OH mass fraction in the premixed flame field.

[0010] A gaseous fuel jet impacts and interacts with the flame to form jet turbulent combustion. The vorticity of jet turbulent combustion is used to characterize its flow characteristics, and the OH mass fraction is used to characterize its flame chemical reaction characteristics. Based on the vorticity feature extraction method for the free jet field and the OH mass fraction feature extraction method for the premixed flame, the vorticity V and OH mass fraction OH of jet turbulent combustion can be obtained. In the formula, L(V i ( ) is the fitted curve of surface vorticity of the jet combustion field versus combustion chamber height; L(OH i ( ) is the fitted curve of the surface OH mass fraction of the jet combustion field versus the combustion chamber height; V represents the total vorticity of the jet combustion field; OH represents the total OH mass fraction in the jet combustion field.

[0011] Define the dimensionless constant K v and K OH This decouples the jet flow from the flame combustion, characterizing their respective roles in jet turbulent combustion. In the formula, K v is the dimensionless constant of vorticity; K OH is a dimensionless constant representing the mass fraction of OH.

[0012] Compare K v With K OH The size of K. v >K OH This indicates that the impact of the high-pressure gaseous fuel free jet significantly increases the vorticity. Compared to premixed combustion, the free jet plays a more important role in jet combustion. If K v =K OH This indicates that free jets and premixed flames have the same effect on jet combustion. If K v <K OH This indicates that the premixed flame causes a significant increase in the OH mass fraction. Compared to free jet combustion, premixed combustion plays a more important role in jet combustion.

[0013] The principle and features of this invention:

[0014] Jet impingement on a premixed flame forms jet combustion. Vorticity and OH mass fraction are two important parameters for evaluating jet combustion. The change in vorticity in jet combustion is mainly caused by the gas jet, while the change in OH mass fraction in the jet flame is mainly caused by the combustion of the premixed flame. Since vorticity and OH mass fraction have different units and physical properties, it is impossible to compare the effects of the jet and combustion on jet combustion simply by comparing the magnitudes of changes in vorticity and OH mass fraction. Therefore, a dimensionless constant K is introduced. v and K OH , defined as the ratio of characteristic parameters (vorticity, OH mass fraction) in jet turbulent combustion to the characteristic parameters in a single reference state (free jet, premixed combustion) at the same time. This decouples the jet flow from the flame combustion, further characterizing their respective roles in jet turbulent combustion.

[0015] The beneficial effects achieved by this invention are:

[0016] By introducing a dimensionless constant K v and K OH Decoupling the free jet field from the premixed combustion field in the jet combustion coupling field, based on K v Characterizing the effect of the free jet field on jet combustion, based on K OH This method characterizes the effect of the premixed combustion field on jet combustion; it is simple to calculate and easy to implement. Attached Figure Description

[0017] Figure 1 This is a structural diagram of the device according to an embodiment of the present invention. In the diagram, 1-nozzle, 2-combustion chamber, 3-ignition needle.

[0018] Figure 2(a) Free jet combustion mode diagram; Figure 2(b) Premixed combustion mode diagram; Figure 2(c) Jet combustion mode diagram;

[0019] Figure 3 The following is a logic diagram illustrating the application of the method in an embodiment of the present invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings. It is to be understood that the embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings, not all of them.

[0021] according to Figure 1As shown in the diagram, this embodiment of the invention provides a device structure diagram. It includes a nozzle 1, a combustion chamber 2, and an ignition needle 3. Both the nozzle and the ignition needle are located on their respective axes, with the bottom of the nozzle located inside the combustion chamber and the ignition needle located at the center of the combustion chamber. The direction of the high-speed gas jet is defined as the z-axis, and the origin and zero point are set as the nozzle outlet. The ignition time is set to zero. Three-dimensional models of three different flow field modes—free gas jet, premixed flame, and jet combustion—are established by controlling the states of the nozzle and ignition needle.

[0022] according to Figure 3 The following is a logic diagram illustrating the application of the method of the present invention:

[0023] Three-dimensional models of three different flow field modes—free gas jet, premixed flame, and jet combustion—are established by controlling the states of the nozzle and ignition needle.

[0024] Calculate the vorticity and OH mass fraction for each flow field model within the combustion chamber space. Divide the combustion chamber into n equal parts perpendicular to the nozzle direction (the larger the n, the more accurate the value), forming n planes. Calculate and sum the vorticity and OH mass fraction on the n planes.

[0025] The vorticity is used to characterize the free jet flow characteristics, and the OH mass fraction is used to characterize the premixed flame chemical reaction characteristics. The vorticity V of the free jet field is obtained. x OH mass fraction in the premixed flame field x .

[0026] A gaseous fuel jet impacts and interacts with a flame, forming jet turbulent combustion. The flow characteristics of jet turbulent combustion are characterized by vorticity, and the chemical reaction characteristics of the jet turbulent combustion flame are characterized by the OH mass fraction. The vorticity V and OH mass fraction OH of jet turbulent combustion are calculated.

[0027] Define the dimensionless constant K v and K OH This decouples the jet flow from the flame combustion, characterizing their respective roles in jet turbulent combustion.

[0028] If K v >K OH This indicates that the impact of the high-pressure gaseous fuel free jet significantly increases the vorticity. Compared to premixed combustion, the free jet plays a more important role in jet combustion. If K v =K OHThis indicates that free jets and premixed flames have the same effect on jet combustion. If K v <K OH This indicates that the premixed flame causes a significant increase in the OH mass fraction. Compared to free jet combustion, premixed combustion plays a more important role in jet combustion.

Claims

1. A method for characterizing the component effects of gas jet flow and flame chemical reaction in turbulent combustion of gaseous fuel jets, characterized in that: S1: The jet turbulence combustion generator includes a nozzle, a combustion chamber, and an ignition needle; both the nozzle and the ignition needle are located on the axis of the combustion chamber, with the bottom of the nozzle located inside the combustion chamber and the ignition needle located at the center of the combustion chamber; the direction of the high-speed gas jet is defined as the z-axis, and the origin and zero point are set as the nozzle outlet; the ignition time is set as the time zero point; three-dimensional models of three different flow field modes—free gas jet, premixed flame, and jet combustion—are established by controlling the states of the nozzle and the ignition needle. S2: Vorticity is used to characterize the free jet flow characteristics, and OH mass fraction is used to characterize the chemical reaction characteristics of the premixed flame; Divide the combustion chamber into n equal parts perpendicular to the nozzle direction to form n planes. Calculate and sum the vorticity and OH mass fraction on the n planes. Calculate the vorticity of the free jet field and the OH mass fraction of the premixed flame field in the combustion chamber space. S3: According to S2, the vorticity of the i-th plane in the combustion chamber of the free jet field and the OH mass fraction in the combustion chamber of the premixed flame field are respectively: In the formula, x represents the parameter under a single reference state, i.e., free jet or premixed combustion; A i Represents the area of ​​plane i; Let be the point-average vorticity of the i-th plane of the free jet; The average OH mass fraction at points on the i-th plane of the premixed flame; Let be the vorticity of the i-th plane of the free jet; is the OH mass fraction of the i-th plane of the premixed flame; The total vorticity of the free jet field and the total OH mass fraction of the premixed flame field, i.e., the sum of the vorticity and OH mass fraction on n planes, are: In the formula, l is the length of the combustion chamber; The fitted curve of surface vorticity of the free jet field versus combustion chamber height; The fitted curve of surface OH mass fraction in the premixed flame field versus combustion chamber height; V x The total vorticity of the free jet field; OH x The total OH mass fraction in the premixed flame field; S4: The gaseous fuel jet impacts the flame and interacts with it to form jet turbulent combustion; the vorticity is used to characterize the flow characteristics of jet turbulent combustion, and the OH mass fraction is used to characterize the chemical reaction characteristics of the jet turbulent combustion flame; the vorticity V and OH mass fraction OH of jet turbulent combustion are obtained based on S2 and S3. In the formula, L(V i ( ) is the fitted curve of surface vorticity of the jet combustion field versus combustion chamber height; L(OH i ( ) is the fitted curve of the surface OH mass fraction of the jet combustion field versus the combustion chamber height; V represents the total vorticity of the jet combustion field; OH represents the total OH mass fraction in the jet combustion field; S5: Define the dimensionless constant K v and K OH This decouples jet flow from flame combustion, characterizing their respective roles in jet turbulent combustion. In the formula, K v is the dimensionless constant of vorticity; K OH is a dimensionless constant representing the mass fraction of OH; S6: K calculated from S5 v With K OH Compare K v With K OH The size of K; if K v >K OH This indicates that the impact of the high-pressure gaseous fuel free jet significantly increases the vortex; compared to premixed combustion, the free jet plays a more important role in jet combustion; if K v =K OH This indicates that free jets and premixed flames have the same effect on jet combustion; if K v <K OH This indicates that the premixed flame causes a significant increase in the OH mass fraction; compared to free jet, premixed combustion plays a more important role in jet combustion.

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