Supersonic combustion recirculation zone isl instability heat flux threshold calculation and ignition method

Abstract

The present application relates to the technical field of supersonic combustion ignition, and discloses a method for calculating the heat flux threshold of ISL instability in a supersonic combustion backflow area and for igniting, which comprises the following steps: constructing a two-dimensional model of the backflow area downstream of a flame holder, deriving the heat flux threshold of shear layer instability induced by energy deposition in the backflow area based on the instability criterion of compressible fluid shear layer and the energy conservation relationship, combining the model with non-reacting flow numerical simulation data to estimate the heat flux modulus length distribution of the heat flux threshold on the shear layer interface in specific working conditions, predicting the position of local flame breaking through the shear layer in the backflow area according to the relationship between the maximum heat flux modulus length and the heat flux threshold, and guiding the ignition based on the position of local flame breaking through the shear layer in the backflow area and the heat flux threshold. The present application can accurately calculate the heat flux threshold and predict the position of local flame breaking, thereby improving the success probability of ignition.

Description

Technical Field

[0001] This invention relates to the field of supersonic combustion ignition technology, and in particular to a method for calculating the instability heat flux threshold and ignition of the ISL in the supersonic combustion reflux zone. Background Technology

[0002] Supersonic combustion (SC) faces severe challenges in high Mach number (typically greater than 2.0) and extremely short fuel residence times (on the order of milliseconds) under high-Mach number inflow conditions. Existing technologies often employ concave or plate-mounted burner stabilizers to create a recirculation zone, extending the residence time of the fuel-air mixture and providing an ignition source (e.g., plasma torch igniters). However, after localized flame formation in the recirculation zone, the shear layers on both sides of the burner's trailing edge exhibit a significant stabilization trend due to the velocity difference between the high-speed main flow and the low-speed recirculation zone (especially at convective Mach numbers). When the disturbance is difficult to propagate upstream, the ignition shear layer (ISL) becomes unstable, making it difficult for the local flame to break through the shear layer and develop into a global flame, resulting in a low ignition success rate.

[0003] To improve ignition success rates, existing technologies primarily focus on optimizing fuel distribution and mixing through structural optimization. However, none of these methods provide a quantitative heat flux threshold calculation method for ISL instability, making it difficult to accurately assess whether energy deposition is sufficient to induce ISL instability and predict local flame breakthrough locations. While existing research focuses on shear layer dynamics (i.e., Kelvin-Helmholtz instability) and abstract models of continuous stirred-tank reactors (CSTRs) in the recirculation zone, it lacks a complete threshold calculation framework that combines reaction kinetics and non-reactive flow field data. This results in the need to rely on empirical trial-and-error combustion enhancement methods such as supplemental oxygen injection to improve the ignition success probability under low-power ignition conditions, leading to low actual ignition success rates. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for calculating the instability heat flux threshold and ignition in the supersonic combustion recirculation zone ISL, which can accurately calculate the heat flux threshold, predict the local flame breakthrough position, and improve the probability of successful ignition.

[0005] To address the aforementioned technical problems, this invention provides a method for calculating the ISL instability heat flux threshold in the supersonic combustion recirculation zone, comprising: A two-dimensional model of the downstream recirculation zone of the stabilizer is constructed. Based on the instability criterion of the compressible fluid shear layer and the energy conservation relationship, the heat flux threshold for energy deposition-induced shear layer instability in the recirculation zone is derived.

[0006] Furthermore, the construction of the two-dimensional model of the downstream recirculation zone of the burner includes: The downstream recirculation zone of the flame stabilizer is abstracted as a continuous stirred tank reactor, and a two-dimensional model corresponding to the continuous stirred tank reactor is established. The two-dimensional model is divided along the XOZ symmetry plane, and only one side of the shear layer and half of the recirculation zone are analyzed.

[0007] Furthermore, the derivation of the heat flux threshold for energy deposition-induced shear layer instability in the recirculation region based on the compressible fluid shear layer instability criterion and energy conservation relationship includes: In compressible supersonic flow, a convective Mach number is introduced to describe the propagation of disturbances, and the instability conditions of the shear layer are constructed based on the convective Mach number. Calculate the sound velocity and energy conservation formula after heating, substitute the sound velocity and energy conservation formula after heating into the instability condition to solve for the temperature rise, and obtain the heat flux threshold for shear layer instability based on the temperature rise.

[0008] Furthermore, the instability conditions of the shear layer are constructed based on the aforementioned convection Mach number, specifically as follows: when When judging the instability of the shear layer, Indicates the convection Mach number; The instability condition at this point is equivalently constructed as follows: , In the formula, The average flow velocity on the high-velocity side of the shear layer. The average flow velocity on the low-velocity side of the shear layer. for The corresponding average speed of sound, for The corresponding average speed of sound.

[0009] Furthermore, the speed of sound after heating is: , In the formula, The speed of sound after heating. For specific heat ratio, It is the gas ratio constant. The static temperature of the incoming flow on the low-velocity side of the shear layer. For temperature rise; The energy conservation formula per unit area is: , In the formula, Energy per unit area For the duration of thermal deposition, The average density of the recirculation zone, For the thickness of the reflux zone, This is the specific heat capacity at constant pressure.

[0010] Furthermore, substituting the aforementioned sound velocity and energy conservation formulas after heating into the instability condition to solve for the temperature rise, the heat flux threshold for shear layer instability is obtained based on the temperature rise, specifically: Substituting the aforementioned formulas for the velocity of sound after heating and the conservation of energy per unit area into the instability condition, the temperature rise is calculated as follows: ; Based on the temperature rise, the heat flux threshold is constructed as follows: , In the formula, The heat flux threshold, The static temperature of the incoming flow on the high-speed side of the shear layer.

[0011] This invention also provides a method for igniting the ISL instability heat flux threshold in the supersonic combustion recirculation region, comprising: The heat flux threshold for shear layer instability was obtained using the supersonic combustion reflow zone ISL instability heat flux threshold calculation method. Combined with two-dimensional model and non-reactive flow numerical simulation data, the heat flux modulus distribution of the heat flux threshold at the reflow zone shear layer interface under specific working conditions was estimated. Based on the relationship between the maximum value of the heat flux modulus in the heat flux modulus distribution and the heat flux threshold, the location where the local flame in the reflow zone breaks through the shear layer is predicted, and ignition is guided by combining the location where the local flame in the reflow zone breaks through the shear layer and the heat flux threshold.

[0012] Furthermore, the estimation of the heat flux modulus distribution at the shear layer interface in the recirculation zone, based on the two-dimensional model and non-reactive flow numerical simulation data, specifically involves: The shear layer interface is discretized into triangular patches. Based on the triangular patches, the flow field parameters are extracted by non-reactive flow numerical simulation. The PSR model in CHEMKIN is used to input the re-entry characteristics of the re-flow region and output the volumetric heat generation rate of the re-flow region. Based on the density gradient of the volumetric heat generation rate in the recirculation region, the power density is mass-weighted and corrected. A three-dimensional matrix field is constructed by projecting along the YOZ and XOZ planes, and the interface heat flux modulus distribution field is obtained by projection calculation.

[0013] Furthermore, the reentry characteristics of the recirculation region include the average residence time, which is calculated using Lagrange particle tracking. Generate local flow field data points, denoted as: , In the formula, For the i-th data point, Let i be the spatial coordinates of the i-th data point. Let i be the velocity vector of the i-th data point. Let be the density of the i-th data point. Let represent the oxygen mass fraction at the i-th data point. For the fuel mass fraction of the i-th data point, Let i be the temperature of the i-th data point. Let M be the pressure at the i-th data point, and M be the total number of data points. In the upstream of the reflow zone, a random seed method is used to track data points and determine whether the data points are entrained by the shear layer and enter the reflow zone. Count the data points entering and leaving the return flow area, and calculate the dwell time of the i-th data point within the tracking steps: , In the formula, Let i be the dwell time of the i-th data point. Let i be the number of numerical tracking steps for the i-th data point within the reflow region. For time step; The average dwell time is calculated based on the quality-weighted average: , In the formula, This represents the average length of stay.

[0014] Furthermore, the prediction of the location where the local flame in the reflow zone breaks through the shear layer based on the relationship between the maximum value of the heat flux modulus in the heat flux modulus distribution and the heat flux threshold specifically involves: The position of the maximum value of the heat flux modulus in the heat flux modulus distribution is taken as the candidate breakthrough point. When the ratio of the maximum value of the heat flux modulus to the heat flux threshold is greater than 1, it is determined that a breakthrough can be made.

[0015] Compared with the prior art, the above-described technical solution of the present invention has the following advantages: This invention abstracts the downstream recirculation zone of the burner into a two-dimensional idealized model. Based on the compressible fluid shear layer instability criterion and energy conservation relationship, it derives the heat flux threshold for energy deposition-induced shear layer instability in the recirculation zone. By accurately assessing whether energy deposition is sufficient to induce ignition shear layer instability and predicting the location of local flame breakthrough through the heat flux threshold, ignition guidance can be provided to improve the probability of successful ignition. This solves the problem in supersonic combustion of intrusive burner-stabilized systems where the local flame in the downstream recirculation zone of the burner is limited by the stable shear layer structure and cannot break through to develop into a global flame. Attached Figure Description

[0016] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein: Figure 1This is a flowchart illustrating the method for calculating the ISL instability heat flux threshold in the supersonic combustion recirculation zone according to a preferred embodiment of the present invention.

[0017] Figure 2 This is a schematic diagram illustrating the instability of the shear layer in the downstream recirculation zone of the burner induced by energy deposition in a preferred embodiment of the present invention.

[0018] Figure 3 This is a flowchart of the ISL instability threshold ignition method in the supersonic combustion reflow zone according to a preferred embodiment of the present invention.

[0019] Figure 4 This is a schematic diagram illustrating the calculation of the local flame volumetric heat generation rate in the recirculation zone in a preferred embodiment of the present invention.

[0020] Figure 5 This is a schematic diagram showing the distribution of inflow and outflow mass flow rates at the shear layer interface in the recirculation zone in a preferred embodiment of the present invention.

[0021] Figure 6 This is a diagram showing the results of simulation prediction of the shear layer breakthrough point in a preferred embodiment of the present invention.

[0022] Figure 7 This is a diagram showing the results of experimental identification of shear layer breakthrough points in a preferred embodiment of the present invention. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0024] like Figure 1 As shown, this invention discloses a method for calculating the ISL instability heat flux threshold in the supersonic combustion recirculation zone, comprising the following steps: S1: Construct a two-dimensional model of the downstream recirculation zone of the stabilizer. Based on the instability criterion of the compressible fluid shear layer and the energy conservation relationship, derive the heat flux threshold for energy deposition-induced shear layer instability in the recirculation zone.

[0025] S1-1: As Figure 2 As shown, the downstream recirculation zone of the burner contains reverse vortex pairs, which can be abstracted as a CSTR. Therefore, this invention assumes that the combustion in the recirculation zone releases heat to the interface between the recirculation zone and the shear layer, thereby disrupting the stable structure of the shear layer. The downstream recirculation zone of the burner is abstracted as a continuous stirred tank reactor (CSTR), and a two-dimensional model corresponding to the continuous stirred tank reactor is established. The two-dimensional model is divided along the XOZ symmetry plane, and only one side of the shear layer and half of the recirculation zone are analyzed.

[0026] S1-2: In incompressible fluids, the Kelvin-Helmholtz instability exists as a non-zero velocity difference, i.e., instability. In compressible fluids, the instability condition of the shear layer is approximately equal to the convective Mach number. Therefore, this invention introduces the convective Mach number to describe the disturbance propagation in compressible supersonic flow and constructs the instability condition of the shear layer based on the convective Mach number.

[0027] In compressible fluids, the instability condition of the shear layer is approximately: , This represents the convection Mach number. Therefore, when When judging the instability of the shear layer, This represents the convection Mach number.

[0028] The instability condition at this point is equivalently constructed as follows: , In the formula, The average flow velocity on the high-velocity side of the shear layer. The average flow velocity on the low-velocity side of the shear layer. for The corresponding average speed of sound, for The corresponding average speed of sound.

[0029] S1-3: Calculate the sound velocity and energy conservation formula after heating, substitute the sound velocity and energy conservation formula after heating into the instability condition to solve for the temperature rise, and obtain the heat flux threshold for shear layer instability based on the temperature rise.

[0030] S1-3-1: The heat release from combustion in the reflow zone increases the sound velocity on the low-speed side, i.e., the sound velocity after heating is: , In the formula, The speed of sound after heating. Specific heat ratio (heat capacity ratio) It is the gas ratio constant. The static temperature of the incoming flow on the low-velocity side of the shear layer. For temperature rise.

[0031] The energy conservation formula per unit area is: , In the formula, Energy per unit area For the duration of thermal deposition, The average density of the recirculation zone, The thickness of the reflow zone (in this embodiment, the reflow zone is idealized as a flat plate flow with a thickness of...) ), This refers to the isobaric specific heat capacity. The relationship between isobaric specific heat capacity and enthalpy change is: In the formula Enthalpy change per unit mass of medium.

[0032] S1-3-2: Substituting the aforementioned formulas for the velocity of sound after heating and the conservation of energy per unit area into the instability condition, the temperature rise is calculated as follows: .

[0033] S1-3-3: The heat flux threshold is constructed based on the temperature rise as follows: , In the formula, Heat flux threshold, unit: , This refers to the static temperature of the incoming flow on the high-speed side of the shear layer. In this embodiment, These parameters are extracted from non-reactive flow numerical values ​​through simulation. Obtained through streamline tracing.

[0034] like Figure 3 As shown, this invention also discloses a method for igniting the ISL instability heat flux threshold in the supersonic combustion recirculation region, comprising the following steps: S1: Construct a two-dimensional model of the downstream recirculation zone of the stabilizer. Based on the instability criterion of the compressible fluid shear layer and the energy conservation relationship, derive the heat flux threshold for energy deposition-induced shear layer instability in the recirculation zone.

[0035] S2: Combining two-dimensional models and non-reactive flow numerical simulation data, estimate the heat flux threshold distribution at the shear layer interface in the recirculation zone under specific operating conditions.

[0036] S2-1: As Figure 4 As shown, the shear layer interface is discretized into triangular patches. Based on the triangular patches, flow field parameters (velocity, density, temperature, area, normal vector, centroid, and mass flow rate, etc.) are extracted through non-reactive flow numerical simulation. The PSR model in CHEMKIN is used to input the re-entry characteristics of the re-flow region and output the volumetric heat generation rate of the re-flow region.

[0037] The reentry characteristics of the reflow region include the average residence time, which is calculated using Lagrange particle tracking. The specific calculation method is as follows: Generate local flow field data points, denoted as: , In the formula, For the i-th data point, Let i be the spatial coordinates of the i-th data point. Let i be the velocity vector of the i-th data point. Let be the density of the i-th data point. Let represent the oxygen mass fraction at the i-th data point. For the fuel mass fraction of the i-th data point, Let i be the temperature of the i-th data point. Let M be the pressure at the i-th data point, and M be the total number of data points. In the upstream of the reflow zone, a random seed method is used to track data points and determine whether the data points are entrained by the shear layer and enter the reflow zone. Count the data points entering and leaving the return flow area, and calculate the dwell time of the i-th data point within the tracking steps: , In the formula, Let i be the dwell time of the i-th data point. This is the number of numerical tracking steps for the i-th data point within the reflow region (i.e., the number of steps is only counted when the data point's location falls within the reflow region). For time step; The average dwell time is calculated based on the quality-weighted average: , In the formula, This represents the average length of stay.

[0038] The reentry characteristics of the reflow zone also include mass flow rate, total oxygen mass flow rate in the reflow zone, total fuel mass flow rate in the reflow zone, mass-weighted average temperature, and mass-weighted average pressure.

[0039] The method for calculating mass flow rate is as follows: , In the formula, Let be the mass flow rate of the infinitesimal surface at the i-th data point on the triangular facet (i.e., at the shear layer interface). Let be the normal velocity vector component of the infinitesimal surface at the i-th data point on the triangular facet (pointing towards the recirculation region indicates inflow, and vice versa indicates outflow). Let be the area of ​​the infinitesimal surface at the i-th data point on the triangular facet; in this embodiment, the mass flow rate in the re-entry feature of the re-entry zone on the interface includes the inflow mass flow rate and the outflow mass flow rate, and the distribution characteristics of the inflow mass flow rate and the outflow mass flow rate are as follows: Figure 5 As shown, Figure 5 (a) shows the distribution of the inflow mass flow rate. Figure 5 (b) is a distribution diagram of the outflow mass flow rate.

[0040] The total oxygen mass flow rate flowing into the reflux zone is: , In the formula, The total oxygen mass flow rate flowing into the reflux zone. This refers to summing over all infinitesimal elements (i.e., the data corresponding to the inflow mass flow rate) flowing into the recirculation zone. The calculation method for the total oxygen mass flow rate flowing out of the recirculation zone is the same as that for the total oxygen mass flow rate flowing into the recirculation zone.

[0041] The total fuel mass flow rate flowing into the recirculation zone is: , In the formula, The total fuel mass flow rate flowing into the recirculation zone is calculated using the same method as the total fuel mass flow rate flowing out of the recirculation zone.

[0042] The mass-weighted average inlet temperature is: , In the formula, The mass-weighted average inlet temperature is calculated using the same method as the mass-weighted average outlet temperature.

[0043] The quality-weighted average inlet pressure is: , In the formula, The mass-weighted average inlet pressure is calculated using the same method as the mass-weighted average outlet pressure.

[0044] S2-2: Based on the density gradient of the recirculation zone volumetric heat generation rate, i.e. density non-uniformity and interface curvature output by the PSR model in CHEMKIN, the power density is mass-weighted and corrected. A three-dimensional matrix field is constructed by projecting along the YOZ plane and XOZ plane. The interface heat flux modulus distribution field is obtained by projection calculation.

[0045] S3: Based on the relationship between the maximum value of the heat flux modulus in the heat flux modulus distribution and the heat flux threshold, predict the location where the local flame in the reflow zone breaks through the shear layer.

[0046] The position of the maximum value of the heat flux modulus in the heat flux modulus distribution is taken as the candidate breakthrough point. When the ratio of the maximum value of the heat flux modulus to the heat flux threshold is greater than 1, it is determined that a breakthrough can be made.

[0047] S4: Ignition is guided by the location of the local flame breaking through the shear layer in the reflow zone and the heat flux threshold.

[0048] The present invention also discloses a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements a method for calculating the ISL instability heat flux threshold in the supersonic combustion recirculation zone or a method for igniting the ISL instability heat flux threshold in the supersonic combustion recirculation zone.

[0049] The present invention also discloses an apparatus, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements a method for calculating the instability heat flux threshold of the supersonic combustion recirculation zone ISL or a method for igniting the instability heat flux threshold of the supersonic combustion recirculation zone ISL.

[0050] This invention abstracts the downstream recirculation zone of the burner into a two-dimensional idealized model, based on the compressible fluid shear layer instability criterion (compressible fluid Kelvin-Helmholtz instability criterion, i.e., convection Mach number). Based on the relationship between energy conservation and energy, the heat flux threshold for energy deposition-induced shear layer instability in the recirculation zone is derived. By accurately assessing whether energy deposition is sufficient to induce ignition shear layer instability and predicting the location of local flame breakthrough through the heat flux threshold, ignition is guided. This effectively solves the problem of determining whether a local flame can break through the shear layer when using lower ignition power in the recirculation zone during supersonic combustion based on an intrusive burner. It provides quantitative guidance for the design of strategies for auxiliary ignition oxygen replenishment or other ignition enhancement methods, and improves the success rate of central flame establishment.

[0051] This invention relates to a method for quantitatively predicting the development of localized flames into global flames and optimizing ignition strategies in supersonic combustion using low-power igniters such as plasma torches in invasive flame stabilizers. The invention provides a method for quantitatively calculating the heat flux threshold for shear layer instability induced by energy deposition in the recirculation zone, assessing breakthrough conditions, and predicting the location. This guides ignition strategy optimization, enabling efficient and reliable ignition under supersonic inflow, thus addressing the lack of quantitative criteria and location prediction for localized flame breakthrough in existing technologies.

[0052] This invention proposes for the first time a quantitatively calculable heat flux threshold formula, providing a general framework that can be further extended to scenarios with different igniter positions, supplementary oxygen flow rates, and equivalence ratios. By integrating reaction kinetics (PSR) and flow field data, it achieves accurate estimation of the heat flux modulus, enabling breakthrough location prediction and guiding the optimization of igniter layout and auxiliary oxygen supplementary flow rates for enhanced ignition. It has low computational cost and is suitable for rapid engineering evaluation and optimization.

[0053] To further demonstrate the effectiveness of the present invention, this embodiment uses the configuration in the prior art (see patent publication number CN120521230A) as an example for simulation experiments.

[0054] First, the equivalence ratio of the leading edge injection of the burner was set to 0.423, and ignition was performed using a 1.75kW plasma torch igniter. No combustion enhancement methods were employed (such as oxygen supplementation in the recirculation zone). The heat flux threshold for shear layer instability calculated in this invention is... The maximum value of the heat flux modulus at the interface is Therefore, under this operating condition, the local flame in the recirculation zone cannot break through the shear layer, and the calculation results are consistent with the experimental results.

[0055] In contrast, with a burner leading edge injection equivalence ratio of 0.423, ignition using a 1.75kW plasma torch igniter, and an oxygen supply mass flow rate to incoming mass flow rate ratio of 0.0016 in the recirculation zone, the heat flux threshold for shear layer instability calculated in this invention is... The maximum value of the heat flux modulus at the interface is In this operating condition, the local flame in the recirculation zone broke through the shear layer, and the calculated results were consistent with the experimental results.

[0056] Using the location of the maximum heat flux modulus as the prediction breakthrough point, the results of predicting the shear layer breakthrough point data are as follows: Figure 6 As shown, the experimental results for identifying the shear layer breakthrough point data are as follows: Figure 7 As shown, Figure 7 (a) is a top view showing the flame boundary in the flow-stretcher plane. Figure 7 (b) is a side view showing the flame boundary in the flow-normal plane. Figure 7 middle , , The dimensions are represented as dimensionless coordinates of the shear layer breakthrough location (dimensionlessized with respect to the width of the burner). These coordinates are found in the flame image sequence. The shear layer breakthrough coordinates corresponding to abrupt aspect ratio changes in the high-speed camera flame image sequence are identified by combining the contour self-similarity (e.g., centroid alignment, linear interpolation, maximum Euclidean distance pairs, etc.) of the abrupt aspect ratio changes. The error analysis results of the shear layer breakthrough points in the simulation prediction data and the actual experimental data are shown in Table 1.

[0057]

[0058] from Figure 6 , Figure 7 As can be seen from Table 1, the error between the predicted data and the experimental data is less than 6% (less than 2% in the X direction, less than 6% in the Y direction, and less than 2% in the Z direction), thus proving that the present invention can achieve a high-precision match between the predicted data and the experimental data.

[0059] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0060] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0061] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0062] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0063] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for calculating the ISL instability heat flux threshold in the supersonic combustion recirculation zone, characterized in that, include: A two-dimensional model of the downstream recirculation zone of the stabilizer is constructed. Based on the instability criterion of the compressible fluid shear layer and the energy conservation relationship, the heat flux threshold for energy deposition-induced shear layer instability in the recirculation zone is derived.

2. The method for calculating the ISL instability heat flux threshold in the supersonic combustion recirculation zone according to claim 1, characterized in that: The construction of the two-dimensional model of the downstream recirculation zone of the burner includes: The downstream recirculation zone of the flame stabilizer is abstracted as a continuous stirred tank reactor, and a two-dimensional model corresponding to the continuous stirred tank reactor is established. The two-dimensional model is divided along the XOZ symmetry plane, and only one side of the shear layer and half of the recirculation zone are analyzed.

3. The method for calculating the ISL instability heat flux threshold in the supersonic combustion recirculation zone according to claim 1, characterized in that: The heat flux threshold for shear layer instability induced by energy deposition in the recirculation region, derived based on the compressible fluid shear layer instability criterion and energy conservation relationship, includes: In compressible supersonic flow, a convective Mach number is introduced to describe the propagation of disturbances, and the instability conditions of the shear layer are constructed based on the convective Mach number. Calculate the sound velocity and energy conservation formula after heating, substitute the sound velocity and energy conservation formula after heating into the instability condition to solve for the temperature rise, and obtain the heat flux threshold for shear layer instability based on the temperature rise.

4. The method for calculating the ISL instability heat flux threshold in the supersonic combustion recirculation zone according to claim 3, characterized in that: The instability conditions of the shear layer are constructed based on the aforementioned convection Mach number, specifically as follows: when When judging the instability of the shear layer, Indicates the convection Mach number; The instability condition at this point is equivalently constructed as follows: ， In the formula, The average flow velocity on the high-velocity side of the shear layer. The average flow velocity on the low-velocity side of the shear layer. for The corresponding average speed of sound, for The corresponding average speed of sound.

5. The method for calculating the ISL instability heat flux threshold in the supersonic combustion recirculation zone according to claim 4, characterized in that: The speed of sound after heating is: ， In the formula, The speed of sound after heating. For specific heat ratio, It is the gas ratio constant. The static temperature of the incoming flow on the low-velocity side of the shear layer. For temperature rise; The energy conservation formula per unit area is: ， In the formula, Energy per unit area For the duration of thermal deposition, The average density of the recirculation zone, For the thickness of the reflux zone, This is the specific heat capacity at constant pressure.

6. The method for calculating the ISL instability heat flux threshold in the supersonic combustion recirculation zone according to claim 5, characterized in that: Substituting the aforementioned sound velocity after heating and the energy conservation formula per unit area into the instability condition to solve for the temperature rise, the heat flux threshold for shear layer instability is obtained based on the temperature rise, specifically: Substituting the aforementioned formulas for the velocity of sound after heating and the conservation of energy per unit area into the instability condition, the temperature rise is calculated as follows: ； The heat flux threshold is constructed based on the temperature rise as follows: ， In the formula, The heat flux threshold, The static temperature of the incoming flow on the high-speed side of the shear layer.

7. A method for ignition based on the ISL instability threshold in the supersonic combustion recirculation zone, characterized in that, include: The heat flux threshold for instability of the ISL in the supersonic combustion reflow zone is obtained using the method described in any one of claims 1-6. The heat flux threshold for instability of the shear layer is then estimated by combining the two-dimensional model and non-reactive flow numerical simulation data to estimate the heat flux modulus distribution of the heat flux threshold at the interface of the shear layer in the reflow zone under specific operating conditions. Based on the relationship between the maximum value of the heat flux modulus in the heat flux modulus distribution and the heat flux threshold, the location where the local flame in the reflow zone breaks through the shear layer is predicted, and ignition is guided by combining the location where the local flame in the reflow zone breaks through the shear layer and the heat flux threshold.

8. The method for igniting the ISL instability heat flux threshold in the supersonic combustion recirculation zone according to claim 7, characterized in that: The heat flux modulus distribution at the shear layer interface in the recirculation zone is estimated by combining two-dimensional model and non-reactive flow numerical simulation data, specifically as follows: The shear layer interface is discretized into triangular patches. Based on the triangular patches, the flow field parameters are extracted by non-reactive flow numerical simulation. The PSR model in CHEMKIN is used to input the re-entry characteristics of the re-flow region and output the volumetric heat generation rate of the re-flow region. Based on the density gradient of the volumetric heat generation rate in the recirculation region, the power density is mass-weighted and corrected. A three-dimensional matrix field is constructed by projecting along the YOZ and XOZ planes, and the interface heat flux modulus distribution field is obtained by projection calculation.

9. The method for igniting the ISL instability heat flux threshold in the supersonic combustion recirculation zone according to claim 8, characterized in that: The reentry characteristics of the reflow region include the average residence time, which is calculated using Lagrange particle tracking. The specific calculation method is as follows: Generate local flow field data points, denoted as: ， In the formula, For the i-th data point, Let i be the spatial coordinates of the i-th data point. Let i be the velocity vector of the i-th data point. Let be the density of the i-th data point. Let represent the oxygen mass fraction at the i-th data point. For the fuel mass fraction of the i-th data point, Let i be the temperature of the i-th data point. Let M be the pressure at the i-th data point, and M be the total number of data points. In the upstream of the reflow zone, a random seed method is used to track data points and determine whether the data points are entrained by the shear layer and enter the reflow zone. Count the data points entering and leaving the return flow area, and calculate the dwell time of the i-th data point within the tracking steps: ， In the formula, Let i be the dwell time of the i-th data point. Let i be the number of numerical tracking steps for the i-th data point within the reflow region. For time step; The average dwell time is calculated based on the quality-weighted average: ， In the formula, This represents the average length of stay.

10. The method for igniting the ISL instability heat flux threshold in the supersonic combustion recirculation zone according to claim 7, characterized in that: The method of predicting the location where the local flame breaks through the shear layer in the reflow zone based on the relationship between the maximum value of the heat flux modulus in the heat flux modulus distribution and the heat flux threshold is as follows: The position of the maximum value of the heat flux modulus in the heat flux modulus distribution is taken as the candidate breakthrough point. When the ratio of the maximum value of the heat flux modulus to the heat flux threshold is greater than 1, it is determined that a breakthrough can be made.

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