A flow passage configuration optimization design method for a powder scramjet combustor

Abstract

The application discloses a kind of powder scramjet combustion chamber flow passage configuration optimization design methods, belong to powder scramjet optimization field, including the following steps: S1, based on particle trajectory model, the motion state of particle is obtained;S2, the momentum equation, motion equation and drag equation of particle are decomposed;S3, the differential equation of particle velocity along the way distribution is deduced;S4, the residence time of particle in powder scramjet combustion chamber at different positions and penetration depth are solved;S5, the cross-sectional area of combustion chamber flow passage in quasi-one-dimensional calculation is corrected;S6, iteration step S1-step S5, until meeting end condition, output optimal combustion chamber flow passage configuration.The powder scramjet combustion chamber flow passage configuration optimization design method described above, by mathematical modeling, reduces the time required for simulation calculation, thereby reduces the calculation cost and calculation time, helps the design of engine combustion chamber flow passage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of powder scramjet optimization, and particularly relates to a flow passage configuration optimization design method for a powder scramjet combustion chamber. BACKGROUND

[0002] Hypersonic vehicles have broad application prospects in the fields of national defense and space transportation. In recent years, high Mach number and wide range have become the main research direction of hypersonic vehicles. The power device, as the main component of the hypersonic vehicle, is the key technology that determines the development of the hypersonic vehicle.

[0003] At present, liquid fuel ramjet is the main form of hypersonic vehicle power device, which has high specific impulse, and the fuel supply speed can be controlled by the control device, so the engine thrust can be freely changed, and even the engine can be turned off, so as to control the speed and direction. However, due to the fact that liquid fuel cannot be stored in the projectile body, it can only be filled before launch, and there are often difficulties in storage, complex structure, poor reliability and other disadvantages. The low density of liquid fuel, the easy dissociation of liquid fuel at high Mach number, the poor combustion stability, and the complex structure of the engine greatly limit the application of this type of power device.

[0004] Solid fuel ramjet with solid propellant as fuel is a new type of ramjet engine. Compared with liquid fuel ramjet, it has the advantages of relatively simple structure, light weight, high specific impulse, low cost, good safety, short combat response time, but also has the problem of low specific impulse and inaccurate thrust control during flight. Therefore, the research on solid fuel ramjet has attracted much attention in recent years.

[0005] In order to make up for the shortcomings of the two types of fuel engines and provide ideas for the research of new generation of hypersonic weapon power systems, some scholars have proposed the idea of using high-energy metals (aluminum, magnesium, boron, etc.) as the fuel of ramjet, i.e. powder fuel ramjet. Powder fuel (Al, Mg, B) has high energy and volume heat value, and there is no storage aging problem, so the fuel cost is greatly reduced; at the same time, powder fuel has higher insensitivity than solid propellant, thereby greatly improving the safety of powder fuel in the manufacturing, storage and use process, even in high overload environment.

[0006] However, there is currently a lack of scientific basis for the design of the flow passage of the engine combustion chamber, which greatly limits the performance optimization of the powder fuel ramjet. SUMMARY

[0007] The purpose of the present application is to provide a flow passage configuration optimization design method for a powder scramjet combustion chamber, which solves the above technical problems.

[0008] To achieve the above objectives, the present invention provides a method for optimizing the flow channel configuration of the combustion chamber of a powder scramjet engine, comprising the following steps:

[0009] S1. Based on the particle trajectory model, combined with quasi-one-dimensional thermodynamic calculations, the Mach number and static temperature distribution along the path are obtained, and the motion state of the particle is obtained.

[0010] S2. Based on the particle trajectory model, the particle motion is decomposed into the x and y directions, and the momentum equation, motion equation and drag force equation of the particle are decomposed.

[0011] S3. By combining the Mach number and static temperature distribution solutions described in step S1 with the momentum equation, motion equation, and drag force equation described in step S2, the differential equation for the particle velocity distribution along the path is derived.

[0012] S4. Integrate the differential equation described in step S3 using the equation of motion to solve for the residence time and penetration depth of the particles at different positions in the combustion chamber of the powder scramjet engine.

[0013] S5. Estimate the height and length of the combustion chamber flow channel by the penetration depth, and correct the cross-sectional area of ​​the combustion chamber flow channel in the quasi-one-dimensional calculation described in step S1 based on the estimation results.

[0014] S6. Iterate through steps S1 to S5 until the termination condition is met, and output the optimal combustion chamber flow channel configuration.

[0015] Preferably, in step S1, the particle orbital model expression is as follows:

[0016]

[0017] In the formula, V x R is the velocity of the particle in the x-direction; M is the Mach number; k is the Boltzmann constant; R is the gas constant.

[0018] The expression for the differential equation along the Mach number is as follows:

[0019]

[0020] In the formula, The rate of change of Mach number M along the x-direction; γ is the specific heat ratio; T t Temperature; C f denoted as the coefficient of friction; D is the diameter of the combustion chamber flow channel; A is the cross-sectional area of ​​the combustion chamber flow channel.

[0021] The differential equation for static temperature is expressed as follows:

[0022]

[0023] In the formula, c is the rate of change of static temperature T along the x-direction; p Specific heat capacity at constant pressure; h t Enthalpy of the fluid.

[0024] Preferably, in step S2, the particle dynamics equations are constructed using Lagrange coordinates in the Cartesian coordinate system:

[0025]

[0026] In the formula, X p V is the particle position vector; p F is the velocity vector of the particle; p F is the resistance force per unit mass of particle; F is the gravity acting on the particle.

[0027] Momentum equation:

[0028]

[0029] In the formula, v px and v py F represents the particle's velocity in the x and y directions, respectively; px and F py These represent the drag forces of the particle in the x and y directions, respectively; f py Indicates mass force;

[0030] Equations of motion:

[0031]

[0032] Assuming the incoming flow has only velocity in the x-direction, the drag force equation is expressed as follows:

[0033]

[0034] In the formula, C Dx and C Dy These represent the drag forces in the x and y directions, respectively; ρ represents the fluid density; ρ p Indicates particle density; d p Indicates particle size; V x This represents the velocity of the fluid in the x-direction.

[0035] Preferably, in step S3, the following is set:

[0036] f py =-g (12);

[0037] Combining (10), (11), (12), (6), and (7), we get:

[0038]

[0039] Substituting formula (1) into formula (13) yields:

[0040]

[0041] Dividing formula (15) by formula (8) yields V. px Solution regarding the x-direction:

[0042]

[0043] Preferably, in step S4, formula (8) is rewritten in reciprocal form, and the time t required for the particles to pass through the combustion chamber is calculated using formula (16):

[0044]

[0045] Decompose the integral x into multiple x i The element segment provides the time t required for a particle to reach any position in the combustion chamber. i ;

[0046] Meanwhile, the velocity solution V in the y-direction of the particle is obtained through formula (14). py =V py (t), perform piecewise integration to obtain different x values ​​in the combustion chamber. i Location and corresponding time t i Penetration depth h i :

[0047]

[0048] In the formula, V Py (t) represents the function of the particle's velocity in the y direction as a function of time;

[0049] Then, assuming x is the dimensionless distance along the path, we consider all time points t... i Corresponding penetration depth h i Add them up to calculate the penetration depth of the entire combustion chamber:

[0050]

[0051] In the formula, L represents the length from the injector inlet to the outlet of the burner; t(x) represents the time corresponding to the dimensionless distance x along the path.

[0052] Preferably, in step S5, the length L from the burner's injection inlet to the outlet is considered as the combustion chamber flow path length L. f :

[0053] L f =L (19);

[0054] Meanwhile, assuming the cross-section of the combustion chamber flow channel is rectangular, the particles at position x... i The maximum offset at position x is considered as position x i The height H of the flow channel f :

[0055] H f =max(h i (20);

[0056] Calculate the cross-sectional area A' of the modified flow channel:

[0057] A' = W × h i (twenty one);

[0058] In the formula, W is the designed flow channel width.

[0059] Preferably, in step S6, the cross-sectional area A' of the corrected flow channel is replaced with A in formulas (2) and (3) for iteration.

[0060] Therefore, the present invention employs the above-mentioned method for optimizing the flow channel configuration of a powder scramjet engine combustion chamber, which has the following beneficial effects:

[0061] Optimizing the combustion chamber flow channel configuration can further improve the overall performance of the engine. It can be used to explore the relationships between different incoming flows, particle sizes, injection angles, penetration depths, and residence times. For example:

[0062] Improved combustion efficiency: The optimized flow channel configuration helps to better control the movement trajectory of particles, improving fuel mixing and combustion efficiency;

[0063] Enhanced thrust output: A better combustion chamber design can improve airflow organization, thereby increasing the engine's thrust output.

[0064] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0065] Figure 1 This is a flowchart of a flow channel configuration optimization design method for a powder scramjet engine combustion chamber according to the present invention.

[0066] Figure 2 This is a diagram showing the distribution of penetration depth along the jet when spraying vertically at 90° as described in the simulation experiment;

[0067] Figure 3 This is a graph showing the change of the y-direction velocity of particles with different sizes (2-6μm) over time during a 90° vertical injection as described in the simulation experiment.

[0068] Figure 4This is a graph showing the variation of the velocity along the x-direction of particles of different sizes (2-6μm) during a 90° vertical injection as described in the simulation experiment.

[0069] Figure 5 This is a diagram showing the penetration depth distribution of particles of different sizes (20-60μm) during a 90° vertical injection as described in the simulation experiment.

[0070] Figure 6 This is a graph showing the change of the y-direction velocity of particles with different sizes (20-60μm) over time during a 90° vertical injection as described in the simulation experiment.

[0071] Figure 7 This is a graph showing the variation of the x-direction velocity of particles with different sizes (20-60μm) during a 90° vertical injection as described in the simulation experiment.

[0072] Figure 8 This is a distribution diagram along the path of the penetration depth of particles with different sizes (2-6μm) during 120° reverse injection as described in the simulation experiment. Detailed Implementation

[0073] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of the present invention and are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions.

[0074] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as a process, method, system, product, or server that includes a series of steps or units, not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or device.

[0075] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0076] like Figure 1 As shown, a method for optimizing the flow channel configuration of a powder scramjet engine combustion chamber includes the following steps:

[0077] S1. Based on the particle trajectory model, combined with quasi-one-dimensional thermodynamic calculations, the Mach number and static temperature distribution along the path are obtained, and the motion state of the particle is obtained.

[0078] In step S1, the particle orbital model expression is as follows:

[0079]

[0080] In the formula, V x R is the velocity of the particle in the x-direction; M is the Mach number; k is the Boltzmann constant; R is the gas constant.

[0081] The expression for the differential equation along the Mach number is as follows:

[0082]

[0083] In the formula, The rate of change of Mach number M along the x-direction; γ is the specific heat ratio; T t Temperature; C f denoted as the coefficient of friction; D is the diameter of the combustion chamber flow channel; A is the cross-sectional area of ​​the combustion chamber flow channel.

[0084] The differential equation for static temperature is expressed as follows:

[0085]

[0086] In the formula, c is the rate of change of static temperature T along the x-direction; p Specific heat capacity at constant pressure; h t Enthalpy of the fluid.

[0087] S2. Based on the particle trajectory model, the particle motion is decomposed into the x and y directions, and the momentum equation, motion equation and drag force equation of the particle are decomposed.

[0088] In step S2, the particle dynamics equations are constructed using Lagrange coordinates in the Cartesian coordinate system:

[0089]

[0090] In the formula, X p V is the particle position vector; p F is the velocity vector of the particle; p F is the resistance force per unit mass of particle; F is the gravity acting on the particle.

[0091] The resistance F experienced by a unit mass of particle p The expression is as follows:

[0092]

[0093] In the formula, V is the velocity vector of the gas phase; C D d is the drag coefficient; p Particle size;

[0094] Traction coefficient C D The expression is as follows:

[0095]

[0096] In the formula, Re p The particle Reynolds number;

[0097] Particle Reynolds number Re p The expression is as follows:

[0098]

[0099] In the formula, μ is the dynamic viscosity of the fluid;

[0100] Momentum equation:

[0101]

[0102] In the formula, v px and v py F represents the particle's velocity in the x and y directions, respectively; px and F py These represent the drag forces of the particle in the x and y directions, respectively; f py Indicates mass force;

[0103] Equations of motion:

[0104]

[0105] Assuming the incoming flow has only velocity in the x-direction, the drag force equation is expressed as follows:

[0106]

[0107]

[0108] In the formula, C Dx and C Dy These represent the drag forces in the x and y directions, respectively; ρ represents the fluid density; ρ p Indicates particle density; d p Indicates particle size; V x This represents the velocity of the fluid in the x-direction;

[0109] S3. By combining the Mach number and static temperature distribution solutions described in step S1 with the momentum equation, motion equation, and drag force equation described in step S2, the differential equation for the particle velocity distribution along the path is derived.

[0110] In step S3, the following is set:

[0111] f py =-g (12);

[0112] Combining (10), (11), (12), (6), and (7), we get:

[0113]

[0114] Substituting formula (1) into formula (13) yields:

[0115]

[0116] Dividing formula (15) by formula (8) yields V. px Solution regarding the x-direction:

[0117]

[0118] S4. Integrate the differential equation described in step S3 using the equation of motion to solve for the residence time and penetration depth of the particles at different positions in the combustion chamber of the powder scramjet engine.

[0119] In step S4, formula (8) is rewritten in reciprocal form, and the time t required for the particles to pass through the combustion chamber is calculated using formula (16):

[0120]

[0121] Decompose the integral x into multiple x i The element segment provides the time t required for a particle to reach any position in the combustion chamber. i ;

[0122] Meanwhile, the velocity solution V in the y-direction of the particle is obtained through formula (14). py =V py (t), perform piecewise integration (the step size selected for integration is less than 10). -6 (level), to obtain different x of the combustion chamber i Location and corresponding time t i Penetration depth h i :

[0123]

[0124] In the formula, V Py (t) represents the function of the particle's velocity in the y direction as a function of time;

[0125] Then, assuming x is the dimensionless distance along the path, we consider all time points t... i Corresponding penetration depth h i Add them up to calculate the penetration depth of the entire combustion chamber:

[0126]

[0127] In the formula, L represents the length from the injector inlet to the outlet of the burner; t(x) represents the time corresponding to the dimensionless distance x along the path.

[0128] In this embodiment, particles with large diameters (e.g., larger than 20 μm) or large radial velocities (greater than 200 m / s) will have a high penetration depth, thus impacting the engine wall. Therefore, the velocities in the x and y directions after reflection can be calculated using the velocity attenuation coefficient.

[0129] S5. Estimate the height and length of the combustion chamber flow channel by the penetration depth, and correct the cross-sectional area of ​​the combustion chamber flow channel in the quasi-one-dimensional calculation described in step S1 based on the estimation results.

[0130] In step S5, the length L from the burner's injection inlet to the outlet is considered as the combustion chamber flow path length L. f :

[0131] L f =L (19);

[0132] Meanwhile, assuming the cross-section of the combustion chamber flow channel is rectangular, the particles at position x... i The maximum offset at position x is considered as position x i The height H of the flow channel f :

[0133] H f =max(h i (20);

[0134] Calculate the cross-sectional area A' of the modified flow channel:

[0135] A' = W × h i (twenty one);

[0136] In the formula, W is the designed flow channel width.

[0137] S6. Iterate through steps S1 to S5 until the termination condition is met, and output the optimal combustion chamber flow channel configuration.

[0138] In step S6, the cross-sectional area A' of the corrected flow channel is replaced with A in formulas (2) and (3) for iteration.

[0139] Simulation experiment:

[0140] like Figure 2 As shown, the horizontal axis X is the axial distance of the combustion chamber. It can be seen that when the particle size is between 2μm and 6μm, the particle stays in the combustion chamber for a period of time and the penetration depth after leaving the combustion chamber.

[0141] like Figure 3As shown, the horizontal axis t represents time (s). It can be seen that the y-direction velocity of small-diameter particles will quickly tend to the mainstream y-direction velocity, which has a significant impact on the penetration depth.

[0142] like Figure 4 As shown, the horizontal axis x represents the axial distance of the combustion chamber, and the vertical axis represents the particle velocity in the x-direction.

[0143] like Figure 5 As shown, it can be seen that when the particle size is between 20μm and 60μm, the time the particles stay in the combustion chamber and the penetration depth after leaving the combustion chamber are significant. It is evident that the penetration depth of large-diameter particles in the combustion chamber cannot be stabilized in a short time, and there is a wall reflection phenomenon.

[0144] like Figure 6 As shown, it can be seen that the y-axis velocity of large-diameter particles is less affected by the mainstream compared to small-diameter particles. Figure 7 As shown, it can be seen that the x-direction velocity of large-diameter particles is less affected by the mainstream compared to small-diameter particles.

[0145] like Figure 8 As shown, it can be seen that the time a particle stays in the combustion chamber and its penetration depth after leaving the combustion chamber are both related to the particle size ranging from 2μm to 6μm. Figure 8 As can be seen from the sub-diagram, the larger the particle size, the farther it is sprayed in the reverse direction.

[0146] This demonstrates that the present invention can be used to explore the relationships between different incoming flows, different particle sizes, different injection angles, penetration depths, and residence times.

[0147] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for optimizing the flow channel configuration of a powder scramjet engine combustion chamber, characterized in that: Includes the following steps: S1. Based on the particle trajectory model, combined with quasi-one-dimensional thermodynamic calculations, the Mach number and static temperature distribution along the path are obtained, and the motion state of the particle is obtained. S2. Based on the particle trajectory model, the particle motion is decomposed into the x and y directions, and the momentum equation, motion equation and drag force equation of the particle are decomposed. S3. By combining the Mach number and static temperature distribution solutions described in step S1 with the momentum equation, motion equation, and drag force equation described in step S2, the differential equation for the particle velocity distribution along the path is derived. S4. Integrate the differential equation described in step S3 using the equation of motion to solve for the residence time and penetration depth of the particles at different positions in the combustion chamber of the powder scramjet engine. S5. Estimate the height and length of the combustion chamber flow channel by the penetration depth, and correct the cross-sectional area of ​​the combustion chamber flow channel in the quasi-one-dimensional calculation described in step S1 based on the estimation results. S6. Iterate through steps S1 to S5 until the termination condition is met, and output the optimal combustion chamber flow channel configuration.

2. The method for optimizing the flow channel configuration of a powder scramjet engine combustion chamber according to claim 1, characterized in that: In step S1, the particle orbital model expression is as follows: In the formula, V x R is the velocity of the particle in the x-direction; M is the Mach number; k is the Boltzmann constant; R is the gas constant. The differential equation for Mach number is expressed as follows: In the formula, The rate of change of Mach number M along the x-direction; γ is the specific heat ratio; T t Temperature; C f denoted as the coefficient of friction; D is the diameter of the combustion chamber flow channel; A is the cross-sectional area of ​​the combustion chamber flow channel. The differential equation for static temperature is expressed as follows: In the formula, c is the rate of change of static temperature T along the x-direction; p Specific heat capacity at constant pressure; h t Enthalpy of the fluid.

3. The method for optimizing the flow channel configuration of a powder scramjet engine combustion chamber according to claim 2, characterized in that: In step S2, the particle dynamics equations are constructed using Lagrange coordinates in the Cartesian coordinate system: In the formula, X p V is the particle position vector; p F is the velocity vector of the particle; p F is the resistance force per unit mass of particle; F is the gravity acting on the particle. Momentum equation: In the formula, v px and v py F represents the particle's velocity in the x and y directions, respectively; px and F py These represent the drag forces of the particle in the x and y directions, respectively; f py Indicates mass force; Equations of motion: Assuming the incoming flow has only velocity in the x-direction, the drag force equation is expressed as follows: In the formula, C Dx and C Dy These represent the drag forces in the x and y directions, respectively; ρ represents the fluid density; ρ p Indicates particle density; d p Indicates particle size; V x This represents the velocity of the fluid in the x-direction.

4. The method for optimizing the flow channel configuration of a powder scramjet engine combustion chamber according to claim 3, characterized in that: In step S3, the following is set: f py =-g (12); Combining (10), (11), (12), (6), and (7), we get: Substituting formula (1) into formula (13) yields: Dividing formula (15) by formula (8) yields V. px Solution regarding the x-direction:

5. The method for optimizing the flow channel configuration of a powder scramjet engine combustion chamber according to claim 4, characterized in that: In step S4, formula (8) is rewritten in reciprocal form, and the time t required for the particles to pass through the combustion chamber is calculated using formula (16): Decompose the integral x into multiple x i The element segment provides the time t required for a particle to reach any position in the combustion chamber. i ; Meanwhile, the velocity solution V in the y-direction of the particle is obtained through formula (14). py =V py (t), perform piecewise integration to obtain different x values ​​in the combustion chamber. i Location and corresponding time t i Penetration depth h i : In the formula, V Py (t) represents the function of the particle's velocity in the y direction as a function of time; Then, assuming x is the dimensionless distance along the path, we consider all time points t... i Corresponding penetration depth h i Add them up to calculate the penetration depth of the entire combustion chamber: In the formula, L represents the length from the injector inlet to the outlet of the burner; t(x) represents the time corresponding to the dimensionless distance x along the path.

6. The method for optimizing the flow channel configuration of a powder scramjet engine combustion chamber according to claim 5, characterized in that: In step S5, the length L from the burner's injection inlet to the outlet is considered as the combustion chamber flow path length L. f : L f =L (19); Meanwhile, assuming the cross-section of the combustion chamber flow channel is rectangular, the particles at position x... i The maximum offset at position x is considered as position x i The height H of the flow channel f : H f =max(h i ) (20); Calculate the cross-sectional area A' of the modified flow channel: A'=W×h i (21); In the formula, W is the designed flow channel width.

7. The method for optimizing the flow channel configuration of a powder scramjet engine combustion chamber according to claim 6, characterized in that: In step S6, the cross-sectional area A' of the corrected flow channel is replaced with A in formulas (2) and (3) for iteration.

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