A method for quickly evaluating gas working substance injection heat reduction effect

Abstract

This invention proposes a rapid evaluation method for the heat reduction effect of gaseous working fluid ejection, comprising the following steps: (1) conducting three-dimensional numerical simulation of the external flow field to obtain surface heat flow pressure, streamline velocity vector, recovery enthalpy, and wall enthalpy; (2) determining the physical properties of the cooling working fluid and the surface cooling flow distribution; (3) calculating the ejection reduction factor for each grid cell on the surface; (4) calculating the surface streamline trajectory based on the streamline velocity vector; (5) calculating the heat reduction factor along the streamline length of the grid cell traversed by the streamline trajectory; (6) calculating the dimensionless position factor; (7) calculating the attenuation factor of the heat reduction effect on the left and right sides of the gas film coverage; (8) superimposing the heat reduction effect along the streamline to obtain the heat reduction factor on each grid cell on the surface. This invention rapidly evaluates the heat reduction effect based on the aerodynamic thermal environment, working fluid type, and working fluid flow rate, and is suitable for rapid evaluation and analysis during the scheme demonstration stage of active thermal protection systems. It can efficiently obtain the heat reduction effect under the outflow conditions of gaseous cooling working fluid.

Description

Technical Field

[0001] This invention belongs to the field of active thermal protection systems, specifically relating to a rapid evaluation method for the heat dissipation effect of gaseous working fluid ejection. Background Technology

[0002] When an aircraft flies at high speed within the atmosphere, it experiences intense friction with the surrounding air and strong compression of the air in front. Under the combined effects of viscous dissipation and shock wave compression, a large amount of kinetic energy from the high-speed incoming flow is converted into internal energy, causing the temperature within the shock layer to rise sharply, reaching over 10,000 K, resulting in severe aerodynamic heating of the aircraft surface. Therefore, it is essential to develop advanced thermal protection systems to overcome the "thermal barrier" problem in the development of high-speed aircraft. Active thermal protection technology is a key technology for overcoming the "thermal barrier" problem. Utilizing the "thermal blockage" effect formed by the outflow of gaseous cooling medium on the boundary layer is an important cooling mechanism for active thermal protection. Quantitatively evaluating the heat reduction effect under gaseous cooling medium outflow conditions is a crucial step in the design of active thermal protection systems. However, using full three-dimensional numerical simulation analysis presents challenges such as numerous design states and high simulation difficulty, making it unsuitable for rapid iterative design of active thermal protection systems. Therefore, there is an urgent need to establish a rapid evaluation method for the heat reduction effect of gaseous medium ejection. Summary of the Invention

[0003] To address the aforementioned issues, this invention proposes a rapid evaluation method for the heat reduction effect of gaseous working fluid ejection. This method rapidly evaluates the heat reduction effect based on the aerodynamic thermal environment, working fluid type, and working fluid flow rate. It is suitable for rapid evaluation and analysis during the feasibility study phase of active thermal protection systems and can efficiently obtain the heat reduction effect under gaseous cooling working fluid outflow conditions.

[0004] A rapid evaluation method for the heat dissipation effect of gaseous working fluid ejection includes the following steps: (1) For the outflow conditions, conduct aerodynamic and thermal numerical simulation of the external flow field of the aircraft to obtain the heat flow on each grid cell k on the surface of the aircraft. Surface pressure streamline direction vector Enthalpy restoration Wall enthalpy ; (2) Determine the molecular weight of the cooling working fluid based on its composition. M jet Determine the cooling fluid flow rate within each grid cell k on the aircraft surface. ; (3) For each grid cell k on the surface of the aircraft, calculate the local heat dissipation factor of the grid cell k. ; (4) For each grid cell i on the surface of the aircraft, determine the streamline trajectory from the end stagnation point to that grid cell; (5) For each grid cell k through which the streamline trajectory obtained in step (4) passes, calculate the heat reduction factor along the streamline length within that grid cell. ; (6) For each grid cell k through which the streamline trajectory passes, calculate the dimensionless position factor of grid cell k relative to grid cell i as follows; (7) Calculate the attenuation factor of the heat reduction effect of the air film covering effect of grid cell k relative to grid cell i. ; (8) Calculate and sum the heat reduction effect of the working fluid ejection in grid cell k on grid cell i to obtain the working fluid ejection heat reduction factor for each grid cell i. .

[0005] In step (3), the heat-reducing factor is ejected. for In the formula, For the surface heat flow determined in step (1), The surface pressure determined in step (1), The recovery enthalpy is determined in step (1). The wall enthalpy determined in step (1); M air The molecular weight of air. M jet and Given the molecular weight of the cooling working fluid and the working fluid flow rate within the grid cell determined in step (1), for laminar flow, N ranges from 0.67 to 0.72. The value of N is 0.25-0.4; for turbulent conditions, N is 0.2. The value is 0.33.

[0006] In step (4), the Runge-Kutta method is used to perform reverse streamline tracing calculations.

[0007] In step (5), the cooling factor for In the formula, The local excitation cooling factor of the grid cells obtained in step (3) is... l i Let k be the length of the streamline trajectory passing through grid cell k. S k This represents the area of ​​a grid cell.

[0008] In step (6), the dimensionless position factor is , In the formula, li Let be the length of the streamline trajectory from the end stagnation point to grid cell i. l k Let be the length of the streamline trajectory from the end stagnation point to grid cell k.

[0009] In step (7), the attenuation factor .

[0010] In step (7), the cooling factor The beneficial effects of this invention are as follows: (1) The present invention can quickly evaluate the heat reduction effect under the outflow condition of gas cooling working fluid, and significantly shorten the demonstration cycle of active thermal protection system scheme; (2) The present invention is based on the theoretical derivation of the compressible boundary layer under the working fluid ejection boundary condition, which has clear physical meaning and high computational efficiency. Attached Figure Description

[0011] Figure 1 This is a flowchart of a method for rapidly evaluating the heat-reducing effect of gaseous working fluid ejection. Detailed Implementation

[0012] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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 claimed by the present invention.

[0013] A rapid evaluation method for the heat dissipation effect of gaseous working fluid ejection includes the following steps: (1) For the outflow conditions, conduct aerodynamic and thermal numerical simulation of the external flow field of the aircraft to obtain the heat flow on each grid cell k (k is the grid cell number) on the surface of the aircraft. Surface pressure streamline direction vector Enthalpy restoration Wall enthalpy ; (2) Determine the molecular weight of the cooling working fluid based on its composition. M jet Based on the given coolant flow rate and surface distribution, determine the coolant flow rate within each grid cell k on the aircraft surface. ; (3) For each grid cell k on the surface of the aircraft, calculate the local heat dissipation factor of the grid cell k. ,in For the surface heat flow determined in step (1), The surface pressure determined in step (1), The recovery enthalpy is determined in step (1). The wall enthalpy determined in step (1); M air The molecular weight of air. M jet and Given the molecular weight of the cooling working fluid and the working fluid flow rate within the grid cells determined in step 2, for laminar flow, N ranges from 0.67 to 0.72. The value of N is 0.25-0.4; for turbulent conditions, N is 0.2. The value is 0.33.

[0014] (4) For each grid cell i on the surface of the aircraft, the streamline direction vector obtained in step (1) The Runge-Kutta method is used to perform reverse streamline tracing calculations to determine the streamline trajectory from the end stagnation point to the grid point; (5) For each grid cell k through which the streamline trajectory obtained in step (4) passes, calculate the heat reduction factor along the streamline length within that grid cell. ,in The local excitation cooling factor of the grid cells obtained in step (3) is... l i Let k be the length of the streamline trajectory passing through grid cell k. S k Area of ​​the grid cell; (6) For each grid cell k through which the streamline trajectory passes, calculate the dimensionless position factor of grid cell k relative to grid cell i as follows, where l i Let be the length of the streamline trajectory from the end stagnation point to grid cell i. l k Let be the length of the streamline trajectory from the end stagnation point to grid cell k. (7) Based on the position factor obtained in step (6) Calculate the attenuation factor of the heat reduction effect of air film coverage on grid cell k relative to grid cell i. : (8) For grid cell i, for each grid cell k through which the streamline trajectory obtained in step (4) passes, calculate and sum the heat reduction effect of the working fluid ejection in grid cell k on grid cell i, where The ejection cooling factor obtained in step (5) The heat reduction effect attenuation factor obtained in step (7) is used to obtain the working fluid excitation heat reduction factor for each grid cell i. The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A rapid evaluation method for the heat-reducing effect of gaseous working fluid ejection, characterized in that, The steps include the following: (1) For the outflow conditions, conduct aerodynamic and thermal numerical simulation of the external flow field of the aircraft to obtain the heat flow on each grid cell k on the surface of the aircraft. Surface pressure streamline direction vector Enthalpy restoration Wall enthalpy ; (2) Determine the molecular weight of the cooling working fluid based on its composition. M jet Determine the cooling fluid flow rate within each grid cell k on the aircraft surface. ; (3) For each grid cell k on the surface of the aircraft, calculate the local heat dissipation factor of the grid cell k. ; (4) For each grid cell i on the surface of the aircraft, determine the streamline trajectory from the end stagnation point to that grid cell; (5) For each grid cell k through which the streamline trajectory obtained in step (4) passes, calculate the heat reduction factor along the streamline length within that grid cell. ; (6) For each grid cell k through which the streamline trajectory passes, calculate the dimensionless position factor of grid cell k relative to grid cell i as follows; (7) Calculate the attenuation factor of the heat reduction effect of the air film covering effect of grid cell k relative to grid cell i. ; (8) Calculate and sum the heat reduction effect of the working fluid ejection in grid cell k on grid cell i to obtain the working fluid ejection heat reduction factor for each grid cell i. .

2. The method for rapid evaluation of the heat dissipation effect of gaseous working fluid ejection according to claim 1, characterized in that, In step (3), the heat-reducing factor is ejected. for In the formula, For the surface heat flow determined in step (1), The surface pressure determined in step (1), The recovery enthalpy is determined in step (1). The wall enthalpy determined in step (1); M air The molecular weight of air. M jet and Given the molecular weight of the cooling working fluid and the working fluid flow rate within the grid cell determined in step (1), for laminar flow, N ranges from 0.67 to 0.

72. The value of N is 0.25-0.4; for turbulent conditions, N is 0.

2. The value is 0.

33.

3. The method for rapid evaluation of the heat-reducing effect of gaseous working fluid ejection according to claim 1, characterized in that, In step (4), the Runge-Kutta method is used to perform reverse streamline tracing calculations.

4. The method for rapid evaluation of the heat dissipation effect of gaseous working fluid ejection according to claim 2, characterized in that, In step (5), the cooling factor for In the formula, The local excitation cooling factor of the grid cells obtained in step (3) is... l i Let k be the length of the streamline trajectory passing through grid cell k. S k This represents the area of ​​a grid cell.

5. The method for rapid evaluation of the heat dissipation effect of gaseous working fluid ejection according to claim 4, characterized in that, In step (6), the dimensionless position factor is ， In the formula, l i Let be the length of the streamline trajectory from the end stagnation point to grid cell i. l k Let be the length of the streamline trajectory from the end stagnation point to grid cell k.

6. The method for rapid evaluation of the heat dissipation effect of gaseous working fluid ejection according to claim 5, characterized in that, In step (7), the attenuation factor .

7. The method for rapid evaluation of the heat dissipation effect of gaseous working fluid ejection according to claim 6, characterized in that, In step (7), the cooling factor .

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