Rapid Calculation Method for Rear Infrared Radiation Intensity of S-Bend Nozzle

Abstract

This invention discloses a rapid calculation method for the rearward infrared radiation intensity of an S-curve nozzle, belonging to the field of infrared radiation characteristic simulation of aero-engine exhaust systems. The method comprises the following steps: determining the design parameters of the S-curve nozzle and exhaust mixer components; establishing projection models of the key shielding sections of the exhaust mixer and S-curve nozzle; calculating the projected area of ​​each component after shielding by the S-curve nozzle using an image method; calculating the flow field parameter distribution and component surface temperature of the S-curve nozzle; calculating the axial length and volume of the visible region of the exhaust gas in the S-curve nozzle; calculating the spectral transmittance and spectral radiance of the exhaust gas along the nozzle outlet centerline within the visible region of the exhaust gas, as well as the spectral radiance intensity of the exhaust gas; calculating the infrared spectral radiance intensity of the wall surface; and integrating the spectral radiance to obtain the total infrared radiation intensity. This method solves the problems of existing technologies where the simulation calculation of the infrared radiation characteristics of S-curve nozzles is complex and time-consuming, and rapid calculation methods are only applicable to axisymmetric nozzles and cannot simulate the shielding structural characteristics of S-curve nozzles.

Description

Technical Field

[0001] This invention belongs to the field of infrared radiation characteristic simulation of aero-engine exhaust systems, specifically involving a rapid calculation method for the rearward infrared radiation intensity of an S-shaped nozzle. Background Technology

[0002] Infrared stealth performance is one of the important indicators for measuring the advancement of modern fighter jets. New infrared-guided weapons are seriously threatening the survivability of fighter jets, necessitating research into infrared stealth design. The exhaust system of an aircraft engine is the primary source of infrared radiation for a fighter jet. The high-temperature components within the exhaust system and the ejected high-temperature exhaust gases generate a large amount of infrared radiation, making them primary targets for infrared-guided weapons. S-bend technology, as a type of infrared suppression technology for exhaust systems, has attracted widespread attention from domestic and international military research institutions due to its significant advantage in low infrared detectability. Its S-shaped curved surface can effectively shield high-temperature components such as the engine's low-pressure turbine, tail cone, and mixer. Simultaneously, the large aspect ratio of the rectangular nozzle enhances the mixing process of high-temperature exhaust gases with the low-temperature atmosphere, effectively suppressing infrared radiation from high-temperature components and exhaust gases in the exhaust system.

[0003] The current method for simulating the infrared radiation characteristics of S-curve nozzles involves using computational fluid dynamics (CFD) to calculate the distribution characteristics of flow field parameters inside and outside the nozzle, and then obtaining the target's infrared radiation intensity through methods such as the inverse Monte Carlo method or the discrete transfer method. This method can obtain detailed target infrared radiation characteristics, but the calculation process depends on the discrete grid scheme, flow field calculation, and solving the radiation transfer equation. For complex nozzle configurations like S-curve nozzles with multiple coupled design parameters, the computational cost of obtaining the target's external infrared characteristics within the complete design space using this method is too high, making it unacceptable in the early stages of exhaust system infrared stealth design and engine overall design. Existing technologies for modeling and infrared radiation prediction of turbofan engines with ejector nozzles are only applicable to axisymmetric nozzles and are difficult to apply to S-curve nozzles with complex shielding relationships. Therefore, it is necessary to develop a new method for rapidly calculating infrared radiation intensity specifically for the shielding structure characteristics of S-curve nozzles, enabling rapid evaluation of their infrared radiation characteristics. Summary of the Invention

[0004] The technical problem to be solved:

[0005] To overcome the shortcomings of existing technologies, this invention provides a rapid calculation method for the rearward infrared radiation intensity of an S-curve nozzle. This method can quickly calculate the infrared radiation characteristics of S-curve nozzles with different design parameters, and decompose the infrared radiation intensity of different components and the infrared radiation intensity of the combustion gas, while ensuring a certain level of calculation accuracy. This addresses the problems of existing technologies where the simulation calculation of the infrared radiation characteristics of S-curve nozzles is complex and time-consuming, and the rapid calculation method is only applicable to axisymmetric nozzles and cannot simulate the shielding structural characteristics of S-curve nozzles.

[0006] The technical solution of this invention is: a method for rapidly calculating the infrared radiation intensity of an S-curve nozzle in the rearward direction, the specific steps of which are as follows:

[0007] Step 1: Determine the design parameters for the S-curve nozzle and exhaust mixer components;

[0008] Step 2: Project the exhaust mixer component backward to establish an exhaust mixer projection model without S-curve nozzle obstruction; project the key obstruction section of the S-curve nozzle backward to establish an S-curve nozzle key obstruction section projection model without obstruction, with the number of models matching the number of key obstruction sections.

[0009] Step 3: Calculate the projected area of ​​each component after the S-curve nozzle is blocked using the image method;

[0010] Step 4: Calculate the flow field parameter distribution and component surface temperature of the S-bend nozzle;

[0011] Step 5: Calculate the axial length and volume of the visible area of ​​the S-bend nozzle;

[0012] Step 6: Based on the flow field parameter distribution obtained in Step 4 and the axial length of the visible gas region obtained in Step 5, calculate the spectral transmittance and spectral radiance of the gas on the nozzle outlet centerline within the visible gas region; correct the projected area of ​​the gas according to the volume of the visible region obtained in Step 5, and calculate the spectral radiance of the gas.

[0013] Step 7: Calculate the infrared spectral radiation intensity of the wall surface based on the component projected area obtained in Step 3, the component surface temperature obtained in Step 4, and the gas spectral transmittance obtained in Step 6;

[0014] Step 8: Add the gas and wall spectral radiation intensities obtained in Step 6 and Step 7 to calculate the total infrared spectral radiation intensity of the S-bend nozzle, and integrate the spectral radiation brightness to obtain the total infrared radiation intensity.

[0015] A further technical solution of the present invention is: the design parameters of the S-bend nozzle include the nozzle inlet diameter, the S-bend section outlet profile parameters, the S-bend section offset, and the nozzle length; the design parameters of the exhaust mixer component include the tail cone diameter, the inner diameter, the outer diameter, the mixer outlet diameter, and the exhaust mixer length.

[0016] A further technical solution of the present invention is: the key shielding section of the S-bend nozzle includes a first bend exit section, a second bend exit section, and a nozzle exit section.

[0017] A further technical solution of the present invention is: the calculation method in step 3 is as follows:

[0018] Step 3.1: Using the geometric center of the exhaust mixer projection model as the center of all images, map the unobstructed exhaust mixer projection model and the S-bend nozzle key obstruction section projection model onto the exhaust mixer projection map and the S-bend nozzle key obstruction section projection map respectively, according to fixed geometric dimensions and pixel scale. Determine the relative position of the key obstruction section on the image based on the offset.

[0019] Step 3.2: Using the exhaust mixer projection image as the base image and all key shielding section projection images as masks, calculate the intersection of the mask and the base image by pixel AND operation according to the axial order of the key shielding sections on the S-curve nozzle, and update the base image in real time according to the intersection.

[0020] Step 3.3: Calculate the visible area projection of each component of the exhaust mixer based on the pixel count results and scale of the base map, and distinguish the projection area of ​​different components according to the difference in pixel values; similarly, calculate the nozzle exit area based on the pixel count results of the nozzle exit section projection map, and subtract the projection area of ​​each component to obtain the projection area of ​​the S-curve nozzle wall.

[0021] A further technical solution of the present invention is: in step 3.1, the mixer projection map distinguishes different components by pixel values, the internal area of ​​the nozzle of the key obstruction section on the key obstruction section projection map is filled with the maximum pixel value, and the pixel values ​​of the area outside the projection model in the image are all set to 0.

[0022] A further technical solution of the present invention is: in step 4, the flow field parameter distribution inside the S-bend nozzle and the jet is calculated according to a one-dimensional flow model. The flow field parameters include the gas temperature, pressure and combustion product component concentration distribution; at the same time, the surface temperature of each component of the S-bend nozzle and the exhaust system is calculated according to the aerodynamic parameters at the inlet of the S-bend nozzle.

[0023] A further technical solution of the present invention is: in step 5, a fitting function is established based on the relationship between the design parameters of the S-bend nozzle and the axial length and volume of the visible gas region, and the axial length and volume of the visible gas region of the S-bend nozzle under the current design parameters are calculated based on the fitting function.

[0024] A further technical solution of the present invention is as follows: In step 5, fitting functions for the axial length and volume S-bend nozzle design parameters of the visible gas region are established using the Boltzmann formula and the Rogerstik formula, respectively, as follows:

[0025]

[0026]

[0027] In the formula, L v V is the axial length of the visible gas region. vL2: Length of the first bend, L3: Length of the second bend, L4: Length of the equal section, ΔY2: Longitudinal offset of the second bend, A e This represents the nozzle exit area.

[0028] A further technical solution of the present invention is: in step 6, the gas spectral transmittance and gas spectral radiance are calculated using a narrow band model and the CG band approximation method.

[0029] Beneficial effects

[0030] The beneficial effects of this invention are as follows: This invention calculates the rearward projected area of ​​each component of an S-bend nozzle under different design parameters using an image method, calculates the flow field parameter distribution of the S-bend nozzle using a one-dimensional flow model, and calculates the visible region length and volume of the gas combustion gas using functional relationships to correct the gas combustion gas radiation. This avoids dependence on discrete grid schemes, computational fluid dynamics methods, and solving radiative transfer equations, and enables rapid calculation of the rearward infrared radiation intensity of S-bend nozzles with different design parameters. It solves the problem that traditional rapid calculation methods for nozzle infrared characteristics are not applicable to S-bend nozzles and cannot simulate their shading characteristics. The technical challenge of this invention lies in rapidly and accurately calculating the rearward projected area of ​​each component under arbitrary S-bend nozzle design parameters using an image method, determining the visible region and volume of the gas combustion gas within the S-bend nozzle based on functional relationships, and correcting the gas combustion gas radiation characteristics.

[0031] The embodiments of the present invention have been verified to investigate the effects of different two-bend offset S-bend nozzles and different internal inlet total temperatures on the calculation accuracy. The results are shown in Tables 1 and 2, with the maximum error being 12.52 W / sr. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of an optional S-curve nozzle geometric model and its design parameters according to an embodiment of the present invention;

[0033] Figure 2 This is a flowchart of a method for rapidly calculating the infrared radiation intensity of an S-curve nozzle, which is optional according to an embodiment of the present invention.

[0034] Figure 3 This is a schematic diagram of the rearward projected area of ​​each component of the S-curve nozzle calculated using the image method;

[0035] Figure 4 This is a schematic diagram showing the length and volume of the visible gas area in S-shaped nozzles with different offsets.

[0036] Explanation of reference numerals in the attached drawings: 1. Outer duct inlet, 2. Mixer, 3. Tail cone, 4. Inner duct inlet, 5. First bend exit section, 6. Nozzle exit section, 7. Exhaust mixer, 8. S-bend nozzle, 9. Centerline of S-bend nozzle, 10. Mixer projection model, 11. Mixer projection view, 12. First bend exit section mask, 13. First bend exit base view, 14. Nozzle exit section mask, 15. Nozzle exit base view, 16. Nozzle exit centerline.

[0037] D t : Tail cone diameter; D c : Inner diameter; D b : Outer diameter; D m : Mixer outlet diameter; L1: Mixing section length; D i : S-bend nozzle inlet diameter; L2: First bend section length; ΔY1: First bend longitudinal offset; W1: First bend outlet width; H1: First bend outlet height; R1: First bend outlet rounding radius; L3: Second bend section length; ΔY2: Second bend section longitudinal offset; W2: Second bend outlet width; H2: Second bend outlet height; R2: Second bend outlet rounding radius; L4: Equivalent section length. Detailed Implementation

[0038] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0039] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0040] Reference Figure 1 As shown, this embodiment targets an S-bend nozzle with a double-bend configuration. The exhaust mixer 7 includes an outer inlet 1, a tail cone 3, a mixer 2, and an inner inlet 4. The figure also shows the main design parameters of the exhaust mixer and the S-bend nozzle. The exhaust mixer design parameters include the tail cone diameter D. t Inner diameter D c Outer diameter D b Mixer outlet diameter D m and the mixing section length L1. S-curve nozzle design parameters include nozzle inlet diameter D. iThe dimensions of the first bend section are: length L2, longitudinal offset ΔY1, outlet width W1, outlet height H1, and outlet rounding radius R1; length of the second bend section is: length L3, longitudinal offset ΔY2, outlet width W2, outlet height H2, and outlet rounding radius R2; and length of the equal section is: L4. In this embodiment, the mixer outlet diameter D... m Greater than the inner diameter D c Nozzle inlet diameter D i Larger than the mixer outlet diameter D m And smaller than the outer diameter D b The critical rearward shielding section of the S-curve nozzle consists of the bend exit section and the nozzle exit section. The section profile is a rounded rectangle, determined by the section width, height, and fillet radius. The geometric center of the profile is determined by the offset.

[0041] Specific embodiments of the present invention include the following steps, the process of which is as follows: Figure 2 As shown.

[0042] Step one: Determine the design parameters for the S-bend nozzle and exhaust mixer components. The design parameters for the S-bend nozzle include, but are not limited to: nozzle inlet diameter, S-bend exit profile parameters, S-bend offset, and nozzle length. The design parameters for the exhaust mixer components include, but are not limited to: tail cone diameter, inner diameter, outer diameter, mixer outlet diameter, and exhaust mixer length. In this embodiment, the S-bend nozzle outlet profile parameters are the cross-sectional width, height, and rounding radius.

[0043] Step two: Project the exhaust mixer component backward to create a projection model of the exhaust mixer without the obstruction of the S-curve nozzle. In this embodiment, since the mixer outlet diameter D... m Greater than the inner diameter D c Nozzle inlet diameter D i Larger than the mixer outlet diameter D m And smaller than the outer diameter D b Therefore, the nozzle inlet and mixer will partially obstruct the outer bypass inlet. A projection model of the key obstruction section of the unobstructed S-curve nozzle is established by projecting the first bend exit section and the nozzle exit section backwards. The projection model is built based on the section width, height, and rounding radius.

[0044] Step 3: Calculate the rearward projected area of ​​each component of the exhaust mixer and S-bend nozzle using a graphical method, such as... Figure 3As shown, with the geometric center of the exhaust mixer projection model as the center of all images, the exhaust mixer projection model and the projection models of all S-bend nozzle key shielding sections are mapped onto the mixer projection map and the S-bend nozzle key shielding section projection map respectively, according to a fixed geometric size and pixel scale. The relative position of the key shielding section on the image can be determined based on the offset. In this embodiment, the key section projection map is the projection map of the bend exit section and the projection map of the nozzle exit section. The geometric size and pixel scale are 1 mm corresponding to 1 pixel. The mixer projection map distinguishes different components by pixel grayscale values. The internal area of ​​the key section nozzle on the key section projection map is filled with the maximum pixel value, and the pixel values ​​of the areas outside the projection model in the image are all set to 0.

[0045] Step 4, as follows Figure 3 As shown, using the mixer projection image as the base image and all key cross-section projection images as masks, the intersection of the mask and the base image is calculated sequentially by pixel AND operation according to the axial order of the key cross-sections on the S-curve nozzle, and the base image is updated in real time according to the intersection. In this embodiment, the mixer projection image and the mask of the first bend exit section are intersected to obtain the base image of the first bend exit, and the base image of the nozzle exit section is further intersected with the mask of the nozzle exit section to obtain the base image of the nozzle exit.

[0046] Step 5: Calculate the visible projected area of ​​each component of the exhaust mixer based on the pixel count results and scale of the base map, and distinguish the projected areas of different components according to the differences in pixel values. Similarly, calculate the nozzle exit area based on the pixel count results of the nozzle exit section projection map, and subtract the projected areas of each component to obtain the projected area of ​​the S-curve nozzle wall. In this embodiment, the rearward projected areas of the tail cone, inner inlet, mixer, outer bypass inlet, and nozzle can be distinguished by the differences in pixel grayscale values.

[0047] Step Six: Calculate the flow field parameter distribution inside the S-bend nozzle and the jet flow based on a one-dimensional flow model. Flow field parameters include, but are not limited to, combustion gas temperature, pressure, and combustion product component concentration distribution. Simultaneously, calculate the surface temperatures of the S-bend nozzle and exhaust system components based on the aerodynamic parameters at the S-bend nozzle inlet. In this embodiment, the temperature and pressure distribution inside the S-bend nozzle are calculated using a one-dimensional pipe flow method, and the combustion product component concentration is consistent with that at the inner inlet. The temperature, pressure, and combustion product component concentration distribution of the jet flow are calculated using a one-dimensional jet flow method. The surface temperatures of the tail cone and inner inlet are set as the total inner inlet temperature, the surface temperatures of the outer bypass inlet and S-bend nozzle wall are set as the total outer bypass inlet temperature, and the mixer surface temperature is set as the average of the total inner and outer bypass inlet temperatures.

[0048] Step 7: Establish a fitting function based on the relationship between the S-bend nozzle design parameters and the axial length and volume of the visible gas region. Calculate the axial length and volume of the visible gas region of the S-bend nozzle under the current design parameters based on the fitting function. For example... Figure 4As shown, the length and volume of the visible region of the gas combustion gas differ for S-bend nozzles with different offsets, which affects the gas combustion gas spectral transmittance and radiation intensity. The length of the visible region is the length of the line segment where the nozzle exit centerline intersects the nozzle wall. In this embodiment, fitting functions for the axial length and volume of the visible region of the S-bend nozzle design parameters are established using the Boltzmann formula and the Rogerstic formula, respectively, as follows:

[0049]

[0050]

[0051] In the formula, L v V is the axial length of the visible gas region. v L2: Length of the first bend, L3: Length of the second bend, L4: Length of the equal section, ΔY2: Longitudinal offset of the second bend, A e This represents the nozzle exit area.

[0052] Step 8: Based on the flow field parameter distribution obtained in Step 6 and the axial length of the visible gas region obtained in Step 7, calculate the spectral transmittance and spectral radiance of the gas along the nozzle outlet centerline within the visible gas region. In this embodiment, a narrow band model and the CG band approximation method are used to calculate the spectral transmittance and spectral radiance of the gas. The projected area of ​​the gas is corrected according to the visible region volume obtained in Step 7, and the spectral radiance of the gas is calculated.

[0053] Step 9: Calculate the infrared spectral radiation intensity of the wall surface based on the component projected area obtained in Step 5, the component surface temperature obtained in Step 6, and the gas spectral transmittance obtained in Step 8.

[0054] Step 10: Add the gas and wall spectral radiation intensities obtained in Step 8 and Step 9 to calculate the total infrared spectral radiation intensity of the S-bend nozzle, and integrate the spectral radiation brightness to obtain the total infrared radiation intensity.

[0055] To verify the accuracy of the calculated rearward infrared radiation intensity of the S-bend nozzle of this invention, simulation verification was performed. The comparison algorithm, based on nozzle flow field parameter data obtained through computational fluid dynamics, used the traditional discrete transfer method for infrared radiation intensity calculation. The effects of selecting different two-bend offset S-bend nozzles and different inlet total temperatures on the calculation accuracy were verified. The results are shown in Tables 1 and 2, with the maximum error being 12.52 W / sr.

[0056] Table 1 Comparison of calculated results of back-facing infrared radiation intensity for S-curve nozzles with different two-bend offsets.

[0057]

[0058] Table 2 Comparison of calculated rearward infrared radiation intensity for S-bend nozzles with different inlet total temperatures.

[0059]

[0060] The above is merely a preferred embodiment of the present invention for the rapid calculation of the rearward infrared radiation intensity of the double-bend S-curve nozzle and exhaust mixer model in the embodiments. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for rapidly calculating the infrared radiation intensity of an S-curve nozzle directly behind it, characterized in that... The specific steps are as follows: Step 1: Determine the design parameters for the S-curve nozzle and exhaust mixer components; Step 2: Project the exhaust mixer component backward to establish an exhaust mixer projection model without S-curve nozzle obstruction; project the key obstruction section of the S-curve nozzle backward to establish an S-curve nozzle key obstruction section projection model without obstruction, with the number of models matching the number of key obstruction sections. Step 3: Calculate the projected area of ​​each component after the S-curve nozzle is blocked using the image method; Step 4: Calculate the flow field parameter distribution and component surface temperature of the S-bend nozzle; Step 5: Calculate the axial length and volume of the visible area of ​​the S-bend nozzle; Step 6: Based on the flow field parameter distribution obtained in Step 4 and the axial length of the visible gas region obtained in Step 5, calculate the spectral transmittance and spectral radiance of the gas on the nozzle outlet centerline within the visible gas region; correct the projected area of ​​the gas according to the volume of the visible region obtained in Step 5, and calculate the spectral radiance of the gas. Step 7: Calculate the infrared spectral radiation intensity of the wall surface based on the component projected area obtained in Step 3, the component surface temperature obtained in Step 4, and the gas spectral transmittance obtained in Step 6; Step 8: Add the gas and wall spectral radiation intensities obtained in Step 6 and Step 7 to calculate the total infrared spectral radiation intensity of the S-bend nozzle, and integrate the spectral radiation brightness to obtain the total infrared radiation intensity.

2. The method for rapid calculation of the rearward infrared radiation intensity of an S-curve nozzle according to claim 1, characterized in that: The design parameters of the S-bend nozzle include the nozzle inlet diameter, the S-bend section outlet profile parameters, the S-bend section offset, and the nozzle length; the design parameters of the exhaust mixer component include the tail cone diameter, the inner diameter, the outer diameter, the mixer outlet diameter, and the exhaust mixer length.

3. The method for rapid calculation of the rearward infrared radiation intensity of an S-curve nozzle according to claim 1, characterized in that: The key shielding sections of the S-bend nozzle include the first bend exit section, the second bend exit section, and the nozzle exit section.

4. The method for rapid calculation of the rearward infrared radiation intensity of an S-curve nozzle according to any one of claims 1-3, characterized in that: The calculation method in step 3 is as follows: Step 3.1: Using the geometric center of the exhaust mixer projection model as the center of all images, map the unobstructed exhaust mixer projection model and the S-bend nozzle key obstruction section projection model onto the exhaust mixer projection map and the S-bend nozzle key obstruction section projection map respectively, according to fixed geometric dimensions and pixel scale. Determine the relative position of the key obstruction section on the image based on the offset. Step 3.2: Using the exhaust mixer projection image as the base image and all key shielding section projection images as masks, calculate the intersection of the mask and the base image by pixel AND operation according to the axial order of the key shielding sections on the S-curve nozzle, and update the base image in real time according to the intersection. Step 3.3: Calculate the visible area projection of each component of the exhaust mixer based on the pixel count results and scale of the base map, and distinguish the projection area of ​​different components according to the difference in pixel values; similarly, calculate the nozzle exit area based on the pixel count results of the nozzle exit section projection map, and subtract the projection area of ​​each component to obtain the projection area of ​​the S-curve nozzle wall.

5. The method for rapid calculation of the rearward infrared radiation intensity of an S-curve nozzle according to claim 4, characterized in that: In step 3.1, the mixer projection map distinguishes different components by pixel values. The internal area of ​​the nozzle in the key occlusion section of the key occlusion section projection map is filled with the maximum pixel value, and the pixel values ​​in the area outside the projection model in the image are all set to 0.

6. The method for rapid calculation of the rearward infrared radiation intensity of an S-curve nozzle according to claim 4, characterized in that: In step 4, the flow field parameter distribution inside the S-bend nozzle and the jet is calculated based on a one-dimensional flow model. The flow field parameters include the gas temperature, pressure, and concentration distribution of combustion product components. At the same time, the surface temperature of the S-bend nozzle and each component of the exhaust system is calculated based on the aerodynamic parameters at the inlet of the S-bend nozzle.

7. The method for rapid calculation of the rearward infrared radiation intensity of an S-curve nozzle according to claim 4, characterized in that: In step 5, a fitting function is established based on the relationship between the design parameters of the S-bend nozzle and the axial length and volume of the visible gas region. Based on the fitting function, the axial length and volume of the visible gas region of the S-bend nozzle under the current design parameters are calculated respectively.

8. The method for rapid calculation of the rearward infrared radiation intensity of an S-curve nozzle according to claim 4, characterized in that: In step 5, fitting functions for the axial length and volume S-bend nozzle design parameters of the visible gas region were established using the Boltzmann formula and the Rogerstic formula, respectively, as follows: In the formula, L v V is the axial length of the visible gas region. v L2: Length of the first bend, L3: Length of the second bend, L4: Length of the equal section, ΔY2: Longitudinal offset of the second bend, A e This represents the nozzle exit area.

9. The method for rapid calculation of the rearward infrared radiation intensity of an S-curve nozzle according to claim 4, characterized in that: In step 6, the gas spectral transmittance and gas spectral radiance are calculated using a narrow band model and the CG band approximation method.

Images