Method for calculating inflation time of supersonic velocity disk gap parachute

Abstract

The invention discloses a method for calculating the inflation time of a supersonic velocity disk gap parachute, which comprises the following steps of: acquiring canopy geometric parameters of the parachute according to the supersonic velocity disk gap parachute of which the inflation time needs to be calculated; the canopy projection diameter of the parachute relative to the inflation time is determined; calculating according to the geometric similarity relationship to obtain the relationship between the diameter of the parachute canopy skirt, the diameter of the junction of the seam structure and the belt structure, the diameter of the junction of the disc structure and the seam structure and the projection diameter of the parachute canopy; calculating the volume of the canopy in the full time; setting flight conditions; the post-wave density of the supersonic velocity disk gap parachute is determined, and then the post-wave gas velocity is calculated through the post-wave density; calculating the speed of airflow flowing into the canopy when the parachute is full; the speed of airflow flowing into the canopy of the parachute relative to the inflation time is determined; calculating a relational expression between the volume of the canopy and the velocity of the airflow flowing into the canopy in the relative inflation time of the parachute; and integrating the relational expression by using the time parameter and the canopy volume, and solving the inflation time of the parachute.

Description

Technical Field

[0001] This invention belongs to the field of deep space exploration aerodynamics, specifically relating to a method for calculating the inflation time of a supersonic disc-seam parachute. Background Technology

[0002] With the advancement of deep space exploration missions, the demand for supersonic parachutes in areas such as planetary atmospheric entry and deep space sample return is becoming increasingly strong. The parachute inflation time has a significant impact on the aerodynamic and structural performance of the parachute. Accurate and rapid prediction of the parachute inflation time is of great importance for the design and application of supersonic parachutes.

[0003] Existing technical approaches for calculating parachute inflation time include experimental methods, simulation methods, and empirical estimation methods. Experimental methods include using scaled-down models to conduct supersonic wind tunnel tests to obtain relevant aerodynamic data, and using sounding rockets to conduct high-altitude low dynamic pressure flight tests. Numerical simulations typically utilize large-scale computing clusters to perform corresponding computational fluid dynamics (CFD) / fluid-structure interaction (FSI) calculations to obtain detailed flow and aerodynamic data. Empirical estimation involves estimating parachute aerodynamic parameters using empirical models derived from statistical summaries of past data.

[0004] However, existing methods for calculating the inflation time of supersonic parachutes have many shortcomings: testing methods, such as supersonic wind tunnel tests and high-altitude low dynamic pressure flight tests of sounding rockets, are characterized by high testing difficulty and high human and economic costs; numerical simulation calculations are time-consuming and costly, making it difficult to meet the rapid and agile development needs in the early design of supersonic parachutes; existing empirical models cannot well match the performance characteristics of the next generation of supersonic parachutes, and the predicted data have large deviations. Summary of the Invention

[0005] The purpose of this invention is to provide a method for calculating the inflation time of a supersonic disc-stitched parachute, so as to overcome the problems of high economic cost and computational time consumption, and large deviation of prediction data in the existing technology.

[0006] To achieve the above objectives, the present invention employs the following technical solution: A method for calculating the inflation time of a supersonic disc-stitched parachute includes: Determine the canopy geometry parameters of the supersonic disc-stitched parachute based on the required inflation time. Based on the nominal diameter of the parachute and the projected diameter of the parachute at the start of inflation in the parachute's geometric parameters, determine the projected diameter of the parachute for the relevant inflation time. Based on geometric similarity, and according to the parachute canopy geometric parameters such as parachute rope length, belt structure height, seam structure height, and disc structure diameter, combined with the parachute canopy projection diameter related to the parachute inflation time, the relationship between the parachute canopy skirt opening diameter, the diameter at the junction of the seam structure and belt structure, the diameter at the junction of the disc structure and seam structure, and the parachute canopy projection diameter is determined. The volume of the parachute during full-load time is determined using the nominal diameter of the parachute in the parachute's geometric parameters. Based on the flight conditions of the supersonic disc-slotted parachute to be calculated, determine the incoming Mach number, incoming velocity, incoming density, and gas specific heat ratio. Based on the incoming Mach number, incoming velocity, incoming density, and gas specific heat ratio, the back-wave density of the supersonic disc-slotted parachute is determined; then, the back-wave gas velocity is calculated using the back-wave density. Based on the disc structure diameter, top hole diameter, seam structure height, and nominal diameter of the parachute in the parachute geometry parameters, the airflow velocity into the parachute when the parachute is fully filled is determined in conjunction with the wave-after gas velocity. By using the airflow velocity flowing into the canopy at the moment the parachute is fully inflated, the velocity of the gas behind the wave, and the parachute canopy inflation time, the airflow velocity flowing into the canopy during the parachute inflation time can be determined. Define time parameters, and combine them with the diameter of the canopy opening, the diameter of the top hole, the height of the seam structure, the gas velocity behind the wave, the diameter at the junction of the seam structure and the belt structure, and the diameter at the junction of the disc structure and the seam structure to determine the relationship between the canopy volume and the airflow velocity flowing into the canopy during the parachute inflation time. By integrating the relationship using the time parameter and the canopy volume, the inflation time of the parachute can be solved.

[0007] Furthermore, based on the nominal diameter of the parachute in the parachute canopy geometry parameters... The diameter of the parachute canopy projection at the start of inflation. Determine the parachute inflation time The diameter of the umbrella canopy projection at any moment : ; in, Time is needed to fill the parachute canopy.

[0008] Furthermore, based on the parachute rope length in the parachute canopy geometry parameters... , with structural height , joint structure height , disk structure diameter Combined with the parachute's inflation time The diameter of the umbrella canopy projection at any moment Determine the diameter of the umbrella-shaped skirt opening. Diameter at the junction of the seam structure and the strip structure Diameter at the junction of the disc structure and the seam structure Diameter of parachute canopy projection Relationship: ; in , , Both are related to inflation time Related.

[0009] Furthermore, using the nominal diameter of the parachute in the parachute canopy geometry parameters... Determine the volume of the canopy during the time it is fully filled. : .

[0010] Furthermore, based on the incoming Mach number Incoming flow velocity Incoming flow density Specific heat ratio of gases Determine the wave back density of a supersonic disc-slotted parachute. Then utilize waveback density Calculate the gas velocity after the wave The calculation formula is as follows: ; .

[0011] Furthermore, based on the disc structure diameter in the umbrella canopy geometry... Top hole diameter , height of seam structure and the nominal diameter of the parachute Combined with the wave-after gas velocity Determine the airflow speed into the canopy when the parachute is fully inflated. The specific formula is as follows: .

[0012] Furthermore, the speed of the airflow flowing into the canopy at the moment the parachute is fully filled is utilized. Gas velocity after wave And the parachute canopy is filled with time Determine the parachute inflation time The speed of the airflow flowing into the canopy at all times The formula is as follows: .

[0013] Furthermore, let the time parameter Combined with the diameter of the umbrella skirt opening Top hole diameter , joint structure height Gas velocity after wave Diameter at the junction of the seam structure and the strip structure Diameter at the junction of the disc structure and the seam structure Determine the volume of the umbrella canopy Inflation time The speed of the airflow flowing into the canopy at all times Relationship: ; in , , , All with time Related; Represents the scale parameter relative to time. Differential operators. Furthermore, regarding the right side of the aforementioned relation from... to Integral, from the left side to The inflation time of the parachute can be calculated by integrating the components. ;in This refers to the volume enclosed by the canopy at the initial inflation stage. The umbrella canopy is filled with the volume of time.

[0014] A terminal device includes a processor, a memory, and a computer program stored in the memory; when the processor executes the computer program, it implements the method for calculating the inflation time of the supersonic disc-seam parachute.

[0015] A computer-readable storage medium storing a computer program; when executed by a processor, the computer program implements the method for calculating the inflation time of a supersonic disc-seam parachute.

[0016] Compared with the prior art, the present invention has the following technical features: 1. The method of this invention comprehensively considers the compression effect of the shock wave in front of the supersonic parachute on the airflow and the characteristic that the projected diameter of the parachute canopy can be approximately expressed as linearly increasing during the inflation process. It can quickly and conveniently obtain the inflation time of the supersonic disc-seam parachute through numerical calculation, thereby further providing support for the research and design of supersonic parachutes.

[0017] 2. The parameters involved in the method of the present invention are only related to the parachute's own structural parameters and flight condition parameters, which can quickly and conveniently obtain relevant data and have high calculation efficiency. Attached Figure Description

[0018] Figure 1This is a schematic diagram of the geometric structure of a supersonic disc-slotted parachute; in the diagram, ① is the radius of the parachute disc structure; ② is the parachute slot structure; ③ is the height of the parachute strap structure; and ④ is the length of the parachute lines. Figure 2 Digital image processing and edge detection process for the projected area during the parachute inflation process; Figure 3 This is the curve showing the change in the projected diameter of the parachute; Figure 4 Model of the initial moment of parachute inflation; Figure 5 The parachute drag curve was obtained through fluid-structure interaction simulation; the peak drag time is 0.23s. Figure 6 A schematic diagram illustrating the shape changes of a parachute during inflation. Detailed Implementation

[0019] This invention provides a method for calculating the inflation time of a supersonic spiral-slotted parachute, which is commonly used for spiral-slotted parachutes, thereby providing guidance for the rapid and agile development and design of supersonic spiral-slotted parachutes.

[0020] In his research on the shape of the parachute canopy during inflation, O'Hara proposed an ideal shape for the canopy, consisting of an upper hemisphere with a diameter equal to the projected diameter of the canopy and an inverted frustum (Reference: O'Hara F. Notes on the Opening Behaviour and the Opening Forces of Parachutes. Journal of the Royal Aeronautical Society. 1949;53(467):1053-1062. doi:10.1017 / S0368393100120759). The shape change trend of the slotted parachute during the initial expansion stage, obtained from the inventor's fluid-structure interaction calculations during the parachute inflation process, conforms to this assumption. For a slotted parachute that maintains an ideal shape during inflation, its hemispherical part is composed of a partial disc structure, and the frustum part is composed of the parachute slots, bands, and a partial disc structure, such as... Figure 1 As shown.

[0021] See Figure 2 The inventors, in the fluid-structure interaction calculations of the inflating and unfolding process of the disc-seam parachute, used digital image processing technology to perform edge detection on the top view of the parachute canopy, obtaining the area of ​​the connected region in the canopy's projected image, and calculating the curve of the canopy's projected diameter change during the inflation and unfolding process, such as... Figure 3 As shown.

[0022] The method of the present invention includes the following steps: Step 1: Based on the supersonic disc-stitched parachute for which the inflation time needs to be calculated, determine the parachute canopy geometry parameters: disc structure diameter... Top hole diameter , height of seam structure , with structural height Paracord length nominal diameter of parachute The diameter of the parachute canopy projection at the start of inflation. And the volume enclosed by the parachute canopy (that is, the volume of the parachute at the initial inflation moment after it is fully extended). The projection mentioned therein refers to the projection in the radial plane.

[0023] Step 2, based on the nominal diameter of the parachute in the parachute canopy geometry parameters. The diameter of the parachute canopy projection at the start of inflation. Determine the parachute inflation time The diameter of the umbrella canopy projection at any moment : ; in, Time is needed to fill the parachute canopy.

[0024] The derivation of the formula is as follows: During the inflation process, the projected diameter of a parachute canopy can be approximated as increasing linearly. (Canopy projected diameter) It can be written as: ; in, The initial diameter of the parachute canopy projection; the scaling factor in the formula. Determined by the following condition: when the parachute is fully charged. At that time, the canopy's projected diameter reaches its maximum value. ,have to: ; in, For the full-fill time, referring to Ibrahim's assumptions (reference: lbrahim-2012-the-potential-flow-field-and-the-added-mass-of-the-idealized-hemispherical-parachute) and the inventor's results on the fluid-structure interaction calculations of the slotted parachute, it is assumed that the parachute in its full-fill state is an ideal hemispherical shape. Therefore: ; in, The nominal diameter of the parachute; Substitute into From this, we can obtain the expression from step 1.

[0025] Step 3, see appendix Figure 1 Based on geometric similarity, and according to the parachute rope length in the parachute canopy's geometric parameters... , with structural height , joint structure height , disk structure diameter Combined with the parachute's inflation time The diameter of the umbrella canopy projection at any moment Determine the diameter of the umbrella-shaped skirt opening. Diameter at the junction of the seam structure and the strip structure Diameter at the junction of the disc structure and the seam structure Diameter of parachute canopy projection The relationship.

[0026] ; Due to the diameter of the umbrella canopy projection Inflation time Related, therefore, according to the relationship in the above formula, , , Both are related to inflation time Related.

[0027] Step 4, using the nominal diameter of the parachute from the parachute canopy geometry parameters. Determine the volume of the canopy during the time it is fully filled. The specific formula is as follows: ; Step 5: Determine the incoming Mach number based on the flight conditions of the supersonic disc-stitched parachute to be calculated. Incoming flow velocity Incoming flow density Specific heat ratio of gases The flight conditions are set according to actual calculation requirements, and the inflation time under different flight conditions can be quickly calculated using this method.

[0028] Step 6, based on the incoming Mach number Incoming flow velocity Incoming flow density Specific heat ratio of gases Determine the wave back density of a supersonic disc-slotted parachute. Then utilize waveback density Calculate the gas velocity after the wave The calculation formula is as follows: ; ; Step 7: During parachute inflation, airflow enters the canopy, forming a stagnant region. This stagnant region rapidly expands, with its leading edge quickly reaching the front of the canopy skirt. It is approximated that the initial velocity of the inflowing and outflowing gas during inflation is the average velocity of the compressed gas. After the canopy is fully inflated, ignoring any breathing phenomena, and assuming the canopy volume remains constant, the inflow and outflow of gas reach a dynamic equilibrium. Based on this, the gas flow velocity into the canopy after it is fully inflated can be obtained.

[0029] Based on the diameter of disk 1 structure in the umbrella canopy's geometric parameters Top hole diameter , joint structure height and the nominal diameter of the parachute Combined with the wave-after gas velocity Determine the airflow speed into the canopy when the parachute is fully inflated. The specific formula is as follows: ; Step 8: Utilize the airflow speed flowing into the canopy when the parachute is fully inflated. Gas velocity after wave And the parachute canopy is filled with time Determine the parachute inflation time The speed of the airflow flowing into the canopy at all times The formula is as follows: ; Step 9: During the inflation process of the parachute with the seam, the incoming air enters through the opening of the parachute skirt, while the airflow flows out from the top hole and the seam of the canopy. The difference between the inflowing and outflowing air causes the parachute to inflate.

[0030] Let time parameter Combined with the diameter of the umbrella skirt opening Top hole diameter , height of seam structure Gas velocity after wave Diameter at the junction of the seam structure and the strip structure Diameter at the junction of the disc structure and the seam structure Determine the volume of the umbrella canopy Inflation time The speed of the airflow flowing into the canopy at all times Relationship: ; in , , , All with time Related; Represents the scale parameter relative to time. The differential operator. The three terms on the right side of the equation represent the mass flowing in through the opening of the umbrella skirt, the mass flowing out through the top hole of the umbrella, and the mass flowing out through the seams of the umbrella.

[0031] Step 10, approximately assuming that the gas flow velocity into the parachute canopy changes linearly during parachute inflation; the right side of the aforementioned relationship is derived from... to Integral, from the left side to The inflation time of the parachute can be calculated by integrating the components. .

[0032] Example: Taking a certain type of supersonic disc-stitched parachute as an example, the supersonic flight conditions of this parachute are: flight speed of Mach 1.88 and atmospheric density of 0.00601 kg / m³. 3 The atmospheric pressure is 414 Pa.

[0033] Based on the supersonic disc-stitched parachute for which the inflation time needs to be calculated, determine the parachute canopy geometry parameters: (Diameter of the disc structure is missing). Top hole diameter Seam structure height , with structural height Paracord length Nominal diameter of parachute The diameter of the parachute canopy projection at the start of inflation. The volume enclosed by the umbrella canopy .

[0034] In this embodiment, the calculated volume of the canopy during the full filling time is... The flight condition to be calculated is the incoming Mach number. ,speed ,density Specific heat ratio of gases Supersonic parachute post-wave parameters: post-wave gas velocity and post-wave density The speed of the airflow into the parachute canopy when it is fully inflated. Finally, the model of the initial parachute inflation moment was obtained by solving the relational integral. Figure 4Let the initial volume of the canopy be taken as the volume of the canopy, and the ideal hemispherical shape formed after inflation be taken as the maximum volume. Let the parameters of the compressed gas inside the canopy be the parameters of the gas compressed by the shock wave flowing freely past the canopy skirt opening. Substituting the relevant parachute data, the canopy inflation time of the supersonic disc-stitched parachute can be obtained as follows: .

[0035] The umbrella canopy filling time obtained using the calculation method proposed in this invention The maximum time for the parachute canopy projected area, calculated using fluid-structure interaction simulation, was 0.216 s (see [reference]). Figure 3 The error was 16.20%, and the time between the moment of maximum canopy opening force and the moment of maximum opening force was 0.230s (see...). Figure 5 The error is 6.09%. Therefore, the calculation method proposed in this invention has high accuracy. The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for calculating the inflation time of a supersonic disc-stitched parachute, characterized in that, include: Determine the canopy geometry parameters of the supersonic disc-stitched parachute based on the required inflation time. Based on the nominal diameter of the parachute and the projected diameter of the parachute at the start of inflation in the parachute's geometric parameters, determine the projected diameter of the parachute for the relevant inflation time. Based on geometric similarity, and according to the parachute canopy geometric parameters such as parachute rope length, belt structure height, seam structure height, and disc structure diameter, combined with the parachute canopy projection diameter related to the parachute inflation time, the relationship between the parachute canopy skirt opening diameter, the diameter at the junction of the seam structure and belt structure, the diameter at the junction of the disc structure and seam structure, and the parachute canopy projection diameter is determined. The volume of the parachute during full-load time is determined using the nominal diameter of the parachute in the parachute's geometric parameters. Based on the flight conditions of the supersonic disc-slotted parachute to be calculated, determine the incoming Mach number, incoming velocity, incoming density, and gas specific heat ratio. Based on the incoming Mach number, incoming velocity, incoming density, and gas specific heat ratio, the back-wave density of the supersonic disc-slotted parachute is determined; then, the back-wave gas velocity is calculated using the back-wave density. Based on the disc structure diameter, top hole diameter, seam structure height, and nominal diameter of the parachute in the parachute geometry parameters, the airflow velocity into the parachute when the parachute is fully filled is determined in conjunction with the wave-after gas velocity. By using the airflow velocity flowing into the canopy at the moment the parachute is fully inflated, the velocity of the gas behind the wave, and the parachute canopy inflation time, the airflow velocity flowing into the canopy during the parachute inflation time can be determined. Define time parameters, and combine them with the diameter of the canopy opening, the diameter of the top hole, the height of the seam structure, the gas velocity behind the wave, the diameter at the junction of the seam structure and the belt structure, and the diameter at the junction of the disc structure and the seam structure to determine the relationship between the canopy volume and the airflow velocity flowing into the canopy during the parachute inflation time. By integrating the relationship using the time parameter and the canopy volume, the inflation time of the parachute can be solved.

2. The method for calculating the inflation time of a supersonic disc-stitched parachute according to claim 1, characterized in that, Based on the nominal diameter of the parachute in the canopy geometry parameters The diameter of the parachute canopy projection at the start of inflation. Determine the parachute inflation time The diameter of the umbrella canopy projection at any moment : ； in, Time is needed to fill the parachute canopy.

3. The method for calculating the inflation time of a supersonic disc-stitched parachute according to claim 1, characterized in that, Based on the parachute rope length in the umbrella canopy's geometric parameters , with structural height , joint structure height , disk structure diameter Combined with the parachute's inflation time The diameter of the umbrella canopy projection at any moment Determine the diameter of the umbrella-shaped skirt opening. Diameter at the junction of the seam structure and the strip structure Diameter at the junction of the disc structure and the seam structure Diameter of parachute canopy projection Relationship: ； in , , Both are related to inflation time Related.

4. The method for calculating the inflation time of a supersonic disc-stitched parachute according to claim 1, characterized in that, Based on the incoming Mach number Incoming flow velocity Incoming flow density Specific heat ratio of gases Determine the wave back density of a supersonic disc-slotted parachute. Then utilize waveback density Calculate the gas velocity after the wave The calculation formula is as follows: ； 。 5. The method for calculating the inflation time of a supersonic disc-stitched parachute according to claim 1, characterized in that, Based on the disc structure diameter in the umbrella canopy's geometric parameters Top hole diameter , joint structure height and the nominal diameter of the parachute Combined with the wave-after gas velocity Determine the airflow speed into the canopy when the parachute is fully inflated. The specific formula is as follows: 。 6. The method for calculating the inflation time of a supersonic disc-stitched parachute according to claim 1, characterized in that, Utilizing the airflow speed flowing into the canopy when the parachute is fully inflated Gas velocity after wave And the parachute canopy is filled with time Determine the parachute inflation time The speed of the airflow flowing into the canopy at all times The formula is as follows: 。 7. The method for calculating the inflation time of a supersonic disc-stitched parachute according to claim 1, characterized in that, Let time parameter Combined with the diameter of the umbrella skirt opening Top hole diameter , joint structure height Gas velocity after wave Diameter at the junction of the seam structure and the strip structure Diameter at the junction of the disc structure and the seam structure Determine the volume of the umbrella canopy Inflation time The speed of the airflow flowing into the canopy at all times Relationship: in , , , All with time Related; Represents the scale parameter relative to time. Differential operators.

8. The method for calculating the inflation time of a supersonic disc-stitched parachute according to claim 1, characterized in that, From the right side of the relation to Integral, from the left side to The inflation time of the parachute can be calculated by integrating the components. ;in This refers to the volume enclosed by the canopy at the initial inflation stage. The umbrella canopy is filled with the volume of time.

9. A terminal device, comprising a processor, a memory, and a computer program stored in the memory; characterized in that, When the processor executes the computer program, it implements the method for calculating the inflation time of the supersonic disc-seam parachute as described in any one of claims 1-8.

10. A computer-readable storage medium storing a computer program; characterized in that, When the computer program is executed by the processor, it implements the method for calculating the inflation time of the supersonic disc-seam parachute as described in any one of claims 1-8.

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