Calculation method suitable for parafoil opening inflation process

Abstract

The invention discloses a calculation method suitable for a parafoil opening inflation process. In combination with the influence of various structural parameters of the parafoil on the parafoil inflation process, the parafoil opening process is divided into a middle air chamber inflation stage, a two-end air chamber inflation stage and a closing-up cloth gliding canopy comprehensive inflation stage; establishing a mathematical model according to the characteristics of the three stages, substituting the structural parameters of the parafoil into the mathematical model, and then calculating the physical quantities of the parafoil system speed, displacement, additional mass, acceleration and parafoil opening overload in the three stages, so as to realize the analysis of the parafoil opening process of the parafoil. According to the method, the defect that the air inflation process of the parafoil is regarded as rough calculation of a round parafoil at present is overcome, the calculation precision of all physical quantities in the parafoil opening process is greatly improved, and the structural design of the parafoil is effectively supported.

Description

Technical Field

[0001] The invention belongs to the technical field of airborne airdrop, and in particular, is a calculation method suitable for a paraglider opening and inflation process. Background Art

[0002] The parachute opening process can be divided into three stages: straightening, inflation and steady descent. Among them, the inflation process is the most complicated. For round parachutes, the inflation process is usually after the canopy and the ropes are straightened, the airflow enters from the bottom of the canopy, and the canopy slowly changes from a line to a bulb shape until it is fully filled; for wing parachutes, after the ropes are straightened, the first airflow will enter the middle air chamber of the canopy, and then expand to the left and right wing tips until it is fully filled.

[0003] At present, there are many studies on the opening process of round parachutes at home and abroad, and its inflation mechanism and calculation method are also relatively mature. After the parachute rope is straightened, the opening process of the round parachute can be calculated according to the inflation time method or the inflation distance method. The change law of parameters such as the canopy resistance characteristics, descent speed, and distance can be calculated.

[0004] Compared with round parachutes, there are few studies on the opening process of wing parachutes at home and abroad. For the opening and inflation process of wing parachutes, a rough calculation is made using the reverse pull method similar to that of round parachutes. That is, the wing parachutes are regarded as round parachutes with the same area, and the calculation is made by referring to the inflation distance method of round parachutes. The calculation process is as follows:

[0005]

[0006]

[0007]

[0008]

[0009]

[0010]

[0011]

[0012]

[0013]

[0014] Where:

[0015] θ——trajectory angle, rad;

[0016] S——Displacement of the parachute system, m.

[0017] g——acceleration due to gravity, m 2 / s;

[0018] v——velocity of the cargo-parachute system, m / s;

[0019] x d ——horizontal displacement of the cargo-parachute system, m;

[0020] y d ——vertical displacement of the cargo-parachute system, m;

[0021] t——time, s;

[0022] m w ——mass of recycled material, kg;

[0023] m s ——canopy mass, kg;

[0024] m f ---Additional mass, kg;

[0025] ρ——air density, kg / m 3 ;

[0026] (CA) w ——Recyclable material resistance characteristics;

[0027] (CA) – parachute system drag characteristics;

[0028] k f ——Added mass system, usually taken as 0.41.

[0029] S1——Displacement of the parachute system during initial inflation, m;

[0030] (CA)1 – Drag characteristics of the parachute system at the end of initial inflation;

[0031] S m ——Full displacement of the object-parachute system, m.

[0032] In fact, the inflation process and mechanism of a wing parachute are different from those of a round parachute. After the parachute rope is straightened, the first airflow will enter the middle air chamber of the canopy, which is curled up into a ball. After the middle air chamber is inflated, it will expand toward the left and right wingtips, causing the wingtip air chambers to inflate. The entire canopy inflation process is similar to an "accordion", unfolding along the wingspan. Since the wing parachute opening process is highly nonlinear and random, current research on the wing parachute opening process still mainly relies on airdrop tests, and the design parameters such as the installation angle and parachute rope length are optimized based on the airdrop test results. Undoubtedly, airdrop tests are costly, long, and require a lot of manpower and financial resources, and require repeated iterative verification, which to a certain extent limits the development of wing parachute technology.

[0033] The existing theoretical method is to treat the parafoil as a round parafoil with the same area and perform numerical calculations according to the round parafoil inflation theory. In fact, the inflation process of the parafoil is significantly different from that of the round parafoil. The calculation method based on the round parafoil inflation theory does not consider the influence of the parafoil airfoil, the opening area, the size of the closing cloth, the installation angle and other structural parameters on the inflation process. The calculation results are quite different from the actual airdrop measured data, and cannot provide an effective reference for the parafoil structure design.

[0034] The present invention solves the technical bottleneck problem that in the design of parafoil structure, the inflation process lacks theoretical calculation method support and completely relies on the results of airdrop tests. Summary of the invention

[0035] The object of the present invention is to provide a parafoil opening process calculation method for improving the accuracy of theoretical calculation of the parafoil inflation process.

[0036] The technical solution to achieve the purpose of the present invention is: a calculation method suitable for the parafoil opening and inflation process, combining the influence of various structural parameters of the parafoil on the parafoil inflation process, dividing the parafoil opening process into three stages: the middle air chamber inflation stage, the two end air chamber inflation stage and the closing cloth sliding canopy full inflation stage; establishing a mathematical model according to the characteristics of the three stages, substituting the structural parameters of the parafoil into the model, and calculating the physical quantities of the parafoil system speed, displacement, additional mass, acceleration, and opening overload in the three stages, so as to realize the analysis of the parafoil opening process.

[0037] Furthermore, the method specifically includes the following steps:

[0038] Step 1, obtaining various calculation parameters of the parafoil;

[0039] Step 2: Divide the middle 3-4 air chambers whose width is equal to the length of the closing cloth into intermediate air chambers; the middle air chambers of the canopy begin to inflate and slowly expand toward the left and right wing tips, and the closing cloth clings to the lower wing surface of the middle air chambers to inhibit the inflation of the wing tip air chambers, until the middle 3-4 air chambers are completely filled, indicating that the inflation stage of the intermediate air chambers is over; establish an inflation model for the middle air chambers of the canopy, substitute the calculation parameters into the model to obtain the physical quantities of the system such as speed, trajectory angle, horizontal displacement, vertical displacement, and additional mass during the inflation stage of the middle air chambers; the values ​​of the physical quantities at the end of this stage are used as the initial conditions for the next stage;

[0040] Step three, the stage when the wing tip air chamber starts to inflate during the parachute opening stage, and the force of the canopy expanding outward increases until the sum of the downward pushing force of the closing cloth by the tension component of the parachute rope and the gravity of the closing cloth is greater than the aerodynamic resistance of the closing cloth is divided into the second stage, the two-end air chamber inflation stage; an air chamber inflation model for both ends is established, and the calculation parameters are substituted into the model to obtain the physical quantities of the system such as speed, trajectory angle, horizontal displacement, vertical displacement, and additional mass during the two-end air chamber inflation stage; the values ​​of the physical quantities at the end of this stage are used as the initial conditions for the next stage;

[0041] Step four, when the sum of the outward expansion force of the parachute rope and the gravity of the closing cloth is greater than the aerodynamic resistance generated by the closing cloth, the balance is destroyed, the closing cloth slides down, and the parachute opening process enters the third stage; the characteristic of this stage is that the closing cloth begins to slide down from the lower wing surface of the canopy to the bottom of the parachute rope; according to the test data of the wing parachute airdrop test, the wing parachute in this stage is regarded as a round parachute, and the canopy resistance characteristics and speed of the inflation process are used as the differential relationship to establish a model of the canopy full inflation stage when the closing cloth slides down; substituting the canopy resistance characteristics and system speed at the end of the second stage, the canopy resistance characteristics and speed at any time in this stage can be obtained.

[0042] Furthermore, the step 1 obtains the parachute opening speed, opening height, canopy area, total parachuting mass, human body resistance characteristics, canopy span, canopy average chord length, airfoil thickness, air inlet height, closing cloth size, closing cloth mass, closing cloth ring and parachute rope friction coefficient, and parachute rope characteristic length data.

[0043] Furthermore, the inflation model of the canopy middle air chamber established in step 2 is:

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050] Where:

[0051] v - system speed, m / s;

[0052] t——time, s;

[0053] m s ——parachute system mass, kg;

[0054] m w ——body mass, kg;

[0055] m f ——Additional mass, kg;

[0056] g——acceleration due to gravity, m 2 / s;

[0057] θ——trajectory angle, rad;

[0058] ρ——air density, kg / m 3 ;

[0059] C(t)——canopy real-time drag coefficient;

[0060] A——canopy area, m 2 ;

[0061] CA w ——Human body resistance characteristics, take 0.5;

[0062] x——horizontal displacement of the system, m;

[0063] y——vertical displacement of the system, m;

[0064] D0——nominal diameter of canopy, m

[0065] t i ——The canopy filling time estimated by treating the parafoil similarly to a round parachute with a diameter of D0, s;

[0066] V cell (t)——the volume of the middle air chamber, m 3 ;

[0067] A in ——Inlet area of ​​the middle air chamber, m 2 ;

[0068] At the end of the first stage, the canopy volume is:

[0069] V cell (t final )=0.5L slider-span L thick (L chord +L slider-chord )

[0070] The intake area is:

[0071] A in =L slider-span L thick f in

[0072] The resistance characteristics at this stage are:

[0073]

[0074] Where:

[0075] V cell (t final )——canopy volume at the end of the first stage, m 3 ;

[0076] L slider-span ——Length of closing fabric, m;

[0077] L slider-chord ——Width of closing fabric, m;

[0078] L thick ——airfoil thickness, m;

[0079] L chord ——airfoil chord length, m;

[0080] f in - air intake efficiency;

[0081] CA——system resistance characteristic, m;

[0082] (CA) pilot ——Drag characteristics of the guide parachute, m.

[0083] Furthermore, the inflation model of the air chambers at both ends established in step 3 is:

[0084] Outer chamber inflation volume:

[0085] V outboard-in =∫A outboard (t)u in dt

[0086] V outboard-in ——Inflated volume of outer air chamber, m 3 ;

[0087] A outbord (t)——intake area of ​​outer air chamber, m 2 ;

[0088] u in ——intake air velocity, m / s;

[0089]

[0090] C n (t) is the drag coefficient, which is a function of the inclination angle Ω(t) when the sidewall is regarded as an inclined flat plate in the airflow. For most airfoils, C n (t) is quickly calculated according to the following formula:

[0091]

[0092] The aerodynamic resistance of the closing fabric is:

[0093]

[0094] (CA) slider =1.12L slider-span L slider-chord

[0095] Where:

[0096] F slider-drag —— aerodynamic resistance of the closing fabric, N;

[0097] (CA) slider ——resistance characteristics of the closing fabric, m;

[0098] The drag characteristics of an umbrella are:

[0099] CA(t)=1.12L span (t)L chord (t)

[0100] L span (t) is the real-time expansion length of the canopy, L chord (t) is the real-time chord length of the canopy:

[0101] L span (t) = L slider-span +2X(t)

[0102]

[0103] The downward push of the rope tension component on the closing cloth is:

[0104]

[0105] μ is the resistance coefficient of the slip ring

[0106] The gravity of the closing fabric is G slider =9.81m slider

[0107] m slider ——Mass of the closing fabric, kg;

[0108] When F line-drive +G slider >F slider-drag When the balance is broken, the closing cloth slides down, and the parachute opening process enters the third stage;

[0109] F line-drive —— downward component of the parachute line tension, N;

[0110] F slider-drag ——Resistance of the closing fabric, N.

[0111] Furthermore, the model of the full inflation stage of the canopy under the closing cloth established in step 4 is:

[0112]

[0113] K imp is the canopy expansion coefficient, which can be taken as a constant based on experience;

[0114] When (CA)(t) increases to the system resistance characteristic, the entire parachute opening process is completed.

[0115] Compared with the prior art, the present invention has the following significant advantages: according to the parafoil working procedure, the parafoil opening process is divided into three stages, Newton's motion equation based on the change of canopy resistance area and load during the parafoil inflation process is established, and the influence of structural parameters such as the parafoil airfoil shape, the opening area, the closing cloth size, the installation angle and the like on the inflation process is considered to improve the calculation accuracy of the parafoil inflation process, solves the problem that the parafoil inflation process lacks theoretical calculation or the theoretical calculation accuracy is insufficient, and mainly relies on the airdrop test results, and provides a theoretical basis for the design optimization of the parafoil. BRIEF DESCRIPTION OF THE DRAWINGS

[0116] Figure 1 It is the relationship between the speed and time of the parafoil opening process.

[0117] Figure 2 This is the relationship between vertical displacement and time during the parafoil opening process.

[0118] Figure 3 This is the relationship between overload and time during the parachute opening process.

[0119] Figure 4 Schematic diagram of the inclination angle Ω(t). DETAILED DESCRIPTION

[0120] The present invention proposes a calculation method suitable for theoretical calculation of the parafoil inflation process, which considers the influence of structural parameters such as airfoil, air inlet area, closing cloth size, installation angle, etc. on the parafoil inflation process, divides the parafoil opening process into three stages: the middle air chamber inflation stage, the two end air chamber inflation stage, and the closing cloth lower canopy full inflation stage, and adopts different mathematical description equations for the physical processes of the three stages, and obtains the physical quantities such as speed, overload, and descent height of the parafoil opening process after substituting the structural parameters of the parafoil and the opening height and speed, etc. of the parafoil. It overcomes the deficiency of roughly calculating the parafoil inflation process as a round parachute, greatly improves the calculation accuracy of various physical quantities in the parafoil opening process, and effectively supports the product structure design.

[0121] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0122] Step 1: Obtain various calculation parameters

[0123] Determine the parachute opening speed, parachute opening height, canopy area, total parachuting mass, human body resistance characteristics, canopy span, canopy average chord length, airfoil thickness, air inlet height, closing cloth size, closing cloth mass, closing cloth ring and parachute rope friction coefficient, and parachute rope characteristic length data.

[0124] Step 2: Establish an inflation model for the middle air chamber of the canopy. The middle air chamber refers to the 3 to 4 air chambers in the middle with a width approximately equal to the length of the closing cloth. The main feature of this stage is that the middle of the canopy is fully inflated, and the closing cloth is close to the lower wing surface of the middle air chamber to inhibit the inflation of the wingtip air chamber. Substitute the calculation parameters into the model to obtain the physical quantities such as the speed, trajectory angle, horizontal displacement, vertical displacement, and additional mass of the system during the inflation stage of the middle air chamber. The values ​​of each physical quantity at the end of this stage are used as the initial conditions for the next stage.

[0125] The kinetic equation is as follows:

[0126]

[0127]

[0128]

[0129]

[0130]

[0131]

[0132] Where:

[0133] v——system speed, m / s;

[0134] t——time, s;

[0135] m s ——parachute system mass, kg;

[0136] m w ——body mass, kg;

[0137] m f ——Additional mass, kg;

[0138] g——acceleration due to gravity, m 2 / s;

[0139] θ——trajectory angle, rad;

[0140] ρ——air density, kg / m 3 ;

[0141] C(t)——canopy real-time drag coefficient;

[0142] A——canopy area, m 2 ;

[0143] CA w ——Human body resistance characteristics, take 0.5;

[0144] x——horizontal displacement of the system, m;

[0145] y——vertical displacement of the system, m;

[0146] D0——nominal diameter of canopy, m

[0147] t i ——The canopy filling time estimated by treating the parafoil similarly to a round parachute with a diameter of D0, s;

[0148] V cell (t)——the volume of the middle air chamber, m 3 ;

[0149] A in ——Inlet area of ​​the middle air chamber, m 2 .

[0150] At the end of the first stage, the canopy volume is:

[0151] V cell (t final )=0.5L slider-span L thick (L chord +L slider-chord )

[0152] The intake area is:

[0153] A in =L slider-span L thick f in

[0154] The resistance characteristics at this stage are:

[0155]

[0156] Where:

[0157] V cell (t final )——canopy volume at the end of the first stage, m 3 ;

[0158] L slider-span ——Length of closing fabric, m;

[0159] L slider-chord ——Width of closing fabric, m;

[0160] L thick ——airfoil thickness, m;

[0161] L chord ——airfoil chord length, m;

[0162] f in ——Intake efficiency, which can be a constant based on experience;

[0163] CA——system resistance characteristic, m;

[0164] (CA) pilot ——drag characteristics of the guide parachute, m;

[0165] Step 3: Establish an inflation model for the air chambers at both ends, and substitute the calculation parameters into the model to obtain the physical quantities such as the speed, trajectory angle, horizontal displacement, vertical displacement, and additional mass of the system during the inflation phase of the air chambers at both ends. This phase refers to the beginning of inflation of the wingtip air chambers, and the increase in the force of the canopy expanding outward. When the sum of the downward force of the tension component of the parachute rope on the closing cloth and the gravity of the closing cloth is greater than the aerodynamic resistance of the closing cloth, it marks the end of this phase. The values ​​of the physical quantities at the end of this phase serve as the initial conditions for the next phase.

[0166] Outer chamber inflation volume:

[0167] V outboard-in =∫A outboard (t)u in dt

[0168] V outboard-in ——Inflated volume of outer air chamber, m 3 ;

[0169] A outbord (t)——intake area of ​​outer air chamber, m 2 ;

[0170] u in ——Intake air velocity, m / s.

[0171]

[0172] C n (t) is the drag coefficient, which is a function of the inclination angle Ω(t) when the sidewall is regarded as an inclined flat plate in the airflow. Figure 4 For most airfoils, C n (t) can be quickly calculated using the following formula:

[0173]

[0174] The aerodynamic resistance of the closing fabric is:

[0175]

[0176] (CA) slider =1.12L slider-span L slider-chord

[0177] Where:

[0178] F slider-dmg—— aerodynamic resistance of the closing fabric, N;

[0179] (CA) slider ——resistance characteristics of the closing fabric, m;

[0180] The drag characteristics of an umbrella are:

[0181] CA(t)=1.12L span (t)L chord (t)

[0182] L span (t) is the real-time expansion length of the canopy, L chord (t) is the real-time chord length of the canopy:

[0183] L span (t) = L slider-span +2X(t)

[0184]

[0185]

[0186] The downward push of the rope tension component on the closing cloth is:

[0187]

[0188] μ is the resistance coefficient of the slip ring

[0189] The gravity of the closing fabric is G slider =9.81m slider

[0190] m slider ——Mass of the closing fabric, kg;

[0191] When F line-drive +G slider >F slideer-drag When the parachute is opened, the balance is destroyed, the closing cloth slides down, and the parachute opening process enters the third stage.

[0192] F line-drive —— downward component of the parachute line tension, N;

[0193] F slider-drag ——Resistance of the closing fabric, N.

[0194] Step 4: Establish a model for the full inflation stage of the canopy after the closing cloth slides down

[0195] According to the analysis of a large number of dynamic load curves measured in the airdrop test, the change law of the parafoil drag characteristics in the third stage is summarized as follows:

[0196]

[0197] Kimp is the canopy expansion coefficient, which can be taken as a constant based on experience.

[0198] When (CA)(t) increases to the system resistance characteristic, the entire parachute opening process is completed.

[0199] According to the above calculation steps, a typical calculation curve is obtained as follows: Figure 1-3 .

[0200] Figure 1 The curve of the relationship between the speed and time of the parafoil from the first stage to the third stage of full filling is calculated by substituting the parafoil structural parameters into the model established according to the present invention. Figure 1 It can be seen that the umbrella is fully filled in about 2.1 seconds.

[0201] Figure 2 The following is a curve of the relationship between the descent height and time of the parafoil from the first stage to the third stage of full filling, calculated by substituting the parafoil structural parameters into the model established according to the present invention. Figure 2 It can be seen that the parachute descends about 105m during the opening process.

[0202] Figure 3 The relationship curve between the parachute overload and time during the parachute opening process from the first stage to the third stage of full filling is calculated by substituting the parachute structural parameters into the model established according to the present invention. Figure 3 It can be seen that the maximum overload of the parachute during the opening process is about 6.25g.

Claims

1. A calculation method applicable to the paraglider opening and inflation process, characterized in that: Combined with the influence of various structural parameters of the parafoil on the inflation process of the parafoil, the parafoil opening process is divided into three stages: the inflation stage of the middle air chamber, the inflation stage of the air chambers at both ends, and the full inflation stage of the lower canopy. According to the characteristics of the three stages, a mathematical model is established, and the structural parameters of the parafoil are substituted into the model to calculate the physical quantities of the parafoil system velocity, displacement, additional mass, acceleration, and opening overload in the three stages, so as to realize the analysis of the parafoil opening process.

2. The calculation method applicable to the parafoil opening and inflation process according to claim 1, characterized in that: The specific steps include: Step 1, obtaining various calculation parameters of the parafoil; Step 2: Divide the middle 3-4 air chambers whose width is equal to the length of the closing cloth into intermediate air chambers; the middle air chambers of the canopy begin to inflate and slowly expand toward the left and right wing tips, and the closing cloth clings to the lower wing surface of the middle air chambers to inhibit the inflation of the wing tip air chambers, until the middle 3-4 air chambers are completely filled, indicating that the inflation stage of the intermediate air chambers is over; establish an inflation model for the middle air chambers of the canopy, substitute the calculation parameters into the model to obtain the physical quantities of the system such as speed, trajectory angle, horizontal displacement, vertical displacement, and additional mass during the inflation stage of the middle air chambers; the values ​​of the physical quantities at the end of this stage are used as the initial conditions for the next stage; Step three, the stage when the wing tip air chamber starts to inflate during the parachute opening stage, and the force of the canopy expanding outward increases until the sum of the downward pushing force of the closing cloth by the tension component of the parachute rope and the gravity of the closing cloth is greater than the aerodynamic resistance of the closing cloth is divided into the second stage, the two-end air chamber inflation stage; an air chamber inflation model for both ends is established, and the calculation parameters are substituted into the model to obtain the physical quantities of the system such as speed, trajectory angle, horizontal displacement, vertical displacement, and additional mass during the two-end air chamber inflation stage; the values ​​of the physical quantities at the end of this stage are used as the initial conditions for the next stage; Step four, when the sum of the outward expansion force of the parachute rope and the gravity of the closing cloth is greater than the aerodynamic resistance generated by the closing cloth, the balance is destroyed, the closing cloth slides down, and the parachute opening process enters the third stage; the characteristic of this stage is that the closing cloth begins to slide down from the lower wing surface of the canopy to the bottom of the parachute rope; according to the test data of the wing parachute airdrop test, the wing parachute in this stage is regarded as a round parachute, and the canopy resistance characteristics and speed of the inflation process are used as the differential relationship to establish a model of the canopy full inflation stage when the closing cloth slides down; substituting the canopy resistance characteristics and system speed at the end of the second stage, the canopy resistance characteristics and speed at any time in this stage can be obtained.

3. The calculation method applicable to the parafoil opening and inflation process according to claim 1 or 2, characterized in that: The step 1 obtains the parachute opening speed, opening height, canopy area, total parachuting mass, human body resistance characteristics, canopy extension, canopy average chord length, airfoil thickness, air inlet height, closing cloth size, closing cloth mass, closing cloth ring and parachute rope friction coefficient, and parachute rope characteristic length data.

4. The calculation method applicable to the parafoil opening and inflation process according to claim 1 or 2, characterized in that: The inflation model of the canopy middle air chamber established in step 2 is: Where: v——system speed, m / s; t——time, s; m s ——parachute system mass, kg; m w ——body mass, kg; m f ——Additional mass, kg; g——acceleration due to gravity, m 2 / s; θ——trajectory angle, rad; ρ——air density, kg / m 3 ; C(t)——canopy real-time drag coefficient; A——canopy area, m 2 ; CA w ——Human body resistance characteristics, take 0.5; x——horizontal displacement of the system, m; y——vertical displacement of the system, m; D0——nominal diameter of canopy, m t i ——The canopy filling time estimated by treating the parafoil similarly to a round parachute with a diameter of D0, s; V cell (t)——the volume of the middle air chamber, m 3 ; A in ——Inlet area of ​​the middle air chamber, m 2 ; At the end of the first stage, the canopy volume is: V cell (t final )=0.5L slider-span L thick (L chord +L slider-chord ) The intake area is: A in =L slider-span L thick f in The resistance characteristics at this stage are: Where: V cell (t final )——canopy volume at the end of the first stage, m 3 ; L slider-span ——Length of closing fabric, m; L slider-chord ——Width of closing fabric, m; L thick ——airfoil thickness, m; L chord ——airfoil chord length, m; f in - air intake efficiency; CA——system resistance characteristic, m; (CA) pilot ——Drag characteristics of the guide parachute, m.

5. The calculation method applicable to the parafoil opening and inflation process according to claim 1 or 2, characterized in that: The inflation model of the two-end air chambers established in step 3 is: Outer chamber inflation volume: V outboard-in =∫A outboard (t)u in dt V outboard-in ——Inflated volume of outer air chamber, m 3 ; A outbord (t)——intake area of ​​outer air chamber, m 2 ; u in ——intake air velocity, m / s; C n (t) is the drag coefficient, which is a function of the inclination angle Ω(t) when the sidewall is regarded as an inclined flat plate in the airflow. For most airfoils, C n (t) is quickly calculated according to the following formula: The aerodynamic resistance of the closing fabric is: (THAT) slider =1.12L slider-span IT slider-chord Where: F slider-drag —— aerodynamic resistance of the closing fabric, N; CA) slider ——resistance characteristics of the closing fabric, m; The drag characteristics of an umbrella are: CA(t)=1.12L span (t)L chord (t) L span (t) is the real-time expansion length of the canopy, L chord (t) is the real-time chord length of the canopy: L span (t)=L slider-span +2X(t) The downward push of the rope tension component on the closing cloth is: μ is the resistance coefficient of the slip ring The gravity of the closing fabric is G slider =9.81m slider m slider ——Mass of the closing fabric, kg; When F line-drive +G slider >F slider-drag When the balance is broken, the closing cloth slides down, and the parachute opening process enters the third stage; F line-drive —— downward component of the parachute line tension, N; F slider-drag ——Resistance of the closing fabric, N.

6. The calculation method applicable to the parafoil opening and inflation process according to claim 1 or 2, characterized in that: The model of the full inflation stage of the canopy during the closing and sliding down of the canopy established in step 4 is: K imp is the canopy expansion coefficient, which can be taken as a constant based on experience; When (CA)(t) increases to the system resistance characteristic, the entire parachute opening process is completed.

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