Method for calculating multi-field coupling thrust of carrier rocket interstage pneumatic separation system

Abstract

The invention discloses a multi-field coupling thrust calculation method for a carrier rocket interstage pneumatic separation system. The method comprises the following steps: 1, acquiring control parameters of the pneumatic separation system under an operation condition; 2, determining a real gas state equation in the gas cylinder; 3, deducing to obtain dynamic changes of gas pressure, mass and temperature in the gas cylinder; 4, valve and pipeline dynamic modeling is carried out; 5, establishing a high-speed high-pressure cylinder mathematical model; 6, judging whether the inter-stage separation performance of the first and second substages meets the requirement or not; if the requirement is met, the thrust time history response of the pneumatic separation system is output; and if not, returning to the step 1. The method not only can accurately obtain the thrust change characteristics of the carrier rocket interstage pneumatic separation system under the multi-field combined action, but also can obtain the dynamic response characteristics of the separation process of the first substage and the upper stage, and has reference significance for design optimization of the interstage pneumatic separation system.

Description

Technical Field

[0001] The invention relates to a multi-field coupling thrust calculation method for a launch vehicle interstage aerodynamic separation system, and belongs to the technical field of launch vehicle interstage separation characteristic calculation. Background Art

[0002] Traditionally, the separation between stages of a launch vehicle is achieved by using forward and reverse thrust solid rockets. This technology has high reliability but does not have the ability to be reused.

[0003] As reuse becomes the inevitable direction of the development of launch vehicles, non-pyrotechnic connection and separation technologies represented by aerodynamic separation technology are gradually replacing traditional pyrotechnic connection and separation technologies and becoming an important way to achieve reusability of the next generation of rockets.

[0004] The interstage separation of a launch vehicle is a process in which the first stage is shut down and then unlocked and separated from the second stage. A high-speed, high-load, and long-stroke pneumatic separation impulse system can ensure the smooth completion of the separation mission. During the interstage pneumatic separation process, high-pressure gas enters the cylinder through the pipeline to push the piston push rod. Under the action of thrust, the second stage is separated from the first stage, the gas temperature in the gas cylinder drops sharply, and the gas temperature in the cylinder rises sharply. This process involves the interaction of complex fluid-solid-heat multi-physics fields, which directly affects the success or failure of the separation mission. Therefore, how to accurately and effectively analyze the thrust change characteristics of the interstage pneumatic separation system of the launch vehicle under multi-field coupling is of great significance to ensure the safe and reliable operation of the system. At present, no relevant technical information has been found for the interstage pneumatic separation technology of the launch vehicle. Summary of the invention

[0005] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to provide a method for calculating the multi-field coupled thrust of an inter-stage aerodynamic separation system of a launch vehicle, which can accurately obtain the multi-field coupled thrust variation characteristics of the aerodynamic separation system, and can realize effective prediction of the inter-stage separation response of the launch vehicle.

[0006] The technical solution of the present invention is: a multi-field coupling thrust calculation method for a launch vehicle interstage aerodynamic separation system, wherein:

[0007] Step 1: obtaining operation control parameters according to the control conditions of the pneumatic separation system;

[0008] Step 2: Determine the true gas state equation in the gas cylinder according to the geometric characteristics and operation control parameters of the gas cylinder;

[0009] Step 3: Use the gas state equation of the real gas in the gas cylinder to derive the change of the gas pressure, mass and temperature in the gas cylinder over time;

[0010] Step 4: Establish flow continuity equations from the gas cylinder to the valve and from the valve to the high-pressure cylinder according to the control parameters of the valve and pipeline in the pneumatic separation system, as well as pressure loss equations of the gas in the pipeline from the gas cylinder to the valve and from the valve to the high-pressure cylinder;

[0011] Step 5: Divide the high-pressure cylinder into a rod chamber and a rodless chamber. According to steps 2, 3, and 4, obtain the real gas characteristics of the gas in the rodless chamber of the high-pressure cylinder, obtain the relationship between the pressure, mass, and temperature of the gas in the rodless chamber and the time, and analyze the relationship between the volume, pressure, and temperature of the gas in the rodless chamber and the rod chamber and the time during the pneumatic separation between the first and second sub-stages.

[0012] Step 6: Based on the information from steps 1 to 5, solve the response of the pneumatic separation system, including the relationship between the push rod thrust, the relative displacement of the pneumatic push rod, and the pressure and temperature changes over time; when the separation performance between the first and second sub-stages meets the index requirements, output the response of the pneumatic separation system; if it does not meet the requirements, return to step 1 and recalculate.

[0013] Preferably, the van der Waals equation is used to determine the true gas state equation in the gas cylinder, specifically:

[0014]

[0015] Among them, p c 、m c 、V c and T c are the pressure, mass, volume and absolute temperature of the gas in the cylinder respectively, R and M are the gas constant and molar mass in the cylinder, a and b are the van der Waals constants of the gas.

[0016] Preferably, the changes in the gas pressure, mass and temperature in the gas cylinder over time are as follows:

[0017]

[0018] in, and It represents the change in pressure, quality and temperature of the gas in the gas cylinder per unit time, and F represents the real gas state equation in the gas cylinder.

[0019] Preferably, the mass conservation principle is used when the gas flows in the gas cylinder, valve, pipeline and rodless cavity of the high-pressure cylinder during the operation of the pneumatic separation system, and according to the control parameters of the valve and pipeline in the pneumatic separation system, the following is obtained:

[0020] The flow continuity equation from the cylinder to the valve is:

[0021]

[0022] The flow continuity equation from the valve to the high-pressure cylinder is:

[0023]

[0024] In the formula, m c is the mass of the gas in the cylinder, m no is the mass of gas in the rodless chamber of the high-pressure cylinder, q m1 and q m2 are the gas mass flow rates at the valve inlet and outlet, respectively, satisfying q m1 =q m2 .

[0025] Preferably, the pressure loss Δp1 generated when the gas cylinder flows out through the pipeline to the valve inlet is:

[0026]

[0027] The pressure loss Δp2 generated from the valve outlet through the pipeline to the rodless chamber of the high-pressure cylinder is:

[0028]

[0029] In the above equation, λ is the resistance coefficient along the laminar flow state, d is the pipeline diameter, v is the gas flow rate, ζ is the local resistance coefficient, g is the acceleration of gravity, L1 is the length of the pipeline from the gas cylinder to the valve inlet, and L2 is the length of the pipeline from the valve outlet to the rodless cavity of the cylinder.

[0030] Preferably, in the rodless chamber and the rod chamber of the high-pressure cylinder, the relationship between the volume change of the gas and the piston movement is:

[0031]

[0032] Where x is the relative displacement of the piston, A no and A rod are the effective areas of the pistons in the rodless and rod chambers, V no and V rod are the volumes of the rodless chamber and the rod chamber of the cylinder respectively.

[0033] Preferably, during the pneumatic separation process between the first and second sub-stages, when the gas in the gas cylinder is continuously pumped into the high-pressure cylinder, the movement of the piston push rod in the cylinder is divided into three stages: static friction stage, dynamic friction stage, and pressure relief stage;

[0034] In the static friction stage, the pneumatic push rod has not yet moved, and its initial position is the lowest end. As the gas cylinder supplies gas to the rodless cavity, the static friction force f between the first and second sub-stages gradually increases. The maximum value of the static friction force satisfies p no A no -p rod A rod -f=0, where pno and p rod are the pressures in the rodless cavity and the rod cavity respectively;

[0035] In the dynamic friction stage, the cylinder continues to supply gas to the rodless cavity. When p no A no -p rod A rod When -f>0, the first stage is decelerated by the force in the opposite direction of the rocket, and the second stage is accelerated by the force in the same direction as the rocket, thus achieving interstage separation;

[0036] During the pressure relief stage, after the piston stroke is completed, the rodless chamber is depressurized and the piston rod is reset; while the pressure relief valve is opened, the pipeline solenoid valve is closed to retain the gas in the gas cylinder.

[0037] Preferably, in the dynamic friction stage of the first and second sub-stage pneumatic separation process, the relationship between the volume and pressure of the rod chamber and the rodless chamber in the cylinder and the time t is as follows:

[0038]

[0039] Where p no and p rod are the pressures in the rodless cavity and the rod cavity respectively, A no and A rod are the effective areas of the rodless and rod pistons, respectively; f is the maximum static friction between the piston and the high-pressure cylinder body; B1 and B2 are the viscous damping between the piston push rod and the cylinder body, and between the atmosphere and the second-stage rocket body, respectively; β is the correction value considering the change of gravity acceleration at altitude and the angle between the gravity direction and the axial direction of the rocket body; g is the gravity acceleration; M1 and M2 are the total masses of the first and second stages, respectively; x is the relative displacement of the piston; x1 is the displacement of the first stage; and x2 is the displacement of the second stage.

[0040] Preferably, the relationship between the gas pressure in the rodless cavity and the time t during the pressure relief stage is:

[0041]

[0042] In the formula, p no is the pressure in the rodless cavity, V no is the volume of the rodless cavity; m no is the mass of the gas in the rodless cavity, T no is the rodless chamber temperature, R and M are the gas constant and molar mass in the cylinder, and a and b are the van der Waals constants of the gas.

[0043] Preferably, the operation control parameters include the initial pressure value of the gas cylinder in the pneumatic separation system, the gas temperature, the volume of the gas cylinder, the valve diameter, the pipeline diameter, and the cylinder structure size.

[0044] Compared with the prior art, the present invention has the following advantages:

[0045] (1) A complete launch vehicle interstage pneumatic separation system from gas cylinders to pipelines, valves, and cylinders was established, including the mass parameters of the first and second stages of the launch vehicle, which can be used for launch vehicle interstage pneumatic separation technology, filling the gap in domestic launch vehicle interstage pneumatic separation technology;

[0046] (2) Based on the real gas state equation, a large-load, high-speed, high-pressure cylinder is used as the actuator, and considering the real physical boundary conditions, an equation for calculating the pneumatic separation between the first and second sub-stages is established. The relationship between the volume, pressure, and temperature of the gas in the rod chamber and the rodless chamber of the cylinder and the change of the piston displacement is obtained, so that the deviation of the calculation result can be controlled within 8%;

[0047] (3) The present invention can effectively obtain the thrust load acting on the first and second sub-stage separation process, and can accurately obtain the dynamic performance characteristics of the inter-stage separation, which helps to deepen the understanding of the entire process of dynamic response of the pneumatic separation system under extreme service environment by engineering personnel;

[0048] (4) The method of the present invention makes the analysis of the thrust response of a large-load, high-speed, high-pressure pneumatic separation impulse system more economical and rapid, not only avoiding the consumption of manpower and material resources in the test process, but also enabling engineers to more intuitively obtain the distribution of the pressure in the cylinder during the separation process and the thrust change characteristics of the pneumatic push rod;

[0049] (5) The present invention has wide applicability and can be applied to the dynamic simulation of the separation mechanism under multi-field coupling under conditions such as the general core stage bundling separation of the launch vehicle, the fairing separation, and the satellite-rocket separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is a flow chart of the method of the present invention;

[0051] Figure 2 A schematic diagram of a pneumatic separation system dynamics model according to an embodiment of the present invention;

[0052] The accompanying drawings are marked as follows: 1-gas cylinder, 2-pipeline, 3-solenoid valve, 4-pressure relief valve, 5-cylinder rodless chamber, 6-cylinder rod chamber, 7-pneumatic push rod;

[0053] Figure 3 It is a time history curve diagram of the thrust of the pneumatic push rod during the interstage separation process of the embodiment of the present invention;

[0054] Figure 4 It is a time history curve diagram of the relative displacement of the pneumatic push rod during the inter-stage separation process of the embodiment of the present invention;

[0055] Figure 5This is a graph showing changes in the pressure of a gas cylinder during the inter-stage separation process of an embodiment of the present invention;

[0056] Figure 6 This is a curve diagram of the temperature change of the gas cylinder during the inter-stage separation process of an embodiment of the present invention. DETAILED DESCRIPTION

[0057] The present invention considers the influence of flow field, structural field and temperature field, and provides a multi-field coupling thrust calculation method for the interstage aerodynamic separation system of a launch vehicle. The proposed method can not only accurately obtain the multi-field coupling thrust variation characteristics of the aerodynamic separation system, but also realize the effective prediction of the interstage separation response of the launch vehicle.

[0058] In order to achieve the above object, the present invention adopts the following technical solution:

[0059] Step 1: Obtaining the operating control parameters of the pneumatic separation system under operating conditions;

[0060] According to the control conditions of the pneumatic separation system, the basic characteristic operation control parameters such as the initial pressure value of the gas cylinder, gas temperature, gas cylinder volume, valve diameter, pipeline diameter, cylinder structure size, etc. in the pneumatic separation system are obtained;

[0061] Step 2: Determine the true gas state equation in the cylinder;

[0062] According to the geometric characteristics and operation control parameters of the cylinder, the van der Waals equation is used to analyze the release process of the helium cylinder. c 、m c 、V c and T c are the pressure, mass, volume and absolute temperature of the gas in the cylinder, R and M are the gas constant and molar mass in the cylinder, a and b are the van der Waals constants of the gas, then the real gas state equation in the cylinder is:

[0063]

[0064] Step 3: Use the gas state equation of the real gas in the gas cylinder to derive the dynamic changes of the gas pressure, mass and temperature in the gas cylinder;

[0065] During the gas release process of the gas cylinder, the volume of the gas cylinder is constant, and the gas pressure, gas mass and gas temperature in the gas cylinder are variables. By solving the partial differential equation on both sides of equation (2), the change of the gas pressure, mass and temperature in the gas cylinder with time is obtained as follows:

[0066]

[0067] in, and Characterizes the change in pressure, quality and temperature of the gas in the cylinder per unit time.

[0068] Step 4: Carry out valve and pipeline dynamics modeling;

[0069] During the operation of the pneumatic separation system, the gas in the cylinder, valve, pipeline and rodless cavity of the high-pressure cylinder maintains mass conservation. According to the control parameters of the valve and pipeline in the pneumatic separation system, the flow continuity equation from the cylinder to the valve and from the pipeline to the high-pressure cylinder can be obtained;

[0070] The flow continuity equation from the cylinder to the valve is:

[0071]

[0072] The flow continuity equation from the valve to the high-pressure cylinder is:

[0073]

[0074] In the formula, m c is the mass of the gas in the cylinder, m no is the mass of gas in the rodless chamber of the high-pressure cylinder, q m1 and q m2 are the gas mass flow rates at the valve inlet and outlet, respectively, satisfying q m1 =q m2 .

[0075] There will be pressure loss in the process of gas flowing from the cylinder to the valve and from the valve to the rodless chamber of the cylinder. The pressure loss in each process consists of two parts: one is the loss along the straight line of the pipeline, and the other is the local pressure loss caused by the sudden reduction of the cut-off area when the gas enters the pipeline.

[0076] The gas flows out from the gas cylinder through the pipeline to the valve inlet and flows out from the valve outlet through the pipeline to the rodless chamber of the cylinder respectively:

[0077]

[0078] Among them, λ is the drag coefficient along the laminar flow state, and its calculation formula is related to the Reynolds number. d is the pipeline diameter, v is the gas flow rate, ζ is the local drag coefficient, g is the gravitational acceleration, L1 is the length of the pipeline from the gas cylinder to the valve, L2 is the length of the pipeline from the valve to the rodless cavity of the cylinder, and the subscripts "1" and "2" correspond to the two sections of the pipeline from the gas cylinder to the valve inlet and the valve to the rodless cavity of the high-pressure cylinder, respectively.

[0079] Step 5: Establish a mathematical model of high-speed and high-pressure cylinder;

[0080] The high-pressure cylinder is divided into two parts: the rod chamber and the rodless chamber. In the calculation process, the van der Waals equation is first used to analyze the real gas characteristics in the rodless chamber and the rod chamber of the cylinder, and the changes in the gas pressure, mass and temperature in the rodless chamber and the rod chamber over time are obtained according to the methods in step 2 and step 3. At the same time, according to the first law of thermodynamics, the high-pressure gas in the cylinder is passed into the high-pressure cylinder to drive the piston to move. The piston movement will cause the volume of the high-pressure cylinder to change. The relationship between the volume change of the rodless chamber and the rod chamber gas and the piston movement is established as follows:

[0081]

[0082] Where x is the relative displacement of the piston, A no and A rod are the effective areas of the pistons in the rodless and rod chambers, V no and V rod The volume of the cylinder's rodless chamber and rod chamber.

[0083] During the separation process, when the gas in the cylinder is continuously pumped into the high-pressure cylinder, the movement of the piston push rod in the high-pressure cylinder can be divided into three stages, namely 1) static friction stage; 2) dynamic friction stage; 3) pressure relief stage. In the static friction stage, the pneumatic push rod has not yet moved, and its initial position is the lowest end. As the cylinder supplies gas to the rodless cavity, the static friction force (f) between the first and second sub-stages gradually increases, and the maximum value of the static friction force satisfies p no A no -p rod A rod -f=0, where p no and p rod are the pressures in the rodless cavity and the rod cavity respectively; in the dynamic friction stage, the gas cylinder continues to supply gas to the rodless cavity. When p no A no -p rod A rod When -f>0, the first stage is decelerated by the force in the opposite direction of the rocket, and the second stage is accelerated by the force in the same direction of the rocket's flight, thus achieving interstage separation. During the dynamic friction stage of the first and second stage separation process, the changes in the volume and pressure of the rod chamber and the rodless chamber in the cylinder with time satisfy the following equation:

[0084]

[0085]

[0086] Where f is the maximum static friction between the piston and the high-pressure cylinder body, B1 and B2 are the viscous damping between the piston push rod and the cylinder body, and between the atmosphere and the second-stage rocket body, respectively; β is the correction value considering the change of gravity acceleration at altitude and the angle between the gravity direction and the axial direction of the rocket body; M1 and M2 are the total masses of the first and second stages, respectively; x is the relative displacement of the piston, x1 is the displacement of the first stage, and x2 is the displacement of the second stage.

[0087] In the pressure relief stage, after the piston stroke is completed, the rodless chamber is depressurized and the piston rod is reset. While the pressure relief valve is opened, the pipeline solenoid valve is closed to retain the gas in the cylinder. At this time, the relationship between the gas pressure in the rodless chamber and time is:

[0088]

[0089] In the formula, p no is the pressure in the rodless cavity, V no is the volume of the rodless chamber of the high-pressure cylinder; m no is the mass of gas in the rodless chamber of the high-pressure cylinder, T no is the rodless chamber temperature, R and M are the gas constant and molar mass in the cylinder, and a and b are the van der Waals constants of the gas.

[0090] The above equations (steps 1 to 5) are combined to obtain the response of the pneumatic separation system, including the push rod thrust, the relative displacement of the pneumatic push rod, the relationship between the pressure and temperature over time, etc. Figure 2 to Figure 6 shown.

[0091] Step 6: Determine whether the separation performance between the first and second sub-stages meets the requirements; if so, output the thrust of the pneumatic separation system and the dynamic response of the first and second sub-stage separation process; if not, return to step 1.

[0092] The requirements for the separation performance between the first and second sub-stages that need to be met are: the displacement or speed of the piston actuation meets the separation index requirements between the first and second sub-stages.

[0093] Example:

[0094] The specific implementation methods of the method of the present invention will be described in detail below with reference to examples:

[0095] Step 1: Obtain control parameters of the pneumatic separation system under operating conditions;

[0096] According to the system control conditions, the basic characteristic operation control parameters such as the initial pressure value of the gas cylinder, the volume of the gas cylinder, the valve diameter, the pipeline diameter, and the cylinder structure size in the pneumatic separation system are obtained;

[0097] According to the system control conditions, the example of the present invention obtains that the initial pressure value of the gas cylinder is 35MPa, the volume of the gas cylinder is 60L, the diameter and pipe diameter of the solenoid valve / pressure relief valve are 16mm, the initial temperature is 293K, the pressure relief time is 0.3s after the solenoid valve is opened, and the cylinder diameter and the pneumatic push rod diameter are 140mm and 100mm respectively.

[0098] Step 2: Determine the true gas state equation in the cylinder;

[0099] According to the geometric characteristics and operation control parameters of the cylinder, the van der Waals equation is used to analyze the release process of the helium cylinder. c 、m c , V and T c are the pressure, mass, volume and absolute temperature of the gas in the cylinder, R and M are the gas constant and molar mass in the cylinder, a and b are the van der Waals constants of the gas, then the real gas state equation in the cylinder is:

[0100]

[0101] In the present embodiment, according to the control parameters of the gas cylinder in step 1, the real gas state equation in the gas cylinder is determined by equations (1) and (2). Among them, the gas constant R and molar mass M in the gas cylinder are 4.0026 g / mol and 8.314 J / (mol·K) respectively, and the van der Waals constants a and b of helium are 0.034 m 6 Pa / mol 2 and 2.4×10 -6 m 3 / mol.

[0102] Step 3: Derive the dynamic changes of gas pressure, quality and temperature in the gas cylinder;

[0103] During the gas release process of the gas cylinder, the volume of the gas cylinder is constant, and the gas pressure, gas mass and gas temperature in the gas cylinder are variables. By solving the partial differential equation on both sides of equation (2), the change of the gas pressure, mass and temperature in the gas cylinder with time is obtained as follows:

[0104]

[0105] in, and Characterizes the change in pressure, quality and temperature of the gas in the cylinder per unit time.

[0106] In the embodiment of the present invention, according to the real gas state equation obtained in step 2, the partial differential equation is calculated to obtain the dynamic changes of the gas pressure, mass and temperature in the gas cylinder. and , where the cylinder temperature differential equation satisfies the first law of thermodynamics.

[0107] Step 4: Carry out valve and pipeline dynamics modeling;

[0108] During the operation of the pneumatic separation system, the gas flow in the rodless cavity of the gas cylinder, valve, pipeline and high-pressure cylinder maintains mass conservation. According to the control parameters of the valve and pipeline in the pneumatic separation system, the flow continuity equation from the gas cylinder to the valve and from the pipeline to the high-pressure cylinder can be obtained as follows:

[0109]

[0110] In the formula, m no is the mass of gas in the rodless chamber of the high-pressure cylinder, q m1 and q m2 are the gas mass flow rates at the valve inlet and outlet, respectively, satisfying q m1 =q m2 When the gas flows out of the cylinder through the pipeline to the valve inlet (Δp1) and from the valve outlet to the rodless chamber of the cylinder (Δp2), pressure loss will occur. The pressure loss is composed of two parts. One part is the loss along the straight line of the pipeline, and the other part is the local pressure loss caused by the sudden reduction of the cut-off area when the gas enters the pipeline from the cylinder, that is,

[0111]

[0112] Among them, λ is the drag coefficient along the laminar flow state, and its calculation formula is related to the Reynolds number, d is the pipeline diameter, v is the gas flow rate, ζ is the local drag coefficient, g is the gravitational acceleration, and the subscripts "1" and "2" correspond to the two sections of the pipeline from the gas cylinder to the valve inlet and the valve to the rodless chamber of the high-pressure cylinder, respectively.

[0113] The pneumatic separation system cylinder, valve, pipeline and high-pressure cylinder model established in the present invention are as follows: Figure 2 As shown, the connection relationship between the gas cylinder 1, pipeline 2, solenoid valve 3, pressure relief valve 4, cylinder rodless chamber 5, cylinder rod chamber 6, and pneumatic push rod 7 is as follows: the gas cylinder 1 is connected to the solenoid valve 3 through the pipeline 2, the other end of the pressure relief valve 4 and the solenoid valve 3 is connected to the rodless chamber of the cylinder (cylinder rodless chamber 5), the piston of the pneumatic push rod 7 is located in the cylinder, and the cylinder is divided into the cylinder rodless chamber 5 and the cylinder rod chamber 6. The pressure loss of the pipeline flowing through the front and back of the valve is considered respectively, the local resistance coefficient ζ1=0.458 when the gas enters the pipeline from the gas cylinder, and the local resistance coefficient ζ2=0.752 when the gas enters the cylinder rodless chamber.

[0114] Step 5: Establish a mathematical model of high-speed and high-pressure cylinder;

[0115] The high-pressure cylinder is divided into two parts: the rod chamber and the rodless chamber. In the calculation process, the van der Waals equation is first used to analyze the real gas characteristics in the rodless chamber and the rod chamber of the cylinder, and the changes in the gas pressure, mass and temperature in the rodless chamber and the rod chamber over time are obtained according to the methods in steps 2 and 3. At the same time, according to the first law of thermodynamics, the high-pressure gas in the cylinder is passed into the cylinder to drive the piston to move. The piston movement will cause the cylinder volume to change. The relationship between the volume change of the rodless chamber and the rod chamber gas and the piston movement is established as follows:

[0116]

[0117] Where x is the relative displacement of the piston, A no and A rod are the effective areas of the pistons in the rodless and rod chambers, V no and V rod Volume of the rodless and rod chambers of the cylinder. Separation process When the gas in the cylinder is continuously pumped into the cylinder, the movement of the piston push rod in the cylinder can be divided into three stages, namely 1) static friction stage; 2) dynamic friction stage; 3) pressure relief stage. In the static friction stage, the pneumatic push rod has not yet moved, and its initial position is the lowest end. As the cylinder supplies gas to the rodless chamber, the static friction force (f) between the first and second sub-stages gradually increases. The maximum value of the static friction force satisfies p no A no -p rod A rod -f=0, where p no and p rod are the pressures in the rodless cavity and the rod cavity respectively; in the dynamic friction stage, the gas cylinder continues to supply gas to the rodless cavity. When p no A no -p rod A rod When -f>0, the first stage is decelerated by the force in the opposite direction of the rocket, and the second stage is accelerated by the force in the same direction of the rocket, thus achieving interstage separation. During the separation of the first and second stages, the changes in the volume and pressure of the rod chamber and the rodless chamber in the cylinder satisfy the following equation

[0118]

[0119] Where f is the maximum static friction between the piston and the cylinder body, B1 and B2 are the viscous damping between the piston push rod and the cylinder body, the atmosphere and the second-stage rocket body, respectively, β is the correction value considering the change of gravity acceleration at altitude and the angle between the gravity direction and the axial direction of the rocket body, and M1 and M2 are the total masses of the first and second stages, respectively. In the pressure relief stage, after the piston stroke is completed, the rodless chamber is depressurized and the piston rod is reset. While the pressure relief valve is opened, the pipeline solenoid valve is closed to retain the gas in the gas cylinder. At this time, the relationship between the gas pressure in the rodless chamber and time is:

[0120]

[0121] The above equations are combined to obtain the thrust of the aerodynamic separation system and the dynamic response of the first and second stage separation process.

[0122] In the example of the present invention, the total mass of the first and second stages of the launch vehicle is 35t and 75t respectively. According to equations (9) to (13), a mathematical model of a high-speed high-pressure cylinder is established, and the variables in the equations are combined with the equations given in steps 1 to 5. The control equations are integrated in the mathematical calculation software to establish a multi-field coupling simulation calculation platform for the interstage aerodynamic separation system of the launch vehicle. The multi-field coupling thrust dynamic characteristics of the interstage aerodynamic separation system of the launch vehicle obtained by simulation in the example of the present invention are as follows: Figure 3 As shown. From the figure, it can be observed intuitively that when the electromagnetic valve of the pneumatic separation system is opened (0-0.4ms), the high-pressure gas flows into the rodless chamber of the cylinder, and the pressure of the pneumatic push rod gradually increases to a maximum value of 507.8kN. The thrust slowly decreases from 0.4ms to 0.3s. This is mainly due to the increase in the volume of the rodless chamber in the cylinder. After 0.3s, the pressure relief valve opens and the push rod thrust gradually decreases. After 0.35s, after the interstage separation, the cylinder thrust shows a small oscillation due to the action of the pneumatic spring pre-stamped in the rod chamber. According to steps one to five, it can also be obtained as follows Figures 4 to 6 The dynamic performance characteristics of the pneumatic separation system under multi-field coupling, including the relative displacement time history of the pneumatic push rod, the pressure change of the gas cylinder and the temperature change of the inter-stage separation, can be seen. It can be seen that during the inter-stage separation process, the gas cylinder pressure drops and finally stabilizes to 21.24MPa. After stabilization, the gas cylinder temperature is 249K, which is 44°C lower than the initial moment. The relative displacement of the piston is 1.015m at the separation moment of 0.35s, which meets the pneumatic separation performance index.

[0123] Step 6: Determine whether the separation performance between the first and second sub-stages meets the requirements; if so, output the thrust time history response of the aerodynamic separation system; if not, return to step 1.

[0124] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in this field.

Claims

1. A multi-field coupling thrust calculation method for a launch vehicle interstage aerodynamic separation system, characterized in that include: Step 1: obtaining operation control parameters according to the control conditions of the pneumatic separation system; Step 2: Determine the true gas state equation in the gas cylinder according to the geometric characteristics and operation control parameters of the gas cylinder; Step 3: Use the gas state equation of the real gas in the gas cylinder to derive the change of the gas pressure, mass and temperature in the gas cylinder over time; Step 4: Establish flow continuity equations from the gas cylinder to the valve and from the valve to the high-pressure cylinder according to the control parameters of the valve and pipeline in the pneumatic separation system, as well as pressure loss equations of the gas in the pipeline from the gas cylinder to the valve and from the valve to the high-pressure cylinder; Step 5: Divide the high-pressure cylinder into a rod chamber and a rodless chamber. According to steps 2, 3, and 4, obtain the real gas characteristics of the gas in the rodless chamber of the high-pressure cylinder, obtain the relationship between the pressure, mass, and temperature of the gas in the rodless chamber and the time, and analyze the relationship between the volume, pressure, and temperature of the gas in the rodless chamber and the rod chamber and the time during the pneumatic separation between the first and second sub-stages. Step 6: Based on the information from steps 1 to 5, solve the response of the pneumatic separation system, including the relationship between the push rod thrust, the relative displacement of the pneumatic push rod, and the pressure and temperature changes over time; when the separation performance between the first and second sub-stages meets the index requirements, output the response of the pneumatic separation system; if it does not meet the requirements, return to step 1 and recalculate.

2. The method for calculating multi-field coupling thrust of a launch vehicle interstage aerodynamic separation system according to claim 1, characterized in that: The van der Waals equation is used to determine the true gas state equation in the gas cylinder, which is: Among them, p c 、m c 、V c and T c are the pressure, mass, volume and absolute temperature of the gas in the cylinder respectively, R and M are the gas constant and molar mass in the cylinder, a and b are the van der Waals constants of the gas.

3. A method for calculating multi-field coupling thrust of a launch vehicle interstage aerodynamic separation system according to claim 2, characterized in that: The changes of gas pressure, quality and temperature in the gas cylinder over time are as follows: in, and It represents the change in pressure, quality and temperature of the gas in the gas cylinder per unit time, and F represents the real gas state equation in the gas cylinder.

4. The method for calculating multi-field coupling thrust of a launch vehicle interstage aerodynamic separation system according to claim 2, characterized in that: Using the mass conservation principle of gas flow in the cylinder, valve, pipeline and rodless cavity of the high-pressure cylinder during the working process of the pneumatic separation system, and based on the control parameters of the valves and pipelines in the pneumatic separation system, we get: The flow continuity equation from the cylinder to the valve is: The flow continuity equation from the valve to the high-pressure cylinder is: In the formula, m c is the mass of the gas in the cylinder, m no is the mass of gas in the rodless chamber of the high-pressure cylinder, q m1 and q m2 are the gas mass flow rates at the valve inlet and outlet, respectively, satisfying q m1 =q m2 .

5. A method for calculating multi-field coupling thrust of a launch vehicle interstage aerodynamic separation system according to claim 4, characterized in that: The pressure loss Δp1 generated when the gas cylinder flows out through the pipeline to the valve inlet is: The pressure loss Δp2 generated from the valve outlet through the pipeline to the rodless chamber of the high-pressure cylinder is: In the above equation, λ is the resistance coefficient along the laminar flow state, d is the pipeline diameter, v is the gas flow rate, ζ is the local resistance coefficient, g is the acceleration of gravity, L1 is the length of the pipeline from the gas cylinder to the valve inlet, and L2 is the length of the pipeline from the valve outlet to the rodless cavity of the cylinder.

6. The method for calculating multi-field coupling thrust of a launch vehicle interstage aerodynamic separation system according to claim 3, characterized in that: In the rodless chamber and rod chamber of the high-pressure cylinder, the relationship between the volume change of the gas and the piston movement is: Where x is the relative displacement of the piston, A no and A rod are the effective areas of the pistons in the rodless and rod chambers, V no and V rod are the volumes of the rodless chamber and the rod chamber of the cylinder respectively.

7. A method for calculating multi-field coupling thrust of a launch vehicle interstage aerodynamic separation system according to claim 6, characterized in that: During the pneumatic separation between the first and second sub-stages, when the gas in the gas cylinder is continuously pumped into the high-pressure cylinder, the movement of the piston push rod in the cylinder is divided into three stages: static friction stage, dynamic friction stage, and pressure relief stage; In the static friction stage, the pneumatic push rod has not yet moved, and its initial position is the lowest end. As the gas cylinder supplies gas to the rodless cavity, the static friction force f between the first and second sub-stages gradually increases. The maximum value of the static friction force satisfies p no A no -p rod A rod -f=0 where p no and p rod are the pressures in the rodless cavity and the rod cavity respectively; In the dynamic friction stage, the cylinder continues to supply gas to the rodless cavity. When p no A no -p rod A rod When -f>0, the first stage is decelerated by the force in the opposite direction of the rocket, and the second stage is accelerated by the force in the same direction as the rocket, thus achieving interstage separation; During the pressure relief stage, after the piston stroke is completed, the rodless chamber is depressurized and the piston rod is reset; while the pressure relief valve is opened, the pipeline solenoid valve is closed to retain the gas in the gas cylinder.

8. A method for calculating multi-field coupling thrust of a launch vehicle interstage aerodynamic separation system according to claim 7, characterized in that: In the dynamic friction stage of the first and second stage pneumatic separation process, the relationship between the volume and pressure of the rod chamber and the rodless chamber in the cylinder and the time t is as follows: Where p no and p rod are the pressures in the rodless cavity and the rod cavity respectively, A no and A rod are the effective areas of the rodless and rod pistons, respectively; f is the maximum static friction between the piston and the high-pressure cylinder body; B1 and B2 are the viscous damping between the piston push rod and the cylinder body, and between the atmosphere and the second-stage rocket body, respectively; β is the correction value considering the change of gravity acceleration at altitude and the angle between the gravity direction and the axial direction of the rocket body; g is the gravity acceleration; M1 and M2 are the total masses of the first and second stages, respectively; x is the relative displacement of the piston; x1 is the displacement of the first stage; and x2 is the displacement of the second stage.

9. The method for calculating multi-field coupling thrust of a launch vehicle interstage aerodynamic separation system according to claim 7, characterized in that: The relationship between the gas pressure in the rodless cavity and time t during the pressure relief stage is: In the formula, p no is the pressure in the rodless cavity, V no is the volume of the rodless cavity; m no is the mass of the gas in the rodless cavity, T no is the rodless chamber temperature, R and M are the gas constant and molar mass in the cylinder, and a and b are the van der Waals constants of the gas.

10. The method for calculating multi-field coupling thrust of a launch vehicle interstage aerodynamic separation system according to claim 1, characterized in that: The operating control parameters include the initial pressure value of the gas cylinder in the pneumatic separation system, gas temperature, gas cylinder volume, valve diameter, pipeline diameter, and cylinder structure size.

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