Rocket pulsating pressure load time domain design method

Abstract

The invention relates to a rocket pulsating pressure load time domain design method, and belongs to the technical field of aerospace systems. Performing a wind tunnel test on the scale model of the carrier rocket, and determining a distribution rule of arterial pressure; selecting an external force identification vibration measuring point according to the actual flight condition of the carrier rocket; preprocessing vibration data collected by the external force identification vibration measuring points to obtain vibration telemetering time domain data; acquiring a time-domain external force spectrogram of the single launch of the carrier rocket; repeating the steps for m-1 times to obtain the time domain external force spectrogram envelope of m launch times of the carrier rocket, namely the time domain curve of the carrier rocket external force model; m is a positive integer not less than 5; according to the time domain curve of the carrier rocket external force model and the scale model of the carrier rocket, the pulsating pressure load of the rocket is obtained; through transient response analysis of the high-precision kinetic model, a time domain calculation method for the pulsating pressure elastic load is obtained, and effective load shedding of the rocket flight transverse elastic load is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of aerospace systems and relates to a time-domain design method for a rocket pulsating pressure load. Background Art

[0002] When the active section of a launch vehicle flies at transonic speed in the atmosphere, local unsteady aerodynamic forces will be generated at the sudden change of the rocket body shape, namely, the pulsating pressure of the alternating separation flow and attachment flow and the pulsating pressure of the shock wave oscillation. Since its main energy is concentrated in the low-frequency band, it will cause the lateral elastic vibration of the entire launch vehicle. As the scale of the launch vehicle increases, the proportion of the rocket elastic load caused by the pulsating pressure interference in the total load gradually increases, and its refined design is very critical to improving the launch vehicle's carrying efficiency and structural efficiency.

[0003] In the traditional design method of pulsating pressure load for launch vehicles, the magnitude, distribution and power spectrum density of pulsating pressure at different Mach numbers of the specific rocket shape are first obtained through wind tunnel scale test. Then, when calculating the elastic load, it is assumed that the launch vehicle is subjected to a steady-state pulsating pressure external load, and the steady-state elastic response of the rocket structure under steady-state random input force is calculated according to the power spectrum density of the pulsating pressure. The frequency domain method is used. However, according to the mechanism of pulsating pressure generation, in the flight profile of the launch vehicle, the time for the rocket to fly through the strong wind area (0.8-1.2Ma) is very short, only a few seconds, and the dynamic pressure changes rapidly. Therefore, in the actual flight profile, the rocket structure has not been excited to steady-state vibration before it has flown through the pulsating pressure influence area. The traditional steady-state response calculation method under full excitation will overestimate the pulsating pressure load and affect the efficiency of the launch vehicle structure. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to propose a time domain design method for rocket pulsating pressure load, to obtain a time domain calculation method for pulsating pressure elastic load through high-precision dynamic model transient response analysis, and to achieve effective load reduction of the lateral elastic load of the rocket flight.

[0005] The solution of the present invention is:

[0006] A rocket pulsating pressure load time domain design method, comprising:

[0007] Step 1: Conduct wind tunnel tests on a scaled model of the launch vehicle to determine the distribution of arterial pressure;

[0008] Step 2: Select external force identification vibration measurement points according to the actual flight conditions of the launch vehicle;

[0009] Step 3: After the launch vehicle flies, the vibration data collected from the external force identification vibration measurement points determined in step 2 are preprocessed to obtain vibration telemetry time domain data;

[0010] Step 4: Obtain a time-domain external force spectrum diagram of a single launch of the launch vehicle according to the arterial pressure distribution law determined in step 1, the external force identification vibration measurement points determined in step 2, and the vibration telemetry time-domain data obtained in step 3;

[0011] Step 5, repeat step 3 to step 4 m-1 times to obtain the envelope of the time domain external force spectrum diagram of the launch vehicle m times, that is, the time domain curve of the launch vehicle external force model; m is a positive integer not less than 5;

[0012] Step six: According to the time domain curve of the launch vehicle external force model in step five and the scaled model of the launch vehicle in step one, the pulsating pressure load of the rocket is obtained.

[0013] In the above-mentioned rocket pulsating pressure load time domain design method, in the step one, a wind tunnel test is carried out on a scaled model of a launch vehicle to obtain a curve of the change of the root mean square magnitude of the pulsating pressure with the height of the scaled model of the launch vehicle.

[0014] In the above-mentioned rocket pulsating pressure load time domain design method, the distribution law of arterial pressure is:

[0015] The pulsating pressure is concentrated at the places where the shape of the launch vehicle changes, including the interface between the fairing cone and column, the inverted cone of the fairing, and the interface between the booster cone and column; therefore, the pulsating pressure is equivalent to a multi-point concentrated load.

[0016] In the above-mentioned time-domain design method for a rocket pulsating pressure load, in the step 2, according to the frequency and mode of the launch vehicle, the energy of the pulsating pressure is concentrated in the low frequency; the low frequency is below 20 Hz.

[0017] In the above-mentioned time-domain design method of a rocket pulsating pressure load, according to the specific mode of the launch vehicle, the positions with large full-rocket modal displacement in the first few low-frequency modes are selected as external force identification vibration measurement points, including the satellite-rocket interface, fairing, interstage, and tail section.

[0018] In the above-mentioned time-domain design method for rocket pulsating pressure load, in step three, the rocket body frequency of the carrier rocket is low frequency, and the high-frequency component in the vibration data affects the accuracy of external force identification.

[0019] In the above-mentioned rocket pulsating pressure load time domain design method, the specific method of the preprocessing is:

[0020] A low-pass filter is used to filter out the high-frequency components in the vibration data to prevent high-frequency data from affecting the accuracy of external force identification. At the same time, the trend items with a first-order lateral frequency less than 1 / 2 of the arrow body are filtered out to prevent the rigid body displacement from affecting the identification results.

[0021] In the above-mentioned rocket pulsating pressure load time domain design method, in step 4, the specific method of obtaining the time domain external force spectrum diagram of a single launch of the launch vehicle is:

[0022] The positions of the vibration measurement points for external force identification determined in step 2 and the vibration telemetry time domain data collected in step 3 are used as known quantities of the identification algorithm; the positions and number of the external force application points are determined according to the distribution law of the arterial pressure in step 1, and the positions and number of the external force application points are used as the spatial distribution information of the external force; a multi-point external force identification method is used to reversely identify the external force, and the time domain history of the external force at each external force application point is obtained, thereby forming a multi-point external force for a single flight test of a carrier rocket, that is, a time domain external force spectrum diagram of a single launch of the carrier rocket.

[0023] In the above-mentioned time domain design method for a rocket pulsating pressure load, in the step five, when the carrier rocket is flying, there is a dispersion difference between the atmospheric state and the specific flight profile; the frequency spectrum diagram of the external force identified each time the carrier rocket is launched is enveloped to obtain the time domain curve of the final external force model.

[0024] In the above-mentioned time domain design method for a rocket pulsating pressure load, in step six, based on the time domain curve of the external force model of the launch vehicle in step five, a finite element time domain transient response analysis is performed on the scaled model of the launch vehicle in step one to extract the internal force of the launch vehicle cross section, which is the pulsating pressure load of the rocket.

[0025] The beneficial effects of the present invention compared with the prior art are:

[0026] (1) The present invention combines the characteristics of rockets flying across windy areas quickly, changes the traditional steady-state response analysis method based on full excitation, and refines the calculation of pulsating pressure elastic load by carrying out external force identification and full-rocket time-domain transient response analysis. The elastic load is reduced by 15% to 17%, which has important engineering application and promotion value;

[0027] (2) The present invention obtains a time-domain calculation method for pulsating pressure elastic loads through high-precision dynamic model transient response analysis, thereby achieving effective load reduction on the lateral elastic load of the rocket during flight;

[0028] (3) The present invention arranges vibration measurement points throughout the launch vehicle during flight, so that the spatial characteristics of the external force model can be established in combination with the pulsating pressure wind tunnel test to determine the location and number of the external force action points. The vibration source data selection is then determined based on the modal information of the entire launch vehicle and the arrangement of the vibration measurement points. Finally, the time domain external load reverse identification and multi-shot envelope are performed based on the flight measurement vibration data to obtain the time domain curve of the external force model. Finally, transient response analysis is performed to obtain the pulsating pressure elastic load of the entire launch vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1The present invention is a flow chart of the rocket pulsating pressure load time domain design;

[0030] Figure 2 It is the distribution diagram of arterial pressure of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the embodiments.

[0032] The present invention proposes a time-domain design method for rocket pulsating pressure load. Based on wind tunnel test data, the spatial distribution of pulsating pressure is obtained to form an equivalent external force model of pulsating pressure. Through flight telemetry data, high-precision pulsating pressure external force is reversely identified. Finally, transient response analysis of the full-rocket dynamic model is carried out to calculate the time-domain pulsating pressure load, thereby achieving effective reduction of the rocket's lateral dynamic load during flight.

[0033] Rocket pulsating pressure load time domain design method, such as Figure 1 As shown, the specific steps include:

[0034] Step 1: Conduct wind tunnel tests on a scaled model of a launch vehicle to determine the distribution of arterial pressure. By conducting wind tunnel tests on a scaled model of a launch vehicle, a curve showing the change of the root mean square magnitude of the pulsating pressure with the height of the scaled model of the launch vehicle is obtained.

[0035] like Figure 2 As shown, the distribution law of arterial pressure is:

[0036] The pulsating pressure is concentrated at the places where the shape of the launch vehicle changes, including the interface between the fairing cone and column, the inverted cone of the fairing, and the interface between the booster cone and column; therefore, the pulsating pressure is equivalent to a multi-point concentrated load.

[0037] Step 2: Select external force identification vibration measurement points according to the actual flight conditions of the launch vehicle.

[0038] According to the frequency and mode of the launch vehicle, the energy of the pulsating pressure is concentrated in the low frequency; the low frequency is below 20Hz. Therefore, according to the specific mode of the launch vehicle, the positions with large full-rocket modal displacement in the first few low-frequency modes are selected as the external force identification vibration measurement points, including the satellite-rocket interface, fairing, interstage, and tail section.

[0039] Step 3: After the launch vehicle takes off, the vibration data collected from the external force identification vibration measurement points determined in step 2 are preprocessed to obtain vibration telemetry time domain data.

[0040] The rocket body frequency of the launch vehicle is low frequency, and the high-frequency components in the vibration data affect the accuracy of external force identification.

[0041] The specific method of preprocessing is:

[0042] A low-pass filter is used to filter out the high-frequency components in the vibration data to prevent high-frequency data from affecting the accuracy of external force identification. At the same time, the trend items with a first-order lateral frequency less than 1 / 2 of the arrow body are filtered out to prevent the rigid body displacement from affecting the identification results.

[0043] Step 4: According to the arterial pressure distribution law determined in step 1, the external force identification vibration measurement points determined in step 2, and the vibration telemetry time domain data obtained in step 3, the time domain external force spectrum diagram of a single launch of the launch vehicle is obtained.

[0044] The specific method for obtaining the time domain external force spectrum of a single launch vehicle is:

[0045] The positions of the vibration measurement points for external force identification determined in step 2 and the vibration telemetry time domain data collected in step 3 are used as known quantities of the identification algorithm; the positions and number of the external force application points are determined according to the distribution law of the arterial pressure in step 1, and the positions and number of the external force application points are used as the spatial distribution information of the external force; a multi-point external force identification method is used to reversely identify the external force, and the time domain history of the external force at each external force application point is obtained, thereby forming a multi-point external force for a single flight test of a carrier rocket, that is, a time domain external force spectrum diagram of a single launch of the carrier rocket.

[0046] The formula is:

[0047] Using the mode decomposition method, the vibration telemetry time domain data of the structure can be expressed as:

[0048]

[0049] Where w(x, t) represents the response of the structure, W n (x) represents the nth-order vibration mode of the structure, q n (t) represents the nth-order modal coordinates. The modal coordinates are used to decouple the dynamic differential equations of the structure, and its single-degree-of-freedom control differential equation is expressed as

[0050]

[0051] In the formula q n denote the nth-order modal acceleration, modal velocity and modal displacement, ξ n represents the nth-order modal damping ratio, ω n represents the nth order natural frequency, f n represents the b-th order load. Writing equation (2) in matrix form yields

[0052]

[0053] where C=diag(2ξ1ω1, 2ξ2ω2,…,2ξ n ω n ),

[0054] Assume that the time step is Δt, and the acceleration is i , t i+1 ] changes linearly, and the time integral is calculated by Newmark method, and we can get

[0055] q(t i+1 )=(K * ) -1 f * (t i+1 ) (4)In the formula

[0056]

[0057] (0≤β≤0.5), (0≤γ≤1) are Newmark integration parameters.

[0058] Let A0 = (K * ) -1 , can be rewritten as

[0059]

[0060] At time t+Δt, the modal acceleration and velocity become

[0061]

[0062] In the formula

[0063]

[0064] Combining (9), (13) and (14) yields

[0065]

[0066] According to the recursive relationship, we can get

[0067]

[0068] Assume y(t)∈R m×1 , there is a relationship:

[0069]

[0070] Obviously, the measuring point x s Location i The acceleration response at time is:

[0071] Where W p (x s ) represents the position x of the p-th mode shapes The conversion relationship between physical space and modal space is

[0072]

[0073] Where r represents the number of modes involved in the identification calculation.

[0074]

[0075] Define R = [R d R v R a ], then combining equation (5) and equation (6) we get

[0076]

[0077] The modal load can be expressed as

[0078]

[0079] Where x fi represents the position where the i-th load acts. Therefore, equation (5) can be simplified to

[0080]

[0081] In the formula Therefore, formula (11) can be simplified to

[0082] Y=HF (12)

[0083] In the formula

[0084]

[0085] Then use formula (13) to obtain the value of load F:

[0086] F=(H T H) -1 H T Y (13)

[0087] F is the time domain external force spectrum diagram of a single launch of the launch vehicle.

[0088] Step 5. Repeat steps 3 to 4 m-1 times to obtain the envelope of the time-domain external force spectrum diagram of the launch vehicle m times, that is, the time-domain curve of the external force model of the launch vehicle; m is a positive integer not less than 5.

[0089] When a launch vehicle is flying, there are differences between the atmospheric state and the specific flight profile; the frequency spectrum of the external force identified during each launch of the launch vehicle is enveloped to obtain the time domain curve of the final external force model.

[0090] Step six: According to the time domain curve of the launch vehicle external force model in step five and the scaled model of the launch vehicle in step one, the pulsating pressure load of the rocket is obtained.

[0091] According to the time domain curve of the launch vehicle external force model in step five, a finite element time domain transient response analysis is carried out on the scaled model of the launch vehicle in step one to extract the internal force of the launch vehicle cross section, which is the pulsating pressure load of the rocket.

[0092] The present invention combines the characteristics of the rocket quickly crossing the windy flight zone, changes the traditional steady-state response analysis method based on full excitation, and through the external force identification and the whole arrow time domain transient response analysis, refines the calculation of the pulsating pressure elastic load, and reduces the elastic load by 15% to 17%, which has important engineering application and promotion value.

[0093] The present invention obtains a time-domain calculation method for pulsating pressure elastic loads through transient response analysis of a high-precision dynamic model, thereby achieving effective load reduction on the lateral elastic load of a rocket during flight.

[0094] The present invention arranges vibration measuring points throughout the entire rocket during flight, so that the spatial characteristics of the external force model can be established in combination with the pulsating pressure wind tunnel test, and the positions and number of external force application points can be determined. The vibration source data selection is then determined based on the modal information of the entire rocket and the arrangement of the vibration measuring points. Finally, the time domain external load reverse identification and multi-shot envelope are performed based on the flight measured vibration data to obtain the time domain curve of the external force model. Finally, transient response analysis is carried out to obtain the pulsating pressure elastic load of the entire rocket.

[0095] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A rocket pulsating pressure load time domain design method, characterized by: include: Step 1: Conduct wind tunnel tests on a scaled model of the launch vehicle to determine the distribution of arterial pressure; Step 2: Select external force identification vibration measurement points according to the actual flight conditions of the launch vehicle; Step 3: After the launch vehicle flies, the vibration data collected from the external force identification vibration measurement points determined in step 2 are preprocessed to obtain vibration telemetry time domain data; Step 4: Obtain a time-domain external force spectrum diagram of a single launch of the launch vehicle according to the arterial pressure distribution law determined in step 1, the external force identification vibration measurement points determined in step 2, and the vibration telemetry time-domain data obtained in step 3; Step 5, repeat step 3 to step 4 m-1 times to obtain the envelope of the time domain external force spectrum diagram of the launch vehicle m times, that is, the time domain curve of the launch vehicle external force model; m is a positive integer not less than 5; Step six: According to the time domain curve of the launch vehicle external force model in step five and the scaled model of the launch vehicle in step one, the pulsating pressure load of the rocket is obtained.

2. A rocket pulsating pressure load time domain design method according to claim 1, characterized in that: In the step 1, a wind tunnel test is performed on a scaled model of a launch vehicle to obtain a curve showing a change in the root mean square magnitude of the pulsating pressure with the height of the scaled model of the launch vehicle.

3. A rocket pulsating pressure load time domain design method according to claim 2, characterized in that: The distribution law of arterial pressure is: The pulsating pressure is concentrated at the places where the shape of the launch vehicle changes, including the interface between the fairing cone and column, the inverted cone of the fairing, and the interface between the booster cone and column; therefore, the pulsating pressure is equivalent to a multi-point concentrated load.

4. The rocket pulsating pressure load time domain design method according to claim 1, characterized in that: In the step 2, according to the frequency and mode of the launch vehicle, the energy of the pulsating pressure is concentrated in the low frequency; the low frequency is below 20 Hz.

5. A rocket pulsating pressure load time domain design method according to claim 4, characterized in that: According to the specific modes of the launch vehicle, the positions with large full-rocket modal displacement in the first few low-frequency modes are selected as the vibration measurement points for external force identification, including the satellite-rocket interface, fairing, interstage, and tail section.

6. The rocket pulsating pressure load time domain design method according to claim 1, characterized in that: In the step three, the rocket body frequency of the carrier rocket is low frequency, and the high-frequency component in the vibration data affects the accuracy of external force identification.

7. A rocket pulsating pressure load time domain design method according to claim 6, characterized in that: The specific method of the pretreatment is: A low-pass filter is used to filter out the high-frequency components in the vibration data to prevent high-frequency data from affecting the accuracy of external force identification. At the same time, the trend items with a first-order lateral frequency less than 1 / 2 of the arrow body are filtered out to prevent the rigid body displacement from affecting the identification results.

8. The rocket pulsating pressure load time domain design method according to claim 1, characterized in that: In step 4, the specific method for obtaining the time domain external force spectrum diagram of a single launch of the launch vehicle is: The positions of the vibration measurement points for external force identification determined in step 2 and the vibration telemetry time domain data collected in step 3 are used as known quantities of the identification algorithm; the positions and number of the external force application points are determined according to the distribution law of the arterial pressure in step 1, and the positions and number of the external force application points are used as the spatial distribution information of the external force; a multi-point external force identification method is used to reversely identify the external force, and the time domain history of the external force at each external force application point is obtained, thereby forming a multi-point external force for a single flight test of a carrier rocket, that is, a time domain external force spectrum diagram of a single launch of the carrier rocket.

9. The rocket pulsating pressure load time domain design method according to claim 1, characterized in that: In the step 5, when the carrier rocket is flying, there are dispersion differences between the atmospheric state and the specific flight profile; the frequency spectrum of the external force identified each time the carrier rocket is launched is enveloped to obtain the time domain curve of the final external force model.

10. The rocket pulsating pressure load time domain design method according to claim 1, characterized in that: In the step six, based on the time domain curve of the launch vehicle external force model in step five, a finite element time domain transient response analysis is performed on the scaled model of the launch vehicle in step one to extract the internal force of the launch vehicle cross section, which is the pulsating pressure load of the rocket.

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