Random vibration test condition prediction method for instrument and equipment in second stage cabin of launch vehicle

Abstract

The application provides a launch vehicle second stage cabin section instrument equipment random vibration test condition prediction method: according to the time domain vibration response of the gimbal on the engine during the ground test of the newly researched launch vehicle second stage engine, the random vibration power spectral density at the position of the newly researched launch vehicle second stage cabin section instrument equipment is predicted and recorded as a first random vibration power spectral density; according to the total sound pressure level of the external noise at the position of the newly researched launch vehicle second stage cabin section, the random vibration power spectral density at the position of the newly researched launch vehicle second stage cabin section instrument equipment is predicted and recorded as a second random vibration power spectral density; the maximum envelope curve of the first random vibration power spectral density and the second random vibration power spectral density is drawn, a certain margin is considered, the envelope curve is converted into a broken line segment, and the second stage cabin section instrument equipment acceptance level random vibration test condition is obtained.

Description

Technical Field

[0001] This invention relates to the field of launch vehicles, and more specifically to a method for predicting random vibration test conditions for instruments and equipment in the second stage section of a launch vehicle. Background Technology

[0002] The random vibration environment experienced by the instruments and equipment in the second-stage section of a launch vehicle during the launch drive phase primarily originates from the transmission of thrust pulsations along the structure during the stable operation phase of the second-stage engine and the local response to noise. Damage or failure of onboard instruments and equipment is closely related to the high-frequency random vibration environment they endure. The accuracy of test conditions directly affects the design level of the product and the effectiveness of ground tests, thus influencing the quality of the instruments and equipment. This is one of the key factors determining the success or failure of the rocket flight.

[0003] Existing methods for designing random vibration test conditions primarily rely on measured environmental data. With a large amount of available measured environmental data, statistical methods are used to analyze this data and apply appropriate envelopes to formulate corresponding test conditions. However, a large amount of measured environmental data is only available after rocket production and multiple flight tests, while test conditions are always required before rocket design to verify the environmental adaptability of instruments and equipment. Therefore, to meet the needs of new rocket design, test conditions must be completed under conditions lacking measured environmental data for the new rocket; the required environment can only be solved through simulation. Finite element analysis is commonly used for simulation, but the analysis model needs thorough verification to ensure the validity of the calculations. Furthermore, simulation simulation requires significant time and effort, causing considerable inconvenience for the rapid demonstration of new rocket designs. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a method for predicting random vibration test conditions for instruments and equipment in the second stage of a launch vehicle. This method can quickly provide random vibration test conditions for instruments and equipment in the second stage of a launch vehicle during the initial stages of the demonstration and design process, so as to facilitate the selection of instruments and equipment and the design of the program.

[0005] The solution provided by this invention is a method for predicting random vibration test conditions for instruments and equipment in the second stage section of a launch vehicle, which includes the following steps:

[0006] Based on the time-domain vibration response at the constant level seat of the engine during the ground test of the second stage engine of the newly developed carrier rocket, the random vibration power spectral density of the instrument and equipment section of the second stage of the newly developed carrier rocket is predicted and denoted as the first random vibration power spectral density.

[0007] Based on the total external noise sound pressure level at the second stage section of the newly developed carrier rocket, the random vibration power spectral density at the instrument and equipment location of the second stage section of the newly developed carrier rocket is predicted and denoted as the second random vibration power spectral density.

[0008] Plot the maximum envelope curves of the first and second random vibration power spectral densities, and considering a certain margin, convert the envelope curves into broken line segments to obtain the random vibration test conditions for the acceptance level of instruments and equipment in the second-stage module.

[0009] Preferably, the first random vibration power spectral density is obtained by the following method:

[0010] During the ground test of the second-stage engine of the newly developed carrier rocket, vibration sensors were placed at the constant level seat to collect vibration data and obtain the time-domain vibration response at the constant level seat of the engine during the ground test of the second-stage engine of the newly developed carrier rocket.

[0011] The time-domain vibration response at the constant level seat of the second stage engine of the newly developed launch vehicle was converted into frequency-domain data by selecting the data of the steady operating segment, and then bandpass filtered. After filtering, the power spectral density was calculated to obtain the power spectral density of the vibration response at the constant level seat of the second stage engine of the newly developed launch vehicle.

[0012] Based on the power spectral density at the constant level seat of the engine of the second stage of the newly developed launch vehicle, and according to the decay law of the power spectral density of random vibration in the compartment, the power spectral density of random vibration at the instrument and equipment section of the second stage of the newly developed launch vehicle is predicted, and is denoted as the first random vibration power spectral density.

[0013] Preferably, the sampling rate for acquiring vibration data is higher than 50 kHz.

[0014] Preferably, the stable operating section refers to the engine operating section other than the transient conditions of ignition and shutdown.

[0015] Preferably, the bandpass filter frequency band is 20–2000 Hz.

[0016] Preferably, the power spectral density at the normal level seat of the second-stage engine is multiplied by the attenuation coefficient to obtain the power spectral density of random vibrations at the instrumentation and equipment of the second-stage section.

[0017] Preferably, the second random vibration power spectral density is obtained by the following method:

[0018] The total sound pressure level of the external noise of the newly developed launch vehicle is compared with that of the second stage of the existing launch vehicle. The difference in random vibration power spectral density between the two is calculated. Based on the random vibration power spectral density of the second stage of the existing launch vehicle, the difference in random vibration power spectral density between the two is multiplied to obtain the random vibration power spectral density of the instrument and equipment in the second stage of the newly developed launch vehicle, which is denoted as the second random vibration power spectral density.

[0019] Preferably, the random vibration power spectral density of the newly developed launch vehicle differs from that of the second-stage module of the existing launch vehicle by a factor of: Wherein, Δ is the difference between the total sound pressure level of the external noise of the newly developed launch vehicle and the total sound pressure level of the external noise of the existing launch vehicle.

[0020] Preferably, the method for predicting random vibration test conditions for instruments and equipment in the second stage of a launch vehicle further includes the following steps:

[0021] The power spectral density of the acceptance-level random vibration test is multiplied by a preset safety factor to serve as the qualification-level random vibration test conditions.

[0022] Preferably, the safety factor is greater than 2.

[0023] The advantages of this invention compared to the prior art are:

[0024] (1) This invention takes into account the main sources of vibration in the second stage of the launch vehicle. It evaluates the random vibration power spectral density of the instruments and equipment in the second stage from two perspectives: the time-domain vibration response at the engine's normal seat and the total external noise sound pressure level at the stage. The evaluation is comprehensive and accurate.

[0025] (2) The invention innovatively utilizes the external noise of the newly developed section measured during engine testing, combined with telemetry data of existing launch vehicle models, to quickly predict the random vibration test conditions of instruments and equipment in the newly developed launch vehicle model section without the need for testing and simulation.

[0026] (3) Using statistical analysis, the power spectral density at the normal level seat of the second stage engine of the newly developed launch vehicle is multiplied by the attenuation coefficient to predict the random vibration power spectral density at the instrument and equipment section of the second stage of the newly developed launch vehicle. Similarly, no test or simulation is required, and rapid calculation can be achieved.

[0027] (4) Compared with the past, which only referred to the results of multiple flight tests and finite element analysis methods, this invention can quickly provide random vibration test conditions for the instruments and equipment of the second stage in the early stage of launch vehicle demonstration and scheme design, so as to provide reference for instrument and equipment selection and scheme design, and shorten the development cycle of the new launch vehicle model.

[0028] (5) The random vibration test condition prediction method for the instrument and equipment of the second stage of a launch vehicle provided by the present invention has been successfully applied to the development of a new generation of liquid and solid-liquid bundled rockets. With the successful completion of the flight test and the comparison of telemetry data, it is shown that the method has high accuracy. Attached Figure Description

[0029] The present invention provides a method for designing random vibration test conditions for instruments and equipment in the second stage section of a launch vehicle, as illustrated in the following embodiments and figures.

[0030] Figure 1This is the time-domain vibration response curve at the constant level seat of the second stage engine in Embodiment 2 of the present invention;

[0031] Figure 2 This is the vibration response power spectral density of the stable operating section at the constant level seat of the stage engine in Embodiment 2 of the present invention;

[0032] Figure 3 This is the power spectral density of the random vibrations at the instrumentation and equipment of the second-stage section caused by the second-stage engine in an embodiment of the present invention;

[0033] Figure 4 This is the power spectral density of random vibrations at the instrumentation and equipment locations in the second-stage module caused by noise, according to an embodiment of the present invention.

[0034] Figure 5 These are the random vibration test conditions for the acceptance level of instruments and equipment in the second-stage sub-sections after the envelope in this embodiment of the invention. Detailed Implementation

[0035] The present invention will be further described below with reference to the embodiments.

[0036] Environmental prediction is a gradual process. During the design phase, it is necessary to rely on the measured data and statistical patterns of past successful models, and to conduct preliminary and rapid environmental design in combination with the specific circumstances of the new rocket.

[0037] The purpose of this invention is to provide a method for designing random vibration test conditions for instruments and equipment in the second stage of a launch vehicle, which can quickly formulate random vibration test conditions for instruments and equipment in the second stage according to the method of this invention.

[0038] Example:

[0039] The following will combine Figures 1-5 The present invention provides a further detailed description of a method for designing random vibration test conditions for instruments and equipment in the second stage section of a launch vehicle.

[0040] The present invention provides a method for designing random vibration test conditions for instruments and equipment in a second-stage section of a launch vehicle, comprising the following steps:

[0041] S1. Obtain the time-domain vibration response at the constant level seat of the engine during the ground test of the second stage engine of the newly developed carrier rocket;

[0042] The specific implementation steps are as follows: During the ground test of the second-stage engine of the newly developed launch vehicle, vibration sensors are placed at the constant-level seat to collect vibration data. The sampling rate is required to be higher than 50 kHz to obtain the time-domain vibration response at the constant-level seat of the engine during the ground test. In this embodiment, based on the engine ground test, the obtained time-domain curve of the vibration response at the constant-level seat of the engine is as follows: Figure 1 As shown.

[0043] S2. Select the data of the steady working segment of the time-domain vibration response at the constant level seat of the second stage engine of the newly developed launch vehicle, convert it into frequency domain data, perform bandpass filtering, and then calculate the power spectral density of the vibration response at the constant level seat of the second stage engine of the newly developed launch vehicle.

[0044] The specific implementation steps are as follows: a. Extract Figure 1 The first part of the data is a segment of time-domain data from the steady-state operating period of the vibration response at the constant level seat of the engine, such as the time-domain data from 200 to 205 s in this embodiment. The second part is a bandpass filter of 20–2000 Hz applied to the extracted 200–205 s steady-state operating period time-domain data, and the power spectral density is calculated on the filtered data. The method for calculating the power spectral density is detailed in Appendix K of “GJB 2238A_2004 Telemetry Data Processing”, and the calculation results are as follows. Figure 2 As shown. The stable operating section refers to the engine operating section other than transient conditions such as ignition and shutdown.

[0045] S3. Based on the power spectral density at the constant level seat of the second stage engine of the newly developed launch vehicle, the power spectral density at the instrument and equipment section of the second stage of the newly developed launch vehicle is predicted according to the attenuation law of the power spectral density of random vibration in the section, and is denoted as the first random vibration power spectral density.

[0046] The specific implementation steps are as follows: The power spectral density at the stage 2 engine's normal operating position is multiplied by an attenuation coefficient to obtain the power spectral density of random vibrations at the stage 2 instrumentation equipment location. In this embodiment, the power spectral density of high-frequency random vibrations from the stage 2 engine's normal operating position to the stage 2 instrumentation equipment location is attenuated to 5%. Based on the obtained power spectral density at the stage 2 engine's normal operating position, the power spectral density is multiplied by a 5% attenuation coefficient to obtain the power spectral density of random vibrations at the stage 2 instrumentation equipment location. The calculation results are as follows: Figure 3 As shown.

[0047] S4. Obtain the total external noise sound pressure level at the second stage section of the newly developed carrier rocket based on ground test or simulation calculations;

[0048] The specific implementation steps are as follows: During the ground test of the second-stage engine of the newly developed carrier rocket, noise sensors are installed at the location of the second-stage section of the newly developed carrier rocket, with a sampling rate required to be higher than 50KHz, to obtain the total sound pressure level of the external noise at the corresponding location.

[0049] S5. Compare the total sound pressure level of the external noise of the newly developed launch vehicle with that of the existing launch vehicle's second stage section, calculate the difference in random vibration power spectral density between the two, and obtain the random vibration power spectral density at the instrument and equipment location of the newly developed launch vehicle's second stage section by multiplying the random vibration power spectral density of the existing launch vehicle's second stage section by the difference in random vibration power spectral density between the two. This random vibration power spectral density is denoted as the second random vibration power spectral density.

[0050] The specific implementation steps are as follows: Compare the total sound pressure level of the external noise of the newly developed launch vehicle and the second stage section of the existing launch vehicle, and calculate the difference in power spectral density. The difference in random vibration power spectral density between the newly developed launch vehicle and the second stage section of the existing launch vehicle is: Wherein, Δ represents the difference between the total sound pressure level of the newly developed launch vehicle and the total sound pressure level of the existing launch vehicle. In this embodiment, the power spectral density difference factor converted from the difference in external noise levels is shown in Table 1.

[0051] Table 1. Power spectral density difference calculated from the difference in external noise levels.

[0052] launch vehicle Total external noise sound pressure level Newly developed launch vehicle 143dB Current launch vehicles 141dB noise difference 2dB Power spectral density phase difference factor (10^(2 / 20))^2＝1.58

[0053] Based on telemetry data from existing launch vehicle models, the random vibration power spectral density of the second-stage module can be obtained. Multiplying this by the difference in random vibration power spectral density between the two models predicts the random vibration power spectral density at the instrumentation location of the second-stage module in the newly developed launch vehicle. The calculation results are as follows: Figure 4 As shown.

[0054] This innovative method utilizes external noise measurements of the newly developed module during engine testing, combined with telemetry data from existing launch vehicle models, to quickly predict the random vibration test conditions for instruments and equipment in the newly developed launch vehicle module.

[0055] S6. Plot the maximum envelope curves of the first and second random vibration power spectral densities, and considering a certain margin, convert the envelope curves into broken line segments to obtain the random vibration test conditions for the acceptance level of instruments and equipment in the second-stage module.

[0056] The specific implementation steps are as follows: Envelope the power spectral density of the random vibrations at the instrumentation and equipment locations in the second-stage stage during the stable operating phase of the second-stage engine and based on noise prediction. Considering a certain engineering margin, the envelope curve is converted into a broken line segment, such as... Figure 5 As shown in Table 2, these are the random vibration acceptance test conditions for the instruments and equipment of the second stage of the launch vehicle. The acceptance test time is specified as 60 seconds.

[0057] Table 2 Random Vibration Acceptance Test Conditions for Instruments and Equipment in Sub-Class Sections

[0058]

[0059] S7. Take the power spectral density multiplied by the safety factor as the random vibration test conditions for the acceptance level, and use it as the random vibration test conditions for the qualification level.

[0060] In this embodiment, the power spectral density is multiplied by a safety factor of 2 as the qualification-level random vibration test condition, and the qualification-level test time is specified as 120s. The specific implementation steps are as follows: multiply the acceptance-level test level in Table 1 by 2 to obtain the qualification-level test level, and specify the qualification-level test time as 120s. Thus, the random vibration test conditions for the instruments and equipment of the second-stage module are obtained, as shown in Table 3.

[0061] Table 3 Random Vibration Test Conditions for Instruments and Equipment in the Second-Level Module

[0062]

[0063] The present invention provides a method for predicting random vibration test conditions for instruments and equipment in the second stage of a launch vehicle, which can quickly provide random vibration test conditions for instruments and equipment in the second stage of a new rocket, thus solving the problem that it is difficult to design random vibration conditions for instruments and equipment in the second stage of a new rocket during the feasibility study phase.

[0064] This invention discloses a method for designing random vibration test conditions for instruments and equipment in the second stage of a launch vehicle. This method has been successfully applied to the development of a new generation of liquid-fueled and solid-liquid coupled rockets, ensuring the sufficiency and accuracy of random vibration testing of onboard instruments and equipment. The new generation of liquid-fueled and solid-liquid coupled rockets successfully completed flight tests, and the flight results demonstrate that the established random vibration test conditions can effectively reflect flight telemetry results. This invention's method has been applied to the development of subsequent models of the new generation of rockets.

[0065] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for predicting random vibration test conditions for instruments and equipment in the second stage section of a launch vehicle, characterized in that... Includes the following steps: Based on the time-domain vibration response at the constant level seat of the engine during the ground test of the second stage engine of the newly developed carrier rocket, the random vibration power spectral density of the instrument and equipment section of the second stage of the newly developed carrier rocket is predicted and denoted as the first random vibration power spectral density. Based on the total external noise sound pressure level at the second stage section of the newly developed carrier rocket, the random vibration power spectral density at the instrument and equipment location of the second stage section of the newly developed carrier rocket is predicted and denoted as the second random vibration power spectral density. Plot the maximum envelope curves of the first and second random vibration power spectral densities, and considering a certain margin, convert the envelope curves into broken line segments to obtain the random vibration test conditions for the acceptance level of instruments and equipment in the second-stage module. The first random vibrational power spectral density is obtained by the following method: During the ground test of the second-stage engine of the newly developed carrier rocket, vibration sensors were placed at the constant level seat to collect vibration data and obtain the time-domain vibration response at the constant level seat of the engine during the ground test of the second-stage engine of the newly developed carrier rocket. The time-domain vibration response at the constant level seat of the second stage engine of the newly developed launch vehicle was converted into frequency-domain data by selecting the data of the steady operating segment, and then bandpass filtered. After filtering, the power spectral density was calculated to obtain the power spectral density of the vibration response at the constant level seat of the second stage engine of the newly developed launch vehicle. Based on the power spectral density at the constant level seat of the second stage engine of the newly developed launch vehicle, the power spectral density at the instrument and equipment section of the second stage of the newly developed launch vehicle is predicted according to the attenuation law of the power spectral density of random vibration in the section, and is denoted as the first random vibration power spectral density. The power spectral density at the normal level seat of the second-stage engine is multiplied by the attenuation coefficient to obtain the power spectral density of random vibrations at the instrument and equipment of the second-stage section. The second random vibration power spectral density is obtained by the following method: The total sound pressure level of the external noise of the newly developed launch vehicle is compared with that of the second stage of the existing launch vehicle. The difference in random vibration power spectral density between the two is calculated. Based on the random vibration power spectral density of the second stage of the existing launch vehicle, the random vibration power spectral density of the instrument and equipment in the second stage of the newly developed launch vehicle is obtained by multiplying it by the difference in random vibration power spectral density between the two. This is denoted as the second random vibration power spectral density. The power spectral density of random vibration in the second-stage section of the newly developed launch vehicle differs from that of the existing launch vehicle by a factor of: ,in, This represents the difference between the total sound pressure level of the external noise of the newly developed launch vehicle and the total sound pressure level of the external noise of the currently in service launch vehicle.

2. The method for predicting random vibration test conditions for instruments and equipment in the second stage section of a launch vehicle according to claim 1, characterized in that... The sampling rate for vibration data acquisition is higher than 50 kHz.

3. The method for predicting random vibration test conditions for instruments and equipment in the second stage section of a launch vehicle according to claim 1, characterized in that... The stable operating section refers to the engine operating section other than the transient conditions of ignition and shutdown.

4. The method for predicting random vibration test conditions for instruments and equipment in the second stage section of a launch vehicle according to claim 1, characterized in that... The bandpass filter operates in the frequency range of 20~2000Hz.

5. The method for predicting random vibration test conditions for instruments and equipment in the second stage section of a launch vehicle according to claim 1, characterized in that... It also includes the following steps: The power spectral density of the acceptance-level random vibration test is multiplied by a preset safety factor to serve as the qualification-level random vibration test conditions.

6. The method for predicting random vibration test conditions for instruments and equipment in the second stage section of a launch vehicle according to claim 5, characterized in that... The safety factor is greater than 2.

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