A method and apparatus for determining the influencing factor of engine jet sound efficiency

Abstract

This invention discloses a method and apparatus for determining the influence factor of engine jet acoustic efficiency, including: calculating the total mechanical power of the engine; arranging a certain number of sound pressure level measuring points during engine testing, and performing sound pressure level measurement and total sound power calculation at each measuring point based on the engine test; determining the acoustic efficiency influence factor for each measuring point based on the ratio of the total sound power to the total mechanical power of the engine; and taking the average of multiple acoustic efficiency influence factors as the acoustic efficiency influence factor for this engine. This method for determining the influence factor of engine jet acoustic efficiency can determine the jet acoustic efficiency influence factor for various types of engines, providing support for the subsequent accurate application of jet noise engineering prediction methods and rapid prediction of jet noise in new engine models.

Description

Technical Field

[0001] This invention belongs to the field of launch vehicles and relates to a method and apparatus for determining the influence factor of engine jet acoustic efficiency. Background Technology

[0002] During launch vehicle ignition and takeoff, the exhaust noise from the engine and the noise reflected from the ground affect the rocket structure, creating a unique jet noise environment. Takeoff jet noise exhibits a degree of randomness, with a sound pressure frequency band ranging from 10Hz to 20kHz. This noise creates a mid-to-high frequency dynamic environment for the rocket structure and payload, resulting in a response frequency range from 20Hz to 2000Hz. In severe cases, it can cause structural damage or equipment malfunction, leading to mission failure. Therefore, predicting the jet noise environment is a crucial basis for establishing rocket noise environment test conditions.

[0003] Accurate simulation and prediction of rocket engine jet noise requires computational fluid dynamics (CFD). This involves establishing a complete flow field and rocket structure model, calculating the pressure on the structural surfaces, and then converting the pressure to obtain the noise pressure level spectrum caused by the engine jet noise on different structural surfaces. However, CFD is computationally expensive, especially for calculations involving complex flow fields such as rocket structures and guide channels. The efficiency of CFD is unacceptable for engineering purposes, and its accuracy cannot be guaranteed. Therefore, engineering prediction methods are a more feasible approach for predicting rocket jet noise.

[0004] Based on engine noise theory and observations of extensive historical test data, NASA has developed an environmental engineering prediction method for predicting engine jet noise. This method considers the influence of various parameters on jet noise, including: the number of engines, distance from the engine nozzle, angle to the jet direction, nozzle geometry, jet velocity, and thrust. Therefore, it has considerable practical value for engineering applications. Calculating the total power of the jet noise is the first step in predicting jet noise. For large rockets, the total power of the engine jet noise can be estimated using the engine's total mechanical power using the following formula.

[0005]

[0006] in It is the thrust of the rocket engine; It is the velocity of the exhaust jet at the engine outlet; It is a factor affecting acoustic efficiency.

[0007] The acoustic efficiency factor is the ratio of the engine's total acoustic power to its total mechanical power. When calculating the total acoustic power level of the jet noise using the above formula, the total mechanical power of the rocket engine needs to be multiplied by the acoustic coefficient to determine the engine's total acoustic power. NASA has derived the relationship between the total jet acoustic power level and engine power based on extensive rocket engine test data. A conservative estimate for the acoustic coefficient is 0.5% for typical liquid rocket engines, with an upper limit of 1%. Because the selection of the acoustic efficiency factor is highly empirical, it needs to be continuously improved in practice based on experimental data.

[0008] While engineering-based prediction methods involve minimal computation and have a clear approach, many parameters are selected based on experience, and current literature primarily uses empirical parameters from foreign engines. Therefore, determining a method for obtaining jet noise efficiency influencing factors, and acquiring relevant empirical parameters based on domestic engines, is crucial for better applying rapid engineering-based prediction methods to the prediction of jet noise environments for various types of rockets in my country. Summary of the Invention

[0009] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a method and device for determining the influence factor of engine jet sound efficiency, which is used to determine the influence factor of jet sound efficiency of various types of engines, so as to facilitate the accurate application of subsequent jet noise engineering prediction methods.

[0010] The solution of this invention is: a method for determining the influencing factor of engine jet sound efficiency, comprising the following steps:

[0011] Step 1: Obtain the total mechanical power of the engine ;

[0012] Step 2: During engine testing, set up N sound pressure level measuring points. The distance between the measuring points and the engine nozzle should be greater than a preset distance. Record the distance between each measuring point and the engine nozzle. The sound pressure level at each measuring point was measured. ,in i Indicates the first i One measurement point;

[0013] Step 3, according to , Calculate the sound power spectrum at each measuring point;

[0014] Step 4: Calculate the total sound power corresponding to each measuring point based on the sound power spectrum of each measuring point;

[0015] Step 5: Based on the total acoustic power and total mechanical power corresponding to each measuring point Calculate the acoustic efficiency influence factor for each measuring point to obtain N acoustic efficiency influence factors.

[0016] Step 6: Take the average value of the N sound efficiency influencing factors and use it as the engine jet sound efficiency influencing factor.

[0017] Furthermore, step 1, obtaining the total mechanical power of the engine, includes:

[0018]

[0019] in, It is the total mechanical power of the engine. It is the thrust of the engine; It is the velocity of the jet stream at the engine exit.

[0020] Furthermore, when the engine is a solid rocket motor and the influence of solid particles is considered, the thrust of the engine containing particle effects can be calculated by adding a jet particle phase at the combustion chamber inlet. Engine outlet jet velocity and obtain the total mechanical power of the engine. .

[0021] Furthermore, in step 2, the number of sound pressure level measurement points N set up during engine testing is ≥ 2.

[0022] Furthermore, the sound pressure level measurement point in step 2 is a point sound source propagation point.

[0023] Furthermore, step 3 involves calculating the sound power spectrum at each measuring point, determined according to the following formula:

[0024]

[0025] in, Indicates the first i The sound power spectrum at each measuring point.

[0026] Furthermore, step 5 involves calculating the acoustic efficiency influence factor for each measuring point, determined according to the following formula:

[0027]

[0028] in, Indicates the first i The acoustic efficiency influence factor corresponding to each measuring point.

[0029] Furthermore, a device for determining the influence factor of engine jet sound efficiency is provided, comprising:

[0030] Engine total mechanical power acquisition module: used to obtain the engine's thrust. Engine outlet jet velocity Obtain the total mechanical power of the engine ;

[0031] Sound power spectrum acquisition module: used to determine the distance from the engine nozzle of each of the N sound pressure level measurement points set up during engine testing. and the sound pressure level measured at each measuring point. Obtain the sound power spectrum at each measuring point. ;in i Indicates the first i There are 2 measurement points, N≥2, and the sound pressure level measurement points are point sound source propagation points;

[0032] Total sound power acquisition module: used to obtain the sound power spectrum of each measuring point. Obtain the total sound power corresponding to each measuring point ;

[0033] The sound efficiency influencing factor acquisition module is used to obtain the total sound power at each measurement point. Total mechanical power of the engine Calculate the acoustic efficiency influence factor for each measuring point. ;

[0034] The module for averaging the sound efficiency influence factors is used to obtain the sound efficiency influence factors of the engine jet.

[0035] Furthermore, the engine total mechanical power acquisition module: based on Obtain the total mechanical power of the engine ;

[0036] Sound power spectrum acquisition module: based on Obtain the sound power spectrum at each measuring point;

[0037] Acquisition module for sound efficiency influencing factor: based on Obtain the acoustic efficiency influence factor for each measuring point.

[0038] The advantages of this invention compared to the prior art are:

[0039] This invention presents a process for obtaining the jet acoustic efficiency influencing factor of an engine. By designing multiple sound pressure level measurement points for approximate point source propagation during engine testing, and utilizing the measured distance parameters and sound pressure levels, a calculation formula for the sound power spectrum is derived. This allows for the direct calculation of the total sound power and acoustic efficiency influencing factor corresponding to each measurement point. This overcomes the shortcomings of relying heavily on empirical methods in selecting the acoustic efficiency influencing factor and the lack of domestic engine parameters. It can be used to determine the jet acoustic efficiency influencing factor for various types of engines, improving the accuracy of jet noise engineering predictions. Attached Figure Description

[0040] Figure 1 This is a flowchart of the method for determining the influence factor of engine jet sound efficiency according to an embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of the sound pressure measurement points during engine testing according to an embodiment of the present invention;

[0042] Figure 3 The flow field distribution characteristics during solid rocket motor test runs according to an embodiment of the present invention;

[0043] Figure 4 This is a schematic diagram of the sound pressure measurement points during the test run of a solid rocket motor, taking into account the influence of solid particles, as an embodiment of the present invention. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0045] Example 1

[0046] like Figure 1 As shown, for various types of engines, the method for determining the engine jet sound efficiency influencing factor according to the present invention includes the following steps:

[0047] Step 1: Obtain the total mechanical power of the engine, including the engine thrust and the engine exhaust velocity. ,in It is the thrust of the rocket engine; This refers to the engine exit jet velocity. This embodiment uses a specific engine as an example, and the specific implementation steps are as follows: Based on the engine performance parameters, the engine thrust is obtained as 1200000N and the exit jet velocity as 2942 m / s. The calculation... .

[0048] Step 2: During engine testing, set up a certain number of sound pressure level measuring points and record the distance of each measuring point from the engine nozzle 3. The sound pressure level at each measuring point was measured. The specific implementation steps are as follows: During engine testing, two measuring points are set up, considering that the measuring points are as far away from the engine nozzle 3 as possible to form a point sound source propagation effect. The two measuring points are set up as follows: Figure 2 As shown. The distance between measuring point 1 and engine nozzle 3. The distance between measuring point 2 and engine nozzle 3 The total sound pressure level at measuring point 1 was measured during engine testing. The total sound pressure level at measuring point 2 was measured. .

[0049] Step 3, according to Calculate the sound power spectrum at each measuring point. The specific implementation steps are as follows: Based on... , Calculations yielded .according to , Calculations yielded .

[0050] Step 4: Calculate the total sound power at each measuring point based on the sound power spectrum. The specific implementation steps are as follows: Based on... Calculations yielded .according to Calculations yielded .

[0051] Step 5, according to Calculate the acoustic efficiency influence factor for each measuring point. The specific implementation steps are as follows: Based on... , Calculations yielded .according to , Calculations yielded .

[0052] Step 6: Take the average of the multiple sound efficiency influence factors obtained in Step 5, and use this average as the sound efficiency influence factor for this engine. The specific implementation steps are as follows: [The text then repeats the steps for step 5, which is redundant and can be omitted.] and Take the average, and get In this example, the sound efficiency influence factor of the engine is 4.44159E-05.

[0053] Example 2

[0054] For solid-propellant engines that consider the influence of solid particles, a method for determining the engine jet acoustic efficiency influence factor is provided, including the following steps:

[0055] Step 1: Obtain the solid rocket motor thrust considering the influence of solid particles through simulation. and the outlet jet velocity Calculate the total mechanical power of the solid rocket motor. ,in It is the thrust of a solid rocket motor; This refers to the exit jet velocity of a solid rocket motor. The specific implementation steps are as follows: During the jet calculation process, based on the particle distribution characteristics, a particulate phase is added to the combustion chamber inlet to calculate the exit jet velocity distribution and thrust, which include the influence of particles. The flow field distribution characteristics of a certain solid rocket motor considering solid particles are as follows: Figure 3 As shown. The calculated exit jet velocity is 2500 m / s, and the engine thrust is 1267000 N. .

[0056] Step 2: During the solid rocket motor test run, set up a certain number of sound pressure level measuring points and record the distance of each measuring point from the engine nozzle. The sound pressure level at each measuring point was measured. The specific implementation steps are as follows: During the solid rocket motor test run, two measuring points are set up. Considering that the measuring points are as far away from the engine nozzle as possible to create a point source propagation effect, the two measuring points are arranged as follows: Figure 4 As shown. Measurement point 1 is at a distance from the engine nozzle. Measuring point 2 is at a distance from the engine nozzle. The total sound pressure level at measuring point 1 was measured during engine testing. The total sound pressure level at measuring point 2 was measured. .

[0057] Step 3, according to Calculate the sound power spectrum at each measuring point. The specific implementation steps are as follows: Based on... , Calculations yielded .according to , Calculations yielded .

[0058] Step 4: Calculate the total sound power at each measuring point based on the sound power spectrum. The specific implementation steps are as follows: Based on... Calculations yielded .according to Calculations yielded .

[0059] Step 5, according to Calculate the acoustic efficiency coefficient for each measuring point. The specific implementation steps are as follows: Based on... , Calculations yielded .according to , Calculations yielded .

[0060] Step 6: Take the average of the multiple sound efficiency coefficients obtained in Step 5, and use this average as the sound efficiency coefficient of the engine. The specific implementation steps are as follows: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] and Take the average, and get In this example, the sound efficiency coefficient of the engine is 6.25E-04.

[0061] The method for determining the influence factor of engine jet noise efficiency, as proposed in this invention, has been successfully applied in the development of new-generation liquid rockets and solid-liquid coupled rockets, providing accurate empirical parameters for the engineering prediction of jet noise. The error between the predicted jet noise value and the measured value is less than 3 dB, meeting the requirements of engineering development.

[0062] 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 determining the influencing factor of engine jet acoustic efficiency, characterized in that, Includes the following steps: Step 1: Obtain the total mechanical power of the engine ; Step 2: During engine testing, set up N sound pressure level measuring points. The distance between the measuring points and the engine nozzle should be greater than a preset distance. Record the distance between each measuring point and the engine nozzle. The sound pressure level at each measuring point was measured. ,in i Indicates the first i There are 2 measurement points, N≥2, and the sound pressure level measurement points are point sound source propagation points; Step 3, according to , Calculate the sound power spectrum at each measuring point; Step 4: Calculate the total sound power corresponding to each measuring point based on the sound power spectrum of each measuring point; Step 5: Based on the total acoustic power and total mechanical power corresponding to each measuring point Calculate the acoustic efficiency influence factor for each measuring point to obtain N acoustic efficiency influence factors. Step 6: Take the average value of the N sound efficiency influencing factors and use it as the engine jet sound efficiency influencing factor.

2. The method for determining the influence factor of engine jet sound efficiency according to claim 1, characterized in that, Step 1, obtaining the total mechanical power of the engine, includes: in, It is the total mechanical power of the engine. It is the thrust of the engine; It is the velocity of the jet stream at the engine exit.

3. The method for determining the influence factor of engine jet sound efficiency according to claim 2, characterized in that, When the engine is a solid rocket motor and the influence of solid particles is considered, the thrust of the engine including the particle effect can be calculated by adding a jet particle phase at the combustion chamber inlet. Engine outlet jet velocity and obtain the total mechanical power of the engine. .

4. The method for determining the influence factor of engine jet sound efficiency according to claim 1, characterized in that, Step 3 involves calculating the sound power spectrum at each measuring point, determined according to the following formula: in, Indicates the first i The sound power spectrum at each measuring point.

5. The method for determining the influence factor of engine jet sound efficiency according to claim 2, characterized in that, Step 5 involves calculating the acoustic efficiency influence factor for each measuring point, determined according to the following formula: in, Indicates the first i The total sound power corresponding to each measuring point Indicates the first i The acoustic efficiency influence factor corresponding to each measuring point.

6. A device for determining the influence factor of engine jet sound efficiency, characterized in that, include: Engine total mechanical power acquisition module: used to obtain the engine's thrust. Engine outlet jet velocity Obtain the total mechanical power of the engine ; Sound power spectrum acquisition module: used to determine the distance from the engine nozzle of each of the N sound pressure level measurement points set up during engine testing. and the sound pressure level measured at each measuring point. Obtain the sound power spectrum at each measuring point. ;in i Indicates the first i There are 2 measurement points, N≥2, and the sound pressure level measurement points are point sound source propagation points; Total sound power acquisition module: used to obtain the sound power spectrum of each measuring point. Obtain the total sound power corresponding to each measuring point ; The sound efficiency influencing factor acquisition module is used to obtain the total sound power at each measurement point. Total mechanical power of the engine Calculate the acoustic efficiency influence factor for each measuring point. ; The module for averaging the sound efficiency influence factors is used to obtain the sound efficiency influence factors of the engine jet.

7. The device for determining the influence factor of engine jet sound efficiency according to claim 6, characterized in that, Engine total mechanical power acquisition module: based on Obtain the total mechanical power of the engine ; Sound power spectrum acquisition module: based on Obtain the sound power spectrum at each measuring point; Acquisition module for sound efficiency influencing factor: based on Obtain the acoustic efficiency influence factor for each measuring point.

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