Low-noise design and evaluation method based on flow field wake

Abstract

The present invention provides a low-noise design and evaluation method based on flow field wake, which comprises the following steps: S1. Based on blade aerodynamic shaping and flow passage, a three-dimensional simulation grid model is constructed for three-dimensional numerical simulation; S2. Conduct low-noise design on the outer stator of a high-bypass ratio turbofan engine; S3. Conduct blade shaping and aerodynamic analysis; S4. Evaluate the effect of the noise reduction design. The low-noise design and evaluation method based on flow field wake utilizes the three-dimensional numerical simulation results to carry out low-noise design of the fan stator blades, iterates with aerodynamics, obtains a low-noise design scheme for the stator blades while ensuring aerodynamic efficiency, and obtains the evaluation result of the noise reduction effect. The low-noise design method obtains a noise reduction scheme and a noise reduction evaluation result while ensuring aerodynamic efficiency. Without reducing aerodynamic efficiency, a noise reduction design scheme for the stator blades is obtained based on the numerical simulation wake results.

Description

Technical Field

[0001] The present invention relates to the field of engine acoustics, and particularly to a low-noise design and evaluation method based on flow field wake. Background Art

[0002] With the continuous increase in the bypass ratio design of turbofan engines, fan / compressor noise has become one of the main noise sources of turbofan engines. Fan / compressor noise is mainly divided into broadband noise and discrete noise. Among them, broadband noise is generated by the interaction of non-periodic disturbances with solid surfaces, such as factors like the boundary layer on the blade surface, vortex shedding at the trailing edge, boundary layer pressure pulsation, and atmospheric turbulence interference. There are many mechanisms for generating discrete noise, which is caused by the periodic interaction between the blade and the airflow, and is usually related to the blade passing frequency BPF and its harmonics.

[0003] For low-speed rotating blade machines, broadband noise is the main sound source, while for high-speed fans / compressors, discrete noise dominates. Therefore, if the discrete noise of the fan / compressor can be correctly predicted, the total noise level of the engine can be determined quite accurately. Conducting noise reduction design for discrete noise has the most obvious effect. For fans / compressors operating at supersonic speeds, in addition to rotor / stator interference noise, it also includes shock wave noise formed by the interaction between the blade and the supersonic oncoming flow.

[0004] However, research shows that the energy level of shock wave noise will continuously decay as the distance of the observation point from the sound source increases. It can be seen that even in the supersonic case, rotor / stator interference noise is still an important part of the discrete noise of the fan / compressor.

[0005] In addition, although isolated rotor noise dominates during the takeoff and climb phases of supersonic fans, rotor / stator interference is still the main factor during the low-speed operation phase of aircraft landing. Therefore, studying the propagation law of rotor / stator interference noise and its prediction is of great significance for both engine acoustic design and the noise reduction design of engine nacelles.

[0006] At the same time, the progress of domestic large aircraft and civil large bypass ratio turbofan engine projects has also put forward new requirements for the research on the generation mechanism of aerodynamic noise and noise reduction technology. Establishing a method to predict aerodynamic noise information using three-dimensional numerical simulation results is not only a practical need for engine noise reduction design but also can provide a basis for exploring new ideas for noise reduction technology.

[0007] In view of this, those skilled in the art have proposed a new low-noise design and evaluation method based on flow field wake in order to overcome the above technical problems. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the defect that in the prior art, people's requirements for the noise of fans / compressors are getting higher and higher, and the evaluation of the noise reduction effect is not accurate enough, and to provide a low-noise design and evaluation method based on the flow field wake.

[0009] The present invention solves the above technical problem through the following technical solutions:

[0010] A low-noise design and evaluation method based on the flow field wake, characterized in that the low-noise design and evaluation method includes the following steps:

[0011] S1. Based on the blade aerodynamic shape and the flow passage, construct a three-dimensional simulation grid model and conduct three-dimensional numerical simulation;

[0012] S2. Conduct low-noise design on the outer stator of a high-bypass ratio turbofan engine;

[0013] S3. Conduct blade shape and aerodynamic analysis;

[0014] S4. Evaluate the effect of the noise reduction design.

[0015] According to an embodiment of the present invention, the following steps are further included before the step S1: input the blade aerodynamic shape, the flow passage and the working condition information.

[0016] According to an embodiment of the present invention, the step S1 specifically includes the following steps:

[0017] S 11 : Based on the blade aerodynamic shape and the flow passage, construct a three-dimensional simulation grid model;

[0018] S 12 : Set the calculation example according to the working condition point information to be designed, and select a suitable fluid and flow model;

[0019] S 13 : Carry out three-dimensional steady numerical simulation, obtain the steady flow field simulation result, extract the fan rotor wake information, and use it as the input for low-noise design.

[0020] According to an embodiment of the present invention, the step S2 adopts the first method: carry out blade low-noise design work based on the wake model.

[0021] According to an embodiment of the present invention, in the first method, the average mainstream flow parameters are obtained through three-dimensional numerical simulation, and the wake input data is constructed using the wake model for carrying out the low-noise design work of the stator blades.

[0022] According to an embodiment of the present invention, the step S2 adopts the second method: carry out low-noise design work based on the three-dimensional numerical simulation rotor blade wake result.

[0023] According to an embodiment of the present invention, the second method specifically includes the following steps:

[0024] S 21 Obtain the rotor wake information in front of the stator blades through three-dimensional numerical simulation;

[0025] S 22 Determine whether it is steady wake information or unsteady wake information; if it is steady wake information, enter S 23 ; if it is unsteady wake information, enter S 24 ;

[0026] S 23 Interpolate the incoming flow wake to the radial integration points and perform circumferential Fourier series expansion;

[0027] S 24 Extract the complex velocity coefficients of each term;

[0028] S 25 Calculate the noise intensity of each combination of bowed and swept stator blades;

[0029] S 26 Obtain the unsteady load and noise intensity.

[0030] According to an embodiment of the present invention, step S3 specifically includes: determining the axial and circumferential offsets and the three-dimensional spatial shape of the blade stacking axis through the optimal bend angle and sweep angle design parameters of the stator obtained in step S2, so as to control the shaping method of blade bending or sweeping.

[0031] According to an embodiment of the present invention, after step S3, it further includes: judging whether the aerodynamic design requirements are met. If so, enter step S4; if not, return to step S3.

[0032] According to an embodiment of the present invention, step S4 specifically includes: re-performing grid modeling through the three-dimensional blade modeling parameters output by step S3, and calculating to obtain the three-dimensional flow field results and sound field results.

[0033] According to an embodiment of the present invention, the method for obtaining the sound field results in step S4 adopts a semi-analytical method or a numerical method.

[0034] According to an embodiment of the present invention, after step S4, it further includes: judging whether the acoustic design requirements are met. If so, complete the design work of the low-noise stator blades; if not, return to step S2.

[0035] The positive and progressive effects of the present invention are as follows:

[0036] The low-noise design and evaluation method based on the flow field wake uses the three-dimensional numerical simulation results to carry out the low-noise design of the fan stator blades, and iterates with the aerodynamics. On the premise of ensuring the aerodynamic efficiency, a low-noise design scheme for the stator blades is obtained, and the evaluation result of the noise reduction effect is obtained.

[0037] The low-noise design method carries out the noise reduction design of the stator blades based on the numerical simulation wake results on the premise of ensuring the aerodynamic efficiency, and obtains the noise reduction scheme and the noise reduction evaluation result. Brief Description of the Drawings

[0038] The above and other features, properties and advantages of the present invention will become more obvious through the following description in conjunction with the drawings and embodiments. In the drawings, the same reference numerals always represent the same features, where:

[0039] Figure 1 It is a schematic diagram of the stator blade sweep in the low-noise design and evaluation method based on the flow field wake of the present invention.

[0040] Figure 2 It is a flow chart of the low-noise design and evaluation method based on the flow field wake of the present invention.

[0041] Figure 3 It is a flow chart of step S2 in the low-noise design and evaluation method based on the flow field wake of the present invention. Detailed Description of the Embodiments

[0042] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be given in conjunction with the drawings.

[0043] Now the embodiments of the present invention will be described in detail with reference to the drawings. Now the preferred embodiments of the present invention will be described in detail, and the examples are shown in the drawings. Whenever possible, the same reference numerals will be used throughout the drawings to represent the same or similar parts.

[0044] In addition, although the terms used in the present invention are selected from well-known and commonly used terms, some of the terms mentioned in the description of the present invention may be selected by the applicant according to his or her judgment, and their detailed meanings are described in the relevant parts of the description herein.

[0045] In addition, it is required to understand the present invention not only through the actual terms used, but also through the meaning implied by each term.

[0046] With the rapid development of the contemporary civil aviation industry, airworthiness regulations have put forward new requirements for aircraft noise levels. As the main noise source, new requirements have been put forward for the research on the generation mechanism of engine aerodynamic noise and noise reduction technologies. And as one of the main noise sources of the engine, the fan / compressor also faces new noise reduction challenges. The technical problem to be solved by the present invention is to further reduce the tonal noise level of the fan / compressor from the sound source, and provide a low-noise design and evaluation method based on the flow field wake.

[0047] Figure 1 It is a schematic diagram of stator blade sweep and lean in the low-noise design and evaluation method based on the flow field wake of the present invention.

[0048] As Figure 1 shown, in the low-noise design and evaluation method based on the flow field wake of the present invention, the stator blades are placed parallel to the mainstream. From the blade root to the blade tip, when the leading edge of the blade changes upstream and downstream with the increase of the radial position, it is called sweep. When the blade changes circumferentially with the increase of the radial position, it is called lean.

[0049] Figure 2 It is a flow chart of the low-noise design and evaluation method based on the flow field wake of the present invention. Figure 3 It is a flow chart of step S2 in the low-noise design and evaluation method based on the flow field wake of the present invention.

[0050] As Figure 2 and Figure 3 shown, a low-noise design and evaluation method based on the flow field wake of the present invention includes the following steps:

[0051] Step S1: Based on the blade aerodynamic shape and flow passage, construct a three-dimensional simulation grid model and conduct three-dimensional numerical simulation;

[0052] Step S2: Conduct low-noise design on the stator of the high-bypass ratio turbofan engine;

[0053] Step S3: Conduct blade shaping and aerodynamic analysis;

[0054] Step S4: Evaluate the effect of the noise reduction design.

[0055] Preferably, before the step S1, the following steps are further included: input the blade aerodynamic shape, flow passage and working condition information.

[0056] More preferably, the step S1 specifically includes the following steps:

[0057] S 11 : Based on the blade aerodynamic shape and flow passage, construct a three-dimensional simulation grid model;

[0058] S 12, set up the example according to the operating point information designed as needed, and select appropriate fluids and flow models;

[0059] S 13 , conduct three-dimensional steady numerical simulation, obtain the simulation results of the steady flow field, extract the wake information of the fan rotor, and use it as the input for low-noise design.

[0060] Specifically, in step S1, a three-dimensional simulation grid model is constructed based on the blade aerodynamic shape and flow channel. Set up the example according to the operating point information designed as needed, select appropriate fluids and flow models, ensure that the inlet and outlet boundary conditions of the example are correct, conduct three-dimensional steady numerical simulation, obtain the simulation results of the steady flow field, extract the wake information of the fan rotor, and use it as the input for low-noise design.

[0061] For steady flow field calculation, the convergence condition can be judged from three aspects: a) the flow rate balance at the inlet and outlet; b) the efficiency tends to be flat; c) the residual decreases and tends to be flat.

[0062] For unsteady flow field calculation, it is carried out on the basis of steady calculation, and finally the simulation results of the unsteady flow field are obtained. The convergence condition is the same as that of steady flow field calculation.

[0063] Preferably, step S2 adopts the first method: carry out low-noise design of the blade based on the wake model. In the first method, the average mainstream flow parameters are obtained through three-dimensional numerical simulation, and the wake input data are constructed using the wake model for carrying out low-noise design of the stator blade.

[0064] Alternatively, step S2 can adopt the second method: carry out low-noise design based on the wake results of the rotor blade through three-dimensional numerical simulation.

[0065] The second method specifically includes the following steps:

[0066] Step S 21 , obtain the rotor wake information in front of the stator blade through three-dimensional numerical simulation;

[0067] Step S 22 , judge whether it is steady wake information or unsteady wake information; if it is steady wake information, enter S 23 ; if it is unsteady wake information, enter S 24 ;

[0068] Step S 23 , interpolate the incoming wake to the radial integration points and perform circumferential Fourier series expansion;

[0069] Step S 24 , extract the complex velocity coefficients of each term;

[0070] Step S 25 、Calculate the noise intensity of each bowed and swept stator blade combination;

[0071] Step S 26 、Obtain the unsteady load and noise intensity.

[0072] Specifically, in the low-noise model of step S2, the three-dimensional lifting surface theory is used to establish an integral equation to solve the unsteady load on the blade surface through the non-penetration boundary condition of the vibration velocity of the particles on the blade surface. The particle velocity on the stator blade includes the wake perturbation velocity under the upstream incoming flow condition and the projection of the particle perturbation velocity caused by the unsteady load in the normal direction of the blade surface.

[0073] Here, two methods can be used in low-noise design (as shown in Figure 3 ):

[0074] First, carry out the low-noise design of the blade based on the wake model:

[0075] Obtain the average mainstream flow parameters, etc. through three-dimensional numerical simulation, and use the wake model to construct the wake input data for carrying out the low-noise design of the stator blade.

[0076] Second, carry out the low-noise design based on the wake results of the three-dimensional numerical simulation of the rotor blade:

[0077] Through three-dimensional numerical simulation, obtain the rotor wake information in front of the stator blade, mainly focusing on speed, pressure, etc., as the input for the low-noise design.

[0078] Among them, for the steady wake, it has the following characteristics:

[0079] For the steady wake information, in the fixed column coordinate system of the pipeline, the circumferential component of the perturbation caused by the harmonic rotor wake on the stator blade can be expressed as a periodic change parameter with time under ideal conditions. Process the rotor wake, extract the circumferential velocity amplitudes of each blade passing frequency corresponding to the wakes under different working conditions, which contain both amplitude and phase information, calculate the rotor-stator interference noise using the three-dimensional lifting surface theory, obtain the unsteady load and noise level on the stator blade surface, judge the pros and cons of the bowed and swept design scheme through the noise level, and select the design result of the bowed and swept combination with a smaller sound power level.

[0080] In addition, for the unsteady wake, it has the following characteristics:

[0081] I. The requirements for using the three-dimensional lifting surface are the same as those for the steady wake.

[0082] II. Wake extraction. For the time-domain calculation results, the circumferential velocity amplitudes of each blade passing frequency can be obtained through Fourier transform. For the frequency-domain calculation results, the circumferential velocity amplitudes of each blade passing frequency can be directly obtained.

[0083] The step S3 preferably specifically includes: determining the axial and circumferential offsets and the three-dimensional spatial shape of the blade stacking axis by using the stator's optimal bend angle and sweep angle design parameters obtained in the step S2, so as to control the shaping mode of the blade bend or sweep.

[0084] The specific selection here needs to be determined by the optimization iteration of aerodynamics / structure / strength. Based on the prototype blade of the aerodynamic design, the blade bend and sweep shaping work is carried out.

[0085] The calculated flow field data such as pressure, temperature, Mach number, etc., the blade performance data such as angle of attack, trailing angle, etc., and the performance data such as pressure ratio, temperature ratio, and efficiency all have reasonable values. Among them, the flow rate, pressure ratio, efficiency, etc. need to meet the technical requirements of the engine's aerodynamic performance design. After multiple rounds of iteration and meeting the aerodynamic performance design requirements, the blade is finally shaped.

[0086] After the blade shaping is completed, the shaping result can be checked to check for the appearance of singular points, lines, and surfaces, and whether the thickness distribution is uneven and non-smooth, so as to ensure the output of available blade three-dimensional shaping parameters.

[0087] After the step S3, it further includes: judging whether the aerodynamic design requirements are met. If they are met, enter the step S4; if not, return to the step S3.

[0088] The step S4 preferably specifically includes: re-performing grid modeling by using the blade three-dimensional shaping parameters output in the step S3, and calculating to obtain the three-dimensional flow field result and the sound field result.

[0089] The way to obtain the sound field result in the step S4 here adopts the semi-analytical method or the numerical method.

[0090] Among them, for the semi-analytical method, according to the sound field theoretical model in the pipeline, the sound field result and the noise level are obtained through the blade surface load. For the numerical method, the sound source is extracted based on the three-dimensional flow field calculation result to obtain the noise level.

[0091] After the step S4, it further includes: judging whether the acoustic design requirements are met. If they are met, the design work of the low-noise stator blade is completed; if not, return to the step S2 to re-start the design work.

[0092] To sum up, the low-noise design and evaluation method based on the flow field wake uses the three-dimensional numerical simulation results to carry out the low-noise design of the fan stator blade, and through aerodynamic iteration, on the premise of ensuring the aerodynamic efficiency, obtains the low-noise design scheme of the stator blade and the evaluation result of the noise reduction effect. When carrying out the low-noise design of the blade, since the stator annular cascade geometry has an important influence on the solution of the sound source and sound propagation, the influence of the blade three-dimensional effect needs to be focused on.

[0093] The low-noise design method obtains a noise reduction solution and a noise reduction evaluation result on the premise of ensuring the aerodynamic efficiency. On the premise of not reducing the aerodynamic efficiency, a stator blade noise reduction design solution is obtained based on the numerical simulation wake result.

[0094] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that these are only examples, and the protection scope of the present invention is defined by the appended claims. Without departing from the principles and essence of the present invention, those skilled in the art can make various changes or modifications to these embodiments, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A low-noise design and evaluation method based on the wake of a flow field, characterized in that The low-noise design and evaluation method includes the following steps: S1. Based on the blade aerodynamic shape and flow passage, construct a three-dimensional simulation grid model and conduct three-dimensional numerical simulation; S2. Conduct low-noise design on the outer stator of the high-bypass turbofan engine; S3. Conduct blade shaping and aerodynamic analysis; S4. Evaluate the effect of the noise reduction design; In step S2, the first method is adopted: carry out the low-noise design of the blade based on the wake model; alternatively, in the first method, obtain the average mainstream flow parameters through three-dimensional numerical simulation, and use the wake model to construct the wake input data for carrying out the low-noise design of the stator blade; Or, in step S2, the second method is adopted: carry out the low-noise design based on the wake result of the three-dimensional numerical simulation rotor blade; The second method specifically includes the following steps: S 21 , the rotor wake information in front of the stator vane is obtained through three-dimensional numerical simulation; S 22 Determine whether it is steady wake information or unsteady wake information; if it is steady wake information, enter S 23 ; if it is unsteady wake information, enter S 24 ; S 23 , interpolate the oncoming flow wake to the radial integration points and perform a circumferential Fourier series expansion; S 24 , extract the plural velocity coefficients for each item; S 25 Calculate the noise intensity of each combined bowed and swept stator blade; S 26 , obtain unsteady loads and noise intensities; Step S3 specifically includes: determine the axial and circumferential offsets and the three-dimensional spatial shape of the blade stacking axis through the optimal bend angle and sweep angle design parameters of the stator obtained in step S2, so as to control the shaping method of the blade bend or sweep.

2. The low-noise design and evaluation method based on the wake of the flow field according to claim 1, characterized in that, Before step S1, the following steps are further included: input the blade aerodynamic shape, flow passage and working condition information.

3. The low-noise design and evaluation method based on the flow field wake according to claim 2, characterized in that Step S1 specifically includes the following steps: S 11 Construct a three-dimensional simulation grid model based on the blade aerodynamic shape and flow channel; S 12 、Set up the example according to the working condition point information designed as needed, and select the fluid and flow model; S 13 、Conduct three-dimensional steady numerical simulations to obtain the simulation results of the steady flow field, extract the wake information of the fan rotor, and use it as the input for low-noise design.

4. The low-noise design and evaluation method based on the flow field wake according to claim 1, wherein After step S3, it is also included: judge whether the aerodynamic design requirements are met. If so, enter step S4; if not, return to step S3.

5. The low-noise design and evaluation method based on the wake of the flow field according to claim 2, characterized in that Step S4 specifically includes: re-perform grid modeling through the blade three-dimensional shaping parameters output by step S3, and calculate to obtain the three-dimensional flow field result and sound field result.

6. The low-noise design and evaluation method based on the flow field wake according to claim 5, characterized in that, The method for obtaining the sound field result in step S4 adopts the semi-analytical method or the numerical method.

7. The low-noise design and evaluation method based on the wake of the flow field according to claim 6, characterized in that, After step S4, it is also included: judge whether the acoustic design requirements are met. If so, complete the design of the low-noise stator blade; if not, return to step S2.

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