CN112177777B

CN112177777B - A design method for noise reduction airfoil leading edge with high degree of freedom controllable theoretical sound velocity point

Info

Publication number: CN112177777B
Application number: CN202011051013.3A
Authority: CN
Inventors: 柳阳威; 赵天铭; 孙晓峰; 侯杰萱; 唐雨萌
Original assignee: Beihang University
Current assignee: Beihang University
Priority date: 2020-09-29
Filing date: 2020-09-29
Publication date: 2022-03-18
Anticipated expiration: 2040-09-29
Also published as: CN112177777A

Abstract

The invention relates to the field of transonic fan/compressor shock noise control, and discloses a leading edge design method for a high degree of freedom controllable theoretical sound speed point, including a three-stage design for the leading edge, and the three-stage design for the leading edge includes : Step 1, numerical simulation of the original airfoil; Step 2, evaluation of the noise level of the original airfoil; Step 3, determination of the three-stage design range of the leading edge; Step 4, selection of characteristic parameters of the three-stage design of the leading edge; Edge section design; Step 6, design of two transition sections connecting the leading edge section to the suction surface/pressure surface of the airfoil; Step 7, Numerical simulation of the three-stage leading edge design of the airfoil; Step 8, three-stage design of the leading edge Evaluation of blade noise reduction benefits. The leading edge design method of the high degree of freedom controllable theoretical sound velocity point redesigns the leading edge of the airfoil under the premise of ensuring that the curvature of the leading edge point of the airfoil remains unchanged. Beneficial effects of wave strength and noise level.

Description

Noise reduction blade profile leading edge design method for high-freedom controllable theoretical sound velocity point

Technical Field

The invention relates to the field of shock wave noise control of transonic fans/compressors, in particular to a high-freedom controllable theoretical sound velocity point front edge design method.

Background

At present, the market of international large commercial passenger aircraft is occupied by European Airbus (Airbus) and American Boeing (Boeing), in order to consolidate the status, the noise standard gradually becomes an important index for clearing the competition in the industry, the standard of a new period and a new stage is utilized to eliminate a large number of commercial passenger aircraft or improve the research and development difficulty of competitors, and a severe technical test is provided for the commercial aircraft engine independently developed in China; at present, the fast development stage of commercial airliners in China is just being corrected, a branch airliner ARJ21 developed by Chinese commercial aircraft (COMAC) is in the market operation period, the first short-range airliner C919 in the first shelf finishes the first flight in 5 months of 2017, and the start of delivery is expected to be in 2021; with respect to the current trend, by the time of C919 delivery, it is likely to release more stringent airworthiness standards, which will become one of the main indicators for limiting the ability of the commercial customers with proprietary intellectual property rights in china to enter the international market.

For a commercial engine with a large bypass ratio, the relative speed of the tip of a fan/compressor rotor is supersonic, an outward extending shock wave is generated at the front edge, the shock wave rotates along with the rotor and propagates upstream to generate shock wave noise, the noise exceeds jet flow noise, the shock wave noise becomes a first noise source of the commercial engine with the large bypass ratio at present, and the control of the shock wave noise is the greatest importance of the noise reduction of the engine.

Since the end of the 90 s of the 20 th century, the european union and the united states have successively developed various engine noise reduction plans, such as the Ultra Efficient Engine Technology (UEET) by NASA in the united states, the quiet technical verification machine (QTD) research plan, the TECH56 and LEAP56 plans implemented by GE corporation in cooperation with sneaker corporation, and the like; the core technology is roughly divided into: 1) the oblique notch air inlet channel and sound lining technology can directionally refract/absorb noise and reduce the outward transmission of the noise, but the method is a temporary solution and a permanent solution; 2) the method can effectively reduce the shock wave strength, but through research for twenty years, the technology is mature and the lifting space is small; therefore, a simple, effective and compatible method for reducing the shock wave noise of the transonic fan/compressor is needed.

Disclosure of Invention

Technical problem to be solved

The invention aims to provide a method for designing a noise reduction blade profile leading edge with a high degree of freedom and a controllable theoretical sound velocity point, which changes the position of the theoretical sound velocity point through three-section design on the basis of the existing transonic fan/compressor blade profile, further redistributes the curvature transition process of the integral leading edge section, optimizes the shock wave-expansion wave system interference condition at the leading edge of the blade profile, achieves the purpose of reducing the strength of overhanging shock waves, and further realizes the effect of reducing transonic blade profile shock wave noise; the existing blade profile leading edge modification design method mainly achieves the purpose of noise reduction by increasing the curvature of a blade profile leading edge point, and when the curvature of the blade profile leading edge point is too large, a sharp leading edge phenomenon can occur, so that the blade profile rigidity is reduced.

(II) technical scheme

In order to solve the technical problem, the invention provides a noise reduction blade profile leading edge design method with high degree of freedom and controllable theoretical sound velocity point, which comprises a leading edge three-section design, wherein the leading edge three-section design comprises a leading edge section design and two transition sections connected with a suction surface/a pressure surface of the blade profile and the leading edge section; the leading edge section is a blade profile with two theoretical sound velocity points of a blade profile suction surface/pressure surface passing through a blade profile leading edge point connecting section, and two transition sections of the leading edge section connected with the blade profile suction surface/pressure surface are respectively the blade profile from the theoretical sound velocity points of the blade profile suction surface and the pressure surface to a modified leading edge and original blade profile connecting section; the leading edge three-stage design comprises: firstly, simulating the numerical value of an original leaf profile; evaluating the original leaf-shaped noise level; determining a front edge three-section type design range; selecting three-section design characteristic parameters of the front edge; designing a front edge section; designing two transition sections for connecting the front edge section with the suction surface/pressure surface of the blade profile; seventhly, designing the numerical simulation of the blade profile of the front edge in a three-section mode; eighthly, evaluating the noise reduction benefit of the blade profile designed in a three-section manner at the front edge;

the first step comprises the following steps: performing grid drawing on an original blade profile, setting the length of an inlet to be three times of the axial chord length in order to capture the forward propagation process of the overhanging shock wave, and performing encryption treatment to ensure that the number of grid points in each shock wave wavelength is not less than 30; performing quasi two-dimensional Reynolds average N-S equation (RANS) numerical simulation on the original leaf profile, and improving the spatial precision by MUSCL interpolation; setting an inlet total temperature and total pressure airflow angle and an outlet back pressure according to a design working condition to obtain a numerical simulation flow field of an original blade profile;

(ii) a The second step comprises the following steps: superposing a uniform and sparse acoustic grid on the numerical simulation flow field of the original blade profile obtained in the step one, and interpolating the pressure p, the density rho, the axial velocity u and the circumferential velocity v of the numerical simulation flow field into the acoustic grid by using a second-order precision inverse distance weighting interpolation method; defining a formula using two-dimensional sound intensity

Evaluating the noise level, wherein

Respectively representing the velocity vector, the axial velocity, the density and the circumferential average quantity of pressure intensity, v ', u ' and p ' represent disturbance quantities of the velocity vector, the axial velocity and the pressure intensity, and gamma is a specific heat ratio; integrating the sound intensity along the axial section S to obtain the sound power

(ii) a The third step comprises: extracting a camber line of an original blade profile, drawing a camber line slope distribution graph, keeping the camber line slope stable before a% of axial chord length, starting to change after the a% of axial chord length, and extracting the blade profile from a blade profile leading edge point to an a% of axial chord length region to serve as a leading edge three-stage design range;

(ii) a The fourth step comprises: selecting a relative coordinate with a theoretical sound velocity point as a front edge three-section type design characteristic parameter, defining the vertical distance from the theoretical sound velocity point to a mean camber line as Y ', the distance from the theoretical sound velocity point parallel to the mean camber line direction to a front edge point of the blade profile as X', designing a plurality of groups (not less than two groups) of schemes by a separation variable method, and respectively exploring the relationship between the X 'and Y' coordinates and the blade profile sound power;

(ii) a Designing a connecting line between the theoretical sound velocity points determined in the fourth step by adopting a quintic Bezier curve, wherein the coordinates, the slope and the curvature of the theoretical sound velocity points are known quantities; bezier curve general formula is

The quintic Bezier curve needs 6 control points, the coincidence of the midpoint of the leading edge section and the leading edge point of the blade profile is set, the number of the control points is reduced to 3 through the symmetry design, and L can be obtained₁、L₂、L₃Relation between three-point horizontal coordinates

Starting point L₁At theoretical sonic velocity point, curve startThe slope is a straight line L₁L₂Slope, L₂The ordinate is obtained from the abscissa through the slope; l is₃The horizontal coordinate and the vertical coordinate of the point are input quantities, and L is changed₃The point horizontal coordinate and the point vertical coordinate enable the curvature of the theoretical sound velocity point and the curvature of the front edge point of the blade profile to meet the curvature invariant condition;

(ii) a The sixth step comprises: designing two transition sections connecting the leading edge section and the suction surface/pressure surface of the blade profile by adopting a cubic Bezier curve, wherein L is₆L₇、 L₈L₉The slope is respectively the same as the theoretical sound velocity point and the slope of the junction of the modified front edge and the blade profile, and L is adjusted₇、L₈Two points of x coordinates enable curvatures of two ends to meet a curvature invariant condition;

(ii) a The seventh step comprises: performing quasi three-dimensional Reynolds average N-S equation (RANS) numerical simulation on the front edge three-section design blade profile, adopting the same numerical simulation setting as the numerical simulation of the original blade profile in order to eliminate errors caused by grids or boundary conditions, and repeating the first step and the second step on the front edge three-section design blade profile to obtain an acoustic power result of the front edge three-section design blade profile;

(ii) a The eighth step comprises: and evaluating the noise reduction benefit of the front edge three-section design blade profile, specifically, comparing the acoustic power result of the front edge three-section design blade profile with the acoustic power result of the original blade profile to obtain the noise reduction benefit of the front edge three-section design blade profile.

(III) advantageous effects

Compared with the prior art, the method for designing the noise reduction blade profile leading edge with the high degree of freedom and the controllable theoretical sound velocity point has the following beneficial effects:

by the three-section design of the front edge, the theoretical sound velocity point coordinate is introduced to the front edge of the blade profile as a characteristic parameter, so that the modified design has higher degree of freedom, and meanwhile, with the mechanism research on shock wave noise, the theoretical sound velocity point can also be replaced by other important parameters, so that the three-section design has wide performance development and promotion space;

the three-section design method of the leading edge provided by the invention redesigns the leading edge of the blade profile on the premise of ensuring that the curvature of the leading edge point of the blade profile is not changed, can effectively reduce the average thickness of the leading edge, avoids the design of a sharp leading edge, and further improves the rigidity of the blade profile of the modified design;

the front edge three-section design method provided by the invention can reduce the overhanging shock wave intensity by 15% and reduce the noise level by 2dB at the position 1 times the chord length away from the front edge point of the blade profile by changing the position of the theoretical sound velocity point.

Drawings

FIG. 1 is a schematic flow chart of steps of a method for designing a noise reduction airfoil leading edge with a high-degree-of-freedom controllable theoretical acoustic velocity point;

FIG. 2 is a slope profile of a camber line in a CM-1.2 airfoil of an embodiment of the present invention, where ξ is the axial distance from a point on the aft airfoil to the leading edge point of the airfoil dimensionless with the axial chord length of the airfoil;

FIG. 3 is a schematic view of a leading edge segment design of a leading edge three-segment design in accordance with an embodiment of the present invention;

FIG. 4 is a schematic view of a transition section of a three-section design of a leading edge in accordance with an embodiment of the present invention;

FIG. 5 is a comparison of example 1, example 2, example 3 and the original profile for a three-stage design of the leading edge;

FIG. 6 is a comparison of example 4, example 5, example 6 and the original profile for a three-stage design of the leading edge;

FIG. 7 is a graph of the curvature distribution of the original blade profile and examples 1, 2, 3 for a three-stage design of the leading edge;

FIG. 8 is a graph of the curvature distribution of examples 4, 5, 6 and the original blade profile for a three-stage design of the leading edge;

FIG. 9 is a graph comparing acoustic power levels of examples 1, 2, 3 and original blade profiles for a three-stage design of the leading edge;

FIG. 10 is a graph comparing acoustic power levels of examples 4, 5, 6 and the original blade profile for a three-stage design of the leading edge;

in the figure, 1: a profile leading edge point; 2: a leading edge segment; 3: a transition section; 4: a theoretical acoustic velocity point; 5: the front edge three-section design is used for designing the connection point of the front edge of the blade profile and the blade profile.

Detailed Description

The following detailed description of specific embodiments of the present invention is provided in connection with the accompanying drawings and examples, which are set forth to illustrate, but are not to be construed to limit the scope of the invention.

Example (b):

taking the disclosed CM-1.2 blade profile as an example, the design Mach number of the blade profile is 1.2, and the geometric coordinates are shown in the literature 'Qiu name. study on the shock wave tissue in the rotor channel of the high-grade pressure ratio axial flow compressor [ D ]. Nanjing aerospace university, 2014'

And (4) carrying out numerical simulation on the original blade profile according to the method in the step one. An equation S-A turbulence model is adopted during calculation, Green Gaussian unit-based method is adopted for gradient interpolation, A standard interpolation method is adopted for pressure interpolation, the density, kinetic energy and turbulence viscosity are firstly interpolated to calculate an initial field by first-order precision MUSCL interpolation, and then third-order precision MUSCL interpolation is carried out to obtain A final solution, so that the speed is increased; the grid adopts an HOH topological structure, an inlet section is extended and encrypted in order to capture the forward propagation process of the overhanging shock wave, the grid parameter of the inlet section is 301, 177 and 5, the total number of the grids is 26.6 thousands, and the total number of the grids is 44 thousands; the total pressure of the inlet given total temperature is 300K and 101325Pa respectively, the axial air intake is realized, the circumferential wall surface is a periodic surface, the spanwise wall surface is an Euler slip wall surface, the translation speed of the blade is 310m/s, and the outlet back pressure is 101325 Pa.

According to the method in the second step, 300 x 100 x 5 acoustic grids are connected to the numerical simulation flow field of the original blade profile obtained in the first step from the front edge point of the blade profile to the position of three times of axial chord length, and the pressure p, the density rho, the axial velocity u and the velocity vector which are obtained through numerical simulation are used for obtaining

Interpolating into the acoustic grid by using an inverse distance weighted interpolation method with second-order precision; defining a formula using two-dimensional sound intensity

Evaluating the noise level, wherein

Respectively representing the velocity vector, the axial velocity, the density and the circumferential average quantity of the pressure intensity,v ', u ' and p ' represent disturbance quantities of a velocity vector, an axial velocity and pressure intensity, and gamma is a specific heat ratio; integrating the sound intensity along the axial section S to obtain the sound power

The original CM1-2 blade profile was evaluated to have a noise intensity of 100dB at one axial chord from the leading edge point of the blade profile.

And extracting the original CM-1.2 leaf camber line according to the third step and making a slope distribution diagram of the camber line, as shown in figure 2. In the slope distribution diagram of the camber line of the CM-1.2 blade profile of the embodiment of the invention, the slope of the front 10% region is stable, so that the blade profile from the front edge point of the original blade profile to the region with 10% axial chord length is selected as the three-section design range of the front edge, and the coordinates, the slope and the curvature parameters of the connecting point of the front edge and the blade profile are calculated.

Selecting a theoretical sound velocity point coordinate as a front edge three-section type design characteristic parameter according to the fourth step, defining the vertical distance from the theoretical sound velocity point to a mean camber line as Y ', and defining the distance from the theoretical sound velocity point parallel to the mean camber line direction to the front edge point of the blade profile as X'; through a separation variable method, 6 groups of calculation example parameters are designed and shown in table 1, wherein calculation example 1, calculation example 2 and calculation example 3 are used for comparing the influence of Y' coordinates on the noise level; examples 4, 5 and 6 were used to compare the effect of the X' coordinate on the noise level.

TABLE 1 theoretical sound velocity point location parameter

Serial number	X'/mm	Y'/mm
			EXAMPLE 1	1.3	-0.18
EXAMPLE 2	1.3	-0.23
			EXAMPLE 3	1.3	-0.28
EXAMPLE 4	0.8	-0.23
			EXAMPLE 5	1.3	-0.23
EXAMPLE 6	1.8	-0.23

And designing 6 groups of leading edge sections and two transition sections of the leading edge sections connected with the suction surface/pressure surface of the blade profile according to the method in the fifth step and the sixth step. FIG. 5 shows the front edge three-segment design examples 1, 2, 3 and the original blade profile pair; the front edge three-segment design examples 4, 5, 6 and the original blade profile pair are shown in FIG. 6. The method is characterized in that the curvature of the front edge point of the blade profile is kept to be the same as that of the original blade profile, the three-section type design blade profile curvature distribution of the front edge is shown in figures 7 and 8, the front edge of the original blade profile is a circular front edge, the curvature is kept unchanged firstly, then the front edge descends linearly until the front edge is connected with the blade profile, the design of the front edge with discontinuous curvature can generate a suction peak at the discontinuous curvature point, and the separation resistance of the blade profile is reduced; in the traditional design of the curvature continuous front edge, the curvature is slowly increased, so that the curvature of the front edge point of the blade profile is too large, a sharp front edge is generated, and the rigidity of the blade profile is reduced; from the curvature profile of the three-stage design of the leading edge of the present invention, it can be seen that: the curvature of the front edge point of the blade profile is small, so that the phenomenon of a sharp front edge is effectively avoided; then the curvature rises first and then falls until the blade profile is connected; the whole curvature transition process has no mutation and is continuous all the time.

Performing numerical simulation on the 6 groups of front edge three-section type design blade profile calculation examples designed in the fifth step and the sixth step according to the seventh step and calculating the sound power, wherein the results are shown in fig. 9 and 10, and it can be seen that the noise reduction effect is very obvious near the front edge, and compared with the CM-1.2 original blade profile at the axial chord length which is one time away from the front edge point of the blade profile, the noise reduction of the front edge three-section type design calculation examples 1, 2 and 3 is respectively 0.5dB, 1.6dB and 4.6 dB; the noise reduction of the front edge three-segment design examples 4, 5 and 6 is respectively 0.4dB, 1.6dB and 2.9 dB. Obviously, the noise reduction effect has a monotonous relation with X 'and Y', and the smaller X 'and the larger Y' are, the better the noise reduction effect is. For the Y' 0.18 example, the noise reduction effect may be maintained up to three times the leading edge, still with a 2dB noise reduction effect.

The above-mentioned embodiments are merely preferred embodiments of the present invention, and not intended to limit the present invention, and any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for designing a noise reduction blade profile leading edge with a high-degree-of-freedom controllable theoretical sound velocity point is characterized by comprising the following steps: the design method comprises a front edge three-section design, wherein the front edge three-section design comprises a front edge section design and two transition sections for connecting the front edge section with a blade profile suction surface/pressure surface; the leading edge section is a blade profile with two theoretical sound velocity points of a blade profile suction surface/pressure surface passing through a blade profile leading edge point connecting section, and two transition sections of the leading edge section connected with the blade profile suction surface/pressure surface are respectively the blade profile from the theoretical sound velocity points of the blade profile suction surface and the pressure surface to a modified leading edge and original blade profile connecting section;

the leading edge three-stage design comprises:

firstly, simulating the numerical value of an original leaf profile;

evaluating the original leaf-shaped noise level;

determining a front edge three-section type design range;

selecting three-section design characteristic parameters of the front edge;

designing a front edge section;

designing two transition sections for connecting the front edge section with the suction surface/pressure surface of the blade profile;

seventhly, designing the numerical simulation of the blade profile of the front edge in a three-section mode;

eighthly, evaluating the noise reduction benefit of the blade profile designed in a three-section manner at the front edge;

the second step comprises the following steps: superposing a uniform and sparse acoustic grid on the numerical simulation flow field of the original blade profile obtained in the step one, and interpolating the pressure p, the density rho, the axial velocity u and the circumferential velocity v of the numerical simulation flow field into the acoustic grid by using a second-order precision inverse distance weighting interpolation method; defining a formula using two-dimensional sound intensity

Evaluating the noise level, wherein

The third step comprises: extracting a camber line of an original blade profile, drawing a camber line slope distribution graph, keeping the camber line slope stable before a% of axial chord length, starting to change after the a% of axial chord length, and extracting the blade profile from a blade profile leading edge point to an a% of axial chord length region to serve as a leading edge three-stage design range;

the fourth step comprises: selecting relative coordinates of a theoretical sound velocity point as a front edge three-section type design characteristic parameter, defining the vertical distance from the theoretical sound velocity point to a mean camber line as Y ', the distance from the theoretical sound velocity point to the direction parallel to the mean camber line and the front edge point of the blade profile as X', designing a plurality of groups (not less than two groups) of schemes by a separation variable method, and respectively exploring the relationship between the coordinates of X 'and Y' and the blade profile sound power;

the fifth step comprises the following steps: designing a connecting line between the theoretical sound velocity points determined in the fourth step by adopting a quintic Bezier curve, wherein the coordinates, the slope and the curvature of the theoretical sound velocity points are known quantities; bezier curve general formula is

Starting point L₁The theoretical sound velocity point is the curve initial slope which is the straight line L₁L₂Slope, L₂The ordinate is obtained from the abscissa through the slope; l is₃The horizontal coordinate and the vertical coordinate of the point are input quantities, and L is changed₃The point horizontal coordinate and the point vertical coordinate enable the curvature of the theoretical sound velocity point and the curvature of the front edge point of the blade profile to meet the curvature invariant condition;

the sixth step comprises: designing two transition sections connecting the leading edge section and the suction surface/pressure surface of the blade profile by adopting a cubic Bezier curve, wherein L is₆L₇、L₈L₉The slope is respectively the same as the theoretical sound velocity point and the slope of the junction of the modified front edge and the blade profile, and L is adjusted₇、L₈Two pointsx coordinate, so that the curvatures of the two ends meet the curvature invariant condition;

the seventh step comprises: performing quasi three-dimensional Reynolds average N-S equation (RANS) numerical simulation on the front edge three-section design blade profile, adopting the same numerical simulation setting as the numerical simulation of the original blade profile in order to eliminate errors caused by grids or boundary conditions, and repeating the first step and the second step on the front edge three-section design blade profile to obtain an acoustic power result of the front edge three-section design blade profile;

the eighth step comprises: and evaluating the noise reduction benefit of the front edge three-section design blade profile, specifically, comparing the acoustic power result of the front edge three-section design blade profile with the acoustic power result of the original blade profile to obtain the noise reduction benefit of the front edge three-section design blade profile.