Open rotor and its stator blades, noise reduction method

Abstract

An open rotor and its stator blades are provided, along with a noise reduction method. The noise reduction method includes the following steps: making the stator blades into a swept shape, such that the sound pressure of the stator blades in at least a portion of the time domain can cancel out the sound pressure of the rotor blades in that portion of the time domain, thereby effectively reducing rotor-stator interference noise.

Description

Technical Field

[0001] This invention relates to the field of open rotors, and more specifically to the field of noise reduction for open rotors. Background Technology

[0002] Open rotors, also known as propfan engines, have blades exposed to the airflow, resulting in significant noise that requires effective control.

[0003] For example, US Patent 10502187B2 discloses a rotor blade in which fluid flows from the leading edge to the trailing edge. At least one actuator for generating an anti-noise signal is disposed on the rotor blade surface. The actuators are arranged and configured such that edge noise caused by the flow of the rotor blade is at least partially canceled out by the anti-noise signal, further eliminating edge noise caused by the flow of the rotor blade. However, this method requires additional attachments to the blade, which can affect the blade's operating efficiency.

[0004] For example, Chinese patent CN114856712A discloses a blade with a biomimetic tip and an open rotor equipped with the blade, wherein the outer edge surface of the blade tip is an arc-shaped curved surface. By setting a biomimetic wavy tip structure on the tip of the front rotor in the open rotor, the wavy tip structure can suppress the tip vortex of the front rotor and reduce interference with the rear rotor, thereby controlling the tip vortex intensity of the front rotor and significantly reducing noise during takeoff without sacrificing aerodynamic performance during takeoff and cruise. This method controls noise from the perspective of tip vortex, but the structural strength of the biomimetic structure is a significant issue. For open fans without an envelope casing, the risk of breakage is even greater, making it difficult to use in engineering applications. Summary of the Invention

[0005] One object of the present invention is to provide an open rotor noise reduction method that can effectively reduce noise.

[0006] The open rotor noise reduction method for achieving the above objective includes the following steps: making the stator blade a swept shape, such that the sound pressure of the stator blade in at least a portion of the time domain can cancel the sound pressure of the rotor blade in that portion of the time domain, thereby achieving noise reduction.

[0007] In one or more embodiments, the sweep profile is determined using simulation and / or experimental methods.

[0008] In one or more embodiments, the sweep profile is described using a relationship between blade height and sweep angle offset and / or blade height and bend angle offset.

[0009] In one or more embodiments, under this swept profile, the acoustic pressure cancellation region of the stationary blade and the moving blade is larger than the acoustic pressure superposition region of the stationary blade and the moving blade.

[0010] Another object of the present invention is to provide an open rotor stator blade, which is designed and obtained by using the above-described open rotor noise reduction method.

[0011] In one or more embodiments, the sweep angle offset of the stator blade's leading edge profile in the region below 55% of the blade height satisfies the following formula with respect to the blade height: R = -9080.3 x 2 +16837x-7804.35, where R is the relative leaf height and x is the relative sweep angle offset.

[0012] In one or more embodiments, the sweep angle offset of the leading edge profile of the stator blade in the region above 55% of the blade height satisfies the following formula with respect to the blade height: R = -29.563 x 2 +62.663x-32.105, where R is the relative leaf height and x is the relative sweep angle offset.

[0013] In one or more embodiments, the sweep angle offset of the stator blade's trailing edge profile below 55% of the blade height satisfies the following formula with respect to the blade height: R = 274.19x 2 -485.06x+214.9, where R is the relative leaf height and x is the relative sweep angle offset.

[0014] In one or more embodiments, the sweep angle offset of the stator blade's trailing edge profile at 55% of the blade height satisfies the following formula with respect to the blade height: R = -14.139 x 2 +29.023x-13.901, where R is the relative leaf height and x is the relative sweep angle offset.

[0015] In one or more embodiments, the bend angle offset of the stator blade and the blade height satisfy the following formula: R = -1.0802 t 3 -1.4633 t 2 -1.2015t+0.5099, where R is the relative blade height and t is the bend angle offset.

[0016] Another object of the present invention is to provide an open rotor including the above-described open rotor stator blades.

[0017] The above-mentioned open rotor noise reduction method adjusts the sweep shape of the stator blades, especially the sweep shape at the leading and trailing edges, and starts from the time-domain sound pressure signal of the noise to make the sound pressure phase of the rotor noise and the stator noise cancel each other in the time domain, thereby effectively reducing the rotor-stator interference noise. Attached Figure Description

[0018] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, wherein:

[0019] Figure 1 This is a structural diagram of an open rotor;

[0020] Figure 2 This is a schematic diagram of phase cancellation;

[0021] Figure 3 This is an external view of one embodiment of an open rotor stator blade;

[0022] Figure 4 This is a graph showing the relationship between the relative sweep angle offset of the local leading edge of the stator blade and the relative blade height;

[0023] Figure 5 This is a graph showing the relationship between the relative sweep angle offset of the local trailing edge of the stator blade and the relative blade height;

[0024] Figure 6 This is a graph showing the relationship between the bend angle offset of the stator blade and its relative blade height.

[0025] Figure 7 It is a noise directivity diagram. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0027] It should be noted that these and other accompanying drawings are merely examples and are not drawn to scale, and should not be construed as limiting the scope of protection of the present invention.

[0028] Open-rotor engines are a promising configuration for next-generation aero engines due to their high propulsion efficiency and low fuel consumption. Compared to traditional turbofan engines, open-rotor engines have no outer casing, allowing the blades to be directly exposed to the air, saving a significant amount of weight and drag, and resulting in a much higher bypass ratio than traditional turbofan engines.

[0029] However, the open rotor structure results in a significant aerodynamic noise problem – the high-speed rotating blades are directly exposed to the sound field, causing intense noise.

[0030] Rotation-to-stationary interference noise refers to noise caused by aerodynamic interference between rotating and stationary components. The periodic wakes generated by the rotating blades act on the stator blades, producing unsteady loads. These periodic unsteady loads generate sound waves, forming rotation-to-stationary interference noise.

[0031] The International Civil Aviation Organization (ICAO) is imposing increasingly stringent EPNL (Effective Partial Noise Limit) restrictions on aircraft noise, while traditional noise reduction methods face significant bottlenecks in open-type fans. Conventional noise reduction methods, such as applying acoustic liner, are difficult to implement due to the lack of installation space in open structures. Against this backdrop, blade sweep-out shapes have become the core technical approach for noise reduction in open-type fans.

[0032] Blade sweep deformation involves multiple disciplines such as strength and aerodynamics. How to achieve noise reduction design of stator blades based on sweep shape has become an urgent technical problem to be solved.

[0033] In their paper "Research on Low-Noise Design of a High-Bypass-Ratio Turbine Fan Engine" (Shanghai Acoustical Society, Institute of Acoustics, College of Physics and Engineering, Tongji University. Proceedings of the 3rd Shanghai-Xi'an Acoustical Society Conference, 2013: 159-162), Li Danwang et al. described a method for reducing the aerodynamic noise source intensity during the fan's transition from stationary to ambient noise. This method introduces a phase shift in the unsteady aerodynamic forces of the transition, and the tilting guide vane design is the main means of achieving this phase shift. As the sweep angle of the outer bypass duct (OGV) increases, the forward noise of the fan's transition from stationary to ambient noise first decreases and then increases, while the backward noise decreases.

[0034] Based on this research, this disclosure further proposes that by modifying the sweep structure design of the open rotor stator blades, especially the sweep design at the leading and trailing edges, the rotor noise and stator noise can be phase-cancelled in the time domain, thus meeting the technical requirements of noise reduction based on sound source for open fans.

[0035] Figure 1 The diagram shows the structure of an open rotor, including a moving vane 10 located on the axially front side and a stator vane 20 located on the axially rear side. The moving vane 10 generates a periodic wake and applies it to the stator vane 20, forming rotor-stator interference noise.

[0036] This open rotor noise reduction method adjusts the sweep profile of the stator blades 20, particularly the sweep profile along the leading and trailing edges, thereby altering the propagation curve of the sound pressure generated by the stator blades in the far field. This allows the sound pressure of the stator blades in at least a portion of the time domain to cancel out the sound pressure of the rotor blades in that portion of the time domain, thus achieving noise reduction. Figure 2 As shown, under this swept shape, the stationary blade can generate a state of sound pressure cancellation with the moving blade in as many time domains as possible, and the canceled sound pressure region achieves effective noise reduction.

[0037] exist Figure 2 In the figure, the vertical axis represents sound pressure. p (Pa), the horizontal axis represents time. T (s), representing the sound pressure radiating to the far field as time progresses. Sound pressure is the periodic change in pressure due to compression and expansion of various parts of the air medium during sound wave propagation. Pressure increases during compression and decreases during expansion; the difference between this pressure change and the static pressure is called sound pressure. Noise sources are non-steady-state signals and are time-dependent. For example, using... Figure 2 Taking the horizontal axis 0.0025s as an example, the time-domain signal shown by this red line reflects the change of the overall fan noise over time during this period.

[0038] The green bars represent the stator blades, i.e., the sound pressure level of the noise generated by the stator in one time domain, while the blue bars represent the rotor blades, i.e., the sound pressure level of the rotor in one time domain.

[0039] Open-type fan noise is the result of the superposition of rotor noise and stator noise. When the noise of both blades is positive or negative at the same time, the superimposed noise increases; if one is positive and the other is negative, the superimposed noise is lower than that of a single blade, thus achieving noise reduction. Figure 2 As shown in region A.

[0040] Since the amplitude of the sound pressure time-domain signal changes positively or negatively with time, as the sound radiates into the far field, the sound pressure of the stator blades in at least a portion of the time domain can cancel out the sound pressure of the rotor blades in the same portion of the time domain, i.e., exhibiting a positive and negative state. This causes the rotor noise and stator noise to cancel each other out in the time-domain signal, effectively reducing the total noise after superposition. Figure 2 As shown by the red curve in the middle.

[0041] Different stator blade sweep shapes result in different noise levels in different time domains. Therefore, by continuously optimizing and adjusting the stator blade sweep shape until the sound pressure cancels out, the noise can be reduced to the greatest extent.

[0042] In the design process of this noise reduction method, the total range of the sound pressure cancellation area between the stationary blade and the moving blade under the swept shape is made larger than the total range of the sound pressure superposition area between the stationary blade and the moving blade, so as to reduce noise as a whole.

[0043] The purpose of this swept-back shape is also to increase the total area of ​​phase cancellation and reduce the total area of ​​phase overlap throughout the entire time domain.

[0044] In some embodiments, the sweep profile of the stator blades is adjusted through numerical simulation and / or experimental methods until a sweep profile that meets the phase cancellation requirement is obtained, such as... Figure 3 As shown.

[0045] The sweep profile is described using the relationship between blade height at the leading and trailing edges and the sweep angle offset, and / or the blade height and the bend angle offset.

[0046] The physical units for blade height, sweep angle offset, and bend angle offset are meters (m). Sweep angle offset refers to... Figure 3 The horizontal offset of the leading edge 21 or trailing edge 22, and the angular offset refers to the circumferential (i.e., perpendicular to) the blade centerline. Figure 3 The offset (in the direction of the paper).

[0047] The sweeping shape of the blade can be determined from the leading edge 21, trailing edge 22, blade tip 23, pressure surface 24, and suction surface 25.

[0048] In some embodiments, the sweep angle offset of the portion of the blade leading edge curve below 55% of the blade height satisfies the formula R = -9080.3 x 2 +16837x-7804.35, where R is the relative leaf height and x is the relative sweep angle offset. The relative leaf height R refers to the normalized and scaled-down leaf height, with a relative leaf height of 1 at the leaf tip, 0 at the leaf root, and between 0 and 1 for the rest. The relative sweep angle offset x refers to the normalized and scaled-down sweep angle offset, where x is the ratio of the sweep angle offset at the current leaf height to the sweep angle offset at the leaf tip; that is, at the leaf tip, the relative sweep angle offset x is 1.

[0049] The leading edge curve of the blade is as follows Figure 4 As shown, the vertical axis represents the relative leaf height R, and the horizontal axis x represents the relative sweep angle offset. Specifically, the vertical axis at the leaf tip is 1, representing 100% leaf height, and the vertical axis at the leaf root is 0, representing 0% leaf height.

[0050] The vertical axis relative sweep angle offset is the relative value between the sweep angle offset at a certain blade height on the leading edge profile and the sweep angle offset at the blade tip. For example... Figure 3 At the leading edge M, the relative blade height R is 0.48 and the relative sweep angle offset x is 0.92375.

[0051] The sweep angle offset above 55% of the blade height satisfies the formula R = -29.563 x. 2 +62.663x-32.105, this part of the leading edge profile is also like... Figure 4 As shown.

[0052] Figure 5 The relationship between the sweep angle offset and leaf height in a localized region of the blade trailing edge is shown. The sweep angle offset of the blade trailing edge curve below 55% of the leaf height satisfies the formula R = 274.19x. 2 -485.06x + 214.9, the sweep angle offset of the blade trailing edge profile above 55% of the blade height satisfies the following formula with respect to the blade height: R = -14.139 x2 +29.023x-13.901, where R is the relative blade height and x is the relative sweep angle offset. For example... Figure 3 At the trailing edge N, the blade height R is 0.8 and the relative sweep angle offset x is 0.9097.

[0053] In some embodiments, the leaf bends from 48% of its height.

[0054] In some embodiments, the bend angle offset and blade height satisfy the formula R = -1.0802 t 3 -1.4633 t 2 -1.2015t+0.5099, where R is the relative blade height and t is the bend angle offset. The trailing edge profile is as follows: Figure 6 As shown, for example, at 60% leaf height, R is 0.6, and the bend angle offset is -0.08. The unit of bend angle offset is meters (m).

[0055] Both relative blade height and relative sweep angle offset are dimensionless quantities.

[0056] This method also balances aerodynamic efficiency and strength requirements. When determining the sweep profile of the stator blades, both aerodynamic efficiency and strength requirements are considered.

[0057] Figure 7 The diagram shows the far-field noise directivity before and after adopting the above-mentioned swept-out shape. The horizontal axis is the pointing angle, and the vertical axis is the sound pressure level (SPL), in decibels. It can be seen that after adopting the swept-out shape, the SPL in some areas is reduced, indicating that the noise is reduced.

[0058] Based on the above introduction of the noise reduction method for open rotors, it can be understood that a stator blade designed using this noise reduction method can, when combined with the rotor blade, have a stator blade with a swept-forward and trailing edge shape. In this way, the sound pressure of the stator blade in at least part of the time domain can cancel out the sound pressure of the rotor blade in the same time domain, thereby effectively reducing the rotor-stator interference noise.

[0059] Reference Figures 4 to 6 Understanding this, the sweep angle offset of the leading edge profile of the stator blade in the region below 55% of the blade height satisfies the following formula with respect to the blade height: R = -9080.3 x 2 +16837x-7804.35, where R is the relative leaf height and x is the relative sweep angle offset.

[0060] The sweep angle offset of the leading edge profile of the stator blade in the region above 55% of the blade height satisfies the following formula with respect to the blade height: R = -29.563 x 2 +62.663x-32.105, where R is the relative leaf height and x is the relative sweep angle offset.

[0061] The sweep angle offset of the trailing edge profile of the stator blade below 55% of the blade height satisfies the following formula with respect to the blade height: R = 274.19x 2 -485.06x+214.9, where R is the relative leaf height and x is the relative sweep angle offset.

[0062] For the stator blade, the sweep angle offset of the trailing edge profile above 55% of the blade height satisfies the following formula with respect to the blade height: R = -14.139 x 2 +29.023x-13.901, where R is the relative leaf height and x is the relative sweep angle offset.

[0063] The angular offset of the stator blade and the blade height satisfy the following formula: R = -1.0802 t 3 -1.4633 t 2 -1.2015t+0.5099, where R is the relative blade height and t is the bend angle offset.

[0064] The aforementioned stator blades, through a sweep design, enable the rotor noise and stator noise to cancel each other out in the time domain signal, effectively reducing the total noise after superposition.

[0065] In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0066] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0067] Furthermore, this application uses specific terms to describe embodiments of the application. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0068] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any variations and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, fall within the protection scope defined by the claims of the present invention.

Claims

1. A noise reduction method for an open rotor, wherein the open rotor comprises moving blades and stator blades, characterized in that, Includes the following steps: The stator blade is made into a swept shape, under which the sound pressure of the stator blade in at least a part of the time domain can cancel the sound pressure of the moving blade in the same part of the time domain, so as to achieve noise reduction. The sweep profile is described by the relationship between the blade height and sweep angle offset at the leading and trailing edges and / or the blade height and bend angle offset; under this sweep profile, the sound pressure cancellation area between the stationary blade and the moving blade is larger than the sound pressure superposition area between the stationary blade and the moving blade. Swing angle offset refers to the horizontal offset of the leading or trailing edge, while bend angle offset refers to the circumferential offset of the blade centerline.

2. The noise reduction method for an open rotor as described in claim 1, characterized in that, The sweep profile is determined using simulation and / or experimental methods.

3. An open rotor stator blade, characterized in that, The stator blades were designed using the open rotor noise reduction method as described in any one of claims 1-2.

4. The open rotor stator blade as described in claim 3, characterized in that, The bending angle offset of the stator blade and the blade height satisfy the following formula: R=-1.0802 t 3 -1.4633 t 2 -1.2015t+0.5099, Where R is the relative blade height and t is the bend angle offset.

5. An open rotor, characterized in that, Including the open rotor stator blades as described in any one of claims 3-4.

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