Variable blade profile noise control system and method

Abstract

The invention provides a variable blade type noise control system which comprises a shape memory alloy fan blade, a distance high-frequency heating device and a controller, and the shape memory alloy fan blade is arranged on a fan disc and supported by a low-pressure shaft; the distance high-frequency heating equipment is used for providing distance high-frequency heating for the low-pressure shaft; the controller is used for recognizing the flight stages of the aero-engine and is in signal connection with the air high-frequency heating equipment so as to provide different heating instructions for the air high-frequency heating equipment according to different flight stages, and then the shape memory alloy fan blades are heated to change the blade types by means of the memory characteristics. The invention further provides a variable blade noise control method. The system and the method can give consideration to the working efficiency of the blade and noise control in different flight stages.

Description

Technical Field

[0001] The present invention relates to the field of aero engines, and in particular to the field of noise control. Background Art

[0002] With the increase in air traffic, the high noise problem of commercial aircraft has attracted more and more attention. The International Civil Aviation Organization (ICAO) requires in its latest fifth-stage noise airworthiness regulations that the cumulative noise generated by aircraft near airports should be further reduced by 7EPNdB (based on the effective perceived noise level) compared to the fourth stage. Since aircraft engine noise accounts for a large proportion in aircraft airworthiness noise assessment, the low-noise design of aircraft engines faces more severe challenges.

[0003] For civil large aircraft turbofan engines, the sound sources mainly include four components: fan / compressor noise, combustion noise, turbine noise and exhaust noise. As the bypass ratio design of turbofan engines continues to increase, the corresponding engine exhaust speed continues to decrease, so compared with the noise generated by the fan / compressor, the exhaust gradually becomes smaller. Therefore, for modern high bypass ratio turbofan engines, the fan / compressor noise contributes the most to the total noise sound pressure level.

[0004] Therefore, effectively reducing fan noise is of great significance for aircraft airworthiness certification. There are currently two ways to limit fan noise: active noise reduction and passive noise reduction. Active noise reduction is achieved through the reasonable design of fan blade shape, that is, changing the sweep angle to reduce the sound radiation of the sound source. Passive noise reduction is to limit the propagation of sound energy by installing sound lining, as shown in Table 1.

[0005] Table 1 Methods for achieving noise reduction of aircraft engine fans

[0006]

[0007] The main target of fan noise reduction is rotational-static interference noise, because it accounts for a large contribution to the total fan noise. Both active noise reduction and passive noise reduction methods are applicable. However, when the fan speed is too high and the blade tip becomes supersonic, shock wave noise begins to dominate. Therefore, there have been many studies on shock wave noise suppression in recent years, mainly for active noise reduction, that is, optimizing the swept structure of fan blades.

[0008] Rotor-static interference noise appears at integer multiples of the blade passing frequency (BPF) in the noise spectrum, and therefore becomes pure tone noise. Shock wave noise appears at BPF / B in the noise spectrum and is generally less than integer multiples of BPF (B is the number of fan rotor blades). The airworthiness noise assessment is aimed at three airworthiness operating conditions: approach, flyover, and sideline. Each operating condition corresponds to a different rotation speed, that is, a different BPF.

[0009] In summary, at present, the key technical difficulties of noise control include the following aspects.

[0010] First of all, the active noise reduction of the engine is mainly focused on the research of the noise of the rotor-static interference, which is mainly related to the sweep design of the fan blades. The blade design is a solution to a multidisciplinary optimization problem. The change of sweep not only affects the noise design, but also affects the working efficiency of the fan. The sweep shape of the fan also affects the aerodynamic efficiency and fuel consumption of the aircraft engine, and often in the optimization design of the fan blades. Secondly, for passive noise reduction, the design of the sound lining can only take into account the noise suppression of a specific frequency band, but the airworthiness noise often requires taking into account three working conditions, which is difficult to implement. Since this technology is multidisciplinary coupling, this further increases the difficulty of implementing active noise control. Finally, the existence of airworthiness noise regulations requires that the low-noise design of the fan should take into account three working conditions as much as possible, but the current low-noise sweep design of the fan can only take one main BPF as the noise reduction target each time, and take into account other frequency noises as much as possible through forward optimization iterative design to obtain a local optimal solution for the total noise. Such noise reduction effect is greatly discounted. Summary of the invention

[0011] An object of the present invention is to provide a variable blade noise control system that can take into account both blade operating efficiency and noise control in different flight phases.

[0012] It includes shape memory alloy fan blades, air-to-air high-frequency heating equipment and a controller. The shape memory alloy fan blades are arranged on a fan disk and supported by a low-pressure shaft; the air-to-air high-frequency heating equipment is used to provide air-to-air high-frequency heating to the low-pressure shaft; the controller is used to identify the flight stage of the aircraft engine and is connected to the air-to-air high-frequency heating equipment by signal to provide different heating instructions to the air-to-air high-frequency heating equipment according to different flight stages, thereby causing the shape memory alloy fan blades to be heated and change their blade shape by virtue of their memory characteristics.

[0013] In one or more embodiments, the air-insulated high-frequency heating device includes a power supply, a frequency conversion control unit and an electromagnetic coil, and the electromagnetic coil is arranged on the low-pressure shaft.

[0014] In one or more embodiments, the power supply is an external power supply or a power supply provided by the aircraft engine avionics system.

[0015] In one or more embodiments, part of the shape memory alloy fan blade is made of Ni-Ti-Hf-Zr alloy.

[0016] In one or more embodiments, the shape memory alloy fan blade is configured to have different prefabricated blade profiles at different temperatures.

[0017] In one or more embodiments, the flight phase includes a take-off phase, a cruising phase, and a landing phase.

[0018] Another object of the present invention is to provide a variable blade noise control method, which is performed using the above-mentioned system. The method includes the following steps: determining the design adaptation blade shape of the fan blade for different flight stages of the aircraft engine; pre-forging the shape memory alloy fan blade into a prefabricated blade shape consistent with the design adaptation blade shape at different temperatures; determining the flight stage of the aircraft engine; and causing the high-frequency heating device in the air to supply different amounts of heat to the low-pressure shaft according to the different flight stages, so that the shape memory alloy fan blade is heated and the shape memory alloy fan blade is deformed to the prefabricated blade shape at this temperature by virtue of its memory characteristics.

[0019] In one or more embodiments, the shape memory alloy fan blade includes a take-off design adapted blade profile, a cruise design adapted blade profile, and a landing design adapted blade profile.

[0020] In one or more embodiments, the designed adapted airfoil is obtained using simulation and / or experimental methods.

[0021] The above-mentioned variable blade noise control system and method make use of the characteristics of shape memory alloy fan blades. Through pre-designing a specific prefabricated blade shape that takes into account both blade efficiency and noise control, the blade shape itself is adaptively changed in different flight stages, thereby achieving noise reduction control in multiple flight stages while taking into account the blade working efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and other features, properties and advantages of the present invention will become more apparent through the following description in conjunction with the accompanying drawings and embodiments, in which:

[0023] Figure 1 It is a schematic diagram of the structure of aircraft engine components;

[0024] Figure 2 It is a schematic diagram of the curved and swept combined blade shape;

[0025] Figure 3 It is a schematic diagram of the principle of high-frequency heating in air;

[0026] Figure 4 is a schematic diagram of an embodiment of an aircraft engine fan blade and a fan disk;

[0027] Figure 5 It is a schematic diagram of the variable sweep shape of the fan blade;

[0028] Figure 6 It is a schematic diagram of the result of the variable blade noise control system;

[0029] Figure 7is a flow chart of the variable blade noise control method;

[0030] Figure 8 It is a flow chart of a specific embodiment of the variable blade noise control method. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with specific embodiments and drawings. More details are elaborated in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in a variety of other ways different from the description herein. Those skilled in the art can make similar generalizations and deductions based on actual application situations without violating the connotation of the present invention. Therefore, the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0032] It should be noted that these and other subsequent drawings are only examples and are not drawn to scale, and should not be used to limit the actual scope of protection required by the present invention.

[0033] The active noise reduction of the engine mainly focuses on the study of the noise of the rotor-static interference, which is mainly related to the swept design of the fan blades. Existing literature shows that changes in the swept structure will affect the generation and transmission of noise. The "Noise Reduction Design of Fan Shock Wave Noise of a High Bypass Ratio Turbofan Engine" (Aerospace Science and Technology, 2019, 30(05)) records the influence of the swept modification on the fan shock wave noise. On the basis of the baseline fan blade shape, a modified fan blade was designed by increasing the forward sweep of the fan blade tip and widening the middle and lower part and root of the fan blade. The one-dimensional propagation characteristics of the leading edge separation shock wave noise of the baseline fan and the modified fan were compared and analyzed. The results show that under the takeoff condition and maximum climb condition of standard atmospheric conditions at sea level, the shock wave noise level of the modified fan is lower than that of the baseline fan blade shape, which proves that the swept modification design of the fan blade shape helps to reduce the fan shock wave noise. However, the swept structure also affects the working efficiency of the fan.

[0034] The variable blade noise control system disclosed in the present invention divides the flight phases into different phases and selectively changes the swept blade profile of the fan blades to achieve noise control without affecting the fan's operating efficiency.

[0035] Figure 1 The overall structure of the aircraft engine is shown, which can be roughly divided into fan blades 1A, a low-pressure compressor 1B, a high-pressure compressor 1C, a combustion chamber 1D, a turbine 1E, a low-pressure shaft 2A and a high-pressure shaft 2B, and the O1 direction is the axial direction of the aircraft engine. Figure 2 A schematic diagram of the swept-bend combined blade shape is given, ignoring the influence of swirl. Figure 2The stator blades shown are placed parallel to the main flow, from the blade root to the blade tip. When the leading edge of the blade changes downstream with increasing radial position, the blade is swept back and the sweep angle is positive; conversely, the blade is swept forward and the sweep angle is negative. When the blade changes along the circumferential phase angle with increasing radial position, it is called a curved blade, and the curved angle is positive when it is in the same direction as the fan rotor rotation.

[0036] The variable blade noise control system described in this application refers to Figures 3 to 6 Understanding, including Figure 4 and Figure 5 The shape memory alloy fan blades, high frequency heating equipment and controller are shown.

[0037] The fan 10 includes shape memory alloy fan blades 11 and a fan disk 12, which are supported by a low-pressure shaft 13. The shape memory alloy fan blades 11 are meshed with the fan disk 12 through a mortise and tenon structure, and the blades and the disk are in contact, which ensures that heat can be transferred to the blade disk through the low-pressure shaft, and further transferred to the fan blades 11.

[0038] Part of the fan blade 11 is made of shape memory alloy (SMA), which exhibits shape memory effect and superelasticity due to the presence of different crystal forms such as martensite and austenite at different temperatures. With the help of the memory function of the shape memory alloy, a prefabricated blade shape can be forged at different temperatures in advance, and when the shape memory alloy is at the temperature again, it can actively deform into the prefabricated blade shape.

[0039] In some embodiments, part of the material of the shape memory alloy fan blade is preferably forged from Ni-Ti-Hf-Zr alloy, which exhibits shape memory effect at 700°C. The fan is a cold end component and does not require too high a temperature for shape changes, so Ni-Ti-Hf-Zr alloy is feasible. Different shape designs can be forged at different temperatures at a preset temperature to achieve multi-level adjustable shape at different engine operating states and temperatures.

[0040] It should be noted that not all fan blades are made of shape memory alloys. Considering the structural strength of the blades, materials such as titanium alloys that can increase strength are used in places such as the leading edge of the blades to ensure the safety of the blades.

[0041] The high frequency heating device 20 is used to provide high frequency heating to the low pressure shaft 13. In some embodiments, the high frequency heating device 20 includes a power supply 21, a frequency conversion control unit 22 and an electromagnetic coil 23, and the electromagnetic coil 23 is arranged on the low pressure shaft 13, such as Figure 6The controller (not shown) is used to identify the flight stage of the aircraft engine and is connected to the remote high-frequency heating device signal to provide different heating instructions to the remote high-frequency heating device according to different flight stages, thereby causing the shape memory alloy fan blades to be heated and change the blade shape by virtue of the memory characteristics.

[0042] Reference for high frequency heating in air Figure 3 As shown in the schematic diagram, a strong magnetic flux H with instantaneous polarity change is generated in the high-frequency induction coil. When the metal to be heated is placed in the high-frequency coil, the magnetic flux will penetrate the entire heated metal object. A corresponding strong eddy current is generated inside the induction heated object in the opposite direction to the induced current I. Because there is resistance in the induction heated metal, strong Joule heat energy is generated, causing the temperature of the induction heated object to increase rapidly, thereby achieving the purpose of heat treatment.

[0043] The frequency conversion control unit 22 can control the eddy current generated in the electromagnetic coil 23 and convert it into heat energy to heat the fan unit. Since the fan blade 11 has a prefabricated blade shape that has been forged through the memory alloy material in advance, the memory alloy can change into different shapes at different working temperatures. The shape of the memory metal can be indirectly controlled by frequency conversion temperature control.

[0044] For example, high-frequency heating in the air can be temperature controlled by designing a PID controller to control the input current size (duty cycle), thereby controlling the bending and sweeping blade shape of the blade at different temperatures.

[0045] As described above, the low-pressure shaft of the fan blade is heated in the air with high frequency through the power supply device, and the heat is transferred from the shaft to the fan disk, and then to the fan blades tenoned with the fan disk, so that the heat can be quickly heated and transferred. Figure 5 Different curved and swept shapes are shown, which are two adaptive blade shapes forged at different temperatures before the shape memory alloy fan blades work. During takeoff and landing, the blade curved and swept shape 3C with optimal noise reduction can be used, and the fan blade curved and swept shape 3D with more "economical" fuel saving can be considered in high-altitude cruising. In the actual operation of the fan blades, the fan blades can smoothly switch between the two adaptive blade shapes under different temperature changes by virtue of the memory characteristics.

[0046] The adaptive blade shape formed by the blades when finally heated is consistent with the designed adaptive blade shape of the fan blades for different flight stages of the aircraft engine. The designed adaptive blade shape is obtained through methods such as simulation and / or testing. The obtained designed adaptive blade shape has been verified in advance and meets the noise reduction and aerodynamic requirements, and is the optimal solution for this flight stage.

[0047] The flight phase includes the take-off phase, the cruise phase and the landing phase. Accordingly, the shape memory alloy fan blades include the take-off design adaptation blade type, the cruise design adaptation blade type and the landing design adaptation blade type. For example, the approach phase indicates the state of the aircraft preparing to land on the runway, the overflight phase indicates the state of the aircraft taking off and rolling for a distance, and the sideline phase indicates the state of the aircraft with the highest noise level after leaving the ground. Different aircraft have different airworthiness standards for each phase.

[0048] For example, since the take-off phase is short, the effect of blade sweep on fuel consumption can be ignored. The main purpose at this stage is to reduce noise. Therefore, fluid mechanics simulation methods and / or experiments are used to obtain the appropriate blade shape for the take-off phase to solve the noise problem at the take-off phase. For example, Figure 5 The blade swept blade type 3C is shown. The main goal of the aircraft's cruise phase is to save fuel, and the cruise phase accounts for about 80% of the entire route. In traditional noise control, noise reduction is performed through the skin at this stage, so by making the fan blade swept Figure 5 The fan blade swept blade profile 3D shown is the optimal aerodynamic shape and can achieve significant benefits.

[0049] Before takeoff, in order to ensure that the fan blades work in the optimal noise reduction shape, the low-pressure shaft 13 needs to be heated by high-frequency heating equipment 20. The heating power supply 21 can be an external power supply or the power supply of the aircraft engine avionics system.

[0050] After takeoff, when the aircraft climbs to the maximum cruising state, the low-pressure shaft 13 is still temperature-controlled by the high-frequency heating device 20, so that the fan sweep shape is transformed into an "economical and fuel-efficient" swept blade 3D, and runs through the entire high-altitude cruising range. In the air, the power supply can be switched, such as switching from the self-contained power supply to the power supply of the aircraft engine avionics system.

[0051] Finally, some time before it is determined that landing is necessary, the high-frequency heating is turned on in advance to heat the low-pressure shaft 13, so that it can be transformed into the blade bending and sweeping working state 3C which is most suitable for the approach airworthiness noise. Only after the blade deformation is completed can the approach and landing be carried out, which greatly reduces the noise of the aircraft engine.

[0052] Combined with the above introduction to the variable blade noise control system, a variable blade noise control method can also be understood, which includes the following steps: determining the design adaptation blade shape of the fan blade for different flight stages of the aircraft engine; pre-forging the shape memory alloy fan blade into a prefabricated blade shape consistent with the design adaptation blade shape at different temperatures; determining the flight stage of the aircraft engine; according to different flight stages, the high-frequency heating equipment in the air supplies different heat to the low-pressure shaft, so that the shape memory alloy fan blade is heated and heated, and the shape memory alloy fan blade is deformed to the prefabricated blade shape at this temperature by virtue of its memory characteristics.

[0053] Figure 8 A specific embodiment of the control method is shown. First, the controller determines the flight state and divides the flight state into 1 take-off state, 2 cruising state and 3 landing state.

[0054] When it is determined to be in the take-off state, the low-pressure shaft is heated using an air-insulated high-frequency heating device. After heating to a predetermined temperature and stabilizing, it is determined whether the fan blades are in the optimal noise suppression curved swept shape design. If so, the airworthiness noise requirements are met and the aircraft is ready to take off; if the fan blade shape is not the optimal design adaptation blade shape, the temperature is continued to be adjusted, and the heat received by the blade is adjusted again until the blade shape is a prefabricated blade shape consistent with the design adaptation blade shape.

[0055] When it is determined that the fan is in a cruising state, the fan blades adjust their shape under the control of the heat supplied by the air-to-air high-frequency heating device in the cruising state. When the temperature stabilizes at a predetermined temperature, it is determined whether the fan blades are in the optimally designed adaptive blade shape at that temperature. If so, the blade shape at this time is in a fuel-saving state. If not, the air-to-air high-frequency heating device needs to change the heat supply, such as using a PID controller to control the input current to adjust the temperature, until the fan blades are in the optimally designed adaptive blade shape in the cruising state.

[0056] When it is determined to be in the landing state, before approaching, the low-pressure shaft is heated in advance using a high-frequency heating device in the air. After the blades are heated to a predetermined temperature and stabilized, it is determined whether the fan blades are in the optimal design and adapted blade shape. If they are satisfied, it means that the noise meets the requirements and you can prepare for landing; if not, the high-frequency heating device is used to adjust the heat supply until the fan blades meet the landing state design and adapted blade shape.

[0057] The above-mentioned variable blade noise control method comprehensively considers the aerodynamic noise reduction method of aircraft engine fan blades and the deformation characteristics of memory materials. It can take into account the various requirements for airworthiness noise and economic cruise in the take-off, cruise and landing stages, and is designed to meet the two blade shapes and control them for different working conditions. Combined with the deformation characteristics of shape memory alloys, temperature control is carried out through high-frequency heating in the air, and the memory characteristics of shape memory alloys are used to restore to the designed prefabricated blade shape, so that the fan blades can be adjusted in multiple stages for multiple working conditions during the flight, closely combining the needs of noise and economy, fully exploring the needs, and maximizing work efficiency. In addition, the manufacturing process, PID control, high-frequency heating and other technologies of blades are already very mature, so this method is feasible.

[0058] The present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or multiple times in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0059] Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope defined by the claims of the present invention.

Claims

1. Variable blade noise control system, characterized in that: include: Shape memory alloy fan blades are disposed on the fan disk and supported by the low-pressure shaft; A high-frequency heating device is used to provide high-frequency heating to the low-pressure shaft; as well as The controller is used to identify the flight stage of the aircraft engine and is connected to the signal of the remote high-frequency heating device to provide different heating instructions to the remote high-frequency heating device according to different flight stages, thereby causing the shape memory alloy fan blades to be heated and change the blade shape by virtue of the memory characteristics.

2. The variable blade noise control system according to claim 1, characterized in that: The air-insulated high-frequency heating device comprises a power supply, a frequency conversion control unit and an electromagnetic coil, and the electromagnetic coil is arranged on the low-pressure shaft.

3. The variable blade noise control system according to claim 2, characterized in that: The power supply is an external power supply or a power supply provided by the aircraft engine avionics system.

4. The variable blade noise control system according to claim 1, characterized in that: Part of the material of the shape memory alloy fan blade is Ni-Ti-Hf-Zr alloy.

5. The variable blade noise control system according to claim 1, characterized in that: The shape memory alloy fan blade is configured to have different prefabricated blade profiles at different temperatures.

6. The variable blade noise control system according to claim 1, characterized in that: The flight phases include a take-off phase, a cruising phase and a landing phase.

7. A variable blade noise control method, characterized in that: Using the system as described in any one of claims 1 to 6, the method comprises the following steps: Determine the design and adaptation of fan blades for different flight phases of aircraft engines; Pre-forging the shape memory alloy fan blades into prefabricated blade shapes consistent with the designed adaptation blade shape at different temperatures; Determine the phase of flight that an aircraft engine is in; According to the different flight stages, the high-frequency heating device in the air supplies different amounts of heat to the low-pressure shaft, so that the shape memory alloy fan blades are heated and heated. The shape memory alloy fan blades are deformed to the prefabricated blade shape at the temperature due to their memory characteristics.

8. The variable blade noise control method according to claim 7, characterized in that: The shape memory alloy fan blades include a take-off design adapted blade shape, a cruise design adapted blade shape and a landing design adapted blade shape.

9. The variable blade noise control method according to claim 7, characterized in that: The designed adapted airfoil is obtained by using simulation and / or experimental methods.

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