Frequency spectrum characteristic adjustable ducted propeller and frequency spectrum characteristic regulation and control method thereof

Abstract

The invention provides a ducted propeller with adjustable spectrum characteristics and a spectrum characteristic regulation and control method thereof, and belongs to the field of propellers, the ducted propeller comprises a conduit, a propeller hub, blades and a jet mechanism, the propeller hub is arranged in the center of the conduit; the blades are axially distributed on the propeller hub around the guide pipe and axially rotate relative to the guide pipe along with the propeller hub, and gaps are reserved between blade tips of the blades and the inner wall of the guide pipe; a plurality of jet holes are formed in the inner wall of the guide pipe around the axial direction of the guide pipe and jet towards the gap at the same time; the jet mechanism is used for inputting jet media into the jet holes; jet flow is jetted to the gap between the blade tip and the inner wall of the guide pipe through the jet flow mechanism, gap flow is directly interfered, line spectrum noise superposition at the blade frequency is reduced, radiation noise of a propulsion system can be remarkably reduced, the method is particularly suitable for the high-navigational-speed working condition of a ship, the sound stealth performance is improved, and the ship is prevented from being recognized by sonar.

Description

Technical Field

[0001] This invention relates to the field of propeller technology, and in particular to a ducted propeller with adjustable spectral characteristics and a method for adjusting its spectral characteristics. Background Technology

[0002] Propulsion system noise is one of the three major noise sources of ships. In the frequency domain, propulsion system noise mainly includes line spectrum noise and broadband noise. Line spectrum noise is the primary target for sonar identification and a key area for optimization in ship design. At medium to high speeds, propulsion system noise increases significantly with propeller speed, greatly determining the overall radiated noise level of the ship.

[0003] Using a suitable number of propellers instead of a conventional single propeller is a feasible technical approach for novel underwater propulsion systems. CV204415693U discloses an asymmetric rotating blade propulsion boat, comprising a hull, a left propeller, a right propeller, and a control system. The left and right propellers, with identical structures, parameters, and operating principles, are symmetrically mounted on the left and right sides of the hull. Each propeller includes an engine, a reducer, a main shaft, a turntable, a guide shield, a central half-tooth gear, and two, three, or four rotating blades. The ducted propeller requires less thrust per propeller, allowing for the use of smaller diameter and lower rotational speed propellers, resulting in lower noise per propeller. Compared to a single propeller, the ducted propeller offers higher propulsion efficiency, higher reliability, and better acoustic performance.

[0004] For ducted propellers, since there is a blade tip gap between the blade and the inside of the duct, the line spectrum noise of the propeller blade may be superimposed at the blade passing frequency (referred to as blade frequency) of the propeller, thus affecting the acoustic performance of the propulsion system. Therefore, how to reduce the blade frequency spectrum characteristics of the propulsion system has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention proposes a ducted propeller with adjustable spectral characteristics and a method for controlling its spectral characteristics, in order to solve the problem of how to reduce the blade frequency spectral characteristics of the propulsion system.

[0006] The technical solution of the present invention is implemented as follows: The present invention provides a duct propeller with adjustable spectrum characteristics, including a duct, a hub, blades, and a jet mechanism. The hub is located at the center of the duct; a plurality of blades are arranged on the hub around the duct axis, and the blades rotate with the hub relative to the duct axis, with a gap between the blade tips and the inner wall of the duct; a plurality of jet holes are opened on the inner wall of the duct around the duct axis, and the plurality of jet holes simultaneously spray jets toward the gap; the jet mechanism is used to input the jet medium into the plurality of jet holes.

[0007] Based on the above technical solutions, the preferred embodiment also includes stator blades, with a plurality of stator blades arranged axially around the duct between the propeller hub and the inner wall of the duct, and the two ends of the stator blades being connected between the outer peripheral wall of the propeller hub and the inner peripheral wall of the duct, respectively.

[0008] In a further preferred embodiment, along the direction of water flow into and out of the duct, several stator blades are arranged in front of several blades, and several jet holes are arranged between the stator blades and the blades.

[0009] Even more preferably, the number of both the propeller blades and the stator blades is a prime number.

[0010] Based on the above technical solutions, preferably, it also includes a conveying ring and a conveying pipe; along the direction of water flow in and out of the conduit, the conveying ring is set on the end face of the water inlet end of the conduit, and the conveying ring is connected to the jet mechanism; several conveying pipes are buried inside the conduit wall, one end of the conveying pipe is connected to the jet hole, and the other end of the conveying pipe extends along the conduit axis toward the conveying ring and passes through the conduit wall to connect with the conveying ring.

[0011] Based on the above technical solutions, preferably, the inner wall of the conduit is provided with a step around the conduit axis, and several jet holes are opened around the side of the step.

[0012] On the other hand, the present invention also provides a method for controlling the spectral characteristics of a duct propeller, which uses the above-mentioned spectral characteristic adjustable duct propeller and controls the spectral characteristics of the duct propeller by changing the jet velocity.

[0013] Based on the above technical solutions, preferably, the jet velocities of the jets in several jet holes are the same, and the jet velocities are described in the form of sine waves or cosine waves.

[0014] More preferably, when the amplitude of the jet velocity waveform is increased, the amplitude of the spectral characteristics of the duct propeller increases and the amplitude decreases; when the amplitude of the jet velocity waveform is decreased, the amplitude of the spectral characteristics of the duct propeller decreases; when the amplitude of the jet velocity waveform is increased, the amplitude of the spectral characteristics of the duct propeller increases and the amplitude decreases; when the amplitude of the jet velocity waveform is decreased, the amplitude of the spectral characteristics of the duct propeller decreases.

[0015] More preferably, when the vehicle is traveling at a speed of 3 to 5 knots, the inner diameter of the duct is 100 to 300 mm, the propeller speed is 3 to 5 rps, and the gap width is 3 to 5 mm, the jet velocity of the jet ejected from the jet hole is 1 to 3 m / s.

[0016] The duct propeller with adjustable spectral characteristics and its spectral characteristic modulation method of the present invention have the following advantages over the prior art: (1) The present invention sprays jets into the gap between the blade tip and the inner wall of the duct through a jetting mechanism, directly interfering with the flow in the gap, reducing the superposition of line spectrum noise at the blade frequency, which can significantly reduce the radiation noise of the propulsion system. It is especially suitable for high-speed operation of ships, improves acoustic stealth performance, and avoids being identified by sonar.

[0017] (2) By changing the jet velocity, for example, by using a sine wave or a cosine wave, the present invention can dynamically adjust the spectral characteristics of the propeller. This adjustability allows for optimization of noise control based on parameters such as the vehicle speed and propeller speed, thereby improving the system's adaptability and maintaining a low noise level under different operating conditions.

[0018] (3) The design of the ducted propeller combines the prime number of stator blades and prime blades, which reduces acoustic modes and flow symmetry, thereby reducing turbulence and vibration. In addition, the integrated design of the jet mechanism with the delivery ring and delivery pipe ensures efficient delivery of the jet medium, enhances the stability and durability of the overall structure, and maintains high propulsion efficiency. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a cross-sectional schematic diagram of the duct propeller of the present invention; Figure 2 This is a comparison chart of the curve changes of three different jet velocities used in the duct propeller of the present invention; Figure 3 This is a schematic diagram of the spectral characteristics of the ducted propeller of the present invention when it is not using a jet flow. Figure 4 The jet velocity of the duct propeller of this invention v 1 or v Schematic diagram of spectral characteristics under 3 states; Figure 5 The jet velocity of the duct propeller of this invention v Schematic diagram of spectral characteristics under state 2; Figure 6 This is a simulation comparison diagram of the ducted propeller of the present invention using a jet flow state and not using a jet flow state.

[0021] In the diagram: 1. Conduit; 11. Jet orifice; 12. Step; 2. Hub; 3. Blade; 4. Jet mechanism; 5. Stator blade; 6. Transport ring; 7. Transport pipe. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] like Figure 1 As shown, the present invention provides a ducted propeller with adjustable spectral characteristics, comprising a duct 1, a hub 2, blades 3, and a jet mechanism 4.

[0024] Among them, the duct 1 is one of the main components of the ducted propeller. It wraps the blade 3 in an approximately cylindrical or annular channel. Its functions include changing the inflow, improving propulsion efficiency, and generating a flow field that interacts with the blade tip gap and the inner wall of the duct.

[0025] The hub 2 is located at the center of the duct 1, and several blades 3 are axially arranged around the duct 1 on the hub 2. The blades 3 rotate with the hub 2 relative to the duct 1, thereby generating propulsion. There is a gap 101 between the blade tip of the blade 3 and the inner wall of the duct 1. This gap 101 is the key area that causes typical blade frequency line spectrum noise. Therefore, blade tip leakage and vortex shedding are one of the main sources of line spectrum noise.

[0026] A plurality of jet holes 11 are axially formed around the inner wall of the duct 1, and jets are simultaneously ejected from the jet holes 11 toward the gap 101. The jet mechanism 4 is used to input the jet medium into the jet holes 11. The jet ejected from the inner wall of the duct 1 can directly enter the blade tip gap 101 and interact with the gap flow, thereby changing the active fluid intervention from "far-field" control, such as the wake control of the trailing edge of the blade, to "near-field / gap" direct intervention, which is beneficial to changing the local vortex structure, suppressing vortex convergence, or changing the superposition of coherent noise. Simultaneous injection through multiple jet orifices 11 can create the desired flow disturbance pattern in the circumferential direction, altering the phase and amplitude superposition of the propeller blade frequency spectrum. The principle is as follows: injecting a jet at the "upstream source" of the blade tip vortex formation directly disturbs the flow in the blade tip gap 101. The jet itself carries a specific vorticity, which is determined by its velocity gradient and direction. By carefully designing the direction, intensity, and vorticity characteristics of the jet, the vorticity it generates can be made to be opposite in direction to the vorticity of the naturally formed blade tip vortex. At the same time, the fluid injected by the jet has high momentum and total pressure, which can "fill" the low vorticity / low-pressure vortex core region that is about to form, increasing the average pressure level in this region, similar to "pressurizing" the low-pressure vortex core, thereby inhibiting the formation and intensity growth of the vortex core. Moreover, the jet can also disturb and prematurely destroy the initial roll-up structure of the blade tip vortex, making it difficult for it to develop into a concentrated strong vortex. The ultimate goal of this scheme is to change the relationship between vortex shedding, flow coherence and phase, reduce the amplitude of the blade spectral characteristics or broaden / disperse the spectral lines, thereby reducing the superposition of line spectral noise at the blade frequency and reducing sonar recognition.

[0027] exist Figure 1 In one embodiment shown, stator blades 5 are also included. A plurality of stator blades 5 are axially arranged around the duct 1 between the hub 2 and the inner wall of the duct 1, with both ends of the stator blades 5 connected between the outer peripheral wall of the hub 2 and the inner peripheral wall of the duct 1, respectively. The function of the stator blades 5 is typically to rectify and guide the inflow, reduce the non-uniformity of the flow field in front of the blades 3, improve the inflow angle, and reduce the suddenness of vortex shedding.

[0028] exist Figure 1 In one embodiment shown, along the direction of water flow in and out of the duct 1, a plurality of stator blades 5 are arranged in front of a plurality of blades 3, and a plurality of jet holes 11 are arranged between the stator blades 5 and the blades 3. Since the jet holes 11 are located in the space behind the stator blades 5 and in front of the blades 3, the jet holes 11 are close to the blade tip facing side; when jetting, the water flow inside the duct 1 first passes through the local flow field generated by the stator blades 5, and then enters the blade tip gap 101 along with the jet ejected from the jet holes 11. Thus, the guiding effect of the stator blades 5 is used to concentrate and reshape the jet, so that it maintains the necessary speed when entering the gap 101, thereby more effectively interfering with the blade tip vortex structure.

[0029] exist Figure 1In one embodiment shown, the number of blades 3 and stator blades 5 are both prime numbers to avoid generating more acoustic modes and increasing the radiated noise level. This is because if the number of blades 3 is a non-prime number, especially an even number, the arrangement of the blades 3 will form a mirror symmetry with respect to the vertical direction of the horizontal plane, thereby generating more acoustic modes and adversely affecting the acoustic performance of the ducted propeller. Similarly, the number of stator blades 5 is preferably a prime number.

[0030] exist Figure 1 In one embodiment shown, a delivery ring 6 and delivery pipes 7 are also included. The delivery ring 6 is disposed on the end face of the water inlet of the conduit 1 along the direction of water flow in and out of the conduit 1, and is connected to the jetting mechanism 4. Several delivery pipes 7 are embedded inside the wall of the conduit 1. One end of each delivery pipe 7 is connected to a jet orifice 11, and the other end extends axially along the conduit 1 towards the delivery ring 6, passing through the wall of the conduit 1 and connecting to the delivery ring 6. The jetting mechanism 4 delivers the jetting medium to the delivery ring 6, and then distributes it to the numerous jet orifices 11 via the delivery pipes 7 embedded in the wall of the conduit 1, ensuring uniformity of supply to the jet orifices 11 and facilitating maintenance. The embedding of the delivery pipes 7 within the pipe wall contributes to the structural integrity of the conduit 1 and a neat hydrodynamic shape, and reduces external leakage resistance or structural interference.

[0031] exist Figure 1 In one embodiment shown, a step 12 is axially arranged around the inner wall of the duct 1, and several jet holes 11 are formed around the side of the step 12. The advantages are: firstly, it partially shields the openings of the jet holes 11, reducing direct diffusion between the jet and the external flow, thus concentrating the jet; secondly, the step 12 itself alters the local geometry of the inner wall of the duct 1, affecting the local flow field in the jet region, making the coupling between the jet and the blade tip gap 101 more controllable.

[0032] like Figure 1 As shown, combined with Figures 2 to 6 This invention discloses a method for controlling the spectral characteristics of a duct propeller, employing the aforementioned spectrally adjustable duct propeller, and controlling the spectral characteristics of the duct propeller by changing the jet velocity. (See also...) Figure 6 It can be observed that: Figure 6 The lower middle figure shows the propeller simulation without jet flow. It can be seen that the vortex intensity in the gap of blade 3 is relatively large, and the vortex intensity near the wall of duct 1 is also relatively large. Figure 6The upper middle figure shows a propeller simulation under jet flow conditions. It can be seen that when a jet cavity 11 is arranged in front of the blade 3 to generate a jet, the initial gap vortex at the tip of the blade 3 guide edge is suppressed. Subsequently, under the sliding edge strip, the gap vortex basically disappears, but the gap sweep vortex still exists. The vortex intensity at the outlet of the duct 1 is also enhanced, indicating that the gap vortex subsequently develops again. Therefore, further flow control is required. However, subsequent control is not within the scope of this study and will not be elaborated in detail.

[0033] exist Figures 1 to 6 In one embodiment shown, the jets ejected from the plurality of jet holes 11 have the same jet velocity, which is described in either a sine wave or a cosine wave form. Selecting a periodic function for modulation can create controlled time-coherent interference, facilitate frequency domain analysis, easily predict its impact on the leaf spectrum, and potentially transfer or disperse noise energy by adjusting the frequency, amplitude, and phase, thereby reducing the amplitude of concentrated spectral lines at the leaf frequency. Periodic modulation also facilitates the evaluation of its effects using linear control or spectral analysis methods.

[0034] exist Figures 1 to 6 In one embodiment shown, such as Figure 3 and Figure 4 As shown in the comparison, increasing the amplitude of the jet velocity waveform increases the amplitude of the spectral characteristics of the duct propeller while decreasing its amplitude; conversely, decreasing the amplitude of the jet velocity waveform decreases the amplitude of the spectral characteristics of the duct propeller. Figure 3 and Figure 5 As shown in the comparison, increasing the amplitude of the jet velocity waveform increases the amplitude of the spectral characteristics of the duct propeller while decreasing the amplitude of the jet velocity waveform decreases the amplitude of the spectral characteristics of the duct propeller.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A ducted propeller with tunable spectral characteristics, characterized in that: It includes a duct (1), a hub (2), blades (3), and a jetting mechanism (4). The propeller hub (2) is located at the center of the guide tube (1); A plurality of blades (3) are axially arranged on a hub (2) around a guide tube (1). The blades (3) rotate axially relative to the guide tube (1) with the hub (2). A gap (101) is left between the blade tip of the blade (3) and the inner wall of the guide tube (1). The inner wall of the conduit (1) is provided with a plurality of jet holes (11) axially around the conduit (1), and the plurality of jet holes (11) simultaneously spray jets toward the gap (101); The jetting mechanism (4) is used to input the jetting medium into a plurality of jetting holes (11).

2. The ducted propeller with adjustable spectral characteristics according to claim 1, characterized in that: It also includes stator blades (5), a plurality of stator blades (5) are axially arranged around the guide tube (1) between the hub (2) and the inner wall of the guide tube (1), and the two ends of the stator blades (5) are respectively connected between the outer peripheral wall of the hub (2) and the inner peripheral wall of the guide tube (1).

3. A ducted propeller with adjustable spectral characteristics according to claim 2, characterized in that: Along the direction of water flow in and out of the conduit (1), a number of stator blades (5) are arranged in front of a number of blades (3), and a number of jet holes (11) are arranged between the stator blades (5) and the blades (3).

4. A ducted propeller with adjustable spectral characteristics according to claim 2, characterized in that: The number of blades (3) and stator blades (5) are both prime numbers.

5. A ducted propeller with adjustable spectral characteristics according to claim 1, characterized in that: It also includes a conveying ring (6) and a conveying pipe (7); Along the direction of water flow in and out of the conduit (1), the conveying ring (6) is disposed on the end face of the water inlet end of the conduit (1), and the conveying ring (6) is connected to the jet mechanism (4); Several of the aforementioned delivery pipes (7) are embedded inside the wall of the conduit (1). One end of the delivery pipe (7) is connected to the jet hole (11), and the other end of the delivery pipe (7) extends along the axial direction of the conduit (1) toward the delivery ring (6) and passes through the wall of the conduit (1) to connect with the delivery ring (6).

6. The ducted propeller with tunable spectral characteristics according to claim 1, characterized in that: The inner wall of the conduit (1) is provided with a step (12) axially around the conduit (1), and several jet holes (11) are opened around the side of the step (12).

7. A method for controlling the spectral characteristics of a ducted propeller, characterized in that: The duct propeller with adjustable spectral characteristics as described in any one of claims 1 to 6 is used, and the spectral characteristics of the duct propeller are adjusted by changing the jet velocity.

8. The method for controlling the spectral characteristics of a ducted propeller according to claim 7, characterized in that: The jet velocities of the jets ejected in several of the jet holes (11) are the same, and the jet velocities are described in the form of a sine wave or a cosine wave.

9. The method for controlling the spectral characteristics of a ducted propeller according to claim 8, characterized in that: Increasing the amplitude of the jet velocity waveform increases the amplitude of the spectral characteristics of the duct propeller while decreasing its amplitude. Conversely, decreasing the amplitude of the jet velocity waveform decreases the amplitude of the spectral characteristics of the duct propeller.

10. The method for controlling the spectral characteristics of a ducted propeller according to claim 8, characterized in that: When the vehicle is traveling at a speed of 3 to 5 knots, the inner diameter of the duct (1) is 100 to 300 mm, the rotational speed of the propeller (3) is 3 to 5 rps, and the width of the gap (101) is 3 to 5 mm, the jet velocity of the jet ejected from the jet hole (11) is 1 to 3 m / s.

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