Ultrasonic jet exciter for flow field control

Abstract

The utility model provides an ultrasonic jet flow exciter for flow field control, which comprises an ultrasonic excitation source, a cavity and a slit outlet, and is characterized in that the ultrasonic excitation source uses ultrasonic waves as an excitation source, and pulse jet flow and directional ultrasonic pressure waves are generated through the ultrasonic excitation source; the cavity adopts a streamline design structure, so that energy loss caused by sudden change of the structure is effectively reduced; one end of the cavity is connected with the ultrasonic excitation source, and the other end of the cavity is connected with the slit outlet, so that the ultrasonic excitation source, the cavity and the slit outlet jointly form a Helmholtz resonator for the ultrasonic pressure wave. Ultrasonic waves are used as an excitation source, the influence on the environment is reduced, the problem of noise pollution is effectively solved, active control over fluid can be achieved through generated pulse jet flow and directional ultrasonic pressure waves, the structure is compact and small, installation is convenient, use under different environments and working conditions is easy, and the application range is wide.

Description

Technical Field

[0001] This utility model relates to the field of fluid mechanics, and in particular to an ultrasonic jet exciter for flow field control. Background Technology

[0002] Fluids are ubiquitous in the material world, and in many cases, they can adversely affect human production and daily life. For example, aerodynamic drag is a significant source of resistance in ground transportation vehicles such as cars and trains; at a speed of 120 km / h, aerodynamic drag accounts for approximately 80% of the total drag of a car. On airplanes, flow field separation on the wing surface leads to a decrease in lift and an increase in drag, which can even cause the aircraft to stall and crash in severe cases. The transition of fluid from laminar to turbulent flow in pipes significantly increases the velocity gradient of the airflow within the boundary layer, resulting in stronger frictional drag and increased energy consumption when using pipelines to transport gas, water, and oil. Similar phenomena also exist in the fluids surrounding ships and submarines that use water as a medium.

[0003] To address the adverse effects of fluid flow, active fluid control methods have been extensively studied in recent years. Among these, pulsed jet technology has attracted significant attention and has been proven in academia to significantly reduce vehicle drag and achieve lift enhancement and drag reduction in airfoils. The key to flow field control using pulsed jets lies in the design of the exciter. An ideal exciter should generate beneficial disturbances in the flow field while also possessing high energy efficiency, minimal environmental impact, and good economic performance.

[0004] Existing pulsed jet actuators primarily use vibrating diaphragms, loudspeakers, mechanical pistons, or plasma as excitation sources, mounted on one side of a cavity, with a slit or orifice on the other side. During operation, the excitation source undergoes periodic motion, driving fluid to periodically exit or enter through the slit or orifice, thus generating a pulsed jet. The actuator has a relatively large cavity and a relatively small slit, meeting the conditions for Helmholtz resonance. Therefore, the actuator exhibits Helmholtz resonance during operation, significantly increasing the jet intensity near the resonant frequency and promoting jet generation. In addition, some researchers have used high-pressure gas sources and high-frequency valves to generate pulsed jets.

[0005] The existing pulsed jet exciter works by generating pressure waves through the periodic motion of an excitation source. These pressure waves convert static pressure into dynamic pressure as they pass through a slit, thus producing a pulsed jet. However, due to the unsteady nature of the pulsed jet, the conversion from pressure wave to pulsed jet is incomplete; a significant portion of the pressure wave continues to propagate downstream, generating substantial noise. The noise problem of existing pulsed jet exciters greatly limits their further application, and they also suffer from low energy efficiency, making them unsuitable for real-world applications. Utility Model Content

[0006] The purpose of this invention is to overcome the shortcomings of existing pulse jets and propose a pulse jet device that can prevent noise pollution and has an effective flow field control effect.

[0007] To achieve the above objectives, this utility model proposes an ultrasonic jet exciter for flow field control, comprising an ultrasonic excitation source, a cavity, and a slit outlet:

[0008] The ultrasonic excitation source uses ultrasound as the excitation source to generate pulse jets and directional ultrasonic pressure waves.

[0009] The cavity adopts a streamlined design structure, which effectively reduces energy loss caused by structural abrupt changes;

[0010] One end of the cavity is connected to the ultrasonic excitation source, and the other end is connected to the slit outlet, so that the ultrasonic excitation source, the cavity, and the slit outlet together constitute a Helmholtz resonator.

[0011] Furthermore, the cavity includes a cavity body and a cavity neck, the cavity body being connected to the slit outlet via the cavity neck; the cavity body adopts a streamlined structure, and the cavity body and the cavity neck are an integral structure.

[0012] Furthermore, the cavity and the slit outlet can be connected as a single unit or by a threaded connection, with a rubber gasket placed at the threaded connection to ensure a sealing effect.

[0013] Furthermore, the head end of the cavity neck is connected to the cavity body, and the tail end is connected to the slit outlet; the inner diameter of the head end of the cavity neck is larger than the inner diameter of the tail end.

[0014] The cavity neck adopts a gradual transition structure, so that the inner diameter of the head end of the cavity neck gradually decreases from the tail end to the head end.

[0015] Furthermore, the ultrasonic excitation source is a device that generates ultrasonic waves, such as a compression driver, piezoelectric sensor, or loudspeaker.

[0016] Furthermore, the ultrasonic excitation source is connected to the cavity via a thread.

[0017] Furthermore, a rubber gasket is provided at the threaded connection between the ultrasonic excitation source and the cavity to ensure a sealing effect.

[0018] Furthermore, the cavity is integrally connected to the slit or connected by threads.

[0019] The cavity can be a symmetrical structure or an asymmetrical structure to facilitate installation in different environments.

[0020] The ultrasonic jet exciter is applied to flow field control fields such as aerodynamic drag reduction of automobile turbulent wakes, lift and drag reduction of airfoils, flow field control in pipelines, and active boundary layer control.

[0021] The method for controlling the jet using the ultrasonic jet exciter is as follows: 1) An ultrasonic pressure wave is generated by the ultrasonic excitation source; 2) When the ultrasonic pressure wave passes through the cavity, it is amplified by Helmholtz resonance and eventually transforms into a pulse jet through the slit outlet; 3) The incompletely transformed portion continues to propagate downstream as ultrasonic waves, and is partially transformed into induced airflow while propagating downstream.

[0022] Compared with the prior art, the advantages of this utility model are:

[0023] 1. Compared with traditional pulse jet exciters that generate huge noise, this utility model uses an ultrasonic excitation source to generate ultrasonic waves, which will not have a negative impact on the human ear, thus solving the noise pollution problem and greatly increasing its practical application capabilities.

[0024] 2. This invention generates pulse jets and directional ultrasonic pressure waves by using an ultrasonic excitation source without causing noise pollution to the human ear, thereby achieving active control of fluids and providing a feasible solution for the application of flow field control methods under real conditions.

[0025] 3. This invention uses ultrasound as the excitation source. Ultrasound has a short wavelength and suffers significant loss in air, resulting in a shorter propagation distance, less diffraction, poor penetration, and easy attenuation, thus reducing its impact on the environment. Compared with other sound waves, ultrasound is anisotropic. After exiting the slit, it propagates downstream without spreading in other directions, further reducing its impact on the environment. At the same time, because ultrasound is relatively concentrated, the concentrated ultrasonic pressure wave will generate significant induced airflow, producing strong disturbance to the flow field and thus creating a unique flow field control effect.

[0026] 4. The ultrasonic jet exciter proposed in this utility model can generate high-concentration and high-intensity ultrasound. After the high-concentration and high-intensity ultrasound is ejected from the slit outlet, part of it will be transformed into a wave-shaped airflow downstream, thereby producing a certain flow field control effect.

[0027] 5. This utility model adopts a streamlined cavity structure and a gradually changing cavity neck structure, which effectively reduces energy loss caused by structural abrupt changes.

[0028] 6. The ultrasonic jet exciter of this utility model has a compact and small structure, is easy to install, and can be installed on the wall of the vehicle body, wing, pipeline, etc. It is easy to use in different environments and working conditions and has a wide range of applications. Attached Figure Description

[0029] Figure 1 This is a three-dimensional structural diagram of the symmetrical ultrasonic jet exciter of Embodiment 1 of this utility model;

[0030] Figure 2 This is a three-dimensional structural cross-sectional view of the symmetrical ultrasonic jet exciter of Embodiment 1 of this utility model;

[0031] Figure 3 This is a three-dimensional structural diagram of the asymmetric ultrasonic jet exciter of Embodiment 2 of this utility model;

[0032] Figure 4 This is a three-dimensional structural cross-sectional view of the asymmetric ultrasonic jet exciter of Embodiment 2 of this utility model;

[0033] Figure 5 This is a schematic diagram illustrating the working principle of the ultrasonic jet exciter in Embodiment 1 of this utility model. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be further described below.

[0035] Example 1

[0036] This embodiment 1 proposes an ultrasonic jet exciter for flow field control, such as... Figure 1 As shown, the device includes an ultrasonic excitation source 1, a cavity 2, and a slit outlet 3. The ultrasonic excitation source 1 is used to generate ultrasonic waves, which are used as the excitation source to generate pulse jets and directional ultrasonic pressure waves. The ultrasonic excitation source 1 is threaded to the left end of the cavity 2, and a rubber gasket is provided at the connection to ensure a sealing effect. The slit outlet 3 is threaded to the right end of the cavity 2, and a rubber gasket is also provided at its connection for sealing. At the same time, the ultrasonic excitation source 1, the cavity 2, and the slit outlet 3 together constitute a Helmholtz resonator, which can amplify the generated pulse jets and pressure waves of a specific frequency through structural adjustments.

[0037] In this embodiment 1, the ultrasonic excitation source 1 is a compression actuator that generates ultrasonic waves; the cavity 2 adopts a symmetrical structure, such as... Figure 2 As shown, it includes a cavity 21 and a cavity neck 22. The cavity 21 is connected to the slit outlet 3 through the cavity neck 22. The cavity 21 and the cavity neck 22 are an integrated structure. The cavity 21 adopts a streamlined structure, which effectively reduces the energy loss caused by structural abrupt changes. The head end of the cavity neck 22 is connected to the cavity 21, and the tail end is connected to the slit outlet 3. At the same time, the inner diameter of the head end of the cavity neck 22 is larger than the inner diameter of the tail end. The cavity neck 22 adopts a gradual transition structure, so that the inner diameter of the head end of the cavity neck 22 gradually decreases from the inner diameter of the tail end.

[0038] like Figure 5As shown, the specific method for jet control using the ultrasonic jet exciter of Embodiment 1 is as follows:

[0039] 1) Ultrasonic pressure wave 4 is generated by ultrasonic excitation source 1;

[0040] 2) When the ultrasonic pressure wave 4 passes through the cavity 2, it will be amplified by Helmholtz resonance and eventually be converted into a pulse jet 5 through the slit outlet 3;

[0041] 3) The incompletely converted portion continues to propagate downstream as ultrasound, and is partially converted into induced airflow 6 while propagating downstream.

[0042] Example 2

[0043] This embodiment 2 proposes an ultrasonic jet actuator for flow field control. The ultrasonic jet actuator in this embodiment 2 is the same as that in embodiment 1, except that, as follows: Figure 3 and Figure 4 As shown, in order to facilitate installation in different environments, the cavity 2 in the ultrasonic jet exciter of this embodiment 2 has an asymmetric structure.

[0044] Example 3

[0045] This embodiment 3 proposes an ultrasonic jet exciter for flow field control. The ultrasonic jet exciter in this embodiment 3 is the same as that in embodiment 1, except that the slit outlet 3 and the cavity 2 are integrally connected in this embodiment 3.

[0046] The above are merely preferred embodiments of this utility model and do not constitute any limitation on this utility model. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and contents disclosed in this utility model without departing from the scope of the technical solutions of this utility model shall still fall within the protection scope of this utility model.

Claims

1. An ultrasonic jet actuator for flow field control, characterized in that: Includes ultrasonic excitation source, cavity and slit outlet: The ultrasonic excitation source uses ultrasonic waves as an excitation source, and generates pulse jets and directional ultrasonic pressure waves through the ultrasonic excitation source; The cavity adopts a streamlined design structure; One end of the cavity is connected to the ultrasonic excitation source, and the other end is connected to the slit outlet, so that the ultrasonic excitation source, the cavity and the slit outlet together constitute a Helmholtz resonator.

2. The ultrasonic jet actuator for flow field control according to claim 1, characterized in that: The cavity comprises a cavity body and a cavity neck, and the cavity body is connected to the slit outlet through the cavity neck; the cavity body adopts a streamlined structure, and the cavity body and the cavity neck are an integrated structure.

3. The ultrasonic jet actuator for flow field control according to claim 2, characterized in that: The head end of the cavity neck is connected to the cavity body, and the tail end is connected to the slit outlet; the inner diameter of the head end of the cavity neck is larger than the inner diameter of the tail end; the cavity neck adopts a gradual transition structure, so that the inner diameter of the cavity neck gradually decreases from the head end to the tail end.

4. The ultrasonic jet actuator for flow field control according to claim 1, characterized in that: The ultrasonic excitation source is a device for generating ultrasonic waves.

5. The ultrasonic jet actuator for flow field control according to claim 1, characterized in that: The ultrasonic excitation source is a compression driver, a piezoelectric sensor or a speaker that generates ultrasonic waves.

6. The ultrasonic jet actuator for flow field control according to claim 4, characterized in that: The ultrasonic excitation source is connected to the cavity via threads; a rubber gasket is provided at the threaded connection between the ultrasonic excitation source and the cavity.

7. The ultrasonic jet actuator for flow field control according to claim 1, characterized in that: The cavity is connected to the slit in an integrated manner or by means of a thread.

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