An asymmetric single-port self-excited pulsed jet device

Abstract

The present invention discloses an asymmetric single-port self-excited pulsed jet device, which includes a drainage port, a mixing chamber, and a snail-shaped jet port located on the central axis of the device in sequence to form a main flow path; a left feedback loop and a right feedback loop are respectively arranged on the left and right sides of the central axis of the device, and the overall configuration of the device is left-right asymmetric; wherein: when a high pressure is given at the drainage port of the device, a low pressure is given at the snail-shaped jet port, and the device can spontaneously generate a pulsed jet with a certain frequency and duty cycle at the outlet of the snail-shaped jet port for fluid flow control. By designing the snail-shaped jet port, the present invention can generate a pulsed jet with a certain frequency and duty cycle, thereby avoiding the adverse control effects generated by the currently widely used single-port self-excited sweeping jet device and double-port self-excited pulsed jet device in actual flow control applications, and is more practical in engineering.

Description

Technical Field

[0001] The present invention relates to an asymmetric single-port self-excited pulsed jet device, belonging to the technical field of unsteady flow control. Background Art

[0002] Currently, fluid machinery is developing towards the direction of high aerodynamic load. When the load of fluid machinery increases significantly beyond the current aerodynamic design level, flow separation phenomena usually occur due to high adverse pressure gradients or shock-boundary layer interference, causing the efficiency of fluid machinery to drop sharply or even leading to instability. Therefore, researchers at home and abroad have been focusing on flow control technologies and corresponding flow control devices that can suppress or even eliminate flow separation. Unsteady flow control technology is an advanced flow control technology, and the unsteady excitation it generates can utilize flow instability and interact coherently with the coherent structures in the separated flow. Relevant research shows that to achieve the same flow control effect, using unsteady flow control technology can save 1 to 2 orders of magnitude of the energy consumed compared to the corresponding steady flow control technology, that is, it has the effect of "using a small amount of effort to achieve great results".

[0003] The self-excited jet oscillator can be used as an unsteady flow control device. If the inlet and outlet of the self-excited jet oscillator are respectively connected to high-pressure and low-pressure gas sources, the self-excited jet oscillator can rely on flow instability to generate unsteady jets at the outlet, which can be used as the unsteady excitation required for unsteady flow control. Since the self-excited jet oscillator has a simple structure and no moving parts, it has good application prospects.

[0004] However, there are certain problems with the currently mainstream self-excited jet oscillators as unsteady flow control devices. The first type is the symmetric single-port self-excited sweeping jet ejector as shown in Figure 1 , which generates a sweeping jet at the outlet (that is, the jet velocity is basically unchanged, but the jet angle changes within a certain range, such as between 40° and 140°). However, there is usually an optimal jet angle for the control of separated flow (usually between 10° and 45°). Therefore, the control effect of the sweeping jet is usually not good or even has a negative control effect. The second type is the symmetric double-port self-excited pulsed jet ejector as shown in Figure 2 , which generates two pulsed jets with opposite phases (a phase difference of 180°) at the two outlets (the jet angle remains unchanged and the velocity changes). However, relevant research shows (see Li Qiufeng's "Mechanism Research on a Passive Double-Pulse Jet") that double-pulse jets with close positions and opposite phases can generate a coherent effect, and their control effects cancel each other out. Therefore, the flow control effect of this type of jet ejector is also poor. Summary of the Invention

[0005] The object of the present invention is to overcome the deficiencies in the prior art and provide an asymmetric single-port self-excited pulsed jet device, which can be used to suppress flow separation in fluid machinery and improve the performance of fluid machinery.

[0006] To achieve the above object, the present invention is implemented by the following technical solutions:

[0007] In a first aspect, the present invention provides an asymmetric single-port self-excited pulsed jet device, which includes a drainage port, a mixing chamber, and a snail-shaped jet port located on the central axis of the device in sequence to form a main flow path; a left feedback loop and a right feedback loop are respectively provided on the left and right sides of the central axis of the device, and the overall configuration of the device is left-right asymmetric; wherein:

[0008] When a high pressure is given at the drainage port of the device, a low pressure is given at the snail-shaped jet port, and the device can spontaneously generate a pulsed jet with a certain frequency and duty cycle at the outlet of the snail-shaped jet port for fluid flow control.

[0009] Further, the shape of the snail-shaped jet port is composed of an ellipse and a parallelogram spliced together, and its outer shape resembles a snail shape.

[0010] Further, in the snail-shaped jet port, the elliptical structure is used to reverse the jet that was originally swept to the left, suppress and block the jet itself, forming the trough of the pulsed jet; the parallelogram structure is used to smoothly guide the jet swept to the right, forming the peak of the pulsed jet.

[0011] Further, the lengths of the left feedback loop and the right feedback loop are not equal.

[0012] Further, the length of the right feedback loop is greater than the length of the left feedback loop.

[0013] Further, the value of the ratio of the length L1 of the right feedback loop to the length L2 of the left feedback loop ranges from 1.05 to 2.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention:

[0015] The present invention provides an asymmetric single-port self-excited pulsed jet device. By designing the snail-shaped jet port, a pulsed jet with a certain frequency and duty cycle can be generated, thereby avoiding the adverse control effects generated by the currently widely used single-port self-excited swept jet device and double-port self-excited pulsed jet device in actual flow control applications, and is more practical in engineering. Description of the Drawings

[0016] Figure 1 It is a schematic diagram of a symmetric single-port self-excited swept jet device;

[0017] Figure 2It is a schematic diagram of a symmetric double-port self-excited pulsed jet device;

[0018] Figure 3 It is a schematic diagram of an asymmetric single-port self-excited pulsed jet device;

[0019] Figure 4 It is a schematic diagram of the clogging mode of an asymmetric single-port self-excited pulsed jet device;

[0020] Figure 5 It is a schematic diagram of the jet mode of an asymmetric single-port self-excited pulsed jet device.

[0021] In the figure: 1, drainage port; 2, mixing chamber; 3, snail-shaped jet port; 4, left feedback loop; 5, right feedback loop. Detailed implementation mode

[0022] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the protection scope of the present invention.

[0023] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0024] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0025] Embodiment 1

[0026] As Figure 3As shown in the figure, this embodiment introduces an asymmetric single-port self-excited pulsed jet device, which includes a drainage port 1, a mixing chamber 2, and a snail-shaped jet port 3, constituting the main flow path; the left and right sides of the device are respectively provided with left and right feedback loops 4 and 5 with different lengths, and the overall structure of the device is left-right asymmetric. When a high pressure is given to the drainage port 1 of the device and a low pressure is given to the snail-shaped jet port 3, the device can spontaneously generate a pulsed jet with a certain frequency and duty cycle at the outlet of the snail-shaped jet port 3, which can be used for fluid flow control. The self-excited jet device is internally provided with left and right feedback loops 5, and the feature is that the lengths of the left feedback loop 4 and the right feedback loop 5 are not equal. Usually, the length of the right feedback loop 5 should be greater than the length of the left feedback loop 4. This is because the flow resistance is large when the jet flows through the elliptical structure of the snail-shaped jet port 3, resulting in a shorter residence time in this mode, which affects the duty cycle of the pulsed jet. The longer right feedback loop 5 can make up for this, so that the duty cycle of the pulsed jet is close to the ideal value of 0.5; among them, the value of the ratio of the length of the right feedback loop 5 to the length of the left feedback loop 4 is between 1.05 and 2.

[0027] Technical principle of the present invention: In the main flow path MC in the mixing chamber 2, due to the Coanda effect, it will adhere to one of the left or right wall surfaces of the mixing chamber 2. If the main flow path MC adheres to the right wall surface of the mixing chamber 2, the jet will wrap around the left wall surface of the snail-shaped jet port 3 and return upstream, forming an effect of suppressing and blocking the jet itself, and at the same time forming a right-side feedback loop (see Figure 4 ), and the right feedback flow path RC then pushes the main flow path MC at the inlet of the mixing chamber 2 to adhere to the left wall surface of the mixing chamber 2, so that the main flow finally forms a jet and flows out from the snail-shaped jet port 3, and a feedback flow path LC is formed in the left feedback loop (see Figure 5 ). These two processes alternate, thus forming a pulsed jet with a certain duty cycle.

[0028] Next, a preferred embodiment is used to illustrate the content involved in the above embodiment.

[0029] In the specific implementation of an asymmetric single-port self-excited pulsed jet device, first, the required pulsed jet frequency F0 and jet velocity V0 need to be determined according to the specific application scenario of the fluid machinery. Secondly, on the basis of the existing mature symmetric single-port self-excited sweeping jet device, through scaling, the jet sweeping frequency at the jet velocity V0 is made F0; through numerical simulation or experimental means, the snail-shaped jet port 3 is designed, and the lengths of the major and minor axes of the elliptical configuration in the snail-shaped jet port 3 are optimized, and the ratio of the length L1 of the right feedback loop 5 to the length L2 of the left feedback loop 4 is optimized, so that the asymmetric single-port self-excited pulsed jet device generates a single pulsed jet with a frequency of F0, a jet velocity of about V0, and a duty cycle of about 0.5, thereby realizing the pulsed jet flow control effect on the flow field.

[0030] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. An asymmetric single-port self-excited pulsed jet device, characterized in that It includes a drainage port (1), a mixing chamber (2), and a snail-shaped jet port (3) located successively on the central axis of the device, forming a main flow path; on the left and right sides of the central axis of the device, a left feedback loop (4) and a right feedback loop (5) are respectively provided, and the overall configuration of the device is left-right asymmetric; where: When a high pressure is given to the drainage port (1) of the device, and a low pressure is given to the snail-shaped jet port (3), the device can spontaneously generate a pulsed jet with a certain frequency and duty cycle at the outlet of the snail-shaped jet port (3) for fluid flow control; The shape of the snail-shaped jet port (3) is formed by splicing an ellipse and a parallelogram, and its outer shape resembles a snail; In the snail-shaped jet port (3), the elliptical structure is used to reverse the jet that was originally swept to the left, suppress and block the jet itself, forming the trough of the pulsed jet; the parallelogram structure is used to smoothly guide the jet swept to the right, forming the peak of the pulsed jet.

2. The asymmetric single-port self-excited pulsed jet device according to claim 1, characterized in that The lengths of the left feedback loop (4) and the right feedback loop (5) are not equal.

3. The asymmetric single-port self-excited pulsed jet device according to claim 1, wherein The length of the right feedback loop (5) is greater than the length of the left feedback loop (4).

4. The asymmetric single-port self-excited pulsed jet device according to claim 1, characterized in that The value of the ratio of the length L1 of the right feedback loop (5) to the length L2 of the left feedback loop (4) ranges from 1.05 to 2.

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