An asymmetric feedback channel fluidic oscillator that compensates for inlet distortion and a design method

Abstract

The application discloses an asymmetric feedback channel fluid oscillator compensating for inlet distortion and a design method, and belongs to the technical field of fluid control. The oscillator comprises an inlet nozzle, an oscillation chamber, double-side wall-attached curved surfaces, asymmetric double feedback channels and an outlet section. The flow area of the double-side feedback channels adopts an asymmetric design: the flow distortion caused by the upstream pipeline disturbance makes the jet naturally deviate to the strong wall-attached side, and the cross-sectional area of the feedback channel corresponding to the strong wall-attached side is greater than that of the feedback channel corresponding to the weak wall-attached side, so as to accurately offset the inlet distortion and restore stable and symmetric oscillation. The application does not need to reserve a long straight pipe section or install a rectifier, does not additionally occupy installation space, can significantly reduce the critical oscillation Reynolds number under the distorted flow, solves the industry problems of jet unilateral locking and asymmetric oscillation, has a simple structure, low flow resistance, can be adapted to installation scenes with limited space, and is high in reliability and universality.

Description

Technical Field

[0001] This invention relates to the field of fluid control technology, and in particular to a feedback fluid oscillator, specifically an asymmetric feedback channel compensation fluid oscillator and its design method for addressing flow distortion caused by upstream pipeline disturbances. Background Technology

[0002] A fluid oscillator is a fluid control device that transforms a steady-state input fluid into a periodic oscillating jet by relying solely on the interaction between the fluid's own dynamic characteristics and geometric structure, without any moving mechanical parts. It has advantages such as high reliability, long life, low energy consumption, and excellent flow field control effect, and is widely used in engineering fields such as aerospace flow control, automotive atomizing nozzles, enhanced cooling of electronic devices, chemical media mixing, and flow measurement.

[0003] Feedback-type (Coanda effect type) fluid oscillators are currently the most widely used mainstream configuration in engineering applications. The core premise for their stable oscillation is that the inlet flow is uniformly and symmetrically distributed. Through the symmetrical wall effect on both sides and the positive feedback mechanism of the symmetrical feedback channel, the periodic alternation of the jet is realized, and finally a stable symmetrical oscillating jet is output.

[0004] However, in practical engineering applications, due to installation space limitations, it is often impossible to reserve a sufficiently long straight pipe section before the oscillator inlet. Elbow pipes or other pipeline disturbance elements (such as valves, reducers, tees, etc.) must be arranged. Such upstream pipeline disturbances will cause severe velocity distribution distortion in the downstream fluid. For example, elbow pipes will generate Dean vortex secondary flow structures, causing the incoming flow at the oscillator inlet to present a fixed asymmetric distribution.

[0005] This asymmetric flow introduces a continuous fixed bias torque into the oscillator, causing the jet to naturally deflect towards the side with higher velocity, leading to a series of serious problems: First, the critical oscillation Reynolds number increases significantly, making it impossible to start oscillation under low velocity and low Reynolds number conditions; second, the attachment time of the jets on both sides is severely unbalanced, resulting in an asymmetric oscillating jet that cannot meet design requirements; third, in extreme cases, the jet may lock up on one side, making it impossible to establish oscillation, and the oscillator will fail directly.

[0006] To address the aforementioned issues, existing technologies primarily offer two solutions: one is to reserve a sufficiently long straight pipe section between the pipeline disturbance and the oscillator inlet to restore symmetrical velocity distribution; the other is to install a rectifier before the inlet to homogenize the velocity distribution. However, both solutions require additional axial installation space, making them completely unsuitable for miniaturized, integrated, and space-constrained applications.

[0007] Furthermore, while some asymmetric fluid oscillators have been disclosed in existing technologies, their core purpose is to actively generate asymmetric pulsed jets through asymmetric structures to meet the needs of specific scenarios such as rock breaking, sediment treatment, and enhanced mixing, rather than to compensate for asymmetric distortion of the inlet flow. Some asymmetric oscillators are also used for low Reynolds number oscillation optimization in microfluidic scenarios, without considering the exogenous inlet flow distortion caused by upstream pipeline disturbances, nor have they proposed corresponding compensation schemes for this problem. Meanwhile, existing feedback oscillators generally suffer from drawbacks such as redundant cavity structures, high local flow resistance, high energy loss, and high manufacturing difficulty.

[0008] In summary, there is currently no existing technology that can accurately compensate for flow distortion caused by upstream pipeline disturbances without requiring additional installation space, has a simplified structure and low flow resistance, and restore the stable and symmetrical oscillation of the oscillator. Summary of the Invention

[0009] This invention aims to address the following deficiencies in the prior art: 1. Existing symmetrical feedback fluid oscillators have problems such as a significant increase in the critical start-up Reynolds number, inability to start oscillation under low flow conditions, and even single-sided jet lock-up failure caused by upstream pipeline disturbances (such as bends) before the inlet. 2. Existing symmetrical oscillators exhibit severe oscillation symmetry imbalance under distorted incoming flow, failing to meet design requirements; 3. Existing entrance distortion compensation solutions require additional installation space and cannot be adapted to miniaturized, integrated, or space-constrained scenarios; 4. Existing asymmetric fluid oscillators all actively generate asymmetric outputs and cannot be used for inlet flow distortion compensation; 5. Existing feedback oscillators suffer from structural redundancy, high local flow resistance, high energy loss, and high manufacturing difficulty.

[0010] To address the aforementioned technical problems, this invention provides, in one aspect, an inlet distortion-compensated fluid oscillator with an asymmetric feedback channel, the specific technical solution of which is as follows: An asymmetric feedback channel fluid oscillator for compensating for inlet distortion includes an inlet nozzle, an oscillation chamber, a first attached wall surface, a second attached wall surface, a first feedback channel, a second feedback channel, and an outlet section. The inlet nozzle is located at the upstream inlet end of the oscillation chamber. The first and second attached wall surfaces are respectively located on the left and right inner walls of the oscillation chamber. The outlet section is located at the downstream end of the oscillation chamber. The two ends of the first feedback channel are respectively connected to a first natural diversion zone downstream of the oscillation chamber and the upstream root of the inlet nozzle. The two ends of the second feedback channel are respectively connected to a second natural diversion zone downstream of the oscillation chamber and the upstream root of the inlet nozzle.

[0011] When the jet adheres to the wall of the oscillating chamber on either side of the wall surface, the downstream flow field naturally forms two functional regions: a region where the main flow flows directly to the outlet, and a region where backflow occurs and enters the feedback channel. This invention refers to the backflow region downstream of the oscillating chamber near the first wall surface as the first natural diversion region, and the backflow region near the second wall surface as the second natural diversion region; both are formed entirely naturally by the jet adhesion effect.

[0012] The first and second feedback channels are asymmetrical structures, which match the distortion of the incoming flow velocity distribution caused by upstream pipeline disturbance before the fluid oscillator inlet. Due to the distortion of the incoming flow velocity distribution, the jet naturally deflects to one side as the strong attachment side and the opposite side as the weak attachment side. The flow cross-sectional area of ​​the feedback channel corresponding to the strong attachment side is larger than the flow cross-sectional area of ​​the feedback channel corresponding to the weak attachment side.

[0013] It should be noted that the upstream pipeline disturbances include, but are not limited to, elbows, valves, reducers, tees, etc., which all share the characteristic of causing the velocity distribution at the oscillator inlet section to be asymmetrical. In a typical scenario, elbows cause the inflow velocity to be higher on the incoming side, and the jet naturally deflects to that side, which is the strong adhesion side; while the side with lower velocity, where the jet is difficult to adhere stably, is the weak adhesion side.

[0014] Furthermore, the length of the feedback channel corresponding to the strong attachment side is less than the length of the feedback channel corresponding to the weak attachment side.

[0015] Preferably, the flow cross-sectional area of ​​the feedback channel corresponding to the strong attachment side is 10% to 50% larger than that of the feedback channel corresponding to the weak attachment side; at the same time, the length of the feedback channel corresponding to the strong attachment side is 5% to 30% shorter than that of the feedback channel corresponding to the weak attachment side. By coordinating the adjustment of the cross-sectional area and length, the feedback flow resistance and feedback pressure peak can be controlled more precisely, thus optimizing the compensation effect.

[0016] Furthermore, the radius of curvature of the attachment surface corresponding to the strong attachment side is greater than the radius of curvature of the attachment surface corresponding to the weak attachment side, in order to weaken the Coanda attachment effect on the strong attachment side and reduce the difficulty of jet switching.

[0017] Furthermore, the outlet axis of the inlet nozzle is deflected toward the weakly attached side by an angle of 1° to 5° to counteract the inherent bias torque of the inlet flow from the source.

[0018] Another aspect of the present invention provides an asymmetric compensation design method for fluid oscillators to address inlet distortion, the specific technical solution of which is as follows: An asymmetric design method for a fluid oscillator to compensate for inlet distortion includes the following steps: S1. Incoming flow distortion: For the upstream pipeline disturbance structure preset before the fluid oscillator inlet, the velocity distribution data of the fluid oscillator inlet section is obtained through numerical simulation or flow field test, and the direction and non-uniformity of the incoming flow distortion, as well as the strong wall-attached side (11) and the relatively weak wall-attached side (12) of the jet's natural bias are determined. S2. Simulation verification of the benchmark symmetric model: Establish a benchmark fluid oscillator model with a symmetric structure. Use the distorted incoming flow obtained in step S1 as the inlet boundary condition and perform unsteady numerical simulation to obtain the start-up characteristics, oscillation symmetry, and critical start-up Reynolds number of the benchmark fluid oscillator model under the distorted incoming flow, and determine the failure boundary of the benchmark model. S3. Iterative design of asymmetric feedback channel parameters: Taking the strong attachment wall side (11) as the core adjustment object, the flow cross-sectional area of ​​the feedback channel corresponding to the strong attachment wall side (11) is increased first, and the length of the feedback channel corresponding to the strong attachment wall side (11) can be shortened to establish an asymmetric structure oscillator model; with the minimum critical start-up Reynolds number as the optimization objective under the premise that the proportion of jet attachment time on both sides reaches the preset symmetry threshold, the optimal combination of asymmetric feedback channel parameters is determined through multiple rounds of numerical simulation iteration; S4. Full-condition stability verification: Within the preset operating Reynolds number range, perform full-condition unsteady numerical simulation on the asymmetric structure oscillator model obtained in step S3 to verify the start-up characteristics, oscillation symmetry, and frequency-flow linearity, ensuring that there are no jet lock-up or oscillation instability problems within the full-condition range. S5. Prototype Calibration and Optimization: Based on the optimal parameters verified in step S4, process the prototype according to the principle. Through experimental testing, perform final calibration and optimization of the asymmetric parameters to obtain the final compensated fluid oscillator.

[0019] Furthermore, in step S1, the upstream pipeline disturbance includes a bend in the pipe, and the length of the straight pipe section between the bend and the inlet of the fluid oscillator is less than 5 times the pipe diameter. Under this short straight pipe section condition, the velocity distribution distortion is not fully recovered, and the advantages of the present invention are particularly obvious.

[0020] Furthermore, in step S3, the flow cross-sectional area of ​​the feedback channel corresponding to the strong attachment side is 10% to 50% larger than the flow cross-sectional area of ​​the feedback channel corresponding to the weak attachment side; the length of the feedback channel corresponding to the strong attachment side is 5% to 30% shorter than the length of the feedback channel corresponding to the weak attachment side.

[0021] Furthermore, step S3 also includes asymmetric optimization iteration of the curvature of the attached wall surface, the position of the diversion wedge, and the deflection angle of the inlet nozzle, in order to achieve the best compensation effect under multi-parameter coupling.

[0022] This invention breaks the conventional understanding in the field that "oscillators must maintain a symmetrical structure to achieve symmetrical oscillation." For fixed asymmetrical inflow caused by upstream pipeline disturbance, this invention introduces a controllable asymmetrical feedback channel design to balance and counteract the inherent bias torque of the inflow by introducing a feedback force that is opposite to the inlet bias.

[0023] Specifically, due to pipeline disturbances, the Coanda adhesion effect of the jet is amplified on the strongly attached side, requiring a greater feedback thrust to drive the jet to switch away. This invention increases the flow cross-sectional area of ​​the feedback channel on the strongly attached side, reduces the flow resistance of the feedback channel on that side, and increases the flow rate and pressure peak of the feedback flow, thereby strengthening the feedback thrust on that side and overcoming the amplified adhesion effect. At the same time, by shortening the length of the feedback channel on the strongly attached side, the flow resistance can be further reduced and the phase of the feedback signal can be optimized, ultimately bringing the jet switching difficulty and adhesion time on both sides back to a balanced state, achieving stable symmetrical oscillation under asymmetrical flow.

[0024] When the jet adheres to the wall on either side of the curved surface, some of the fluid will naturally enter the natural diversion zone on that side, and flow back to the root of the inlet nozzle through the feedback channel, pushing the jet to switch to the other side.

[0025] In summary, the present invention has the following beneficial effects: 1. Perfectly adaptable to space-constrained scenarios, requiring no additional installation space: This invention achieves distortion compensation by modifying the geometric parameters of the oscillator's own feedback channel, without requiring long straight pipe sections or rectifiers, and without adding any additional installation space, making it perfectly adaptable to miniaturized, integrated, and extremely space-constrained engineering scenarios.

[0026] 2. Effectively solves the problem of oscillation failure and greatly expands the stable operating range: This invention can significantly reduce the critical oscillation Reynolds number under distorted inflow, solve the problem of oscillation failure under low flow rate conditions and jet lock-up on one side under extreme bias, and expand the stable operating Reynolds number range of the oscillator to 2 to 3 times that of symmetrical design.

[0027] 3. Precisely restore oscillation symmetry to meet design requirements: Through asymmetric parameter design that precisely matches the inlet distortion, the attachment time ratio of the two jets can be made as close as possible to 50%:50% under design conditions, and the amplitude and frequency symmetry of the oscillating jet can be restored to the level of symmetrical design under uniform inflow.

[0028] 4. Simplified structure, lower flow resistance, and significantly improved energy efficiency: This invention adopts a minimalist cavity design without additional flow diversion structure, which is simpler in structure and easier to process. At the same time, it eliminates the local resistance loss caused by additional structure, and the pressure drop at the inlet and outlet is significantly reduced compared with the traditional structure, resulting in a significant improvement in energy conversion efficiency.

[0029] 5. Reduced processing costs and strong versatility: The asymmetric structure of this invention is completely consistent with the processing technology of traditional symmetric oscillators and can be realized through conventional machining, 3D printing and other methods without additional processing costs; at the same time, it can be adapted to the compensation needs of different diameters, different working conditions and different upstream pipeline disturbance structures, and has strong versatility.

[0030] 6. The design method is reproducible and standardizable: The design method provided by this invention can complete parameter iterative optimization through numerical simulation, without the need for a large number of trial and error experiments, and can form a standardized design process that is suitable for industrial mass applications. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a planar structure of a commonly used symmetrical feedback fluid oscillator in the prior art. Figure 2 This is a schematic diagram of a plan view of a commonly used symmetrical feedback fluid oscillator with a 90° elbow pipe at the inlet. Figure 2 The entrance cross section is marked with "AA" for identification; Figure 3 For the corresponding Figure 2 The inlet velocity distribution distortion contour map of the AA cross section, the distortion depends only on the bend form before the inlet; Figure 4 This is a schematic diagram of the planar structure of the inlet distortion compensation fluid oscillator with an asymmetric feedback channel as described in Embodiment 1 of the present invention; Figure 5 This is a flowchart of the asymmetric compensation design method for fluid oscillators to address inlet elbow distortion, as described in this invention. Figure 6 The streamline distribution of the fluid field inside the fluid oscillator of Comparative Example 1 (symmetric structure) at a certain moment under the distortion of the inlet elbow; Figure 7 This is a flow field streamline distribution diagram inside the fluid oscillator at a certain moment under the inlet elbow distortion condition of Example 1 (asymmetric structure); Figure 8 This is a flow field streamline distribution diagram inside the fluid oscillator at another moment under the inlet elbow distortion condition of Example 1 (asymmetric structure).

[0032] Explanation of reference numerals in the attached drawings: 1-Inlet nozzle, 2-Oscillating chamber, 3-First wall-attached curved surface, 4-Second wall-attached curved surface, 5-First feedback channel, 6-Second feedback channel, 7-Outlet section, 8-First natural diversion zone, 9-Second natural diversion zone, 10-Elbow pipe, 11-Strong wall-attached side, 12-Weak wall-attached side. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] Feedback-type (Coanda effect type) fluid oscillators are currently the most widely used mainstream configuration in engineering applications. Their stable oscillation relies on a uniform and symmetrical inlet flow distribution. Through the symmetrical wall-attachment effect on both sides and the positive feedback mechanism of the symmetrical feedback channel, the jet periodically alternates, ultimately outputting a stable symmetrical oscillating jet. It has one inlet, one outlet, two feedback channels, and one oscillation chamber. The basic working principle is as follows: Under stable inlet pressure, the main jet enters the coupling chamber from the inlet nozzle. Due to the Coanda effect, the main jet randomly adheres to one side wall. Due to the flow restriction effect of the outlet nozzle, some fluid enters the feedback channel and flows back to the inlet nozzle throat, subsequently filling the separation bubble in the oscillation chamber. The enlargement of the separation bubble pushes the main jet towards the other side wall and the feedback channel, repeating the cycle. This results in a periodic oscillating jet at the nozzle with a relatively constant jet velocity and a sweeping, oscillating jet direction within a certain angle range.

[0035] like Figure 1 The diagram shown is a planar structural schematic of a commonly used symmetrical feedback fluid oscillator in the prior art, including an inlet nozzle 1, an oscillation chamber 2, a first attached wall surface 3, a second attached wall surface 4, a first feedback channel 5, a second feedback channel 6, and an outlet section 7. Figure 1 The arrows in the diagram indicate the main flow direction of the fluid inside the oscillator at a certain moment.

[0036] like Figure 2 The image shows a schematic diagram of a plan view of a commonly used symmetrical feedback fluid oscillator with a 90° bend in the pipe before the inlet. Figure 1 The prior art commonly uses a symmetrical feedback fluid oscillator with a 90° bend in the pipe 10 before the inlet. The cross-section AA is marked to monitor the inlet velocity distribution distortion caused by the bend in the pipe 10. The presence of the 90° bend in the pipe 10 leads to abnormal flow within the oscillator.

[0037] like Figure 3 The diagram shows the velocity distribution across the inlet AA cross section. Because a 90° bend pipe is installed before the inlet of the commonly used symmetrical feedback fluid oscillator in the prior art, the velocity distribution across the inlet AA cross section is distorted.

[0038] It should be noted that the velocity distortion at the inlet AA cross section is mainly determined by the bend shape before the inlet. Therefore, as long as the symmetrical and asymmetrical fluid oscillators adopt the same bend design before the inlet, the velocity distribution cloud map of the two at the AA cross section will be basically the same.

[0039] like Figure 4The diagram shown is a planar structural schematic of the inlet distortion compensation fluid oscillator with asymmetric feedback channel according to Embodiment 1 of the present invention, including an inlet nozzle 1, an oscillation chamber 2, a first attached wall surface 3, a second attached wall surface 4, a first feedback channel 5, a second feedback channel 6, an outlet section 7, a first natural diversion zone 8, a second natural diversion zone 9, an elbow pipe 10, a strong attached wall side 11, and a weak attached wall side 12.

[0040] like Figure 5 As shown, an asymmetric design method for a fluid oscillator to compensate for inlet distortion is described, and the specific implementation steps are as follows: S1. Incoming flow distortion: For the upstream pipeline disturbance structure preset before the fluid oscillator inlet, obtain the velocity distribution data of the fluid oscillator inlet section through numerical simulation or flow field test, determine the direction and non-uniformity of the incoming flow distortion, as well as the strong wall-attached side 11 and the relatively weak wall-attached side 12 of the jet's natural bias. S2. Simulation verification of the benchmark symmetric model: Establish a benchmark fluid oscillator model with a symmetric structure. Use the distorted incoming flow obtained in step S1 as the inlet boundary condition and perform unsteady numerical simulation to obtain the start-up characteristics, oscillation symmetry, and critical start-up Reynolds number of the benchmark fluid oscillator model under the distorted incoming flow, and determine the failure boundary of the benchmark model. S3. Iterative design of asymmetric feedback channel parameters: Taking the strong attachment side 11 as the core adjustment object, the flow cross-sectional area of ​​the feedback channel corresponding to the strong attachment side (11) is increased first, and the length of the feedback channel corresponding to the strong attachment side 11 can be shortened to establish an asymmetric structure oscillator model; with the minimum critical start-up Reynolds number as the optimization objective under the premise that the proportion of jet attachment time on both sides reaches the preset symmetry threshold, the optimal combination of asymmetric feedback channel parameters is determined through multiple rounds of numerical simulation iteration. S4. Full-condition stability verification: Within the preset operating Reynolds number range, perform full-condition unsteady numerical simulation on the asymmetric structure oscillator model obtained in step S3 to verify the start-up characteristics, oscillation symmetry, and frequency-flow linearity, ensuring that there are no jet lock-up or oscillation instability problems within the full-condition range. S5. Prototype Calibration and Optimization: Based on the optimal parameters verified in step S4, process the prototype according to the principle. Through experimental testing, perform final calibration and optimization of the asymmetric parameters to obtain the final compensated fluid oscillator.

[0041] If a flow field testing method is selected in step S1, the flow field testing can be carried out using conventional flow velocity measurement methods such as particle image velocimetry (PIV), laser Doppler velocimetry (LDV), hot wire anemometer, or five-hole probe. By arranging a transparent window or probe hole upstream of the oscillator inlet section, the time-averaged flow velocity distribution at each measuring point of the section can be obtained, thereby determining the direction of incoming flow distortion and non-uniformity.

[0042] The unsteady numerical simulations in the above steps can be implemented using computational fluid dynamics software based on the finite volume method (such as ANSYS Fluent). The simulation uses the two-dimensional / three-dimensional incompressible Navier-Stokes equations, and the turbulence model can be the SST k-ω model. The inlet boundary is set as a velocity inlet condition with the non-uniform velocity distribution obtained in step S1 applied, and the outlet is set as a pressure outlet condition. The mesh should use structured quadrilateral / hexahedral meshes as much as possible, with local refinement in the attached curved surface and feedback channel regions. The time step is set to 1 / 200 to 1 / 500 of the characteristic period to ensure that the complete oscillation period is captured.

[0043] like Figure 6 As shown, when a fluid medium such as gas or liquid enters the symmetrical feedback fluid oscillator through a 90° bend in the pipe before the inlet, the incoming flow velocity becomes distorted, causing the fluid oscillator to fail. Specifically, Figure 6 The streamline diagram obtained from the simulation of Comparative Example 1 (symmetric structure) under distorted incoming flow conditions shows that there is basically no oscillation effect.

[0044] Figure 7 and Figure 8 The asymmetric feedback channel fluid oscillator for compensating inlet distortion described in Example 1 demonstrates the internal streamline distribution characteristics at two typical moments within a complete oscillation cycle under the same inlet 90° bend distortion inlet flow conditions. This visually presents the core working process of the present invention, which enables the jet to achieve stable alternating wall oscillation after accurately offsetting inlet distortion through an asymmetric structure.

[0045] After the fluid undergoes a velocity distribution distortion due to the 90° bend in the pipe 10 before the inlet, it is injected at high speed into the oscillating chamber 2 from the inlet nozzle 1. Due to the Coanda effect, the mainstream initially adheres to a curved surface on one side of the wall. Specifically, Figure 7 The corresponding state of the jet adhering to the first attached curved surface 3. Figure 8 This corresponds to the state of the jet adhering to the second attached wall surface 4 after the jet has switched. Due to the flow restriction effect of the outlet section 7, a mainstream area where the main flow directly flows to the outlet and a natural diversion area where backflow occurs will naturally form downstream of the oscillating chamber 2: When the jet adheres to the first attached wall surface 3, part of the fluid enters the first natural diversion area 8 and flows back to the upstream root of the inlet nozzle 1 through the first feedback channel 5; when the jet adheres to the second attached wall surface 4, part of the fluid enters the second natural diversion area 9 and flows back to the upstream root of the inlet nozzle 1 through the second feedback channel 6. For ease of description, the backflow area near the first attached wall surface 3 is referred to as the first natural diversion area 8, and the backflow area near the second attached wall surface 4 is referred to as the second natural diversion area 9. The two are formed naturally by the jet attachment effect and do not require physical separation.

[0046] The feedback fluid flowing back creates reverse pressure upstream of the inlet nozzle, filling the separation bubbles in the oscillating chamber 2 and continuously pushing the main stream away from the current attached wall surface, deflecting it towards the other attached wall surface. This process repeats itself, with the main jet periodically alternating between the first attached wall surface 3 and the second attached wall surface 4, ultimately forming a symmetrical periodic oscillating jet at the outlet section 7 with a basically stable jet velocity and a jet direction that continuously sweeps and oscillates within a preset angle range.

[0047] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments and comparative examples. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Example 1 This embodiment provides an asymmetric feedback channel fluid oscillator to compensate for inlet distortion. The application scenario is as follows: a 90° elbow is installed before the oscillator inlet (a typical upstream pipeline disturbance), the straight pipe section between the elbow and the oscillator inlet is one pipe diameter (1D), the working medium is liquid water, and the designed operating Reynolds number range is 1000~10000. In this embodiment, the fluid is water.

[0049] like Figure 4 As shown, the oscillator in this embodiment includes an inlet nozzle 1, an oscillation chamber 2, a first attached wall surface 3, a second attached wall surface 4, a first feedback channel 5, a second feedback channel 6, an outlet section 7, a first natural diversion zone 8, a second natural diversion zone 9, an elbow pipe 10, a strong attached wall side 11, and a weak attached wall side 12.

[0050] The inlet nozzle 1 is a contraction type nozzle with a throat width of 1 mm and a contraction ratio of 3:1, and is located at the upstream inlet end of the oscillation chamber 2; the first attached wall curved surface 3 and the second attached wall curved surface 4 are respectively located on the left and right inner walls of the oscillation chamber 2, with a radius of curvature of 2 mm each; the outlet axis of the inlet nozzle 1 is deflected about 2° towards the weakly attached wall side 12; the effective length of the oscillation chamber 2 is 1.5 mm and the width is 4 mm; the outlet section 7 is located at the downstream end of the oscillation chamber 2, and is a single-outlet swept outlet with an outlet width of 3 mm.

[0051] The two ends of the first feedback channel 5 are respectively connected to the first natural diversion zone 8 downstream of the oscillation chamber 2 and the upstream root of the inlet nozzle 1, and the two ends of the second feedback channel 6 are respectively connected to the second natural diversion zone 9 downstream of the oscillation chamber 2 and the upstream root of the inlet nozzle 1.

[0052] In this embodiment, a 90° elbow pipe is installed before the oscillator inlet. Figure 2The velocity distribution at the AA cross section is distorted, and its typical velocity distribution contour map is shown below. Figure 3 As shown in the figure, it is clear that the flow velocity at one end of the cross-section is significantly higher than that at the other end. Since the bend shape and cross-section position are consistent, the velocity distribution cloud map at the inlet cross-section is the same regardless of whether the downstream structure of the oscillator is symmetrical or asymmetrical. Due to the influence of the inlet bend, the flow velocity on the left side of the incoming flow is higher in this embodiment, and the jet naturally deflects to the left. Therefore, the left side is the strong attachment side 11, and the right side is the weak attachment side 12. The first feedback channel 5 corresponds to the feedback channel on the strong attachment side, and the second feedback channel 6 corresponds to the feedback channel on the weak attachment side. The flow cross-sectional area of ​​the first feedback channel 5 is 1.2 mm², and the flow cross-sectional area of ​​the second feedback channel 6 is 0.8 mm², with the cross-sectional area of ​​the feedback channel on the strong attachment side being 50% larger than that on the weak attachment side. The length of the first feedback channel 5 is 8 mm, and the length of the second feedback channel 6 is 10 mm, with the length of the feedback channel on the strong attachment side being 20% ​​shorter than that on the weak attachment side.

[0053] Meanwhile, in this embodiment, the radius of curvature of the first attached wall surface 3 is adjusted to 2.2 mm, which is slightly larger than the radius of curvature of the second attached wall surface 4 (2 mm), further weakening the attachment effect on the strong attachment side.

[0054] Example 2 This embodiment provides an asymmetric design method for a fluid oscillator to compensate for inlet distortion, targeting the same scenario as in Embodiment 1, such as... Figure 5 As shown, it includes the following steps: S1. Incoming Flow Distortion: For the pipe structure with a 90° bend before the inlet and a straight pipe section of 1D, the flow velocity distribution data of the oscillator inlet section is obtained through Fluent numerical simulation. It is determined that the flow velocity on the left side of the incoming flow is higher and the non-uniformity is 35%. The left side is the strong wall-attached side and the right side is the weak wall-attached side. S2. Simulation verification of the benchmark symmetrical model: A benchmark oscillator model with a symmetrical structure is established. The cross-sectional area of ​​the feedback channel is 0.8 mm² and the length is 10 mm. The distorted incoming flow obtained in step S1 is used as the inlet boundary condition. Unsteady numerical simulation is performed. The critical oscillation Reynolds number of the benchmark model is 3500. When Re < 3500, oscillation cannot start. When Re = 5000, the ratio of jet attachment time on both sides is 72%:28%, and the oscillation is seriously asymmetrical. S3. Iterative Design of Asymmetric Feedback Channel Parameters: Taking the strong attachment side as the core adjustment object, the cross-sectional area of ​​the feedback channel on the strong attachment side is increased first, while its length is shortened simultaneously to establish an asymmetric structural model. With the goal of minimizing the critical start-up Reynolds number under the premise that the jet attachment time ratio on both sides reaches a preset symmetry threshold of 48%:52%, after 8 rounds of simulation iterations, the optimal parameters are determined as follows: cross-sectional area of ​​1.2mm² and length of 8mm on the strong attachment side, cross-sectional area of ​​0.8mm² and length of 10mm on the weak attachment side, and the radius of curvature of the attachment surface on the strong attachment side is simultaneously optimized to 2.2mm. S4. Full-condition stability verification: Within the operating range of Re=1000~10000, the optimized asymmetric model was simulated under full conditions. The verification results showed that the critical oscillation start-up Reynolds number was 1200. When the Reynolds number ≥1200, the model could stably start oscillation within its operating range without jet lock-up. The proportion of time spent attaching to both sides was stable between 47% and 53%, and the linearity error between the oscillation frequency and the flow rate was less than 3%. S5. Prototype Calibration and Optimization: Based on the optimal parameters obtained from the simulation, a prototype was fabricated using photosensitive resin 3D printing. The asymmetric parameters were fine-tuned and calibrated through particle image velocimetry (PIV) and pressure sensor testing, ultimately resulting in a compensated fluid oscillator consistent with the simulation results.

[0055] Comparative Example 1 This comparative example is a symmetrically structured reference fluid oscillator. The main difference between this and Example 1 is the symmetrical design of the feedback channel. Furthermore, since Comparative Example 1 uses a symmetrical feedback channel design, it does not involve the distinction between the first natural flow divider 8, the second natural flow divider 9, the strong wall-attached side 11, and the weak wall-attached side 12 as in Example 2.

[0056] The fluid used in this comparative example is water. Specific parameters are as follows: the cross-sectional area of ​​both the first and second feedback channels is 0.8 mm², and the length is 10 mm; the radius of curvature of the two attached wall surfaces is 2 mm. Except for the above parameters, the remaining geometric structure is consistent with Example 1.

[0057] Effect verification The asymmetric oscillator of Example 1 and the symmetric oscillator of Comparative Example 1 were simulated and experimentally tested under the exact same inlet elbow distortion flow conditions. The core performance comparison is as follows: Oscillation characteristics: The critical oscillation Reynolds number for Comparative Example 1 is 3500. When Re < 3500, it cannot start oscillation at all, and the jet locks up on one side. The critical oscillation Reynolds number for Example 1 is 1200. It can start oscillation stably in the working range of Re = 1200 to 10000 without lock-up problems.

[0058] Oscillation symmetry: In Comparative Example 1, when Re=5000, the attachment time ratio of the two jets is 72%:28%, and the oscillation is severely asymmetrical; In Example 1, under the same working conditions, the attachment time ratio of the two jets is 49%:51%, which is close to complete symmetry, and the amplitude and swing angle symmetry of the oscillating jet are restored to the level of uniform inflow.

[0059] Frequency linearity: The linearity error between the oscillation frequency and flow rate in Comparative Example 1 is 18.7%, and the linear relationship is completely destroyed; the frequency-flow rate linearity error in Example 1 is 2.8%, which maintains a good linear relationship and can meet the requirements of high-precision scenarios such as flow measurement.

[0060] Pressure loss: The inlet and outlet pressure drop of Example 1 was reduced by 11.3% compared with Comparative Example 1. The minimalist design without additional flow diversion structure significantly reduced local flow resistance and significantly improved energy efficiency.

[0061] The above verification results show that the asymmetric feedback channel design of the present invention can effectively compensate for the inflow distortion caused by upstream pipeline disturbances (such as bends), effectively solve the problems of oscillation failure and asymmetric oscillation of symmetrical oscillators, and at the same time, it does not require additional installation space, thus demonstrating significant technological progress and practical value.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An asymmetric feedback channel fluid oscillator for compensating for inlet distortion, comprising an inlet nozzle (1), an oscillation chamber (2), a first attached wall surface (3), a second attached wall surface (4), a first feedback channel (5), a second feedback channel (6), and an outlet section (7); the inlet nozzle (1) is disposed at the upstream inlet end of the oscillation chamber (2), the first attached wall surface (3) and the second attached wall surface (4) are respectively disposed on the left and right inner walls of the oscillation chamber (2), and the outlet section (7) is disposed at the downstream end of the oscillation chamber (2); the two ends of the first feedback channel (5) are respectively connected to the first natural diversion zone (8) downstream of the oscillation chamber (2) and the upstream root of the inlet nozzle (1), and the two ends of the second feedback channel (6) are respectively connected to the second natural diversion zone (9) downstream of the oscillation chamber (2) and the upstream root of the inlet nozzle (1); Its features are, The first feedback channel (5) and the second feedback channel (6) are asymmetrical structures, which match the distortion of the incoming flow velocity distribution caused by the disturbance of the upstream pipeline before the inlet of the fluid oscillator; Among them, due to the distortion of the incoming flow velocity distribution, the jet naturally deflects to one side as the strong attachment side (11) and the other side as the weak attachment side (12); the flow cross-sectional area of ​​the feedback channel corresponding to the strong attachment side (11) is greater than the flow cross-sectional area of ​​the feedback channel corresponding to the weak attachment side (12).

2. The asymmetric feedback channel fluid oscillator for compensating inlet distortion according to claim 1, characterized in that, The length of the feedback channel corresponding to the strong attachment side (11) is less than the length of the feedback channel corresponding to the weak attachment side (12).

3. The asymmetric feedback channel fluid oscillator for compensating inlet distortion according to claim 2, characterized in that, The flow cross-sectional area of ​​the feedback channel corresponding to the strong attachment side (11) is 10% to 50% larger than that of the feedback channel corresponding to the weak attachment side (12); the length of the feedback channel corresponding to the strong attachment side (11) is 5% to 30% shorter than that of the feedback channel corresponding to the weak attachment side (12).

4. The asymmetric feedback channel fluid oscillator for compensating inlet distortion according to claim 1, characterized in that, The radius of curvature of the wall surface corresponding to the strong wall side (11) is greater than the radius of curvature of the wall surface corresponding to the weak wall side (12).

5. The asymmetric feedback channel fluid oscillator for compensating inlet distortion according to claim 1, characterized in that, The outlet axis of the inlet nozzle (1) is deflected toward the weakly attached wall side (12) by an angle of 1° to 5°.

6. The asymmetric feedback channel fluid oscillator for compensating inlet distortion according to any one of claims 1 to 5, characterized in that, The upstream pipeline disturbance includes the elbow pipe (10), and the length of the straight pipe section between the elbow pipe (10) and the inlet of the fluid oscillator is less than 5 times the pipe diameter.

7. An asymmetric design method for a fluid oscillator with compensated inlet distortion, used to design the asymmetric feedback channel fluid oscillator with compensated inlet distortion as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Incoming flow distortion: For the upstream pipeline disturbance structure preset before the fluid oscillator inlet, the velocity distribution data of the fluid oscillator inlet section is obtained through numerical simulation or flow field test, and the direction and non-uniformity of the incoming flow distortion, as well as the strong wall-attached side (11) and the relatively weak wall-attached side (12) of the jet's natural bias are determined. S2. Simulation verification of the benchmark symmetric model: Establish a benchmark fluid oscillator model with a symmetric structure. Use the distorted incoming flow obtained in step S1 as the inlet boundary condition and perform unsteady numerical simulation to obtain the start-up characteristics, oscillation symmetry, and critical start-up Reynolds number of the benchmark fluid oscillator model under the distorted incoming flow, and determine the failure boundary of the benchmark model. S3. Iterative design of asymmetric feedback channel parameters: Taking the strong attachment wall side (11) as the core adjustment object, the flow cross-sectional area of ​​the feedback channel corresponding to the strong attachment wall side (11) is increased first, and the length of the feedback channel corresponding to the strong attachment wall side (11) can be shortened to establish an asymmetric structure oscillator model; with the minimum critical start-up Reynolds number as the optimization objective under the premise that the proportion of jet attachment time on both sides reaches the preset symmetry threshold, the optimal combination of asymmetric feedback channel parameters is determined through multiple rounds of numerical simulation iteration; S4. Full-condition stability verification: Within the preset operating Reynolds number range, perform full-condition unsteady numerical simulation on the asymmetric structure oscillator model obtained in step S3 to verify the start-up characteristics, oscillation symmetry, and frequency-flow linearity, ensuring that there are no jet lock-up or oscillation instability problems within the full-condition range. S5. Prototype Calibration and Optimization: Based on the optimal parameters verified in step S4, process the prototype according to the principle. Through experimental testing, perform final calibration and optimization of the asymmetric parameters to obtain the final compensated fluid oscillator.

8. The asymmetric design method for fluid oscillator with compensated inlet distortion according to claim 7, characterized in that, In step S1, the upstream pipeline disturbance includes the elbow pipe (10), and the length of the straight pipe section between the elbow pipe (10) and the fluid oscillator inlet is less than 5 times the pipe diameter.

9. The asymmetric design method for a fluid oscillator to compensate for inlet distortion according to claim 7, characterized in that, In step S3, the flow cross-sectional area of ​​the feedback channel corresponding to the strong attachment side (11) is 10% to 50% larger than the flow cross-sectional area of ​​the feedback channel corresponding to the weak attachment side (12); the length of the feedback channel corresponding to the strong attachment side (11) is 5% to 30% shorter than the length of the feedback channel corresponding to the weak attachment side (12).

10. The asymmetric design method for a fluid oscillator to compensate for inlet distortion according to claim 7 or 9, characterized in that, Step S3 also includes asymmetric optimization iterations of the wall surface curvature, the split wedge position, and the inlet nozzle deflection angle.

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