KR102363305B1 - Fluidic Oscillator Pair with Phase control function for Phase synchronization - Google Patents

Abstract

The present invention relates to a fluid oscillator pair with a phase control function for phase synchronization, which is configured by connecting two or more corresponding fluid oscillators, which have an inlet nozzle at an upper part and an outlet nozzle at a lower part, by a bridge, comprises an inclined inner wall and a recirculation area chamber inside a main body of the fluid oscillator, and includes a feedback loop for fluid circulation from an inlet port of a lower part of the main body and to an outlet port of an upper part of the main body. The fluid oscillator pair reduces phase delay of the synchronization by phase coincidence or phase symmetry.

Description

Fluidic Oscillator Pair with Phase control function for Phase synchronization

The present invention relates to a fluid vibrator, and more particularly, to a fluid vibrator pair having a phase control function for phase synchronization.

In general, a fluid vibrator is a device that induces vibration of an outlet flow by using the specificity of its shape without a separate driving unit. , AFC (Active Flow Control), combustion control, heat transfer improvement, etc.

The sweeping jet sprayed by the fluid vibrator has the characteristics described above, and compared to the steady-state jet flow, the spraying area is relatively wide, and the flow pattern and flow characteristics such as vortices near the outlet are also different. , based on these characteristics, the fluid vibrator has been applied to research for various purposes such as control of aerodynamic phenomena, improvement of cooling efficiency, and improvement of fuel mixing efficiency.

In the case of AFC (Active Flow Control) mounted on the wing of an aircraft and used for the purpose of aerodynamic control, Lin et al. According to the study ["An Overview of Active Flow Control Enhanced Vertical Tail Technology Development"], a flight test was performed with a fluid vibrator array mounted on the vertical tail wing for the purpose of controlling the delamination phenomenon near the wing of an airplane, and the amount of increase in lift was compared with a vortex generator.

A study by Camci et al. ["Forced convection heat transfer enhancement using a self-oscillating collision planar jet." J. Heat Transfer 124, no. 4 (2002): 770-782.] compared the Nusselt number with increasing Reynolds number of a steady-state jet flow and a vibrating jet (sweeping jet), Hossain et al. . [8] compared the Nusselt number according to the curvature of the jet wall of a steady-state jet flow and a vibrating jet (sweeping jet).

YongjiaWu2018's study compared the heat transfer area increase efficiency of the vibrating jet (sweeping jet) of an angular fluid vibrator with a straight shape and a fluid vibrator with a curved shape through LES (Large Eddy Simulation).

A study by Ostermann et al. ["The interaction between a spatially sweeping jet emitted by a fluidic oscillator and a cross-flow", Journal of Fluid Mechanics 863 (2019): 215-241.] )) and the behavior in the cross-flow of the steady-state jet flow were observed through particle image velocimetry (PIV), and the penetration length from the wall to the vertical direction was compared.

Meanwhile, in order to observe the mixing efficiency when a fluid vibrator is applied as an injector, a study by Bobusch et al. ["Investigation of fluidic devices for mixing enhancement for the shockless explosion combustion process", In Active Flow and Combustion Control 2014, pp. 281-297. Springer, Cham, 2015.] simulated shockless explosion combustion (SEC) with water and a fluorescent dye and quantified the unmixedness through particle image velocimetry (PIV).

A study by Lee et al. ["A Numerical Study on the Characteristics of Air-Fuel Mixing Using a Fluidic Oscillator in Supersonic Flow Fields." Energies 12, no. 24 (2019): 4758.] proposes indicators to evaluate mixing efficiency, such as penetration length and flammable area, of the outlet flow of a fluid vibrator in a domain simulating a combustion chamber in a scramjet. Compared with the flow, it was quantified through computational analysis.

While studies that observed and analyzed the internal and external flow of a single fluid vibrator have been actively conducted through experiments and computational analysis, two or more fluid vibrators are connected to observe the interaction and a new phase-control technique (Phase-control) method) has only recently received attention. This is related to the circumstance that studies on Active Flow Control (AFC) applying a fluidic oscillator array, heat transfer techniques, and enhancement of mixing efficiency have entered the countdown (a study by Gokoglu et al. ["Numerical] Studies of an Array of Fluidic Diverter Actuators for Flow Control"], a study by Lin et al. ["An Overview of Active Flow Control Enhanced Vertical Tail Technology Development "], a study by Kim et al. ["Effects of Installation Conditions of Fluidic Oscillators on Control of Flow Separation." AIAA Journal 57, no. 12 (2019): 5208-5219.]).

The initial phase of each fluid vibrator cannot be predicted due to the nature of the fluid vibrator, where vibration is induced by the pressure difference that occurs irregularly between the feedback ports. Since it is unpredictable, there is a demand for a technique that can synchronize the phases between the fluid vibrators.

A study by Tomac et al. [“Phase-synchronized fluidic oscillator pair,” AIAA Paper 2017-3314, 2017.] is a type of fluid oscillator that causes the synchronization of the outlet flow by sharing inner feedback loops. was introduced, and later studies by xinwen et al. ["Interaction of dual sweeping collision jets at different Reynolds numbers." Physics of Fluids 30, no. 10 (2018): 105105.], a study by Bohan et al. ["sweeping jets Issuing From the Face of a Backward-Facing Step." Journal of Fluids Engineering 141, no. 12 (2019).], air-to-air feedback 2020, and other studies applying the fluid vibrator pair were carried out one after another.

에서 안정적으로 위상 일치(phase-in)됨을 확인하였으며 출구 유동 사이에 충돌로 인한 소용돌이가 생성되어 역류 유동(upwash flow)을 생성하는 것이 관찰되었다. A study by xinwen et al. ["Interaction of dual sweeping collision jets at different Reynolds numbers." Physics of Fluids 30, no. 10 (2018): 105105.] observed the flow characteristics when the outlet flow according to the Reynolds number of the fluid vibrator pair collided with the wall,

was confirmed to be stably phase-in, and it was observed that a vortex was generated due to collision between the outlet flows to generate an upwash flow.

에서는 진동 모션(sweeping motion)의 변화가 관찰되었는데, 진동 제트(sweeping jet)이 안쪽에서 바깥쪽으로 움직일 때의 속도가 반대의 경우보다 컸으며 위상에 따른 속도변화 추이 또한 급격하게 나타났고, 낮은 레이놀즈수(Reynolds number)에서 관찰되었던 벽(wall) 소용돌이들의 구별이 어려웠다.

A change in sweeping motion was observed in , and the speed when the sweeping jet moved from the inside to the outside was larger than the opposite case, and the speed change according to the phase also appeared rapidly, and the low Reynolds number It was difficult to distinguish the wall vortices observed in (Reynolds number).

A study by Bohan et al. ["sweeping jets Issuing From the Face of a Backward-Facing Step", Journal of Fluids Engineering 141, no. 12 (2019)] of parallel jets, a single fluid oscillator, a pair of separated fluid oscillators, and a study of Tomac et al. [Phase-synchronized fluidic oscillator pair,” AIAA Paper 2017-3314, 2017.] The frequency, oscillation angle, and jet penetration depth of the in-phase fluid vibrator pair were observed through the Schliren method, while the feedback chamber of the in-phase fluid vibrator pair was observed. A fluid vibrator pair that induces phase-out by adding a partition to . As a result, the jet penetration depth of the single oscillator was larger than that of the in-phase fluid oscillator pair, and the oscillation angle of the single oscillator and the in-phase fluid oscillator were Both pairs showed a tendency to be proportional to the Reynolds number.

The research trend of fluid oscillator array to date is mainly research on fluidic oscillator array that causes synchronization, but fuel mixing efficiency according to the vortex generated by the outlet flow (a study by Eroglu et al. ["Structure, penetration, and mixing of pulsed jets in crossflow." AIAA journal 39, no. 3 (2001): 417-423.]) and vortex in wakes depending on the phase (Ostermann et al.'s study ["The interaction between a spatially sweeping jet emitted by a fluidic oscillator and a cross-flow", Journal of Fluid Mechanics 863 (2019): 215-241. ]), it is predictable that the flow characteristics near the outlet and in the wake of a fluidic oscillator array in which several fluidic oscillators are arranged are also classified according to the phase difference. Therefore, there is a need to propose a phase-control method that can subdivide the phase difference by being more intuitive and easy to deform.

ShiqiWang's study ["Experimental and Numerical Study of Micro-Fluidic Oscillators for Flow Separation Control." PhD diss., Toulouse, INSA, 2017.] observed the phase difference of the outlet flow for each case by connecting the feedback ports of two fluid vibrators with a tube. A fluid vibrator without a recirculation chamber The type was applied, and an experiment of a fluidic oscillator array with a port connected with a tube was performed. However, the effect of the recirculation was not considered, and the spatial dimension of the device increased due to the tube connection, so it was difficult to apply the shape as an aerodynamic control device in an aircraft wing or a cooling device in a turbine blade. there was

1 shows the vibration mechanism of a general single fluid vibrator, the fluid vibrator includes an inclined inner block and a recirculation chamber inside the body, and extends from one side of the lower body to the other side. A type having a feedback loop, an inlet port positioned at a connection portion between the lower side of the main body and the feedback loop, and an outlet port positioned at a connecting portion between one side of the upper body and the feedback loop was used.

In the 2019 AIAA study by SHPark et al., the corresponding fluid vibrator type showed that the main flow was closely adhered to the inner wall of the fluid vibrator due to pressure difference and viscosity, and a portion of the main flow introduced into the feedback loop through the inlet port, i.e., the feedback flow, was the feedback flow. It is discharged through the loop to the outlet port. The feedback flow discharged to the outlet port causes separation of the main flow at the inner wall to create a recirculation area between the main flow and the inner wall, wherein the generated recirculation area directs the main flow to the opposite inner wall. The phase is symmetrical by being pushed by the , and the oscillation of the exit jet occurs through the mechanism.

In the study of 'ECLee2019', the occurrence of oscillation of the outlet jet of the fluid vibrator is 1) a step in which a part of the main flow enters the feedback loop through the inlet port, and 2) the incoming flow flows from the feedback loop through the outlet port. It can be abbreviated to three stages: venting causing flow separation, and 3) venting flow creating a recirculation region between the main flow and the inner wall. In this case, the width of the feedback loop and the length of the feedback loop affect the frequency and the vibration angle.

To date, several types of fluid vibrator arrays have been developed for the purpose of controlling the phase of the outlet flow, but their application is difficult because the shape factor that can be deformed is limited to the feedback channel and the overall size is increased. The variation of outlet flow control is still focused on synchronization, so it is difficult to observe the interaction of various flows. However, in order to quantify the performance by observing the interacting flow characteristics near the exit and classifying the resulting phenomena, the need to conduct additional research on a new phase control technique is highlighted.

Accordingly, the present invention was developed to solve the above problems, and the purpose of the present invention is to provide a fluidic oscillator pair that connects a feedback loop and a recirculation chamber by a bridge, and enables phase control through this. have.

In order to achieve the above object, the present invention provides an embodiment of a fluid vibrator pair having a total of four types of bridge connection structures, and the interaction between fluid vibrators classified according to the bridge connection position by performing analysis on them and the characteristics of the outlet flow and the phase change are observed.

According to the present invention, as a fluid vibrator pair configured by connecting two or more corresponding fluid vibrators having an inlet nozzle at the upper part and an outlet nozzle at the lower part by a bridge, the fluid vibrator body includes an inclined inner wall and a recirculation area chamber. and reduce the phase lag of synchronization through phase coincidence or phase symmetry from the configuration of the fluid vibrator pair having a feedback loop for fluid flow from the inlet port at the bottom of the body to the outlet port at the top of the body be able to

The first type of fluid vibrator pair connects the inlet ports of the inner feedback loops (LR, RL) among the feedback loops of both fluid vibrators with a bridge, and the flow introduced through the inlet port is shared with the other fluid vibrator through the bridge and make it interactive.

The second type of fluid vibrator pair connects the outlet ports of the inner feedback loops (LR, RL) among the feedback loops of both fluid vibrators with a bridge, and the flow flowing out through the outlet ports is shared with the other fluid vibrator through the bridge and make it interactive.

The third type of fluid vibrator pair connects the inlet port and the outlet port of the inner feedback loops (LR, RL) of the feedback loops of both fluid vibrators with a bridge, respectively, and flows in through the inlet port and through the outlet port The flow outflow is shared with the other fluid vibrator through the bridge and configured to interact.

The fourth type of the fluid vibrator pair connects the inlet port, the outlet port, and the recirculation chamber chamber of the inner feedback loops (LR, RL) of the feedback loops of both fluid vibrators by a bridge, respectively, and includes each of the inlet port, the outlet port, and Flow through a bridge connected between the recirculation chamber chambers is configured to interact and share with the opposing fluid vibrator.

In the present invention, a fluid vibrator type composed of a feedback loop and an inlet and outlet nozzle of a recirculation chamber (Recirculation chamber) is applied. The concept of inter-bridge phase control, in which the roles of each port are clearly distinguished, was introduced.

In order to reduce the phase lag of synchronization, an in-phase fluidic oscillator pair was proposed, which removed the feedback loop and connected a bridge, and a phase symmetric fluidic oscillator pair (out -phase fluidic oscillator pair) and a shape to which this technique is applied was also presented.

In addition, the characteristics of the fluid vibrator pair according to the bridge connection for each feedback port, the internal flow structure, and the synchronization mechanism were observed, while the recirculation chamber of each fluid vibrator was connected with a bridge to interact between the fluid vibrators. A new phase control concept was proposed by analyzing how it changes according to the flow rate shared through this bridge and the behavior of the recirculation region.

From the above-mentioned characteristics, the present invention provides an inter-bridge phase control (inter-bridge phase control) connecting at least the inlet port, the outlet port, and the recirculation chamber chamber of the inner feedback loops (LR, RL) among the feedback loops of both fluid vibrators by a bridge. By introducing the concept of control, phase control to reduce the phase lag of synchronization becomes possible.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows the vibration mechanism of a single fluid vibrator having an inclined inner wall;
2 is a view showing a first embodiment ('caseA') for phase-synchronized of a fluid vibrator pair according to the present invention;
3 is a view showing a second embodiment ('caseB') for phase-synchronized of a fluid vibrator pair according to the present invention;
4 is a view showing a third embodiment ('caseC') for phase-synchronized of a fluid vibrator pair according to the present invention;
5 is a view showing a fourth embodiment ('caseD') for phase-synchronized of a fluid vibrator pair according to the present invention;
6 is a diagram showing the mass flow rate (kg/s) over time in the nozzle neck and outer feedback loops of the fluid vibrator pair 'caseA' during three cycles;
7 is a diagram showing the Mach number, pressure profile and stream line of the fluid vibrator pair 'caseA' during one cycle;
8 is a diagram showing the vibration angle according to time of the fluid vibrator pair 'caseA' during one cycle;
9 is a diagram showing the mass flow rate (kg/s) over time in the nozzle neck and outer feedback loops of the fluid vibrator pair 'caseB' during three cycles;
10 is a diagram showing the Mach number, pressure profile and stream line of the fluid vibrator pair 'caseB' during one cycle;
11 is a diagram showing the vibration angle according to time of the fluid vibrator pair 'caseB' during one cycle;
12 is a diagram showing the mass flow rate (kg/s) over time in the nozzle neck and outer feedback loops of the fluid vibrator pair 'caseC' during three cycles;
13 is a diagram showing the Mach number, pressure profile and stream line of the fluid vibrator pair 'caseC' during one cycle;
14 is a diagram showing the vibration angle according to time of the fluid vibrator pair 'caseC' during one cycle;
15 is a diagram showing the mass flow rate (kg/s) over time in the nozzle neck and outer feedback loops of the fluid vibrator pair 'caseD' during three cycles;
16 is a diagram showing the Mach number, pressure profile and stream line of the fluid vibrator pair 'caseD' during one cycle;
17 is a diagram showing the vibration angle according to time of the fluid vibrator pair 'caseD' during one cycle.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings and examples.

In the following embodiments, the illustration and description are omitted except for essential parts in describing the invention, and the same reference numerals are given to the same and similar elements throughout the specification, and detailed descriptions thereof are omitted without repeating them. do.

In the present invention, the fluid vibrator basically includes an inclined inner block and a recirculation chamber inside the body, as in FIG. 1, and extends from one side of the lower part of the body and is connected to the other side. ), and a type having an inlet port positioned at the connection part of the lower body side and the feedback loop, and an outlet port positioned at one side of the upper body part and the connection part of the feedback loop was applied, and to increase the efficiency of phase control For this purpose, the concept of inter-bridge phase control, in which the shape factor can be easily modified and the roles of each feedback port is clearly distinguished, was introduced.

That is, in order to reduce the phase lag of synchronization, the shape and phase symmetry of an in-phase fluidic oscillator pair in which a feedback loop is connected between a pair of fluid oscillators by a bridge The shape of the out-phase fluidic oscillator pair is presented, and through this, the characteristics of the fluid oscillator pair according to the bridge connection for each port of the feedback loop, the internal flow structure, and the synchronization mechanism are observed, while each fluid By connecting the recirculation area chamber of the vibrator with a bridge, a new phase control concept was proposed by analyzing how the interaction between the fluid vibrators changes according to the flow rate shared through the bridge and the behavior of the recirculation area.

2 to 5 show the geometric shapes of a fluid vibrator pair having various bridge connection structures according to the present invention. For reference, the external shape of each fluid vibrator applied in the present invention is a fluid vibrator used in the study of 'SHPark2019AIAA' referenced. In addition, in this embodiment, a certain distance (eg 40 mm) was applied to the distance between the center lines of both fluid vibrators of the fluid vibrator pair to secure a bridge section, and the outer feedback loop of the left fluid vibrator (L) was set to 'LL'. , the inner feedback loop was named 'LR', the outer feedback loop of the right fluid vibrator (R) was named 'RR', and the inner feedback loop was named 'RL', respectively.

Figure 2a shows a first embodiment (hereinafter, 'caseA') for phase-synchronized of a fluid vibrator pair, and inner feedback loops (LR, RL) among the feedback loops of both fluid vibrators. of the inlet port was connected by a bridge (Inport bridge), and the flow introduced through the inlet port was designed to share and interact with the other fluid vibrator through the bridge. 'caseA' is separated from the main flow by connecting the inlet ports of the inner feedback loops, and the interaction between the progress direction of the inflow and the relative flow introduced into the feedback loop is shown in FIG. 2B.

According to FIG. 2B, the flow ① introduced into the inlet port is discharged to the inlet port of the opposing fluid vibrator through the inlet port bridge and directly pressurizes the main flow, so that the main flow of the opposing fluid vibrator is in close contact with the outer wall. . And, when the feedback flow② flows into the inlet port of the inner feedback loops (LR, RL), it proceeds by dividing it into LR and RL, and then is discharged to the outlet ports of LR and RL at regular intervals to flow the fluid A phase difference occurs by causing a separation at the inner wall of the main flow for the vibrator L and the fluid vibrator R.

Figure 3a shows a second embodiment (hereinafter 'caseB') for phase-synchronized of a fluid vibrator pair, and bridges the outlet ports of the inner feedback loops (LR, RL) among the feedback loops of both fluid vibrators. (Outport bridge, outlet port bridge) is connected to the structure, and the flow flowing out through the outlet port is designed to share and interact with the fluid vibrator on the other side through the bridge. 'caseB' shows the interaction between the progress direction of the inflow separated from the main flow and introduced into the feedback loop and the relative main flow in FIG. 3B .

According to FIG. 3B, the feedback flow ① introduced into the inlet port of the inner feedback loop (LR, RL) is simultaneously discharged to the outlet ports of the fluid vibrator L and the fluid vibrator R through the outlet port bridge to the fluid vibrator L and the fluid vibrator R. It causes separation at the inner wall of the main flow to the flow, and each main flow is in close contact with the fluid vibrator L and the outer wall of the fluid vibrator R, resulting in phase symmetry.

4A shows a third embodiment (hereinafter 'caseC') for phase-synchronized phase-synchronized of a fluid vibrator pair, and among the feedback loops of both fluid vibrators, the inlet ports of the inner feedback loops (LR, RL) and It has a structure in which each of the outlet ports is connected by a bridge, and it is designed so that the flow flowing in through the inlet port and the flow flowing out through the outlet port share with the other fluid vibrator through the bridge and interact. 'caseC' connects the inlet ports and outlet ports of the inner feedback loops (LR, RL) to each other to help the interaction between the direction of inflow and the relative flow separated from the main flow and introduced into the feedback loop. 4b.

According to FIG. 4B, a part of the main flow ① that is in close contact with the inner wall of the fluid vibrator R flows into the outlet port bridge and is discharged to the outlet port of the counter fluid vibrator L, and the main flow in the counter fluid vibrator L It causes delamination at the inner wall of the flow. And, a part of the main flow in close contact with the inner wall ② flows into the inlet port bridge and is discharged through the inlet port of the counter fluid vibrator R to directly pressurize the main flow, so that the main flow is transferred to the outer wall , and phase symmetry occurs.

5A shows a fourth embodiment (hereinafter 'caseD') for phase-synchronized of a fluid vibrator pair, and inlet ports of inner feedback loops (LR, RL) among the feedback loops of both fluid vibrators. , the outlet ports, and the recirculation chamber chambers are each connected by a bridge, and the flow through the bridge connected between the inlet ports, the outlet ports, and the recirculation chamber chambers is designed to share and interact with the fluid vibrator on the other side. . In 'caseD', at the beginning of injection, the pressure inside the bridge is lower than in the outer feedback loop, so the main flow of each object is closely adhered to the inner wall and flows into the inner feedback loop. It simultaneously pushes out the main flow of the fluid vibrator object, and this effect creates a symmetry of the outlet flow.

The action of this flow is shown in FIG. 5B, in which a part of the main flow ① adhered to the inner wall flows into the outlet port bridge and is discharged to the outlet port of the counterpart fluid vibrator, and the inner wall of the main flow of the counterpart fluid vibrator cause flaking. And, a part of the main flow (②) closely adhered to the inner wall flows into the chamber bridge and is discharged into the recirculation chamber of the counterpart fluid vibrator, causing disruption of the recirculation area and directly pressurizing the main flow. In addition, a part of the main flow in close contact with the inner wall (③) flows into the inlet port bridge and is discharged to the outlet port of the counter fluid vibrator through the outlet port bridge to directly pressurize the main flow, and the main flow is brought into close contact with the outer wall. A symmetry of the outlet flow occurs.

Numerical approach

Commercial code Star-CCM+ 14.02.010-R8 was used for the flow analysis of the fluid vibrator pair according to the present invention. Numerical analysis of DES and LES has been used in the study of fluid vibrator recently (Dauengauer et al. [17]), but considering that it is a high-cost analysis, the main point of this study is the oscillation mechanism and characteristics ( In observing changes in characteristics), it was determined that the three-dimensional URANS (Unsteady Reynolds-Averaged Navier-Stokes) equation could be applied, and the three-dimensional URANS (Unsteady Reynolds-Averaged Navier-Strokes equations) modeling was applied. An ideal gas was assumed as the working fluid. As the coupled inviscid flux term, Roe FDS (Roe's Flux-Difference Splitting) was applied, and the inviscid flux at the interface was tertiary based on the Monotonic Upwind Scheme for Conservation Laws (MUSCL). It was calculated by the interpolation technique. As the turbulence model, the k-ω SST turbulence model (Menter et al. [18]), which is suitable for analyzing flow separation, was applied, and for the calculation of unsteadiness, a secondary implicit discretization in time was applied. became

The grid used for numerical analysis is an alignment grid, and a prism layer is applied to place a grid near the wall so that y+ is 1 or less. About 1 million grids are used for each fluid vibrator pair, and the time interval Analysis was performed by setting Δt of 2E-6s.

Validation

For validation of the analysis technique, a study by Lee et al. ["A Numerical Study on the Characteristics of Air-Fuel Mixing Using a Fluidic Oscillator in Supersonic Flow Fields." Energies 12, no. 24 (2019): 4758.], the pressure measurement results in the outer feedback loop of the shape tested under the conditions of NPR3.0 and the pressure calculation results over time calculated through computational flow analysis are The experimentally measured frequencies in the outer feedback loops (PL) (PR) and the central feedback loop (PC) were compared with those calculated through computational flow analysis.

PL(Hz) PC (Hz) PR(Hz) Experiment result
'hang2020' 687 1373 687 cfd result 667 1335 667 error 2.91% 2.77% 2.91%

The experimentally measured pressure value over time in the outer feedback loop PL and the shape of the pressure over time in the PL calculated by the analysis technique applied in the present invention showed good agreement, and the error in the maximum and minimum values was They were analyzed to be 3.8% and 0.5%, respectively. The frequency calculated in each feedback loop showed an error of less than 3% from the frequency measured experimentally (Table 1).

Results (relevant flow structures and properties depending on the type of bridge connection)

1) Evaluation of the first embodiment ('caseA') of the fluid vibrator pair

6, the mass flow rate over time in the nozzle throat and outer feedback loops (LL, RR) of the fluid vibrator pair 'caseA' for three cycles in FIG. , kg/s) are shown. The mass flow rate was calculated and presented by averaging the nozzle neck and the outer feedback loops of the fluid vibrator pair 'caseA'. The observation period was selected at a point in time showing a constant phase change and frequency after about ten cycles after the start of vibration.

At the beginning of the injection, the main flow of each fluid vibrator vibrates irregularly due to the pressure imbalance between the inlet ports without a feedback mechanism. First, it flows into the inlet port bridge. At the same time the flow is shared through the inlet port bridge, the flow is distributed to the inner feedback loops (LR, RL) connected to the inlet port bridge, and the feedback flow rate between each fluid vibrator is A difference occurred, which caused a phase difference between each fluid vibrator, and the pressure in the inlet port bridge and the flow rate to and from the inlet port bridge were changed. As a result, there was a difference in the total flow rate of each fluid vibrator, and as a result of calculating the total flow rate for three cycles, the total flow rate of the fluid vibrator L was derived to be 3.3% higher than the total flow rate of the fluid vibrator R. As a result of calculating the phase difference between the two fluid vibrators in the outer feedback loop, the phase difference of the fluid vibrator pair 'caseA' was calculated to be 21.0% of the period.

7 shows the Mach number, pressure contour, and streamline of the fluid vibrator pair 'caseA' during one cycle. The observation time points (a)-(c) in FIG. 7 were previously shown in FIG. 6 .

According to FIG. 7( a ), the main flow (hereinafter, the main flow R) of the fluid vibrator R is in close contact with the inner wall due to viscosity, and a part flows into the inlet port bridge. The flow discharged through the inlet port bridge applies a direct pressure to the lower portion of the main flow (hereinafter, the main flow (L)) of the fluid vibrator L (white dotted line; pressurizing action), and due to this, a part of the main flow (L) pushed in series flows into the inlet port (Inport) of the LL. After that, the feedback flow passing through the outer feedback loop LL is discharged to the outlet port of the LL and causes separation in the outer block of the main flow L (black dotted line. The main flow A recirculation zone whose role is to reverse the phase).

According to Figure 7 (b), the main flow (L) is pushed in the direction of the inner block (inner block) by the recirculation region developed due to separation, the main flow (R) flow to the inlet port bridge (inport bridge) In the discharged state, as the main flow L is surged, the pressure in the inlet port bridge increases (FIG. 7(bp)). Due to this, the flow flowing into the inlet bridge is distributed to LR and RL, and the dispersed flow is discharged through the outlet ports of LR and RL, respectively, and the main flow (L) and main flow (R) (acting that disrupts phase-in)

According to Figure 7 (c), the upper portion of the main flow (L) is separated from the inner block (inner block) by the flow discharged from the outlet port (outport) of the main flow (L) at the same time the lower portion of the main flow (L) is the inlet port bridge It adheres to the (inport bridge) and discharges the flow into the bridge. Due to this, the pressure at both the inlet port (Inport) and the outlet port (outport) of the RL is increased, so that the phase of the main flow (R) is aligned to the center.

According to Fig. 7(d), the flow discharged from the bridge presses the lower portion of the main flow R (white dotted line, phase-in induced action), so that the main flow R becomes the outer block. ) side, and a part of the main flow (R) in series flows into the inlet port (Inport) of RR. The incoming flow is discharged to the outlet port of the RR, causing separation in the outer block of the main flow R. On the other hand, the main flow L is pushed toward the outer block by the recirculation region developed due to separation in the inner block (phase-in breakdown, phase-symmetry (phase-in) out)).

According to Figure 7 (e), the main flow (R) is pushed toward the inner block (inner block) by the recirculation region developed due to separation from the outer block (a), the inlet port as in (a) A portion of the main flow (R) is introduced into the bridge (inport bridge) to apply pressure to the lower portion of the main flow (L). Accordingly, a part of the main flow (L) in close contact with the outer block flows into the inlet port of the LL and is discharged to the outlet port of the LL to the outer block of the main flow L. block), causing detachment.

8 shows sweeping angles (degrees) according to time (t ^* (s)) of the fluid vibrator pair 'caseA' during one cycle. The vibration angle was derived from the average position of the lowest pressure point based on the nozzle neck after observing the pressure change at each point over time for three periods on the nozzle exit surface. Angle and outward oscillation angle were derived respectively.

average frequency
(Hz) sweeping angle Average inward deflection
(deg) Average outward deflection
(deg) caseA 633 13 20

In Table 2 above, the sweeping characteristics of the fluid vibrator pair 'caseA' are shown. For frequency, referring to the frequency measurement point in 'Lee et al.'s study', the value obtained by converting the time-dependent mass flow change in the outer feedback loop through Fourier transform is converted into thermal cycles. were averaged and derived. Compared with the frequency of a single fluid vibrator (605±15 Hz(exp) (research by Lee et al.)), the frequency of the first embodiment ('caseA') showed an increase of about 5.0%. Similarly, the inward deflection and the outward deflection were averaged over the thermal cycle, respectively, and the outward deflection of the fluid vibrator pair 'caseA' Measured larger than the inward deflection, which is that the pressure at the inner feedback ports becomes smaller than the pressure at the outer feedback ports due to the addition of the inlet bridge, It was analyzed that the outward deflection of the outlet flow increased as the degree of adhesion of the main flow to the inner wall increased.

2) Evaluation of the second embodiment ('caseB') of the fluid vibrator pair

In Figure 9, the nozzle neck and the outer feedback loops (LL, RR) of the fluid vibrator pair 'caseB' during three cycles (Mass flow rate, kg/s) This appears. The observation period was selected at a point in time showing a constant phase change and frequency after about ten cycles after the start of vibration.

In the case of the fluid vibrator pair 'caseB' that connects the outlet ports of the inner feedback loops (LR, RL), the inlet ports ( Inports) and the pressure difference between the inlet ports (Inports) of the outer feedback loops (LL, RR), the main flow (L, R) is the inlet of each of the inner feedback loops (LR, RL) The flow flows into the port at the same time, and the phase difference occurs due to the difference in flow rate that is concentrated at the outlet bridge and then distributed to the outlet ports of each inner feedback loop. , a difference in the flow rate shared through the outlet port bridge also occurred. The mass flow rate at the nozzle neck of each fluid vibrator changed due to this, and finally, a difference in the total flow rate was caused. was drawn higher. As a result of calculating the phase difference in the outer feedback loops (LL, RR) of the fluid vibrator pair 'caseB', the phase difference between the two fluid vibrators of the fluid vibrator pair 'caseB' was calculated to be 12.1% of the period.

10 shows the Mach number, pressure contour, and streamline of the fluid vibrator pair 'caseB' during one cycle. The observation time points (a)-(c) in FIG. 10 are shown in FIG. 9 above.

According to Figure 10 (a), the pressure in the inner feedback loops (LR, RL) due to the outlet port bridge (outport bridge) connection to the outer feedback loops (LL, RR) ), the main flows (L, R) are pressed toward the inner block, and the outlet flows of the two fluid vibrators are gathered inward (phase-out). Then, the flow flows into the inlet ports of LR and RL and is concentrated at the outlet port bridge. The pressure in the bridge rises (FIG. 10(ap)) and the flow is discharged to the outlet ports of LR and RL, causing separation in the inner block of the main flows L and R. The outlet flow of both fluid vibrators is deflected outward (phase-out).

According to FIG. 10( b ), the recirculation region generated near the inner block develops due to delamination, and the main flows L and R are pushed to the outer block. Due to this movement, the flow enters the inlet ports of LL and RR and is discharged to the outlet ports of LL and RR to prevent separation from the outer block of the main flows L and R. cause.

According to FIG. 10(c), the recirculation region generated near the outer block develops due to the separation, and the main flows L and R are in close contact with the inner block, and the process of (a) is followed. Repeat.

In the case of fluid vibrator pair 'caseB' to which an outlet bridge is applied, the growth of the recirculation region in the inner block is slower than in the outer block due to the bridge connection. Due to this, a time difference occurs until the outlet flow reaches the maximum deflection angle when deflecting to the inner block and deflecting to the outer block, and this time difference occurs in the time bar shown in FIG. ) was calculated as 0.06T (0.1ms).

average frequency
(Hz) sweeping angle Average inward deflection
(deg) Average outward deflection
(deg) caseB 619 13 20

11 shows sweeping angles (degrees) according to time (t ^* (s)) of the fluid vibrator pair 'caseB' during one cycle. Table 3 above shows the sweeping characteristics of the fluid vibrator pair 'caseB', and the average vibration angle and frequency for thermal cycles was derived in the same way as the fluid vibrator pair 'caseA'. The frequency of a single fluid vibrator (605±15Hz(exp)) was increased by about 2.3% when compared with 'Lee et al.'s study'. Like the fluid vibrator pair 'caseA', the outward deflection of the fluid vibrator pair 'caseB' was measured to be larger than the inward deflection. This is because the pressure at the inner feedback ports becomes smaller than the pressure at the outer feedback ports due to the outlet port bridge connection, increasing the degree of adhesion of the main flow to the inner wall. It was analyzed that the outward deflection of the sea outlet flow increased.

3) Evaluation of the third embodiment ('caseC') of the fluid vibrator pair

12 shows the mass flow rate (kg/s) over time in the nozzle neck and outer feedback loops (LL, RR) of the fluid vibrator pair 'caseC' for three cycles . The observation period was selected at a time point showing a constant phase change and frequency after about ten cycles passed after the start of the oscillation.

In the case of the fluid vibrator pair 'caseC', by removing the inner feedback loops and connecting the inlet ports (Inports) and the outlet ports (outports), the outlet port bridge (outport bridge), the inlet port bridge ( The difference in feedback flow in the input bridge) and the outer feedback loops occurs. Due to the difference in the feedback flow rate, a difference occurs in the growth rate of the recirculation region, which causes a phase change of the main flow, and causes a phase difference. The phase difference measured in the outer feedback loops of the fluid vibrator pair 'caseC' was analyzed as 13.9% of the period.

13 shows the Mach number, pressure contour, and streamline of the fluid vibrator pair 'caseC' during one cycle. The observation time points (a)-(d) in FIG. 13 were previously shown in FIG. 12 .

According to Figure 13 (a), the pressure in the inlet port bridge (inport bridge), the outlet port bridge (outport bridge) is lower than that in the outer feedback loops (LL, RR), the main flow (L, R) ) is pressed toward the inner block, and due to the pressure imbalance, the main flow R first discharges the flow through the outlet bridge (dotted white line; pressure action to align the phase). The discharged flow presses the main flow (L) and pushes it toward the outer block, and a part of the main flow (L) flows into the inlet port (Inport) of the LL in a chain to the outlet port (outport) of the LL ) and causes delamination in the outer block of the main flow (L). Due to the separation, the recirculation region develops, and the main flow (L) is closely attached to the inlet port bridge, and the flow is discharged to the inlet port bridge to cause separation in the inner block of the main flow (R). (black dotted line. Recirculation region causing phase shift).

According to Fig. 13(b), the recirculation region due to delamination develops so that the main flow L is in close contact with the inner block and the main flow R is in close contact with the outer block (phase coincidence). (phase-in)).

According to Figure 13 (c), the main flow (L) is in close contact with the inner block (inner block) and discharges the flow to the inlet port bridge (inport bridge). The discharged flow presses the main flow (R), the main flow (R) is in close contact with the outer block (outer block), the flow is introduced into the inlet port (Inport) of the RR. Then, separation of the main flow R in the outer block is induced by the flow discharged to the outlet port of the RR.

According to FIG. 13( d ), the main flow R is in close contact with the inner block by the recirculation region grown due to the separation, and the flow is discharged to the outlet port bridge. Separation in the inner block of the main flow L is caused by the flow discharged to the outlet port bridge, and the main flow L is pushed toward the outer block (phase-in). )).

average frequency
(Hz) sweeping angle Average inward deflection
(deg) Average outward deflection
(deg) caseC 516 13 18

Fig. 14 shows sweeping angles (degrees) according to time (t ^* (s)) of the fluid vibrator pair 'caseC' during one cycle. Table 4 above shows the sweeping characteristics of the fluid vibrator pair 'caseC', and the average vibration angle and frequency with respect to the thermal cycle was derived in the same way as the fluid vibrator pair 'caseA'. The frequency of a single fluid vibrator (605±15Hz(exp)) compared with 'Lee et al.'s study', the frequency of a pair of fluid vibrators 'caseC' showed a decrease of about 14.7%. Unlike the single fluidic oscillator, in the case of the fluid oscillator pair 'caseC', a recirculation area grows between the inner block and the main flow by the flow discharged through the outlet bridge. The mass flow rate of the flow discharged through the outport bridge is small compared to the mass flow rate discharged through the feedback loop of a single fluid vibrator, so the growth rate of the recirculation region created between the inner block and the main flow is slowed down. . That is, it was analyzed that the frequency of the fluid vibrator pair 'caseC' decreased due to the decrease in the growth rate of the recirculation region due to the difference in the mass flow rate of the flow discharged to the outlet port. In the case of the fluid vibrator pair 'caseC', outward deflection was reduced by 10% compared to the fluid vibrator pair 'caseA' and the fluid vibrator pair 'caseB'. This is because the movement distance of the feedback flow is shortened due to the connection of the outlet port bridge, and the time for the feedback flow to reach the outlet port of the counterpart fluid vibrator is shorter than the response time through the existing feedback loop. It was analyzed that this is because a part of it flows into the Inport and blocks the bending process of the main flow relatively early.

4) Evaluation of the fourth embodiment ('caseD') of the fluid vibrator pair

15 shows the mass flow rate (kg/s) over time in the nozzle neck and outer feedback loops (LL, RR) of the fluid vibrator pair 'caseD' for three cycles. . The observation period was selected at a time point showing a constant phase change and frequency after about ten cycles passed after the start of the oscillation.

In the case of the fluid vibrator pair 'caseD', a chamber bridge is additionally connected to the fluid vibrator pair 'caseC', which connects an inport bridge and an outlet bridge. Compared with the pair 'caseC', the difference between the maximum and minimum values of mass flow at the nozzle neck increased by 31.6%. It was analyzed that the flow rate shared was increased due to the connection of the chamber bridge, and the fluctuation range of the mass flow rate at the nozzle neck of each fluid vibrator was also increased.

16 shows the Mach number, pressure contour, and streamline of the fluid vibrator pair 'caseD' during one cycle. The observation time points (a)-(d) in FIG. 16 were previously shown in FIG. 15 .

According to Figure 16 (a), the pressure in the three bridges is smaller than in the outer feedback loops (LL, RR), the main flow (L, R) is in close contact with the inner block (inner block), The lower part of the main flow (R) is in close contact with the inner block by the minute pressure difference, and the flow is discharged through the inlet port bridge. The discharged flow presses the main flow (L), the pushed out main flow (L) is in close contact with the outer block (outer block), the flow is introduced into the inlet port (Inport) of the LL. The flow is discharged to the outlet port of LL, causing separation from the outer block of the main flow (L), and the pushed out main flow (L) is in close contact with the inner block and the outlet port The flow is discharged to an outlet bridge and a chamber bridge. The flow discharged through the outlet port bridge causes delamination in the inner block of the main flow R.

According to Figure 16 (b), the flow discharged through the chamber bridge (chamber bridge) pressurizes the middle portion of the main flow (R) at the same time as the recirculation region following separation in the inner block (inner block) of the main flow (R) interfere with the creation of

According to Figure 16 (c), the lower portion of the main flow (L) is in close contact with the inner block (inner block) and discharges the flow to the inlet port bridge (inport bridge). The main flow (R) pressurized by the discharged flow is pushed toward the outer block and the flow is introduced into the inlet port (Inport) of the RR.

According to FIG. 16( d ), the separation in the outer block of the main flow R is induced by the flow discharged to the outlet port of the RR and a recirculation region is created. As the recirculation region develops, the main flow R is pushed toward the inner block, and a part of the main flow R is introduced into the outlet port bridge and the chamber bridge.

average frequency
(Hz) sweeping angle Average inward deflection
(deg) Average outward deflection
(deg) caseD 675 18 13

17 shows sweeping angles (degrees) according to time (t ^* (s)) of the fluid vibrator pair 'caseD' during one cycle. Table 5 above shows the sweeping characteristics of the fluid vibrator pair 'caseD', and the average vibration angle and frequency with respect to the thermal cycle was derived in the same way as the fluid vibrator pair 'caseA'. The frequency of a single fluid vibrator (605±15Hz(exp)) compared with 'Lee et al.'s study', the frequency of a pair of fluid vibrators 'caseD' showed an increase of about 11.6%. Compared with the fluid vibrator pair 'caseD', the frequency of the fluid vibrator pair 'caseD' increased by 30.8%, the inward deflection increased by 38.5%, and the outward deflection decreased by 38.5%. . In the case of the fluid vibrator pair 'caseD', due to the addition of a chamber bridge in the shape of the fluid vibrator pair 'caseC', the flow discharged to the counter fluid vibrator through the bridges increases and the relative main flow is reduced to the outer block ( The pressure pushing to the outer block) increases. As a result, it was analyzed that the forward speed of the main flow toward the outer block increased and the frequency increased, and the inward deflection was also increased. It was analyzed that the strength of the recirculation region developed in the outer block was relatively weak, so that the outward deflection was reduced.

Conclusions

In this study, under the condition of NPR3.0, the inlet and outlet ports and the recirculation chamber of two fluid vibrators with an inclined inner block were connected through a bridge, respectively. For the four fluid vibrator pairs, the vibration characteristics and flow rate characteristics according to the bridge position were analyzed through computational analysis. As a result of the analysis, the interaction of the fluid vibrator pair was distinguished according to the bridge connection positions of the inport, outlet, and recirculation chamber, respectively, and the outlet port of the other fluid vibrator through the bridge. ), it was analyzed that the growth and disappearance of the generated recirculation region caused separation and was significantly involved in matching/symmetrical phase of the fluid vibrator pair.

In the case of 'caseA', a fluid vibrator pair with an inlet port bridge connected, the feedback flow discharged through the inlet port bridge flows into each fluid vibrator through three paths, so that both main flows induced delamination from the inner block, and direct pressurization was performed on the lower portion of the relative main flow. Due to this, a phase difference occurred and was analyzed as 21.0% of the period. Due to the phase difference, there was a difference in the flow rate that each fluid vibrator shared with the other fluid vibrator through the bridge, and accordingly, the mass flow rate at the nozzle neck also changed, so that the total flow rate of the fluid vibrator L was 3.3% higher than that of the fluid vibrator R was measured. The frequency showed an increase of 5.0% compared to the single fluid vibrator, and the outward deflection of the outlet flow due to the pressure difference between the inner and outer feedback loops due to the bridge connection Outward deflection was measured to be larger than inward deflection.

In the case of 'caseB', a fluid vibrator pair connected with an outlet bridge, the feedback flow flowing into the inner feedback loops of each unit is concentrated on the outlet bridge. Thus, it simultaneously caused separation from the inner wall of the main flow of each fluid vibrator, pushing the main flow outward at the same time, acting as a mechanism to symmetrical the phase. As with the fluid vibrator pair 'caseA', there was a difference in the flow rate shared through the outlet port bridge due to the pressure imbalance, and a phase difference was observed. The fluid vibrator pair 'caseB' had a phase difference of 12.1% of the period and symmetrical outlet flow was observed, and the total flow rate at the nozzle neck of the fluid vibrator L was measured to be 1.8% higher than that of the fluid vibrator R. Compared to the single fluid vibrator, the frequency increased by 2.3%, and as in the fluid vibrator pair 'caseA', the outward deflection became larger due to the pressure imbalance due to the bridge connection, resulting in inward deflection (inward deflection). ) was observed.

In the case of the fluid vibrator pair 'caseC' that connects the inlet and outlet bridges, the flow shared through the outlet bridge is transferred from the inner block of the main flow. The phase was reversed by inducing separation, and the synchronization of the outlet flow was induced by performing direct pressurization through the inlet bridge. The difference in the total flow rate at the nozzle neck between each fluid vibrator of the fluid vibrator pair 'caseC' was less than 1%, and the phase difference was analyzed as 13.9% of the cycle. In the case of the fluid vibrator pair 'caseC', the flow discharged through the outlet bidge causes separation in the inner block and creates a recirculation region that pushes the main flow. As the mass flow discharged through the port bridge was small, the growth rate of the recirculation region was slowed, and the frequency decreased by 14.7% compared to the single fluid vibrator.

In the case of the fluid vibrator pair 'caseD', which connects the inlet port bridge, the outlet bridge, and the chamber bridge, the outlet port bridge is similar to the fluid vibrator pair 'caseC'. Separation is caused in the inner block of the main flow due to the flow discharged through the main flow They interact on the principle of pressurizing the flow. Due to the absence of the recirculation region, the frequency increased by 30.8% compared to the fluid vibrator pair 'caseC', and increased by 11.6% compared to the single vibrator. Unlike the fluid vibrator pair 'caseC', the outflow to the chamber bridge is additionally generated, and the strength of the recirculation area created in the outer block is weakened, making it the only outward dipl The outward deflection was measured to be smaller than the inward deflection. The phase difference of the fluid vibrator pair 'caseC' was the smallest among the four types and was analyzed to be 2.9% of the period.

From the above study results, the interaction of the four types of fluid vibrator pairs and the phase change and frequency change of the outlet flow were confirmed. However, since it has been observed in previous studies that the characteristics of a single fluid vibrator change according to the injection flow rate and shape factor ([19]-[22]), according to the corresponding parameters of the fluid vibrator pair observed in the present invention, Changes in characteristics are predictable. Therefore, as a follow-up study, it is judged that it is necessary to analyze the change in vibration period and phase according to the influence of shape factors such as injection mass flow rate and bridge width and length.

Although various embodiments of the present invention have been described above, the contents described so far are merely illustrative of some of the preferred embodiments of the present invention, and except as may appear in the claims appended below It is not limited by the above-mentioned content. Accordingly, the present invention understands that many changes, modifications and substitutions of equivalents can be made without departing from the spirit and spirit of the invention within the scope set forth in the claims below by those of ordinary skill in the art. will have to

Claims (5)

A fluid vibrator pair configured by connecting two or more corresponding fluid vibrators with an inlet nozzle at the upper part and an outlet nozzle at the lower part by a bridge,
A fluid vibrator pair comprising within each fluid vibrator body a sloping interior wall and a recirculation zone chamber and having a feedback loop for fluid flow from an inlet port in the lower body to an outlet port in the upper body. The method of claim 1,
As a first type of fluid vibrator pair, the inlet ports of the inner feedback loops (LR, RL) among the feedback loops of both fluid vibrators are connected by a bridge, and the flow flowing in through the inlet ports is connected to the counterpart fluid vibrator through the bridge. Fluid vibrator pair, characterized in that it is configured to be shared and interact. The method of claim 1,
As a second type of fluid vibrator pair, the outlet ports of the inner feedback loops (LR, RL) among the feedback loops of both fluid vibrators are connected by a bridge, and the flow flowing out through the outlet ports is connected to the counterpart fluid vibrator through the bridge. Fluid vibrator pair, characterized in that it is configured to be shared and interact. The method of claim 1,
As the third type of fluid vibrator pair, the inlet port and outlet port of the inner feedback loops (LR, RL) among the feedback loops of both fluid vibrators are connected by a bridge, respectively, and the flow introduced through the inlet port and the outlet port Fluid vibrator pair, characterized in that the flow flowing out through the bridge is shared with the other fluid vibrator and configured to interact. The method of claim 1,
As a fourth type of fluid vibrator pair, an inlet port, an outlet port, and a recirculation chamber chamber of the inner feedback loops (LR, RL) among the feedback loops of both fluid vibrators are connected by a bridge, respectively, each inlet port, an outlet port, and a fluid vibrator pair configured such that the flow is shared and interacts with the other fluid vibrator through a bridge connected between the recirculation chamber chambers.

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