CN114370650B

CN114370650B - Sub-millimeter self-excitation sweep jet oscillator

Info

Publication number: CN114370650B
Application number: CN202210041292.8A
Authority: CN
Inventors: 王士奇; 温泉; 刘英杰; 陈前景
Original assignee: China Aero Engine Research Institute
Current assignee: China Aero Engine Research Institute
Priority date: 2022-01-14
Filing date: 2022-01-14
Publication date: 2023-05-23
Anticipated expiration: 2042-01-14
Also published as: CN114370650A

Abstract

The invention provides a submillimeter self-excitation sweeping jet oscillator, wherein a disturbing fluid is arranged in the middle of the oscillator. The turbulent fluid is added, after the main flow enters the flow chamber from the inlet throat, the flowing instability is forced to be enhanced, the influence of the viscous boundary layer action of the fluid is relatively reduced, the coanda effect of the fluid is dominant again, the self-oscillation process is restored under the action of the baffle plate and the feedback channel in the flow chamber, and the sweeping type oscillation jet flow is formed at the outlet.

Description

Sub-millimeter self-excitation sweep jet oscillator

Technical Field

The invention belongs to an improved structure of a liquid injection device, in particular to an improved structure for liquid or gas fuel injection, and belongs to the field of energy power.

Background

In the design field of liquid spraying devices, a self-excited oscillation spraying device mainly forms a sweeping type liquid column or a fan-shaped liquid level (or liquid fog) at an outlet under the condition of stable liquid inlet through the design of a flow channel internal flow path. The core principle is that fluid is reciprocally circulated in two channels by means of the coanda effect, and finally periodic sweeping jet is formed at the outlet of the nozzle. When the liquid in the nozzle is working medium, the liquid is injected into the gas medium at a higher working frequency, and then fan-shaped liquid fog is formed at the outlet of the nozzle. The structure has the advantages of compact size, small flow loss, no movable parts, high reliability and the like.

The related patent applications CN202110519916.8 (afterburner) and CN202110747716.8 (central staged combustor) of the inventor apply the liquid injection device with the configuration to fuel injection in an aeroengine, and the high-frequency dynamic sweeping effect generated by the device is utilized to greatly improve the space dispersion uniformity of fuel in incoming flow, so that the combustion efficiency is improved, and finally, the aim of improving the working efficiency of the engine is fulfilled. However, in both afterburners and center staged combustors, the fuel injection apertures used are about 0.5mm, i.e., the throat size of the fuel injection is sub-millimeter.

In order to utilize the design theoretical basis and design experience of the existing afterburners and central staged combustors, the flow number of the novel self-excited sweep fuel injection device must be ensured to be consistent with the flow number of the original direct injection nozzle with the sub-millimeter size. Since the flow loss of the novel fuel injection device is very small, the flow coefficient is almost the same as that of the direct injection nozzle, so that the throat (the minimum sectional area of the flow channel) of the novel fuel injection device is required to be kept consistent in order to ensure that the flow coefficient of the novel fuel injection device and the flow coefficient of the direct injection nozzle are consistent, that is, the throat sectional area of the novel fuel injection nozzle is required to be kept at about 0.5mm aperture.

However, as the size of the structure of the configuration is reduced, the larger the resistance generated by the viscosity of the liquid is, the larger the ratio of the throat of the liquid boundary layer to the flow channel dimension is, and no matter how high the inlet pressure is (the highest inlet pressure is tested to be 4 MPa) when the throat width is smaller than 0.8mm when the aspect ratio of the section of the inlet throat is 1. To ensure that the throat cross-sectional area is similar to the cross-sectional area of the 0.5 aperture, if the throat width is 0.5mm, the depth is about 0.4mm, and the aspect ratio is 0.8; if the throat width is 1.25mm, the depth is about 0.16mm and the aspect ratio is only 0.128. Due to the coupling of the liquid viscosity effect and the size effect, the smaller the aspect ratio is, the more difficult the self-oscillation is realized, namely, when the throat width is larger, but the aspect ratio is only 0.128, no matter how high the inlet pressure is (the highest inlet pressure is tested to be 4 MPa), the self-oscillation cannot be generated.

In order to ensure that the throat width is less than about 0.7mm, the throat aspect ratio is less than 1.2; or the throat width is in millimeter scale (0.7 < T <2 mm), and the self-excitation sweeping oscillation of jet flow can still be realized under the condition that the throat aspect ratio is smaller than 0.25, and the structural size of an internal flow channel of the jet flow can be improved.

Disclosure of Invention

In order to solve the problem that the conventional jet oscillator structure cannot realize self-excited sweep oscillation under the conditions of sub-millimeter throat size and extremely low throat aspect ratio, the invention provides a jet oscillator flow channel structure with disturbance fluid, which can realize self-excited sweep oscillation of jet injection under the conditions of sub-millimeter throat size and extremely low throat aspect ratio. The aim of the invention is achieved by the following scheme:

the submillimeter self-excitation sweeping jet oscillator comprises an oscillation cavity, two feedback channels, nozzles and inlets, wherein the two feedback channels are arranged on two sides of the oscillation cavity and are communicated with the oscillation cavity, the nozzles and the inlets are respectively arranged at two ends of the oscillation cavity, the feedback channels comprise feedback channel inlets close to the nozzles and communicated with the oscillation cavity, and feedback channel outlets close to the inlets and communicated with the oscillation cavity, an inlet throat is formed at the joint of the inlets and the oscillation cavity, the width of the inlet throat is smaller than or equal to 0.7mm, the ratio of the height of the inlet throat to the width of the inlet throat is smaller than or equal to 1.2, or the width of the inlet throat is larger than or equal to 0.7mm and smaller than or equal to 2mm, and the width ratio of the height of the inlet throat to the inlet throat is smaller than or equal to 0.25; the middle part of the oscillation cavity is provided with a fluid disturbance which is used for increasing the instability of the fluid and can influence the thickness of the boundary layer of the side wall of the oscillation cavity.

Further, the disturbing fluid is cylindrical or polygonal.

Further, a ratio of a diameter of the cylindrical shape or a diameter of a circumscribed circle of the polygon to a width of the inlet throat is 0.5 or more and 2.5 or less.

Further, the nozzle is fan-shaped, the smaller section of the nozzle is communicated with the oscillating cavity to form an outlet throat, and the larger section of the nozzle is arranged away from the oscillating cavity.

Further, the distance from the center of the disturbing fluid to the outlet throat is greater than or equal to the width of the inlet throat.

Further, the distance from the center of the disturbing fluid to the end face of the feedback channel outlet close to the nozzle is larger than or equal to the width of the inlet throat.

Further, the ratio of the longest length of the projection of the spoiler on the flow cross section to the width of the inlet throat should be greater than or equal to 0.5 and less than or equal to 2.5.

Further, the ratio of the distance from the center of the disturbing fluid to any side wall of the oscillating cavity to the distance from the two side walls of the oscillating cavity is more than or equal to 0.2 and less than or equal to 0.8.

Further, the turbulence body is located on the symmetry axis of the oscillation cavity.

Further, there are 2 or more of the spoilers.

Further, the height of the turbulence body is consistent with the height of the inside of the oscillation cavity.

Compared with the prior art, the invention has the advantages that: the invention provides a submillimeter self-excitation sweeping jet oscillator, wherein a disturbing fluid is arranged in the middle of the oscillator. The turbulent fluid is added, after the main flow enters the flow chamber from the inlet throat, the flowing instability is forced to be enhanced, the influence of the viscous boundary layer action of the fluid is relatively reduced, the coanda effect of the fluid is dominant again, the self-oscillation process is restored under the action of the baffle plate and the feedback channel in the flow chamber, and the sweeping type oscillation jet flow is formed at the outlet.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

FIG. 1 is a self-exciting swept injection oscillator;

FIG. 2 is a schematic illustration of fluid flow of a sub-millimeter self-excited swept jet oscillator without interfering with the fluid;

FIG. 3 is a schematic illustration of fluid flow of a submillimeter self-exciting swept jet oscillator with a spoiler positioned adjacent to a jet orifice;

FIG. 4 is a schematic illustration of fluid flow of a submillimeter self-exciting swept jet oscillator when the spoiler is positioned away from the jet orifice;

FIG. 5 is a dimension view of the sub-millimeter self-excited swept jet oscillator of FIG. 4;

FIG. 6 is a schematic diagram of a spoiler biased sub-millimeter self-excited swept jet oscillator.

FIG. 7 is a schematic diagram of sub-millimeter self-excited swept jet oscillator spoiler position;

fig. 8 is a schematic diagram of a submillimeter self-excited swept jet oscillator for a dual disturbance fluid.

Wherein: 110. an inlet; 120. a feedback channel; 130. a spout; 140. a flow passage partition; 150. an oscillation cavity; 160. an outlet throat; 170. an inlet throat; 180. disturbing the fluid; 200. an adhesive layer; 300. and (5) shedding vortex.

Detailed Description

The present invention will be described in further detail with reference to the drawings and embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the substances, and not restrictive of the invention. It should be further noted that, for convenience of description, only the portions related to the present invention are shown in the drawings.

In addition, the embodiments of the present invention and the features of the embodiments may be combined with each other without collision. The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

Referring to fig. 1 of the specification, the invention provides a self-excited sweep spray oscillator, which comprises an oscillation cavity 150, two feedback channels 120 arranged at two sides of the oscillation cavity 150 and communicated with the oscillation cavity 150, a nozzle 130, an inlet 110 and a flow channel partition 140 respectively arranged at two ends of the oscillation cavity 150.

The flow channel partition 140 is disposed in the inner cavity of the oscillator, and divides the inner cavity into two parts, namely the oscillator cavity and the feedback channel 120. The feedback channel inlet is connected to the oscillation cavity 150 proximate the spout 130 and the feedback channel outlet is in communication with the oscillation cavity 150 proximate the inlet 110. The inlet 110 has a smaller cross-sectional area than the oscillation cavity 150, so that an inlet throat 170 is formed at the junction of the inlet and the oscillation cavity 150. The two flow path partitions 140 are in the shape of an "L" and are symmetrically disposed to define a larger oscillation cavity 150 space near the nozzle 130, and a fluid passage space that is equal in size to the inlet throat 170 or slightly larger than the inlet throat 170 is generally formed near the inlet. Of course, the two-flow path partitions 140 can take on other shapes. The flow path diaphragm 140 serves to define the oscillation cavity 150 with a cross section that gradually increases along the fluid flow direction as a whole. That is, it is within the scope of the claimed invention that the flow from the inlet 110 be further constricted by the flow path baffle 140 and then expanded.

The spout 130 is fan-shaped, with the smaller cross-section of the spout 130 communicating with the oscillation cavity 150 to form an outlet throat 160. While the spout 130 has a larger cross-section that is disposed away from the oscillation cavity 150, the fan angle being used to control the angle of the oscillating spray of liquid. Typically at larger sizes, the fluid passes through the inlet throat 170 at high velocity, and the primary fluid typically flows along a side wall and is ejected outwardly. The flow path formed by the oscillating cavity 150 gradually expands, resulting in a decrease in velocity and turbulence, while the feedback channel 120, due to the proximity of the inlet throat 170, creates a lower pressure for the high velocity fluid, drawing fluid from the feedback channel inlet, pushing the main fluid to deflect to the other side.

Referring to fig. 2, when the throat size width is small (about 0.5 mm), or the throat height width is small (less than 1.2 in the submillimeter scale and less than 0.2 in the millimeter scale), the viscosity effect of the liquid is too large because the thickness of the boundary layer 200 occupies the main flow channel, and under the effect of the size effect, after the main flow enters the flow cavity from the inlet throat 170, the coanda effect of the fluid fails, and the wall attachment of the main jet cannot be realized, that is, the self-excitation sweeping oscillation of the outlet jet cannot be realized by using the backflow of the fluid in the feedback channel 120. Fluid entering the oscillation cavity 150 through the inlet 110 will be ejected from the spout 130 directly through the oscillation cavity 150.

The invention mainly researches that when the width T of the inlet throat 170 is less than or equal to 0.7mm and the ratio of the height of the inlet throat 170 to the width T of the inlet throat 170 is less than or equal to 1.2, or the width T of the inlet throat 170 is less than or equal to 0.7mm and less than or equal to 2mm and the ratio of the height of the inlet throat 170 to the width T of the inlet throat 170 is less than or equal to 0.25, the oscillator is enabled to swing again by adding the disturbance fluid 180. A self-exciting swept jet oscillator having the above dimensional relationship, i.e. a sub-millimeter self-exciting swept jet oscillator as referred to herein.

Referring to fig. 3, when the distance between the disturbing fluid 180 and the nozzle 130 is smaller than a certain value, the main fluid does not damage the boundary layer 200, the main fluid does not pass through the feedback channel 120, the main fluid moves along a straight line, and the main fluid forms a falling vortex 300 with a certain frequency in the direction of the main fluid flowing in the rear direction under the action of the disturbing body 180, namely, a karman falling vortex (karman vortex street), and under the action of the falling vortex 300, the oscillator can also form an oscillating jet with a certain angle alpha, but the angle alpha is far smaller than the angle of a swept jet generated by the coanda effect with the feedback channel.

Referring to fig. 4, the turbulence body 180 of the present invention is disposed at a distance from the nozzle 130, and when the main fluid encounters the turbulence body 180, turbulence is formed in the direction of the main fluid flow away from the main fluid flow direction, and the turbulence will directly affect the boundary layer 200, so that the boundary layer 200 is reduced, and the boundary layer re-induces the coanda effect of the fluid, so that the main fluid is re-attached to the sidewall. At this time, under the effect of the coanda effect, the fluid pushes the main fluid to turn over in another direction through the feedback channel, so that the main fluid is continuously swung at the nozzle 130 to form a fan-shaped liquid film or liquid mist. This solution gives a fan-shaped liquid film or spray angle that is greater than the solution with an oscillating jet formed by karman shedding vortices behind the disturbing fluid.

The core of the invention is how to re-oscillate a small-sized oscillator and to provide a solution for breaking the thickness of the boundary layer in the oscillation cavity to obtain re-oscillation. Other schemes for reducing the boundary layer thickness to regain shimmy are readily available to those skilled in the art based on the specific embodiments of the present disclosure, including, but not limited to, changing the distance of the interfering fluid from the jet, the shape of the interfering fluid and the jet, the size of the interfering fluid, the shape of the oscillating cavity, etc. Referring to fig. 4, a scheme of blocking a main fluid with a cylindrical spoiler to generate an unstable fluid is shown. The cylindrical spoiler 180 is only an example, and it is not excluded that other forms of spoiler 180 may be used. It is within the scope of the claimed invention to have a spoiler 180 that enables the creation of an unstable fluid within the oscillating cavity of a self-swept jet oscillator at the sub-millimeter scale. For example, the present invention can also employ a polygonal spoiler 180.

According to the principle of generating turbulence in the direction of the turbulent flow 180 facing away from the flow direction, which is mentioned in the present invention, it is necessary to increase the distance of the turbulent flow 180 from the nozzle 130. Referring to fig. 5 and 7, a distance D2 from the center of the spoiler 180 to the outlet throat 160 is greater than or equal to a width T of the inlet throat 170. Specifically, when the disturbing fluid 180 is in a regular shape, for example, a cylinder shape or a polygon having a circumscribing circle, its center is a center line of the cylinder or a straight line where the center of the circumscribing circle is located. When the turbulence body 180 is irregularly shaped, the center of the turbulence body 180 is the centroid of the irregular shape, i.e., the center of gravity thereof.

Generally, it is preferable to arrange the turbulence body 180 along the central symmetry line of the fluidic oscillator, i.e. the above-mentioned center of the turbulence body 180 is located on the central symmetry line. The primary jet, after entering the oscillation cavity 150 from the inlet throat 170, can be blocked with a greater probability by the turbulent fluid flow 180, forcing the primary fluid to deflect to both sides and create turbulence behind the turbulent fluid flow 180. However, it is found that, due to the characteristics of the oscillator, the main jet flow has a deflection with a certain angle after entering the oscillating cavity 150, and the spoiler 180 has a certain width, and the center of the spoiler 180 is shifted, so that the function of re-shimmy of the submillimeter oscillator can be realized. Referring to FIG. 5, when 0.2 ID/IW is 0.8, the turbulent flow of the turbulent flow is achieved by the turbulent flow 180. Wherein ID is the distance from the center of the disturbing fluid 180 to one side wall surface, a straight line perpendicular to the symmetry axis of the oscillator is made from the center of the disturbing fluid 180 to the two side wall surfaces, and a line segment sandwiched by the two side wall surfaces is IW. That is, the ratio of the distance from the center of the turbulence body 180 to any side wall of the oscillation cavity 150 to the distance between the two side walls of the oscillation cavity 150 is greater than 0.2 and less than or equal to 0.8. When the turbulence body 180 is too close to one side wall surface, i.e., ID/IW <0.2 or ID/IW > 0.8, effective turbulence cannot be formed due to the too close distance between the turbulence body 180 and one side wall surface, and the feedback channel 120 is affected due to the rapid decrease of the liquid flowing to one side, so that shimmy cannot be generated again.

The turbulent fluid flow 180 must have a certain width to form a barrier for the main flow entering the oscillation cavity 150, so that the fluid is turbulent in a direction in which the turbulent flow 180 faces away from the incoming flow. Thus, the disturbance fluid 180 is projected along the central symmetry line of the oscillator onto a plane perpendicular to the central symmetry line. The maximum distance of the projection perpendicular to the central symmetry line is the effective blocking length of the spoiler 180 that can block the forward flow of the main fluid into the oscillating cavity 150. The ratio of this length to the width T of the inlet throat 170 should be greater than or equal to 0.5 and less than or equal to 2.5. To reduce the difficulty of manufacturing, a cylindrical shape or a polygonal shape having a circumscribing circle is generally used as the disturbing fluid 180. At this time, the ratio of the diameter of the cylinder or the diameter of the circumscribed circle of the polygon to the width T of the inlet throat 170 should be 0.5 or more and 2.5 or less.

Referring to fig. 7, the turbulators 180 should be located a distance from the end face of the flow channel baffle 140 proximate the inlet throat 170. More specifically, the two flow channel partitions 140 define the oscillating cavity 150 with an oscillating cavity 150 having a varying cross-sectional area, and the spoiler 180 should be disposed at a minimum cross-sectional distance from the oscillating cavity 150. Typically this minimum cross-section occurs at the end of the diaphragm proximate the inlet throat 170. The smallest cross-section defines the flow cross-section of the fluid entering the oscillation cavity 150 after the primary fluid has passed through the inlet throat 170. The main fluid is characterized by being ejected in a straight line before passing through the cross section, and after passing through the flow cross section, the main fluid is deflected by vortex generation or the like due to the increase of space. If the turbulence body 180 is too close to the cross section, after the main fluid hits the turbulence body 180, the bouncing fluid will affect the entering of the main fluid and may cause the fluid to flow reversely along the outlet of the feedback channel 1 towards the inlet of the feedback channel. It has been studied that the distance from the center of the disturbance fluid 180 to this cross section should be greater than or equal to the width T of the inlet throat 170.

Referring to fig. 8, in order to further increase the instability of the main flow at very small dimensions or at very low aspect ratios of the inlet throat 170, 2 or more turbulators 180 may be provided to excite the coanda effect of the flow, thereby achieving self-oscillation of the fluid. Of course, the plurality of interfering fluids 180 must meet the position size and shape size requirements described above.

Further, the height of the turbulence body 180 is consistent with the height of the interior of the oscillation cavity 150. So that the main fluid advances around both sides of the disturbing fluid 180, thereby preventing the fluid from flowing forward along a straight line from the upper portion or the bottom of the disturbing body 180, and reducing the disturbing characteristics of the disturbing column.

Reference herein to a primary fluid is to a medium having flow characteristics including, but not limited to, liquids such as water, fuel oil, gases such as air, nitrogen, flowable solid particles, and the like. The above media flows in a self-excited swept spray pattern at sub-millimeter dimensions, all in accordance with the flow characteristics described herein, and the disturbance fluid 180 of the present invention is capable of re-shimmy the self-excited swept spray pattern.

In the description of the present specification, reference to the terms "one embodiment/manner," "some embodiments/manner," "example," "specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment/manner or example is included in at least one embodiment/manner or example of the present application. In this specification, the schematic representations of the above terms are not necessarily for the same embodiment/manner or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments/modes or examples. Furthermore, the various embodiments/modes or examples described in this specification and the features of the various embodiments/modes or examples can be combined and combined by persons skilled in the art without contradiction.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "plurality" is at least two, such as two, three, etc., unless explicitly defined otherwise.

It will be appreciated by persons skilled in the art that the above embodiments are provided for clarity of illustration only and are not intended to limit the scope of the invention. Other variations or modifications will be apparent to persons skilled in the art from the foregoing disclosure, and such variations or modifications are intended to be within the scope of the present invention.

Claims

1. The utility model provides a submillimeter self-excitation sweeps jet oscillator, includes oscillation cavity, sets up respectively in oscillation cavity both sides and with two feedback channels of oscillation cavity intercommunication, set up respectively in spout and the import at oscillation cavity both ends, feedback channel including be close the spout and with the feedback channel entry of oscillation cavity intercommunication and be close the import and with the feedback channel export of oscillation cavity intercommunication, import and oscillation cavity junction form import throat, its characterized in that:

the inlet throat satisfies: t is less than or equal to 0.7mm and A/T is less than or equal to 1.2, or T is less than or equal to 0.7mm and less than or equal to 2mm and A/T is less than or equal to 0.25; wherein T is the width of the inlet throat, A is the height of the inlet throat;

the middle part of the oscillating cavity is provided with a turbulence body which is used for increasing the instability of fluid and can influence the thickness of the boundary layer of the side wall of the oscillating cavity;

the ratio of the longest length of the projection of the disturbing fluid on the flow cross section to the width of the inlet throat should be greater than or equal to 0.5 and less than or equal to 2.5.

2. A submillimeter self-exciting swept jet oscillator as claimed in claim 1, wherein: the distance from the center of the disturbing fluid to the nozzle is larger than or equal to the width of the inlet throat.

3. A submillimeter self-exciting swept jet oscillator as claimed in claim 1, wherein: the distance from the center of the disturbing fluid to the end face of the feedback channel outlet close to the nozzle is greater than or equal to the width of the inlet throat.

4. A submillimeter self-exciting swept jet oscillator as claimed in claim 1, wherein: the turbulence body satisfies 0.2-0.8 ID/IW, wherein ID is the distance from the center of the turbulence body to any side wall of the oscillation cavity, and IW is the distance between the two side walls of the oscillation cavity.

5. A sub-millimeter self-excited swept jet oscillator as claimed in claim 4, wherein: the turbulence body is positioned on the symmetry axis of the oscillation cavity.

6. A submillimeter self-exciting swept jet oscillator as claimed in any one of claims 1 to 5, wherein: the disturbing fluid is cylindrical or polygonal.

7. A submillimeter self-exciting swept jet oscillator as claimed in any one of claims 1 to 5, wherein: the nozzle is fan-shaped, the smaller section of the nozzle is communicated with the oscillating cavity to form an outlet throat, and the larger section of the nozzle is arranged away from the oscillating cavity.

8. A submillimeter self-exciting swept jet oscillator as claimed in any one of claims 1 to 5, wherein: there are 2 or more of said spoilers.

9. A submillimeter self-exciting swept jet oscillator as claimed in any one of claims 1 to 5, wherein: the height of the turbulence body is consistent with the height of the inside of the oscillation cavity.