CN112844895B

CN112844895B - Device for controlling liquid jet flow crushing

Info

Publication number: CN112844895B
Application number: CN202110000477.XA
Authority: CN
Inventors: 赵羽; 徐海涛
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2021-01-03
Filing date: 2021-01-03
Publication date: 2021-08-17
Anticipated expiration: 2041-01-03
Also published as: CN112844895A

Abstract

The invention relates to the technical field of liquid jet, in particular to a device for controlling liquid jet to break. The device integrates two sets of pulse laser focusing heating systems in the cavity, and different pulse laser focusing heating systems are mutually independent to carry out complex cooperative pulse heating on different positions along the flow direction on the liquid jet flow, and the unstable waves induced by surface tension disturbance in different forms on the liquid jet flow are cooperatively excited, so that different control effects are realized aiming at the crushing of the liquid jet flow. The pulse laser group of many sets presents the circumference distribution form of ectonexine at the cavity top, and then cooperates speculum and convex lens to realize the pulse focus heating to liquid efflux along the different positions of flow direction, and such structural design has greatly saved the space, has improved the degree of integrating to the position of pulse focus heating point on the liquid efflux of regulation pulse laser focus heating system in a flexible way provides the condition.

Description

Device for controlling liquid jet flow crushing

Technical Field

The invention relates to the technical field of liquid jet, in particular to a device for controlling liquid jet to break.

Background

The liquid jet is generally unstable and can break up into droplets. Quantitative research on the liquid jet fragmentation phenomenon dates back to the 19 th century and directly prompts Rayleigh to develop an important tool for linear stability analysis. Long-term theoretical analysis, numerical simulation and experimental observation show that: jet breakup is caused by the development of an initial disturbance wave at the jet surface. Since the initial perturbations comprise a wide range of frequencies (or wave numbers), the ultimate breakup is a result of the competition between these perturbation frequencies, unless the jet reynolds number (a dimensionless parameter used to characterize the jet strength, defined as the product of jet velocity and jet diameter divided by the fluid viscosity coefficient) is extremely small, the jet breaks up into droplets of different size and spacing. In brief, the liquid jet is broken into liquid drops with different sizes and different spacing distances, the size and the spacing distance of the liquid drops broken naturally by the liquid jet are not controllable, the broken length of the liquid jet fluctuates continuously along with time, and the whole system is in a chaotic state.

The above-mentioned natural break-up phenomena of liquid jets have various different effects on different fields. For example: in the field of wet spinning, the person skilled in the art would like the liquid jet not to break up into droplets prematurely, so that a longer jet break-up length can be maintained. Meanwhile, in the field of wet spinning, the quantitative control on the liquid jet flow crushing length is of great significance. It is additionally emphasized that in the present invention, the distance of the liquid jet from the "nozzle orifice" to the "first breaking point" is expressed by the term "liquid jet breaking length", and the time between the ejection of the liquid jet from the "nozzle orifice" and the "first breaking point" is expressed by the term "liquid jet breaking time".

On the contrary, although the fields of jet spraying and cleaning, fuel spraying, ink jet printing (and 3D printing), pharmaceutical manufacturing, cloud dynamics research and the like utilize the liquid droplets generated after the liquid jet is broken to a certain extent, these different application fields have many different requirements on the form of the liquid droplets generated after the liquid jet is broken, and further have many technical bottlenecks. Particularly, in the field of spraying and cleaning of jet flow, a most typical example is cleaning of semiconductor wafers, and research shows that impact cleaning of the semiconductor wafers by droplet strings with the same particle size and the same spacing distance is better than cleaning of droplet strings with different particle sizes and different spacing distances; in the field of fuel oil spraying, it is also very desirable that fuel oil droplets with wide particle size distribution in liquid spraying can be improved into fuel oil droplets with the same particle size, uniform intervals and precisely controllable particle size, so that the combustion efficiency of fuel oil is improved; for the field of ink-jet printing (and 3D printing), the size of ink droplets is homogenized and controlled, so that the printing (and modeling) quality can be improved to a great extent; for the field of pharmaceutical manufacturing, those skilled in the art would like to be able to precisely control the size of the drug particles produced; for the cloud dynamics research, the related researchers need a droplet group satisfying a certain particle size distribution (such as gaussian distribution, poisson distribution, etc.) as an experimental research object. The natural fragmentation phenomenon, which relies solely on liquid jets, is clearly not able to satisfy the different technical needs of the above mentioned fields.

In summary, different technical fields have different technical requirements for the liquid jet flow crushing phenomenon, and the invention of a device which can meet the different technical requirements is of great significance.

A publication with the application number 201910640820.X discloses a method and a device for controlling jet flow crushing. The publication states that the heating frequency of the pulsed laser can be determined in dependence on the target frequency of jet break-up, and then the liquid jet is broken up in accordance with the target frequency by projecting the pulsed laser onto the liquid jet. However, the embodiments, devices, principles, etc., which are not specifically disclosed in this disclosure, cannot be embodied in any way.

Disclosure of Invention

The invention aims to provide a device for controlling liquid jet flow crushing, which carries out complex cooperative pulse heating on different positions on a liquid jet flow through a plurality of sets of pulse laser groups, and cooperatively excites unstable waves induced by surface tension disturbance in different forms on the liquid jet flow, thereby realizing different control effects aiming at the crushing of the liquid jet flow.

The device for controlling the liquid jet flow to be broken comprises an outer layer pulse laser focusing and heating system and an inner layer pulse laser focusing and heating system which are arranged inside a cavity of a cavity and a measuring system which is arranged outside the cavity;

the outer layer pulse laser focusing and heating system comprises an outer layer pulse laser group, an upper layer reflector mounting rack, a first rotation controller, an upper layer reflector screw rod, an upper layer convex lens mounting rack, a second rotation controller and an upper layer convex lens screw rod; the outer layer pulse laser groups are uniformly distributed on the top of the cavity along the circumference, and the upper layer reflector is arranged in the upper layer reflector mounting frame; the upper reflector mounting frame is linked with an upper reflector screw rod, and the upper reflector screw rod penetrates through the cavity to be linked with a first rotating controller arranged on a top cover of the cavity; the upper layer convex lens is arranged on the upper layer convex lens mounting frame, the upper layer convex lens mounting frame is linked with the upper layer convex lens lead screw, and the upper layer convex lens lead screw penetrates through the cavity to be linked with a second rotation controller arranged on the top cover of the cavity; the pulse laser emitted by the outer layer pulse laser group is reflected to the upper layer convex lens through the upper layer reflector, and the focused laser is acted on the upper part of jet flow sprayed out of the caliber-adjustable liquid spraying port in the center of the top of the cavity by the upper layer convex lens; the upper-layer convex lens mounting frame provided with the upper-layer convex lens is positioned at the inner side of the upper-layer reflector mounting frame provided with the upper-layer reflector, and the upper-layer convex lens mounting frame and the upper-layer reflector mounting frame are positioned on the same horizontal plane; the first rotation controller controls the upper reflector mounting frame provided with the upper reflector to move up and down through an upper reflector screw rod, and the second rotation controller controls the upper convex lens mounting frame provided with the upper convex lens to move up and down through an upper convex lens screw rod;

the inner layer pulse laser focusing and heating system comprises an inner layer pulse laser group, a lower layer reflector mounting frame, a third rotation controller, a lower layer reflector screw rod, a lower layer convex lens mounting frame, a fourth rotation controller and a lower layer convex lens screw rod; the inner layer pulse laser groups are uniformly distributed on the top of the cavity along the circumference and on the inner ring of the outer layer pulse laser group, and the lower layer reflector is arranged in the lower layer reflector mounting frame; the lower reflector mounting frame is linked with a lower reflector screw rod, and the lower reflector screw rod penetrates through the cavity to be linked with a third rotation controller arranged on the top cover of the cavity; the lower convex lens is arranged on the lower convex lens mounting frame, the lower convex lens mounting frame is linked with the lower convex lens lead screw, and the lower convex lens lead screw penetrates through the cavity to be linked with a fourth rotation controller arranged on the top cover of the cavity; the pulse laser emitted by the inner layer pulse laser group is reflected to the lower layer convex lens through the lower layer reflector, and the focused laser is acted on the lower part of jet flow sprayed out of the caliber-adjustable liquid spraying opening in the center of the top of the cavity by the lower layer convex lens;

the measuring system is composed of a high-speed camera and an infrared camera, the high-speed camera shoots the liquid jet and the crushing condition at a high speed in real time through a high-speed camera shooting window on the cavity to obtain the diameter size of the liquid jet when the liquid jet is sprayed out, the crushing length of the liquid jet, the particle size and the distribution form of liquid drops crushed by the liquid jet and the crushing frequency of the liquid jet, and the infrared camera shoots the window through the infrared camera on the cavity to measure the temperature of the liquid jet in real time to further obtain the surface tension change of the liquid at the heated point on the liquid jet.

The device for controlling the liquid jet flow crushing, provided by the invention, has the advantages that:

the device for controlling the liquid jet flow crushing is highly integrated as a whole, two sets of pulse laser focusing heating systems are integrated in a cavity, different pulse laser focusing heating systems are independent from each other to carry out complex cooperative pulse heating on different positions along the flow direction of the liquid jet flow, unstable waves induced by surface tension disturbance in different forms on the liquid jet flow are cooperatively excited, and different control effects are further realized aiming at the crushing of the liquid jet flow. The pulse laser group of many sets presents the circumference distribution form of ectonexine at the cavity top, and then cooperates speculum and convex lens to realize the pulse focus heating to liquid efflux along the different positions of flow direction, and such structural design has greatly saved the space, has improved the degree of integrating to the position of pulse focus heating point on the liquid efflux of regulation pulse laser focus heating system in a flexible way provides the condition. In addition, each set of pulse laser focusing and heating system comprises a plurality of pulse lasers which are uniformly distributed at the top of the cavity along the circumference, and the pulse lasers are completely synchronous with each other, so that the pulse heating of the liquid jet flow which is heated by the reflectors and the convex lenses and distributed along the circumferential direction is realized, and the more sufficient pulse heating effect is ensured. In addition, the reflector and the mounting rack of each set of pulse laser focusing heating system, the convex lens and the mounting rack of each set of pulse laser focusing heating system are respectively provided with an independent rotation controller and a screw rod which are used for respectively and independently controlling the up-and-down movement of the reflector and the mounting rack of the convex lens, so that not only can a better focusing effect be ensured, but also the pulse laser emitted by each set of pulse laser focusing heating system can be accurately controlled at the pulse focusing heating position of the liquid jet, and the relative distance between the focusing heating positions of a plurality of sets of pulse laser focusing heating systems on the liquid jet can be accurately controlled. In addition, the device comprises a measuring system consisting of a high-speed camera and an infrared camera, various physical quantities involved in the operation of the device can be measured in real time, particularly, the infrared camera can obtain the surface tension change of liquid at a heated point on the liquid jet flow by measuring the temperature of the liquid jet flow in real time, and therefore quantitative analysis of complex Marangoni unstable waves under the surface tension disturbance excited by a plurality of sets of pulse laser focusing heating systems is achieved. Compared with the published file with the application number of 201910640820.X, the method has the contents of a very detailed device, implementation scheme, principle and the like, and can achieve richer control effect. The device provided by the invention has the advantages of the structural design, and can also realize various different control effects aiming at the breakage of the liquid jet, in particular, the device can carry out complex cooperative pulse heating on different positions on the liquid jet through a plurality of sets of pulse laser groups, and cooperatively excite Marangoni unstable waves induced by surface tension disturbance in different forms on the liquid jet, so that 4 types of different control effects can be selectively realized under different implementation modes as follows: delaying liquid jet flow crushing, controlling liquid jet flow crushing frequency (realizing homogenization and controllability of the particle size of liquid drops and the distance between the liquid drops after the liquid jet flow crushing), controlling the liquid jet flow crushing length (crushing time), customizing the frequency distribution of the liquid jet flow crushing, and distributing the particle size distribution and the distance between the liquid drops after the liquid jet flow crushing (being capable of meeting various distribution forms such as Gaussian distribution, Poisson distribution and the like). Therefore, with the set of devices according to the invention, it is possible to meet the various technical requirements of different fields for the breaking up of liquid jets in different embodiments of the device.

Description of the drawings:

fig. 1 is a schematic structural diagram of a device for controlling the break-up of a liquid jet according to the present invention.

Fig. 2 is a top view of the device of fig. 1.

Fig. 3 is a schematic diagram of the chamber structure of the device shown in fig. 1.

Fig. 4 is a schematic view showing the arrangement of the upper mirror and the upper convex lens in the device of fig. 1.

Fig. 5 is a schematic view of the mounting of the lower reflector and the lower convex lens in the device of fig. 1.

Fig. 6 is a schematic diagram of liquid jets of different crushing states generated by the device shown in fig. 1 under different operating conditions, wherein (a) the liquid jets without any modulation and irregular droplets crushed by the liquid jets, (b) the liquid jets with delayed crushing, (c) the liquid jets with controlled crushing frequency and crushing length and regular droplets crushed by the liquid jets, and (d) the liquid jets with customized droplet distribution generated after being crushed and droplets with customized distribution.

Fig. 7 is a control signal transmitted to the outer layer pulse laser of the apparatus of fig. 1, wherein (a) is a control signal for controlling the frequency and length of break-up (break-up time) of the liquid jet break-up, and (b) is a control signal for customizing the distribution pattern of droplets produced after break-up of the liquid jet.

In fig. 1 to 7, 1 is a cavity, 2 is an outer layer pulse laser group, 3 is an upper layer mirror, 4 is an upper layer mirror mounting bracket, 5 is a first rotation controller, 6 is an upper layer mirror lead screw, 7 is an upper layer convex lens, 8 is an upper layer convex lens mounting bracket, 9 is a second rotation controller, 10 is an upper layer convex lens lead screw, 11 is an inner layer pulse laser group, 12 is a lower layer mirror, 13 is a lower layer mirror mounting bracket, 14 is a third rotation controller, 15 is a lower layer mirror lead screw, 16 is a lower layer convex lens, 17 is a lower layer convex lens mounting bracket, 18 is a fourth rotation controller, 19 is a lower layer convex lens lead screw, 20 is a liquid inlet, 21 is an adjustable liquid jet port, 22 is a high speed camera, 23 is an infrared camera, 24 is an injection pump, 25 is a high speed camera shooting window, 26 is an infrared camera shooting window, 27 is an upper layer mirror lead screw mounting hole, 28 is an upper convex lens screw rod mounting hole, 29 is a lower reflector screw rod mounting hole, 30 is a lower convex lens screw rod mounting hole, 31 is a liquid jet stream without any modulation, 32 is a liquid drop generated after crushing by 31, 33 is a liquid jet stream delayed from crushing, 34 is a liquid jet stream controlled in crushing frequency and crushing length (crushing time), 35 is a liquid drop generated after crushing by 34, 36 is a liquid jet stream subjected to customized treatment of a liquid drop distribution form generated after crushing, and 37 is a liquid drop generated after crushing by 36.

Detailed Description

The structure of the device for controlling the liquid jet flow crushing is shown in figures 1 and 2, and the device comprises a cavity 1 which plays a role in integrally supporting the structure of the device, an outer layer pulse laser focusing heating system and an inner layer pulse laser focusing heating system which are arranged in the cavity 1, and a measuring system which is arranged outside the cavity 1;

the outer layer pulse laser focusing heating system comprises an outer layer pulse laser group 2, an upper layer reflector 3, an upper layer reflector mounting frame 4, a first rotation controller 5, an upper layer reflector screw rod 6, an upper layer convex lens 7, an upper layer convex lens mounting frame 8, a second rotation controller 9 and an upper layer convex lens screw rod 10; the outer layer pulse laser groups 2 are uniformly distributed on the top of the cavity 1 along the circumference, and in one embodiment of the invention, the outer layer pulse laser groups 2 comprise 4 sets of pulse lasers which are completely synchronous, so that a good pulse heating effect is ensured. As shown in fig. 4, the upper reflector 3 includes 4 reflecting surfaces, and the upper reflector 3 is mounted in the upper reflector mounting bracket 4; the upper reflector mounting rack 4 is linked with an upper reflector screw rod 6, and the upper reflector screw rod 6 penetrates through the cavity 1 to be linked with a first rotating controller 5 arranged on the top cover of the cavity 1; the upper layer convex lens 7 is arranged on the upper layer convex lens mounting rack 8, the upper layer convex lens mounting rack 8 is linked with the upper layer convex lens lead screw 10, and the upper layer convex lens lead screw 10 passes through the cavity 1 and is linked with a second rotating controller 9 arranged on the top cover of the cavity 1; the pulse laser emitted by the outer layer pulse laser group 2 is reflected to the upper layer convex lens 7 through the upper layer reflector 3, and the focused laser is acted on the upper part of jet flow sprayed out of the caliber-adjustable liquid spraying opening 21 in the center of the top of the cavity 1 by the upper layer convex lens 7;

the inner layer pulse laser focusing and heating system comprises an inner layer pulse laser group 11, a lower layer reflector 12, a lower layer reflector mounting frame 13, a third rotation controller 14, a lower layer reflector screw rod 15, a lower layer convex lens 16, a lower layer convex lens mounting frame 17, a fourth rotation controller 18 and a lower layer convex lens screw rod 19; the inner layer pulse laser groups 11 are uniformly distributed on the top of the cavity 1 along the circumference and are arranged on the inner ring of the outer layer pulse laser group 2, and in one embodiment of the invention, the inner layer pulse laser groups 11 comprise 4 sets of pulse lasers which are completely synchronous, so that a good pulse heating effect is ensured. As shown in fig. 5, the lower reflector 12 includes 4 reflecting surfaces, and the lower reflector 12 is mounted in the lower reflector mounting bracket 13; the lower reflector mounting frame 13 is linked with a lower reflector screw rod 15, and the lower reflector screw rod 15 penetrates through the cavity 1 to be linked with a third rotating controller 14 arranged on the top cover of the cavity 1; the lower convex lens 16 is arranged on a lower convex lens mounting rack 17, the lower convex lens mounting rack 17 is linked with a lower convex lens screw rod 19, and the lower convex lens screw rod 19 passes through the cavity 1 and is linked with a fourth rotation controller 18 arranged on the top cover of the cavity 1; the pulse laser emitted by the inner layer pulse laser group 11 is reflected to the lower layer convex lens 16 through the lower layer reflector 12, and the focused laser is acted on the lower part of jet flow sprayed out from the caliber-adjustable liquid spraying opening 21 in the center of the top of the cavity 1 by the lower layer convex lens 16;

the measuring system consists of a high-speed camera 22 and an infrared camera 23, the high-speed camera 22 shoots the liquid jet and the crushing condition at a high speed in real time through a high-speed camera shooting window 25 on the cavity 1 to obtain the diameter size of the liquid jet when being sprayed out, the crushing length of the liquid jet, the particle size and the distribution form of liquid drops crushed by the liquid jet and the crushing frequency of the liquid jet, wherein the crushing frequency of the liquid jet can be obtained by carrying out Fast Fourier Transform (FFT) spectrum analysis on a video shot by the high-speed camera 22; the infrared camera 23 measures the temperature of the liquid jet in real time through the infrared camera shooting window 26 on the cavity 1, and further obtains the surface tension change of the heated point liquid on the liquid jet. In one embodiment of the present invention, the surface tension change of the liquid at the heated point is obtained using the handbook of chemistry of Lane. Furthermore, it is emphasized that the heated spot on the liquid jet comprises two different heating positions of the outer pulsed laser focusing system and the inner pulsed laser focusing system.

The working principle and the working process of the device for controlling the liquid jet flow breaking are described in detail in the following with the accompanying drawings:

the device for controlling the liquid jet flow to be broken can carry out complex cooperative pulse heating on different positions on the liquid jet flow through a plurality of sets of pulse laser groups, and cooperatively excite different forms of unstable waves induced by surface tension disturbance on the liquid jet flow, thereby realizing different control effects aiming at the breaking of the liquid jet flow.

the outer layer pulse laser focusing heating system comprises an outer layer pulse laser group 2, an upper layer reflector 3, an upper layer reflector mounting frame 4, a first rotation controller 5, an upper layer reflector screw rod 6, an upper layer convex lens 7, an upper layer convex lens mounting frame 8, a second rotation controller 9 and an upper layer convex lens screw rod 10; the outer layer pulse laser groups 2 are uniformly distributed on the top of the cavity 1 along the circumference, and in one embodiment of the invention, the outer layer pulse laser groups 2 comprise 4 sets of pulse lasers which are completely synchronous, so that a good pulse heating effect is ensured. As shown in fig. 4, the upper reflector 3 includes 4 reflecting surfaces, and the upper reflector 3 is mounted in the upper reflector mounting bracket 4; the upper reflector mounting rack 4 is linked with an upper reflector screw 6, the upper reflector screw 6 penetrates through the cavity 1 to be linked with a first rotating controller 5 arranged on the top cover of the cavity 1, and the upper reflector screw 6 penetrates through an upper reflector screw mounting hole 27; the upper layer convex lens 7 is arranged on the upper layer convex lens mounting frame 8, the upper layer convex lens mounting frame 8 is linked with the upper layer convex lens screw rod 10, the upper layer convex lens screw rod 10 passes through the cavity 1 to be linked with the second rotating controller 9 arranged on the top cover of the cavity 1, and the upper layer convex lens screw rod 10 passes through the upper layer convex lens screw rod mounting hole 28; the pulse laser emitted by the outer layer pulse laser group 2 is reflected to the upper layer convex lens 7 through the upper layer reflector 3, and the focused laser is acted on the upper part of jet flow sprayed out of the caliber-adjustable liquid spraying opening 21 in the center of the top of the cavity 1 by the upper layer convex lens 7; the liquid jet is pumped into the liquid inlet 20 by an injection pump 24 and then is ejected from the caliber-adjustable liquid ejecting port 21, and the flow rate of the liquid jet is controlled by the injection pump 24.

As shown in fig. 4, the upper convex lens mounting frame 8 on which the upper convex lens 7 is mounted is located inside the upper mirror mounting frame 4 on which the upper mirror 3 is mounted, and both are located on the same horizontal plane; the upper reflector mounting frame 4 provided with the upper reflector 3 can move up and down by matching with the first rotating controller 5 and the upper reflector screw rod 6; the upper-layer convex lens mounting frame 8 provided with the upper-layer convex lens 7 can move up and down by matching with the second rotation controller 9 and the upper-layer convex lens screw rod 10, so that the positions of the upper-layer reflector 3 and the upper-layer convex lens 7 can be accurately controlled; so that the upper focused heating position of the pulsed laser light emitted from the outer layer pulsed laser group 2 on the liquid jet can be precisely controlled by the first rotation controller 5 and the second rotation controller 9.

The inner layer pulse laser focusing and heating system comprises an inner layer pulse laser group 11, a lower layer reflector 12, a lower layer reflector mounting frame 13, a third rotation controller 14, a lower layer reflector screw rod 15, a lower layer convex lens 16, a lower layer convex lens mounting frame 17, a fourth rotation controller 18 and a lower layer convex lens screw rod 19; the inner layer pulse laser groups 11 are uniformly distributed on the top of the cavity 1 along the circumference and are arranged on the inner ring of the outer layer pulse laser group 2, and in one embodiment of the invention, the inner layer pulse laser groups 11 comprise 4 sets of pulse lasers which are completely synchronous, so that a good pulse heating effect is ensured. As shown in fig. 5, the lower reflector 12 includes 4 reflecting surfaces, and the lower reflector 12 is mounted in the lower reflector mounting bracket 13; the lower reflector mounting frame 13 is linked with a lower reflector screw rod 15, the lower reflector screw rod 15 penetrates through the cavity 1 to be linked with a third rotation controller 14 arranged on the top cover of the cavity 1, and the lower reflector screw rod 15 penetrates through a lower reflector screw rod mounting hole 29; the lower convex lens 16 is arranged on a lower convex lens mounting frame 17, the lower convex lens mounting frame 17 is linked with a lower convex lens screw rod 19, the lower convex lens screw rod 19 passes through the cavity 1 to be linked with a fourth rotation controller 18 arranged on the top cover of the cavity 1, and the lower convex lens screw rod 19 passes through a lower convex lens screw rod mounting hole 30; the pulse laser emitted by the inner layer pulse laser group 11 is reflected to the lower layer convex lens 16 through the lower layer reflector 12, and the focused laser is acted on the lower part of jet flow sprayed out from the caliber-adjustable liquid spraying opening 21 in the center of the top of the cavity 1 by the lower layer convex lens 16; the liquid jet is pumped into the liquid inlet 20 by an injection pump 24 and then is ejected from the caliber-adjustable liquid ejecting port 21, and the flow rate of the liquid jet is controlled by the injection pump 24.

As shown in fig. 5, the lower convex lens mount 17 to which the lower convex lens 16 is mounted is located at the inner side of the lower mirror mount 13 to which the lower mirror 12 is mounted, and both are located at the same horizontal plane; the lower reflector screw rod 15 can enable the lower reflector mounting frame 13 provided with the lower reflector 12 to move up and down by matching with the third rotation controller 14; in cooperation with the fourth rotation controller 18, the lower convex lens lead screw 19 can enable the lower convex lens mounting rack 17 provided with the lower convex lens 16 to move up and down, so that the positions of the lower reflector 12 and the lower convex lens 16 can be accurately controlled; thus, the lower focused heating position of the pulsed laser light emitted from the inner layer pulsed laser group 11 on the liquid jet can be precisely controlled by the third rotation controller 14 and the fourth rotation controller 18.

Therefore, the relative distance between the upper pulse focusing heating position and the lower pulse focusing heating position of the outer layer pulse laser focusing heating system and the inner layer pulse laser focusing heating system in the liquid jet flow direction can be accurately controlled.

The measuring system is composed of a high-speed camera 22 and an infrared camera 23, as shown in fig. 2 and 3, the high-speed camera 22 performs real-time high-speed shooting on the liquid jet and the crushing condition through a high-speed camera shooting window 25 on the cavity 1 to obtain the diameter size of the liquid jet when the liquid jet is sprayed out, the crushing length of the liquid jet, the particle size and the distribution form of liquid drops crushed by the liquid jet and the crushing frequency of the liquid jet, wherein the crushing frequency of the liquid jet can be obtained by performing Fast Fourier Transform (FFT) spectrum analysis on a video shot by the high-speed camera 22; the infrared camera 23 measures the temperature of the liquid jet in real time through the infrared camera shooting window 26 on the cavity 1, and further obtains the surface tension change of the heated point liquid on the liquid jet. In one embodiment of the present invention, the surface tension change of the liquid at the heated point is obtained using the handbook of chemistry of Lane. In addition, it is emphasized that the heated point on the liquid jet comprises an upper heating position and a lower heating position of an outer layer pulse laser focusing system and an inner layer pulse laser focusing system, and the distance between the upper heating position and the lower heating position and parameters such as respective heating frequency (distribution), duty ratio, power and the like can be accurately controlled.

From the principle of fluid mechanics, when the temperature of the liquid is increased, the surface tension of the liquid is correspondingly reduced; when the temperature of the liquid is lowered, the surface tension of the liquid is correspondingly increased. According to the invention, the moving liquid jet is heated by pulse laser to generate interval type high-low distribution of temperature on the moving liquid jet, and further generate interval type high-low distribution of surface tension on the moving liquid jet, so that Marangoni flow on the liquid jet is induced.

Specifically, the Marangoni flow means that while the liquid jet moves in its entirety, the fluid in the low surface tension region of the liquid jet flows to the high surface tension region of the liquid jet, causing the high surface tension region to expand and the low surface tension region to contract accordingly. In accordance with the invention, it is then the location where the liquid jet is heated that contracts over time and the location where it is not heated that correspondingly expands over time. This surface tension varying unstable wave induced by the present invention is referred to herein as a Marangoni unstable wave.

The device for controlling liquid jet flow crushing, provided by the invention, carries out complex cooperative pulse focusing heating on the upper position and the lower position of the liquid jet flow along the flow direction through the two sets of pulse laser groups, and is used for cooperatively exciting Marangoni unstable waves induced by surface tension disturbance in different forms on the liquid jet flow so as to realize various different control effects aiming at the liquid jet flow crushing.

It should be emphasized that, in the implementation of the device of the present invention, gravity is not utilized, and the spraying direction of the liquid jet is not limited to vertical downward, and may be directed to any direction in space, and the words "upper", "lower", "top-down" and the like are used herein only for convenience of description with reference to the drawings, and "upper" and "lower" herein do not represent a fixed direction such as the gravity direction. This is essentially different from some techniques which rely on gravity to break a jet of high viscosity liquid by changing the viscosity.

In summary, with the device for controlling the liquid jet break-up proposed by the present invention, the following four different control effects can be selectively achieved in different embodiments: firstly, delaying the liquid jet flow from breaking; secondly, the liquid jet flow crushing frequency is controlled (the size of the particle size of the liquid drops and the distance between the liquid drops generated after the liquid jet flow crushing are uniform and controllable); thirdly, controlling the crushing length (crushing time) of the liquid jet; fourthly, the frequency distribution of the liquid jet flow crushing and the particle size distribution and the spacing distance distribution of the liquid drops generated after the liquid jet flow crushing are customized (the distribution forms such as Gaussian distribution, Poisson distribution and the like can be met).

As shown in fig. 6, the liquid jet flow generated by the proposed device under different operating conditions is schematically represented by (a) liquid jet flow 31 without any modulation and its broken irregular droplets 32, (b) liquid jet flow 33 with delayed breakage, (c) liquid jet flow 34 with controlled breakage frequency and breakage length and its broken regular droplets 35, and (d) liquid jet flow 36 with customized distribution of droplets generated after being broken and its broken droplets 37 satisfying the customized distribution.

The following will describe in detail the implementation and principle of the proposed device to achieve the above mentioned various control effects:

firstly, delaying liquid jet flow crushing:

the liquid jet is broken into liquid drops with different sizes and different spacing distances, which is a natural phenomenon, the size and the spacing distance of the liquid drops broken naturally by the liquid jet are not controllable, the broken length of the liquid jet fluctuates continuously along with time, and the whole system is in a chaotic state, as shown in (a) in fig. 6. This natural fragmentation phenomenon that must occur is known as Rayleigh-Plateau instability. However, this natural fragmentation phenomenon is undesirable in the field of wet spinning and the like, since it would mean premature breakage of the dope filament. The ability to delay the break-up of the liquid jet in some way is a technical need in the relevant field of wet spinning and the like.

The outer layer pulse laser focusing heating system and the inner layer pulse laser focusing heating system of the device provided by the invention are used for carrying out pulse focusing heating on the upper position and the lower position of the liquid jet flow in the upper flow direction and the lower position, and the two sets of pulse laser focusing heating systems are both in a single frequency state, so that the purpose of delaying the liquid jet flow from being broken can be realized under certain parameter setting.

Specifically, in order to achieve the technical effect of delaying the liquid jet flow from being broken, the outer layer pulse laser focusing heating system and the inner layer pulse laser focusing heating system need to have the same pulse frequency, the same pulse duty ratio, and sufficiently high and close pulse laser power, and besides, any one of the following two conditions needs to be satisfied between the focusing heating point of the outer layer pulse laser focusing heating system on the liquid jet flow and the focusing heating point of the inner layer pulse laser focusing heating system on the liquid jet flow:

condition 1:

and

condition 2:

and

wherein the content of the first and second substances,

and

the pulse phases, y, of the outer layer pulse laser group 2 and the inner layer pulse laser group 11, respectively₁And y₂The space positions of the focusing heating points of the outer layer pulse laser focusing heating system and the space positions of the focusing heating points of the inner layer pulse laser focusing heating system are respectively set, v is the jet speed of the liquid jet flow, and f is the pulse frequency f of the outer layer pulse laser focusing heating system₁Pulse frequency f of inner layer pulse laser focusing heating system₂Is given (since in said state the pulse frequency of both is the same, i.e. f₁＝f₂F), the values of i, j, m and n are natural numbers.

On the premise that the pulse frequency is the same, the pulse duty ratio is the same and the pulse laser power is high enough and close between the outer layer pulse laser focusing heating system and the inner layer pulse laser focusing heating system, any one of the two conditions is met, and the control effect of delaying the liquid jet flow crushing can be achieved through the device. It should be emphasized that, in the above condition, the pulse laser powers of the two pulse laser heating systems only need to be close and not strictly equal, and the specific magnitude relationship between the two powers can be mutually fine-tuned according to the desired jet flow breaking delaying effect and the current jet flow breaking delaying effect. In addition, i or m in the parameters can be any numerical value in the natural number, and the final jet flow crushing delaying effect cannot be influenced; in the parameters, j or n can appropriately take a larger numerical value on the premise of meeting the value range of the natural number according to the current jet flow crushing delay effect so as to increase the jet flow crushing delay effect.

As shown in fig. 4, the upper convex lens mounting frame 8 on which the upper convex lens 7 is mounted is located inside the upper mirror mounting frame 4 on which the upper mirror 3 is mounted, and both are located on the same horizontal plane; the upper reflector mounting rack provided with the upper reflector 3 can be matched with the first rotation controller 5 and the upper reflector screw rod 64, moving up and down; the upper-layer convex lens mounting frame 8 provided with the upper-layer convex lens 7 can move up and down by matching with the second rotation controller 9 and the upper-layer convex lens screw rod 10, so that the positions of the upper-layer reflector 3 and the upper-layer convex lens 7 can be accurately controlled; so that the upper focusing heating position y of the pulse laser emitted from the outer layer pulse laser group 2 on the liquid jet can be accurately controlled by the first rotation controller 5 and the second rotation controller 9₁。

As shown in fig. 5, the lower convex lens mount 17 to which the lower convex lens 16 is mounted is located at the inner side of the lower mirror mount 13 to which the lower mirror 12 is mounted, and both are located at the same horizontal plane; the lower reflector screw rod 15 can enable the lower reflector mounting frame 13 provided with the lower reflector 12 to move up and down by matching with the third rotation controller 14; in cooperation with the fourth rotation controller 18, the lower convex lens lead screw 19 can enable the lower convex lens mounting rack 17 provided with the lower convex lens 16 to move up and down, so that the positions of the lower reflector 12 and the lower convex lens 16 can be accurately controlled; so that the lower focused heating position y of the pulse laser emitted from the inner layer pulse laser group 11 on the liquid jet can be precisely controlled by the third rotation controller 14 and the fourth rotation controller 18₂。

Therefore, through the device, on the premise that the pulse frequency between the outer layer pulse laser focusing heating system and the inner layer pulse laser focusing heating system is the same, the pulse duty ratio is the same, and the pulse laser power is high enough and close, the relative distance y between the focusing heating point of the outer layer pulse laser focusing heating system on the liquid jet flow and the focusing heating point of the inner layer pulse laser focusing heating system on the liquid jet flow is ensured₂-y₁And the pulse phase difference between the two

Can be adjusted to satisfy the above conditions, thereby achieving the control effect of delaying the liquid jet breakup, resulting in the liquid jet 33 being delayed in breakup, as shown in (b) of fig. 6.

Having described an embodiment for delaying break up of a liquid jet as described above by means of the device, the principle of this embodiment will now be described. The liquid jet flow is broken into liquid drops with different particle sizes and different spacing distances, the particle sizes and the spacing distances of the liquid drops broken naturally by the liquid jet flow are not controllable, the broken length of the liquid jet flow fluctuates continuously along with time, and the whole system is in a chaotic state. This natural break-up that necessarily occurs is called Rayleigh-Plateau instability and the corresponding unstable wave that causes the natural break-up of the jet is called Rayleigh-Plateau unstable wave. This Rayleigh-Plateau unstable wave does not exist at a single frequency in the actual liquid jet, but is broad-spectrum, so that the liquid jet in nature is broken into droplets having different sizes and pitches without any modulation, and the droplet size and the pitch exhibit an uncontrollable disorder as shown in (a) of fig. 6.

The device provided by the invention carries out pulse focusing heating on the upper part of the liquid jet flow through the outer layer pulse laser focusing heating system, and aims to change the surface tension on the moving liquid jet flow by changing the temperature on the moving liquid jet flow so as to generate interval type height distribution of the surface tension on the moving liquid jet flow, thereby inducing Marangoni flow on the liquid jet flow and correspondingly generating Marangoni unstable waves. This Marangoni flow means that while the liquid jet moves as a whole, fluid in low surface tension regions of the liquid jet flows towards high surface tension regions of the liquid jet, causing the high surface tension regions to expand and the low surface tension regions to contract accordingly. In accordance with the invention, it is then the location where the liquid jet is heated that contracts over time and the location where it is not heated that correspondingly expands over time. When the pulse laser power of the outer layer pulse laser focusing heating system is high enough, the development of Marangoni unstable waves caused by the pulse laser heating can completely suppress the development of Rayleigh-Plateau unstable waves, so that the natural fragmentation phenomenon cannot be shown.

Meanwhile, the device provided by the invention carries out pulse focusing heating on the lower part of the liquid jet flow through the inner layer pulse laser focusing heating system, and induces another group of Marangoni unstable waves to counteract the development of the Marangoni unstable waves induced by the outer layer pulse laser focusing heating system in turn, so that the liquid jet flow is prevented from being broken according to the induction of the outer layer pulse laser focusing heating, and the technical effect of delaying the breaking of the liquid jet flow is realized. In other words, the outer layer pulse laser focusing heating makes the natural fragmentation on the liquid jet flow unable to be shown, and simultaneously makes some positions on the liquid jet flow gradually expand (or contract) according to the induction of the outer layer pulse laser focusing heating, so the inner layer pulse laser focusing heating makes the positions of the expansion (or contraction) gradually contract (or expand) again, thereby the excitation of the outer layer pulse laser focusing heating is offset, and the control effect of delaying the liquid jet flow fragmentation is realized.

In order for the outer layer pulsed laser focusing heating system to successfully suppress the natural fragmentation phenomenon, the pulsed laser power of the outer layer pulsed laser focusing heating system needs to be sufficiently high.

In order to enable the inner layer pulse laser focusing heating system to successfully cancel Marangoni unstable waves induced by the outer layer pulse laser focusing heating system, the invention discloses a process condition that the phase difference between the two pulse laser reverse phases or the phase difference between the two pulse laser focusing heating positions is odd times of the half wavelength of pulse heating. Meanwhile, the two sets of pulse laser heating systems are required to have the same pulse frequency, the same pulse duty ratio and sufficiently high and similar pulse laser power. Thereby, a control effect of delaying the liquid jet break-up by the device can be achieved.

In brief, delaying the liquid jet break-up in fact follows the following process: the outer layer pulse laser focusing heating system is used for inhibiting the natural breaking phenomenon of liquid jet flow, and then the inner layer pulse laser focusing heating system is used for counteracting the development of Marangoni unstable waves caused by the outer layer pulse laser focusing heating system. Therefore, the liquid jet which is naturally broken after being sprayed out can move according to the excitation of the outer layer pulse laser heating, so that the natural breaking is avoided; and then the heating of the inner layer pulse laser counteracts the heating of the outer layer pulse laser, thereby avoiding the heating of the outer layer pulse laser to excite the outer layer pulse laser to be broken, further greatly delaying the breaking of the liquid jet and obtaining the longer breaking length of the liquid jet.

Although in the described embodiment of the device, the pulsed laser focusing heating system with inner and outer layers is provided to cooperatively heat two different locations on the liquid jet, thereby achieving the control effect of delaying the break-up of the liquid jet. However, if the device proposed by the present invention is to be used, the breaking up of the liquid jet is retarded to a greater extent, and in addition to appropriately raising the value of j or n as described above, there are also the following extensions.

Description of the expanded example: namely, a plurality of sets of pulse laser focusing and heating systems are added on the outer layer, so that 2p +2 pulse laser focusing and heating points are arranged on the liquid jet from top to bottom, and the process condition of delaying the liquid jet from being broken is met between the pulse laser focusing and heating systems corresponding to the 2q-1 and 2q pulse laser focusing and heating points from top to bottom. Wherein, the value of p is a certain positive integer, and q is all positive integers from 1 to p + 1.

In short, the natural breaking phenomenon of the liquid jet is firstly inhibited by the excitation of the 2q-1 pulse laser focusing heating system. It should be emphasized that the suppressed natural fragmentation phenomenon represents the natural fragmentation effect when q is equal to 1, which is carried by the liquid jet just after being ejected from the aperture-adjustable liquid ejection opening 21, and represents the natural fragmentation effect which is slowly generated after the liquid jet has undergone the 1 st to 2q-2 th pulse laser focusing heating points from top to bottom and the fragmentation delay processing thereof when q is equal to 1.

And then the 2q pulse laser focusing heating system cancels the excitation of the 2q-1 pulse laser focusing heating system, thereby continuing to delay the liquid jet flow crushing and obtaining a longer liquid jet flow crushing length. If the two pulse laser focusing heating systems in one group are added infinitely and the technological condition of delaying the liquid jet flow to be broken disclosed by the invention is met between the two pulse laser focusing heating systems, the liquid jet flow can be never broken theoretically, and further infinite liquid jet flow is obtained.

Secondly, controlling the liquid jet flow crushing frequency (realizing the homogenization and controllability of the particle size of the liquid drops and the distance between the liquid drops after the liquid jet flow is crushed):

compared with the fields such as wet spinning, the fields such as jet spraying and cleaning, fuel oil spraying, ink jet printing (and 3D printing), medicine manufacturing and the like utilize the crushing of liquid jet to a certain extent, but because the natural crushing phenomenon of the liquid jet refers to that the liquid jet can be crushed into liquid drops with different particle sizes and different spacing distances, the particle sizes and the spacing distances of the liquid drops generated after the crushing are uncontrollable, and the whole body is in a disordered state, the irregular natural crushing phenomenon can actually cause a plurality of adverse factors on operation for the fields. Therefore, controlling the breaking frequency of the liquid jet (to make the size of the droplet size and the distance between droplets uniform and controllable after the jet breaks) in some way is a technical requirement in the related fields of jet spraying and cleaning, fuel oil spraying, ink jet printing (and 3D printing), pharmaceutical manufacturing, and the like.

The device provided by the invention can delay the liquid jet flow crushing, and can control the crushing frequency of the liquid jet flow under certain parameter settings, namely, the particle size of liquid drops and the distance between the liquid drops generated after the liquid jet flow is crushed are homogenized and controllable.

Specifically, to achieve this control effect, the inner pulsed laser focused heating system of the device is turned off, leaving only the outer pulsed laser focused heating system in operation, and the outer pulsed laser focused heating system is in a single frequency state for pulsed heating of the upper portion of the liquid jet at the single frequency.

When the pulse laser power of the outer layer pulse laser focusing heating system is high enough, and the outer layer pulse laser focusing heating system inhibits the natural breaking phenomenon of the liquid jet, the development of Marangoni unstable waves excited by the outer layer pulse laser focusing heating system can not be counteracted by the pulse focusing heating of the inner layer pulse laser focusing heating system, the unstable wave development of the surface tension change of the liquid jet excited by the outer layer pulse laser focusing heating system can completely guide the breaking phenomenon of the liquid jet 34, and further the liquid jet is broken into liquid drops 35 with uniform and controllable particle size and spacing distance, as shown in (c) in fig. 6.

In principle, the pulsed heating of the liquid jet by the outer layer pulsed laser focused heating system essentially changes the surface tension on the liquid jet, so that a spaced-apart high-low distribution of surface tension is generated on the moving liquid jet, thereby inducing Marangoni flow on the liquid jet, and correspondingly generating Marangoni unsteady waves. This Marangoni flow means that while the liquid jet moves as a whole, fluid in low surface tension regions of the liquid jet flows towards high surface tension regions of the liquid jet, causing the high surface tension regions to expand and the low surface tension regions to contract accordingly. In accordance with the invention, it is then the location where the liquid jet is heated that contracts over time and the location where it is not heated that correspondingly expands over time. When the Marangoni unstable wave excited by the outer layer pulse laser focusing heating system can completely inhibit the natural breaking phenomenon of the liquid jet and cannot be cancelled by the pulse focusing heating of the inner layer pulse laser focusing heating system, the Marangoni unstable wave excited by the outer layer pulse laser focusing heating system can completely dominate the breaking phenomenon of the liquid jet, the liquid jet can be broken strictly according to the pulse frequency of the outer layer pulse laser focusing heating system, so that the breaking frequency of the liquid jet 34 is strictly equal to the pulse frequency of the outer layer pulse laser group 2 (namely, frequency locking control is realized), and the liquid jet 34 can be broken into liquid drops 35 with uniform and controllable particle size and spacing distance.

At this time, the breaking frequency of the liquid jet 34 is completely equal to the pulse frequency of the outer layer pulse laser group 2, and after the liquid jet 34 is broken strictly according to the pulse frequency of the outer layer pulse laser group 2 at this time, a string of droplets 35 with equal size and equal distance is generated, and the size of the droplets 35 in the droplet string and the distance between the droplets 35 can be strictly controlled. The control effect described above can be described by the following formula:

wherein f is_bIs the breaking frequency, f, of the liquid jet 34₁The pulse frequency of the outer layer pulse laser group 2 is s is a droplet spacing distance of droplets 35 generated after the liquid jet stream 34 is broken, v is an ejection speed of the liquid jet stream 34, d is a particle size (diameter) of the droplets 35 generated after the liquid jet stream 34 is broken, and Q is a flow rate of the liquid jet stream. From the above formula, it can be seen that, with the above-described device, in the above-described embodiment, the liquid jet 34 can be made to follow the pulse frequency f of the outer layer pulse laser group 2₁The crushing takes place and into a series of droplets 35 of equal size d in diameter and at equal spacing s, the size d in diameter of the droplets 35 in the series and the spacing s between them being both tightly controlled and satisfying the above formula.

Real-time break-up frequency f of the liquid jet_bWhich can be obtained by Fast Fourier Transform (FFT) spectroscopy of the video captured by the high speed camera 22, the flow rate Q of the liquid jet being controlled by the syringe pump 24, the size d of the diameter of the droplets 35 in the string and their separation distance s from each other being measured by the high speed camera 22.

It is emphasized that the above-described control effect of "controlling the break-up frequency of the liquid jet" cannot be achieved at any frequency, and there exists a corresponding "achievable frequency range". In other words, the breaking frequency f of the liquid jet 34_bNeeds to be within a certain frequency range to be equal to the outer layer pulse laserPulse frequency f of group 2₁In the frequency range, the uniform and controllable size and spacing of the droplets generated after jet break-up can be realized as described in the above formula. Once outside this frequency range, the Marangoni instability wave excited by the outer layer pulsed laser focused heating system is no longer able to suppress the natural fragmentation phenomenon of the liquid jet, which in turn, like the natural fragmentation phenomenon, no longer has a strict single fragmentation frequency and will fragment into droplets whose size and spacing are both irregular and uncontrollable. The present invention will be described below with respect to the frequency range.

The frequency range is as follows, that is, the frequency range simultaneously satisfies the following three conditions:

wherein σ₀For the initial surface tension of the liquid jet, Δ σ is the amplitude of the change in surface tension at the heated point of the liquid jet caused by the pulse-focused heating by the outer-layer pulse laser-focused heating system, r₀Is the jet radius of the liquid jet just after being sprayed out from the caliber-adjustable liquid spraying opening 21, v is the spraying speed of the liquid jet, f₁Is the pulse frequency, k, of the outer pulse laser group 2₁The wave number of Marangoni unstable wave excited by the outer layer pulse laser group 2 satisfies k₁＝2πf₁/v₀The subscript 1 here indicates the outer layer pulse laser group 2, δ is the dimensionless initial small perturbation on the liquid jet surface, a is a dimensionless mathematical expression and can be expressed as

ln (·) is a natural logarithm operator.

Wherein σ₀Delta sigma can be obtained by matching the infrared camera 23 with a physical property parameter table, and in one embodiment of the invention, the formula is blueHandbook of chemistry.

The jet velocity v of the liquid jet can be calculated by the following formula:

where Q is the flow rate of the liquid jet and can be controlled by a syringe pump 24, r₀Is the jet radius of the liquid jet just after the liquid jet is ejected from the adjustable-caliber liquid ejecting opening 21 and can be measured by a high-speed camera 22, and r₀Can be controlled by the caliber-adjustable liquid spraying port 21. Furthermore, the ejection velocity v of the liquid jet can also be measured by means of Particle Image Velocimetry (PIV) by adding particles to the liquid in the liquid jet.

The dimensionless initial small perturbation δ on the liquid jet surface can be calculated by the following formula:

wherein r is₀The radius of the liquid jet just after being ejected from the caliber-adjustable liquid ejecting opening 21 and can be measured by the high-speed camera 22, and epsilon is the initial small perturbation with dimension of the natural breaking effect on the surface of the liquid jet and can be calculated by the following formula:

so, the dimensionless initial small perturbation δ of the natural break-up effect on the liquid jet surface can be calculated by the following formula:

wherein l_nIn order not to inject said liquid into said deviceThe subscript n indicates the natural breaking phenomenon of the liquid jet as shown in fig. 6 (a). Further, v is the ejection velocity of the liquid jet, σ₀Is the initial surface tension of the liquid jet, r₀The radius of the liquid jet just after being sprayed out from the caliber-adjustable liquid spraying opening 21 is defined as ρ, which is the liquid density of the liquid jet, and exp (·) is an exponential function operator with a natural constant e as a base.

Since the natural break-up phenomenon of the liquid jet does not have a single frequency, and is broad-spectrum, under a fixed injection condition_nThere is not a completely stable one and some fluctuation will be exhibited. To this end, the present invention provides for l pairs by means of high speed cameras 22_nPerforming high-speed multiple acquisition, and averaging the acquired data to obtain formal l_nThen, the formal values of epsilon and delta are calculated by the above formula. In addition to this, l acquired at high speed and multiple times by the high-speed camera 22 may be acquired_nThe method comprises the steps of firstly, respectively substituting the values into the formula to obtain a plurality of groups of epsilon and delta, and then, respectively averaging the groups of epsilon and delta to obtain formal values of epsilon and delta.

Although the three conditions described above cannot be explicitly formulated as relating to f₁Due to f₁Implicit in k₁And a, so that the three conditions described above are fundamentally reflected in f₁I.e. the frequency range in which the control effect of "controlling the liquid jet break-up frequency" can be achieved. For example, for one flow rate Q of 1200. mu.l/min, radius r₀A pure water liquid jet of 60.16 μm, a surface tension change rate delta sigma/sigma of 1% is formed at the upper part of the pure water liquid jet (the position close to the caliber-adjustable liquid jet 21) by the pulse focusing heating of the outer layer pulse laser group 2₀Then the pure water liquid jet can realize the control effect of 'controlling the liquid jet breaking frequency' in the frequency range of 1213Hz-4674Hz, namely in the frequency range of 1213Hz-4674HzThe crushing frequency of the inner pure water liquid jet is equal to the pulse frequency of the outer layer pulse laser group 2, and then the controllable liquid drops which meet the requirements of the uniform droplet size and the uniform droplet spacing distance described by the control effect in the foregoing are crushed. The inventor of the present invention has made a strong proof of this through a large number of experiments.

Meanwhile, mathematical property analysis is performed on the three conditions, and after the upper and lower limit frequencies of the frequency range are calculated through the three conditions, the pulse frequency f of the outer layer pulse laser group 2 is obtained₁The value can be continuously taken in a frequency range formed by the upper and lower bound frequencies, and the control effect of controlling the liquid jet flow crushing frequency can be realized.

In addition, the three conditions and the frequency ranges reflected thereby are also used to define the frequency selection of the outer layer pulse laser group 2 in the foregoing extended example of delaying liquid jet breakup, and to define the frequency selection of the 2q-1 th pulse laser focused heating system in the foregoing extended example of delaying liquid jet breakup. Since the three conditions and the frequency ranges reflected thereby essentially reflect the conditions for suppressing the natural break-up of the liquid jet by the pulsed laser focused heating system.

Thirdly, controlling the liquid jet flow crushing length (crushing time):

as shown in (c) of fig. 6, by the technical means of "controlling the breaking frequency of the liquid jet" and satisfying the frequency range described above (i.e. satisfying the three conditions described above), the proposed apparatus of the present invention can control the breaking frequency of the liquid jet to be equal to the pulse frequency of the outer layer pulse laser group 2, and can also simultaneously control the breaking length of the liquid jet, and make the breaking length of the liquid jet satisfy the following expression:

wherein l_cFor liquid injection under the above-mentioned modulation of the deviceThe breaking length of the stream 34, as shown in (c) of FIG. 6, the subscript c denoting the control of the device on the breaking length (time) of the liquid jet 34, v being the jet velocity of the liquid jet, σ₀Is the initial surface tension of the liquid jet, r₀The radius of the liquid jet just after the liquid jet is sprayed out from the caliber-adjustable liquid spraying opening 21, rho is the liquid density of the liquid jet, f₁Is the pulse frequency, k, of the outer pulse laser group 2₁The wave number of Marangoni unstable wave excited by the outer layer pulse laser group 2 satisfies k₁＝2πf₁/v₀The subscript 1 here indicates the outer pulse laser group 2, a is a dimensionless mathematical expression and can be expressed as

Delta sigma is the surface tension change amplitude on the heated point of the liquid jet caused by pulse focusing heating of the outer layer pulse laser focusing heating system, and ln (·) is a natural logarithm operator.

Wherein l_cWhich can be measured by the high speed camera 22, the measurements for the remaining physical quantities can continue using the respective measuring methods disclosed above in the introduction "controlling the liquid jet break up frequency".

As already highlighted above, the "jet break up length" represents the distance of the liquid jet from the "nozzle orifice" to the "first break up position", so that the "jet break up length" is equal to the product of the speed of said liquid jet and the time between the ejection of the liquid jet from the "adjustable orifice" and the "first break up" in the present invention (referred to as "liquid jet break up time"). Since the speed v of the liquid jet can be controlled by the injection pump 24 and the caliber-adjustable liquid jet 21, the focus of the device on the control of the liquid jet crushing length is essentially on the control of the liquid jet crushing time, and the control of the liquid jet crushing time can be expressed by the following formula:

wherein, t_cFor the break up time of the liquid jet 34 at the above modulation of the device, the subscript c indicates the control of the device on the break up time (length) of the liquid jet.

In principle, the pulsed heating of the liquid jet by the outer set of pulse lasers 2 essentially changes the surface tension on the liquid jet, so that a spaced-apart high-low distribution of surface tension is created on the moving liquid jet, thereby inducing a Marangoni flow on the liquid jet, correspondingly creating a Marangoni unsteady wave. This Marangoni flow means that while the liquid jet moves as a whole, fluid in low surface tension regions of the liquid jet flows towards high surface tension regions of the liquid jet, causing the high surface tension regions to expand and the low surface tension regions to contract accordingly. In accordance with the invention, it is then the location where the liquid jet is heated that contracts over time and the location where it is not heated that correspondingly expands over time. When the Marangoni unsteady waves excited by the outer layer pulse laser set 2 completely suppress the natural breaking phenomenon of the liquid jet and are not cancelled out by the pulse heating of the inner layer pulse laser set 11, the Marangoni unsteady waves excited by the outer layer pulse laser focusing heating system completely dominate the breaking phenomenon of the liquid jet 34. The liquid jet breaking time is essentially the time between the ejection of the liquid jet from the adjustable-caliber liquid ejection port 21 and the "pinching-off" of the liquid jet by the Marangoni unstable wave, and the invention is based on the above formula for the liquid jet breaking time t_cThe control is carried out, and further the control on the jet velocity v of the liquid jet is combined to realize the crushing length l of the liquid jet_cAnd (4) controlling.

Fourthly, customizing the frequency distribution of liquid jet flow crushing and the particle size distribution and the interval distance distribution of liquid drops generated after the liquid jet flow crushing (which can meet various distribution forms such as Gaussian distribution, Poisson distribution and the like);

the device can control the crushing frequency of the liquid jet to be at a certain single frequency, can customize the frequency distribution of the liquid jet crushing and the particle size distribution and the spacing distance distribution of liquid drops generated after the liquid jet is crushed, and can meet various distribution forms such as Gaussian distribution and Poisson distribution.

For example, for the study of cloud dynamics, the relevant researchers need a droplet group with a certain particle size distribution (such as gaussian distribution, poisson distribution, etc.) as an experimental study object, and the natural fragmentation phenomenon relying solely on liquid jet obviously cannot meet the technical requirement. This control effect of the device proposed by the present invention can meet the experimental technical requirements of the cloud dynamics research.

Specifically, as shown in fig. 6 (d) and fig. 7(b), to achieve this control effect, the inner pulsed laser focusing heating system of the device is turned off, and only the outer pulsed laser focusing heating system is kept in operation, and the outer pulsed laser focusing heating system is no longer at a single frequency, but exhibits a frequency distribution pattern for pulse-heating the upper portion of the liquid jet according to the frequency distribution pattern.

When the pulse laser power of the outer layer pulse laser focusing heating system is high enough, and the outer layer pulse laser focusing heating system inhibits the natural breaking phenomenon of the liquid jet, the development of the unstable wave excited by the outer layer pulse laser focusing heating system can not be counteracted by the inner layer pulse laser focusing heating system any more, and the development of the unstable wave of the surface tension change of the liquid jet excited by the outer layer pulse laser group 2 can completely guide the breaking phenomenon of the liquid jet 36. At this time, the unstable wave of the surface tension change of the liquid jet satisfies the frequency distribution form of the outer layer pulse laser focusing heating system, the correspondingly generated liquid jet fragmentation phenomenon also satisfies the frequency distribution form, and the droplets 37 generated by the fragmentation of the liquid jet 36 also satisfies the frequency distribution form.

It is particularly emphasized that the power of the outer layer pulse laser group 2 is now no longer varied over time at a single frequency as was the case when the "control of the liquid jet break-up frequency" was implemented as described above, but rather exhibits a frequency distribution, as shown in fig. 7 (b).

As shown in fig. 7, the time-varying control signals transmitted to the outer layer pulse laser group 2 by the proposed apparatus of the present invention are (a) a control signal for controlling the frequency and length of the break-up of the liquid jet (break-up time), and (b) a control signal for customizing the droplet distribution pattern generated after break-up of the liquid jet. The horizontal axis t in fig. 7 represents time, and the vertical axis V represents the magnitude of the voltage value of the control signal and has a unit of volts (V). When the control signal is 0V, the instantaneous power of the pulse laser emitted by the outer layer pulse laser group 2 is 0; when the control signal is 5V, the instantaneous power of the pulse laser emitted by the outer layer pulse laser group 2 is a certain constant value, and the magnitude of the constant value of the instantaneous power of the pulse laser can be controlled.

When the device is used for controlling the liquid jet flow crushing frequency and the liquid jet flow crushing length (crushing time), the control signal transmitted to the outer layer pulse laser group 2 is in the form of (a) in fig. 7, and the change of the power of the corresponding outer layer pulse laser group 2 along with time also takes the form, namely the change of the instantaneous power of the outer layer pulse laser group 2 along with time is in a certain single frequency. In this case, the outer pulse laser group 2 has a fixed frequency f₁And period 1/f₁。

When the device is used for customizing the frequency distribution of liquid jet flow crushing and the particle size distribution and the spacing distance distribution of generated liquid drops after crushing, the control signal transmitted to the outer layer pulse laser group 2 is in the form of (b) in fig. 7, and the change of the power of the corresponding outer layer pulse laser group 2 along with time also takes the form, namely the change of the instantaneous power of the outer layer pulse laser group 2 along with time takes the form of the frequency distribution. At this time, the outer layer pulse laser group 2 does not have a fixed frequency and period, that is, the frequency and period of the instantaneous power of the outer layer pulse laser group 2 change in real time with time. This frequency distribution pattern is also satisfied by Marangoni unsteady waves of the liquid jet surface tension variations.

In principle, since the Marangoni unstable wave of the surface tension variation of the liquid jet excited by the outer layer pulse laser group 2 completely dominates the break-up phenomenon of the liquid jet 36, when the real-time frequency of the outer layer pulse laser group 2 is increased, the break-up frequency of the liquid jet excited by the device is increased, and then the liquid drops with smaller particle size and smaller spacing distance are generated. When the real-time frequency of the outer layer pulse laser group 2 is reduced, the breaking frequency of the liquid jet excited by the device is reduced, and liquid drops with larger particle size and larger spacing distance are generated. Then, when the real-time frequency of the outer layer pulse laser group 2 changes with time to satisfy a certain distribution form (for example, a distribution form such as gaussian distribution, poisson distribution, etc.), the Marangoni unstable wave of the surface tension change of the liquid jet excited by the outer layer pulse laser focusing heating system also satisfies the distribution form, and then the breaking frequency of the liquid jet excited by the device also satisfies the distribution form, and then the liquid drop with the size of the liquid drop and the liquid drop interval distance satisfying the distribution form is generated. And combining the frequency distribution of the pulse laser, the breaking frequency distribution of the liquid jet, the particle size (distribution) of the generated liquid drops after breaking and the spacing distance (distribution) can be accurately calculated.

For example, as shown in (b) of fig. 7, when the pulse frequency of the control signal transmitted to the outer layer pulse laser group 2 is first high, then decreases with time, and then increases with time. Then, as shown in fig. 6 (d), the size of the droplets 37 generated after the liquid jet 36 is broken is smaller, larger in the jetting direction, and smaller in the jetting direction. For the same reason, as shown in fig. 6 (d), the distance between the droplets 37 generated after the liquid jet 36 is broken is smaller, then larger in the jetting direction, and then smaller in the jetting direction. In summary, under the pulse focusing heating modulation of the outer layer pulse laser group 2 satisfying the pulse frequency distribution shown in fig. 7(b), the breaking frequency distribution of the liquid jet 36 and the particle size distribution and the spacing distance distribution of the generated droplets 37 after breaking satisfy the pulse frequency distribution form of the outer layer pulse laser group 2 at this time. If the frequency distribution of the outer layer pulse laser group 2 satisfies the distribution form such as gaussian distribution and poisson distribution, the breaking frequency distribution of the liquid jet 36 and the particle size distribution and the spacing distance distribution of the liquid drop 37 generated after breaking both satisfy the distribution form such as gaussian distribution and poisson distribution of the outer layer pulse laser group 2 at this time.

Finally, it is emphasized that the liquids to which the present invention is directed are low viscosity fluids, such as pure water (pure water may be considered a non-viscous fluid). The surface tension of the low-viscosity liquid jet is changed by the pulse laser heating, and then Marangoni unstable waves with changed surface tension are induced, so that various control effects in the above can be selectively realized under different embodiments. In the implementation process of the invention, the gravity effect is not utilized in the invention, and the spraying direction of the liquid jet is not limited to be vertical downwards and can be towards any direction in the space, which is essentially different from some technologies that the high-viscosity liquid jet is pulled off by changing the viscosity and relying on the gravity.

Claims

1. A device for controlling liquid jet flow crushing comprises a cavity, an outer layer pulse laser focusing heating system and an inner layer pulse laser focusing heating system which are arranged in the cavity, and a measuring system which is arranged outside the cavity;

2. An apparatus for controlling break up of a liquid jet as claimed in claim 1 wherein said lower convex lens mount with a lower convex lens mounted thereon is located inwardly of a lower mirror mount with a lower mirror mounted thereon, and wherein the lower convex lens mount and the lower mirror mount are located at the same horizontal plane; the third rotation controller controls the lower reflector mounting rack provided with the lower reflector to move up and down through the lower reflector screw rod; and the fourth rotation controller controls the lower-layer convex lens mounting frame provided with the lower-layer convex lens to move up and down through the lower-layer convex lens screw rod.