阅读说明：本技术 Ldv测量圆管内部二维流场的装置 (Device for measuring two-dimensional flow field inside circular tube by LDV (laser direct-current voltage) ) 是由 王德忠 宋煜 尹俊连 马元巍 黄松 于 2020-05-29 设计创作，主要内容包括：本发明提供了一种LDV测量圆管内部二维流场的装置,包括待测圆管、移动台架底座、移动台架底板、丝杠滑块移动台、LDV探头以及支撑载体,移动台架底座、移动台架底板都安装在支撑载体上；所述移动台架底座包括载物台以及滑轨,所述待测圆管安装在载物台上,丝杠滑块移动台通过LDV旋转台安装在移动台架底板上,所述LDV探头安装在丝杠滑块移动台上,移动台架底板在电机的驱使下带动台架移动电机、LDV旋转台、丝杠滑块移动台、LDV探头绕待测圆管在滑轨上运动,本发明实现了LDV探头3个自由度的移动调节,具备圆管内测量空间点自动对准功能以及折射后空间点对准功能,提高了检测效率和准确性,结构简单,控制灵活。(The invention provides a device for measuring a two-dimensional flow field inside a circular tube by an LDV (laser direct current), which comprises a circular tube to be measured, a moving rack base, a moving rack bottom plate, a screw slide block moving platform, an LDV probe and a support carrier, wherein the moving rack base and the moving rack bottom plate are arranged on the support carrier; the movable rack base comprises an object stage and a slide rail, the round tube to be measured is installed on the object stage, the lead screw slider moving platform is installed on the movable rack bottom plate through the LDV rotating platform, the LDV probe is installed on the lead screw slider moving platform, the movable rack bottom plate drives the rack moving motor, the LDV rotating platform, the lead screw slider moving platform and the LDV probe to move on the slide rail around the round tube to be measured under the driving of the motor.)

1. A device for measuring a two-dimensional flow field in a circular tube by an LDV (laser direct-current Voltage) is characterized by comprising a circular tube to be measured (1), a moving rack base (2), a moving rack bottom plate (3), a screw slide block moving platform (6), an LDV probe (7) and a support carrier (11);

the moving rack base (2) and the moving rack bottom plate (3) are both arranged on a support carrier (11);

the round pipe (1) to be tested is arranged on a moving rack base (2), and a rack moving motor (4) is arranged on a moving rack bottom plate (3);

the lead screw sliding block moving platform (6) is installed on the moving platform frame bottom plate (3) through the LDV rotating platform (5), and the LDV probe (7) is installed on the lead screw sliding block moving platform (6);

the rack moving motor (4) can drive the moving rack bottom plate (3) to drive the LDV rotating table (5), the lead screw sliding block moving table (6) and the LDV probe (7) to move around the round pipe (1) to be measured.

2. The device for LDV measurement of two-dimensional flow field inside a round tube according to claim 1, wherein the moving gantry base (2) comprises an object stage (9) and a slide rail (10) arranged along the circumference of the object stage (9), and the round tube (1) to be measured is mounted on the object stage (9).

3. The device for LDV measurement of the two-dimensional flow field inside the circular tube according to claim 2, wherein the circular tube (1) to be measured is arranged concentrically with the stage (9).

4. The device for LDV measurement of two-dimensional flow field inside a circular tube according to claim 1, further comprising a flat mirror (8), wherein said flat mirror (8) is mounted on the LDV probe (7).

5. The device for LDV measurement of two-dimensional flow field inside a circular tube as claimed in claim 4, wherein said plane mirror (8) can change the included angle of the beam of LDV probe (7) in horizontal direction.

6. The LDV device for measuring the two-dimensional flow field inside the circular tube according to claim 2, wherein the object stage (9) is a circular object stage and a driving tooth extends out of the circular object stage along the circumferential direction, the rack moving motor (4) is connected with a transmission gear, the transmission gear is matched and meshed with the driving tooth, and when the rack moving motor (4) is started, the transmission gear rotates and drives the moving rack bottom plate (3) to move on the sliding rail under the meshing force of the driving tooth.

7. The device for LDV measurement of two-dimensional flow field inside a circular tube as claimed in claim 1, wherein the LDV rotating table (5) can drive the screw slide moving table (6) and the LDV probe (7) to rotate.

8. The device for LDV measurement of two-dimensional flow field inside circular tube according to claim 7, wherein the rotation angle of the LDV rotating table (5) is 360 °.

9. The device for LDV measurement of the two-dimensional flow field inside the circular tube as recited in claim 1, wherein the lead screw slider moving table (6) can drive the LDV probe (7) to move back and forth.

10. The device for LDV measurement of the two-dimensional flow field inside the circular tube according to claim 5, further comprising a control device, wherein the control device is capable of obtaining the spatial position of the LDV probe (7) corresponding to the point to be measured in the circular tube (1) to be measured by calculating the vertical light path, adjusting the LDV probe (7) to the required position under the control of the control device, obtaining the rotation parameter of the plane mirror (8) by correcting the horizontal light path for 2 times, leveling the plane mirror (8) under the control of the control device so that two sets of light beams of the LDV probe (7) are intersected with the same spatial point in the circular tube (1) to be measured, obtaining the parameter that the corresponding LDV probe (7) of each spatial point needs to move by calculating, and controlling the LDV probe (7) to move automatically by the control device, and completing the automatic measurement of each spatial point to be measured.

Technical Field

The invention relates to the technical field of laser measurement, in particular to a device for measuring a two-dimensional flow field inside a circular tube by an LDV (laser direct-view).

Background

Laser Doppler Velocimetry (LDV) measures the Doppler signals of trace particles passing through a Laser probe and then obtains the velocity from the relationship between the velocity and the Doppler frequency. Because of laser measurement, the flow field is not interfered, the speed measurement range is wide, and because the Doppler frequency and the speed are in a linear relation and have no relation with the temperature and the pressure of the point, the Doppler frequency and the speed measurement instrument is the instrument with the highest speed measurement precision in the world at present.

The laser Doppler velocimeter has the characteristics of non-contact property, no interference to a flow field, high accuracy, quick response and the like. The method has great superiority in the aspect of measuring the flow field velocity inside the pipeline. In the case of a pipe with both ends sealed, the flow field inside the pipe can only be measured from outside the pipe wall. When liquid exists in the pipeline and the flow field of the liquid is to be measured, a window is usually opened on the pipe wall of the circular pipe, or an optical compensation device is added on the outside. And the flow state of the internal flow field can be changed by adding the optical compensation device, and the optical compensation device added externally can be influenced by the number of the measuring points and the space size, so that when a large number of measuring points exist inside the circular tube and the external optical compensation device is inconvenient to build, a device capable of automatically positioning each measuring point and compensating the light path needs to be designed.

Patent document CN1595170A discloses a doppler velocimeter based on self-mixing interference effect, belonging to the field of laser measurement. The velocimeter consists of 3 parts, namely a light source, a measuring part and a signal processing part. The system light source uses a double-frequency laser, and a quarter wave plate is arranged on the measuring part of the self-mixing interference system, namely the system external cavity, the fast axis direction of the quarter wave plate and the polarization directions of two polarized lights respectively form an angle of 45 degrees, so that the light beam travels back and forth in the external cavity, and the polarization direction of the light beam is changed into the original vertical direction. For the self-mixing interference velocimeter, when no Doppler frequency shift exists, only one spectral line is on the power spectrum of the laser, when the Doppler frequency shift exists, the original spectral line on the power spectrum is changed into two spectral lines, the positive and negative of the difference value of the two spectral lines corresponding to the beat frequency signal represent the direction of the speed, the distance between the two spectral lines can be converted into the speed, but the design still cannot solve the problem of speed measurement when a plurality of measuring points exist inside the circular tube.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a device for measuring a two-dimensional flow field in a circular tube by an LDV.

The device for measuring the internal two-dimensional flow field of the circular tube by the LDV comprises the circular tube to be measured, a moving rack base, a moving rack bottom plate, a lead screw sliding block moving platform, the LDV probe and a support carrier, wherein the moving rack base is arranged on the moving rack bottom plate;

the moving rack base and the moving rack bottom plate are both arranged on the supporting carrier;

the round pipe to be tested is arranged on a base of the moving rack, and a rack moving motor is arranged on a bottom plate of the moving rack;

the lead screw sliding block moving platform is arranged on the bottom plate of the moving platform frame through the LDV rotating platform, and the LDV probe is arranged on the lead screw sliding block moving platform;

the rack moving motor can drive the moving rack bottom plate to drive the LDV rotating table, the lead screw sliding block moving table and the LDV probe to move around the round pipe to be measured.

Preferably, the moving platform base comprises an object stage and a slide rail arranged along the circumferential direction of the object stage, and the round tube to be tested is installed on the object stage.

Preferably, the round tube to be tested and the object stage are arranged concentrically.

Preferably, the laser device further comprises a plane mirror, and the plane mirror is installed on the LDV probe.

Preferably, the plane mirror can change the included angle of the light beam in the horizontal direction of the LDV probe.

Preferably, the objective table is circular objective table and circular objective table extends along the circumferential direction and drives the tooth, rack traveling motor is connected with drive gear, drive gear and the meshing of driving tooth matching, drive gear rotates and drives about the traveling gantry bottom plate and move on the slide rail under the effect of driving tooth meshing force when rack traveling motor starts.

Preferably, the LDV rotating platform can drive the screw slide block moving platform and the LDV probe to rotate.

Preferably, the rotation angle of the LDV rotary table is 360 °.

Preferably, the lead screw sliding block moving platform can drive the LDV probe to move back and forth.

Preferably, the device further comprises a control device, the control device can obtain the spatial position of the LDV probe corresponding to the point to be measured in the round tube to be measured through calculation of the vertical light path, adjust the LDV probe to the required position under the control of the control device, obtain the rotation parameters of the plane mirror through 2 times of correction of the horizontal light path, adjust the plane mirror under the control of the control device so that two groups of light beams of the LDV probe are intersected with the same spatial point in the round tube to be measured, obtain the parameter, which needs to be moved, of the corresponding LDV probe of each spatial point through calculation, control the LDV probe to automatically move by the control device, and complete automatic measurement of each spatial point to be measured.

Compared with the prior art, the invention has the following beneficial effects:

1. according to the invention, the mobile rack is designed to enable the LDV probe to realize the mobile adjustment with 3 degrees of freedom, the base of the mobile rack can move along the circumferential direction, the LDV rotating table can rotate for 360 degrees, the screw rod sliding block mobile platform can move back and forth, the automatic alignment function of the measured space point in the circular tube and the alignment function of the space point after refraction are realized, the defects that when a large number of measuring points exist in the circular tube in the prior art, each time of manually adjusting the LDV probe will cost a large amount of time and labor cost and the measurement is inaccurate are overcome, the detection efficiency and accuracy are improved, the structure is simple, and the control is flexible.

2. The invention starts from the fact that different light beams emitted by the LDV probe can not intersect at the same space point, combines the geometric shape of the round tube to be measured and the refractive indexes of different media inside and outside, carries out theoretical calculation through the light path diagram, and designs the rack without an additional optical compensation device, so that the light beams emitted by the LDV probe can intersect at the same space point, and the structure is simple and the practicability is strong.

3. According to the invention, the space coordinate position of the LDV probe when the LDV detection body reaches the actual space point position is obtained through theoretical calculation of the light path, and automatic point searching and measurement of the LDV rack are realized through programming, so that the method is rapid and accurate, and has high automation degree.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a schematic top view of the present invention;

FIG. 3 is a schematic view of the structure of a flat mirror according to the present invention;

FIG. 4 is a schematic view of horizontal optical path correction according to the present invention;

FIG. 5 is a schematic view of vertical optical path correction according to the present invention;

FIG. 6 is a schematic diagram of the horizontal optical path correction with a plane mirror according to the present invention.

The figures show that:

objective table 9 of round tube 1 LDV rotary table 5 to be tested

Sliding rail 10 of moving platform 6 of lead screw sliding block of moving platform base 2

Moving rack bottom plate 3 LDV probe 7 support carrier 11

Table moving motor 4 plane mirror 8

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.

The invention provides a device for measuring a two-dimensional flow field inside a circular tube by an LDV (laser direct-current), which comprises a circular tube to be measured 1, a moving rack base 2, a moving rack bottom plate 3, a screw slide block moving platform 6, an LDV probe 7 and a support carrier 11, wherein the moving rack base 2 and the moving rack bottom plate 3 are both arranged on the support carrier 11; the moving rack base 2 comprises an object stage 9 and slide rails 10 arranged along the circumferential direction of the object stage 9, and the to-be-tested circular tube 1 is installed on the object stage 9; a rack moving motor 4 is arranged on the moving rack bottom plate 3; the lead screw sliding block moving platform 6 is installed on the moving rack bottom plate 3 through the LDV rotating platform 5, and the LDV probe 7 is installed on the lead screw sliding block moving platform 6; the rack moving motor 4 can drive the moving rack bottom plate 3 to drive the rack moving motor 4, the LDV rotating table 5, the lead screw sliding block moving table 6 and the LDV probe 7 to move on the sliding rail 10 around the round pipe 1 to be measured.

Specifically, in a preferred embodiment, the LDV rotary table 5 is mounted on the moving gantry base plate 3 by bolts.

Specifically, as shown in fig. 1, the circular tube 1 to be measured is concentrically arranged with the stage 9.

Further, as shown in fig. 1-3, the objective table 9 is a circular objective table and the circular objective table extends out of the driving teeth along the circumferential direction, the stage moving motor 4 is connected with a transmission gear, the transmission gear is engaged with the driving teeth in a matching manner, when the stage moving motor 4 rotates, the transmission gear is driven to rotate and the moving stage bottom plate 3 is driven to move on the sliding rail under the action of the driving teeth, in a preferred embodiment, the bottom of the moving stage bottom plate 3 is provided with a pulley, and the moving track of the pulley and the cross section of the round tube 1 to be measured are concentrically arranged.

Furthermore, as shown in fig. 1, the rotating table 5 can drive the lead screw slider moving table 6 and the LDV probe 7 to rotate, and the rotation angle is 360 °; the lead screw slide block moving platform 6 can drive the LDV probe 7 to move back and forth.

Specifically, as shown in fig. 1, the laser scanning device further comprises a plane mirror 8, wherein the plane mirror 8 is installed in front of the LDV probe 7, and the plane mirror 8 can change an included angle of a beam in the horizontal direction of the LDV probe 7.

Specifically, the LDV detection device is also provided with a control device, the control device obtains the space coordinate position of the LDV probe 7 when the LDV detection body reaches the actual space point position through theoretical calculation of the light path, and automatic point searching and measurement of the LDV rack are realized through programming.

Further, the control device can obtain the spatial position of the LDV probe 7 corresponding to the to-be-measured point in the round tube 1 to be measured by calculating the vertical light path, adjust the LDV probe 7 to the required position under the control of the control device, and obtain the rotation parameter of the plane mirror 8 by correcting the horizontal light path for 2 times, and adjust the plane mirror 8 under the control of the control device so that two groups of light beams of the LDV probe 7 are intersected at the same spatial point, and obtain the parameter that the corresponding LDV probe 7 of each spatial point needs to move by calculating, the control device controls the LDV probe 7 to automatically move, and completes the automatic measurement of each spatial point to be measured.

Specifically, considering that the light beams emitted by the LDV probe 7 are refracted when passing through the circular tube 1 to be measured, if each group of light beams is supposed to pass through the circular tube 1 to be measured and then reach the point to be measured, the light path after refraction needs to be corrected, as shown in fig. 4, for a horizontal light beam, the optical axis of the horizontal light beam passes through the center of the measuring plane, so that only one of the two light beams is considered, wherein the outside of the measuring tube section is air, and the refractive index is denoted as n_aAnd the refractive index of the measured pipe section is recorded as n_gFor example, the measuring tube section is made of glass, the inside of the measuring tube section is made of fluid, such as water, and the refractive index is recorded as n_wThe light beam is refracted a first time at the air-glass interface and a second time at the glass-water interface.

Specifically, as shown in fig. 4 to 6, the calculation of the optical path correction includes a horizontal direction beam correction calculation, a vertical direction beam correction calculation, and a horizontal direction beam correction calculation 2 times.

Further, as shown in fig. 4, for the light beam in the horizontal direction, the light beam emitted by the LDV probe 7 is refracted when passing through the round tube 1 to be measured, so that each group of light beams passes through the round tube 1 to be measured and then joins the point to be measured, the light path after refraction needs to be corrected, the light beam emitted by the LDV probe 7 enters the round tube 1 to be measured from the air first to be refracted for the first time, and then enters the fluid inside the round tube 1 to be measured from the round tube 1 to be measured to be refracted for the second time, the refracted light path is as shown in fig. 4, if no refraction occurs, theoretically two light beams join N points, and after refraction occurs, the two light beams join M points, the segment AF is half of the beam interval of the probe, and the beam interval is d which is the. Therefore, there are:

line FN is probe focal length, recorded as f, beam angle is LDV probe parameter, β is half beam angle, α is half refracted beam angle, on air-glass interface, α₄As angle of incidence of the light beam, α₃Angle of refraction, at glass-water interface α₂As angle of incidence of the light beam, α₁Is the angle of refraction. The point O is the center of a circle, OC is the inner diameter of the circular tube and is marked as R, and OB is the outer diameter of the circular tube and is marked as R. Therefore, we will note the point M as the point to be measured, and given the length of the line segment OM, we can obtain from the geometric relationship:

by the formula, half alpha of the included angle of the refracted light beam can be obtained, the spatial position of the LDV probe 7 is finally obtained according to the geometrical relationship of refraction by calculating alpha and combining with the known focal length of the LDV probe 7,

further, as shown in fig. 4, if the position parameters of the probe are to be known, the lengths of the line segments DF and ND need to be known, first, the length of the line segment ND can be obtained by solving the length of the line segment BD, and since NF is the focal length of the probe and is a known parameter, the length of the line segment DF can be obtained, and according to the geometric relationship, the projection of the line segments MC and CB in the direction of the BD can be represented by the following formula:

BD＝MC sinα+CB sin(α+α₂-α₁)

FD＝NF-ND

in summary, the spatial positions of the LDV probe 7 are:

OM+MD+FD＝OM+MC cosα+CB cos(α+α₂-α₁)+FD

wherein n is_aIs the refractive index, n, of the air outside the round tube 1 to be measured_gThe refractive index n of the section of the round tube 1 to be measured_wThe refractive index of the fluid in the round tube 1 to be measured, f is the focal length of the LDV probe 7, β is half of the included angle of the light beam, as shown in FIG. 4, α₃From air to round tube to be measuredAngle of refraction of 1, α₄α is the incident angle from the air to the round tube 1 to be measured₁Angle of refraction of fluid from the pipe 1 to be tested to the interior of the pipe 1 to be tested α₂In order to obtain the incident angle from the round pipe 1 to be measured to the fluid inside the round pipe 1 to be measured, the inner radius of the round pipe 1 to be measured is R, the outer radius of the round pipe 1 to be measured is R, O is the center of a circle on the cross section of the round pipe 1 to be measured, and M is the point to be measured inside the round pipe 1 to be measured.

Specifically, for the light beam in the vertical direction, the refraction path is as shown in fig. 5, if no refraction occurs, theoretically two light beams intersect with N point, and after refraction occurs, they intersect with M point, the line segment AF is half of the beam distance of the probe, the beam distance is the LDV probe parameter and is denoted as d, so there are:

line FN is probe focal length, recorded as f, beam angle is LDV probe parameter, β is half of beam angle, α is half of refracted beam angle, on air-glass interface, α₄As angle of incidence of the light beam, α₃Angle of refraction, at glass-water interface α₂As angle of incidence of the light beam, α₁Is the angle of refraction. The point O is the center of a circle, OE is the inner diameter of the circular tube and is marked as R, and OD is the outer diameter of the circular tube and is marked as R. Therefore, we mark the point M as the point to be measured, and give the length of the line segment OM, which is:

as can be seen from fig. 5, if the position parameters of the probe are to be known, the length of the line segment DF needs to be known. Firstly, the length of the segment ND can be obtained by solving the length of the segment BD, and the length of the segment DF can be obtained because NF is the focal length of the probe and is a known parameter. According to the geometric relationship, the projection of the line segment MC and the line segment CB in the BD direction can be represented by the following formula:

BD＝MC sinα+CB sinα₂

BD＝(r-OM)tanα+(R-r)tanα₂

FD＝NF-ND

in summary, the spatial positions of the LDV probe 7 are:

finally obtaining the space position of the LDV probe 7 according to the geometric relation of refraction by the obtained α and combining with the known focal length of the LDV probe 7, wherein the included angle of the light beam is a parameter of the LDV probe 7, n_aIs the refractive index, n, of the air outside the round tube 1 to be measured_gThe refractive index n of the section of the round tube 1 to be measured_wβ is half of the included angle of the light beam for the refractive index of the fluid in the round tube 1 to be measured, and α is arranged on the interface from the external atmosphere to the round tube 1 to be measured₄As angle of incidence of the light beam, α₃At the interface of the pipe 1 to be measured to the fluid, α, angle of refraction₂As angle of incidence of the light beam, α₁The refraction angle is a refraction angle, the point O is the center of the cross section of the round tube 1 to be measured, the radius of the inner part of the round tube 1 to be measured is R, and the radius of the outer part of the round tube 1 to be measured is R.

Specifically, as shown in fig. 6, in order to make the detectors of two sets of beams in the horizontal direction and the vertical direction intersect at a point, the position of the detector in the vertical optical path can be calculated first through the above relationship, and the position of the detector can be adjusted by placing a plane mirror on the horizontal optical path.

Firstly, the position OF the probe after the adjustment OF the vertical optical path is 1x ═ OF, and then on the horizontal optical path, the angle OF the plane mirror is changed while ensuring that 1x is unchanged. The initial position of the rotation axis of the plane mirror at a distance FE of 50mm from the probe is designated as G, and the initial angle is designated as 0 at this time. Then, the plane mirror on one side rotates anticlockwise as shown in the figure, the rotation angle is beta, and the beam included angle becomes:

β₀＝β+2β

in the triangular OMB, the sine theorem is used, which includes:

wherein:

ON＝l_x-FE-EN

EG＝(OF-FE)*tanβ≈25mm

thus, α can be obtained₄As to the function of the rotation angle β, there are further:

α＝α₁-α₂+α₃-α₄+β

and finally, according to the triangular OMC, obtaining a relational expression by adopting a sine theorem:

α therein₁And α are quantities related to the mirror rotation angle β, and the rotation angle β can be obtained from this relational expression.

In the description of the present application, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present application and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present application.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.