CN106092501A - Rotary variable-diameter pipe flow field experimental apparatus for testing - Google Patents

Abstract

Disclosed is an experimental device for testing the flow field in a rotary reducing circular tube. The main purpose is to solve the problems of insufficient strength of the plexiglass variable-diameter circular tube used for flow field testing under the condition of wall rotation and difficulty in compensating the refractive index of the rotating variable-diameter circular tube in the existing experimental device. It is characterized in that: the test device for the flow field of the rotating variable-diameter circular tube includes a variable-diameter circular tube unit, a support and connection unit, a power and transmission unit, and a refractive index compensation unit; the variable-diameter circular tube unit is sequentially composed of an overflow pipe, an overflow nozzle, The tangential inlet plate, plexiglass reducing tube, tapered tube and tail tube are connected by flanges; the power and transmission unit includes a motor, a transmission shaft and a transmission belt, and its function is to drive the reducing tube to rotate; the supporting and connecting unit includes Bearings, bearing housings, support guide rails, drive shaft brackets, etc., play the role of supporting the connection and sealing between the variable diameter circular tube and the drive shaft, as well as the pipeline; the refractive index compensation unit is installed on the plexiglass section of the variable diameter circular tube to realize laser The role of refractive index compensation.

Description

Experimental device for testing the flow field in a rotating variable diameter circular tube

Technical field:

The invention relates to an experimental device for testing the flow field in a rotating variable-diameter circular tube, which is applied in the technical field of flow field testing.

Background technique:

There are various rotary flow problems in the industrial field. Accurately describing the flow law of rotary flow is helpful to improve the design of fluid equipment structure, optimize operating parameters, and improve the performance and efficiency of rotary fluid equipment. The helical flow in a rotating circular pipe with variable diameter is a kind of complex rotating turbulent flow problem, which has the coupling effect of circumferential rotation and flow shear, and has two characteristics of helical flow and forced rotating flow in an axially rotating pipe, which contains The complex physical mechanism of turbulent flow has an important application background in the field of engineering technology, such as the application of moving walls in turbulent drag reduction, the application of hydrocyclones in downhole oil-water separation and offshore platforms, etc. The research on this kind of complex turbulent motion coupled with wall rotation is still very lacking. At present, it is still mainly concentrated in the scope of numerical simulation, lacking credible experimental results, and limited by the accuracy of numerical simulation research, it is still impossible to quantitatively study it. carry out. Therefore, the development of corresponding experimental equipment and experimental methods is a more reliable method to study this complex flow. The experimental device for testing the flow field in the rotating variable-diameter circular tube has not been found in the literature at home and abroad. According to the characteristics of the flow field, the related flow field research devices and methods are mainly focused on the static variable-diameter circular tube. (Static hydrocyclone) or the test of the flow field in a rotating circular tube, such as the static hydrocyclone flow field laser velocity measurement device established by Marins et al. However, the existing experimental devices of this kind generally have the problems of insufficient strength of the plexiglass variable-diameter circular tube under the condition of wall rotation and difficulty in compensating the refractive index of the rotating variable-diameter circular tube for flow field testing.

Invention content:

In order to solve the technical problems mentioned in the background technology, the present invention provides an experimental device for testing the flow field in a rotating and reducing circular tube. This common complex flow in the field of wall rotation coupled with its own rotation can realize the laser velocity measurement research of its internal flow field, and test the flow law of the helical flow in the variable-diameter circular tube under different wall rotation speeds and different flow rates.

The technical solution of the present invention is: the experimental device for testing the flow field in the rotating variable-diameter circular tube is composed of four parts: a variable-diameter circular tube unit, a support and connection unit, a power and transmission unit, and a refractive index compensation unit;

The variable-diameter circular tube unit, whose function is to rotate the fluid, is composed of a circular tube-shaped inlet connected to multiple sections of straight tubes or variable-diameter tubes with different diameters; among them, from left to right are overflow tube, overflow tube Nozzle, tangential inlet plate, plexiglass reducer, cone and tailpipe, the overflow pipe, overflow nozzle, tangential inlet plate, plexiglass reducer, cone and tailpipe The flange is connected with the bolt, and the joint is matched to ensure the overall coaxiality requirements after assembly;

The overflow pipe is a pipe structure with a flange at one end, and the outer wall of the middle part of the pipe is provided with a keyway and a ring groove for installing the timing belt pulley, and the inner hole on one side of the flange is threaded for installing the overflow nozzle; The overflow nozzle is a pipe structure with an external thread at one end; the tangential inlet plate is a hollow plate-shaped flange structure, the inner diameter of which is equal to the inner diameter of the straight pipe section of the plexiglass variable diameter tube, and two holes are opened on one side of the plate. There are two tangential inlets, and the flow channel is in the form of a gradual cross section, which provides a channel for the liquid to enter the reducing tube and make it form a spiral flow; the plexiglass reducing tube is a plexiglass material reducing tube with flanges at both ends The different diameter sections are divided into straight pipe section, large cone section and small cone section; the tapered pipe is a pipe structure with a flange at one end, and the inner hole on the side of the flange is a tapered hole, and the taper and the plexiglass variable diameter The small cone section of the pipe is the same, the inner hole at the rear of the tapered pipe is a straight hole, and the middle part of the outer wall of the tapered pipe is provided with a keyway and a ring groove for installing the timing pulley; the end of the tapered pipe is provided with a keyway, a half-ring groove and a sealing ring for installation The groove is used to install a detachable movable flange; the tail pipe is also a pipe structure with a flange at one end, and the flange end is used to connect with the taper pipe flange, and its inner hole is a stepped hole structure, and the inner hole of the flange end The hole is slightly larger to match the tapered tube and O-ring;

The function of the support and connection unit is to support the variable-diameter circular pipe unit, realize the dynamic and static separation and connect the pipeline; the support and connection unit includes a support seat and a guide rail assembly, a bearing composed of a bearing seat and self-aligning ball bearings Seat assembly, bearing seat base, inlet cavity assembly composed of inlet cavity and inlet cavity cover, outlet component composed of outlet cavity and outlet cover, drive shaft bracket, legs, and outlet base plate and inlet base plate; The guide rail assembly is composed of a guide rail and a drive shaft bracket, and its function is to support the variable-diameter circular tube unit. The structure of the guide rail is a combination of rectangular and triangular guide rails, which can better ensure the coaxial accuracy of the supporting structure after assembly;

The outlet assemblies are respectively located at both ends of the variable-diameter circular pipe unit and connected to the overflow pipe and the tail pipe. The two ends of the overflow pipe and the tail pipe are respectively inserted into the outlet assemblies at the front and rear ends, and the outlets at the front and rear ends The components are all formed by connecting the outlet cavity and the outlet cover. The two ends of the overflow pipe and the tail pipe are sealed with the front and rear outlet components with PTEF lip seals; the overflow pipe passes through the outlet cover, and the overflow The flow tube rotates during the working process, while the outlet transparent cover is stationary, and the seal ring with the same specification as the PTEF lip seal ring is used to realize the rotating seal between the two; the front and rear end outlet components are connected to the guide rail through the outlet base plate; The bearing seat assembly is respectively installed on the overflow pipe, the tapered pipe and the tail pipe to play a supporting role; the inlet cavity assembly is installed at the entrance of the plexiglass reducer to accommodate the entrance of the plexiglass reducer , to connect the external pipeline and realize the function of dynamic and static separation between the inlet and the variable-diameter round pipe; the overflow pipe passes through the cover of the inlet cavity, and also uses a seal ring of the same specification as the PTEF lip seal ring to achieve rotary sealing; the inlet cavity assembly Connected to the guide rail through the entrance base plate;

There are T-shaped slots on the two drive shaft brackets, which are used to install the drive shaft bearing seat, and the lower end is installed with feet. The legs are installed on the drive shaft bracket by two upper and lower nuts; connected; the bearing seat assembly is installed on two drive shaft brackets to support the drive shaft; the overflow pipe, tapered pipe and tail pipe in the variable-diameter circular pipe unit are respectively installed on four on the bearing seat;

The power and transmission unit is responsible for providing power and transmitting the power to the variable-diameter circular tube unit; the power and transmission unit includes a motor, a first V-pulley and a second V-pulley, a transmission shaft, the same specification 2 second synchronous pulleys, 2 first synchronous pulleys of the same specification, and two synchronous belts; among them, the motor is installed on the ground through an adjustable motor mounting plate, and the torque of the motor shaft is passed by the second V-belt pulley The V-belt is transmitted to the first V-pulley. The first V-pulley is installed on the drive shaft. Its rotation makes the drive shaft rotate. The drive shaft drives the second synchronous pulley at both ends, and the second synchronous pulley drives the first synchronous belt through the synchronous belt. The synchronous pulley rotates, and the other end drives in the same form, thereby driving the entire variable-diameter circular tube unit to rotate; the transmission shaft is installed on the bracket through the bearing seat;

The refractive index compensation unit includes a water tank assembly, a water tank transparent cover and double-sided plexiglass plates; one side of the water tank assembly is a flange structure connected to the entrance cavity, and the other side of the water tank assembly has a stepped hole on the end surface for installing the water tank The flange of the transparent cover; the sink assembly is installed on the right side of the entrance through flange connection, the plexiglass reducer passes through from left to right, and two PTEF flanges are used at the flange positions of the large straight pipe section and the small tapered section of the plexiglass reducer pipe The lip-shaped sealing ring realizes the rotary dynamic seal; the upper part of the water tank assembly is an open structure, and the two sides of the water tank assembly are plexiglass plates, which are connected to the water tank assembly by bolts and gaskets, and the inside of the water tank assembly is used to be filled with experimental media; the refraction The rate compensation unit is mounted on the rail assembly with T-slot bolts.

The present invention has the following beneficial effects: in order to achieve the purpose of testing the flow field in the rotating variable-diameter circular tube, the device designs the variable-diameter circular tube part as plexiglass material, and reduces the variable diameter as much as possible under the condition of ensuring sufficient strength. The wall thickness of the circular tube can reduce the loss of light intensity and the influence of refraction, so as to meet the needs of LDV light transmission, and solve the problem of insufficient strength of the plexiglass variable-diameter circular tube under the condition of wall rotation; the added refractive index compensation unit is very good The problem of difficult compensation of the refraction index of the rotary variable-diameter circular tube is solved. In addition, the model under this device has good light transmission and strong visibility, and can observe the real flow state of the fluid in the variable diameter tube; in addition, this device is designed with a double synchronous belt drive structure, which is designed on both the front and rear rotating tubes of the plexiglass section. Driven by synchronous belts, two synchronous belts are driven by one shaft, which can minimize the torque on the variable-diameter circular tube made of plexiglass. In addition, the structure of the device separates the motor from the variable-diameter circular tube device, and uses a V-belt with a certain vibration-damping effect to drive between the two, so that the vibration generated by the equipment driving motor can be reduced. This device can be used to simulate the complex flow in which the common wall rotation and its own rotation are coupled in the industrial field, and can realize the laser velocity measurement research of its internal flow field, and test the helical flow in the variable-diameter circular tube under different wall rotation speeds and different flow rates. flow law.

Description of drawings:

Fig. 1 is a schematic cross-sectional view of the front view structure of the present invention.

Fig. 2 is a left side view of Fig. 1 .

Fig. 3 is a schematic diagram of the appearance structure of the present invention.

Fig. 4 is a partial sectional view of the appearance of the present invention.

Fig. 5 is an assembled assembly diagram of the variable-diameter circular tube unit of the present invention.

Fig. 6 is an assembly diagram of the refractive index compensation unit of the present invention.

Fig. 7 is a schematic structural view of the inlet cavity assembly of the present invention.

Fig. 8 is a schematic structural view of the motor base of the present invention.

In the figure 1-exit mouth; 2-exit through cover; 3-overflow pipe; 4-bearing seat; 5-self-aligning ball bearing; 6-first synchronous pulley; ;9-Overflow nozzle; 10-Tangential inlet plate; 11-Sink assembly; 12-Plexiglass reducing tube; 13-First PTFE lip seal ring; 14-Sink cover; 15-Taper tube; 16- Key; 17-shaft retaining ring; 18-connecting flange; 19-half ring; 20-tail pipe; 21-rail assembly; 22-second PTEF lip seal; ;25-drive shaft; 26-first V pulley; 27-second V pulley; 28-V belt; 29-synchronous belt; 30-second synchronous pulley; 31-bearing base; Plate; 33-inlet mouth base plate; 34-drive shaft bracket; 35-motor mounting plate; 36-plexiglass cover plate; 37-motor base plate; 38-foot.

detailed description:

The present invention will be further described below in conjunction with accompanying drawing:

As shown in Figure 1 to Figure 8, this kind of experimental device for testing the flow field in the rotating variable diameter circular tube is composed of four parts: the variable diameter circular tube unit, the support and connection unit, the power and transmission unit, and the refractive index compensation unit;

The function of the variable-diameter circular tube unit is to rotate the fluid, and it is composed of a circular tube-shaped inlet connected to multiple sections of straight tubes or variable-diameter tubes with different diameters; wherein, from left to right are overflow pipe 3, overflow pipe Nozzle 9, tangential inlet plate 10, plexiglass reducing pipe 12, tapered pipe 15 and tail pipe 20, the overflow pipe, overflow nozzle, tangential inlet plate, plexiglass reducing pipe, tapered pipe and tail pipe The pipes are connected by flanges and bolts, and the joints are matched to ensure the overall coaxiality requirements after assembly;

The overflow pipe is a pipe structure with a flange at one end, and the outer wall of the middle part of the pipe is provided with a keyway and a ring groove for installing the timing belt pulley, and the inner hole on one side of the flange is threaded for installing the overflow nozzle; The overflow nozzle is a pipe structure with an external thread at one end; the tangential inlet disk is a hollow disk-shaped flange structure, the inner diameter of which is equal to the inner diameter of the straight pipe section of the plexiglass reducing pipe 12, and one side of the disk is opened with Two tangential inlets, the flow channel form is a gradual cross section, which provides a channel for the liquid to enter the reducing tube and make it form a spiral flow; the plexiglass reducing tube is a plexiglass reducing tube with flanges at both ends Pipe structure, its sections with different diameters are divided into straight pipe section, large cone section and small cone section; The small tapered section of the diameter pipe 12 is the same, the inner hole at the rear of the tapered pipe is a straight hole, and the middle part of the outer wall of the tapered pipe is provided with a keyway and a ring groove for installing a timing belt pulley; the end of the tapered pipe is provided with a keyway, a half-ring groove and a sealing Ring installation groove, used to install detachable movable flange; the tail pipe is also a pipe structure with a flange at one end, and the flange end is used to connect with the tapered pipe flange, and its inner hole is a stepped hole structure, and the flange The inner hole of the end is slightly larger, which is matched with the tapered tube and the O-ring;

The function of the support and connection unit is to support the variable-diameter circular pipe unit, realize the dynamic and static separation and connect the pipeline; The bearing seat assembly constituted, the bearing seat base 31, the entrance cavity assembly formed by the entrance cavity 8 and the entrance cavity cover 7, the outlet component composed of the exit cavity 1 and the exit cover 2, the drive shaft support 34, the legs 39, and Outlet base plate 32 and entrance base plate 33; described guide rail assembly is made up of guide rail and drive shaft support 34, and its function is to support described variable-diameter round pipe unit, and the structure of described guide rail is the combination guide rail of rectangle and triangle, can Better guarantee the coaxial accuracy of the supporting structure after assembly;

The outlet assembly is respectively located at both ends of the variable-diameter circular pipe unit, and is connected with the overflow pipe 3 and the tail pipe 20. The two ends of the overflow pipe 3 and the tail pipe 20 are respectively inserted into the outlet assemblies at the front and rear ends. The outlet components at the rear end are all formed after the outlet cavity 1 is connected with the outlet transparent cover 2, and the two ends of the overflow pipe 3 and the tail pipe 20 are sealed with the front and rear outlet components with PTEF lip seals 22; The flow tube 3 passes through the outlet cover 2, the overflow tube 3 rotates during the working process, and the outlet cover 2 is stationary, and the sealing ring with the same specification as the PTEF lip seal ring 22 is used to realize the rotary seal between the two; The front and rear outlet components are connected to the guide rail 21 through the outlet base plate 32; the bearing housing components are respectively installed on the overflow pipe 3, the cone pipe 15 and the tail pipe 20 to play a supporting role; the inlet cavity components are installed At the entrance position of the plexiglass reducing tube 12, it plays the function of accommodating the entrance of the plexiglass reducing tube 12, connecting the external pipeline and realizing the dynamic and static separation of the inlet and the reducing tube; the overflow pipe 3 is passed through the entrance cavity cover 7 , using a sealing ring with the same specifications as the PTEF lip sealing ring to achieve rotary sealing; the inlet cavity assembly is connected to the guide rail 21 through the inlet base plate 33;

There are T-shaped slots on the two drive shaft brackets 34, which are used to install the drive shaft bearing housing 4. The lower end is equipped with a leg 38. The leg 38 is installed on the drive shaft bracket 34 by two upper and lower nuts; the drive shaft bracket 34 passes through the T-shaped slot. And the spiral is connected to the side of the guide rail 21; the bearing seat assembly is installed on two drive shaft brackets 34 to play the role of supporting the drive shaft 27; the overflow pipe 3 and the tapered pipe 15 in the variable diameter circular pipe unit Installed on four bearing housings 4 of the same specification as the tailpipe 20;

The power and transmission unit is responsible for providing power and transmitting the power to the variable-diameter circular tube unit; the power and transmission unit includes a motor 24, a first V-pulley 26 and a second V-pulley 27, and a transmission shaft 25 , 2 second synchronous pulleys 30 of the same specification, 2 first synchronous pulleys 6 of the same specification, two synchronous belts 29; wherein, the motor 24 is installed on the ground by an adjustable motor mounting plate 35, and the motor shaft The torque is transmitted from the second V-belt pulley 27 to the first V-belt pulley 26 through the V-belt 28. The first V-belt pulley 26 is installed on the driving shaft 25, and its rotation makes the driving shaft 25 rotate, and the driving shaft 25 drives the second V-pulley at both ends. Two synchronous pulleys 30, the second synchronous pulley 30 drives the first synchronous pulley 6 to rotate through the synchronous belt 29, and the other end drives the same form, thereby driving the rotation of the whole variable-diameter circular tube unit; the transmission shaft 25 is installed on the On the bracket 34;

The refractive index compensation unit includes a water tank assembly 11, a water tank transparent cover 14, and a double-sided organic glass plate 36; one side of the water tank assembly 11 is a flange structure connected to the entrance cavity, and the other side of the water tank assembly 11 has a stepped hole on the end surface , used to install the flange of the water tank cover 14; the water tank assembly 11 is installed on the right side of the entrance cavity 8 through flange connection, and the plexiglass reducing tube 12 passes through from left to right, at the large diameter of the plexiglass reducing tube 12 Two PTEF lip seal rings 13 are used for the flange position of the pipe section and the small cone section to realize rotary dynamic sealing; the upper part of the water tank assembly 11 is an open structure, and the two sides of the water tank assembly 11 are plexiglass plates 36, which are connected to the water tank assembly 11 by bolts and gaskets Above, the inside of the water tank assembly 11 is used to be filled with the experimental medium; the refractive index compensation unit is installed on the guide rail assembly 21 through T-slot bolts.

When in use, first turn on the liquid supply pump, the experimental medium flows from the inlet of the experimental device into the inlet cavity, and after filling the inlet cavity, flows into the variable diameter circular tube from the bilateral tangential inlets of the variable diameter circular tube to form a spiral flow. After the whole device is filled with the experimental medium, the driving motor of the experimental device is turned on, and the variable-diameter circular tube rotates under its drive, and the flow law of the fluid in the tube also changes accordingly. The flow rate of the liquid supply pump and the speed of the drive motor are respectively adjusted by the frequency conversion device. There is a certain degree of mutual influence between the flow rate and the speed, so it needs to be adjusted synchronously. Similar to the hydrocyclone, the variable-diameter circular tube device is designed with outlets in two directions, also known as the overflow port and the underflow port. By adjusting the valve, different distribution relationships between the two liquids can be obtained between the outlets. After the flow rate and rotational speed meet the experimental requirements stably, a suitable section is selected, and the laser Doppler velocimetry device is used to test and study the fluid flow law in the variable-diameter circular tube. The frequency conversion device is used to control the motor to generate different speeds to achieve different wall speeds of the variable-diameter circular tubes. The flow field in the transparent pipe segment variable-diameter circular tubes can be tested by laser velocimetry methods such as laser Doppler velocimeters and particle image velocimeters.

Claims (1)

1. An experimental device for testing the flow field in a rotating variable-diameter circular tube, which consists of four parts: a variable-diameter circular tube unit, a support and connection unit, a power and transmission unit, and a refractive index compensation unit; The function of the variable-diameter circular tube unit is to rotate the fluid, and it is composed of a circular tube-shaped inlet connected to multiple straight tubes or variable-diameter tubes with different diameters; among them, from left to right are overflow tubes (3) , overflow nozzle (9), tangential inlet plate (10), plexiglass reducing pipe (12), tapered pipe (15) and tailpipe (20), the overflow pipe, overflow nozzle, tangential inlet Flanges and bolts are used to connect the disk, plexiglass reducer, cone and tailpipe, and the joints are matched to ensure the overall coaxiality requirements after assembly; The overflow pipe is a pipe structure with a flange at one end, and the outer wall of the middle part of the pipe is provided with a keyway and a ring groove for installing the timing belt pulley, and the inner hole on one side of the flange is threaded for installing the overflow nozzle; The overflow nozzle is a pipe structure with an external thread at one end; the tangential inlet disk is a hollow disk-shaped flange structure, and its inner diameter is equal to the inner diameter of the straight pipe section of the plexiglass reducing pipe (12), and one side of the disk is There are two tangential inlets, and the form of the flow channel is a gradual cross section, which provides a channel for the liquid to enter the variable-diameter circular tube and make it form a spiral flow; the plexiglass variable-diameter tube is made of plexiglass with flanges at both ends The variable diameter pipe structure, its different diameter sections are divided into straight pipe section, large cone section and small cone section; the tapered pipe is a pipe structure with a flange at one end, and the inner hole on the side of the flange is a tapered hole. The small tapered section of the glass reducer (12) is the same, the inner hole at the rear of the tapered pipe is a straight hole, and the middle part of the outer wall of the tapered pipe is provided with a keyway and a ring groove for installing a synchronous pulley; the end of the tapered pipe is provided with a keyway, a half The ring groove and the sealing ring installation groove are used to install the detachable movable flange; the tail pipe is also a pipe structure with a flange at one end, and the flange end is used to connect with the tapered pipe flange, and its inner hole is a stepped hole Structure, the inner hole of the flange end is slightly larger, and cooperates with the tapered tube and the O-ring; The function of the support and connection unit is to support the variable-diameter circular pipe unit, realize the separation of movement and static, and connect the pipeline; the support and connection unit includes a support seat and a guide rail assembly (21), which consists of a bearing seat (4), a bearing The bearing seat assembly composed of the seat base (31) and the self-aligning ball bearing (5), the entrance chamber assembly composed of the entrance chamber (8) and the entrance passage cover (7), and the exit chamber (1) and the exit passage cover ( 2) The outlet assembly consists of the drive shaft bracket (34), the feet (39), and the outlet base plate (32) and the inlet base plate (33); the guide rail assembly is composed of the guide rail and the drive shaft bracket (34). The role is to support the variable-diameter circular tube unit, and the structure of the guide rail is a combination of rectangular and triangular guide rails, which can better ensure the coaxial accuracy of the supporting structure after assembly; The outlet components are respectively located at both ends of the variable-diameter circular pipe unit, connected with the overflow pipe (3) and the tail pipe (20), and the two ends of the overflow pipe (3) and the tail pipe (20) are respectively inserted into the front and rear In the outlet assembly at the end, the outlet assembly at the front and rear ends are formed by connecting the outlet cavity (1) and the outlet cover (2), and the two ends of the overflow pipe (3) and the tail pipe (20) are connected with the front , The rear outlet components are sealed with PTEF lip seals (22); the overflow pipe (3) passes through the outlet cover (2), and the overflow pipe (3) rotates during the working process, while the outlet cover ( 2) Static, the seal ring with the same specifications as the PTEF lip seal ring (22) is used to realize the rotary seal between the two; the front and rear outlet components are connected to the guide rail (21) through the outlet base plate (32); the Bearing seat components are respectively installed on the overflow pipe (3), tapered pipe (15) and tail pipe (20) to play a supporting role; the inlet cavity assembly is installed at the inlet position of the plexiglass reducing pipe (12) , to accommodate the inlet of the plexiglass variable diameter tube (12), connect the external pipeline and realize the function of separating the inlet from the variable diameter circular tube; A sealing ring of the same specification as the PTEF lip sealing ring realizes a rotary seal; the inlet cavity assembly is connected to the guide rail (21) through the inlet base plate (33); There are T-shaped slots on the two drive shaft brackets (34), which are used to install the drive shaft bearing seat (4), and the lower end is equipped with a leg (38). The leg (38) is installed on the drive shaft bracket (34) by two upper and lower nuts. Above; the drive shaft bracket (34) is connected to the side of the guide rail (21) through a T-shaped groove and a screw; the bearing seat assembly is installed on two drive shaft brackets (34) to support the drive shaft (27) ; The overflow pipe (3), tapered pipe (15) and tailpipe (20) in the variable-diameter circular pipe unit are respectively installed on four bearing seats (4) of the same specification; The power and transmission unit is responsible for providing power and transmitting the power to the variable-diameter circular tube unit; the power and transmission unit includes a motor (24), a first V-pulley (26) and a second V-pulley ( 27), transmission shaft (25), 2 second synchronous pulleys (30) of the same specification, 2 first synchronous pulleys (6) of the same specification, two synchronous belts (29); among them, the motor (24 ) is installed on the ground through an adjustable motor mounting plate (35), the torque of the motor shaft is transmitted from the second V-belt pulley (27) to the first V-belt pulley (26) through the V-belt (28), and the first V-belt The wheel (26) is installed on the drive shaft (25), and its rotation makes the drive shaft (25) rotate, and the drive shaft (25) drives the second synchronous pulley (30) at both ends, and the second synchronous pulley (30) passes through the synchronous The belt (29) drives the first synchronous pulley (6) to rotate, and the other end drives in the same form, thereby driving the entire variable-diameter circular tube unit to rotate; the transmission shaft (25) is installed on the bracket (34) through the bearing seat (4); The refractive index compensation unit includes a water tank assembly (11), a water tank transparent cover (14) and a double-sided plexiglass plate (36); one side of the water tank assembly (11) is a flange structure connected to the inlet, and the water tank assembly ( The other side of 11) has a stepped hole on the end face, which is used to install the flange of the sink cover (14); the sink assembly (11) is installed on the right side of the entrance cavity (8) through flange connection, and the plexiglass reducing tube (12) ) from left to right, and two PTEF lip seals (13) are used at the flange positions of the large straight pipe section and the small tapered section of the plexiglass reducing pipe (12) to realize rotary dynamic sealing; the upper part of the water tank assembly (11) is an opening structure, the two sides of the water tank assembly (11) are plexiglass plates (36), which are connected to the water tank assembly (11) by bolts and gaskets, and the inside of the water tank assembly (11) is used to be filled with experimental media; the refractive index compensation The unit is mounted on the rail assembly (21) with T-slot bolts.