A device for measuring the extensional viscosity of low-viscosity solutions using a cross-microchannel

Abstract

The present invention proposes a device for measuring the tensile viscosity of a low-viscosity solution based on a cross microchannel, comprising a differential pressure sensor, an upper channel cover plate, a cross microchannel layer, a lower channel cover plate, a liquid adding valve, a liquid adding port, a bellows, a piezoelectric stack, a heating-cooling plate, a temperature controller, a flow shell, a thermocouple, a drain valve, and a programmable power supply. The present invention uses an improved cross microchannel to allow the fluid to enter through two opposite inlets and leave through a pair of outlets with opposite diameters. A stagnation point is formed at the exact center of the intersection area, and the fluid is stretched along the outlet axis in the vorticity and free shear flow, and the applied strain rate can be easily controlled by the macroscopic flow rate of the device; the tensile viscosity can be evaluated by measuring the overall pressure drop of the entire device. The present invention has a simple structure, is easy to process, and is economical and convenient. The present invention can change the size of the bellows and the size of the microchannel according to the actual task requirements to achieve a wider range of application conditions.

Description

Technical Field

[0001] The invention belongs to the field of rheological measurement, and in particular relates to a device for measuring the stretching viscosity of a low-viscosity solution based on a cross microchannel. Background Art

[0002] As a rheological parameter that characterizes the tensile properties of materials, there are four main problems in measuring tensile viscosity in fluids: First, it is difficult to ensure that the fluid undergoes pure tensile deformation in the experiment. The ideal pure tensile deformation is described by the deformation rate tensor, which has only non-zero elements on its diagonal and is shear-free and vorticity-free. The deformation of the liquid always appears as a mixture of shear contribution and stretching contribution. To obtain the contribution of stretching in the liquid deformation, it is necessary to separate the two contributions in some form or to correct the contribution of shear stress. Secondly, viscoelastic fluids are prone to unstable flow because the deformation and elastic stress in stretching flow are usually much larger than those in shear flow, and the impact of the instability of viscoelastic fluids will be more obvious. Next is the dependence of strain rate on accumulated strain. Many studies have reported instantaneous stretching viscosity, but to observe steady-state stretching viscosity, continuous stretching flow is required, that is, the applied strain rate must be maintained for a long enough time so that the microstructure strain reaches saturation at this rate. Finally, due to the lack of a consistent and reliable method to interpret different experiments, many studies on polymer liquids have shown that it is difficult to obtain consistent stretching flow characteristics. Even when using different techniques to measure the stretching viscosity of a single model fluid, the results can differ by orders of magnitude.

[0003] At present, most rheometers or other stretching viscosity measurement methods or instruments are more suitable for measuring high viscosity fluids, such as polymer melts. Low viscosity fluids cannot be made into uniform material sheets or rods, and their stretching viscosity is difficult to obtain by conventional means. Microfluidics has been considered to have great potential in testing the tensile properties of low viscosity and low elasticity fluids. In macroscopic flows, the elastic coefficient may be small, but it is very large at the microscopic scale and may not be masked by the flow inertia. This means that microfluidic devices can achieve high deformation rates (i.e., high Weissenberg numbers Wi) while minimizing inertia. Summary of the invention

[0004] In view of this, in order to solve the technical problems mentioned in the above background technology, the present invention proposes a device for measuring the extension viscosity of a low-viscosity solution based on a cross microchannel, using mutually bisecting orthogonal rectangular microchannels to allow the fluid to enter through two relative inlets and leave through a pair of diametrically opposite outlets. A stagnation point is formed at the center of the intersection area, and the fluid is stretched in the vorticity and free shear flow along the outlet axis. The flow near the stagnation point is similar to a pure plane elongation flow, and the flow along the symmetry axis is shear-free and vortex-free, and a higher fluid strain can be achieved. The applied strain rate can be controlled by controlling the microchannel size and the liquid flow rate; the extension viscosity can be evaluated by measuring the overall pressure drop of the entire device.

[0005] To achieve the above object, the present invention adopts the following technical scheme: a device for measuring the tensile viscosity of a low-viscosity solution based on a cross microchannel, comprising a pressure testing part, a cross channel part, a shell part and a temperature control part, wherein the pressure testing part, the cross channel part, the shell part and the temperature control part are arranged in sequence from top to bottom;

[0006] The pressure test part includes a differential pressure sensor; the cross channel part includes a channel upper cover plate, a cross microchannel layer and a channel lower cover plate; the shell part includes a flow shell, four liquid adding valves, four liquid adding ports, four bellows, four piezoelectric stacks, four liquid drain valves and four programmable power supplies, the flow shell is provided with four liquid adding ports, each liquid adding port is equipped with a liquid adding valve, four bellows are installed around the flow shell, each bellows is connected to the piezoelectric stack and the programmable power supply in turn, and liquid drain valves are installed around the flow shell; the temperature control part includes a heating-cooling plate, a temperature controller and a thermocouple;

[0007] The two ends of the differential pressure sensor are connected to the two holes of the upper cover plate of the channel, the upper cover plate of the channel covers the cross microchannel layer, the cross microchannel layer correspondingly covers the lower cover plate of the channel, the four holes on the lower cover plate of the channel correspondingly cover the flow shell, the flow shell is placed on the heating-cooling plate, one end of the thermocouple is inserted into the flow shell, and the other end is connected to the temperature controller, and the temperature controller is connected to the heating-cooling plate.

[0008] Furthermore, the flow shell is made of stainless steel metal through integrated processing.

[0009] Furthermore, the flow shell is divided into four mutually unconnected areas A1, A2, B1, and B2, each area is connected to a corresponding test hole of the bellows and a drain hole of the drain valve, and each area on the upper surface is correspondingly connected to a liquid filling port.

[0010] Furthermore, the cross microchannel layer is in a cross shape, each top end is provided with a No. 1 through hole, the channel lower cover plate is in a cross shape, each top end is provided with a No. 2 through hole, the No. 1 through hole corresponds to the No. 2 through hole, and four No. 3 through holes are provided on the flow shell, and the No. 2 through hole corresponds to the No. 3 through hole.

[0011] Furthermore, the thermocouple is connected to the flow shell by threads, and the channel upper cover plate and the cross microchannel layer, the cross microchannel layer and the channel lower cover plate, and the channel lower cover plate and the flow shell are all fixed by glue and threads.

[0012] Furthermore, the measured liquid flows out from a set of holes on the flow housing, flows into the microchannels of the cross microchannel layer through the holes on the channel lower cover plate, and flows out from another set of holes through the channel lower cover plate into the flow housing.

[0013] Furthermore, the diameter of the bellows is 2-15 mm.

[0014] Furthermore, the displacement of the piezoelectric stack is 20-80 um.

[0015] Furthermore, the thickness of the cross microchannel layer is 2-4 mm, and the width of the microchannel is 0.1-0.4 mm.

[0016] A test method using a device for measuring the extensional viscosity of a low-viscosity solution based on a cross microchannel, specifically comprising the following steps:

[0017] (1) Assembling a device for measuring the tensile viscosity of a low-viscosity solution based on a cross microchannel: placing a flow shell on a heating-cooling plate and fixing it through a slot, the channel upper cover plate and the cross microchannel layer, the cross microchannel layer and the channel lower cover plate, and the channel lower cover plate and the flow shell are all fixed by glue and threading, the thermocouple and the flow shell are connected by threading and connected to a temperature controller through wires, the temperature controller is connected to the heating-cooling plate through wires, the liquid filling valve and the liquid filling port are welded, the liquid filling port is welded to the flow shell, the bellows is connected to the side pipe of the flow shell, and the other end is connected to the piezoelectric stack;

[0018] (2) After the device components are assembled, the relative piezoelectric stacks are set as one group and adjusted to zero displacement, and the other group is adjusted to maximum displacement. The liquid filling valve is opened, and the sample liquid to be measured is added to the flow shell through the liquid filling port. After the sample liquid is filled, the liquid filling valve is closed, and the programmable power supply and temperature controller are turned on to start the measurement;

[0019] (3) Start the programmable power supply, the piezoelectric stack moves, and when the total pressure difference is measured, the liquid in the bellows corresponding to the A1 and A2 areas enters the A1 and A2 areas under the push of the corresponding piezoelectric stack, then flows out through the holes G1G2, flows into the microchannel of the cross microchannel layer through the holes F1F2 on the lower cover plate of the channel through the holes C1C2, flows out from another opposite set of holes D1D2, flows through the holes E1E2 on the lower cover plate of the channel through the holes H1H2 into the B1B2 area of ​​the flow shell, and enters the bellows under the extraction of the corresponding piezoelectric stack in the B1B2 area; after a period of time, when the displacement of the piezoelectric stack reaches the upper limit, the liquid in the bellows corresponding to the B1 and B2 areas enters the B1 and B2 areas under the push of the corresponding piezoelectric stack. , then flows out through holes H1H2, through holes E1E2 on the lower cover plate of the channel, through holes D1D2, into the microchannel of the cross microchannel layer, and flows out from another set of holes C1C2, through holes F1F2 on the lower cover plate of the channel, through holes G1G2, into the A1A2 region of the flow shell, and enters the bellows under the extraction of the corresponding piezoelectric stack in the A1A2 region, and waits for the displacement of the piezoelectric stack to reach the upper limit, and repeats this cycle to obtain sufficient data. During the experiment, the piezoelectric stack corresponding to A1A2 is extracted to move away from the center of the shell, and the piezoelectric stack corresponding to B1B2 is pushed toward the center of the flow shell, and vice versa. The displacements of the four piezoelectric stacks are equal at all times. The absolute value of the pressure difference at this time is recorded as the total pressure difference, and the flow rate at this time is recorded;

[0020] When measuring the pressure difference caused by shear, the piezoelectric stacks 3-5 corresponding to the A1B2 areas of the flow shell are kept fixed. The liquid in the bellows corresponding to the A2 area enters the two A2 areas under the push of the corresponding piezoelectric stacks, and then flows out through the hole G2, flows into the microchannel of the cross microchannel layer through the hole C2 through the hole F2 on the lower cover plate of the channel, and flows out from another opposite group of holes D2 through the E2 of the lower cover plate of the channel through the hole H2 into the B1 area of ​​the flow shell. Under the extraction of the corresponding piezoelectric stack in the B1 area, it enters the bellows. After a period of time, when the displacement of the piezoelectric stack reaches the upper limit, the liquid in the bellows corresponding to the B1 area enters the two B1 areas under the push of the corresponding piezoelectric stack. Then it flows out through hole H1, through hole E1 on the lower cover plate of the channel, through hole D1, into the microchannel of the cross microchannel layer, and flows out from another opposite set of holes C2, through hole F2 on the lower cover plate of the channel, through hole G2, into the A2 area of ​​the flow shell, and enters the bellows under the extraction of the piezoelectric stack corresponding to the A2 area, and waits for the displacement of the piezoelectric stack to reach the upper limit, and repeats this cycle to obtain sufficient data. During the experiment, the piezoelectric stack corresponding to A2 is extracted and the piezoelectric stack corresponding to B1 is pushed, and vice versa, and the displacements of the two piezoelectric stacks are equal at all times. The absolute value of the pressure difference at this time is recorded as the shear pressure difference, and the flow rate at this time is recorded. During the experiment, a temperature controller is used to control the temperature in the flow shell;

[0021] (4) After the test, open the drain valve to drain the sample liquid, clean the flow shell, and analyze the collected data to eliminate invalid data. Record the differential pressure at different times recorded by the differential pressure sensor 1 and the displacement speed of the piezoelectric stack. Combined with the tensile viscosity under different temperature conditions, the specific calculation method is as follows:

[0022]

[0023] Among them, ΔP 总 (U) is the total pressure difference when the speed is U, ΔP 剪切 (U) is the pressure difference caused by shear only when the velocity is U, U is the flow velocity in the microchannel; W is the width of the microchannel, η E is the extensional viscosity at the corresponding strain rate, where the strain rate

[0024] Compared with the prior art, the beneficial effects of the device for measuring the elongation viscosity of low-viscosity solutions based on a cross microchannel described in the present invention are:

[0025] (1) The present invention proposes a device for measuring the extensional viscosity of low-viscosity solutions based on a "cross" microchannel, using mutually bisecting orthogonal rectangular microchannels to allow the fluid to enter through two opposite inlets and leave through a pair of diametrically opposite outlets. The flow field is symmetrical, a stagnation point is formed at the exact center of the intersection area, and the fluid is stretched along the outlet axis in vorticity and free shear flow. The macroscopic flow rate through the device is easily controlled by the applied strain rate; the extensional viscosity can be evaluated by measuring the overall pressure drop of the entire device.

[0026] (2) The device of the present invention is small in size, simple in structure, and easy to manufacture. A small amount of sample liquid can be used to measure the elongational viscosity. During the measurement process, different temperatures can be controlled to obtain the elongational viscosity at the corresponding temperature.

[0027] (3) The measuring part of the present invention is sealed, and the tensile viscosity of high-temperature solutions can be measured. In macroscopic flow, the elastic coefficient may be very small, but it is very large on the microscopic scale and may not be masked by the flow inertia. This means that the microchannel can achieve a high deformation rate (i.e., a high Weissenberg number Wi) while minimizing inertia. The device of the present invention can be used to measure the tensile viscosity of low-viscosity and low-elasticity fluids.

[0028] (4) The present invention has a simple structure, is easy to process, is economical and convenient, and can change the size of the bellows and the size of the microchannel according to actual task requirements to achieve a wider range of application conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0030] Figure 1 This is a schematic diagram of the assembly of the main accessories of the present invention;

[0031] Figure 2 It is a top view of the assembly of the main accessories of the present invention;

[0032] Figure 3 It is a diagram of the cross microchannel structure;

[0033] Figure 4 Schematic diagram of the upper cover structure;

[0034] Figure 5 is the cross-sectional view of the flow shell;

[0035] Figure 6 It is a top view of the flow shell;

[0036] Figure 7 This is an enlarged view of the center of the microchannel;

[0037] In the figure: differential pressure sensor 1; channel upper cover plate 2-1, cross microchannel layer 2-2, channel lower cover plate 2-3; flow shell 3-1, liquid adding valve 3-2, liquid adding port 3-3, bellows 3-4, piezoelectric stack 3-5, drain valve 3-6, programmable power supply 3-7, heating-cooling plate 4-1, temperature controller 4-2, thermocouple 4-3. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely explain the technical solutions in the embodiments of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict, and the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0039] See also Figure 1-Figure 7The present embodiment is described as a device for measuring the tensile viscosity of a low-viscosity solution based on a cross microchannel, which mainly includes four parts: a pressure test part, a cross channel part, a shell part, and a temperature control part; the pressure test part includes a differential pressure sensor 1; the cross channel part includes a channel upper cover plate 2-1, a cross microchannel layer 2-2 and a channel lower cover plate 2-3; the shell part includes a flow shell 3-1, four liquid adding valves 3-2, four liquid adding ports 3-3, four bellows 3-4, and four piezoelectric stacks 3-3. -5, four drain valves 3-6 and four programmable power supplies 3-7, the flow housing 3-1 is provided with four liquid filling ports 3-3, each liquid filling port 3-3 is installed with a liquid filling valve 3-2, four bellows 3-4 are installed around the flow housing 3-1, each bellows 3-4 is connected to the piezoelectric stack 3-5 and the programmable power supply 3-7 in sequence, and drain valves 3-6 are installed around the flow housing 3-1; the temperature control part includes a heating-cooling plate 4-1, a temperature controller 4-2 and a thermocouple 4-3;

[0040] The two ends of the differential pressure sensor 1 are connected to the two holes of the channel upper cover 2-1, the channel upper cover 2-1 covers the cross microchannel layer 2-2, the cross microchannel layer 2-2 is correspondingly covered on the channel lower cover 2-3, the four holes on the channel lower cover 2-3 are correspondingly covered on the flow shell 3-1, the flow shell 3-1 is placed on the heating-cooling plate 4-1, one end of the thermocouple 4-3 is inserted into the flow shell 3-1, and the other end is connected to the temperature controller, and the temperature controller is connected to the heating-cooling plate 4-1.

[0041] like Figure 3 and Figure 4 As shown, the measuring end of the differential pressure sensor 1 is connected to the pressure measuring hole of the channel upper cover plate 2-1, the channel upper cover plate 2-1 covers the cross microchannel layer 2-2, the holes C1C2D1D1 of the cross microchannel layer 2-2 correspond to the holes F1F2E1E2 of the channel lower cover plate 2-3 covered on the channel lower cover plate 2-3, and the four holes F1F2E1E2 on the channel lower cover plate 2-3 correspond to the holes G1G2H1H2 of the flow shell 3-1 covered on the flow shell 3-1. The liquid filling port 3-3 is respectively located in the four areas A1A2B1B2 of the flow shell 3-1, and is connected to the liquid filling valve 3-2. The liquid filling port 3-3 is also the exhaust port of the device.

[0042] like Figure 5 , Figure 6 As shown, the flow shell 11 in the present invention is made of stainless steel metal integrated processing, and the flow shell 3-1 is divided into four areas A1, A2, B1, and B2 that are not connected to each other. Each area is connected to the corresponding test hole of the bellows 3-4 and the drain hole of the drain valve 3-6, and each area on the upper surface is correspondingly connected to the liquid filling port 3-2.

[0043] In the present invention, the rectangular microchannels bisecting each other orthogonally in the cross microchannel layer 2-2 need a larger aspect ratio to ensure the uniformity of the strain rate in the vertical direction, such as Figure 7 As shown, in order to be closer to the theoretical stagnation point at the center, the rectangular microchannel is set to a hyperbolic structure near the center, and a square frame appears at the center.

[0044] The thermocouple 4-3 and the flow shell 3-1 are connected by threads, and the channel upper cover plate 2-1 and the cross microchannel layer 2-2, the cross microchannel layer 2-2 and the channel lower cover plate 2-3, and the channel lower cover plate 2-3 and the flow shell 3-1 are all fixed by glue and threads.

[0045] When testing the total pressure difference, the measured liquid flows out of the flow shell 3-1 from the holes G1G2 on the upper surface of the flow shell 3-1, flows into the microchannel of the cross microchannel layer 2-2 through the holes on the channel lower cover plate 2-3, flows out from the holes H1H2, passes through the channel lower cover plate 2-3 and flows into the flow shell 3-1. When measuring the pressure difference caused by shear, the measured liquid flows out of the flow shell 3-1 from the upper surface G2 of the flow shell 3-1, flows into the microchannel of the cross microchannel layer 2-2 through the holes on the channel lower cover plate 2-3, and flows out from the hole H1, passes through the channel lower cover plate 2-3 and flows into the flow shell 3-1.

[0046] The diameter of the bellows 7 is 2-15 mm.

[0047] The thickness of the cross microchannel layer 2-2 is 2-4 mm, and the width of the microchannel is 0.1-0.4 mm.

[0048] The displacement of the piezoelectric stack 3-5 is 20-80 um.

[0049] The test method using a device for measuring the elongational viscosity of a low-viscosity solution based on a cross microchannel specifically comprises the following steps:

[0050] (1) Assembling a device for measuring the tensile viscosity of a low-viscosity solution based on a cross microchannel: placing the flow shell 3-1 on the heating-cooling plate 4-1 and fixing it through a slot, the channel upper cover plate 2-1 and the cross microchannel layer 2-2, the cross microchannel layer 2-2 and the channel lower cover plate 2-3, and the channel lower cover plate 2-3 and the flow shell 3-1 are all fixed by glue and threads, the thermocouple 4-3 and the flow shell 3-1 are connected by threads and connected to the temperature controller 4-2 through wires, the temperature controller 4-2 is connected to the heating-cooling plate 4-1 through wires, the liquid adding valve 3-2 and the liquid adding port 3-3 are welded, the liquid adding port 3-3 is welded to the flow shell 3-1, the bellows 3-4 is connected to the side pipe of the flow shell 3-1, and the other end is connected to the piezoelectric stack 3-5;

[0051] (2) After the device components are assembled, the relative piezoelectric stacks 3-5 are set as one group and adjusted to zero displacement, and the other group is adjusted to maximum displacement. The liquid filling valve 3-2 is opened, and the sample liquid to be measured is added to the flow shell 3-1 through the liquid filling port 3-3. After the sample liquid is full, the liquid filling valve 3-2 is closed, and the programmable power supply 3-7 and the temperature controller 4-2 are turned on to start the measurement;

[0052] (3) Start the programmable power supply, the piezoelectric stack 3-5 moves, and when the total pressure difference is measured, the liquid in the bellows 3-4 corresponding to the A1 and A2 areas enters the A1 and A2 areas under the push of the corresponding piezoelectric stack 3-5, then flows out through the holes G1G2, flows into the microchannel of the cross microchannel layer 2-2 through the holes F1F2 on the channel lower cover plate 2-3 through the holes C1C2, flows out from another opposite group of holes D1D2 through the holes E1E2 on the channel lower cover plate 2-3 through the holes H1H2 into the B1B2 area of ​​the flow shell 3-1, and enters the bellows 3-4 under the extraction of the corresponding piezoelectric stack 3-5 in the B1B2 area; after a period of time, when the displacement of the piezoelectric stack 3-5 reaches the upper limit, the liquid in the bellows 3-4 corresponding to the B1 and B2 areas enters the B1 and B2 areas under the push of the corresponding piezoelectric stack 3-5. B2 two areas, then flow out through holes H1H2, through holes E1E2 on the channel lower cover plate 2-3, through holes D1D2 into the microchannel of the cross microchannel layer 2-2, and flow out from another opposite set of holes C1C2 through holes F1F2 on the channel lower cover plate 2-3, through holes G1G2 into the A1A2 area of ​​the flow shell 3-1, and enter the bellows 3-4 under the extraction of the piezoelectric stack 3-5 corresponding to the A1A2 area, and wait until the displacement of the piezoelectric stack 3-5 reaches the upper limit, and repeat this cycle to obtain sufficient data. During the experiment, the piezoelectric stack corresponding to A1A2 is extracted to move away from the center of the shell, and the piezoelectric stack corresponding to B1B2 is pushed to move toward the center of the flow shell, and vice versa. The displacements of the four piezoelectric stacks 3-5 are equal at all times. The absolute value of the pressure difference at this time is recorded as the total pressure difference, and the flow rate at this time is recorded;

[0053] When measuring the pressure difference caused by shear, the piezoelectric stack 3-5 corresponding to the A1B2 area of ​​the flow shell 3-1 is kept fixed. The liquid in the bellows 3-4 corresponding to the A2 area enters the two A2 areas under the push of the corresponding piezoelectric stack 3-5, and then flows out through the hole G2, flows into the microchannel of the cross microchannel layer 2-2 through the hole C2 through the hole F2 on the lower cover plate 2-3 of the channel, and flows out from another opposite group of holes D2 through the hole E2 of the lower cover plate 2-3 and into the B1 area of ​​the flow shell 3-1 through the hole H2. Under the extraction of the corresponding piezoelectric stack 3-5 in the B1 area, it enters the bellows 3-4. After a period of time, when the displacement of the piezoelectric stack 3-5 reaches the upper limit, the liquid in the bellows 3-4 corresponding to the B1 area enters the two B1 areas under the push of the corresponding piezoelectric stack 3-5. , then flows out through hole H1, flows into the microchannel of the cross microchannel layer 2-2 through hole E1 on the channel lower cover plate 2-3 through hole D1, flows out from another opposite group of holes C2 through hole F2 on the channel lower cover plate 2-3 through hole G2 into the A2 area of ​​the flow shell 3-1, enters the bellows 3-4 under the extraction of the piezoelectric stack 3-5 corresponding to the A2 area, and waits for the displacement of the piezoelectric stack 3-5 to reach the upper limit, and repeats this cycle to obtain sufficient data. During the experiment, the piezoelectric stack corresponding to A2 is extracted and the piezoelectric stack 3-5 corresponding to B1 is pushed, and vice versa, and the displacements of the two piezoelectric stacks 3-5 are equal at all times. The absolute value of the pressure difference at this time is recorded as the shear pressure difference, and the flow rate at this time is recorded. During the experiment, the temperature controller 4-2 is used to control the temperature in the flow shell 3-1;

[0054] (4) After the test, the drain valve 3-6 is opened to discharge the sample liquid to be tested. The test personnel clean the flow housing 3-1. The data analyst analyzes the collected data, removes invalid data, and records the differential pressure recorded by the differential pressure sensor 1 at different times and the displacement speed of the piezoelectric stack 3-5. Combined with the tensile viscosity under different temperature conditions, the specific calculation method is as follows:

[0055]

[0056] Among them, ΔP 总 (U) is the total pressure difference when the speed is U, ΔP 剪切 (U) is the pressure difference caused by shear only when the velocity is U, U is the flow velocity in the microchannel; W is the width of the microchannel, η E is the extensional viscosity at the corresponding strain rate, where the strain rate

[0057] The embodiments of the present invention disclosed above are only used to help illustrate the present invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. According to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well.

Claims

1. A device for measuring the extensional viscosity of a low-viscosity solution based on a cross microchannel, characterized in that: It includes a pressure testing part, a cross channel part, a shell part and a temperature control part, wherein the pressure testing part, the cross channel part, the shell part and the temperature control part are arranged in sequence from top to bottom; The pressure test part comprises a differential pressure sensor (1); the cross channel part comprises a channel upper cover plate (2-1), a cross microchannel layer (2-2) and a channel lower cover plate (2-3); the shell part comprises a flow shell (3-1), four liquid adding valves (3-2), four liquid adding ports (3-3), four bellows (3-4), four piezoelectric stacks (3-5), four liquid discharge valves (3-6) and four programmable power supplies (3-7); the flow shell (3-1) is provided with four liquid adding ports (3-3), each liquid adding port (3-3) is installed with a liquid adding valve (3-2); four bellows (3-4) are installed around the flow shell (3-1), each bellows (3-4) is connected in sequence to a piezoelectric stack (3-5) and a programmable power supply (3-7); and liquid discharge valves (3-6) are installed around the flow shell (3-1); The temperature control part comprises a heating-cooling plate (4-1), a temperature controller (4-2) and a thermocouple (4-3); two ends of the differential pressure sensor (1) are connected to two holes of the channel upper cover plate (2-1); the channel upper cover plate (2-1) covers the cross microchannel layer (2-2); the high-pressure and low-pressure ends of the differential pressure sensor (1) are respectively connected to two pressure measuring holes of the channel upper cover plate (2-1); the two pressure measuring holes respectively correspond to two mutually perpendicular channels of the cross microchannel layer (2-2); the cross microchannel layer (2-2) corresponds to covering the channel lower cover plate (2-3); the four holes on the channel lower cover plate (2-3) correspond to covering the flow shell (3-1); the flow shell (3-1) is placed on the heating-cooling plate (4-1); one end of the thermocouple (4-3) is inserted into the flow shell (3-1); the other end is connected to the temperature controller (4-2); the temperature controller (4-2) is connected to the heating-cooling plate (4-1); The flow housing (3-1) is divided into four mutually incommunicable areas, namely A1, A2, B1 and B2, each area being connected to a corresponding test hole of the bellows (3-4) and a drain hole of the drain valve (3-6), and each area on the upper surface being connected to a corresponding liquid filling port (3-3); The cross microchannel layer (2-2) is in a cross shape, and each top end is provided with a No. 1 through hole; the channel lower cover plate (2-3) is in a cross shape, and each top end is provided with a No. 2 through hole, and the No. 1 through hole corresponds to the No. 2 through hole; the flow housing (3-1) is provided with four No. 3 through holes, and the No. 2 through holes correspond to the No. 3 through holes; The four holes C1, C2, D1, and D2 of the cross microchannel layer (2-2) correspond to the four holes F1, F2, E1, and E2 of the lower cover plate (2-3) and cover the lower cover plate (2-3), and the four holes F1, F2, E1, and E2 on the lower cover plate (2-3) correspond to the four holes G1, G2, H1, and H2 of the flow shell (3-1) and cover the flow shell (3-1).

2. The device for measuring the elongational viscosity of a low-viscosity solution based on a cross microchannel according to claim 1, characterized in that: The flow casing (3-1) is made of stainless steel through integrated processing.

3. The device for measuring the elongational viscosity of a low-viscosity solution based on a cross microchannel according to claim 1, characterized in that: The thermocouple (4-3) and the flow housing (3-1) are connected by threads, and the channel upper cover plate (2-1) and the cross microchannel layer (2-2), the cross microchannel layer (2-2) and the channel lower cover plate (2-3), and the channel lower cover plate (2-3) and the flow housing (3-1) are all fixed by glue and threads.

4. The device for measuring the elongational viscosity of a low-viscosity solution based on a cross microchannel according to claim 1, characterized in that: When testing the total pressure difference, the measured liquid flows out of the flow shell (3-1) from the holes G1 and G2 on the upper surface of the flow shell (3-1), flows into the microchannel of the cross microchannel layer (2-2) through the holes on the lower channel cover plate (2-3), flows out from the holes H1 and H2, passes through the lower channel cover plate (2-3), and flows into the flow shell (3-1). When measuring the pressure difference caused by shear, the measured liquid flows out of the flow shell (3-1) from the upper surface G2 of the flow shell (3-1), flows into the microchannel of the cross microchannel layer (2-2) through the holes on the lower channel cover plate (2-3), and flows out from the hole H1, passes through the lower channel cover plate (2-3), and flows into the flow shell (3-1).

5. The device for measuring the extensional viscosity of a low-viscosity solution based on a cross microchannel according to claim 1, characterized in that: The diameter of the bellows (3-4) is 2-15 mm.

6. The device for measuring the elongational viscosity of a low-viscosity solution based on a cross microchannel according to claim 1, characterized in that: The displacement of the piezoelectric stack (3-5) is 20-80 um.

7. The device for measuring the extensional viscosity of a low-viscosity solution based on a cross microchannel according to claim 1, characterized in that: The thickness of the cross microchannel layer (2-2) is 2-4 mm, and the width of the microchannel is 0.1-0.4 mm.

8. A test method using a device for measuring the elongational viscosity of a low-viscosity solution based on a cross microchannel as claimed in any one of claims 1 to 7, characterized in that: The specific steps include: (1) Assembling a device for measuring the tensile viscosity of a low-viscosity solution based on a cross microchannel: placing a flow shell (3-1) on a heating-cooling plate (4-1) and fixing it through a slot; the channel upper cover plate (2-1) and the cross microchannel layer (2-2), the cross microchannel layer (2-2) and the channel lower cover plate (2-3), and the channel lower cover plate (2-3) and the flow shell (3-1) are all fixed by glue and threads; the thermocouple (4-3) and the flow shell (3-1) are connected by threads and connected to a temperature controller (4-2) through wires; the temperature controller (4-2) is connected to the heating-cooling plate (4-1) through wires; the liquid filling valve (3-2) and the liquid filling port (3-3) are welded; the liquid filling port (3-3) is welded to the flow shell (3-1); the bellows (3-4) is connected to the side pipe of the flow shell (3-1), and the other end is connected to a piezoelectric stack (3-5); (2) After the device components are assembled, the relative piezoelectric stacks (3-5) are set as one group and adjusted to zero displacement, and the other group is adjusted to maximum displacement. The liquid filling valve (3-2) is opened, and the sample liquid to be measured is added into the flow shell (3-1) through the liquid filling port (3-3). After the sample liquid is filled, the liquid filling valve (3-2) is closed, and the programmable power supply (3-7) and the temperature controller (4-2) are turned on to start the measurement; (3) The programmable power supply is started, and the piezoelectric stack (3-5) moves. When the total pressure difference is measured, the liquid in the bellows (3-4) corresponding to the A1 and A2 regions enters the A1 and A2 regions under the push of the corresponding piezoelectric stack (3-5), and then flows out through holes G1 and G2, through holes F1 and F2 on the channel lower cover (2-3), and then flows into the microchannel of the cross microchannel layer (2-2) through holes C1 and C2, and then flows out from another set of holes D1 opposite to the liquid. , D2 flows out through holes E1 and E2 of the lower cover plate (2-3) of the channel, and flows into the B1 and B2 regions of the flow shell (3-1) through holes H1 and H2, and enters the bellows (3-4) under the extraction of the corresponding piezoelectric stacks (3-5) in the B1 and B2 regions; after a period of time, when the displacement of the piezoelectric stacks (3-5) reaches the upper limit, the liquid in the bellows (3-4) corresponding to the B1 and B2 regions enters under the push of the corresponding piezoelectric stacks (3-5). The piezoelectric stack (3-5) corresponding to the A1 and A2 regions enters the bellows (3-4) when the piezoelectric stack (3-5) reaches the upper limit. This cycle is repeated to obtain sufficient data. During the experiment, the piezoelectric stacks corresponding to A1 and A2 are pulled away from the center of the shell, and the piezoelectric stacks corresponding to B1 and B2 are pushed toward the center of the flow shell, and vice versa. The displacements of the four piezoelectric stacks (3-5) are equal at all times. The absolute value of the pressure difference at this time is recorded as the total pressure difference, and the flow rate at this time is recorded. When measuring the pressure difference caused by shear, the piezoelectric stacks (3-5) corresponding to the A1 and B2 regions of the flow shell (3-1) are kept fixed. The liquid in the bellows (3-4) corresponding to the A2 region enters the A2 region under the push of the corresponding piezoelectric stack (3-5), then flows out through the hole G2, flows into the microchannel of the cross microchannel layer (2-2) through the hole C2 through the hole F2 on the channel lower cover (2-3), flows out from another opposite set of holes D2 through the hole E2 of the channel lower cover (2-3) through the hole H2 into the B1 region of the flow shell (3-1), and enters the bellows (3-4) under the extraction of the piezoelectric stack (3-5) corresponding to the B1 region. After a period of time, when the displacement of the piezoelectric stack (3-5) reaches the upper limit, the liquid in the bellows (3-4) corresponding to the B1 region enters the B1 region under the push of the corresponding piezoelectric stack (3-5). domain, then flows out through hole H1, flows through hole E1 on the lower cover plate (2-3) of the channel through hole D1 into the microchannel of the cross microchannel layer (2-2), flows out from another opposite set of holes C2 through hole F2 on the lower cover plate (2-3) of the channel through hole G2 into the A2 region of the flow shell (3-1), enters the bellows (3-4) under the extraction of the piezoelectric stack (3-5) corresponding to the A2 region, and waits for the displacement of the piezoelectric stack (3-5) to reach the upper limit, and repeats this cycle to obtain sufficient data. During the experiment, when the piezoelectric stack corresponding to A2 is extracted, the piezoelectric stack (3-5) corresponding to B1 is pushed, and vice versa, and the displacements of the two piezoelectric stacks (3-5) are equal at the same time. The absolute value of the pressure difference at this time is recorded as the shear pressure difference, and the flow rate at this time is recorded. During the experiment, a temperature controller (4-2) is used to control the temperature in the flow shell (3-1); (4) After the test, the drain valve (3-6) is opened to discharge the sample liquid to be tested. The test personnel clean the flow shell (3-1). The data analyst analyzes the collected data, removes invalid data, and records the differential pressure recorded by the differential pressure sensor (1) at different times and the displacement speed of the piezoelectric stack (3-5). Combined with the tensile viscosity under different temperature conditions, the specific calculation method is as follows: in, is the total pressure difference when the velocity is U, is the pressure difference caused only by shear when the velocity is U, U is the flow velocity in the microchannel; W is the width of the microchannel, is the extensional viscosity at the corresponding strain rate, where the strain rate =0.2U / W.

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