CN106370559B - Using the experimental provision and experimental method of microflow control technique measurement fluid viscosity - Google Patents

Abstract

The invention belongs to the technical field of microfluidic chips, and in particular relates to an experimental device for measuring fluid viscosity using microfluidic technology. The sample device is connected to the microfluidic chip through a Teflon tube; the temperature control system is connected to the glass heating platform; the laser light source, the upright fluorescence microscope, and the digital camera are connected in sequence; the digital camera is located on the stage of the upright fluorescence microscope Above; the microfluidic chip is placed on a glass heating platform, and the glass heating platform is placed on an upright fluorescence microscope stage. The invention can obtain the quantitative change rule of the fluid viscosity in a relatively large temperature range. The method is simple and feasible, has high accuracy, wide measurement temperature range, and low cost, and is suitable for undergraduate teaching experiments related to fluid mechanics.

Description

Experimental device and experimental method for measuring fluid viscosity using microfluidic technology

technical field

The invention belongs to the technical field of microfluidic chips, and in particular relates to an experimental device and method for measuring fluid viscosity using microfluidic technology.

Background technique

(Engineering) Fluid Mechanics is one of the basic courses for undergraduates and postgraduates in engineering colleges. There are many experiments in the course of fluid mechanics, and the experimental equipment involved in fluid state discrimination and viscosity measurement is often bulky, low in precision, and difficult to maintain. The introduction of microfluidic chip technology can well solve the above problems.

Microfluidics, also known as Lab-on-a-chip, refers to the size of a chip built on a transparent carrier (such as glass, plastic, etc.) with a small area (about a few square centimeters). Precise chemistry or biology laboratory. It realizes the integration of routine functions in chemical or biological laboratories, and has the characteristics of high sensitivity, high precision, transparent visualization, and low cost. It is an emerging analysis and detection method. Foreign countries have introduced microfluidic technology into various fields such as chemistry, biology, medicine, and environment, and made it play an important role. my country's microfluidic chip technology started relatively late, but has developed rapidly. For example, Lin Bingcheng, Wang Liding, Fang Zhaolun and others have provided good theoretical guidance and practical significance for the application of microfluidic technology in my country.

In the field of petroleum engineering, there are many problems involving fluids. For example, the analysis of flow forms includes oil, gas and water seepage, pipe flow, annular flow, etc., and the flow states include laminar flow, turbulent flow, and slug flow. At present, the traditional teaching and research methods for these problems are very limited, time-consuming and material-consuming, and the precision is not high, while microfluidic technology provides new possibilities for the teaching and research of these problems.

Viscosity refers to the property of resisting deformation and hindering relative movement when fluid microgroups move relative to each other. It is a basic property of fluid. The dynamic viscosity μ reflects the true viscosity of the fluid, which is related to the type of fluid and temperature, and the influence of temperature on viscosity is more significant.

Therefore, understanding the influence of temperature on fluid viscosity is not only an application and supplement to the professional basic course of fluid mechanics, but also one of the important learning contents for majors such as petroleum engineering, offshore oil and gas engineering, and oil and gas gathering and transportation engineering. Mastering the relationship between temperature and fluid viscosity through this experimental system will provide strong support and help for understanding annular flow, seepage, and deepwater drilling fluid design.

Contents of the invention

The purpose of the present invention is to propose an experimental device and method for measuring fluid viscosity using microfluidic technology, so as to solve the problems of large volume, low precision and difficult maintenance of the current experimental equipment in fluid mechanics course experiments.

Experimental device for measuring fluid viscosity using microfluidic technology, including constant pressure pump, micro-injector, microfluidic chip, temperature control system, glass heating platform, laser light source, upright fluorescence microscope, digital camera, waste liquid collection system ; The described constant pressure pump, micro-injector, micro-fluidic chip, and waste liquid collection system are connected sequentially, and the described micro-injector is connected with the micro-fluidic chip through a Teflon tube; the described temperature control system It is connected with the glass heating platform; the laser light source, the upright fluorescence microscope, and the digital camera are connected in sequence; the digital camera is located above the stage of the upright fluorescence microscope; the microfluidic chip is placed on the glass heating platform, and the glass heating platform is placed on an upright fluorescence microscope stage.

Wherein, the main body layer of the microfluidic chip is a polydimethylsiloxane polymer material layer, and the bottom surface carrier is glass; the main layer of the microfluidic chip includes a channel configuration, and the channel configuration is a single straight channel , the width of a single straight channel is 450-470 μm, and the height is 40-50 μm. Preferably, the microchannel of the microfluidic chip has a width of 460.5 μm and a height of 44.2 μm.

Specifically, the selected temperature range of the temperature control system and the glass heating platform is 298K-348K.

Specifically, the relevant parameters of the digital camera are: aperture F3.2, ISO100, sensitivity 80, exposure time 1s.

The experimental method of the experimental device using microfluidic technology to measure fluid viscosity includes the following processes:

(1) Evenly disperse the fluorescent particles in the fluid sample to be tested, and suck the sample containing the fluorescent particles into the micro-injector;

(2) By adjusting the parameters of the constant pressure pump panel, inject the fluid sample into the microfluidic chip and maintain the injection state;

(3) Turn on the constant pressure pump to inject the sample into the microfluidic chip, make the sample fill the channel of the microfluidic chip and flow out a little, then suspend the injection;

(4) Choose a suitable microscope objective lens for the upright fluorescence microscope, and make the field of view under the eyepiece the middle section of the channel of the microfluidic chip;

(5) Adjust the focal length of the digital camera to focus on the channel of the microfluidic chip;

(6) Set the target temperature through the temperature control system, make the glass heating platform reach the set temperature, and let it stand for 10 minutes;

(7) Turn on the constant pressure pump to inject the sample into the microfluidic chip. After observing that the flow is stable, adjust and record the exposure time, and start taking pictures. The number of pictures is 10;

(8), measure the length of each trace in the photo, divide by the exposure time, obtain the fluid velocity distribution in the microfluidic chip pipeline;

(9) Bring the flow velocity distribution data and the pressure difference parameters into the N-S equation and the continuity equation to obtain the fluid viscosity at the temperature.

Wherein, the fluorescent particles described in step (1) have a particle diameter of 1 μm.

The fluid sample to be tested in step (1) includes deionized water, engine oil, and glycerin.

The present invention has following advantage and effect:

The invention can obtain the quantitative change rule of the fluid viscosity in a relatively large temperature range. The method is simple and feasible, has high accuracy, wide measurement temperature range, and low cost, and is suitable for undergraduate teaching experiments related to fluid mechanics.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a schematic structural diagram of the microfluidic chip of the present invention;

Fig. 3 is the comparison of the flow field distribution and simulation results of the 298K deionized water of the embodiment;

Fig. 4 is the comparison of the flow field distribution and simulation results of the embodiment engine oil at 298K and 348K;

Fig. 5 is the flow field distribution and simulation result comparison of embodiment glycerol under 298K and 348K;

Fig. 6 is a curve diagram of oil flow velocity distribution under different temperatures of the embodiment;

Fig. 7 is the curve diagram of glycerin flow velocity distribution under the different temperatures of embodiment;

Fig. 8 is a graph showing the variation of engine oil viscosity at different temperatures in the embodiment;

Fig. 9 is a graph showing the variation of glycerin viscosity at different temperatures in the embodiment.

Detailed ways

The specific implementation of the present invention will be described in conjunction with the examples.

As shown in Figure 1, the experimental device for measuring fluid viscosity using microfluidic technology includes a constant pressure pump 1, a micro-injector 2, a microfluidic chip 3, a temperature control system 4, a glass heating platform 5, a laser light source 6, An upright fluorescence microscope 7, a digital camera 8, and a waste liquid collection system 9; the constant pressure pump 1, micro-injector 2, microfluidic chip 3, and waste liquid collection system 9 are connected in sequence, and the micro-injection The device 2 is connected to the microfluidic chip 3 through a Teflon tube; the temperature control system 4 is connected to the glass heating platform 5; the laser light source 6, the upright fluorescence microscope 7, and the digital camera 8 are connected in sequence; placed above the stage of the fluorescence microscope 7; the microfluidic chip 3 is placed on the glass heating platform 5, and the glass heating platform 5 is placed on the stage of the upright fluorescence microscope 7.

As shown in Figure 2, the main body layer of the microfluidic chip 3 is a polydimethylsiloxane polymer material layer, and the bottom surface carrier is glass; the main layer of the microfluidic chip 3 includes a channel structure, and the channel structure The type is a single straight channel, the width of the single straight channel is 450-470 μm, and the height is 40-50 μm. Preferably, the microchannel of the microfluidic chip 3 has a width of 460.5 μm and a height of 44.2 μm.

Specifically, the selected temperature range of the temperature control system 4 and the glass heating platform 5 is 298K-348K.

Specifically, the relevant parameters of the digital camera 8 are: aperture F3.2, ISO100, sensitivity 80, exposure time 1s.

Embodiment 1: Feasibility of deionized water verification experiment

(1) In order to verify the feasibility of the experiment, at first the test is carried out for deionized water, and the fluorescent particle solution is directly used as the sample for the test, and an appropriate amount of the fluorescent particle solution is injected with the micro-injector 2, and then the micro-injector 2 is set at a constant temperature. Pressure pump 1, after setting the relevant parameters on the constant pressure pump 1 board, the sample can be injected;

(2) Turn on the constant pressure pump 1 to inject the sample into the microfluidic chip 3, fill the channel of the microfluidic chip 3 with the sample and flow out a little, then suspend the injection, and then start to adjust the upright fluorescence microscope 7 so that the field of view under the eyepiece is micro In the middle section of the 3 channels of the fluidic chip, and the size is appropriate, connect the digital camera 8 to the upright fluorescence microscope 7, and adjust the focal length;

(3) Set the temperature of the temperature control platform to 298K. After the temperature reaches the set temperature, turn on the constant pressure pump 1. After observing that the flow is stable, start taking pictures. The number of photos can be determined according to the actual effect, but should not be less than 5;

(4) After the photos are collected, use graphic analysis software for quantitative analysis, so as to obtain the flow field distribution of deionized water at a specific temperature and a specific flow rate, as shown in Figure 3.

It can be seen from Fig. 3 that the flow field distribution obtained by the analysis of fluorescent particle traces conforms to the parabolic form of the analytical solution of the circular tube laminar flow theory, and the flow velocity is the largest at the tube axis, and the actual flow field distribution basically agrees with the simulation results. The average flow velocity 74.84μm/s obtained from the fitting of the experimental results is consistent with the average flow velocity 75μm/s set by the experiment, and the calculated dynamic viscosity μ (0.8985cP) of the water is consistent with the values used in the look-up table and simulation. It means that the experimental plan is accurate and feasible.

Example 2: Flow Field Observation and Simulation Verification of Oil Phase

The oil phases used are machine oil and glycerin, respectively. The COMSOL Multiphysics simulation software is selected for verification.

After the surface of the fluorescent particles is treated with hydrophobicity, an oil phase is added to indicate its flow field distribution. The specific operation steps are the same as the observation of the water phase in Example 1, and the inlet pressure is controlled at 1.5 atmospheres. And after completing a group of observations, adjust the temperature of the temperature control system 4 to 348K, and repeat the measurement steps once the system is stable. The flow field distribution of engine oil and glycerin can be obtained as shown in Figure 4 and Figure 5.

It can be seen from Figure 4 that under the condition of constant pressure, the oil flow field can be measured through experimental observation. Through fitting, its dynamic viscosity is 574cP at 298K, and the dynamic viscosity decreases to 28cP when the temperature rises to 348K. It can be seen that the temperature has an effect on the dynamic viscosity. The effect is significant, and the experimental data of the two groups are consistent with the simulation curve;

From Figure 5, it can be seen that the dynamic viscosity of glycerin is 995cP at 298K and 24cP at 384K, and the two sets of experimental data are consistent with the simulation curve.

Comparing Figure 4 and Figure 5, the increase in temperature has played a role in reducing viscosity, and the fluid flow field is significantly different at different temperatures, and the fitted viscosity is consistent with the reference value, indicating that the experiment is accurate and effective in determining fluid viscosity, and can be quantitatively analyzed Effects of temperature and other factors on rheology.

Example 3: Effect of temperature on oil phase flow field and viscosity result fitting

Based on Example 2, the flow field distributions of the two oil products were simulated under more temperature conditions, and 5 of them were selected for illustration. The velocity distribution curves of engine oil at different temperatures are shown in Figure 6, and the velocity distribution curves of glycerin at different temperatures are shown in Figure 7. It can be seen that the velocity distribution curve of engine oil is obviously different from the peak-type laminar flow curve of glycerol, which is similar to the flat-type laminar flow curve. The flat laminar flow is beneficial for carrying cuttings and stabilizing the borehole wall, which meets the characteristics of engine oil and is also the characteristic required for drilling fluid.

Further comparison of the flow rate distribution diagrams of engine oil and glycerin shows that the viscosity of engine oil decreases continuously in the temperature range from 273K to 373K, while the viscosity of glycerin does not change significantly with the increase of temperature from 323K onwards.

By extracting the fluid viscosity at different temperatures through the circular tube laminar flow theory, the dynamic viscosity change curve can be obtained, as shown in Figure 8 and Figure 9. And using the Arrhenius formula for fitting, the results are shown in formulas (1) and (2) respectively.

μ＝4.75549×10 ^-10 e ^{51814.51426/(8.31451×T)} (1)

μ＝5.74611×10 ^-12 e ^{64116.38228/(8.31451×T)} (2)

In the formula: μ is the dynamic viscosity of the fluid, Pa·s; T is the temperature, K.

It can be seen from Figures 8 and 9 that the dynamic viscosities of both oils increase as the temperature decreases. Especially when it is lower than 300K, the viscosity of the fluid is greatly affected by the temperature, and the viscosity increases exponentially with the decrease of the temperature; when the temperature is higher, the influence on the viscosity of the fluid is not obvious. This also fully demonstrates that low temperature has a great influence on the rheological properties of fluids, and the regulation of low temperature rheological properties is one of the difficult problems that must be overcome in deepwater drilling fluids. Through this experiment, students can gain a deeper understanding of this problem from both practical and theoretical aspects; at the same time, this experimental system can also be used to design and verify the "constant rheological" drilling system.

Claims (5)

1. the experimental provision of application microflow control technique measurement fluid viscosity, it is characterised in that including constant pressure pump (1), micro-sampling Device (2), micro-fluidic chip (3), temperature control system (4), glass heating platform (5), laser light source (6), just put fluorescence microscope (7), digital camera (8), waste collection system (9)；The constant pressure pump (1), microsyringe (2), micro-fluidic chip (3), waste collection system (9) is sequentially connected, and the microsyringe (2) is connected by teflon pipe and micro-fluidic chip (3) Connect；The temperature control system (4) is connected with glass heating platform (5)；Laser light source (6), just putting fluorescence microscope (7), be digital Camera (8) is sequentially connected；Digital camera (8) is located above the objective table for just putting fluorescence microscope (7)；Described is micro-fluidic Chip (3) is placed on glass heating platform (5), and glass heating platform (5), which is positioned over, just puts fluorescence microscope (7) objective table On.

2. the experimental provision according to claim 1 using microflow control technique measurement fluid viscosity, it is characterised in that described The body layer of micro-fluidic chip (3) be dimethyl silicone polymer polymer material layer, bottom surface carrier is glass；Micro-fluidic chip (3) including channel configurations in body layer, channel configurations are single straight channel, and single straight-through road width is 450~470 μm, a height of 40~ 50μm。

3. the experimental method of the experimental provision according to claim 1 or 2 using microflow control technique measurement fluid viscosity, its It is characterized in that, including procedure below：

(1), fluorescent grain is uniformly dispersed in fluid to be measured sample, the sample containing fluorescent grain is sucked into micro-sampling Device (2)；

(2), by adjusting constant pressure pump (1) panel parameter, by fluid sample injection micro-fluidic chip (3) and injection state is kept；

(3), constant pressure pump (1) is opened to micro-fluidic chip (3) injected sample, sample is full of micro-fluidic chip (3) passage cocurrent After going out a little, pause injection；

(4), just putting fluorescence microscope (7) and choosing suitable micro objective, and making the visual field under eyepiece be micro-fluidic chip (3) Passage stage casing；

(5), adjustment digital camera (8) focal length is allowed to focus on micro-fluidic chip (3) passage；

(6), target temperature is set by temperature control system (4), glass heating platform (5) is reached design temperature, and stand 10 points Clock；

(7), constant pressure pump (1) is opened to micro-fluidic chip (3) injected sample, it was observed that after flowing is stablized, is adjusted and is recorded exposure Time, starts to take pictures, and number of pictures is 10；

(8), the length of each trace in photo, divided by time for exposure are measured, obtains the fluid flow rate in micro-fluidic chip (3) pipeline Distribution；

(9), velocity flow profile data and pressure difference parameter are brought into N-S equations and continuity equation, so as to obtain stream at this temperature Body viscosity.

4. the experimental method of the experimental provision according to claim 3 using microflow control technique measurement fluid viscosity, it is special Sign is that the fluorescent grain described in step (1), particle diameter is 1 μm.

5. the experimental method of the experimental provision according to claim 3 using microflow control technique measurement fluid viscosity, it is special Sign is that the fluid to be measured sample described in step (1) includes deionized water, machine oil, glycerine.