System for confining pressure and back pressure simultaneously realize high pressure in micro-fluidic chip
Technical Field
The invention belongs to the technical field of multiphase flow in primary subject power engineering and engineering thermophysics, and particularly relates to a simple system for simultaneously realizing high pressure, confining pressure and back pressure in a micro-fluidic chip in micro-scale flow.
Background
In recent years, microscopic multiphase flow in porous media has been a research hotspot in the fields of science and engineering. The microscopic visualization technology can really realize in-situ observation and direct recording of the flow process, and greatly promotes related research processes, but most of the micro-flow research occurs on micro-fluidic chips, and most of the chips cannot bear high pressure due to material properties and can not really realize flow measurement under actual working conditions.
The existing method for solving the problem mainly comprises two methods, one method is to add a clamp at the inlet and outlet ends of the microfluidic chip to prevent the port from bursting, but the problem cannot be solved fundamentally, the bearable pressure cannot be increased too much, the manufacturing cost is expensive, and the loss factor is strong due to the matched special chip; in another mode, the oil extraction confining pressure reaches the preset pressure, and the purpose of high pressure is realized through the internal and external pressure difference control of the microfluidic chip, but the previous patent research finds that the realization of the confining pressure is few, the Chinese patent specifications 2012101483096 and 2017113800102 mention the realization of the confining pressure, but the purpose of the confining pressure is mainly to realize the high pressure in the rock core through the confining pressure and is not suitable for fragile materials such as glass and PDMS, the high-pressure system proposed in the Chinese patent specification 2017107179868 is the most common confining pressure mode for realizing the high pressure at present, but the design of the confining pressure chamber is complex, a plurality of connecting parts exist, the pressure is easy to leak, the manufacturing cost is not high, and the mode for realizing the confining pressure is that the internal and external pressure difference of the microfluidic chip cannot be too large through the manual control, and the operability has certain difficulty. In addition, the system has no outlet when being used for filling oil or other fluids, and is far different from the actual oil production and gas production, namely a backpressure regulation part is lacked.
Disclosure of Invention
The invention aims to solve the technical problem of improving a high-pressure implementation method in a microfluidic chip, providing a simple system for simultaneously carrying out confining pressure and back pressure regulation, and reducing the manufacturing cost of equipment, thereby providing a high-temperature high-pressure working condition which is consistent with the actual condition for flow research on a micro scale.
The technical scheme of the invention is as follows:
a system for realizing high pressure in a microfluidic chip by carrying out confining pressure and back pressure simultaneously comprises a liquid containing container 1, a plunger pump 2, a valve 3, a gas cylinder 4, a pressure gauge 5, a middle piston container 6, a microfluidic chip 7, a sapphire confining pressure chamber 8 and a pipeline;
one end of the plunger pump 2 is communicated with the liquid containing container 1, and the other end of the plunger pump is connected with the bottom of the middle piston container 6;
a valve 3 and a pressure gauge 5 are arranged on a main pipeline of the gas cylinder 4, the main pipeline is divided into two branches, the first branch is introduced into a middle piston container 6, the second branch is introduced into a sapphire confining pressure chamber 8, and gas in the gas cylinder 4 is injected into the sapphire confining pressure chamber 8 and the middle piston container 6 in two paths;
the sapphire confining pressure chamber 8 is provided with a sapphire window, the top of the sapphire confining pressure chamber is divided into three joints, a one-way valve 9 is arranged on a pipeline of the left joint, the middle joint is connected with a main pipeline of the gas cylinder 4, and the right joint is connected with a second pipeline of the gas cylinder 4;
the microfluidic chip 7 is positioned in the sapphire confining pressure chamber 8, and pipelines butted with a left joint and a right joint of the sapphire confining pressure chamber 8 are respectively connected with an inlet and an outlet of the microfluidic chip 7.
First, the plunger pump 2 is turned on and water is sucked from the liquid containing vessel 1 to be pressurized; then the valve 3 is opened, and the gas in the gas bottle 4 is injected into the sapphire confining pressure chamber 8 and the intermediate piston container 6; when the valve 3 is opened, gas enters the sapphire confining pressure chamber 8 from the middle joint, at the moment, the right port of the microfluidic chip 7 serves as a gas inlet, the left port serves as a gas outlet, and the check valve 9 seals a pipeline; the pressure in the sapphire confining pressure chamber 8 and the pressure in the microfluidic chip 7 reach preset pressure at the same time, no pressure difference exists between the inside and the outside of the microfluidic chip 7, the potential burst hazard is eliminated, the pressure in the sapphire confining pressure chamber 8 is monitored by a pressure gauge 5, the realization of accurate pressure is controlled by the intermediate piston container 6 and the plunger pump 2, and the plunger pump 2 adopts a constant pressure mode to reach the preset pressure by moving the position of a piston; the back pressure regulation is realized through the plunger pump 2, the middle piston container 6 and the one-way valve 9; in the system, only when the left end fluid pressure of the check valve 9 is greater than the right end fluid pressure, the left end fluid can pass through the pipeline, if the left end fluid pressure is less than the right end fluid pressure, the check valve 9 is in a closed state to prohibit the fluid from passing through; when the pressure of the fluid at the left end of the one-way valve 9 is greater than the confining pressure, the fluid starts to enter the microfluidic chip 7, at the moment, the right port of the microfluidic chip 7 serves as a fluid outlet, the left port serves as a fluid inlet, the fluid flows into the middle piston container 6 through the right port of the microfluidic chip 7, at the moment, the plunger pump 2 adopts a constant pressure mode, the middle piston container 6 serves as a back pressure regulator to regulate the piston to move downwards, and then the high pressure brought by the newly injected fluid is regulated to reach the preset pressure; if the injected fluid is gas, the pressure in the microfluidic chip 7 is slightly higher than the set pressure, so that the gas flowing out cannot enter the microfluidic chip 7 again, but is mixed with the confining pressure gas to enter the sapphire confining pressure chamber 8, and the observation system is not influenced.
In order to prevent injected liquid from entering the sapphire confining pressure chamber 8 to affect the sapphire window, a pipeline which is connected with the intermediate piston container 6 and comes out from the right end of the microfluidic chip 7 must be lower than a pipeline which is connected with the intermediate piston container 6 and is connected with the intermediate port of the sapphire confining pressure chamber 8, so that the liquid is ensured to enter the intermediate piston container 6 and sink on the piston due to the action of gravity and cannot be blown into the sapphire confining pressure chamber 8.
It should be noted that because of the particularity of the non-return valve 9, the fluid used as confining pressure is only a gas and not a liquid.
The invention has the beneficial effects that: the system of the invention can adjust the confining pressure and the back pressure of the confining pressure chamber with simple process manufacture only by one plunger pump, one intermediate piston container and one-way valve, really realizes high pressure by simultaneously pressurizing the inside and the outside of the microfluidic chip, has simple system and strong operability, does not have potential safety hazard, and greatly reduces the system cost while realizing the functions of the confining pressure and the back pressure.
Drawings
FIG. 1 is a schematic diagram of a simple system for achieving high pressure in a microfluidic chip by simultaneously performing confining pressure and back pressure;
FIG. 2 is a diagram of CO at high temperature and high pressure using the system of the present invention2A microscopic visualization system of displacement brine;
in the figure: 1 a liquid holding container; 1-1 liquid holding container a; 1-2 liquid holding containers b; 1-3 liquid holding containers c; 2 a plunger pump; 2-1 plunger pump a; 2-2 plunger pump b; 3, a valve; 3-1, valve a; 3-2, valve b; 3-3 valve c; 3-4, valve d; 3-5 valve e; 3-6 valves f; 3-7, valve g; 3-8 valves h; 3-9i valves; 4, a gas cylinder; 5, a pressure gauge; 6 an intermediate piston container; 6-1 intermediate piston container a; 6-2 intermediate piston container b; 6-3 intermediate piston container c; 7 a microfluidic chip; 8 sapphire confining pressure chamber; 9 a one-way valve; 10 differential pressure sensor; 11 a computer; 12 a camera; 13, a microscope; 14 circulating water bath.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the following detailed description of the present invention "microscopic visualization system for CO2 displacement of brine at high temperature and high pressure". It should be understood that the specific embodiments described herein are merely illustrative of the present system and are not intended to limit the present system.
FIG. 2 is a view showing the addition of the injection system to FIG. 1, and also all valves are defaulted to a closed state before the start of the experiment, valve g3-7 is opened, plunger pump a2-1 and plunger pump b2-2 suck the liquid in liquid-holding vessel a1-1 and liquid-holding vessel b1-2 for pressurization, and valve g3-7 is closed. And (3) starting the circulating water bath 14 to heat the sapphire confining pressure chamber 8, opening a valve a3-1 after the temperature reaches a set temperature and is stable, performing pressurization operation on the microfluidic chip 7 and the sapphire confining pressure chamber 8, reading by a pressure gauge 5, and closing a valve a3-1 when the pressure is close to a preset pressure. The plunger pump a2-1 is activated to set its operation mode to "constant pressure mode" to increase the pressure in the sapphire enclosure chamber 8 to a preset pressure. After the pressure in the microfluidic chip 7 is stabilized, opening a valve f3-6, a valve i3-9 and a valve c3-3, sucking the saline in a liquid containing container c 1-3 into a middle piston container b6-2 through a plunger pump b2-2, closing the valve i3-9, opening a valve b3-2, injecting the saline into the microfluidic chip 7, continuously pressurizing through the plunger pump b2-2, enabling the saline to enter the microfluidic chip 7 through a one-way valve 9 when the pressure of the saline is greater than the pressure in a sapphire confining pressure chamber 8, observing the microfluidic chip 7 by using a camera 12 and a microscope 13 at the moment, stopping injecting until the microfluidic chip 7 is completely saturated by the saline, and closing the valve b3-2 and the valve c 3-3. After the pressure in the microfluidic chip 7 is stabilized again, the valve h3-8 is opened to enable CO to be discharged2Gas was injected into the intermediate piston vessel 6-3, valve h3-8 was closed, valve d3-4 and valve e3-5 were opened, and CO in the intermediate piston vessel c6-3 was pumped at a constant rate by the plunger pump b2-2 in "constant flow mode"2Injected into the microfluidic chip 7, again only when the CO is present2The pressure is higher than the pressure in the confining pressure chamber and then can enter the microfluidic chip 7 through the one-way valve 9 to displace saline, the displacement process is shot and recorded through the camera 12 and the microscope 13, and the change of the pressure difference at the inlet and the outlet is also recorded through the pressure difference sensor 10. The brine and CO discharged from the right end of the micro-fluidic chip 7 in the whole process2All enter an intermediate piston container a6-1, wherein the saline drops toOn the piston, the CO can not enter the sapphire confining pressure chamber 8, and the pressure in the microfluidic chip 7 is always higher than the set pressure, so that the CO flows out2Will mix with the confining pressure gas and enter the sapphire confining pressure chamber 8 and will not re-enter the microfluidic chip 7. Meanwhile, the middle piston container 6 and the plunger pump a2-1 adopt a constant pressure mode, so that the pressure at the right end of the microfluidic chip 7 is always regulated, namely, the back pressure is regulated.