CO2 fluid non-woven fabric entanglement system based on gradient pressure regulation and targeted phase change

Abstract

The CO2 fluid non-woven fabric entanglement system based on gradient pressure regulation and targeted phase change comprises an entanglement cavity and a nozzle, wherein the entanglement cavity comprises a high-pressure area, a phase change trigger cavity and a pressure regulation cavity which are sequentially distributed from top to bottom; in the high-pressure area, the phase change triggering cavity is communicated with the pressure adjusting cavity; the high-pressure area is located between the bottom of the nozzle and the upper supporting plate. A fiber web channel allowing a fiber web to pass through is arranged between the bottom of the nozzle and the upper surface of the upper supporting plate, and when the fiber web passes through the fiber web channel, fluid jet flow sprayed by the nozzle entangles the fiber web. The phase change trigger cavity is located between the upper supporting plate and the first bottom plate. The pressure adjusting cavity is located below the first bottom plate. The pressure of the high-pressure area is P1, the pressure of the phase change trigger cavity is P2, and the pressure of the entanglement cavity is P3. P1gt; p2gt, P2gt; p3 and P2 are lower than the saturated vapor pressure of the supercritical CO2 fluid at the current process temperature. Therefore, on the premise that energy consumption is not remarkably improved, advanced phase change of jet flow can be effectively avoided.

Description

Technical Field

[0001] This invention relates to a nonwoven fabric entanglement system, belonging to the field of nonwoven fabric manufacturing, and particularly to a CO2 fluid nonwoven fabric entanglement system based on gradient pressure regulation and targeted phase change. Background Technology

[0002] In the field of nonwoven fabric processing, hydroentangling is a commonly used reinforcement technique. This method uses high-pressure water to generate multiple fine water jets, which are sprayed onto the fiber web. The water jets repeatedly penetrate and impact the fiber web, causing the fibers to shift, entangle, and bind together under hydraulic action, thereby reinforcing the fiber web. However, hydroentangling not only consumes a large amount of water resources but also has high energy consumption. Therefore, there is a need to propose a non-aqueous medium that forms a fluid jet under pressure to replace water in reinforcing the fiber web in the entanglement cavity and causing it to vaporize after entanglement (for example, the waterless reinforcement method for enhancing fiber web entanglement using CO2 phase change fluid proposed in Chinese patent application No. 2025116011678).

[0003] This non-aqueous medium forms a fluid jet within the nozzle. This jet needs to remain in a liquid or supercritical state to penetrate the fiber web in order to achieve effective fiber entanglement. However, when the high-pressure jet is directed from the nozzle into the entanglement chamber, which is under lower pressure, "flash evaporation" (i.e., premature vaporization from a liquid or supercritical state) occurs before the fibers can be effectively pierced and entangled. Once the jet prematurely changes phase to gas, its momentum decreases sharply, making it unable to effectively complete entanglement. This leads to problems such as low entanglement efficiency, increased risk of product damage, and poor process controllability. Currently, flash evaporation is often suppressed by increasing the overall pressure of the entanglement chamber. However, due to the large volume of the entanglement chamber, maintaining its overall high pressure will directly increase the system's energy consumption significantly. This makes it impossible to effectively avoid premature phase change of the jet without significantly increasing energy consumption.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the overall background of this patent application and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects and problems existing in the prior art that cannot effectively avoid premature phase change of the jet without significantly increasing energy consumption, and to provide a CO2 fluid nonwoven fabric entanglement system based on gradient pressure regulation and targeted phase change that can effectively avoid premature phase change of the jet without significantly increasing energy consumption.

[0006] To achieve the above objectives, the technical solution of the present invention is: a CO2 fluid nonwoven fabric entanglement system based on gradient pressure regulation and targeted phase change, the system comprising an entanglement chamber and a nozzle, the nozzle being disposed at the top of the entanglement chamber;

[0007] The entanglement cavity includes a high-pressure zone, a phase change triggering cavity, and a pressure regulating cavity distributed from top to bottom; the high-pressure zone, the phase change triggering cavity, and the pressure regulating cavity are connected; the entanglement cavity is in fluid communication with a gas recovery system for recovering CO2;

[0008] The high-pressure zone is located between the bottom of the nozzle and the upper support plate; a fiber web channel is provided between the bottom of the nozzle and the upper surface of the upper support plate for the fiber web to pass through, and when the fiber web passes through the fiber web channel, the fluid jet sprayed by the nozzle entangles the fiber web;

[0009] The phase change trigger cavity is located between the upper support plate and the first base plate;

[0010] The pressure regulating chamber is located below the first base plate;

[0011] The pressure in the high-pressure zone is P1, the pressure in the phase change trigger cavity is P2, and the pressure in the entanglement cavity is P3; P1>P2>P3, and P2 is lower than the saturated vapor pressure of the supercritical CO2 fluid at the current process temperature.

[0012] The high-pressure zone is formed by the bottom of the nozzle, two parallel partitions fixed on both sides of the nozzle, and the upper support plate.

[0013] The phase change trigger cavity is formed by an upper support plate, a first bottom plate, and four side plates;

[0014] The upper support plate is the top surface of the phase change trigger cavity, the first bottom plate is the bottom surface of the phase change trigger cavity, and the four side plates are connected to the section between the upper support plate and the first bottom plate, forming the side walls of the phase change trigger cavity; the length of the upper support plate is equal to the length of the first bottom plate, and the width of the upper support plate is less than the width of the first bottom plate.

[0015] The upper support plate has several through holes for the fluid jet to pass through and enter the phase change trigger cavity.

[0016] The pressure regulating chamber is formed by a first bottom plate, a second bottom plate, and four side plates.

[0017] The first base plate is the top surface of the pressure regulating cavity, the second base plate is the bottom surface of the pressure regulating cavity, and the four side plates are connected to the section between the first base plate and the second base plate, forming the side walls of the pressure regulating cavity.

[0018] The first base plate has several through holes for pressure communication between the phase change trigger cavity and the pressure regulating cavity.

[0019] An air inlet is provided on the second base plate. The air inlet is connected to a high-pressure air pump and is used to inject gas into the pressure regulating chamber to increase P2.

[0020] The second base plate has an air outlet, which is connected to a vacuum pumping device to extract gas from the pressure regulating chamber to reduce P2.

[0021] A pressure sensor is installed inside the phase change trigger cavity.

[0022] The nozzle comprises, from top to bottom, an inlet section, a primary pressurization section, a flow stabilization section, and an outlet focusing section;

[0023] The primary pressurization section is a tapered conical channel; the flow stabilization section is a cylindrical straight channel; and the outlet focusing section is a streamlined contraction or conical channel.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. A CO2 fluid non-woven fabric entanglement system based on gradient pressure regulation and targeted phase change according to the present invention. The system includes an entanglement chamber and a nozzle. The entanglement chamber includes a high-pressure zone, a phase change trigger chamber, and a pressure regulation chamber that are sequentially distributed from top to bottom. The high-pressure zone, the phase change trigger chamber, and the pressure regulation chamber are connected and communicate with each other. The entanglement chamber communicates with a gas recovery system. The pressures of the high-pressure zone, the phase change trigger chamber, and the entanglement chamber are P1, P2, and P3 respectively, where P1 > P2 > P3, and P2 is lower than the saturated vapor pressure of the supercritical fluid at the current process temperature. During application, first, a pressure gradient from high to low is established and maintained in the entanglement chamber. The pressure P1 in the high-pressure zone is provided by an upstream pressure supply system to provide an initial high kinetic energy for the fluid jet. The pressure P3 in the entanglement chamber serves as the lower background pressure of the system and is maintained by the gas recovery system. At the same time, the pressure P2 in the phase change trigger chamber is dynamically controlled and stabilized at a preset target value through the pressure regulation chamber. This value needs to satisfy P3 < P2 < P1 and be lower than the saturated vapor pressure of CO2 at the current process temperature. The fiber web enters below the nozzle along the fiber web channel, and the supercritical CO2 fluid is ejected through the nozzle to form a high-pressure fluid jet. This jet maintains a high momentum state in the high-pressure zone and then strongly penetrates the fiber web, causing the fibers to entangle and fix with each other. During this penetration process, although the preset target value P2 is lower than the saturated vapor pressure, the local hydrodynamic pressure generated by the high-kinetic-energy jet in the fiber layer is sufficient to temporarily maintain it in a liquid or supercritical state, effectively completing mechanical entanglement and suppressing premature phase change inside the fiber web. When the fluid jet completely penetrates the fiber web and enters the phase change trigger chamber instantaneously, the kinetic energy of the fluid jet rapidly dissipates, and the local pressure balances with P2. Since the preset target value P2 is lower than the saturated vapor pressure, the fluid jet immediately meets the thermodynamic conditions for phase change and undergoes a controlled violent flash evaporation in the phase change trigger chamber. The shock wave generated by the phase change acts on the back of the fiber web. Part of the shock wave acts on the unentangled area of the fiber web, causing the unentangled fiber web to form a preliminary entanglement. Another part of the shock wave acts on the area of the fiber web that has been completed with entanglement, strengthening the entanglement of the completed fiber web. The advantages of the present invention further include:

[0026] First, the high-pressure CO2 jet maintains a high momentum state in the high-pressure zone and strongly penetrates the fiber web. Since the phase change trigger chamber below the fiber web maintains a medium-pressure buffer zone P2 higher than P3 through dynamic compensation, it effectively suppresses the premature gasification of the jet in the fiber layer, enabling the jet to fully push and penetrate the fibers to complete the core mechanical entanglement.

[0027] Second, only the pressure P2 in the relatively small-volume phase change trigger chamber needs to be dynamically regulated, without maintaining the high-pressure state of the entire large entanglement chamber, thus significantly reducing the overall energy consumption.

[0028] Furthermore, based on the pressure gradient P1>P2>P3, the fluid jet enters the phase change triggering chamber after penetrating the fiber web. Since the pressure P2 in this chamber is lower than the saturated vapor pressure, the fluid jet undergoes synchronous and intense flash evaporation within the preset target area. The uniform shock wave generated by the phase change impacts the unentangled area on the back of the fiber web, achieving initial entanglement; and it also performs secondary impact compaction on the already entangled area, thereby enhancing the entanglement effect.

[0029] Therefore, the present invention can not only entangle the fiber web, but also effectively avoid premature phase change of the jet without significantly increasing energy consumption.

[0030] 2. In the CO2 fluid nonwoven fabric entanglement system based on gradient pressure regulation and targeted phase change of this invention, an air inlet is provided on the second base plate, which is connected to a high-pressure air pump. An air outlet is also provided on the second base plate, which is connected to a vacuum pumping device. In application, gas is injected into the pressure regulating chamber through the air inlet by the high-pressure air pump, or gas is extracted from the chamber through the air outlet by the vacuum pumping device. By adjusting the pressure in the pressure regulating chamber, the pressure P2 of the phase change triggering chamber is dynamically adjusted and maintained, providing a pressure buffer for the phase change triggering chamber and thus reducing the fluctuation of pressure P2. Therefore, this invention can not only effectively avoid premature phase change of the jet without significantly increasing energy consumption, but also achieve stability in the phase change process.

[0031] 3. In the CO2 fluid nonwoven fabric entanglement system based on gradient pressure regulation and targeted phase change of the present invention, the nozzle includes an inlet section, a primary pressurization section, a stabilization section and an outlet focusing section connected sequentially from top to bottom. The primary pressurization section is a tapered conical channel, the stabilization section is a cylindrical straight channel, and the outlet focusing section is a streamlined contraction or conical channel. In application, supercritical CO2 fluid is first smoothly introduced through the inlet section and enters the primary pressurization section. In the tapered conical channel of the primary pressurization section, the fluid is initially accelerated, its kinetic energy is increased, and the flow state tends to stabilize. Subsequently, the fluid enters the stabilization section. In this cylindrical straight channel, the streamlines are further streamlined, turbulence and vortices are eliminated, and the cross-sectional velocity distribution is homogenized. Finally, the fluid reaches the outlet focusing section. After final constraint and condensation by the streamlined contraction or conical channel of the outlet focusing section, a bundled, stable, high-momentum liquid or supercritical needle-shaped jet is formed, which is ejected from the nozzle and directed towards the fiber web. Therefore, this invention not only achieves stability in the phase transition, but also improves the focusing, stability, and momentum of the jet. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0033] Figure 2This is a schematic diagram of the phase change trigger cavity and pressure regulating cavity in the longitudinal direction of the present invention.

[0034] Figure 3 This is a schematic diagram of the nozzle structure in this invention.

[0035] Figure 4 This is a schematic diagram of the entanglement process of the present invention.

[0036] In the diagram: Entanglement chamber 1, Nozzle 2, Inlet section 21, Primary pressurization section 22, Flow stabilization section 23, Outlet focusing section 24, High-pressure zone 3, Baffle 31, Phase change trigger chamber 4, Upper support plate 41, First base plate 42, Pressure regulating chamber 5, Second base plate 51, Air inlet 511, Air outlet 512, High-pressure air pump 513, Vacuum pumping device 514, Side plate 52, Fiber web 6, Fiber web channel 61, Fluid jet 62, Pressure sensor 7. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] See Figures 1-4 A CO2 fluid nonwoven fabric entanglement system based on gradient pressure regulation and targeted phase change, the system includes an entanglement chamber 1 and a nozzle 2, the nozzle 2 being disposed at the top of the entanglement chamber 1;

[0039] The entanglement chamber 1 includes a high-pressure zone 3, a phase change triggering chamber 4, and a pressure regulating chamber 5 distributed sequentially from top to bottom; the high-pressure zone 3, the phase change triggering chamber 4, and the pressure regulating chamber 5 are connected; the entanglement chamber 1 is in fluid communication with a gas recovery system for recovering CO2;

[0040] The high-pressure zone 3 is located between the bottom of the nozzle 2 and the upper support plate 41; a fiber web channel 61 for the fiber web 6 to pass through is provided between the bottom of the nozzle 2 and the upper surface of the upper support plate 41. When the fiber web 6 passes through the fiber web channel 61, the fluid jet 62 sprayed by the nozzle 2 entangles the fiber web 6.

[0041] The phase change trigger cavity 4 is located between the upper support plate 41 and the first base plate 42;

[0042] The pressure regulating chamber 5 is located below the first base plate 42;

[0043] The pressure in the high-pressure zone 3 is P1, the pressure in the phase change triggering chamber 4 is P2, and the pressure in the entanglement chamber 1 is P3; P1>P2>P3, and P2 is lower than the saturated vapor pressure of the supercritical CO2 fluid at the current process temperature.

[0044] The high-pressure zone 3 is formed by the bottom of the nozzle 2, two parallel partitions 31 fixed on both sides of the nozzle 2, and the upper support plate 41.

[0045] The phase change trigger cavity 4 is formed by an upper support plate 41, a first bottom plate 42 and four side plates 52;

[0046] The upper support plate 41 is the top surface of the phase change trigger cavity 4, the first bottom plate 42 is the bottom surface of the phase change trigger cavity 4, and the four side plates 52 are connected to the section between the upper support plate 41 and the first bottom plate 42, forming the side walls of the phase change trigger cavity 4; the length of the upper support plate 41 is equal to the length of the first bottom plate 42, and the width of the upper support plate 41 is less than the width of the first bottom plate 42.

[0047] The upper support plate 41 has several through holes for the fluid jet 62 to pass through and enter the phase change trigger cavity 4.

[0048] The pressure regulating cavity 5 is formed by the first base plate 42, the second base plate 51, and four side plates 52.

[0049] The first base plate 42 is the top surface of the pressure regulating cavity 5, the second base plate 51 is the bottom surface of the pressure regulating cavity 5, and the four side plates 52 are connected to the section between the first base plate 42 and the second base plate 51, forming the side walls of the pressure regulating cavity 5.

[0050] The first base plate 42 has several through holes for pressure communication between the phase change trigger cavity 4 and the pressure regulating cavity 5.

[0051] The second base plate 51 has an air inlet 511, which is connected to a high-pressure air pump 513 to inject gas into the pressure regulating chamber 5 to increase P2.

[0052] The second base plate 51 has an air outlet 512, which is connected to a vacuum pumping device 514 to extract gas from the pressure regulating chamber 5 to reduce P2.

[0053] A pressure sensor 7 is installed inside the phase change trigger cavity 4.

[0054] The nozzle 2 includes an inlet section 21, a primary pressurization section 22, a flow stabilization section 23 and an outlet focusing section 24 connected sequentially from top to bottom;

[0055] The primary pressurization section 22 is a tapered conical channel; the flow stabilization section 23 is a cylindrical straight channel; and the outlet focusing section 24 is a streamlined contraction or conical channel.

[0056] The following are supplementary descriptions of the present invention:

[0057] Preferably, the through holes on the upper support plate 41 are evenly distributed.

[0058] Preferably, the upper support plate 41 of the present invention is made of stainless steel with a thickness of 2mm-5mm. This thickness ensures that the upper support plate 41 has sufficient mechanical strength to support the fiber web 6 and withstand the direct impact of the high-pressure fluid jet.

[0059] Preferably, the upper support plate 41 of the present invention has a width of 0.5mm-1mm and a length greater than the width of the fiber web 6.

[0060] Preferably, the phase change trigger cavity 4 of the present invention has a height of 5mm-10mm, a width of 10mm-20mm, and a length greater than the width of the fiber web 6.

[0061] Preferably, the through holes on the first base plate 42 are evenly distributed.

[0062] Preferably, the diameter of the through hole on the first base plate 42 is 0.5mm-2mm.

[0063] Preferably, the length and width of the pressure regulating cavity 5 are the same as the length and width of the phase change trigger cavity 4, and the height is not less than 20mm.

[0064] Preferably, the first base plate 42, the second base plate 51, and the four side plates 52 of the present invention are made of stainless steel.

[0065] Preferably, the high-pressure air pump 513 of the present invention is a miniature high-pressure air pump.

[0066] Preferably, the vacuum pumping device 514 of the present invention is a miniature vacuum pumping device.

[0067] Preferably, the nozzle 2 of the present invention can be arranged in a single row, double row or multi-row array according to production needs; specifically, the arrangement density of the single row of holes is 8-24 holes / cm, the double row of holes is 16-36 holes / cm, and the triple row of holes is 24-48 holes / cm.

[0068] The present invention preferably has the nozzle 2 having a diameter and arrangement density that are precisely matched with the flow rate of the high-pressure pump and operating in a stable high-pressure environment to ensure the fluid jet velocity, thereby achieving the ideal fiber entanglement effect.

[0069] Preferably, the inner wall of the outlet focusing section 24 of this invention must achieve an extremely high degree of smoothness, and the orifice shape must be round and the orifice diameter must be uniform; in order to ensure the formation of a bundled "needle-shaped" CO2 jet.

[0070] The entanglement chamber mentioned in this invention refers to the large main chamber of the entire entanglement equipment, which is filled with CO2 gas and maintains a low and relatively stable background pressure P3, typically controlled between 3 MPa and 6 MPa; P3 is maintained by the main exhaust and recovery system and is one of the main determinants of system energy consumption.

[0071] Preferably, the distance between the partition plate 31 and the center line of the nozzle hole of the outlet focusing section 24 is set to 2mm-6mm.

[0072] The pressure P1 of the high-pressure zone 3 described in this invention is determined and maintained by the upstream CO2 supply system, and its pressure range is usually controlled between 3.5MPa and 10MPa. The setting of the pressure P1 must meet the following requirements: higher than the saturated vapor pressure of CO2 at the current process temperature to suppress premature phase change of the fluid jet in the fiber web; and lower than the initial pressure of the fluid jet at the outlet of nozzle 2.

[0073] The design of the phase change trigger cavity 4 described in this invention ensures that for the same row of nozzles 2, all fluid jets 62 enter the same small, sealed chamber with uniform pressure and height after penetrating the fiber mesh 6. This ensures that the spatial location of the phase change of the fluid jets 62 is precisely limited within this chamber. At the same time, due to the uniform pressure and small volume of the chamber, the phase change process of all fluid jets 62 can be highly synchronized in time. This, from both spatial and temporal dimensions, collaboratively guarantees the controllability of the phase change shock wave effect and the consistency of the process.

[0074] The fluid connection between the entanglement chamber 1 and the gas recovery system for recovering CO2 in this invention means that the entanglement chamber 1 is connected to the gas recovery system, so that the CO2 gas formed after the phase change during the entanglement process can be continuously drawn in and transported to the gas recovery system, thereby realizing the recycling of the medium.

[0075] Example 1:

[0076] See Figures 1-4 A CO2 fluid nonwoven fabric entanglement system based on gradient pressure regulation and targeted phase change is described. The system includes an entanglement chamber 1 and a nozzle 2, with the nozzle 2 positioned at the top of the entanglement chamber 1. The entanglement chamber 1 includes a high-pressure zone 3, a phase change triggering chamber 4, and a pressure regulating chamber 5, distributed sequentially from top to bottom. The high-pressure zone 3, phase change triggering chamber 4, and pressure regulating chamber 5 are connected. The entanglement chamber 1 is fluidly connected to a gas recovery system for recovering CO2. The high-pressure zone 3 is located between the bottom of the nozzle 2 and an upper support plate 41. The bottom of the nozzle 2 and the upper support plate 41... A fiber web channel 61 is provided between the upper surfaces for the fiber web 6 to pass through. When the fiber web 6 passes through the fiber web channel 61, the fluid jet 62 sprayed by the nozzle 2 entangles the fiber web 6. The phase change triggering chamber 4 is located between the upper support plate 41 and the first bottom plate 42. The pressure regulating chamber 5 is located below the first bottom plate 42. The pressure of the high pressure zone 3 is P1, the pressure of the phase change triggering chamber 4 is P2, and the pressure of the entanglement chamber 1 is P3. P1>P2>P3, and P2 is lower than the saturated vapor pressure of the supercritical CO2 fluid at the current process temperature.

[0077] During application, first, a stable pressure gradient from high to low is established and maintained within the entanglement chamber 1: The high pressure at the inlet of the nozzle 2 is established by the upstream supercritical CO2 booster pump, enabling the formation and maintenance of the high-pressure region 3 between the outlet of the nozzle 2 and the upper support plate 41, with a pressure P1, to provide the initial high kinetic energy for the fluid jet 62; The lower background pressure P3 of the entanglement chamber 1 is maintained through the gas recovery system; Meanwhile, the pressure P2 in the phase change trigger chamber 4 is pre-adjusted and dynamically controlled through the pressure regulation chamber 5 to satisfy P3 < P2 < P1 and be lower than the saturated vapor pressure of CO2 at the current process temperature; Subsequently, the fiber web 6 is horizontally and continuously passed through the fiber web channel 61; When the fiber web 6 runs below the nozzle 2, the supercritical CO2 fluid is ejected through the nozzle 2 to form a high-pressure fluid jet 62; This jet maintains a high-momentum state in the high-pressure region 3 and strongly penetrates the fiber web 6 by virtue of its own kinetic energy, causing the fibers to entangle with each other; During the process of penetrating the fiber web 6, the phase change trigger chamber 4 is dynamically compensated through the pressure regulation chamber 5 to keep P2 at the preset value in real time; This preset value is lower than the saturated vapor pressure, but the local hydrodynamic pressure generated by the high-kinetic-energy jet within the fiber layer is still sufficient to temporarily maintain it in a liquid or supercritical state, thus effectively completing mechanical entanglement and suppressing the premature phase change of the fluid jet 62 inside the fiber web 6; The moment when the fluid jet 62 completely penetrates the fiber web 6 and enters the phase change trigger chamber 4, its kinetic energy rapidly dissipates, and the local pressure drops to balance with the ambient pressure P2; Since the preset P2 value is lower than the saturated vapor pressure, the fluid jet 62 immediately meets the thermodynamic conditions for phase change at this moment and undergoes a violent and synchronous flash evaporation within the "target area"; The shock wave released by the phase change acts on the fiber network from the back of the fiber web 6, and a part of the energy acts on the unentangled area of the fiber web 6 to form a preliminary entanglement; Another part of the energy acts on the area of the fiber web 6 that has completed entanglement to achieve secondary impact and compaction reinforcement in this area, thereby improving the entanglement uniformity and overall strength.

[0078] Example 2:

[0079] The basic content is the same as that of Example 1, with the difference being that: The high-pressure region 3 is jointly enclosed by the bottom of the nozzle 2, two parallel partition plates 31 fixed on both sides of the nozzle 2, and the upper support plate 41.

[0080] During application, the upper ends of the two parallel partition plates 31 are fixed on both sides of the outer wall of the nozzle 2, and the lower ends of the partition plates 31 extend to be close to but not touch the upper surface of the upper support plate 41, and the vertical distance between the lower ends of the partition plates 31 and the upper support plate 41 is less than the vertical distance between the bottom of the nozzle 2 and the upper support plate 41; Thus, the two parallel partition plates 31, the bottom of the nozzle 2, and the upper support plate 41 jointly enclose a long and narrow chamber that is closed at the top and open at the bottom, namely the high-pressure region 3, and the partition plates 31 form a physical barrier closer to the fiber web 6;

[0081] When the supercritical CO2 fluid jet 62 is ejected from the nozzle 2, it immediately enters the high-pressure zone 3. The baffle 31, which is closer to the fiber web 6, effectively reduces the lateral mixing of the jet with the low-pressure gas in the entanglement cavity 1, thereby reducing the momentum dissipation of the fluid jet 62. This provides effective spatial constraint for the core jet, enabling it to maintain a stable and bundled high momentum state before penetrating the fiber web 6, ensuring the stability of the local pressure environment in the high-pressure zone 3, and thus more reliably suppressing the premature phase change of the jet in the fiber layer.

[0082] Example 3:

[0083] The basic content is the same as in Embodiment 1, except that: the phase change triggering cavity 4 is formed by an upper support plate 41, a first bottom plate 42, and four side plates 52; the upper support plate 41 is the top surface of the phase change triggering cavity 4, the first bottom plate 42 is the bottom surface of the phase change triggering cavity 4, and the four side plates 52 are connected to the section between the upper support plate 41 and the first bottom plate 42, forming the sidewalls of the phase change triggering cavity 4; the length of the upper support plate 41 is equal to the length of the first bottom plate 42, and the width of the upper support plate 41 is less than the width of the first bottom plate 42; the upper support plate 41 has several through holes for the fluid jet 62 to pass through and enter the phase change triggering cavity 4.

[0084] In application, the upper support plate 41 is located below the outlet of the nozzle 2. Its length is equal to the length of the first base plate 42 and both are greater than the width of the fiber web 6, providing stable support for the continuously running fiber web 6. By adjusting the position of the upper support plate 41, the center vertical line of the nozzle 2 falls on the center line of the width direction of the upper support plate 41. After the high-pressure CO2 fluid jet 62 penetrates the fiber web 6, it enters the phase change trigger chamber 4 below through the through hole on the upper support plate 41.

[0085] The first base plate 42 has a relatively large width, which, together with the side plate 52, forms a relatively spacious and pressure-uniform flat cavity, constituting a stable physical target area. Within this target area, because the pressure P2 is lower than the saturated vapor pressure of CO2 at the current process temperature, the jet 62 undergoes a violent and synchronous flash phase change. The width of the upper support plate 41 is smaller than that of the first base plate 42, which effectively supports the fiber web 6 while reducing the area of ​​the upper support plate 41 that blocks the back of the fiber web 6. Therefore, when the shock wave generated by the phase change acts from the back of the fiber web 6, the narrower upper support plate 41 allows the shock wave to act on the wider fiber web area on both sides of the upper support plate 41 with less obstruction, thereby achieving a more uniform and sufficient impact coverage and reinforcement of the back of the fiber web 6.

[0086] Example 4:

[0087] The basic content is the same as in Embodiment 1, except that: the pressure regulating cavity 5 is formed by a first base plate 42, a second base plate 51 and four side plates 52; the first base plate 42 is the top surface of the pressure regulating cavity 5, the second base plate 51 is the bottom surface of the pressure regulating cavity 5, and the four side plates 52 are connected to the section between the first base plate 42 and the second base plate 51, forming the side walls of the pressure regulating cavity 5.

[0088] In application, the pressure regulating chamber 5 is located directly below the phase change trigger chamber 4 and is connected to the phase change trigger chamber 4 through its top surface (i.e., the first base plate 42), forming a vertically integrated structure. The through hole on the first base plate 42 serves as a gas channel connecting the phase change trigger chamber 4 and the pressure regulating chamber 5. An air inlet and an air outlet are respectively provided on the second base plate 51 for connecting to an external pressure regulating system to introduce or export gas into or out of the pressure regulating chamber 5. By regulating the gas in the pressure regulating chamber 5 through the air inlet and air outlet, the internal pressure of the pressure regulating chamber 5 can be dynamically changed. This pressure change is transmitted through the through hole on the first base plate 42 and stabilizes the pressure P2 in the phase change trigger chamber 4. The pressure regulating chamber 5 physically isolates the active pressure regulation execution part from the phase change trigger chamber 4 and forms a buffer, effectively attenuating the pressure pulsation and disturbance during the gas flow process. This provides a structural basis for implementing more stable and precise closed-loop control of P2, thereby ensuring the consistency and repeatability of the targeted phase change process.

[0089] Example 5:

[0090] The basic content is the same as in Embodiment 1, except that: the first base plate 42 has several through holes for pressure communication between the phase change triggering cavity 4 and the pressure regulating cavity 5; the second base plate 51 has an air inlet 511 connected to a high-pressure air pump 513 for injecting gas into the pressure regulating cavity 5 to increase P2; the second base plate 51 has an air outlet 512 connected to a vacuum pumping device 514 for extracting gas from the pressure regulating cavity 5 to decrease P2; and a pressure sensor 7 is installed inside the phase change triggering cavity 4.

[0091] In application, pressure sensor 7 monitors the pressure P2 in the phase change triggering chamber 4 in real time and feeds it back to the control system (e.g., PLC). The control system compares the real-time pressure P2 with a preset target value and drives the execution unit according to the deviation through a control algorithm (e.g., PID): if the real-time pressure P2 is detected to be too low, the high-pressure air pump 513 is controlled to inject CO2 gas into the pressure regulating chamber 5 through the air inlet 511; if the real-time pressure P2 is detected to be too high, the vacuum pumping device 514 is controlled to remove gas from the pressure regulating chamber 5 through the air outlet 512. The gas enters and exits through the through hole on the first base plate 42, thereby realizing real-time closed-loop dynamic compensation for the pressure P2 of the phase change triggering chamber 4. This high-precision closed-loop control improves the stability and response speed of pressure control and ensures the high repeatability of phase change triggering conditions and process accuracy.

[0092] Example 6:

[0093] The basic content is the same as in Embodiment 1, except that: the nozzle 2 includes an inlet section 21, a primary pressurizing section 22, a flow stabilizing section 23 and an outlet focusing section 24 connected sequentially from top to bottom; the primary pressurizing section 22 is a tapered conical channel; the flow stabilizing section 23 is a cylindrical straight channel; and the outlet focusing section 24 is a streamlined contraction or conical channel.

[0094] In application, inlet section 21 uses a standard high-pressure interface and is connected to the outlet of the CO2 booster pump. High-pressure CO2 fluid is smoothly introduced through inlet section 21 and flows sequentially through primary booster section 22, flow stabilization section 23, and outlet focusing section 24. Inlet section 21 ensures smooth fluid introduction and connection. Primary booster section 22 initially accelerates the fluid and increases its kinetic energy, while stabilizing any upstream flow fluctuations. Flow stabilization section 23 eliminates turbulence and vortices generated after acceleration by primary booster section 22, making the velocity distribution of the fluid on the cross-section more uniform. Outlet focusing section 24 further compresses the fluid. The cross-sectional area forms a small-diameter, clearly defined "quasi-rigid" fluid jet 62. This multi-stage composite nozzle structure of "gradual convergence + steady flow + focusing" synergistically forms a fluid jet 62 with good convergence, stable flow, and high momentum density by progressively enhancing the fluid kinetic energy, fully optimizing the flow state, and ultimately focusing the energy. This fluid jet 62 can effectively suppress unexpected phase change nucleation inside the nozzle 2, ensuring that it maintains a high-momentum liquid or supercritical state before reaching and penetrating the fiber web 6, thereby improving the penetration of entanglement, processing efficiency, uniformity of effect, and overall process controllability.

[0095] Specifically, the primary boosting section 22 is a tapered channel with a convergence angle of 12°-18°;

[0096] The flow stabilization section 23 is a cylindrical straight channel with a length-to-diameter ratio (L / D) between 3:1 and 5:1;

[0097] The outlet focusing section 24 is a streamline contraction or conical channel with a length of 0.1 mm - 0.5 mm and a pore diameter of 0.08 mm - 0.25 mm. The reason for setting the pore diameter of the outlet focusing section 24 to 0.08 mm - 0.25 mm is as follows: If the pore diameter is too small (less than 0.08 mm), the fluid jet 62 will lose the energy required for piercing during slight gasification, and the cost will increase due to the increased processing accuracy requirements. If the pore diameter is too large (greater than 0.25 mm), the consumption of CO2 fluid will increase, resulting in increased costs, and the entanglement effect does not increase linearly with the increase in pore diameter, so a large pore diameter is unnecessary.

[0098] Example 7:

[0099] The basic content is the same as that of Example 1, except that: the system further includes a control system, the control system is communicatively connected to a pressure sensor 7 disposed in the phase change trigger chamber 4, and the control system is electrically connected to a high-pressure air pump 513 and a vacuum pumping device 514 respectively.

[0100] During application, the pressure sensor 7 monitors the pressure P2 in the phase change trigger chamber 4 in real time and transmits it to the control system; the control system compares the real-time pressure P2 with the internally set target pressure P2, and generates a control instruction according to the built-in control algorithm (such as the PID algorithm), driving the high-pressure air pump 513 to inject CO2 gas (which can be recycled normal-temperature and normal-pressure CO2 gas) into the chamber, or driving the vacuum pumping device 514 to pump out gas from the chamber, thereby forming a control loop for real-time and dynamic closed-loop compensation of the pressure P2;

[0101] The pressure control of this loop follows the principle of P3 < P2 < P1, and the set value of the target pressure P2 is lower than the saturated vapor pressure of CO2 at the current process temperature; thus ensuring that when the CO2 fluid jet 62 travels in the fiber web 6, it maintains a liquid or supercritical state by virtue of the local high pressure generated by its high kinetic energy to complete entanglement; at the moment when the fluid jet 62 penetrates the fiber web 6 and enters the phase change trigger chamber 4, a controllable targeted phase change is immediately triggered due to the ambient pressure (i.e., P2) being lower than the saturated vapor pressure; thereby ensuring the stability, repeatability and high efficiency of the process;

[0102] Specifically, when the process temperature is 35 °C (at 35 °C, the saturated vapor pressure of CO2 is about 7.5 Mpa; at 25 °C, the saturated vapor pressure is about 6.43 MPa; at 20 °C, the saturated vapor pressure is about 5.7 Mpa; at 0 °C, the saturated vapor pressure is about 3.5 MPa), the pressure P1 in the high-pressure zone is set to 15 MPa, and the background pressure P3 of the entanglement chamber 1 is 5 MPa, then the target pressure P2 of the phase change trigger chamber 4 is set between 6.0 MPa and 7.2 MPa; this setting ensures that when the fluid jet 62 is within the fiber web, the ambient pressure (close to P2) is higher than the saturated vapor pressure, suppressing flash evaporation; when the fluid jet 62 penetrates the fiber web and enters the phase change trigger chamber, the ambient pressure (P2) is lower than the saturated vapor pressure, meeting the flash evaporation condition and immediately undergoing a phase change.

[0103] In addition, the control system is specifically a programmable logic controller (PLC) or an industrial computer (IPC), and the response time of the control system should be less than 10 milliseconds.

[0104] Example 8:

[0105] The basic content is the same as that of Example 7, except that: the system further includes a solenoid valve, which is electrically connected to the high-pressure air pump 513 and the vacuum pumping device 514 respectively, and the solenoid valve is electrically connected to the control system.

[0106] During application, the solenoid valve serves as a precision flow control component in the execution unit, and specifically, a precision proportional valve or a switch valve can be used; based on the deviation between the real-time pressure P2 fed back by the pressure sensor 7 and the target value, the control system calculates through a control algorithm and issues an adjustment command to the solenoid valve; the solenoid valve accordingly precisely adjusts its opening degree, thereby controlling the flow rate of the CO2 gas injected by the high-pressure air pump 513 into the pressure adjustment chamber 5 (and then to the phase change trigger chamber 4), or controlling the rate of gas extraction from the pressure adjustment chamber 5 by the vacuum pumping device 514; through the fine and rapid adjustment of the gas flow rate by the solenoid valve, a more sensitive and precise dynamic closed-loop control of the pressure P2 in the phase change trigger chamber 4 is achieved, further ensuring the stable maintenance of the pressure gradient (P3 < P2 < P1) and the accuracy of the targeted phase change trigger timing.

[0107] Example 9:

[0108] The basic content is the same as that of Example 1, except that: the fiber web 6 continuously enters below the nozzle 2 through the fiber web channel 61, and the fluid jet 62 ejected by the nozzle 2 penetrates or pierces into the fiber web 6 to entangle the raw material fibers in the fiber web 6; for any bundle of fluid jets 62, after it penetrates the fiber web 6, it enters the phase change trigger chamber 4 and undergoes gasification in the phase change trigger chamber 4 to generate a gaseous non-aqueous medium.

[0109] During application, refer to Figure 4The fluid jet 62 impacts the fiber web 6, and the enormous kinetic energy of the fluid jet 62 is directly transferred to the individual fibers in the fiber web 6, causing the individual fibers to vibrate, displace, and rearrange. Simultaneously, multiple fluid jets 62 work together to drag and pull the fibers. Under the combined effect of fluid dynamics, the fibers interweave, entangle, and hook together, thus achieving overall entanglement of the fiber web 6 and forming a stable three-dimensional network structure. After the entanglement process, the fluid jet 62 rapidly vaporizes in the phase change trigger chamber 4, generating a gaseous non-aqueous medium. The gaseous medium is recovered and recycled by a gas recovery system. Compared with the traditional hydroentangling process, this invention has advantages in energy saving and environmental protection: First, it completely eliminates the need for liquid water in the traditional hydroentangling process, eliminating the huge energy consumption caused by water pressurization, transportation, heating and recycling; Second, the efficient recovery and recycling of the gaseous medium through the gas recovery system reduces the energy input required for the continuous preparation of fresh high-pressure medium; In addition, it avoids the complex wastewater treatment process with high energy consumption from the source, realizing energy saving and clean production throughout the entire process.

[0110] The above description is only a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. Any equivalent modifications or changes made by those skilled in the art based on the content disclosed in the present invention should be included within the scope of protection set forth in the claims.

Claims

1. A CO2 fluid nonwoven web entanglement system based on gradient pressure regulation and targeted phase change, characterized by: The system comprises a entanglement cavity (1) and a nozzle (2), the nozzle (2) is arranged at the top of the entanglement cavity (1); The entanglement cavity (1) comprises a high pressure area (3), a phase transition triggering cavity (4) and a pressure regulating cavity (5) arranged in sequence from top to bottom; the high pressure area (3), the phase transition triggering cavity (4) and the pressure regulating cavity (5) are communicated; the entanglement cavity (1) is in fluid communication with a gas recovery system for recovering CO2; The high pressure area (3) is located between the bottom of the nozzle (2) and the upper supporting plate (41); a web channel (61) for the web (6) to pass through is arranged between the bottom of the nozzle (2) and the upper surface of the upper supporting plate (41), when the web (6) passes through the web channel (61), the fluid jet (62) sprayed by the nozzle (2) entangles the web (6); The phase transition triggering cavity (4) is located between the upper supporting plate (41) and the first bottom plate (42); The pressure regulating cavity (5) is located below the first bottom plate (42); The pressure of the high pressure area (3) is P1, the pressure of the phase transition triggering cavity (4) is P2, and the pressure of the entanglement cavity (1) is P3; P1>P2>P3, and P2 is lower than the saturation vapor pressure of supercritical CO2 fluid at the current process temperature.

2. The CO2 fluid nonwoven web entanglement system based on gradient pressure regulation and targeted phase change of claim 1, wherein: The high pressure area (3) is enclosed by the bottom of the nozzle (2), two parallel partition plates (31) fixed on both sides of the nozzle (2) and the upper supporting plate (41).

3. The CO2 fluid nonwoven web entanglement system based on gradient pressure regulation and targeted phase change of claim 1, wherein: The phase transition triggering cavity (4) is enclosed by the upper supporting plate (41), the first bottom plate (42) and four side plates (52); The upper supporting plate (41) is the top surface of the phase transition triggering cavity (4), the first bottom plate (42) is the bottom surface of the phase transition triggering cavity (4), and the four side plates (52) are connected between the upper supporting plate (41) and the first bottom plate (42) and are the side walls of the phase transition triggering cavity (4); the length of the upper supporting plate (41) is equal to the length of the first bottom plate (42), and the width of the upper supporting plate (41) is less than the width of the first bottom plate (42).

4. The CO2 fluid nonwoven web entanglement system based on gradient pressure regulation and targeted phase change of claim 3, wherein: The upper supporting plate (41) is provided with a plurality of through holes for the fluid jet (62) to pass through and enter the phase transition triggering cavity (4).

5. The CO2 fluid nonwoven web entanglement system based on gradient pressure regulation and targeted phase change of claim 4, wherein: The pressure regulating cavity (5) is enclosed by the first bottom plate (42), the second bottom plate (51) and four side plates (52); The first bottom plate (42) is the top surface of the pressure regulating cavity (5), the second bottom plate (51) is the bottom surface of the pressure regulating cavity (5), and the four side plates (52) are connected between the first bottom plate (42) and the second bottom plate (51) and are the side walls of the pressure regulating cavity (5).

6. The CO2 fluid nonwoven web entanglement system based on gradient pressure regulation and targeted phase change of claim 5, wherein: The first bottom plate (42) is provided with a plurality of through holes for the phase transition triggering cavity (4) and the pressure regulating cavity (5) to communicate in pressure.

7. The CO2 fluid nonwoven web entanglement system based on gradient pressure regulation and targeted phase change of claim 6, wherein: The second bottom plate (51) is provided with an air inlet hole (511), the air inlet hole (511) is connected with a high pressure gas pump (513) for injecting gas into the pressure regulating cavity (5) to increase P2.

8. The CO2 fluid nonwoven web entangling system based on gradient pressure regulation and targeted phase change according to claim 7, characterized in that: The second bottom plate (51) is provided with an air outlet hole (512) connected with a vacuum air extraction device (514) for extracting air from the pressure regulating cavity (5) to reduce P2.

9. The CO2 fluid nonwoven web entanglement system based on gradient pressure regulation and targeted phase change of claim 8, wherein: The phase change triggering cavity (4) is internally provided with a pressure sensor (7).

10. The CO2 fluid nonwoven web entanglement system based on gradient pressure regulation and targeted phase change of any of claims 1-9, wherein: The nozzle (2) comprises an inlet section (21), a primary pressurizing section (22), a flow stabilizing section (23) and an outlet focusing section (24) connected in sequence from top to bottom. The primary pressurizing section (22) is a tapered conical channel; the flow stabilizing section (23) is a cylindrical straight channel; and the outlet focusing section (24) is a streamline converging channel or a conical channel.

Images