A cross-critical co2 two-phase flow ejector

Abstract

This invention proposes a transcritical CO2 two-phase flow ejector with permeability, belonging to the field of ejector technology. It includes a mixing chamber and a nozzle. The mixing chamber is connected to an active inlet, and the nozzle is located at one end of the active inlet within the mixing chamber. A selectively permeable membrane is connected to the bottom of the active inlet. This allows lubricating oil in the working fluid to pass through the selectively permeable membrane to the outside of the ejector, while simultaneously preventing CO2 from passing through. The inner wall of the active inlet is a micro-nano composite structure, consisting of alternating smooth regions and comb-shaped groove regions. The working fluid enters the active inlet and flows on the surface of the micro-nano composite structure. The comb-shaped groove regions act on the lubricating oil in the working fluid, driving the lubricating oil through the smooth regions to the selectively permeable membrane. This invention effectively discharges lubricating oil from the ejector, solving the problem of lubricating oil accumulation on the ejector surface under high dryness conditions, which leads to a decrease in heat transfer performance.

Description

Technical Field

[0001] This invention belongs to the field of ejector technology, specifically a transcritical CO2 two-phase flow ejector with passability. Background Technology

[0002] Zhu Yinhai and others from Tsinghua University established a theoretical model of a non-equilibrium phase change-related transcritical CO2 ejector, conducted experimental research on the ejector performance, performed a visualization study on the two-phase flow inside the ejector, and calculated and analyzed the distribution of shock waves and Mach number inside the ejector.

[0003] Liu Heng conducted numerical simulations of a transcritical two-phase CO2 ejector. Based on a homogeneous flow model, he proposed a suitable model for the CO2 phase change within the ejector, as well as a sound velocity model. He also proposed new solutions for CO2 properties. Simulation results show that the constructed simulation method can accurately simulate the internal flow field of the ejector with an error within 5%. Furthermore, the characteristics of shock waves generated by the fluid at high Mach numbers were also obtained.

[0004] Researchers also conducted measurements on lubricating oil leakage in transcritical CO2 heat pumps. (Liu Shengchun, Tianjin University) [7] Researchers conducted experimental studies and theoretical calculations on the lubricating oil leakage of transcritical CO2 heat pumps, which indirectly reflected the oil content of carbon dioxide in the heat pump. The study found that the amount of lubricating oil leakage changed when the lubricating oil in the system changed from 9.6 g / s to 14.1 g / s under different pressures and gaps, providing a reference for equipment design.

[0005] Defects and shortcomings of existing technology:

[0006] In current transcritical CO2 heat pump systems, the highest temperature in the system is far below the boiling point of the lubricating oil, which always exists in a liquid state. Under high dryness conditions, lubricating oil accumulates on the injector surface, increasing its adverse effects on heat transfer and significantly impacting the injector's ejection performance and heat exchange. Summary of the Invention

[0007] This invention overcomes the shortcomings of the prior art and proposes a transcritical CO2 two-phase flow ejector with passability; it solves the problem that lubricating oil accumulates on the ejector surface under high dryness conditions, leading to a decrease in heat transfer performance.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution.

[0009] A transcritical CO2 two-phase flow ejector with permeability includes a mixing chamber and a nozzle. The mixing chamber is connected to an active inlet and an ejector inlet. The nozzle is located at one end of the active inlet in the mixing chamber and is used to inject a high-pressure working fluid. The mixing chamber is used to mix the working fluid and the ejector fluid to form a mixed fluid. A selectively permeable membrane is connected to the bottom of the active inlet. The lubricating oil in the working fluid is discharged to the outside of the ejector through the selectively permeable membrane, while the selectively permeable membrane prevents CO2 from passing through. The inner wall of the active inlet is a micro-nano composite structure. The micro-nano composite structure consists of alternating smooth areas and comb-shaped groove areas. The working fluid enters the active inlet and flows on the surface of the micro-nano composite structure. The comb-shaped groove areas act on the lubricating oil in the working fluid, driving the lubricating oil through the smooth areas to flow to the selectively permeable membrane.

[0010] Furthermore, a collection device is connected to the bottom of the active inlet, and a selectively permeable membrane is provided at the connection between the collection device and the active inlet.

[0011] Furthermore, the selectively permeable membrane is a zirconia ceramic modified membrane.

[0012] Furthermore, the micro-nano composite structure is distributed on the inner surface from the active inlet to 6 mm in front of the nozzle.

[0013] Furthermore, the nozzle is connected to an adjusting nozzle; the outer surface of the adjusting nozzle is the aforementioned micro-nano composite structure.

[0014] Furthermore, the comb-shaped groove region is prepared using one of the following materials: organosilicon, silicon-based nanolayer, organosilicon nanocoating, or organosilicon resin.

[0015] Furthermore, the lengths of the smooth area and the comb-shaped groove area are set along the inner wall length of the active inlet and the outer wall length of the adjusting nozzle. The width of each smooth area is 500μm, and the width of each comb-shaped groove area is 1000μm. The depth of each groove in the comb-shaped groove area gradually increases from the tooth tip to the tooth root by 0.2μm - 2.2μm.

[0016] Furthermore, femtosecond laser direct writing technology is used to divide the inner wall of the active inlet and the outer wall of the adjusting nozzle into smooth areas and comb-shaped groove areas according to different chamber diameters.

[0017] Furthermore, the active inlet includes a vertical section and a horizontal section connected together. The front end of the horizontal section is connected to the nozzle. The area directly below the horizontal section of the active inlet is a smooth area. The micro-nano composite structure of the horizontal section is arranged symmetrically from left to right with the axial centerline as the center.

[0018] Furthermore, the mixing chamber is connected to the outlet diffuser chamber to pressurize and discharge the mixed fluid.

[0019] The beneficial effects of this invention compared to the prior art are as follows:

[0020] 1. This invention utilizes comb-shaped microgrooves to achieve an oil-repelling effect, forcing oil droplets to move towards the oleophilic region and causing the oil droplets to gather in the same position as much as possible, which is beneficial for subsequent oil drainage.

[0021] 2. This invention utilizes a zirconia ceramic membrane, which allows lubricating oil to pass through but rejects carbon dioxide, thus enabling the lubricating oil to be discharged effectively.

[0022] 3. The injector described in this invention is adjustable, and the area of ​​the nozzle throat is controlled by a needle valve, which facilitates the control of the injector's flow rate. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the transcritical CO2 two-phase flow ejector with passability as described in this invention;

[0024] Figure 2 This is a schematic diagram of a structure in which the active inlet inner wall lubrication zone and the comb-shaped groove zone are arranged alternately.

[0025] In the figure, 10-active inlet, 20-ejector inlet, 30-mixing chamber, 40-outlet diffusion chamber, 50-adjusting nozzle, 60-nozzle, 70-selective permeable membrane, 80-collecting device, 90-micro-nano composite structure, 901-smooth area, 902-comb-shaped groove area. Detailed Implementation

[0026] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail with reference to the embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. The technical solutions of this invention are described in detail below with reference to the embodiments and accompanying drawings, but the scope of protection is not limited thereto.

[0027] See Figure 1 and Figure 2This embodiment proposes a transcritical CO2 two-phase flow ejector with passability. The ejector is entirely made of metal and includes an active inlet 10, an ejector inlet 20, a mixing chamber 30, an outlet diffuser 40, an adjusting needle 50, and a nozzle 60. The side of the mixing chamber 30 is connected to the active inlet 10, with a portion of the active inlet 10 located outside and another portion inside the mixing chamber 30. The active inlet 10 is used for the entry of the working fluid. The nozzle 60 is located at the end of the active inlet 10 located inside the mixing chamber 30 and is used to inject high-pressure working fluid. The upper part of the mixing chamber 30 is connected to the ejector inlet 20, which is used to eject the fluid. The mixing chamber 30, nozzle 60, and ejector inlet 20 are connected to mix the working fluid and the ejected fluid to form a mixed fluid. The outlet diffuser 40 is connected to the mixing chamber 30 and is used to pressurize and discharge the mixed fluid. The adjusting needle 50 is located inside the nozzle 60 and is threadedly connected to adjust the position of the nozzle 60 relative to the mixing chamber 30. The throat area of ​​the nozzle 60 can be adjusted by adjusting the nozzle needle 50, thereby controlling the ejection ratio and thus the ratio of liquid and gaseous working fluid at the ejector outlet and the performance of the heat pump refrigeration cycle.

[0028] The most significant improvement in this embodiment is that a collection device 80 is connected to the bottom of the portion of the active inlet 10 located outside the mixing chamber 30, and a selective permeable membrane 70 is provided at the connection between the collection device 80 and the active inlet 10. The selective permeable membrane 70 is a zirconia ceramic modified membrane, which allows the lubricating oil in the working fluid to pass through the selective permeable membrane 70 and be discharged into the collection device 80, while at the same time preventing CO2 from passing through.

[0029] To promote the movement of lubricating oil toward the selective permeation membrane 70, this embodiment also improves the structure of the inner wall of the active inlet 10 and the outer wall of the adjusting nozzle 50, because the inner wall of the active inlet 10 and the outer wall of the adjusting nozzle 50 have the greatest contact with the working fluid; that is, a micro-nano composite structure 90 is provided on the inner wall of the active inlet 10 and the outer wall of the adjusting nozzle 50; in order not to affect the spraying of the nozzle 60, the micro-nano composite structure 90 on the active inlet 10 is distributed on the inner surface of the active inlet 10 to 6 mm in front of the nozzle 60.

[0030] The micro-nano composite structure 90 consists of alternating smooth regions 901 and comb-shaped groove regions 902. The working fluid enters the active inlet 10 and flows on the surface of the micro-nano composite structure. The comb-shaped groove regions 902 act on the lubricating oil in the working fluid, and the comb-shaped microgrooves act on the unbalanced surface force of the lubricating oil, causing the lubricating oil droplets to form an ellipsoidal crown shape when they are in a steady state, making it easier for the lubricating oil droplets to pass through the smooth regions 901 and flow to the selectively permeable membrane 70 quickly.

[0031] The lengths of the smooth area 901 and the comb-shaped groove area 902 are set along the inner wall of the active inlet 10 and the outer wall of the adjusting nozzle 50. Each smooth area 901 has a width of 500 μm, and each comb-shaped groove area 902 has a width of 1000 μm. The depth of each groove in the comb-shaped groove area 902 gradually increases from the tooth tip to the tooth root by 0.2 μm - 2.2 μm, and the tooth root width is approximately 40 μm. Due to the change in cross-sectional dimensions, the comb-shaped grooves significantly hinder the spread of liquid from the lubrication area, forming an apparent strip-shaped oleophilic surface.

[0032] The comb-shaped groove region 902 is prepared using one of the following materials: organosilicon, silicon-based nanolayer, organosilicon nanocoating, or organosilicon resin. In this embodiment, femtosecond laser direct writing technology is used to divide the surface equally according to different chamber diameters on the inner wall of the active inlet 10 and the outer wall of the adjusting nozzle 50 to form a smooth region 901 and a comb-shaped groove region 902.

[0033] During the processing, when machining the section from the transverse pipe of the active inlet 10 to 6mm before the nozzle 60, the area directly below the transverse pipe of the active inlet 10 should be a smooth zone 901. The machining should be performed symmetrically from left to right, centered on the axial centerline of the transverse pipe of the active inlet 10. A hole is drilled from the vertical projection of the inlet of the active inlet 10 down to the position of the transverse pipe of the active inlet 10, extending to the outside of the injector. A collection device 80 is installed outside the injector and connected to the hole. Simultaneously, a zirconia ceramic modified film is applied to the surface of the hole.

[0034] Zirconia ceramic modified films are prepared by the following methods:

[0035] 1. Dissolve trimethylchlorosilane in chloroform to form an organic precursor solution.

[0036] 2. The ceramic zirconia membrane was pretreated by immersing it in a 3 mol / L sodium hydroxide solution for 15 min, rinsed three times with deionized water, and then forced to dry at 150℃ for 2 h before cooling to room temperature for use.

[0037] 3. The pretreated ceramic zirconia membrane is completely immersed in the organic precursor solution prepared in the first step for modification. The modification time is 24 hours, and the ceramic zirconia membrane must be completely submerged.

[0038] 4. Rinse the modified ceramic zirconia film with deionized water 3 to 5 times until the organic solvent on the surface is completely cleaned.

[0039] 5. The modified ceramic zirconia film was heat-treated at 100℃ for 72 hours and then naturally cooled to room temperature.

[0040] The working process of the injector described in this embodiment is as follows:

[0041] Step 1: Supercritical CO2 carrying lubricating oil gas flow (primary flow) enters from active inlet 10, and low-pressure carbon dioxide (secondary flow) enters from ejector inlet 20.

[0042] Step 2: The high-pressure primary flow passes through the active inlet 10 and flows on the surfaces of two regions: the smooth region 901 and the comb-shaped groove region 902. The comb-shaped groove region 902 acts on the unbalanced surface force of the lubricating oil, promoting the lubricating oil to enter the smooth region 901. In steady state, it forms an ellipsoidal crown shape and flows to the position of the selective permeable membrane 70. It is then connected to the external collection device through the zirconia ceramic membrane, thereby discharging the lubricating oil.

[0043] The above description is a further detailed explanation of the present invention in conjunction with specific preferred embodiments. It should not be considered that the specific embodiments of the present invention are limited to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the present invention, and all of these should be considered to fall within the scope of patent protection determined by the submitted claims.

Claims

1. A transcritical CO2 two-phase flow ejector with passability, comprising a mixing chamber (30) and a nozzle (60), wherein the mixing chamber (30) is connected to an active inlet (10) and an ejector inlet (20); the nozzle (60) is disposed at one end of the active inlet (10) located in the mixing chamber (30) for ejecting a high-pressure working fluid, and the mixing chamber (30) is used to mix the working fluid with the ejector fluid to form a mixed fluid; characterized in that, The bottom of the active inlet (10) is connected to a selectively permeable membrane (70); the lubricating oil in the working fluid is discharged to the outside of the injector through the selectively permeable membrane (70), while the selectively permeable membrane (70) prevents CO2 from passing through; the inner wall of the active inlet (10) is a micro-nano composite structure (90); the micro-nano composite structure (90) consists of alternating smooth areas (901) and comb-shaped groove areas (902), the working fluid enters the active inlet (10) and flows on the surface of the micro-nano composite structure, the comb-shaped groove areas (902) act on the lubricating oil in the working fluid, driving the lubricating oil through the smooth areas (901) to flow to the selectively permeable membrane (70); the selectively permeable membrane (70) is a zirconia ceramic modified membrane.

2. A transcritical CO2 two-phase flow ejector with passability according to claim 1, characterized in that, A collection device (80) is connected to the bottom of the active inlet (10), and a selective permeable membrane (70) is provided at the connection between the collection device (80) and the active inlet (10).

3. A transcritical CO2 two-phase flow ejector with passability according to claim 1, characterized in that, The micro-nano composite structure is distributed on the inner surface from the active inlet (10) to 6 mm in front of the nozzle (60).

4. A transcritical CO2 two-phase flow ejector with passability according to claim 1, characterized in that, The nozzle (60) is connected to an adjusting nozzle (50); the outer surface of the adjusting nozzle (50) is the micro-nano composite structure (90).

5. A transcritical CO2 two-phase flow ejector with passability according to claim 1, 3, or 4, characterized in that, The comb-shaped groove region (902) is prepared using one of the following materials: organosilicon, silicon-based nanolayer, organosilicon nanocoating, or organosilicon resin.

6. A transcritical CO2 two-phase flow ejector with passability according to claim 4, characterized in that, The lengths of the smooth area (901) and the comb-shaped groove area (902) are set along the inner wall length of the active inlet (10) and the outer wall length of the adjusting nozzle (50). The width of each smooth area (901) is 500 μm, and the width of each comb-shaped groove area (902) is 1000 μm. The depth of each groove in the comb-shaped groove area (902) gradually increases from the tooth tip to the tooth root by 0.2 μm - 2.2 μm.

7. A transcritical CO2 two-phase flow ejector with passability according to claim 4, characterized in that, Using femtosecond laser direct writing technology, the inner wall of the active inlet (10) and the outer wall of the adjusting nozzle (50) are divided into smooth areas (901) and comb-shaped groove areas (902) according to different chamber diameters.

8. A transcritical CO2 two-phase flow ejector with passability according to claim 1, characterized in that, The active inlet (10) includes a vertical section and a horizontal section connected together. The front end of the horizontal section is connected to the nozzle (60). The area directly below the horizontal section of the active inlet (10) is a smooth area (901). The micro-nano composite structure (90) of the horizontal section is arranged symmetrically on the left and right with the axial center line as the center.

9. A transcritical CO2 two-phase flow ejector with passability according to claim 1, characterized in that, The mixing chamber (30) is connected to the outlet diffusion chamber (40) for pressurizing and discharging the mixed fluid.

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