A pneumatic oil mist suction and separation device

Abstract

The present invention provides a pneumatic oil mist suction and separation device, comprising a pneumatic suction module, a circulation condensation module, an oil mist separation module, and a reflux recovery module; the purpose is to structurally improve the existing pneumatic oil mist suction and separation device, and provide a pneumatic oil mist suction and separation device that can instantly and efficiently separate oil droplets while sucking oil mist, thereby solving the difficulties of the existing device such as difficult installation, long oil mist processing time, and low separation efficiency.

Description

Technical Field

[0001] The present invention relates to the field of oil mist purification and separation of lubricating oil systems in large equipment such as compressors, and in particular to a pneumatic oil mist suction and separation device externally connected to a lubricating oil tank to suck lubricating oil vapor escaping from an exhaust port. Background Art

[0002] Oil mist extraction and separation devices play a crucial role in the petrochemical industry. Their effectiveness directly impacts the lifespan and performance of compressor equipment, impacting the company's economic profitability and significantly impacting the environment. Two technologies are commonly used to remove oil mist in industry: electric-driven oil mist treatment, such as fan oil mist treatment devices, and pneumatic oil mist treatment, which utilizes pneumatic demisting systems. Fan oil mist treatment devices operate by using motor-driven technology to extract oil mist from the lubricating oil tank using the suction force of the fan. The oil mist is then separated into gas and liquid through a separator.

[0003] However, relying on the suction power of a fan to extract oil mist can pose a safety hazard due to the fact that the fan is an electrical device and is surrounded by an oil mist environment. Currently, the most widely used pneumatic demisting systems in industry utilize Venturi tubes as their core component. Existing pneumatic demisting devices worldwide demonstrate excellent oil mist extraction and separation performance. Therefore, utilizing Venturi tube pneumatic demisting technology to extract and separate oil mist is an inevitable trend in addressing the issue of lubricant mist escaping from large machinery.

[0004] As an alternative to electric blowers, another problem with the current pneumatic demisting system using Venturi tube pneumatic demisting technology is that the simple suction separation function is effective, but the subsequent real-time separation of oil droplets in the mixed fluid is poor, especially when a large amount of compressed air is mixed into the Venturi tube during suction, which dilutes the oil mist concentration, making the concentration of oil droplets in the sucked oil mist lower than that of air, increasing the difficulty of separation. Summary of the Invention

[0005] In view of the above-mentioned technical status quo, the purpose of the present invention is to structurally improve the existing pneumatic oil mist suction and separation device, and provide a pneumatic oil mist suction and separation device that can instantly and efficiently separate oil droplets while sucking oil mist, thereby solving the difficulties of existing devices such as difficult installation, long oil mist processing time, and low separation efficiency.

[0006] The technical solution adopted by the present invention is as follows: a pneumatic oil mist suction and separation device, comprising a pneumatic suction module, a circulation condensation module, an oil mist separation module, and a reflux recovery module;

[0007] The pneumatic suction module includes a mixing chamber, a contraction section, and a diffuser section connected in sequence. A nozzle is installed inside the mixing chamber, and the nozzle outlet is directed toward the throat between the contraction section and the diffuser section. The lower side of the mixing chamber is connected to an ejector pipe, which is connected to the oil tank to suck the oil mist in the oil tank into the mixing chamber.

[0008] The circulation condensation module includes a gas-liquid distributor, an inner spiral channel, a guide pipe, a circulation baffle and a sleeve. The gas-liquid distributor is a cone-shaped cylinder, which is installed at the outlet end of the diffuser section and the small-diameter end of the cone faces the inlet of the guide pipe. The front end of the inner spiral channel is connected to the diffuser section, and the rear end is connected to the inlet end of the tapered section of the cyclone separation module. The wall shape of the inner spiral channel is limited to form a spiral flow channel; the guide pipe is coaxially installed inside the inner spiral channel, and the circulation baffle is installed inside the inner spiral channel corresponding to the outlet end of the guide pipe. The circulation baffle guides part of the fluid after passing through the guide pipe into the spiral flow channel of the inner spiral channel, and then flows back to the inlet end of the guide pipe to form a circulation; the sleeve is nested on the outer peripheral side of the inner spiral channel;

[0009] The oil mist separation module includes a tapered section, a straight pipe section and a gas-liquid separation section which are connected in sequence. The small-diameter end of the tapered section is connected to the straight pipe section, and the end of the straight pipe section is connected to the gas-liquid separation section. A central body composed of a hemisphere and a cone is arranged inside the tapered section. The cone angle is oriented towards the straight pipe section and the cone angle is the same as the cone angle of the tapered section, so as to form a tapered annular flow channel between the central body and the tapered section. The cone angle is fixedly connected to a swirl tail installed inside the straight pipe section. The gas-liquid separation section includes a drainage trough, fins and a gas discharge pipe. The drainage trough is a conical shell with a gradually expanding inner diameter. Its large-diameter end is connected to the gas discharge pipe. The fins are installed in the drainage trough and are located between the drainage trough and the gas discharge pipe.

[0010] The reflux recovery module includes a reflux pipe, a Y-type filter, and a Tesla valve. The reflux pipe is connected below the drain tank and is located on the upstream side of the fin. The Y-type filter is installed between the reflux pipe and the Tesla valve. The other end of the Tesla valve is connected to the return oil tank.

[0011] An air inlet pipe is also installed within the mixing chamber and connected to the nozzle inlet to direct working air provided by an external power system into the nozzle. The power system includes an air compressor, a buffer tank, and a flowmeter. The buffer tank buffers and separates the fluid from the air compressor, which is then passed through the flowmeter into the air inlet pipe.

[0012] Furthermore, the outlet end of the gas exhaust pipe is also connected to a gas-liquid cyclone separator with a collection tank. The gas-liquid cyclone separator separates the liquid in the incoming flow again to prevent incompletely separated gas from being discharged into the atmosphere. If the oil mist separator fails, the gas-liquid cyclone separator can ensure that the oil mist content in the exhaust gas is low, providing sufficient time for processing and maintenance.

[0013] Furthermore, a vertical baffle is installed inside the oil tank, which separates the interface position between the Tesla valve and the oil tank and the oil tank body to prevent the recovered lubricating oil droplets from being sucked into the mixing chamber by negative pressure; a guide plate is provided inside the oil tank at the interface position corresponding to the Tesla valve to guide the reflux oil droplets to flow back along the plate surface of the guide plate.

[0014] Preferably, the fin is a tapered conical shell, the diameter of which gradually decreases towards the drainage trough.

[0015] Preferably, a detachable filter element is installed in the Y-type filter, and the installation direction of the Tesla valve is to prevent the oil mist from escaping toward the Y-type filter.

[0016] Preferably, the semi-cone angle of the drainage trough is selected to be 10-20°, and the center line of the reflux pipe forms an angle of 5-10° with the horizontal line.

[0017] As a parallel technical solution, the circulating condensation modules are installed between the pneumatic suction module and the oil mist separation module in a manner of being used in parallel.

[0018] The technical solution of the present invention has the following technical advantages:

[0019] (1) Using industrial cold air as power to extract the oil vapor in the oil tank, the industrial site power source is convenient, and pneumatic defogger has fewer safety hazards than electric defogger, saving electricity and being more efficient. A nozzle is added at the inlet of the Venturi tube in the oil mist aspirator, which increases the negative pressure at the outlet of the ejector tube, accelerates the suction rate of the oil mist in the oil tank, shortens the oil mist processing time, and improves the efficiency of subsequent separation work.

[0020] (2) The circulation condensation module forms a circulation from the inside out, extending the fluid's residence time in the circulation zone. At the same time, the internal spiral channel increases the mixing degree of the fluid and ensures uniform heat exchange. The external cooling water sleeve strengthens the internal heat exchange, allowing the steam to fully condense into oil mist, thereby improving the subsequent oil mist separation efficiency. Furthermore, the number of circulation condensation modules can be increased or decreased according to the required lubricating oil vapor processing volume. Multiple circulation condensation modules can be set to work in parallel without interfering with each other, making operation very flexible.

[0021] (3) The device has a compact structure and occupies a small space. The outer surface of the outlet side of the expansion section of the venturi tube is provided with a thread, and the surface of the inlet side of the inner spiral channel is also provided with a thread. The inner spiral channels of different structures can be replaced. The internal and external threads cooperate with each other to make the structure easy to disassemble, easy to replace, easy to clean and troubleshoot, and save costs.

[0022] (4) A Y-type filter and a Tesla valve are sequentially arranged on the return pipe. The Y-type filter can replace different filter elements under different operating environments, and effectively filter out impurities in the separated and recovered lubricating oil, so that the recovered lubricating oil can directly enter the oil tank for recycling; the Tesla valve can prevent the oil vapor in the oil tank from being directly discharged along the return pipe, playing the role of one-way circulation. At the same time, the small oil droplets that are not completely separated are recovered along the return pipe and separated again, thereby improving the oil mist recovery rate.

[0023] (5) The device is equipped with a cyclone with a drainage trough on the gas outlet side to further separate and filter the discharged gas. When the oil mist separator of the device fails, it can ensure that the discharged gas has a lower oil content, thus buying time for maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 It is a schematic diagram of the overall structure of the pneumatic oil mist suction and separation device of the present invention;

[0026] Figure 2 This is a schematic diagram of the structure of the circulation condensation module in the present invention;

[0027] Figure 3 Schematic diagram of an embodiment of the inner spiral track in the present invention;

[0028] In the figure: 1. Air inlet pipe, 2. Nozzle, 3. Mixing chamber, 4. Ejector pipe, 5. Contraction section, 6. Diffuser section, 7. Gas-liquid distributor, 8. Inner spiral channel, 9. Guide pipe, 10. Casing, 11. Circulation baffle, 12. Circulation condensation module, 13. Gradual convergence section, 14. Center body, 15. Drain trough, 16. Fin, 17. Gas discharge pipe, 18. Oil mist separation module, 19. Return pipe, 20. Y-type filter, 21. Filter element, 22. Tesla valve, 23. Guide plate, 24. Baffle, 25. Oil tank, 26. Fixed pipe, 27. Air compressor, 28. Buffer tank, 29. Flow meter, 30. Gas-liquid cyclone separator. DETAILED DESCRIPTION

[0029] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0030] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0031] With reference to the accompanying drawings, the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for understanding and reading by those familiar with this technology. They are not used to limit the conditions for implementation of the present invention and therefore have no substantial technical significance. Any structural modification, change in proportional relationship, or adjustment in size, without affecting the efficacy and purpose of the present invention, should still fall within the scope of the technical content disclosed in the present invention. At the same time, the position limiting terms quoted in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments in their relative relationships, without substantially changing the technical content, should also be considered as the scope of implementation of the present invention.

[0032] like Figure 1 Figure 2 is a schematic diagram of the overall structure of the pneumatic oil mist suction and separation device of the present invention, which primarily comprises a pneumatic suction module, a circulating condensation module, an oil mist separation module, and a reflux recovery module. The pneumatic suction module is primarily comprised of a Venturi tube, which comprises a mixing chamber 3, a contracting section 5, and a diffuser section 6, connected in sequence. An air inlet pipe 1 connected to an external power system and a nozzle 2 are installed within the mixing chamber 3. The nozzle 2's outlet faces the throat between the contracting section 5 and the diffuser section 6. An ejector pipe 4 is connected below the mixing chamber 3 and is fixedly connected to the oil tank 25 via a fixing pipe 26. The ejector pipe 4 is preferably installed at a position corresponding to the nozzle 2's outlet. The power system introduces industrial cold air into the air inlet pipe 1, forming a negative pressure at the outlet of the nozzle 2, and sucking the oil mist in the oil tank 25 up through the ejector pipe 4. The oil mist and the industrial cold air are preliminarily mixed in the mixing chamber 3. After the Venturi effect of the contraction section 5 and the expansion section 6, the pressure of the mixed fluid decreases, the speed increases, the turbulent component inside the fluid increases, and the disturbance is intense, which is conducive to the cooling and condensation of the oil vapor.

[0033] The circulation condensation module 12 includes a gas-liquid distributor 7, an inner spiral channel 8, a guide tube 9, a circulation baffle 11 and a sleeve 10. The gas-liquid distributor 7 is installed at the end of the diffuser section 6 and is in the shape of a cone, with its small-diameter end facing the entrance of the guide tube 9. The front end of the inner spiral channel 8 is detachably connected to the diffuser section 6, such as a matching connection of internal and external threads, and the rear end of the inner spiral channel 8 is connected to the oil mist separation module 18. The inner wall surface of the inner spiral channel 8 is defined by its shape to form a spiral flow channel, which pre-swirls and remixes the mixed fluid flowing through. The guide pipe 9 is installed at the axis of the inner spiral channel 8, and its outlet end corresponds to the circulation baffle 11. Part of the fluid flowing out from the outlet of the guide pipe 9 enters the spiral flow channel between the inner spiral channel 8 and the guide pipe 9 under the action of the circulation baffle 11, and then flows back to the inlet end of the guide pipe 9 to form a circulation from the inside to the outside, which prolongs the fluid residence time. The sleeve 10 is nested on the outer peripheral side of the inner spiral channel 8, and cooling water is circulated to enhance mixed heat transfer and accelerate the condensation of lubricating oil vapor into oil mist.

[0034] The oil mist separation module 18 includes a tapered section 13, a straight pipe section, and a gas-liquid separation section. The large-diameter end of the tapered section 13 is detachably connected to the rear end of the inner spiral 8, and the small-diameter end of the tapered section 13 is connected to the straight pipe section. The end of the straight pipe section is connected to the gas-liquid separation section. A central body 14 composed of a hemisphere and a cone is provided inside the tapered section 13. The cone angle of the cone faces the straight pipe section and the cone angle is the same as the cone angle of the tapered section 13 to form a tapered annular flow channel between the central body 14 and the tapered section 13. The cone angle is fixedly connected to the swirl tail installed inside the straight pipe section. The swirl tail is a spirally extended metal wire. The swirl tail changes the fluid motion trajectory multiple times, causing small oil droplets inside the fluid to collide and coalesce into large oil droplets, and the oil mist is finally separated in the gas-liquid separation section. The gas-liquid separation section includes a drainage trough 15, fins 16, and a gas discharge pipe 17. The drainage trough 15 is a conical shell with a gradually expanding inner diameter, and its large-diameter end is connected to the gas discharge pipe 17. The fins 16 are arranged between the drainage trough 15 and the gas discharge pipe 17, and their diameter gradually decreases toward the drainage trough 15, blocking the incoming liquid and allowing the gas to pass over the fins 16 and enter the gas discharge pipe 17. Furthermore, the outer surface of the cone of the central body 14 can be provided with guide vanes with the same swirl-generating direction as the swirl tail to enhance the swirl intensity of the mixed fluid in the oil mist separation module.

[0035] The reflux recovery module includes a reflux pipe 19, a Y-type filter 20, and a Tesla valve 22. The reflux pipe 19 is connected below the drain trough 15 and is located on the upstream side of the fin 16 to discharge the oil droplets blocked by the fin 16. The outlet end of the reflux pipe 19 is connected to the Tesla valve 22 through the Y-type filter 20, and the outlet end of the Tesla valve 22 is connected to the oil return tank 25.

[0036] Fins 16 are fixedly connected to the junction of drain trough 15 and gas discharge pipe 17. Small oil droplets in the exhaust gas can adhere to fins 16 during fluid flow before flowing into return pipe 19, improving lubricant recovery. Furthermore, a gas-liquid cyclone separator 30 with a collection tank is fixedly connected to the outlet end of gas discharge pipe 17 to further separate the separated gas and prevent incompletely separated gas from being released into the atmosphere. If the oil mist separator malfunctions, the gas-liquid cyclone separator 30 ensures a low oil mist content in the exhaust gas, providing sufficient time for repairs.

[0037] A Y-type filter 20 is fixedly connected to the outlet side of the return pipe 19, which can remove impurities in the recovered lubricating oil and improve the purity of the lubricating oil. The filter element 21 in the Y-type filter 20 can be removed for cleaning or replacement after a period of use. The return pipe 19 is connected to the oil tank 25 after passing through the Tesla valve 22, allowing the recovered lubricating oil and incompletely separated gas to pass through, preventing the steam in the oil tank 25 from being discharged through the return pipe 19. Furthermore, at the connection between the Tesla valve 22 and the oil tank 25, a baffle 24 and a guide plate 23 are provided inside the oil tank 25. The baffle 24 can prevent the recovered lubricating oil droplets from being sucked into the Venturi tube by negative pressure, thereby avoiding ineffective recovery. The guide plate 23 can allow the oil droplets to flow from the return pipe along the plate surface into the oil tank, avoiding splashing of oil droplets.

[0038] See also Figure 2 , is a schematic diagram of the structure of the circulation condensation module in the present invention, which shows the flow state of the circular vortex when the gas-liquid mixed fluid flows through the circulation condensation module through arrows. The outlet of the gas-liquid distributor 7 is located at the center of the inlet of the guide pipe 9. When the gas-liquid distributor 7 passes the fluid into the guide pipe 9 and flows along the guide pipe 9, a part of the fluid enters the circulation pipe between the guide pipe 9 and the inner spiral channel 8 under the action of the circulation baffle 11 and flows in the reverse vortex. Since the middle speed at the inlet of the guide pipe 9 is fast and the peripheral flow velocity is small, a negative pressure is formed in the central part of the guide pipe 9. The negative pressure sucks the fluid from the circulation pipe around it to re-enter the guide pipe 9, thereby forming a circulation and prolonging the fluid residence time. The inner spiral channel 8 has an inward-protruding spiral channel, which promotes sufficient fluid mixing of cold and hot fluids. At the same time, under the cooling action of the outer sleeve 10, heat transfer is enhanced, and the condensation of steam into oil mist is accelerated. See Figure 2 The inlet end of the guide tube 9 is bent into an arc plate toward the inside, and the outlet end of the guide tube 9 is bent into an arc plate toward the outside, so as to more fully guide the mixed fluid to form a circular flow.

[0039] Figure 3Schematic diagram of an embodiment of the inner spiral channel in the present invention, showing six embodiments. In the cross section of the formed spiral channel, (a) is a wide sawtooth shape, (b) is a wide thread type, (c) is a wide thread type with a chamfered top angle, (d) is a narrow sawtooth shape, (e) is a narrow thread type, and (f) is a narrow thread type with a chamfered top angle. It is obvious to those skilled in the art that the above six embodiments are merely schematic examples of the specific circumstances of constructing the inner spiral channel 8, and do not limit the specific scope of the technical solution of the present invention. Those skilled in the art can further expand the shape of the inner spiral channel 8 based on the content disclosed in the present invention, such as a wavy line type, a broken line type, etc.

[0040] As a supporting device, the pneumatic oil mist suction and separation device of the present invention also includes a power system, which includes an air compressor 27, a buffer tank 28 and a flow meter 29. When working, the air compressor 27 provides working air, which is separated from the gas and liquid and buffered in the buffer tank 28 to form a 15°C power air that enters the air inlet pipe 1.

[0041] In the specific simulation experiment, the numerical settings are as follows: the nozzle inlet diameter is 13-15mm, the nozzle outlet diameter is 2.5-6mm, the nozzle length is 5mm, the horizontal length of the inlet and outlet of the drainage trough 15 in the oil mist separator 18 is 130mm, the busbar is at an angle of 10-20° to the horizontal plane, and the center line of the return pipe 19 is at an angle of 5-10° to the horizontal line. The pneumatic oil mist suction and separation device of the present invention demonstrates high suction efficiency and oil mist separation efficiency, and has certain practical value.

Claims

1. A pneumatic oil mist suction and separation device, comprising a pneumatic suction module, a circulating condensation module, a cyclone separation module, and a reflux recovery module; The pneumatic suction module includes a mixing chamber, a contraction section, and a diffuser section connected in sequence. A nozzle is installed inside the mixing chamber, and the nozzle outlet is directed toward the throat between the contraction section and the diffuser section. The lower side of the mixing chamber is connected to an ejector pipe, which is connected to the oil tank to suck the oil mist in the oil tank into the mixing chamber. The circulation condensation module includes a gas-liquid distributor, an inner spiral channel, a guide pipe, a circulation baffle and a sleeve. The gas-liquid distributor is a cone-shaped cylinder, which is installed at the outlet end of the diffuser section, and the small-diameter end of the cone faces the inlet of the guide pipe. The front end of the inner spiral channel is connected to the outlet end of the diffuser section, and the rear end is connected to the inlet end of the tapered section of the oil mist separation module. The wall shape of the inner spiral channel is limited to form a spiral flow channel; the guide pipe is coaxially installed inside the inner spiral channel, and the circulation baffle is installed inside the inner spiral channel corresponding to the outlet end of the guide pipe. The circulation baffle guides part of the fluid after passing through the guide pipe into the spiral flow channel of the inner spiral channel, and then flows back to the inlet end of the guide pipe to form a circulation; the sleeve is nested on the outer peripheral side of the inner spiral channel; The oil mist separation module includes a tapered section, a straight pipe section and a gas-liquid separation section which are connected in sequence. The small-diameter end of the tapered section is connected to the straight pipe section, and the end of the straight pipe section is connected to the gas-liquid separation section. A central body composed of a hemisphere and a cone is arranged inside the tapered section. The cone angle is oriented towards the straight pipe section and the cone angle is the same as the cone angle of the tapered section, so as to form a tapered annular flow channel between the central body and the tapered section. The cone angle is fixedly connected to a swirl tail installed inside the straight pipe section. The gas-liquid separation section includes a drainage trough, fins and a gas discharge pipe. The drainage trough is a conical shell with a gradually expanding inner diameter. Its large-diameter end is connected to the gas discharge pipe. The fins are installed in the drainage trough and are located between the drainage trough and the gas discharge pipe. The reflux recovery module includes a reflux pipe, a Y-type filter, and a Tesla valve. The reflux pipe is connected below the drain tank and is located on the upstream side of the fin. The Y-type filter is installed between the reflux pipe and the Tesla valve. The other end of the Tesla valve is connected to the return oil tank.

2. The pneumatic oil mist suction and separation device according to claim 1, characterized in that: An air inlet pipe is also installed in the mixing chamber, and the air inlet pipe is connected to the inlet of the nozzle to pass the working air provided by the external power system into the nozzle.

3. The pneumatic oil mist suction and separation device according to claim 1 or 2, characterized in that: The outlet end of the gas discharge pipe is also connected to a gas-liquid cyclone separator with a collection tank, and the gas-liquid cyclone separator separates the liquid in the incoming flow again.

4. The pneumatic oil mist suction and separation device according to claim 2, characterized in that: The power system includes an air compressor, a buffer tank and a flow meter. The buffer tank buffers and separates gas and liquid from the fluid from the air compressor, and then the fluid passes through the flow meter and enters the air inlet pipe.

5. The pneumatic oil mist suction and separation device according to claim 3, characterized in that: A vertical baffle is installed inside the oil tank, which separates the interface position between the Tesla valve and the oil tank and the oil tank body to prevent the recovered lubricating oil droplets from being sucked into the mixing chamber by negative pressure; a guide plate is provided inside the oil tank at the interface position corresponding to the Tesla valve to guide the reflux oil droplets to flow back along the plate surface of the guide plate.

6. The pneumatic oil mist suction and separation device according to claim 1, characterized in that: The fin is a tapered cone shell, the diameter of which gradually decreases toward the drainage groove.

7. The pneumatic oil mist suction and separation device according to claim 1, characterized in that: A detachable filter element is installed in the Y-type filter, and the installation direction of the Tesla valve is to prevent oil mist from escaping toward the Y-type filter.

8. The pneumatic oil mist suction and separation device according to claim 1, characterized in that: The semi-cone angle of the drainage trough is selected to be 10-20 degrees, and the center line of the reflux pipe forms an angle of 5-10 degrees with the horizontal line.

9. The pneumatic oil mist suction and separation device according to claim 1, characterized in that: The circulating condensation modules are installed between the pneumatic suction module and the oil mist separation module in a manner of being used in parallel.

10. The pneumatic oil mist suction and separation device according to claim 1, characterized in that: The cone outer surface of the central body is provided with guide vanes whose swirl-generating direction is the same as that of the swirl tail.

Images