Gas ejection nozzle, gas dissolution device, and gas dissolution method

Abstract

To provide a gas ejection nozzle which maintains high gas dissolution capacity by using a cavitation screw member and is also superior in self-priming capacity, and to provide a gas dissolution device and a gas dissolution method using the gas ejection nozzle.SOLUTION: A gas ejection nozzle 1 comprises: a nozzle body 2 in which a single liquid channel 11 having a liquid inlet 3 at one end and a liquid outlet 4 at the other end is formed, and in which a throttle part 9 is formed in the middle of the liquid channel 11 so as to have a smaller diameter than the liquid inlet 3; a cavitation screw member 10 disposed within the throttle part 9; and a gas dissolution diameter expansion part 13 which is connected to a downstream side of the throttle part 9 so as to form a part of the liquid channel 11, and which continuously or gradually expands an axial cross section toward the liquid outlet 4. A gas introduction hole 6 of the nozzle body 2 communicates with the throttle part 9 or the gas dissolution diameter expansion part 13 at a downstream side beyond all cavitation screw members 10 positioned within the throttle part 9, and is formed so as to connect an external part of the nozzle body 2 and the liquid path 11.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gas ejection nozzle, and a gas dissolving device and a gas dissolving method using the same. [Background technology]

[0002] Venturi ejectors (Patent Documents 1 and 2) are known as gas ejection nozzles for gas-liquid mixing. These gas ejection nozzles have a throttle section in the middle of the flow path, and a gas inlet hole at or directly below the throttle section. The gas supplied is entrained and mixed with the liquid flow, which accelerates at the throttle section. These gas ejection nozzles have the advantage of being free of obstacles within the throttle section and relatively low pressure loss, making it easy for gas to self-suck due to the decompression effect generated by the throttle. Meanwhile, Patent Document 3 discloses a gas ejection nozzle in which a screw member is installed upright at the throttle section of a Venturi-shaped nozzle body, and the gas is entrained and mixed in the cavitation turbulence generated downstream of the screw member. Because the cavitation turbulence produces a significant gas-liquid mixing effect, this gas ejection nozzle has the advantage of being able to demonstrate high liquid dissolving ability even when a relatively low liquid supply pressure is used. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-085237 [Patent Document 2] Japanese Patent Publication No. 2023-066081 [Patent Document 3] WO2016 / 195116 publication Summary of the Invention [Problem to be solved by the invention]

[0004] The venturi ejectors and orifice ejectors disclosed in Patent Documents 1 to 3 require a high liquid flow rate to fully utilize the self-priming ability of the gas, and the liquid supply pressure must be set considerably high to ensure a sufficient liquid flow rate in the throttle section with a large pressure resistance. As a result, there is a drawback in that the liquid delivery section, such as a pump, inevitably becomes larger.

[0005] Furthermore, in the gas ejection nozzle disclosed in Patent Document 3, the gas introduction hole opens upstream of the screw member for forming the cavitation point. With this structure, the following problems arise. (1) When the liquid flow collides with the screw member, a strong back pressure acts on the gas inlet hole, making it impossible to self-suck the gas. In fact, in the carbon dioxide gas dissolution test disclosed in Patent Document 3, carbon dioxide gas is forcibly injected into the gas inlet hole at a pressure (0.2 MPa) higher than the liquid delivery pressure (0.1 MPa). Therefore, a cylinder and a pump are necessary for pressurized gas delivery, which limits the types of use. (2) Because not only liquid but also gas is supplied from the upstream side of the screw, the liquid passes through the screw in a mixed phase with coarse bubbles, and the thread roots that come into contact with the coarse bubbles cannot function as cavitation points. As a result, compared to when only liquid is flowing, cavitation turbulence is less likely to occur, which can lead to a decrease in gas dissolution efficiency.

[0006] An object of the present invention is to provide a gas ejection nozzle that uses a cavitation screw member but has excellent gas self-suction ability and can achieve high gas dissolution capacity, as well as a gas dissolution device and gas dissolution method that use the same. [Means for solving the problem]

[0007] In order to solve the above problems, the gas ejection nozzle of the present invention comprises: a nozzle body in which a single liquid flow path is formed, the single liquid flow path having a liquid inlet at one end and a liquid outlet at the other end, and a throttle portion formed midway along the liquid flow path so that the diameter of the liquid flow path is smaller than that of the liquid inlet; a cavitation screw member disposed within the throttle portion, the cavitation screw member having a thread portion formed on its outer surface with a thread pitch of 0.20 mm or more and 0.40 mm or less, a thread root depth of 0.20 mm or more and 0.40 mm or less, and a nominal diameter of 1.0 mm or more and 2.0 mm or less; a gas dissolving expansion section that is connected to the downstream side of the narrowing section in a manner that forms a part of the liquid flow path and that expands in axial cross section area continuously or stepwise toward the liquid outlet, The nozzle body is provided with a gas introduction hole, which communicates with the throttling section or the gas dissolution expansion section downstream of all of the cavitation screw members located within the throttling section, and is formed to connect the outside of the nozzle body with the liquid flow path.

[0008] The gas dissolving device of the present invention comprises a nozzle body having a single liquid flow path formed therein with a liquid inlet at one end and a liquid outlet at the other end, and a throttle portion formed midway along the liquid flow path so that the diameter of the liquid flow path is smaller than that of the liquid inlet; a cavitation screw member disposed within the throttle portion and having a thread portion formed on its outer surface with a thread pitch of 0.20 mm to 0.40 mm, a thread root depth of 0.20 mm to 0.40 mm, and a nominal diameter of 1.0 mm to 2.0 mm; and a gas dissolving expansion portion that forms part of the liquid flow path and is connected to the downstream side of the throttle portion, and whose axial cross-sectional area expands continuously or stepwise toward the liquid outlet. the nozzle body is provided with a gas inlet hole, the gas inlet hole communicates with the constricted section or the gas-dissolving expansion section downstream of all of the cavitation screw members located within the constricted section, and the gas ejection nozzle is formed to connect the outside of the nozzle body with the liquid flow path; a liquid delivery section that delivers liquid to the liquid inlet of the nozzle body; and a gas supply section that supplies gas to the gas inlet hole of the nozzle body, and is characterized in that the gas is sucked into the liquid through the gas inlet hole based on the negative pressure generated downstream of the cavitation screw members in the liquid flow path, and the gas is entrained in the turbulence generated in the gas-dissolving expansion section and dissolved.

[0009] Furthermore, the gas dissolving method of the present invention comprises a nozzle body having a single liquid flow path formed therein with a liquid inlet at one end and a liquid outlet at the other end, and a throttle portion formed midway along the liquid flow path so that the diameter of the liquid flow path is smaller than that of the liquid inlet; a cavitation screw member disposed within the throttle portion and having a thread portion formed on its outer surface with a thread pitch of 0.20 mm to 0.40 mm, a thread root depth of 0.20 mm to 0.40 mm, and a nominal diameter of 1.0 mm to 2.0 mm; and a gas dissolving screw member connected to the downstream side of the throttle portion in a manner forming part of the liquid flow path and having an axial cross-sectional area that expands continuously or stepwise toward the liquid outlet. and an expanded diameter portion, the nozzle body having a gas introduction hole, the gas introduction hole being connected to the diameter portion downstream of the cavitation screw member located within the throttling portion and the gas dissolution expansion portion, the gas introduction hole being connected to the diameter portion and being formed to connect the outside of the nozzle body with the liquid flow path, the liquid is fed to the liquid inlet of the nozzle body, while gas is supplied to the gas introduction hole of the nozzle body, and the gas from the gas introduction hole is sucked into the liquid due to the negative pressure generated downstream of the cavitation screw member in the liquid flow path, and the gas is entrained in the turbulence generated within the gas dissolution expansion portion and dissolved. [Effects of the Invention]

[0010] The gas ejection nozzle of the present invention, which uses a cavitation screw member, maintains high gas dissolution capability while also exhibiting excellent gas self-suction capabilities. Furthermore, the gas dissolution device and gas dissolution method of the present invention use the gas ejection nozzle of the present invention to dissolve gas in liquid with high efficiency. In particular, gas-liquid mixing can be easily achieved without using a cylinder or pump for pressurizing the gas, allowing for a wider range of uses. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a cross-sectional view showing one embodiment of the gas ejection nozzle of the present invention. [Figure 2] 2 is an axial cross-sectional view of the throttle portion of the gas ejection nozzle of FIG. 1 at a position including the cavitation screw member. [Figure 3]FIG. 2 is a structural explanatory diagram showing a flow system according to a first example of the gas dissolving device of the present invention. [Figure 4] FIG. 10 is a structural explanatory diagram showing a flow system according to a second example of a gas dissolving device of the present invention. [Figure 5] FIG. 10 is an axial cross-sectional view showing a first modified example of the arrangement of the cavitation screw member in the throttle portion. [Figure 6] FIG. 10 is an axial cross-sectional view showing a second modified example of the arrangement of the cavitation screw member in the throttle portion. [Figure 7] FIG. 10 is an axial cross-sectional view showing a third modified example of the arrangement of the cavitation screw members in the throttle portion. [Figure 8] FIG. 2 is a cross-sectional view showing a first example of a gas ejection nozzle in which a gas-dissolving expanded diameter portion is formed into a cylindrical surface. [Figure 9] FIG. 10 is a cross-sectional view showing a second example of a gas ejection nozzle in which the gas-dissolving expanded diameter portion is formed into a cylindrical surface shape. [Figure 10] 1 is a graph showing the relationship between the cross-sectional area of ​​the throttling portion of the gas ejection nozzle in Table 1 and the average flow velocity at the position of the cavitation screw member when water is passed through at a hydrodynamic pressure of 0.1 MPa. [Figure 11] 1 is a graph showing changes in negative suction pressure generated in the gas introduction hole when water is passed through the throttle portions of the gas ejection nozzles Nos. 2 and 101 in Table 1 at various hydrodynamic pressures. [Figure 12] 1 is a graph showing characteristic curves of negative suction pressure generated in the gas introduction hole when water is passed through the throttle portions of the gas ejection nozzles Nos. 2 and 101 in Table 1 at various flow rates. [Figure 13] 1 is a graph showing changes in negative suction pressure generated in the gas introduction hole when water is passed through the throttle portions of the gas ejection nozzles Nos. 3 and 102 in Table 1 at various dynamic water pressures. [Figure 14] 1 is a graph showing characteristic curves of negative suction pressure generated in the gas introduction hole when water is passed through the throttle portions of the gas ejection nozzles Nos. 3 and 102 in Table 1 at various throttle flow rates. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described. 1 is a cross-sectional view of a gas ejection nozzle 1 constituting one embodiment of the present invention. The gas ejection nozzle 1 comprises a nozzle body 2 and a cavitation screw member 10. The nozzle body 2 is formed with a single liquid flow path 11 having a liquid inlet 3 at one end and a liquid outlet 4 at the other end. In addition, a throttle portion 9 having a smaller diameter than the liquid inlet 3 is formed midway along the liquid flow path 11. The nozzle body 2 is made of a resin such as PTFE, ABS, acrylic, or polyacetal, but metals such as stainless steel, brass, or aluminum alloys may also be used.

[0013] Joints 3F, 4F for connecting a liquid supply pipe and a liquid take-out pipe are formed in the portions of the nozzle body 2 that form the liquid inlet 3 and liquid outlet 4. In this embodiment, the joints 3F, 4F are formed with female threads (for example, tapered pipe threads such as R1 / 2), but these can be changed to other types of joints as appropriate depending on the size and joint shape of the pipe to be connected.

[0014] The cavitation screw member 10 (hereinafter simply referred to as the "screw member 10") is disposed within the constricted portion 9. As shown in FIG. 2, the leg portion of the cavitation screw member 10 has a threaded portion formed on the outer surface thereof. The threaded portion has a thread 31 with a pitch of 0.20 mm to 0.40 mm, a thread root 32 with a depth of 0.20 mm to 0.40 mm, and a nominal diameter M of 1.0 mm to 2.0 mm. In this embodiment, the screw member 10 is a JIS No. 0, Class 1 pan head machine screw (coarse pitch) made of metal, for example. However, the screw member 10 may also be made of inorganic materials such as alumina, zirconia, or glass. Stainless steel, titanium, or the like can be used as the specific material for the screw member 10 to ensure corrosion resistance. When used to dissolve corrosive gases such as ozone, the screw member 10 is preferably made of titanium or a titanium alloy. Furthermore, a screw member made of quartz can also be used for applications where even trace amounts of metal contamination are a problem, such as semiconductor applications.

[0015] In this embodiment, as shown in FIG. 2, the screw member 10 is screwed into the threaded hole 8 formed in the nozzle body 2 so that the tip protrudes from the outer peripheral surface of the wall into the constricted portion 9, but it may also be configured to be integrated with the nozzle body 2 by insert molding or the like.

[0016] Returning to FIG. 1 , a gas-dissolving expanded diameter section 13, whose axial cross-sectional area expands continuously (or stepwise: the configuration shown in FIG. 8 or FIG. 9 , described later) toward the liquid outlet 4, is connected to the nozzle body 2 downstream of the throttle section 9, forming part of the liquid flow path 11. A gas inlet hole 6 is formed in the nozzle body 2 downstream of all of the cavitation screw members 10 located within the throttle section 9, so as to communicate with the throttle section 9 (or the gas-dissolving expanded diameter section 13, described later) and to connect the outside of the nozzle body 2 with the liquid flow path 11. A female threaded hole 7, for attaching a gas inlet joint, is formed on the outer circumferential surface of the nozzle body 2, so as to communicate with the gas inlet hole 6. The inner diameter of the gas inlet hole 6 is, for example, 0.3 mm or more and 2 mm or less.

[0017] In this embodiment, the constriction section 9 has a cylindrical inner surface shape, and at its upstream end is formed an inlet taper section 5 that narrows in diameter from the liquid inlet 3 toward the constriction section 9 at a steeper angle than the gas dissolution expansion section 13.

[0018] 3 is a structural explanatory diagram showing the flow system of an example of a gas dissolution apparatus using the gas ejection nozzle 1 of FIG. 1. The gas dissolution apparatus 100 has a storage tank 50 and a main liquid pipe 101, on which a pump 55 constituting a liquid delivery section and the aforementioned gas ejection nozzle 1 are provided. One end of the main liquid delivery pipe 101 is connected to the storage tank 50, and the pump 55 pressure-feeds the liquid L in the storage tank 50 to the liquid inlet 3 (FIG. 1) of the gas ejection nozzle 1. On the main liquid delivery pipe 101, upstream of the gas ejection nozzle 1, a pressure gauge 110 for measuring the flow dynamic pressure of the liquid L relative to the gas ejection nozzle 1 and a flow meter 111 for measuring the flow rate of the liquid L are provided.

[0019] The liquid L may be, for example, water or water-based liquids (soft drinks such as juice, tea, coffee, lactic acid bacteria drinks, fruit juice, seawater, and other aqueous solutions), as well as alcoholic beverages, other alcoholic drinks, fossil fuels, organic solvents, and edible oils, but is not limited to these.

[0020] A gas supply main pipe 121 is connected to a gas introduction joint 15 attached to the female threaded hole 7 (FIG. 1) of the gas ejection nozzle 1, and the gas to be used for dissolution is supplied from a gas supply source 123 provided at the end of the gas supply main pipe 121. The gas supply source 123 can be selected, for example, as follows, depending on the type of gas to be used. (1) Oxygen: Pressure Swing Adsorption (PSA) oxygen generators, oxygen cylinders, etc. (2) Hydrogen: Electrolytic hydrogen generators, chemical hydrogen generators, hydrogen cylinders, etc. (3) Nitrogen: PSA nitrogen generator, nitrogen cylinder, etc. (4) Nitrogen-hydrogen mixed gas: A device that mixes the hydrogen and nitrogen generated in (2) and (3) through piping, a cylinder filled with the mixed gas, etc. (5) Ozone-containing gas (e.g., oxygen-ozone mixed gas, air-ozone mixed gas): Ozonizer (oxygen source is PSA oxygen gas generator, oxygen cylinder, air, etc.) (6) Carbon dioxide: fossil fuel combustion equipment, carbon dioxide cylinders, etc. (7) Ammonia: ammonia generators, ammonia cylinders, etc. (8) Air: air cylinder, air compressor. When the gas ejection nozzle 1 is self-sucking atmospheric air using its negative pressure suction capability, the gas inlet 6 functions as a gas supply unit.

[0021] A flow rate adjustment valve 124 for adjusting the gas supply flow rate to the gas ejection nozzle 1 and a flow rate / pressure measurement device 125 for monitoring the gas flow rate and gas supply pressure are provided on the main gas supply pipe 121. A measurement pipe 126 branches off from the main gas supply pipe 121 via a switching valve 122, and a negative pressure meter 127 is connected to the end of the measurement pipe. If measurement of the suction negative pressure is not required, the switching valve 122, the measurement pipe 126, and the negative pressure meter 127 can be omitted.

[0022] A relief pipe 104 branches off from the main liquid pipe 101 on the discharge side of the pump 55, and the liquid passing through the relief pipe 104 is returned to the storage tank 50. A flow rate adjustment valve 116 is provided on the relief pipe 104, and adjusting the aperture of the flow rate adjustment valve 116 makes it possible to change the dynamic water pressure and flow rate applied to the gas ejection nozzle 1. By changing the aperture of the flow rate adjustment valve 116 while referring to the reading of the flow meter 111, the flow rate through the relief pipe 104 can be adjusted, and ultimately the distribution flow rate of the liquid applied to the gas ejection nozzle 1 can be set to a desired value. Note that if no particular adjustment of the flow rate is required, the flow rate adjustment valve 116 and relief pipe 104 can be omitted.

[0023] In the gas dissolving apparatus 200 shown in Fig. 4, a water supply pipe 1005 is connected to a main liquid pipe 101 via a water supply valve 1010. The dynamic water pressure and the flow rate of tap water applied to the gas ejection nozzle 1 can be changed by adjusting the opening of the water supply valve 1010. In this case, the water supply valve 1010 constitutes the liquid delivery section, and the storage tank 50 and pump 55 in the configuration of Fig. 3 are omitted.

[0024] Returning to FIG. 3, downstream of the liquid outlet 4 (FIG. 1) of the gas ejection nozzle 1, the main liquid pipe 101 branches into a liquid extraction pipe 103 and a circulation pipe 105, which can be switched by a switching valve 117. The end of the circulation pipe 105 is connected to a storage tank 50. When the switching valve 117 is tilted to the liquid extraction pipe 103 side, the liquid L is circulated through the gas ejection nozzle 1, in a single pass, and when the switching valve 117 is tilted to the circulation pipe 105 side, the liquid L is circulated through the gas ejection nozzle 1. When only one of the single-pass circulation and the circulation circulation is adopted, it is possible to leave only one of the liquid extraction pipe 103 and the circulation pipe 105, and omit the other together with the switching valve 117.

[0025] The operation of the gas dissolving device 100 will now be described. The storage tank 50 is filled with the liquid L, and in the case of one-path circulation, the switching valve 117 is switched to the liquid outlet pipe 103 side and the pump 55 is operated. As a result, the liquid L in the storage tank 50 flows through the gas ejection nozzle 1 and then flows out from the end of the liquid outlet pipe 103. At this time, if the switching valve 122 is switched to the measurement pipe 126 side, the negative suction pressure generated in the gas inlet hole 6 of the gas ejection nozzle 1 can be measured by the negative pressure gauge 127. Next, the switching valve 122 is switched to the gas supply main pipe 121 side, and the opening of the flow rate adjustment valve 124 is adjusted while referring to the pressure and flow rate indication values ​​of the flow rate / pressure measurement device 125 to set the gas flow rate to a desired value.

[0026] When liquid is supplied to the gas ejection nozzle 1, the liquid flow is first rapidly throttled toward the throttle section 9 at the inlet tapered section 5. As shown in Figure 2, the liquid passes through the main flow region 21 formed between the cavitating screw member 10 and the inner circumferential surface of the throttle section 9, colliding with the cavitating screw member 10. As the liquid passes through the outer circumferential surface of the screw member 10, the flow forms a high-speed region in the thread roots 32 and a low-speed region in the threads 31. The high-speed region in the thread roots 32 becomes a negative pressure region according to Bernoulli's theorem, and bubbles FB are generated by cavitation, i.e., decompression deposition of dissolved air. Because the thread roots 32 are formed in multiple turns around the outer periphery of the screw member 10, this decompression deposition occurs simultaneously and violently in multiple thread roots 32 within the throttle section 9. Furthermore, as the liquid flow detours downstream of the screw member 10, numerous microvortices are generated, forming a strongly stirred region containing a high density of microvortices derived from Karman vortices around and immediately downstream of the screw member 10.

[0027] In Patent Document 3, a gas inlet hole is formed upstream of the screw member, and by introducing the gas to be dissolved therein, a multiphase flow of liquid and gas is supplied toward the screw member. However, the inventors' studies have revealed that in a structure in which the gas inlet hole is located upstream of the screw member, the back pressure generated when the liquid flow collides with the screw member is large, and the gas inlet hole has no self-priming ability. In fact, in Patent Document 3, gas dissolution cannot be achieved unless gas is injected into the gas inlet hole at a pressure (0.2 MPa) higher than normal pressure.

[0028] However, when using the gas ejection nozzle 1 with the structure shown in Figure 1, despite the presence of the threaded member 10, which acts as a flow obstruction, the gas inlet hole 6, which communicates with the throttled member 9 or the gas-dissolving expansion portion 13 downstream of the threaded member 10, exhibits a significant self-priming ability (negative pressure suction ability). As will be apparent from the test results described below, this self-priming ability is higher than that of a nozzle with a structure in which the threaded member 10 is omitted from the throttled member 9, and is characterized by its significant self-priming ability even under operating conditions with a relatively low liquid flow rate. As a result, not only can gas be smoothly supplied to the gas inlet hole 6 at a relatively low supply pressure, but the gas-liquid mixing action downstream of the threaded member 10 is effectively enhanced, significantly increasing the efficiency of gas dissolution in the liquid. Furthermore, as a result of the increased gas dissolution efficiency, it is possible to dissolve gas at a high concentration in the liquid even with the gas supply in a single pass, as described above.

[0029] The gas ejection nozzle 1 of the present invention is designed by intentionally providing the screw member 10, which causes pressure loss, in the throttle section 9 and forming the gas inlet hole 6 downstream of it, thereby significantly improving the gas self-priming ability compared to a typical gas ejection nozzle that does not have a screw member 10. As shown in FIG. 1, in the gas ejection nozzle 1, the gas inlet hole 6 is located downstream of the screw member 10, so the gas in the gas inlet hole 6 is less likely to be subjected to back pressure from the screw member 10. However, the above-described feature of the gas ejection nozzle 1 of the present invention cannot be technically explained simply by the fact that the effect of back pressure from the screw member 10 is eliminated by changing the position of the gas inlet hole 6.

[0030] For example, in the nozzle of Patent Document 3, not only liquid but also gas is supplied from the upstream side of the screw member. As a result, when liquid containing floating coarse bubbles passes through the screw member, the thread roots in contact with the bubbles cannot function as cavitation points. On the other hand, in the gas ejection nozzle 1 of the present invention, only liquid is supplied from the upstream side of the screw member 10, so that when the liquid passes through the screw member 10, the coarse bubbles immediately after supply do not come into contact with the thread roots 32 ( FIG. 2 ). As a result, all of the thread roots 32 formed in the screw member 10 can function well as cavitation points.

[0031] The thread roots 32 are aligned in the thrust direction of the screw leg within the axial cross section of the throttle section 9, and are less susceptible to interference from large bubbles of the supply gas immediately downstream of the screw member. This is thought to be why the high-speed localized flow generated in each thread root 32 tends to gather toward the center of the axial cross section. It is also possible that the micro-vortices generated in large numbers downstream of the screw member 10 reduce wall friction loss against the flow. From these facts, it is presumed that a region where the flow is even faster (central flow velocity boost region) is formed steeply in the central region of the axial cross section downstream of the screw member 10 than when the screw member 10 is not provided in the throttle section 9, resulting in a significant negative pressure suction effect and gas dissolution action.

[0032] Next, returning to FIG. 3, when the switching valve 117 is switched to the circulation pipe 105 side and the pump 55 is operated, the liquid L in the storage tank 50 flows through the gas ejection nozzle 1 and then returns to the storage tank 50 via the circulation pipe 105. As a result, the liquid circulates through the gas ejection nozzle 1 while repeatedly mixing and stirring the gas introduced from the gas inlet hole 6. This makes it possible to obtain a liquid with a higher concentration of dissolved gas than in the case of a single-pass flow.

[0033] Additional technical requirements for the gas ejection nozzle 1 of the present invention are described in detail below. To increase the flow velocity in the thread root, enhance the negative pressure suction effect that contributes to the self-priming ability of the gas ejection nozzle 1, and improve gas dissolution efficiency, it is essential to ensure a sufficient average flow velocity in the throttle section 9. On the other hand, from the perspective of achieving the effect of improving the gas self-priming ability while maintaining a relatively low liquid supply pressure, it is desirable to set an appropriate upper limit for the average flow velocity in the throttle section 9. The average flow velocity at the position of the cavitation screw member in the throttle section 9 is desirably 9 m / s or greater. If the average flow velocity is less than 9 m / s, the negative pressure suction ability and gas dissolution efficiency may not be significant.

[0034] When water is supplied to the liquid inlet 3 of the nozzle body 2 with the liquid outlet 4 open and at a dynamic water pressure of 0.1 MPa, equivalent to the pressure of a typical tap water supply, the inner diameter of the axial cross section of the throttle portion 9 is desirably set to a range of 2.0 mm to 8.0 mm to obtain an average flow velocity in the above range at, for example, 1 L / min to 35 L / min. Furthermore, the inner diameter of the axial cross section of the throttle portion 9 is desirably set to a range of 3.5 mm to 8.0 mm to obtain an average flow velocity in the above range at a relatively large flow rate, for example, 4 L / min to 25 L / min. There is no upper limit to the average flow velocity at the position where the cavitation screw member is disposed in the throttle portion 9. However, since the pressure loss in the throttle portion increases as the inner diameter of the throttle portion 9 decreases, the limit to the average flow velocity due to the decrease in the inner diameter is considered to be approximately 13 m / s to 14 m / s.

[0035] As shown in Fig. 2, the average flow velocity in the throttle section 9 is calculated by dividing the measured liquid flow rate ρ by the cross-sectional flow area S obtained by subtracting the area of ​​the projected region of the screw member 10 from the total cross-sectional area of ​​the throttle section 9. For example, when the screw member 10 is arranged as shown in Fig. 2, the inner diameter of the throttle section 9 is d, the nominal diameter of the screw member 10 is M, the pitch of the thread is p, and the depth of the thread root is W, then the cross-sectional flow area S is S=(d / 2) 2 π-(MW) d It can be calculated as follows.

[0036] The reasons for setting the numerical ranges of the thread pitch and thread root depth of the cavitation screw member 10 as described above are as follows. First, if the thread root depth is less than 0.2 mm, the cavitation effect (the bubble precipitation effect due to reduced pressure of dissolved gas) necessary for forming a strong stirring region for gas dissolution becomes insignificant. Furthermore, if the thread root depth is insufficient, the local flow velocity at the thread root position cannot be sufficiently ensured, which also leads to a loss of self-priming ability generated in the gas inlet hole 6.

[0037] On the other hand, if the thread root depth is 0.40 mm or greater, the improvement in the cavitation effect plateaus. If the thread pitch is increased to 0.40 mm or greater, the number of thread roots per unit length of the thread stem decreases, and the number of thread roots within the cross section of the constricted portion may not be sufficient. Therefore, in the present invention, the thread pitch and thread root depth are set to 0.20 mm or greater and 0.40 mm or less. Furthermore, to ensure the strength of the threaded member, to prevent the constricted portion from being excessively occupied by the threaded member, and to ensure sufficient liquid flow even with normal fluid supply pressures similar to tap water pressure, the nominal diameter of the threaded member is set to 1.0 mm or greater and 2.0 mm or less. This range of nominal diameter values ​​roughly corresponds to the range of nominal thread diameters for JIS coarse pitch threads, which covers the above-mentioned thread pitch and thread root depth. It is even more preferable that the threaded portion of the cavitation threaded member 10 has a thread pitch of 0.28 mm or greater and 0.32 mm or less, and a thread root depth of 0.28 mm or greater and 0.32 mm or less.

[0038] Furthermore, in order to enhance the negative pressure suction effect downstream of the thread roots, it is desirable to ensure an appropriate area density of the thread roots 32 (cavitation points), which serve as speed-up points. If the radial flow velocity distribution in the axial cross section of the throttle section 9 on the upstream side of the threaded member 10 is assumed to be parabolic, with the maximum flow velocity value at the center of the cross section, the flow velocity will decrease to 50% of the maximum flow velocity value at the 70% radius position. Therefore, it is considered technically reasonable to consider the thread roots located within 70% radius from the center in the axial cross section of the throttle section 9 as thread roots that significantly contribute to the formation of a central flow velocity boost region and, therefore, to the improvement of the negative pressure suction effect.

[0039] Specifically, as shown in FIG. 2, when the number of thread valley points of the cavitating screw member 10 existing within 70% of the radius from the center in the axial cross section of the throttle portion 9 is defined as the 70% valley point number, the value of the 70% valley point area density, which is the value obtained by dividing the 70% valley point number by the flow cross-sectional area S, is 1.00 pieces / mm 2 More than 5.60 / mm 2 If the 70% valley point area density is less than the above-mentioned lower limit, the absolute number of thread valleys 32 that exert the effect of locally increasing the flow velocity will be insufficient, and if it exceeds the upper limit, excessive thread valleys 32 will be arranged, resulting in significant turbulence. In either case, the formation of a central flow velocity boost region will be hindered, and the negative pressure suction effect may be insufficient.

[0040] Next, in the configuration shown in FIG. 2 , the cavitation screw member 10 is arranged in the diametric direction of the axial cross section of the throttle portion 9. This is because the flow velocity distribution within the throttle portion 9 increases toward the center of the cross section, which has the advantage of making it easier to form the thread roots 32 through which liquid is supplied at a higher flow velocity. In this case, it is more preferable to arrange the cavitation screw member 10 along a predetermined diameter of the axial cross section of the throttle portion 9 so that the length of the leg of the screw member 10 located within the throttle portion 9 is greater than the radius of the throttle portion 9. This ensures that the thread roots 32 are located near the center of the axial cross section of the throttle portion 9, where the flow velocity is highest, thereby achieving a more pronounced self-priming effect of gas. This is presumably because the formation of a central flow velocity boost region by the thread roots 32 becomes more pronounced. From the perspective of enhancing the self-priming effect of gas, it is desirable that the cavitation screw member 10 does not have any voids formed along the diameter, as shown in FIG. 2 , and that the leg located within the throttle portion 9 spans the entire diameter of the axial cross section of the throttle portion 9.

[0041] Although there is a possibility that the gas self-priming effect or gas dissolution efficiency may be somewhat impaired, it is also possible to adopt a configuration in which two screw members 10 are used to form a gap 215 near the center of the cross section in the diameter direction, or a configuration in which a gap 215 is formed between the tip of the leg of the screw member 10 and the inner circumferential surface of the throttle portion 9, as shown in Fig. 6. Also, as shown in Fig. 7, it is also possible to adopt a configuration in which four screw members 10 are arranged in a cross shape along two diameters that are perpendicular to each other, to form a square-shaped gap 215 near the center of the cross section.

[0042] Returning to FIG. 1 , the gas-dissolving expansion section 13 is formed as a tapered surface whose axial cross-sectional area continuously increases with increasing distance downstream from the throttle section 9. The gas inlet hole 6 communicates with the liquid flow path 11 within section B, which extends from the downstream edge of the outer circumferential surface of the cavitation screw member 10 located within the throttle section 9 to a position on the inner circumferential surface of the gas-dissolving expansion section 13 where the cross-sectional diameter is 1.5 times (1.5d) the inner diameter d of the throttle section 9. By forming the gas-dissolving expansion section 13 as a tapered surface, a swirling flow is easily generated along the inner circumferential surface of the tapered surface in the liquid that passes through the cavitation screw member 10 and enters the gas-dissolving expansion section 13. The formation of this swirling flow further enhances the self-priming effect of the gas and further increases the dissolution efficiency of the gas introduced through the gas inlet hole 6 into the liquid. This is thought to be due to the swirling flow suppressing the outward radial diffusion of the flow within the gas-dissolving expansion section 13, resulting in a more sharply defined central flow velocity boost region.

[0043] In the above configuration, the negative pressure suction effect may not be sufficiently achieved downstream of the position where the gas introduction hole 6 is 1.5 times the inner diameter d of the constricted section 9 (downstream of section B in FIG. 1). In FIG. 1, the gas introduction hole 6 opens into the constricted section 9, but as shown by the dashed line in the figure, the gas introduction hole 6 may open into the gas dissolution expansion section 13 as long as it is within section B.

[0044] When the gradient angle of the inner peripheral surface of the gas dissolution expansion section 13 relative to the center line of the constricted section 9 is θ, the gas self-suction ability of the gas inlet hole 6 is further dramatically improved by making the gas dissolution expansion section 13 an expansion tapered surface in which the gradient section with tan θ of 0.04 to 0.14 accounts for 90% or more of the section length of the gas dissolution expansion section 13. This is thought to be because the formation of a swirling flow for gas dissolution becomes extremely pronounced when the gradient angle θ of the inner peripheral surface of the gas dissolution expansion section 13 is set gradual within the above range.

[0045] In the above configuration, if tan θ is 0.14 or more, the pressure loss due to expansion increases, and a significant improvement in gas self-priming capacity cannot be expected. The reason why the gradient section with a small tan θ is set to 90% or more of the length of the gas-dissolving expansion section 13 is that applying a section with a small tan θ to only a small portion of the gas-dissolving expansion section 13 and using a tapered surface or stepped surface with a steeper gradient for the remaining expansion area would not improve gas self-priming capacity. In the configuration of Figure 1, tan θ is set constant within the range of 0.04 to 0.14 throughout the entire gas-dissolving expansion section 13. However, an expansion section with a tan θ outside the above range may be added to the end of the expansion side of the gas-dissolving expansion section 13 as long as it is less than 10% of the length of the gas-dissolving expansion section 13.

[0046] 1, the inner peripheral surface of gas-dissolving expanded diameter portion 13 can be made into a cylindrical surface 13' without tapering (i.e., tan θ = 0), as shown in Fig. 8, for example, and a certain level of gas self-suction capacity can be expected. That is, gas-dissolving expanded diameter portion 13 can be formed as an expanded diameter cylindrical surface whose diameter expands discontinuously (i.e., in stages) from throttle portion 9, and gas inlet hole 6 can be configured to communicate with liquid flow path 11 within throttle portion 9 or at the boundary between throttle portion 9 and gas-dissolving expanded diameter portion 13.

[0047] In this case, the connection between the throttle section 9 and the gas-dissolving expansion section 13 forms an orifice-like stepped surface. The expansion from the throttle section 9 to the gas-dissolving expansion section 13 is discontinuous compared to the configuration shown in Figure 1, and the swirling flow generated on the inner surface of the gas-dissolving expansion section 13 is less pronounced compared to when a tapered inner surface with a continuous expansion is used. It is also thought that the region where the central flow velocity is boosted due to the expansion is limited to the gas inlet hole 6 near the boundary between the throttle section 9 and the gas-dissolving expansion section 13. In the configuration shown in Figure 8, the gas inlet hole 6 is opened at the connection position between the throttle section 9 and the gas-dissolving expansion section 13, but it is also possible to open the gas inlet hole 6 in the throttle section 9, as shown in Figure 9. [Example]

[0048] Various tests were carried out below to confirm the effects of the present invention. Example 1 Various test gas ejection nozzles (hereinafter referred to as "test nozzles") were fabricated with the shapes shown in Figures 1 and 8. The nozzle body 2 was made of PTFE resin and was machined into a cylindrical shape with an outer diameter of 30 mm and a length of 76 mm. The inlet tapered section 5 had an axial length of 2 mm, and the opening inner diameter of the liquid inlet 3 was 20 mm. The gas-dissolving expanded diameter section 13 had an axial length L of 24 mm, and the opening inner diameter on the liquid outlet 4 side was 20 mm. The length of the constricted section 9 was 10 mm, and the inner diameter d was variously set between 2.2 mm and 8.0 mm, as shown in Table 1.

[0049] For the test nozzles numbered 1, 101, and 102 in Table 1, the shape of the gas-dissolving expansion portion 13 was a cylindrical surface without a taper as shown in Figure 8, and the slope angle θ of the inner peripheral surface relative to the center line of the constricted portion 9 was zero (i.e., tan θ = 0). The connection between the constricted portion 9 and the gas-dissolving expansion portion 13 was an orifice-shaped stepped surface. For the test nozzles numbered 2 to 20 and 103 and 104, the inner surface of the gas-dissolving expansion portion 13 was the expansion tapered surface shown in Figure 1, and the slope angle θ of the expansion tapered surface was set to various values ​​of tan θ between 0.042 and 0.197.

[0050] The cavitation screw member 10 is a No. 0, Class 1 pan head machine screw with a metric coarse pitch as specified in JIS:B0205 (1997) and is made of stainless steel (SUS304). The cavitation screw members 10 used have nominal thread diameters of M1.0 (thread pitch: 0.25 mm, screw head outer diameter: 1.8 mm), M1.2 (thread pitch: 0.25 mm, screw head outer diameter: 1.8 mm), M1.4 (thread pitch: 0.30 mm, screw head outer diameter: 2.0 mm), and M1.6 (thread pitch: 0.35 mm, screw head outer diameter: 2.4 mm). For the test nozzles numbered 1 to 17 and 20 in Table 1, only one cavitation screw member 10 was placed across the entire diameter of the axial cross section, as shown in Figure 2. On the other hand, for test nozzle No. 18, four M1.4 threaded members were arranged in a cross shape in the diametrically orthogonal directions in the layout shown in Figure 7. The spacing of the gaps 215 was 1.4 mm. For test nozzle No. 19, two M1.4 threaded members were arranged in a diametrical direction in the layout shown in Figure 5. The spacing of the gaps 215 was 1.4 mm.

[0051] The gas inlet 6 has an inner diameter of 1.0 mm and is opened at the connection position of the throttle section 9 and the gas-dissolving expanded diameter section 13 so that its central axis is parallel to that of the cavitation screw member 10. The opening position of the gas inlet 6 is 2 mm downstream of the cavitation screw member 10 in terms of the distance between the central axes. Note that the test nozzles numbered 101 and 102 and the test nozzles numbered 103 and 104 are comparative examples in which the cavitation screw member 10 is omitted.

[0052] In addition, the number of 70% valley points N inside the reference circle was counted on a projected image showing the layout of the screw member 10 inside the constriction section 9, and the value of the 70% valley point area density β was calculated for each test nozzle by dividing this by the flow cross-sectional area S of the constriction section 9. The values ​​of the inner diameter d of the constriction section, the flow cross-sectional area S, the 70% valley point number N, and the 70% valley point area density β of each test nozzle are summarized in Table 1.

[0053] Each test nozzle was installed in the gas dissolution device 100 shown in Figure 3, and the storage tank 50 (volume: 20 L) was filled with tap water at 20°C. The selector valve 117 was then shifted to the circulation pipe 105 side to operate the pump 55 (Tohshin Technical vane pump: TVP-MS1803-A). While checking the reading on the pressure gauge 110, the opening of the flow control valve 116 was adjusted appropriately to set the dynamic water pressure applied to the test nozzle to 0.1 MPa. The selector valve 122 was then shifted to the measurement pipe 126 side, and the negative suction pressure generated in the gas inlet hole 6 of the test nozzle was measured with the negative pressure gauge 127 without gas being supplied. The flow rate of tap water flowing through the test nozzle was measured with the flow meter 111, and the average flow velocity at the position of the screw member in the throttle section 9 was calculated based on the measured value and the cross-sectional area of ​​each test nozzle. The results are summarized in Table 1.

[0054] [Table 1]

[0055] It can be seen that the test nozzles Nos. 1 to 20, which are examples of the present invention, all generated higher negative suction pressure values ​​than the test nozzles Nos. 101 to 104, which are comparative examples that do not use a cavitation screw member. In these test nozzles, the throttle section 9 had a flow rate of 1 L / min to 35 L / min and an average flow velocity of 9 m / sec to 13.5 m / sec when water was supplied to the liquid inlet 3 of the nozzle body 2 at a supply dynamic pressure of 0.1 MPa. Furthermore, the inner diameter of the axial cross section of the throttle section 9 was φ2.0 mm to φ8.0 mm, and all test nozzles achieved a good negative suction pressure value of -0.06 MPa or less.

[0056] In order to ensure a good suction negative pressure, it is desirable that the average flow velocity at the cavitation screw position be larger at the same liquid supply dynamic pressure. Figure 10 is a graph showing the relationship between the flow cross-sectional area of ​​the throttle section of the test nozzle in Table 1 and the average flow velocity at the cavitation screw position when water is passed through at a dynamic pressure of 0.1 MPa. 2In the region where the above is ensured, the average flow velocity at the position where the screw member 10 is disposed is approximately constant at 12.5 to 12.6 m / sec. However, in the region where the flow cross-sectional area S of the throttle portion is smaller than this, the average flow velocity starts to decrease due to an increase in flow pressure loss, and especially when the flow cross-sectional area S of the throttle portion is 3 mm 2 The average flow velocity decreases significantly in the region where the flow cross-sectional area S of the constricted section is less than 3 mm 2 Above 8mm, preferably 2 Above 11mm, preferably 11mm 2 It is sufficient if the above is ensured.

[0057] Of the nozzles in which the inner surface of the gas-dissolving expansion section 13 is an expansion tapered surface, test nozzles Nos. 2 to 6 and Nos. 12, 13, and 20 have M1.4 cavitation screw members 10 arranged relative to the throttling section 9 in the layout shown in Figure 2. The test results in Table 1 for these test nozzles reveal the following.

[0058] The test nozzles Nos. 2 to 6 had a tan θ value of the expanding tapered surface forming the gas-dissolving expanding portion 13 set within a range of 0.04 to 0.14, whereas the test nozzles Nos. 10 to 17 had a tan θ value of the expanding tapered surface that exceeded this range. The negative suction pressure values ​​of the test nozzles Nos. 2 to 6 were higher than those of the test nozzles Nos. 10 to 17. Furthermore, the test nozzle No. 2 and the test nozzle No. 20 had the same cross-sectional flow area in the throttling portion 9, but the tan θ value of the expanding tapered surface was 0.160 for the test nozzle No. 20, while the tan θ value of the test nozzle No. 2 was set to a smaller value of 0.125. The negative suction pressure value of the test nozzle No. 2 was higher than that of the test nozzle No. 20. It is clear that setting the angle θ of the expanding tapered surface to a small value, particularly setting the tan θ value to a range of 0.04 to 0.14, is advantageous for improving the negative suction pressure value.

[0059] Test nozzles No. 2 to No. 6 have the same thread layout as in Figure 2, but the inner diameter d of the constricted portion is changed, and the 70% valley point area density value gradually decreases from No. 2 to No. 6. Of these, the value of the 70% valley point area density is 1.00 count / mm 2 For test nozzles No. 2 to No. 5, the 70% valley area density was 1.00 pieces / mm 2 The negative suction pressure is greater than that of test nozzle No. 6, which is less than 1.20 / mm. In particular, the 70% valley point area density is 1.20 / mm. 2 More than 2.25 / mm 2 Test nozzles Nos. 2 to 4 below achieved very good results, with negative suction pressure values ​​of -0.09 MPa or less under water flow conditions of a dynamic water pressure of 0.1 MPa.

[0060] Test nozzles Nos. 7 and 8 have roughly the same cross-sectional flow area S of the throttling portion 9, but the nominal diameter of the cavitation screw element 10 used is changed to M1.2 or M1.6, which is different from that of test nozzle No. 3. The measured suction negative pressure values ​​for these test nozzles are also relatively good, but slightly inferior to test nozzle No. 3, which uses M1.4. These differences are thought to be caused by differences in the depth of the thread roots of the screw elements used.

[0061] Test nozzles Nos. 2, 18, and 19 all use the same M1.4 threaded member as the cavitation screw member 10, and the cross-sectional flow area S of the throttle section 9 is set to a similar value. However, the number and layout of the threaded members differ. Specifically, test nozzle No. 2 has one threaded member 10 arranged across a predetermined diameter of the axial cross section of the throttle section 9 (i.e., the leg length of the threaded member 10 located within the throttle section 9 is greater than the radius of the throttle section 9). Test nozzle No. 18 has four threaded members arranged along two diameters, forming a gap 215 in the center of the cross section (see Figure 7). Test nozzle No. 19 has two M1.4 threaded members arranged along one diameter (Figure 5). Comparing the results of these test nozzles, test nozzle No. 2 generates a higher negative suction pressure than test nozzles Nos. 18 and 19.

[0062] Test nozzle No. 1 and test nozzle No. 2 have the same screw arrangement and inner diameter of the constricted section, but the inner surface of the gas-dissolving expansion section 13 of test nozzle No. 1 is cylindrical as shown in Figure 8, whereas the inner surface of the gas-dissolving expansion section 13 of test nozzle No. 2 is a tapered surface that is more gradually tapered than the inlet tapered section 5 as shown in Figure 1. Test nozzle No. 2 has a higher suction negative pressure.

[0063] Figure 11 shows the measurement results of the negative pressure dynamic water pressure characteristic curve, which shows the relationship between the dynamic water pressure value and the suction negative pressure generated in the gas introduction hole 6 when water is passed through the nozzle main body 2 with the nozzle outlet side open, for the test nozzle No. 2 (Example) and the test nozzle No. 101 (Comparative Example). The flow cross-sectional area at the constriction part of the test nozzle No. 2 is 8.2 mm 2 , No. 101 test nozzle is 7.1 mm 2 There is not much difference in the average flow velocity values ​​at a dynamic water pressure of 0.10 MPa shown in Table 1, but the shapes of the negative pressure dynamic water pressure characteristic curves are clearly different.

[0064] Specifically, for test nozzle 101 (a typical orifice-type nozzle with a cylindrical gas-dissolving expansion section 13), the change in negative suction pressure with increasing water dynamic pressure was gradual, and the negative suction pressure value at a water dynamic pressure of 0.10 MPa was read as approximately -0.055 MPa. Furthermore, the critical water dynamic pressure value for the negative suction pressure to be -0.07 MPa or less was 0.16 MPa, and the critical water dynamic pressure value for the negative suction pressure to be -0.09 MPa or less was 0.27 MPa.

[0065] On the other hand, the test nozzle No. 2, which is an embodiment of the present invention, clearly exhibits a much steeper change in negative suction pressure with increasing water dynamic pressure due to the gradually expanding inner surface of the gas-dissolving expansion section 13 and the provision of a cavitation screw member upstream of the gas inlet hole 6. At a water dynamic pressure of 0.10 MPa, the negative suction pressure was −0.093 MPa, the critical water dynamic pressure for the negative suction pressure to be −0.07 MPa or less was 0.06 MPa (i.e., 0.07 MPa or less), and the critical water dynamic pressure for the negative suction pressure to be −0.09 MPa or less was 0.082 MPa (i.e., 0.09 MPa or less). This indicates that sufficient negative suction pressure is obtained even at low flow rates (i.e., low water dynamic pressures).

[0066] Figure 12 shows a comparison of the negative pressure flow velocity characteristic curves obtained by converting the horizontal axis of Figure 11 into the average flow velocity value at the choke section for test nozzle No. 2 and test nozzle No. 101. The critical flow velocity value for test nozzle No. 101, where the suction negative pressure value is -0.07 MPa or less, is 17.1 m / s, and the critical flow velocity value for test nozzle No. 101 is -0.09 MPa or less is 21.0 m / s, which is large. On the other hand, the critical flow velocity value for test nozzle No. 2, where the suction negative pressure value is -0.07 MPa or less, is 12.3 m / s (i.e., 13 m / s or less), and the critical flow velocity value for test nozzle No. 2 is -0.09 MPa or less is 13.8 m / s (i.e., 14 m / s or less), which are significantly lower than those of test nozzle No. 101.

[0067] Figure 13 shows the measurement results of the negative pressure dynamic water pressure characteristic curves for the test nozzle No. 3 (Example) and the test nozzle No. 102 (Comparative Example) in comparison. The cross-sectional flow area at the throttle section of the test nozzle No. 3 was 14.1 mm2 , No. 102 test nozzle is 12.6 mm 2 According to Table 1, the difference in the average flow velocity at a hydrodynamic pressure of 0.10 MPa is within a few percent. However, in the above-mentioned region of the cross-sectional flow area where the pressure loss in the throttle section 9 is reduced, the difference in the shape of the negative pressure hydrodynamic characteristic curve between the example test nozzle and the comparative example test nozzle becomes even more pronounced.

[0068] Specifically, for test nozzle No. 102, the negative suction pressure was approximately -0.057 MPa at a hydrodynamic pressure of 0.10 MPa. The critical hydrodynamic pressure for a negative suction pressure of -0.07 MPa or less was 0.14 MPa, and the critical hydrodynamic pressure for a negative suction pressure of -0.09 MPa or less was 0.27 MPa. Compared to test nozzle No. 101, the performance in the low hydrodynamic pressure range was slightly improved, but a large hydrodynamic pressure was still required to achieve a negative suction pressure of -0.09 MPa or less.

[0069] On the other hand, as is clear from a comparison with Figure 11, the test nozzle No. 3 according to an embodiment of the present invention exhibits a more abrupt change in negative suction pressure with increasing water dynamic pressure than the test nozzle No. 2. The critical water dynamic pressure for negative suction pressure to be -0.07 MPa or less is 0.040 MPa, and the critical water dynamic pressure for negative suction pressure to be -0.09 MPa or less is 0.051 MPa. It can be seen that in the range of water dynamic pressures above 0.10 MPa, a nearly flat negative suction pressure close to the physical maximum value is obtained.

[0070] Figure 14 shows a comparison of the negative pressure flow velocity characteristic curves obtained by converting the horizontal axis of Figure 13 into the average flow velocity value at the choke section for test nozzle No. 3 and test nozzle No. 102. For test nozzle No. 102, the critical flow velocity value for the suction negative pressure to be -0.07 MPa or less is 17.1 m / s, and the critical flow velocity value for the suction negative pressure to be -0.09 MPa or less is 21.3 m / s. On the other hand, for test nozzle No. 3, the critical flow velocity value for the suction negative pressure to be -0.07 MPa or less is 11.3 m / s, and the critical flow velocity value for the suction negative pressure to be -0.09 MPa or less is 12.4 m / s.

[0071] Example 2 Test nozzles numbered 1 to 8, 11, 13 to 19 (all examples) and 101 (comparative example) in Table 1 were installed in the gas dissolution device 100 shown in Figure 3 in the same manner as in Example 1, and the storage tank 50 (volume: 20 L) was filled with tap water at 20°C, and a carbon dioxide gas cylinder was connected as the gas supply source 123. In this state, first, the switching valve 117 was switched to the circulation pipe 105 side to operate the pump 55, and the opening of the flow rate adjustment valve 116 was appropriately changed while checking the reading displayed on the pressure gauge 110, so that the dynamic water pressure applied to the test nozzle was set to 0.1 MPa or 0.2 MPa.

[0072] Next, the gas supply switching valve 122 was switched to the main gas supply pipe 121, and while monitoring the flow rate of tap water flowing through the test nozzle with the flow meter 111, the opening of the flow control valve 124 was appropriately changed to adjust the flow rate of carbon dioxide gas so that the gas-liquid mixture ratio (gas flow rate / water flow rate under standard conditions) was 0.7. Since all test nozzles generated negative suction pressure, the carbon dioxide gas supply pressure was set to 0.1 MPa. The carbon dioxide gas flow rate under standard conditions was calculated from the pressure and flow rate readings of the flow / pressure measuring device 125. After adjustment, the switching valve 117 was quickly switched to the liquid extraction pipe 103 side, and the resulting water was collected. The carbon concentration was measured using a commercially available carbon dioxide gas concentration meter (DKK-TOA Corporation: CGP-31 (diaphragm electrode type)).

[0073] For comparison, test nozzles (numbers 113 to 117) were created as comparative examples corresponding to test nozzles numbered 13 to 17, with the gas inlet hole positioned 2 mm upstream of the cavitation screw member. When these comparative test nozzles were installed in the gas dissolution apparatus 100 shown in FIG. 3 after removing the main gas supply pipe 121 from the gas inlet joint 15 and operating the pump 55, water backflowed and sprayed out of the gas inlet hole. Furthermore, an attempt was made to connect the main gas supply pipe 121 to the gas inlet joint 15 to supply carbon dioxide gas, but this was not possible at 0.1 MPa. Therefore, carbon dioxide gas was supplied at 0.2 MPa, as in Patent Document 3, and the carbon concentration of the recovered water was measured in the same manner.

[0074] For each condition, the theoretical carbon dioxide concentration Ct was calculated assuming that all the supplied carbon dioxide dissolved, and the carbon dioxide dissolution efficiency was calculated by dividing the measured carbon dioxide concentration C by Ct. The results are summarized in Table 2.

[0075] [Table 2]

[0076] In the comparative test nozzles (numbers 113 to 117), the carbon dioxide gas supply pressure and gas-liquid ratio were set to twice those of the corresponding example test nozzles (numbers 13 to 17) because no negative suction pressure was generated. Nevertheless, it can be seen that the carbon dioxide gas concentrations achieved by the example test nozzles (numbers 13 to 17) are all roughly equivalent to or higher than those of the corresponding comparative test nozzles. Furthermore, when comparing the carbon dioxide gas dissolution efficiency, the example test nozzles are approximately twice or more than those of the corresponding comparative test nozzles.

[0077] In particular, when test nozzles No. 1 to No. 5, which have high self-priming ability and 70% valley point area density adjusted to the desired range mentioned above, were used, a high carbonate concentration of 750 to 1375 ppm was achieved despite the single-pass dissolution, and the dissolution efficiency was also high at 55% or more. [Explanation of symbols]

[0078] 1 Gas ejection nozzle 2 Nozzle body 3 liquid inlet 5. Inlet tapered section 6 Gas inlet 9. Constriction section 10 Cavitation screw element 11 Liquid flow path 13 Gas dissolving expansion section 31 threads 32 Neji Valley

Claims

1. a nozzle body having a single liquid flow path formed therein, the single liquid flow path having a liquid inlet at one end and a liquid outlet at the other end, and a throttle portion formed midway through the liquid flow path so that the diameter of the liquid flow path is smaller than that of the liquid inlet; a cavitation screw member disposed within the throttle portion, the cavitation screw member having a thread portion formed on its outer surface, the thread portion having a thread pitch of 0.20 mm or more and 0.40 mm or less, a thread root depth of 0.20 mm or more and 0.40 mm or less, and a nominal diameter of 1.0 mm or more and 2.0 mm or less; a gas dissolving expansion section that is connected to the downstream side of the throttle section in a manner that forms a part of the liquid flow path and that expands in axial cross section area continuously or stepwise toward the liquid outlet, a nozzle body including a gas inlet hole, the gas inlet hole communicating with the throttle portion or the gas-dissolving expanded diameter portion downstream of all of the cavitation screw members located within the throttle portion, and formed to connect the outside of the nozzle body with the liquid flow path.

2. 2. The gas ejection nozzle according to claim 1, wherein the cavitation screw member is arranged along a predetermined diameter of an axial cross section of the throttle portion so that a leg length of the screw member located within the throttle portion is greater than a radius of the throttle portion.

3. 3. The gas ejection nozzle according to claim 2, wherein the cavitation screw member is arranged so that the leg portion located within the throttle portion spans the entire diameter of the axial cross section of the throttle portion.

4. 2. The gas ejection nozzle according to claim 1, wherein the inner diameter of the axial cross section of the throttle portion is set within a range of 2.0 mm to 8.0 mm so that, when the liquid outlet is open and water is supplied to the liquid inlet at a dynamic water pressure of 0.1 MPa, the flow rate is 1 L / min to 35 L / min and the average flow velocity at the position where the cavitation screw member is disposed is 9 m / sec or more.

5. 2. The gas ejection nozzle according to claim 1, wherein the gas-dissolving expansion section is formed as a tapered surface whose axial cross-sectional area continuously increases with increasing distance downstream from the throttle section, and the gas inlet hole communicates with the liquid flow path within a section from the downstream edge of the outer peripheral surface of the cavitation screw member located within the throttle section to a position on the inner peripheral surface of the gas-dissolving expansion section where the cross-sectional diameter is 1.5 times the inner diameter of the throttle section.

6. 6. The gas ejection nozzle according to claim 5, wherein the gas-dissolving expansion portion forming the tapered surface is formed such that, when a gradient angle of the inner circumferential surface with respect to the center line of the throttle portion is θ, a gradient section in which tan θ is 0.04 or more and 0.14 or less accounts for 90% or more of a section length of the gas-dissolving expansion portion.

7. 7. The gas ejection nozzle according to claim 6, wherein a negative pressure hydrodynamic pressure characteristic curve showing the relationship between hydrodynamic pressure and negative suction pressure generated in the gas introduction hole when water is passed through the nozzle body with the nozzle outlet side open, has a critical hydrodynamic pressure value of 0.07 MPa or less for the negative suction pressure to be −0.07 MPa or less.

8. 7. The gas ejection nozzle according to claim 6, wherein a negative pressure flow velocity characteristic curve showing the relationship between an average flow velocity value at the throttle portion and the negative suction pressure generated in the gas introduction hole when water is passed through the nozzle body with the nozzle outlet side open has a critical flow velocity value of 13 m / s or less for the negative suction pressure value to be −0.07 MPa or less.

9. 7. The gas ejection nozzle according to claim 6, wherein a negative pressure hydrodynamic pressure characteristic curve showing the relationship between the hydrodynamic pressure value when water is passed through the nozzle body and the negative suction pressure generated in the gas introduction hole has a critical hydrodynamic pressure value of 0.09 MPa or less for the negative suction pressure value to be −0.09 MPa or less.

10. 7. The gas ejection nozzle according to claim 6, wherein a negative pressure flow velocity characteristic curve showing the relationship between an average flow velocity value of the throttle portion and the negative suction pressure generated in the gas introduction hole when water is passed through the nozzle body has a critical flow velocity value of 14 m / s or less for the negative suction pressure value to be −0.09 MPa or less.

11. 2. The gas ejection nozzle according to claim 1, wherein the gas-dissolving expansion portion is formed as an expansion-diameter cylindrical surface that discontinuously expands in diameter from the throttle portion, and the gas inlet hole communicates with a liquid flow path within the throttle portion or at a boundary between the throttle portion and the gas-dissolving expansion portion.

12. The number of thread valley points of the cavitation screw member that are present within a 70% radius from the center in the axial cross section of the throttled portion is defined as the 70% valley number, and the value of the 70% valley number divided by the flow cross-sectional area obtained by subtracting the area of ​​the projected region of the cavitation screw member from the total cross-sectional area of ​​the throttled portion is the 70% valley number area density, which is 1.00 points / mm ２ 5.60 / mm or more ２ 12. A gas ejection nozzle according to any one of claims 1 to 11, wherein:

13. 2. The gas ejection nozzle according to claim 1, wherein the threaded portion of the cavitation screw member has a thread pitch of 0.28 mm or more and 0.32 mm or less and a thread root depth of 0.28 mm or more and 0.32 mm or less.

14. a gas ejection nozzle comprising: a nozzle body having a single liquid flow path formed therein, the single liquid flow path having a liquid inlet at one end and a liquid outlet at the other end, and a throttle section formed midway along the liquid flow path so that the diameter of the liquid flow path is smaller than that of the liquid inlet; a cavitation screw member disposed within the throttle section, the cavitation screw member having a thread section formed on its outer peripheral surface, the thread section having a thread pitch of 0.20 mm or more and 0.40 mm or less, a thread root depth of 0.20 mm or more and 0.40 mm or less, and a nominal diameter of 1.0 mm or more and 2.0 mm or less; and a gas dissolution expansion section connected to the downstream side of the throttle section in a manner forming a part of the liquid flow path, the gas dissolution expansion section having an axial cross-sectional area that expands continuously or stepwise toward the liquid outlet, the nozzle body having a gas introduction hole that communicates with the throttle section or the gas dissolution expansion section downstream of all of the cavitation screw members located within the throttle section, and that is formed to connect the outside of the nozzle body to the liquid flow path; a liquid delivery unit that delivers liquid to the liquid inlet of the nozzle body; a gas supply unit that supplies gas to the gas introduction hole of the nozzle body, A gas dissolution device characterized in that the gas is sucked into the liquid through the gas introduction hole based on negative pressure generated downstream of the cavitation screw member in the liquid flow path, and the gas is dissolved by being entrained in turbulence generated in the gas dissolution expansion section.

15. a nozzle body having a single liquid flow path formed therein with a liquid inlet at one end and a liquid outlet at the other end, and a throttled section formed midway through the liquid flow path so that the diameter of the liquid flow path is smaller than that of the liquid inlet; a cavitation screw member disposed within the throttled section, and having a threaded section formed on its outer surface with a thread pitch of 0.20 mm or more and 0.40 mm or less, a thread root depth of 0.20 mm or more and 0.40 mm or less, and a nominal diameter of 1.0 mm or more and 2.0 mm or less; and a gas dissolving expansion section that forms part of the liquid flow path and is connected to the downstream side of the throttled section, and whose axial cross-sectional area expands continuously or stepwise toward the liquid outlet, and the nozzle body has a gas introduction hole. a gas inlet of a nozzle body of a gas ejection nozzle formed so as to connect the outside of the nozzle body with the liquid flow path, the gas inlet of the nozzle body being in communication with the throttle section or the gas dissolution expansion section downstream of all of the cavitation screw members located within the throttle section; a gas being supplied to the gas inlet of the nozzle body; and a negative pressure being generated in the liquid flow path downstream of the cavitation screw members, whereby the gas from the gas inlet is sucked into the liquid, and the gas is entrained in the turbulence generated in the gas dissolution expansion section, thereby dissolving the gas.

16. the liquid is water, 16. The method for dissolving a gas according to claim 15, wherein the gas comprises one or more gases selected from the group consisting of carbon dioxide gas, ozone-containing gas, oxygen, nitrogen, air, ammonia, and hydrogen.

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