A self-compensating cylindrical head flow guiding injection needle structure

Abstract

The present invention discloses a self-compensating cylindrical head flow guiding injection needle structure, which is composed of a nozzle cover, a throat pipe, an injection needle and a bolt; four airfoil plates are evenly distributed on the head of the injection needle, and a gas guiding hole is opened on each airfoil plate, and each gas guiding hole communicates with the air inlet hole on the outer end face of the injection needle. The structure of the present invention can ensure that the high-speed jet flow is in an annular state, avoid cavitation at the tip of the injection needle, reduce the radial velocity of the jet flow, increase the kinetic energy of the water flow doing work, reduce the frictional loss of the jet flow in the runner, and improve the efficiency of the runner.

Description

Technical Field

[0001] The present invention relates to a self - air - supplementing cylindrical - head flow - guiding injection needle structure. Background Art

[0002] The DC nozzle is an important flow - guiding component of an impulse turbine. The gravitational potential energy of water is converted into the kinetic energy of a jet after passing through the DC nozzle. The runner rotates and does work to generate electricity under the impact of the high - speed jet. The performance of the DC nozzle directly affects the energy conversion efficiency of the impulse turbine.

[0003] The conventional built - in conical injection needle structure is as Figure 1 shown. High - pressure water flows into the DC nozzle from the inlet. Since the annular cross - sectional area between the injection needle and the DC nozzle at the nozzle outlet decreases, the water flow velocity gradually increases. The pressure at the DC nozzle outlet is the atmospheric pressure, and the water flow will shoot into the atmosphere along the injection needle at a very high speed here. When the water flow passes through the tip of the injection needle, the potential energy of the water flow is rapidly converted into jet kinetic energy, and the rapid increase in the water flow velocity causes the pressure at the tip of the injection needle to decrease. The low pressure will cause cavitation at the tip of the injection needle, resulting in cavitation erosion, shortening the service life of the injection needle, and even causing vibrations of the unit and the power house. At the same time, under the combined influence of the external pressure and the taper of the injection needle, the jet will generate a radial velocity, which will cause the effective kinetic energy of the water flow when it shoots into the bucket to decrease, and the efficiency of the unit will decline. In summary, there is an urgent need for a flow - guiding injection needle structure with high energy conversion efficiency and good cavitation performance. Summary of the Invention

[0004] The object of the present invention is to improve the power generation efficiency of an impulse turbine and suppress the generation of cavitation through a self - air - supplementing cylindrical - head flow - guiding injection needle structure. The technical solution of the present invention is specifically described as follows: It is composed of a nozzle cover, a throat tube, an injection needle, and bolts. The inside of the nozzle cover is a hollow conical structure, the inside of the throat tube is a hollow cylindrical structure, the injection needle is composed of a first cylindrical surface, a second cylindrical surface, and an outer conical surface, and four airfoil plates are evenly distributed on the second cylindrical surface and the outer conical surface of the injection needle. The injection needle is placed inside the throat tube, and the nozzle cover is fixedly connected to the throat tube through bolts.

[0005] In the above - mentioned self - air - supplementing cylindrical - head flow - guiding injection needle structure, the first cylindrical surface of the injection needle, the second cylindrical surface of the injection needle, and the outer conical surface of the injection needle are coaxial, and the outer conical surface of the injection needle has the same taper and is coaxial with the inner conical surface of the nozzle cover.

[0006] In the above - mentioned self - air - supplementing cylindrical - head flow - guiding injection needle structure, the sum of twice the height of the airfoil plate and the diameter of the second cylindrical surface of the injection needle is equal to 9 / 10 of the nozzle orifice diameter, and the width of the airfoil plate is equal to 1 / 8 of the nozzle orifice diameter.

[0007] In the above self-compensating cylindrical head diversion injection needle structure, the air guide hole penetrates through the airfoil plate, and the distance from the center line of the air guide hole to the outer end face of the injection needle is the same as the diameter of the second cylindrical surface of the injection needle, and the diameter of the air guide hole is equal to 1 / 2 of the width of the airfoil plate.

[0008] In the above self-compensating cylindrical head diversion injection needle structure, the air inlet hole is located at the center of the outer end face of the injection needle and communicates with the four air guide holes, and the diameter of the air inlet hole is 2.1 times the diameter of the air guide hole.

[0009] The beneficial effects of the present invention are as follows:

[0010] 1. The cavitation performance of the injection needle is good: the jet flow velocity at the outlet of the nozzle is high and the pressure is low. Under the action of the pressure difference, air is inhaled through the air guide hole of the airfoil plate and flows out along the air inlet hole on the outer end face of the injection needle, which can effectively avoid cavitation erosion caused by low pressure at the head of the injection needle and improve the service life of the injection needle and the stability of the unit operation.

[0011] 2. The jet energy of the injection needle is high: under the same injection needle stroke, the jet flow rate remains unchanged. Due to the cylindrical head injection needle structure and the air compensation effect, the internal and external pressures of the jet are equal. The high-speed water flow will eject in a circular state along the head of the injection needle, the radial velocity of the jet cross-section decreases, and the kinetic energy of the water flow doing work increases, and the kinetic energy available for the runner increases.

[0012] 3. The energy conversion efficiency of the runner is high: most of the water flow of the annular cylindrical jet directly enters the arc surface of the bucket without passing through the water dividing edge, the flow loss along the way decreases, the energy conversion efficiency increases, and the runner efficiency increases. Description of the Drawings

[0013] Figure 1 is the structural diagram of the injection needle of a conventional impulse water turbine;

[0014] Figure 2 is the assembly diagram of the self-compensating cylindrical head diversion injection needle structure;

[0015] Figure 3 is the structural diagram of the self-compensating cylindrical head diversion injection needle;

[0016] Figure 4 is the structural diagram of the nozzle shroud.

[0017] Explanation of the marks in the figure: 1 - nozzle shroud; 2 - injection needle; 3 - throat; 4 - bolt; 5 - first cylindrical surface of the injection needle; 6 - outer conical surface of the injection needle; 7 - inner conical surface of the nozzle shroud; 8 - second cylindrical surface of the injection needle; 9 - airfoil plate; 10 - air guide hole; 11 - air inlet hole. Detailed Embodiments

[0018] The present invention will be further described below in conjunction with the drawings and specific embodiments.

[0019] As Figure 2As shown in the figure, a self-compensating cylindrical head diversion injection needle structure is composed of a nozzle cover 1, an injection needle 2, a throat pipe 3, and a bolt 4. The inside of the nozzle cover 1 is a hollow conical structure, and the inside of the throat pipe 3 is a hollow cylindrical structure. The injection needle 2 is composed of a first cylindrical surface 5, a second cylindrical surface 8, and an outer conical surface 6. Four airfoil plates 9 are evenly distributed on the second cylindrical surface 8 and the outer conical surface 6 of the injection needle 2. The injection needle 2 is placed inside the throat pipe 3, and the nozzle cover 1 is fixedly connected to the throat pipe 3 through the bolt 4.

[0020] In this embodiment, the head of the injection needle is cylindrical and four airfoil plates are added, which can ensure the annular cross-section of the jet, reduce the radial velocity, and improve the effective kinetic energy of the jet.

[0021] As Figure 3 , 4 shown, the first cylindrical surface 5, the second cylindrical surface 8, and the outer conical surface 6 of the injection needle 2 are coaxial. The taper of the outer conical surface 6 of the injection needle 2 is the same as that of the inner conical surface 7 of the nozzle cover 1 and they are coaxial. The four airfoil plates 9 are evenly distributed at four equal parts on the outer conical surface 6 and the second cylindrical surface 8 of the injection needle 2. The front end of the airfoil plate 9 is oval, and the end is a conical structure. The sum of twice the height of the airfoil plate 9 and the diameter of the second cylindrical surface 8 of the injection needle 2 is equal to 9 / 10 of the nozzle diameter, and the width of the airfoil plate 9 is equal to 1 / 8 of the nozzle diameter. Each airfoil plate 9 has a vent hole 10 with a diameter of 1 / 2 of the width of the airfoil plate 9. The distance from the center line of the vent hole 10 to the outer end face of the injection needle 2 is the same as the diameter of the second cylindrical surface 8 of the injection needle 2. The air inlet hole 11 is located at the center of the outer end face of the injection needle 2 and communicates with the four vent holes 10. The diameter of the air inlet hole 11 is equal to 2.1 times the diameter of the vent hole 10.

[0022] In this embodiment, the vent hole and the air inlet hole are communicated with each other to ensure smooth air flow. At the same time, the area of the air inlet hole is equal to 1.1 times the sum of the areas of the four vent holes, which ensures that the air flow velocity remains unchanged during the natural air intake process and reduces the air supplement loss.

[0023] In the present invention, the front end of the injection needle is a cylindrical structure. After the jet flows out from the outlet of the DC nozzle, it will flow along the second cylindrical surface of the injection needle. After leaving the head of the injection needle, due to the high jet velocity, a low pressure will be generated in the central area of the jet. Under the action of the pressure difference, air enters through the four vent holes, is inhaled from the air inlet hole into the central area of the jet, and the cavitation phenomenon caused by the low pressure is suppressed through automatic air supplement, improving the service life of the injection needle and increasing the operation stability of the equipment. At the same time, the supplement of air enables the jet to be ejected in an annular state, reducing the radial velocity of the jet cross-section and increasing the effective kinetic energy of the jet. Most of the water flow of the annular jet will directly enter the arc surface of the water bucket without passing through the dividing blade, reducing the along-flow loss of the jet and improving the energy conversion efficiency.

[0024] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A self-compensating cylindrical head diversion injection needle structure, characterized in that: It is composed of a nozzle cover (1), an injection needle (2), a throat tube (3), and a bolt (4); the inside of the nozzle cover (1) is a hollow conical structure, the inside of the throat tube (3) is a hollow cylindrical structure, and the injection needle (2) is composed of a first cylindrical surface (5), a second cylindrical surface (8), and an outer conical surface (6). Four airfoil plates (9) are evenly distributed on the second cylindrical surface (8) and the outer conical surface (6) of the injection needle (2); the injection needle (2) is placed inside the throat tube (3), and the nozzle cover (1) is fixedly connected to the throat tube (3) through a bolt (4); the air guide hole (10) penetrates through the airfoil plate (9), and the distance from the center line of the air guide hole (10) to the outer end face of the injection needle (2) is equal to the diameter of the second cylindrical surface (8) of the injection needle (2), and the diameter of the air guide hole (10) is equal to 1 / 2 of the width of the airfoil plate (9); the air inlet hole (11) is located at the center of the outer end face of the injection needle (2) and communicates with the four air guide holes (10) mutually, and the diameter of the air inlet hole (11) is equal to 2.1 times the diameter of the air guide hole (10).

2. A self-compensating cylindrical head diversion injection needle structure according to claim 1, characterized in that: The sum of twice the height of the airfoil plate (9) and the diameter of the second cylindrical surface (8) of the injection needle (2) is equal to 9 / 10 of the nozzle orifice diameter, and the width of the airfoil plate (9) is equal to 1 / 8 of the nozzle orifice diameter.

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