A large flow centrifugal atomizing nozzle and its design method

Abstract

The application discloses a large-flow centrifugal atomizing nozzle and a design method thereof, and belongs to the field of agricultural plant protection machinery and liquid atomization technology. The nozzle comprises a direct current motor, a liquid inlet pipe, an annular cavity, a flow guide pipe and a triple atomizing disc. Liquid enters the annular cavity through the liquid inlet pipe, is stabilized and energy-dissipated by a baffle, and then falls into a liquid collecting area of the triple atomizing disc through the flow guide pipe. The outer edge of the triple atomizing disc is provided with an inner layer flow channel, a middle layer flow channel and an outer layer flow channel from inside to outside. The bottom end edge of each layer flow channel is provided with a triangular sawtooth. With the increase of flow, liquid is overflowed and branched to each layer flow channel to be accelerated, stretched and thinned, and finally is cut by the sawtooth to realize secondary breaking. The design method comprises designing the disc surface diameter of the center disc, the included angle between the wall surface of each layer flow channel and the horizontal direction, the sawtooth height of the bottom end edge of each layer flow channel and the width of each layer flow channel. The application can adapt to flow changes, and still maintains high atomization efficiency and uniform droplet distribution under large-flow operation.

Description

Technical Field

[0001] This invention belongs to the field of agricultural plant protection machinery and liquid atomization technology, specifically relating to a high-flow centrifugal atomizing nozzle and its design method, which is particularly suitable for high-flow spraying operations of agricultural drones that require precise control of droplet size distribution and anti-drift. Background Technology

[0002] Centrifugal atomizing nozzles are widely used in agricultural drone-based plant protection due to their relatively uniform droplet size distribution and resistance to clogging. However, existing conventional single-layer centrifugal atomizing nozzles often have significant limitations when facing high-flow-rate operations. As the input flow rate increases, the thickness of the liquid film on the single-layer atomizing disc increases significantly, making it impossible for centrifugal force to fully tear the liquid film. This results in incomplete atomization, larger droplet size, and extremely uneven distribution. This phenomenon not only reduces the deposition rate and coverage uniformity of the pesticide in the crop canopy but also increases the risk of pesticide runoff and environmental pollution.

[0003] To meet the application needs of different crops, spray nozzles typically need to maintain good atomization even when flow conditions change. Existing atomizing nozzles struggle to automatically adjust the atomization level under low, medium, and high flow conditions, lacking a structural design that can adapt to flow changes and achieve triple-efficiency atomization. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a high-flow-rate centrifugal atomizing nozzle and its design method. This nozzle, through an innovative triple atomizing disc design, maintains extremely high atomization efficiency and droplet fineness even at high flow rates.

[0005] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0006] A high-flow-rate centrifugal atomizing nozzle includes a DC motor, an inlet pipe, a guide pipe, an annular cavity, and a triple atomizing disc. The DC motor is mounted above the annular cavity, and the lower part of the annular cavity is connected to the triple atomizing disc through multiple evenly distributed guide pipes. The inlet pipe extends into the annular cavity from the outer edge of the DC motor in an inclined direction and is connected to it. The motor shaft of the DC motor passes through the annular cavity and its end is fixed to the triple atomizing disc.

[0007] The annular cavity has a central cavity for the motor shaft to pass through, and multiple evenly distributed baffles are fixed between the outer wall of the central cavity and the inner wall of the annular cavity.

[0008] The triple atomizing disk consists of a central disk, an inner ring, a middle ring, and an outer disk from the inside out. An inner flow channel is formed between the central disk and the inner ring, a middle flow channel is formed between the inner ring and the middle ring, and an outer flow channel is formed between the middle ring and the outer disk. The liquid collection area is located above the central disk. Triangular serrations are provided at the bottom edges of the annular portion of the central disk, the bottom edges of the inner ring, the bottom edges of the middle ring, and the bottom edges of the annular portion of the outer disk.

[0009] In the above technical solution, a bushing is fixed at the bottom end of the motor shaft, and the upper and lower ends of the bushing are fixed to the outer disk and the central disk, respectively.

[0010] In the above technical solution, the central disk, inner ring, middle ring and outer disk are connected by circumferentially evenly distributed ribs. One end of the rib is fixed to the bushing, and the other end passes through the flow channels of each layer in the radial direction and is connected to the outer disk.

[0011] In the above technical solution, the annular portion of the central disk, the inner ring, the middle ring, and the annular portion of the outer disk are all inclined inward.

[0012] In the above technical solution, the angle between the liquid inlet pipe and the horizontal direction is in the range of 30°-60°.

[0013] In the above technical solution, the thickness of the central disk, inner ring, middle ring and outer disk is 1-1.5mm; the materials of the annular cavity, guide tube, triple atomizing disk, bushing and rib are polytetrafluoroethylene or composite plastic; the materials of the housing and motor shaft of the DC motor are stainless steel or metal alloy.

[0014] A design method for a high-flow-rate centrifugal atomizing nozzle, in order to utilize the centrifugal acceleration of the triple atomizing disc (7) to sufficiently thin the liquid film to the preset maximum liquid film thickness h. max The diameter of the central disk Where μ is the dynamic viscosity of the liquid. The liquid flow rate allocated to the inner channel, ρ is the liquid density, and ω is the rotational angular velocity of the triple atomizing disk. C is the angle between the channel wall and the horizontal direction. h h is the film thickness correction factor. max This is the preset maximum liquid film thickness.

[0015] Furthermore, the angle between the wall surface of each flow channel and the horizontal direction... .

[0016] Furthermore, the height of the serrations With the target droplet size D p The terms are directly proportional to the square roots of the eccentric Weber numbers: , where Ck This is an empirical coefficient. The surface tension coefficient of the liquid. The radius of rotation is the position of the sawtooth.

[0017] Furthermore, the height difference between the upper surface of the central disk and the upper end face of the inner ring is... The width W1 of the inner flow channel satisfies: k1 is a correction factor, ranging from 0.5 to 0.7; the height difference between the upper surface of the central disk and the upper end face of the middle ring is... The width W2 of the middle layer flow channel satisfies: k2 is a correction factor, ranging from 0.6 to 0.8; the height difference between the upper surface of the central disk and the lower surface of the horizontal portion of the outer disk is... The width W3 of the outer flow channel satisfies: k3 is a correction factor, with a value ranging from 0.7 to 0.9.

[0018] The beneficial effects of this invention are:

[0019] 1. The high-flow-rate centrifugal atomizing nozzle provided by this invention features a large spray flow rate, uniform droplet distribution, excellent anti-clogging performance, and strong corrosion resistance, achieving the goal of maintaining extremely high atomization efficiency even under high-flow-rate liquid supply conditions. Under the same spraying conditions, the centrifugal atomizing nozzle provided by this invention has higher atomization fineness and operating efficiency, achieving the goals of precise pesticide application and reduced pesticide loss. Furthermore, the centrifugal atomizing nozzle provided by this invention also features a compact structure, stable operation, and strong adaptability, enabling its widespread application in various fields such as agricultural plant protection drone spraying, industrial humidification, and environmental disinfection.

[0020] 2. In this invention, the liquid enters the inner, middle, and outer flow channels through a triple atomizing disc, forming multi-layered liquid films. This multi-layered flow channel design solves the problem of excessively thick liquid films leading to coarse droplets and a sharp decline in atomization performance in traditional single-layer centrifugal atomizing discs at high flow rates. Under centrifugal force, the liquid automatically achieves split atomization according to the supply volume, and the liquid film is accelerated and thinned on the inclined flow channel walls. The multi-layered atomizing disc structure of this invention increases the surface area for liquid spread, breaking the bottleneck of the traditional nozzle's inability to simultaneously achieve high flow rate and fine atomization. This allows the nozzle to simultaneously possess characteristics such as high spray flow rate, small droplet size, wide flow range adaptability, and high atomization uniformity.

[0021] 3. The nozzle designed in this invention features a central cavity and baffle inside the annular chamber, with several guide tubes evenly distributed at the bottom. The liquid undergoes sufficient energy dissipation and rectification before entering the atomizing disc, effectively eliminating the high-speed eccentric force caused by uneven liquid distribution. Simultaneously, the large-diameter guide tubes effectively prevent clogging of the pesticide powder suspension. Furthermore, the bottom edge of the triple atomizing disc has triangular serrations. The liquid film is broken by the serrations upon detachment from the disc surface, fully utilizing the mechanical energy from the high rotation speed to achieve secondary centrifugal fragmentation. In addition, the annular cavity design with a set thickness forms an effective thermal insulation layer, preventing pesticide agglomeration caused by high motor temperature, reducing nozzle maintenance costs, and improving overall service life. Attached Figure Description

[0022] Figure 1 This is a schematic cross-sectional view of a high-flow-rate centrifugal atomizing nozzle according to the present invention.

[0023] Figure 2 This is a cross-sectional structural schematic diagram and a magnified view of the serrations of the triple atomizing disc of the present invention;

[0024] Figure 3 This is a schematic diagram of the structure of the motor shaft and bushing of the present invention;

[0025] Figure 4 This is a partial structural diagram of the triple atomizing disc of the present invention.

[0026] Reference numerals in the attached diagram: 1. DC motor; 2. Inlet pipe; 3. Motor shaft; 4. Annular cavity; 5. Guide pipe; 6. Bushing; 7. Triple atomizing disc; 8. Rib; 9. Baffle; 10. Central cavity; 701. Outer disc; 702. Middle ring; 703. Inner ring; 704. Liquid collection area; 705. Central disc; 706. Serrated edge. Detailed Implementation

[0027] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0028] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "axial," "radial," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In this invention, unless otherwise expressly specified and limited, the terms "installation," "connection," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an indirect connection through an intermediate medium.

[0029] Combined with appendix Figure 1 To be continued Figure 2 As shown, one embodiment of the high-flow centrifugal atomizing nozzle of the present invention includes a DC motor 1, an inlet pipe 2, a motor shaft 3, an annular cavity 4, a guide pipe 5, a bushing 6, a triple atomizing disc 7, and ribs 8.

[0030] The DC motor 1 is mounted directly above the annular cavity 4, and its output end is connected to a motor shaft 3. The motor shaft 3 extends vertically downwards and passes through the central cavity 10 inside the annular cavity 4, maintaining a physical gap between the motor shaft 3 and the inner wall of the central cavity 10. The bushing 6 is fitted and fixed to the bottom end of the motor shaft 3, and the triple atomizing disc 7 is fixedly connected to the motor shaft 3 through the bushing 6.

[0031] The annular cavity 4 is located at the lower end of the DC motor 1. Multiple baffles 9 are evenly distributed radially inside the annular cavity 4, forming a fan-shaped area between adjacent baffles 9 for liquid flow. The height of each baffle 9 is less than the height of the annular cavity 4. The two sides of each baffle 9 are fixed to the outer wall of the central cavity 10 and the inner wall of the annular cavity 4, respectively, to buffer and dissipate the incoming liquid. The inlet pipe 2 extends into the annular cavity 4 from the outer edge of the DC motor 1 at an inclined direction and communicates with the annular cavity 4. The angle α between the inlet pipe 2 and the horizontal direction ranges from 30° to 60°. Several guide pipes 5 are evenly distributed circumferentially at the bottom of the annular cavity 4, extending downwards and connecting to the liquid collection area 704 of the triple atomizing disk 7.

[0032] like Figure 4As shown, the triple atomizing disk 7 consists of a central disk 705, an inner ring 703, a middle ring 702, and an outer disk 701, arranged from the inside out. An inner flow channel is formed between the central disk 705 and the inner ring 703; a middle flow channel is formed between the inner ring 703 and the middle ring 702; and an outer flow channel is formed between the middle ring 702 and the outer disk 701. A liquid collection area 704 is located above the central disk 705. The annular portions of the central disk 705, the inner ring 703, the middle ring 702, and the outer disk 701 are all inclined inwards at the same angle to the horizontal direction, denoted as θ1. The central disk 705, inner ring 703, middle ring 702, and outer disk 701 are connected by circumferentially evenly distributed ribs 8. Adjacent ribs 8 form a fan-shaped area for liquid flow. One end of each rib 8 is fixed to the bushing 6, and the other end passes radially through each flow channel and connects to the outer disk 701. The bottom edges of the annular portion of the central disk 705, the inner ring 703, the middle ring 702, and the outer disk 701 are each provided with triangular serrations 706. In this embodiment, the upper and lower ends of the bushing 6 are fixed to the outer disk 701 and the central disk 705, respectively.

[0033] In this embodiment, there are 6-8 flow guide tubes 5, 4-6 baffles 9, and 4-6 ribs 8.

[0034] The thickness d1 of the central disc 705, inner ring 703, middle ring 702, and outer disc 701 is 1-1.5mm to ensure sharp edges at their bottom ends. Figure 3 As shown, the length H of the motor shaft 3 is 50-60mm, and the diameter D2 of the motor shaft 3 is 4-6mm; the sidewall thickness d2 of the annular cavity 4 is 1-2mm; the outer diameter of the guide tube 5 is 6-8mm, and the sidewall thickness of the guide tube 5 is 0.5mm.

[0035] The annular cavity 4, the guide tube 5, the triple atomizing disc 7, the bushing 6, and the rib 8 are all made of materials with high mechanical strength and good waterproof and corrosion resistance, such as polytetrafluoroethylene or composite plastics; the housing of the DC motor 1 and the motor shaft 3 are made of materials with good torsional and fatigue resistance, such as stainless steel or metal alloys.

[0036] The working principle of the high-flow-rate centrifugal atomizing nozzle of this invention is as follows: Liquid enters the annular cavity 4 through the inlet pipe 2, and is stabilized under the guidance of the baffle 9. It then flows out through the bottom guide pipe 5 and falls into the collection area 704 in the center of the triple atomizing disk 7. The DC motor 1 drives the motor shaft 3 and the triple atomizing disk 7 to rotate synchronously at high speed. Under centrifugal force, the liquid entering the collection area 704 is automatically divided according to the liquid supply: under low flow conditions, the liquid mainly enters the inner flow channel 703; when the flow rate increases, the liquid overflows from the inner layer and sequentially enters the middle flow channel 702 and the outer flow channel 701. The liquid is stretched and thinned on the walls of each flow channel to form a liquid film. Finally, at the moment of detachment from the triangular sawtooth 706 at the edge of the disk, it is broken and atomized by high-speed centrifugal force and sprayed into the external space.

[0037] A design method for a high-flow-rate centrifugal atomizing nozzle, including the diameter and included angle of the central disc. The serration height and the width of the flow channel; details are as follows:

[0038] (1) To ensure the liquid flow rate allocated to the inner flow channel This allows the liquid to acquire sufficient radial expansion space, enabling the centrifugal acceleration of the triple atomizing disk 7 to sufficiently thin the liquid film to the preset maximum liquid film thickness h. max (The value range is 10) -5 -1.5×10 -4 Within the specified range, the diameter of the center disk 705 is determined by deriving the following formula. Angle :

[0039] Based on the classic Navier-Stokes equations (NS equations) for Newtonian fluid films on a rotating conical surface, the component of the centrifugal force acting on the liquid film along the wall of the inner channel in a rotating coordinate system is:

[0040] (1)

[0041] Where ρ is the liquid density, with units of kilograms per cubic meter (kg / m³). 3 ); ω is the rotational angular velocity of the triple atomizing disk 7, in radians per second (rad / s); D1 is the diameter of the central disk 705, in meters (m).

[0042] Neglecting Coriolis force and aerodynamic drag, the viscous shear force and centrifugal force within the liquid film are balanced along the wall components of the inner flow channel:

[0043] (2)

[0044] Where μ is the dynamic viscosity of the liquid, and the unit is Pascal-second (Pa·s). The velocity of the liquid is expressed in meters per second (m / s). The thickness of the liquid film is expressed in meters (m).

[0045] Integrating equation (2) yields the velocity distribution within the liquid film (the rate of velocity change between adjacent liquid layers). Then, the integral is performed along the liquid film thickness y, with the upper limit of the integration being the actual liquid film thickness. The rated split volumetric flow rate of the inner channel can be obtained as follows:

[0046] (3)

[0047] Due to discrepancies between theory and practice, a preset maximum liquid film thickness h is introduced. max With respect to actual liquid film thickness Correction coefficient Substitute into the flow equation (Formula (3)) and extract The formula can then be obtained:

[0048] (4)

[0049] Among them, C h The film thickness correction factor has a value range of 0.90-1.10. To ensure that the liquid film can overflow smoothly to the outside, the above equation (4) is transformed and solved to obtain the angle between the channel wall and the horizontal direction. The solution formula is as follows:

[0050] (5)

[0051] (2) Based on Rayleigh-Taylor instability and the fracture mechanism of rotating droplets, the serration height is affected. Derivation:

[0052] The Weber number represents the ratio of fluid inertial force (or centrifugal force) to surface tension:

[0053] (6)

[0054] in, is the surface tension coefficient of the liquid, with units of Newtons per meter (N / m). The radius of rotation (in meters) at the location of the saw teeth.

[0055] At the edge of the triple atomizing disk, the characteristic linear velocity Substituting this into formula (6) and rearranging, we obtain the eccentric Weber terms at the edge:

[0056] (7)

[0057] D pThe target droplet size (in meters) that allows the liquid film to tear smoothly at the serrated edge, C k This is an empirical coefficient (ranging from 1.15 to 1.35) that combines geometry and fluid properties, and the sawtooth height. It must be proportional to the target droplet size and the square root of the Weber number, then:

[0058] (8)

[0059] (3) In order to adjust the flow rate of each channel, the width of each channel is designed. The size of each channel is different, with the outer channel being wider and having a larger flow rate;

[0060] The height difference between the upper surface of the central disk 705 and the upper end face of the inner ring 703 is The width W1 of the inner flow channel satisfies: k1 is a correction factor, ranging from 0.5 to 0.7; the height difference between the upper surface of the central disk 705 and the upper end face of the middle ring 702 is... The width W2 of the intermediate flow channel should satisfy: k2 is a correction factor, ranging from 0.6 to 0.8; the height difference between the upper surface of the central disk 705 and the lower surface of the horizontal portion of the outer disk 701 is... The width W3 of the outer flow channel should satisfy: k3 is a correction factor, with a value ranging from 0.7 to 0.9.

[0061] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A high-flow-rate centrifugal atomizing nozzle, characterized in that, The device includes a DC motor (1), an inlet pipe (2), a guide pipe (5), an annular cavity (4), and a triple atomizing disc (7). The DC motor (1) is installed above the annular cavity (4). The annular cavity (4) is connected to the triple atomizing disc (7) below through multiple evenly distributed guide pipes (5). The inlet pipe (2) extends into the annular cavity (4) from the outer edge of the DC motor (1) in an inclined direction and is connected to it. The motor shaft (3) of the DC motor (1) passes through the annular cavity (4) and its end is fixed to the triple atomizing disc (7). The annular cavity (4) has a central cavity (10) inside, through which the motor shaft (3) passes. Multiple evenly distributed baffles (9) are fixed between the outer wall of the central cavity (10) and the inner wall of the annular cavity (4). The triple atomizing disk (7) consists of a central disk (705), an inner ring (703), a middle ring (702), and an outer disk (701) from the inside out. An inner flow channel is formed between the central disk (705) and the inner ring (703), a middle flow channel is formed between the inner ring (703) and the middle ring (702), and an outer flow channel is formed between the middle ring (702) and the outer disk (701). A liquid collection area (704) is located above the central disk (705). Triangular serrations (706) are provided at the bottom edge of the annular portion of the central disk (705), the bottom edge of the inner ring (703), the bottom edge of the middle ring (702), and the bottom edge of the annular portion of the outer disk (701).

2. The high-flow-rate centrifugal atomizing nozzle according to claim 1, characterized in that, The bottom end of the motor shaft (3) is fixed with a bushing (6), and the upper and lower ends of the bushing (6) are fixed with the outer disk (701) and the central disk (705) respectively.

3. The high-flow-rate centrifugal atomizing nozzle according to claim 2, characterized in that, The central disk (705), inner ring (703), middle ring (702) and outer disk (701) are connected by circumferentially evenly distributed ribs (8). One end of the ribs (8) is fixed to the bushing (6), and the other end passes through each flow channel in the radial direction and is connected to the outer disk (701).

4. The high-flow-rate centrifugal atomizing nozzle according to claim 3, characterized in that, The annular portion of the central disk (705), the inner ring (703), the middle ring (702), and the annular portion of the outer disk (701) are all inclined inward.

5. The high-flow-rate centrifugal atomizing nozzle according to claim 1, characterized in that, The angle between the liquid inlet pipe (2) and the horizontal direction is in the range of 30°-60°.

6. The high-flow-rate centrifugal atomizing nozzle according to claim 1, characterized in that, The thickness of the central disk (705), inner ring (703), middle ring (702) and outer disk (701) is 1-1.5 mm; the materials of the annular cavity (4), guide tube (5), triple atomizing disk (7), bushing (6) and rib plate (8) are polytetrafluoroethylene or composite plastic; the materials of the housing and motor shaft (3) of the DC motor (1) are stainless steel or metal alloy.

7. A design method for a high-flow-rate centrifugal atomizing nozzle based on any one of claims 1-6, characterized in that, In order to utilize the centrifugal acceleration of the triple atomizing disk (7) to sufficiently thin the liquid film to the preset maximum liquid film thickness h max The diameter of the central disk (705) Where μ is the dynamic viscosity of the liquid. The liquid flow rate allocated to the inner channel, ρ is the liquid density, and ω is the rotational angular velocity of the triple atomizing disk (7). C is the angle between the channel wall and the horizontal direction. h h is the film thickness correction factor. max This is the preset maximum liquid film thickness.

8. The design method according to claim 7, characterized in that, Angle between the wall of each flow channel and the horizontal direction .

9. The design method according to claim 7, characterized in that, Height of the saw teeth (706) With the target droplet size D p The terms are directly proportional to the square roots of the eccentric Weber numbers: , where C k This is an empirical coefficient. The surface tension coefficient of the liquid. The radius of rotation is the position of the sawtooth.

10. The design method according to claim 7, characterized in that, The height difference between the upper surface of the central disk and the upper end face of the inner ring is The width W1 of the inner flow channel should satisfy: k1 is a correction factor, ranging from 0.5 to 0.7; the height difference between the upper surface of the central disk and the upper end face of the middle ring is... The width W2 of the intermediate flow channel should satisfy: k2 is a correction factor, ranging from 0.6 to 0.8; the height difference between the upper surface of the central disk and the lower surface of the horizontal portion of the outer disk is... The width W3 of the outer flow channel should satisfy: k3 is a correction factor, with a value ranging from 0.7 to 0.9.

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