GAS-LIQUID TWO-PHASE FLOW ATOMIZING NOZZLE

Abstract

A gas-liquid two-phase flow atomizing nozzle includes a nozzle core, an outer sleeve and an atomizing body. An inner cavity of the nozzle core consists of an inlet tapered section, a jet flow section and an outlet diffusion section. The outlet diffusion section of the nozzle core is connected to an atomizing body mixing chamber. The jet flow section of the nozzle core is in communication with external atmosphere through a core air inlet hole, an air inlet buffering chamber and a sleeve air inlet hole.

Claims

1. A gas-liquid two-phase flow atomizing nozzle, comprising: a nozzle core, an outer sleeve and an atomizing body, wherein an inner cavity of the nozzle core consists of an inlet tapered section, a jet flow section and an outlet diffusion section; along a central axis of the nozzle core, the inlet tapered section gradually shrinks, the jet flow section is cylindrical, and the outlet diffusion section gradually expands, and the outlet diffusion section is in direct communication with an atomizing body mixing chamber; a nozzle core air inlet hole is provided on a wall surface of the nozzle core, a sleeve air inlet hole is provided on a wall surface of the outer sleeve, so that the jet flow section in the inner cavity of the nozzle core is in communication with external atmosphere through the nozzle core air inlet hole, an air inlet buffering chamber and the sleeve air inlet hole; liquid flows along a central axis of the nozzle, and is atomized after sequentially flowing through the inlet tapered section, the jet flow section, the outlet diffusion section, the atomizing body mixing chamber and an atomizing-body outlet; a series of the nozzle core air inlet holes circumferentially and evenly distributed are provided on a wall surface of the jet flow section, and the jet flow section of the inner cavity of the nozzle core is in communication with the air inlet buffering chamber through the nozzle core air inlet holes; the nozzle core and the atomizing body are mounted inside the outer sleeve, and the air inlet buffering chamber is ring-shaped and is located between an inner wall surface of the outer sleeve and an outer wall surface of the nozzle core; the atomizing body comprises the atomizing body mixing chamber as an internal chamber thereof, the atomizing-body outlet is a conical orifice with a fixed diffusion angle, and an inner cavity of the atomizing body mixing chamber is conical-shaped; the atomizing body and the nozzle core are mounted in an internal cavity of the outer sleeve, the atomizing body and the nozzle core are made of a ceramic, stainless steel or brass material, and the outer sleeve is made of a nylon, polyethylene or polytetrafluoroethylene material; parameters including a volume median diameter D.sub.0.5 of spray droplets of the nozzle, a designed flow rate Q of the nozzle and geometrical dimensions of parts of the nozzle satisfy the following relationship: $D_{0.5}=d_2\left(1.92-\frac{300{\rho }_g{d}_3}{\rho d_1}\right)\left[k_1\ln \left(\frac{{\rho }_g{Q}^2}{d_2^3\sigma }\right)-0.004\right]$ and the following constraint conditions: $1.9\times {10}^4\le \frac{\rho Q}{d_2\mu }\le 2.4\times {10}^4$ $2.2\le \frac{N_2{d}_3^2}{N_1{d}_1^2}\le 6.5$ when the volume median diameter D.sub.0.5 of spray droplets of the nozzle is ≥300 μm, $\frac{\rho Q}{d_2\mu }$ has a value range of $1.9\times {10}^4\le \frac{\rho Q}{d_2\mu }\le 2.1\times {10}^4;$ when the volume median diameter D.sub.0.5 of spray droplets of the nozzle is <300 μm, $\frac{\rho Q}{d_2\mu }$ has a value range of $2.1\times {10}^4\le \frac{\rho Q}{d_2\mu }\le 2.4\times {10}^4;$ when a liquid dynamic viscosity μ is ≥0.001 Pa.Math.s, a correction coefficient k.sub.1 has a value range of 0.07≤k.sub.1≤0.10; when the liquid dynamic viscosity μ is <0.001 Pa.Math.s, the correction coefficient k.sub.1 has a value range of 0.10<k.sub.1≤0.12; and in the formulas, D.sub.0.5 is the volume median diameter of spray droplets of the nozzle, measured in m; Q is the designed flow rate of the nozzle, measured in m.sup.3/s; d.sub.1 is a diameter of the nozzle core air inlet hole, measured in m; d.sub.2 is a diameter of the atomizing-body outlet of the nozzle, measured in m; d.sub.3 is a diameter of the sleeve air inlet hole, measured in m; ρ is a liquid density, measured in Kg/m.sup.3; ρ.sub.g is an air density of the external atmospheric environment, measured in Kg/m.sup.3; σ is a liquid surface tension coefficient, measured in N/m; μ is the liquid dynamic viscosity, measured in Pa.Math.s; k.sub.1 is the correction coefficient, wherein k.sub.1=0.07˜0.12; N.sub.1 is a number of the nozzle core air inlet holes, wherein N.sub.1=3˜5, and N.sub.2 is a number of the sleeve air inlet holes.

2. The gas-liquid two-phase flow atomizing nozzle according to claim 1, wherein in main geometrical dimension parameters of the nozzle core, design formulas of a diameter D.sub.1 of the jet flow section, a length L.sub.1 of the jet flow section and a diffusion angle β of the outlet diffusion section are as follows: $D_1=\left(0.34\frac{{\rho }_g{Q}^2}{d_2^3\sigma }+8.91\right)d_2$ $L_1=7{d_1\left(\frac{1000\mu D_1}{\rho Q}\right)}^{0.3}$ $\beta =6°\sim 10°$ wherein, D.sub.1 is the diameter of the jet flow section, measured in m; ρ.sub.g is the air density of the external atmospheric environment, measured in Kg/m.sup.3; Q is the designed flow rate of the nozzle, measured in m.sup.3/s; σ is the liquid surface tension coefficient, measured in N/m; d.sub.2 is the diameter of the atomizing-body outlet of the nozzle, measured in m; L.sub.1 is the length of the jet flow section, measured in m; ρ is the liquid density, measured in Kg/m.sup.3; μ is the liquid dynamic viscosity, measured in Pa.Math.s; an β is the diffusion angle of the outlet diffusion section, measured in °.

3. The gas-liquid two-phase flow atomizing nozzle according to claim 1, wherein in main geometrical dimension parameters of the atomizing body, design formulas of a maximum inner diameter D.sub.2 of the atomizing body mixing chamber and a width b of the air inlet buffering chamber are as follows: $D_2=2.6D_1+L_1\mathrm{tg}\beta$ $b=k_2{D}_1$ wherein when the liquid dynamic viscosity μ is ≥0.001 Pa.Math.s, a correction coefficient k.sub.2 has a value range of 0.6≤k.sub.2≤0.7; when the liquid dynamic viscosity μ is <0.001 Pa.Math.s, the correction coefficient k.sub.2 has a value range of 0.5≤k.sub.2<0.6; and in the formulas, D.sub.2 is the maximum inner diameter of the atomizing body mixing chamber, measured in m; D.sub.1 is the diameter of the jet flow section, measured in m; L.sub.1 is the length of the jet flow section, measured in m; β is a diffusion angle of the outlet diffusion section, measured in °; b is the width of the air inlet buffering chamber, measured in m; and k.sub.2 is the correction coefficient, wherein k.sub.2=0.5˜0.7.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The present invention will be described in further detail below with reference to the accompanying drawings and the detailed description of embodiments, wherein

[0055] FIG. 1 is an axial plane cross-sectional view of a nozzle according to an embodiment of the present invention;

[0056] FIG. 2 is an axial plane cross-sectional view of a nozzle core according to the embodiment;

[0057] FIG. 3 is an axial plane cross-sectional view of the nozzle core and an outer sleeve assembled together according to the embodiment; and

[0058] FIG. 4 is an axial plane cross-sectional view of an atomizing body according to the embodiment.

[0059] In the drawings: 1. nozzle core, 2. outer sleeve, 3. atomizing body, 4. inlet tapered section, 5. nozzle core air inlet hole, 6. jet flow section, 7. outlet diffusion section, 8. diffusion angle β of the outlet diffusion section, 9. length L.sub.1 of the jet flow section, 10. diameter d.sub.1 of the nozzle core air inlet hole, 11. diameter D.sub.1 of the jet flow section, 12. sleeve air inlet hole, 13. air inlet buffering chamber, 14. diameter d.sub.3 of the sleeve air inlet hole, 15. width b of the air inlet buffering chamber, 16. atomizing body mixing chamber, 17. atomizing-body outlet, 18. diameter d.sub.2 of the atomizing-body outlet, 19. maximum inner diameter D.sub.2 of the atomizing body mixing chamber.

DESCRIPTION OF THE EMBODIMENTS

[0060] FIG. 1 to FIG. 4 together determine the structure and geometrical dimensions of a nozzle according to this embodiment, which is a gas-liquid two-phase flow atomizing nozzle having an axisymmetric structure, and includes a nozzle core 1, an outer sleeve 2 and an atomizing body 3. An inner cavity of the nozzle core 1 consists of an inlet tapered section 4, a jet flow section 6 and an outlet diffusion section 7. The outlet diffusion section 7 is in communication with an atomizing body mixing chamber 16. A nozzle core air inlet hole 5 and a sleeve air inlet hole 12 are respectively provided on a wall surface of the nozzle core 1 and a wall surface of the outer sleeve 2, so that the jet flow section 6 in the inner cavity of the nozzle core 1 is in communication with external atmosphere through the nozzle core air inlet hole 5, an air inlet buffering chamber 13 and the sleeve air inlet hole 12. Liquid flows along a central axis of the nozzle, and is atomized after sequentially flowing through the inlet tapered section 4, the jet flow section 6, the outlet diffusion section 7, the atomizing body mixing chamber 16 and an atomizing-body outlet 17. During the high-speed flow of the liquid in the jet flow section 6, hydrostatic pressure is significantly decreased until it is lower than the pressure of the external atmosphere. Thus, driven by the pressure of the external atmosphere, air enters the jet flow section 6 through the sleeve air inlet hole 12, the air inlet buffering chamber 13 and the nozzle core air inlet hole 5, and liquid and air are mixed in the jet flow section 6, the outlet diffusion section 7 and the atomizing body mixing chamber 16 to generate a gas-liquid two-phase flow and produce spray droplets.

[0061] According to conditions such as the operational requirements of the nozzle and the liquid characteristics, first, the values of a volume median diameter D.sub.0.5 of spray droplets, a designed spray flow rate Q, a liquid density ρ, a liquid surface tension coefficient σ, a liquid dynamic viscosity μ and an air density ρ.sub.g of the nozzle under designed working conditions are determined. According to the technical requirements of the design of this embodiment, the volume median diameter D.sub.0.5 of spray droplets is 0.0002 m=200 μm, the designed spray flow rate Q is 1.25×10.sup.−5 m.sup.3/s=0.75 L/min, the liquid density p is 1050 Kg/m.sup.3, the liquid surface tension coefficient σ is 0.065 N/m, the liquid dynamic viscosity μ is 0.00095 Pa.Math.s, and the air density ρ.sub.g is 1.2 Kg/m.sup.3. On the basis of the parameter values determined, a diameter d.sub.1 of the nozzle core air inlet hole, a diameter d.sub.2 of the atomizing-body outlet and a diameter d.sub.3 of the sleeve air inlet hole are specifically designed according to the following three steps.

[0062] First step. According to the requirements on the value of the volume median diameter D.sub.0.5 of spray droplets of the nozzle, the values of the diameter d.sub.1 of the nozzle core air inlet hole and the diameter d.sub.2 of the atomizing-body outlet are determined first, where the diameter d.sub.1 of the nozzle core air inlet hole has a value range of 10D.sub.0.5-15D.sub.0.5 and is 0.002 m=10D.sub.0.5 in this embodiment, the diameter d.sub.2 of the atomizing-body outlet has a value range of 2D.sub.0.5-5D.sub.0.5 and is 0.0006 m=3D.sub.0.5 in this embodiment, and the value of the diameter d.sub.2 of the atomizing-body outlet should satisfy the following constraint condition (1):

[00009]$\begin{array}{cc}1.9\times {10}^4\le \frac{\rho Q}{d_2\mu }\le 2.4\times {10}^4& \left(1\right)\end{array}$

[0063] In the formula, Q is a designed spray flow rate of the nozzle, measured in m.sup.3/s; [0064] d.sub.2 is the diameter of the atomizing-body outlet of the nozzle, measured in m; [0065] ρ is the liquid density, measured in Kg/m.sup.3; and [0066] μ is the liquid dynamic viscosity, measured in Pa.Math.s.

[0067] When the volume median diameter D.sub.0.5 of spray droplets of the nozzle is ≥300 μm,

[00010]$\frac{\rho Q}{d_2\mu }$

has a value range of

[00011]$1.9\times {10}^4\le \frac{\rho Q}{d_2\mu }\le 2.1\times {10}^4;$

when the volume median diameter D.sub.0.5 of spray droplets of the nozzle is <300 μm,

[00012]$\frac{\rho Q}{d_2\mu }$

has a value range of

[00013]$2.1\times {10}^4<\frac{\rho Q}{d_2\mu }\le 2.4\times {10}^4.$

[0068] By substituting the values such as the diameter d.sub.2 of the atomizing-body outlet and the designed spray flow rate Q of this embodiment into the formula, it is obtained that

[00014]$\frac{\rho Q}{d_2\mu }\approx 23026,$

which satisfies the requirement of

[00015]$\mathrm{2.1`}\times {10}^4<\frac{\rho Q}{d_2\mu }\le 2.4\times {10}^4.$

[0069] Second step. After the values of the diameter d.sub.1 of the nozzle core air inlet hole and the diameter d.sub.2 of the atomizing-body outlet are obtained, the parameters such as the volume median diameter D.sub.0.5 of spray droplets, the designed spray flow rate Q, the diameter d.sub.1 of the nozzle core air inlet hole and the diameter d.sub.2 of the atomizing-body outlet are substituted into the relational expression (2), to obtain a value of the diameter d.sub.3 of the sleeve air inlet hole that satisfies the relational expression (2).

[00016]$\begin{array}{cc}{D}_{0.5}=d_2\left(1.92-\frac{300{\rho }_g{d}_3}{\rho d_1}\right)\left[k_1\ln \left(\frac{{\rho }_g{Q}^2}{d_2^3\sigma }\right)-0.004\right]& \left(2\right)\end{array}$

[0070] When the liquid dynamic viscosity μ≥0.001 Pa.Math.s, the correction coefficient k.sub.1 has a value range of 0.07≤k.sub.1≤0.10; when the liquid dynamic viscosity μ<0.001 Pa.Math.s, the correction coefficient k.sub.1 has a value range of 0.10≤k.sub.1≤0.12.

[0071] In the formulas, D.sub.0.5 is the volume median diameter of spray droplets of the nozzle, measured in m; [0072] Q is a designed spray flow rate of the nozzle, measured in m.sup.3/s; [0073] d.sub.1 is the diameter of the nozzle core air inlet hole, measured in m; [0074] d.sub.2 is the diameter of the atomizing-body outlet of the nozzle, measured in m; [0075] d.sub.3 is the diameter of the sleeve air inlet hole, measured in m; [0076] ρ is the liquid density, measured in Kg/m.sup.3; [0077] ρ.sub.g is the air density of the external atmospheric environment, measured in Kg/m.sup.3; [0078] σ is the liquid surface tension coefficient, measured in N/m; and [0079] k.sub.1 is a correction coefficient, where k.sub.1=0.07˜0.12.

[0080] According to the above requirements, the parameters of this embodiment such as the diameter d.sub.1 of the nozzle core air inlet hole, the diameter d.sub.2 of the atomizing-body outlet, the volume median diameter D.sub.0.5 of spray droplets, the designed spray flow rate Q, the diameter d.sub.1 of the nozzle core air inlet hole and the diameter d.sub.2 of the atomizing-body outlet are substituted into the relational expression, to obtain a value of the diameter d.sub.3 of the sleeve air inlet hole that satisfies the relational expression (2), where the value is 0.0043 m, and k.sub.1=0.11.

[0081] Third step. The diameter d.sub.1 of the nozzle core air inlet hole and the diameter d.sub.3 of the sleeve air inlet hole obtained in the first step and the second step are substituted into a constraint condition (3), to determine specific values of the number N.sub.1 of nozzle core air inlet holes and the number N.sub.2 of sleeve air inlet holes. The number N.sub.1 of nozzle core air inlet holes should be selected from a specified range, and the number N.sub.2 of sleeve air inlet holes is designed and selected according to the constraint condition (3).

[00017]$\begin{array}{cc}2.2⩽\frac{N_2{d}_3^2}{N_1{d}_1^2}⩽6.5& \left(3\right)\end{array}$

[0082] Wherein, d.sub.1 is the diameter of the nozzle core air inlet hole, measured in m; [0083] d.sub.3 is the diameter of the sleeve air inlet hole, measured in m; and [0084] N.sub.1 is the number of nozzle core air inlet holes, where N.sub.1=3˜5.

[0085] According to the requirement of the constraint condition (3), by substituting the values of the diameter d.sub.1 of the nozzle core air inlet hole and the diameter d.sub.3 of the sleeve air inlet hole of this embodiment and letting the number N.sub.1 of nozzle core air inlet holes be 3, it is obtained through calculation that the number N.sub.2 of sleeve air inlet holes is 6, and

[00018]$\frac{N_2{d}_3^2}{N_1{d}_1^2}=3.06,$

which satisfies the requirement of the constraint condition (3).

[0086] The inner cavity of the nozzle core 1 consists of the inlet tapered section 4, the jet flow section 6 and the outlet diffusion section 7. Along a central axis of the nozzle core 1, the inlet tapered section 4 gradually shrinks, the jet flow section 6 is cylindrical, and the outlet diffusion section 7 gradually expands. A series of the nozzle core air inlet holes 5 circumferentially and evenly distributed are provided on a wall surface of the jet flow section 6, and the jet flow section 6 of the inner cavity of the nozzle core 1 is in communication with the air inlet buffering chamber 13 through the nozzle core air inlet holes 5. In main geometrical dimension parameters of the nozzle core 1, design formulas of the diameter D.sub.1 11 of the jet flow section, the length L.sub.1 9 of the jet flow section and the diffusion angle β 8 of the outlet diffusion section are as shown in formulas (4), (5) and (6):

[00019]$\begin{array}{cc}{D}_1=\left(0.34\frac{{\rho }_g{Q}^2}{d_2^3\sigma }+8.91\right)d_2& \left(4\right)\end{array}$

[00020]$\begin{array}{cc}{L}_1=7{d_1\left(\frac{1000\mu D_1}{\rho Q}\right)}^{0.3}& \left(5\right)\\ \beta =6°\sim 10°& \left(6\right)\end{array}$

[0087] Wherein, D.sub.1 is the diameter of the jet flow section, measured in m; [0088] ρ.sub.g is the air density of the external atmospheric environment, measured in Kg/m.sup.3; [0089] Q is a designed spray flow rate of the nozzle, measured in m.sup.3/s; [0090] σ is the liquid surface tension coefficient, measured in N/m; [0091] d.sub.1 is the diameter of the nozzle core air inlet hole, measured in m; [0092] d.sub.2 is the diameter of the atomizing-body outlet of the nozzle, measured in m; [0093] L.sub.1 is the length of the jet flow section, measured in m; [0094] ρ is the liquid density, measured in Kg/m.sup.3; [0095] μ is the liquid dynamic viscosity, measured in Pa.Math.s; and [0096] β is the diffusion angle of the outlet diffusion section, measured in °.

[0097] By substituting the above values into the formulas (4), (5) and (6) to calculate the values such as the diameter D.sub.1 11 of the jet flow section of this embodiment, it is obtained that the value of the diameter D.sub.1 11 of the jet flow section is 0.008 m, the value of the length L.sub.1 9 of the jet flow section is 0.012, and the diffusion angle β 8 of the outlet diffusion section is 6°.

[0098] The nozzle core 1 and the atomizing body 3 are mounted inside the outer sleeve 2, and the air inlet buffering chamber 13 is ring-shaped and located between an inner wall surface of the outer sleeve 2 and an outer wall surface of the nozzle core 1. The atomizing body 3 includes the atomizing body mixing chamber 16 as an internal chamber thereof, the atomizing-body outlet 17 is a conical orifice with a fixed diffusion angle, and an inner cavity of the atomizing body mixing chamber 16 is conical-shaped. Along the flow direction of the gas-liquid two-phase flow, the inner diameter of the atomizing-body outlet 17 increases linearly toward the outlet. The atomizing body 3 and the nozzle core 1 are mounted in an internal cavity of the outer sleeve 2. The atomizing body 3 and the nozzle core 1 are made of a ceramic, stainless steel or brass material. The outer sleeve 2 is made of a nylon, polyethylene or polytetrafluoroethylene material. In main geometrical dimension parameters of the atomizing body 3, design formulas of the maximum inner diameter D.sub.2 19 of the atomizing body mixing chamber and the width b 15 of the air inlet buffering chamber are as shown in formulas (7) and (8).

D.sub.2=2.6D.sub.1+L.sub.1tgβ  (7)

b=k.sub.2D.sub.1  (8)

[0099] When the liquid dynamic viscosity μ≥0.001 Pa.Math.s, the correction coefficient k.sub.2 has a value range of 0.6≤k.sub.2≤0.7; when the liquid dynamic viscosity μ<0.001 Pa.Math.s, the correction coefficient k.sub.2 has a value range of 0.5≤k.sub.2<0.6.

[0100] In the formulas, D.sub.2 is the maximum inner diameter of the atomizing body mixing chamber, measured in m; [0101] D.sub.1 is the diameter of the jet flow section, measured in m; [0102] L.sub.1 is the length of the jet flow section, measured in m; [0103] β is the diffusion angle of the outlet diffusion section, measured in °; [0104] b is the width of the air inlet buffering chamber, measured in m; and [0105] k.sub.2 is a correction coefficient, where k.sub.2=0.5-0.7.

[0106] By substituting the above values into the formulas (7) and (8) to calculate the values of the maximum inner diameter D.sub.2 19 of the atomizing body mixing chamber and the width b 15 of the air inlet buffering chamber of this embodiment, it is obtained that the value of the maximum inner diameter D.sub.2 19 of the atomizing body mixing chamber is 0.022 m, and the width b 15 of the air inlet buffering chamber is 0.0045, where k.sub.2=0.55.

[0107] According to the above design and calculation process, the structure and key geometrical dimensions of the nozzle according to this embodiment of the present invention can be obtained. Samples were fabricated and tested based on this embodiment of the present invention. Test data of this embodiment of the present invention was compared with performance data of a conventional single-phase flow atomizing nozzle. The specific results are as shown in the following table.

[0108] Table 1: Comparison of performance data of the embodiment of the present invention and a conventional nozzle

TABLE-US-00001 TABLE 1 Comparison of performance data of the embodiment of the present invention and a conventional nozzle Volume median diameter D.sub.0.5 Spray flow Spray of spray droplets rate Q pressure Nozzle type (μm) (L/min) (MPa) Embodiment of 208 0.61  0.2 MPa the present 203 0.75 0.25 MPa invention 194 0.85  0.3 MPa Conventional 135 0.92  0.2 MPa single-phase fluid 124 1.15 0.25 MPa atomizing nozzle 116 1.29  0.3 MPa

[0109] As shown in Table 1, when the spray pressure is 0.2 MPa to 0.3 MPa, the performance of the nozzle of this embodiment of the present invention can satisfy to a certain degree the specific requirements on the design parameters such as the volume median diameter D.sub.0.5 of spray droplets and the designed spray flow rate Q. Compared with the conventional single-phase flow atomizing nozzle, the nozzle of this embodiment of the present invention obviously has the characteristics of a small spray flow rate and a large droplet size, and under the same spray pressure, the droplet size is generally increased by about 60% than that of the conventional nozzle, and the spray flow rate is decreased by about 35%. Therefore, the nozzle of this embodiment of the present invention is particularly applicable to the technical field of low-amount pesticide spraying and application for plant protection in orchards and facility agriculture.