CN113775844A - Asymmetric spherical pipeline elbow for pneumatic conveying - Google Patents

Asymmetric spherical pipeline elbow for pneumatic conveying Download PDF

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CN113775844A
CN113775844A CN202111163003.3A CN202111163003A CN113775844A CN 113775844 A CN113775844 A CN 113775844A CN 202111163003 A CN202111163003 A CN 202111163003A CN 113775844 A CN113775844 A CN 113775844A
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pipeline
particles
spherical
elbow
pipeline elbow
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CN113775844B (en
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聂利生
路宽
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Taiyuan Dianjin Technology Co ltd
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Taiyuan Dianjin Technology Co ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L43/00—Bends; Siphons
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L57/00—Protection of pipes or objects of similar shape against external or internal damage or wear
    • F16L57/02—Protection of pipes or objects of similar shape against external or internal damage or wear against cracking or buckling
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation

Abstract

The invention particularly relates to an asymmetric spherical pipeline elbow for pneumatic transmission, which solves the problems that the existing pneumatic transmission pipeline elbow is frequently corroded and damaged by the pipe wall, the transmitted particles are damaged, the kinetic energy loss of the transmitted gas is overlarge, and the like. An asymmetric spherical pipeline elbow for pneumatic transmission comprises a spherical pipeline elbow, wherein a feeding pipeline communicated with the spherical pipeline elbow is horizontally arranged and is connected with the left front lower part of the spherical pipeline elbow; the discharge pipeline communicated with the spherical pipeline elbow is vertically arranged and is connected with the left rear upper part of the spherical pipeline elbow; the inner diameter of the spherical pipeline elbow is 240 mm; the inner diameters of the feeding pipeline and the discharging pipeline are both less than or equal to 100 mm; the eccentricity of the pipeline is less than or equal to 75 mm. The invention ensures that the airflow presents vortex and is decelerated and phase-changed in the flowing process of the particles, and then the speed is reduced by the buffering of the collision particle pad, thereby reducing the collision speed of the particles and the wall surface, reducing the direct frontal collision between the particles and the wall surface and reducing the particle breakage rate.

Description

Asymmetric spherical pipeline elbow for pneumatic conveying
Technical Field
The invention relates to the technical field of pipeline transportation of particulate materials, in particular to an asymmetric spherical pipeline elbow for pneumatic transportation.
Background
Pneumatic transportation is a new transportation mode for transporting granular materials in a closed pipeline by using flowing gas, and is widely applied to the industries of chemical industry, metallurgy, pharmacy, electronics, food, agriculture, animal husbandry, fishing and the like. At present, arc-shaped common pipeline elbows are often used in pneumatic conveying equipment.
However, the prior pneumatic conveying equipment has the following problems in use due to the practice that: when transporting some particles with larger diameter and poor flowability, such as: the problems of erosion and damage of pipe walls, breakage of transported particles, excessive loss of kinetic energy of transported gas and the like frequently occur at the elbow of pipelines of grains, seeds, feeds, medicines and the like. Therefore, the pipeline elbow with a brand-new structure is needed to be invented, the damage of the pipeline elbow and the damage of transported particles in the transportation process are reduced, and the energy utilization rate of transported gas is improved.
Disclosure of Invention
The invention provides an asymmetric spherical pipeline elbow for pneumatic transmission, which aims to solve the problems that the existing pneumatic transmission pipeline elbow is frequently corroded and damaged by pipe wall, transported particles are damaged, kinetic energy loss of transported gas is overlarge and the like.
The invention is realized by adopting the following technical scheme:
an asymmetric spherical pipeline elbow for pneumatic transmission comprises a spherical pipeline elbow, wherein a feeding pipeline communicated with the spherical pipeline elbow is horizontally arranged and is connected with the left front lower part of the spherical pipeline elbow; the discharge pipeline communicated with the spherical pipeline elbow is vertically arranged and is connected with the left rear upper part of the spherical pipeline elbow; wherein the inner diameter of the spherical pipe elbow is 240 mm; the inner diameter of the feeding pipeline is consistent with the inner diameter D of the discharging pipeline, and the inner diameters D of the feeding pipeline and the discharging pipeline are both less than or equal to 100 mm; and setting the distance from the sphere center of the spherical pipeline elbow to the axis of the discharge pipeline as the pipeline eccentricity E, wherein the pipeline eccentricity E is less than or equal to 75 mm.
Further, when the spherical pipeline elbow conveys particles, the air flow velocity V is more than or equal to 20 m/s; the diameter d of the granules is less than or equal to 6mm, and the density is 600kg/m3The shear modulus is 20MPa, the elastic modulus is 50MPa, the initial speed is 15m/s, and the mass flow is less than or equal to 1.3 kg/s.
Further, the selection ranges of the inner diameters D of the feeding pipeline and the discharging pipeline are both smaller than 90 mm; the selection range of the pipeline eccentricity E is less than 52 mm; the selection range of the air flow velocity V is more than 25 m/s; the selection range of the particle diameter d is less than 5 mm;
the parameters are selected through an orthogonal experiment, and the specific selection process is realized by adopting the following steps:
s1: determining a spherical pipeline elbow particle flow and damage analysis method:
s1.1: analyzing the motion process of the particles in the spherical pipeline elbow by adopting a discrete element method, wherein the control equation of the discrete elements of the particles is as follows:
Figure BDA0003290887340000021
Figure BDA0003290887340000022
wherein m isp、νp、IpAnd ωpMass flow, translational velocity, rotational inertia and angular velocity of the particles respectively; g is the acceleration of gravity; fwp、FppAnd MpThe force of the wall surface to the particles, the acting force among the particles and the moment borne by the particles are respectively; ffIs the force of the fluid on the particles;
s1.2: analyzing the flowing process and the vortex structure of the gas in the spherical pipeline elbow by adopting a computational fluid dynamics method; the hydrodynamic N-S equation is:
Figure BDA0003290887340000023
wherein ρ is a gas phase density; v. ofi、vjIs the gas phase velocity component; x is the number ofjIs a spatial coordinate; p is pressure; tau isijIs the stress tensor; ρ gjIs the gravity component; sDAn additional momentum term for the discrete phase;
s1.3: analysis of the flow-through of gases and particles in spherical pipe bends by means of a coupling of computational fluid dynamics with discrete elementsThe process and the interplay of particles and gas vortices; wherein, in order to characterize the influence of the particles on the fluid, an additional momentum term S for increasing the influence of the discrete relative momentum of the particles in the fluid mechanics N-S equationD(ii) a To characterize the effect of a fluid on a particle, the force F of the fluid on the particle is increased in the particle discrete element equationf；
S1.4: calculating the erosion rate of the pipe wall of the spherical pipe elbow under the particle erosion by adopting an empirical formula of an Oka erosion model, wherein the erosion rate formula is as follows:
Figure BDA0003290887340000031
wherein R iseThe wall surface wear rate; n is a radical ofpIs the number of colliding particles; m ispIs the particle mass flow rate; c (d)p) Is a particle attribute correlation function; theta is the impingement angle of the particles on the wall surface; f (θ) is a function of impact angle effect on wear; u is the velocity of the particles relative to the wall; b (v) is a function of relative velocity; a. thefaceIs the area of the wall surface;
s2: selecting the eccentricity E of the pipeline:
setting D to be 90mm, D to be 5mm and V to be 25m/s, and analyzing the flow characteristics of particles in the spherical pipeline elbow when E to be 52mm, 63.5mm and 75mm by utilizing computational fluid dynamics software and discrete element software coupling, wherein the discharge pipeline is tangent to the inner wall of the spherical pipeline elbow when E to be 75 mm;
the analysis results show that: a) when E is 52mm, 63.5mm and 75mm, the maximum erosion rate is 3.76, 5.71 and 16.5 respectively, and the unit of the maximum erosion rate is 10-4kg/(m2s); b) when E is 52mm and 63.5mm, the particles enter the spherical pipeline elbow and collide with the flowing particles in the spherical pipeline elbow for buffering, partial energy is lost, and the speed of the particles at the outlet is reduced; c) when E is 52mm, 63.5mm and 75mm, the average total energy of the particles in the spherical pipe elbow is 53, 54 and 62 respectively, and the unit of the average total energy is 10-5J；
S3: selection of particle diameter d:
setting D to be 90mm, E to be 63.5mm and V to be 25m/s, and analyzing the flow characteristics of particles in the spherical pipeline elbow when D is 4mm, 5mm and 6mm by utilizing the coupling of computational fluid dynamics software and discrete element software;
the analysis results show that: a) when d is 4mm, 5mm and 6mm, the maximum erosion rates are 5.88, 5.71 and 6.82 respectively, and the unit of the maximum erosion rate is 10-4kg/(m2s); b) when d is 4mm, 5mm or 6mm, the larger the particle diameter d is, the smaller the velocity of the particles at the outlet of the spherical pipeline elbow is;
s4: selecting the inner diameters D of the feeding pipeline and the discharging pipeline:
setting D to be 5mm, E to be 63.5mm and V to be 25m/s, and analyzing the flow characteristics of particles in the spherical pipeline elbow when D is 80mm, 90mm and 100mm by utilizing the coupling of computational fluid dynamics software and discrete element software;
the analysis results show that: a) when D is 80mm, 90mm and 100mm, the maximum erosion rates are respectively 5.1, 5.71 and 4.67, and the unit of the maximum erosion rate is 10-4kg/(m2s); b) when D is 80mm, 90mm and 100mm, the larger the inner diameter D of the feeding pipeline and the discharging pipeline is, the smaller the speed of the particles at the outlet of the elbow of the spherical pipeline is; c) when D is 80mm, 90mm and 100mm, the average total energy of the particles in the spherical pipe elbow is 52, 54 and 30 respectively, and the unit of the average total energy is 10-5J；
S5: selecting the air flow velocity V:
setting D to be 5mm, E to be 63.5mm and D to be 90mm, and analyzing the flow characteristics of the particles in the spherical pipeline elbow when V is 20m/s, 25m/s and 30m/s by utilizing the coupling of computational fluid dynamics software and discrete element software;
the analysis results show that: a) when V is 20m/s, 25m/s and 30m/s, the maximum erosion rates are respectively 5.5, 5.71 and 8.0, and the unit of the maximum erosion rate is 10-4kg/(m2s); b) when V is 20m/s, 25m/s and 30m/s, the larger the air flow velocity V is, the larger the velocity of the particles at the outlet of the spherical pipe elbow is; c) when V is 20m/s, 25m/s and 30m/s, the average total energy of the particles in the spherical pipe elbow is 52, 54 and 98 respectively, and the unit of the average total energy is 10-5J。
The invention designs the asymmetric spherical pipeline elbow for pneumatic transmission, so that the airflow presents a vortex in the process of flowing particles in the spherical pipeline elbow, and the particles are fully mixed and carried by the gas. The inlet particles A are mixed with the internal circulation particles B firstly, the speed is reduced and the phase is changed, and then the speed is reduced through the buffering of the collision particle pad, so that the speed reduction for two times and the phase change for one time are completed, the collision speed of the particles and the wall surface is reduced, the direct frontal collision between the particles and the wall surface is reduced, the force of the particles impacting the wall surface is less, and the particle breakage rate is reduced. The concentrated impact of the particles on a certain area is reduced, so that the maximum erosion rate of the particles is obviously reduced compared with that of the common pipeline elbow. The invention avoids the problems that large particles in the common pipeline elbow have poor fluidity and are deposited on one side of the inner wall of the pipeline under the action of inertia force, thereby improving the particle transportation speed. The invention effectively solves the problems that the pipe wall is frequently eroded and damaged, transported particles are damaged, kinetic energy loss of transported gas is overlarge and the like at the elbow of the existing pneumatic transport pipeline.
Table 1 is a statistical table of the pipeline erosion results of the ordinary pipeline elbow and the spherical pipeline elbow.
Figure BDA0003290887340000051
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a schematic side view of FIG. 1;
FIG. 3 is a schematic top view of FIG. 1;
FIG. 4 is a reference graph of the velocity distribution of particles in a spherical pipe elbow of the present invention;
FIG. 5 is a reference view of the flow of particles in the spherical pipe elbow of the present invention from a bottom perspective;
FIG. 6 is a schematic view of a flow slice of particles in a spherical pipe elbow of the present invention;
FIG. 7 is a reference graph of the velocity distribution of particles in a conventional pipe bend according to the present invention;
FIG. 8 is a flow diagram of the flow of particles through a spherical pipe elbow of the present invention;
FIG. 9 is an erosion cloud on the inside of a conventional pipe bend according to the present invention;
FIG. 10 is an erosion cloud on the inside of a spherical pipe elbow of the present invention;
FIG. 11 is a cloud of erosion of the inner wall of a spherical pipe elbow with pipe eccentricities E of 52mm, 63.5mm and 75 mm;
FIG. 12 is a graph of the velocity profile of particles inside a spherical pipe bend and at the outlet at 52mm, 63.5mm, 75mm eccentricity E of the pipe;
FIG. 13 is a cloud of erosion of the inner wall of a spherical pipe elbow with particle diameters d of 4mm, 5mm, and 6 mm;
FIG. 14 is a graph showing the velocity distribution of particles at the outlet and inside the spherical pipe elbow when the diameter d of the particles is 4mm, 5mm, and 6 mm;
FIG. 15 is a cloud of erosion on the inner wall of a spherical pipe elbow when the inner diameters D of the feeding pipe and the discharging pipe are 80mm, 90mm and 100 mm;
FIG. 16 is a velocity distribution diagram of particles at the inner and outlet of a spherical pipe elbow when the inner diameters D of a feeding pipe and a discharging pipe are 80mm, 90mm and 100 mm;
FIG. 17 is a cloud of erosion of the inner wall of a spherical pipe bend at air velocities V of 20m/s, 25m/s, and 30 m/s;
FIG. 18 is a velocity profile of particles inside a spherical pipe bend, at an outlet, at 20m/s, 25m/s, 30m/s air velocity V;
in the figure, 1-a spherical pipe elbow, 2-a feeding pipe and 3-a discharging pipe.
Detailed Description
An asymmetric spherical pipeline elbow for pneumatic transmission is shown in attached figures 1, 2 and 3, and comprises a spherical pipeline elbow 1, wherein a feeding pipeline 2 communicated with the spherical pipeline elbow 1 is horizontally arranged and is connected with the left front lower part of the spherical pipeline elbow 1; the discharge pipeline 3 communicated with the spherical pipeline elbow 1 is vertically arranged and is connected with the left rear upper part of the spherical pipeline elbow 1; wherein the inner diameter of the spherical pipe elbow 1 is 240 mm; the inner diameter of the feeding pipeline 2 is consistent with the inner diameter D of the discharging pipeline 3, and the inner diameters D of the feeding pipeline and the discharging pipeline are both less than or equal to 100 mm; the distance from the sphere center of the spherical pipeline elbow 1 to the axis of the discharge pipeline 3 is set as the pipeline eccentricity E, and the pipeline eccentricity E is less than or equal to 75 mm.
The invention designs an asymmetric spherical pipeline elbow for pneumatic transmission, and because the axes of a feeding pipeline 2 and a discharging pipeline 3 of the spherical pipeline elbow 1 are not symmetric, the flow of gas in the spherical pipeline elbow 1 is in a 3D vortex-shaped structure, as shown in attached figures 4, 5, 6, 8 and 10, particles enter the spherical pipeline elbow 1 to generate a rotational flow, namely the particles at an outlet are rotational flow. Under the action of the rotational flow, the particles in the spherical pipeline elbow 1 are divided into three states: inlet particles A, internal circulation particles B and outlet particles C. High-speed import granule A gets into spherical pipeline elbow 1 after earlier with the internal circulation granule B mixture of low-speed, the phase is changeed to the deceleration under the combined action of internal circulation granule B and vortex, dashes into and piles up the granule pad, avoids colliding with the wall. The inlet particles A and the particles on the inner wall of the sphere form 30-60 degrees of collision, buffer and flow into the internal circulation particles B after speed reduction. The internal circulation particles B circularly flow along the inner wall of the sphere of the spherical pipeline elbow 1 under the pushing of the vortex. When the internally circulating particles B pass through the outlet, a part of the internally circulating particles B flows out of the outlet along with the gas flow to form outlet particles C; the other part of the internal circulating particles B circularly flow along the inner wall of the sphere of the spherical pipeline elbow 1, and are mixed with the inlet particles A at the inlet again to enter the next circulation. Therefore, the particle flow is decelerated and collision buffered, the collision times in unit area are relatively less due to the larger area of the ball and the air vortex, and the erosion rate is obviously reduced compared with that of the common pipeline elbow. Because the buffering effect of the right internal circulation particles B avoids the direct collision of the particles, the particles can be protected to a certain extent, and the breakage of the particles is reduced.
Compared with the common pipeline elbow, the particle flow and erosion characteristics of the invention are analyzed, and the generation mechanism and the analysis process are as follows:
one is as follows: the particle flow characteristic of the spherical pipeline elbow is as follows:
the motion state of the particles in the common pipeline elbow and the spherical pipeline elbow is shown in attached figures 7 and 4; large particles in a common pipeline elbow have poor flowability and are deposited on one side of the inner wall of the pipeline under the action of inertia force, so that the pneumatic efficiency of the particles close to the wall surface is low, and the speed is low; the spherical pipeline elbow has the advantages that due to the fact that gas flows are of the special 3D vortex-shaped structure, particles at the outlet are in a rotational flow mode, the particles are uniformly distributed around the spherical pipeline elbow under the effect of centrifugal force, excellent scattering is achieved, pneumatic efficiency is good, and particle speed is high. The particle flow at the outlet of the spherical pipeline elbow is rotational flow, and the problems of high speed, particle breakage, pipeline blockage, pipe wall abrasion and the like of the subsequent conveying critical gas flow can be effectively solved.
The second step is as follows: the spherical pipeline elbow has the characteristics of erosion:
the erosion of the particles to the common pipeline elbow and the spherical pipeline elbow is shown in the attached figures 9 and 10 and table 1; from this it can be seen that: the impact velocity of particles in the common pipeline elbow is high, the erosion positions are relatively concentrated, and the erosion rate is high; the impact velocity of the particles in the spherical pipeline elbow is low, the erosion position is dispersed, the erosion route is the rotational flow route of the particles, and the maximum erosion rate is reduced by about 43 percent compared with the common pipeline elbow.
And thirdly: the protection characteristic of the elbow eddy current of the spherical pipeline to particles
The damage of the particles was judged by counting particles having a collision force with the wall surface of more than 2N within 1 second. The fewer particles with a collision force greater than 2N, the less likely the particles will fragment. The statistical result of the damaged particles shows that the number of particles with the collision force larger than 2N in the common pipeline elbow is 6500, and the number of particles with the collision force larger than 2N in the spherical pipeline elbow is 6100. The analysis shows that: although the collision speed of the particles of the ordinary pipe elbow is high, the particles form a certain angle with the wall surface during collision, so the collision force is small, and the particles can be protected to a certain extent. In the spherical pipe elbow, after mixing, buffering and turning, particles collide with the wall surface at a certain angle, so that the collision force is small. Compared with the prior art, the spherical pipeline elbow has slightly stronger particle breakage resistance than the common pipeline elbow.
When the spherical pipeline elbow 1 transports particles, the air flow velocity V is more than or equal to 20 m/s; the diameter d of the granules is less than or equal to 6mm, and the density is 600kg/m3The shear modulus is 20MPa, the elastic modulus is 50MPa, the initial speed is 15m/s, and the mass flow is less than or equal to 1.3 kg/s.
The selection ranges of the inner diameters D of the feeding pipeline 2 and the discharging pipeline 3 are both less than 90 mm; the selection range of the pipeline eccentricity E is less than 52 mm; the selection range of the air flow velocity V is more than 25 m/s; the selection range of the particle diameter d is less than 5 mm;
the parameters are selected through an orthogonal experiment, and the specific selection process is realized by adopting the following steps:
s1: determining a particle flow and damage analysis method of the spherical pipeline elbow 1:
s1.1: analyzing the motion process of the particles in the spherical pipeline elbow 1 by adopting a discrete element method, wherein the control equation of the discrete elements of the particles is as follows:
Figure BDA0003290887340000091
Figure BDA0003290887340000092
wherein m isp、νp、IpAnd ωpMass flow, translational velocity, rotational inertia and angular velocity of the particles respectively; g is the acceleration of gravity; fwp、FppAnd MpThe force of the wall surface to the particles, the acting force among the particles and the moment borne by the particles are respectively; ffIs the force of the fluid on the particles;
s1.2: analyzing the flowing process and the vortex structure of the gas in the spherical pipeline elbow 1 by adopting a computational fluid dynamics method; the hydrodynamic N-S equation is:
Figure BDA0003290887340000093
wherein ρ is a gas phase density; v. ofi、vjIs the gas phase velocity component; x is the number ofjIs a spatial coordinate; p is pressure; tau isijIs the stress tensor; ρ gjIs the gravity component; sDAn additional momentum term for the discrete phase;
s1.3: analyzing the flowing process of gas and particles in the spherical pipe elbow 1 and the mutual influence of the particles and gas vortex by adopting a method of coupling computational fluid dynamics and discrete elements; wherein, in order to characterize the influence of the particles on the fluid, an additional momentum term S for increasing the influence of the discrete relative momentum of the particles in the fluid mechanics N-S equationD(ii) a To characterize the effect of a fluid on a particle, the force F of the fluid on the particle is increased in the particle discrete element equationf；
S1.4: calculating the erosion rate of the pipe wall of the spherical pipe elbow 1 under the particle erosion by adopting an empirical formula of an Oka erosion model, wherein the erosion rate formula is as follows:
Figure BDA0003290887340000094
wherein R iseThe wall surface wear rate; n is a radical ofpIs the number of colliding particles; m ispIs the particle mass flow rate; c (d)p) Is a particle attribute correlation function; theta is the impingement angle of the particles on the wall surface; f (θ) is a function of impact angle effect on wear; u is the velocity of the particles relative to the wall; b (v) is a function of relative velocity; a. thefaceIs the area of the wall surface;
s2: selecting the eccentricity E of the pipeline:
setting D to be 90mm, D to be 5mm and V to be 25m/s, and analyzing the flow characteristics of particles in the spherical pipeline elbow 1 when E to be 52mm, 63.5mm and 75mm by utilizing computational fluid dynamics software and discrete element software coupling, wherein the discharge pipeline 3 is tangent to the inner wall of the spherical pipeline elbow 1 when E to be 75 mm;
the analysis results show that: a) the erosion cloud picture of the inner wall of the spherical pipeline elbow 1 under different pipeline eccentricities E is shown in the attached figure 11, when E is 52mm, 63.5mm and 75mm, the maximum erosion rates are 3.76, 5.71 and 16.5 respectively, and the unit of the maximum erosion rate is 10-4kg/(m2s); the smaller the eccentricity E of the pipeline is, the larger the impact angle is, so that the erosion rate is smaller, and when the eccentricity of the pipeline is 52mm and 63.5mm, the buffering effect of the internal circulation particles B avoids the direct collision of the particles with the pipe wall, thereby protecting the pipe wall. When the eccentricity of the pipelineWhen the diameter is 75mm, the discharge pipeline 3 is tangent to the wall surface of the inner wall of the spherical pipeline elbow 1, particles directly collide with the pipe wall after entering the spherical pipeline elbow 1 without buffering, so that the erosion is serious, and the erosion cloud picture is similar to the common pipeline elbow in an inverted V shape. b) The velocity distribution diagram of the particles at the inner part and the outlet of the spherical pipeline elbow with different pipeline eccentricities E is shown in figure 12, when the pipeline eccentricities are 52mm and 63.5mm, the particles enter the spherical pipeline elbow 1 to collide with the internal circulation particles B for buffering, partial energy is lost, and the velocity of the outlet particles is reduced. When the eccentricity of the pipeline is 75mm, the discharge pipeline 3 is tangent to the wall surface of the inner wall of the spherical pipeline elbow 1, particles directly collide with the pipe wall after entering the spherical pipeline elbow and are not buffered by the internal circulating particles B, so that the energy loss is relatively small, and the particle outlet speed is high. It is shown that proper reduction of the eccentricity of the duct increases the velocity of the exiting particles without changing the total energy of the gas. c) When E is 52mm, 63.5mm and 75mm, the average total energy of the particles in the spherical pipe elbow 1 is 53, 54 and 62 respectively, and the unit of the average total energy is 10-5J；
S3: selection of particle diameter d:
setting D to be 90mm, E to be 63.5mm and V to be 25m/s, and analyzing the flow characteristics of the particles in the spherical pipeline elbow 1 when D is 4mm, 5mm and 6mm by utilizing the coupling of computational fluid dynamics software and discrete element software;
the analysis results show that: a) the erosion cloud pictures of the inner wall of the spherical pipeline elbow 1 under different particle diameters d are shown in attached figure 13, when the particle diameter d is 6mm, the erosion of the inner wall of the spherical pipeline elbow 1 is higher than that when the particle diameter d is 4mm and 5 mm; when d is 4mm, 5mm and 6mm, the maximum erosion rates are 5.88, 5.71 and 6.82 respectively, and the unit of the maximum erosion rate is 10-4kg/(m2s); b) velocity distribution diagrams of particles inside and at the outlet of the spherical pipe elbow 1 under different particle diameters d are shown in the attached figure 14, when d is 4mm, 5mm and 6mm, the larger the particle diameter d is, the larger the particle mass is, and the smaller the velocity of the particles at the outlet of the spherical pipe elbow 1 is;
s4: selecting the inner diameters D of the feeding pipeline 2 and the discharging pipeline 3:
setting D to be 5mm, E to be 63.5mm and V to be 25m/s, and analyzing the flow characteristics of the particles in the spherical pipeline elbow 1 when D is 80mm, 90mm and 100mm by utilizing the coupling of computational fluid dynamics software and discrete element software;
the analysis results show that: a) the erosion cloud pictures of the inner wall of the spherical pipe elbow 1 with different D values are shown in figure 15, when D is 80mm, 90mm and 100mm, the maximum erosion rate is 5.1, 5.71 and 4.67 respectively, and the unit of the maximum erosion rate is 10-4kg/(m2s); when D is 90mm, the erosion is maximum; when D is 80mm and D is 100mm, the erosion is small. In addition, the erosion rates are not greatly different from each other at the inner diameter D value, and the erosion positions are also substantially uniform. b) The velocity distribution diagram of inside, the export granule of spherical pipeline elbow 1 when different D values is shown in figure 16, and when D80 mm, 90mm, 100mm, the internal diameter D of charge-in pipeline 2, ejection of compact pipeline 3 is big more, and the velocity of spherical pipeline elbow 1 export granule is little, and the reason is because: the increase of internal diameter D has increased to a certain extent that the distance between inlet channel 2, ejection of compact pipeline 3 and spherical pipeline elbow 1 center increases for the granule increases at the inside stroke of spheroid, and energy loss increases thereupon, makes export granule speed step-down. c) When D is 80mm, 90mm and 100mm, the average total energy of the particles in the spherical pipe elbow 1 is 52, 54 and 30 respectively, and the unit of the average total energy is 10-5J；
S5: selecting the air flow velocity V:
setting D to be 5mm, E to be 63.5mm and D to be 90mm, and analyzing the particle flow characteristics in the spherical pipeline elbow 1 when V is 20m/s, 25m/s and 30m/s by utilizing the coupling of computational fluid dynamics software and discrete element software;
the analysis results show that: a) the erosion cloud picture of the inner wall of the spherical pipe elbow 1 at different air flow rates V is shown in fig. 17, when V is 20m/s, 25m/s and 30m/s, the maximum erosion rates are 5.5, 5.71 and 8.0 respectively, and the unit of the maximum erosion rate is 10-4kg/(m2s); as the air flow velocity V increases, the particle velocity also increases and the duct erosion rate increases. b) The velocity distribution diagram of the particles at the inner and outlet of the spherical pipe elbow at different air flow rates V is shown in fig. 18, when V is 20m/s, 25m/s and 30m/s, the larger the air flow rate V is, the larger the velocity of the particles at the outlet of the spherical pipe elbow 1 is; the velocity of the air flow velocity V is increased, the particle velocity is increased, and the particles are dischargedThe velocity increases, the average energy of the particles is proportional to the velocity squared, and the average energy increases as the square of the velocity of the air increases from 20m/s to 30 m/s. c) When V is 20m/s, 25m/s and 30m/s, the average total energy of the particles in the spherical pipe elbow 1 is 52, 54 and 98 respectively, and the unit of the average total energy is 10-5J。
Example 1
An asymmetric spherical pipeline elbow for pneumatic transmission comprises a spherical pipeline elbow 1, wherein a feeding pipeline 2 communicated with the spherical pipeline elbow 1 is horizontally arranged and is connected with the left front lower part of the spherical pipeline elbow 1; the discharge pipeline 3 communicated with the spherical pipeline elbow 1 is vertically arranged and is connected with the left rear upper part of the spherical pipeline elbow 1; wherein the inner diameter of the spherical pipe elbow 1 is 240 mm; the inner diameter of the feeding pipeline 2 is consistent with the inner diameter D of the discharging pipeline 3, and the inner diameters D of the feeding pipeline and the discharging pipeline are both 100 mm; the distance from the sphere center of the spherical pipeline elbow 1 to the axis of the discharge pipeline 3 is set as the pipeline eccentricity E, and the pipeline eccentricity E is 75 mm.
When the spherical pipeline elbow 1 transports particles, the air flow velocity V is 30 m/s; the granules have a diameter d of 6mm and a density of 600kg/m3The shear modulus was 20MPa, the elastic modulus was 50MPa, the initial velocity was 15m/s, and the mass flow was 1.3 kg/s.
Example 2
An asymmetric spherical pipeline elbow for pneumatic transmission comprises a spherical pipeline elbow 1, wherein a feeding pipeline 2 communicated with the spherical pipeline elbow 1 is horizontally arranged and is connected with the left front lower part of the spherical pipeline elbow 1; the discharge pipeline 3 communicated with the spherical pipeline elbow 1 is vertically arranged and is connected with the left rear upper part of the spherical pipeline elbow 1; wherein the inner diameter of the spherical pipe elbow 1 is 240 mm; the inner diameter of the feeding pipeline 2 is consistent with the inner diameter D of the discharging pipeline 3, and the inner diameters D of the feeding pipeline and the discharging pipeline are both 80 mm; the distance from the sphere center of the spherical pipeline elbow 1 to the axis of the discharge pipeline 3 is set as the pipeline eccentricity E, and the pipeline eccentricity E is 52 mm.
When the spherical pipeline elbow 1 transports particles, the air flow velocity V is 20 m/s; the granules have a diameter d of 4mm and a density of 600kg/m3A shear modulus of 20MPa and an elastic modulus of 50MPa, initial velocity of 15m/s, and mass flow rate of 0.8 kg/s.
Example 3
An asymmetric spherical pipeline elbow for pneumatic transmission comprises a spherical pipeline elbow 1, wherein a feeding pipeline 2 communicated with the spherical pipeline elbow 1 is horizontally arranged and is connected with the left front lower part of the spherical pipeline elbow 1; the discharge pipeline 3 communicated with the spherical pipeline elbow 1 is vertically arranged and is connected with the left rear upper part of the spherical pipeline elbow 1; wherein the inner diameter of the spherical pipe elbow 1 is 240 mm; the inner diameter of the feeding pipeline 2 is consistent with the inner diameter D of the discharging pipeline 3, and the inner diameters D of the feeding pipeline and the discharging pipeline are both 90 mm; the distance from the sphere center of the spherical pipeline elbow 1 to the axis of the discharge pipeline 3 is set as the pipeline eccentricity E, and the pipeline eccentricity E is 63.5 mm.
When the spherical pipeline elbow 1 transports particles, the air flow velocity V is 25 m/s; the granules have a diameter d of 4mm and a density of 600kg/m3The shear modulus was 20MPa, the elastic modulus was 50MPa, the initial velocity was 15m/s, and the mass flow was 1.0 kg/s.

Claims (3)

1. The utility model provides an asymmetric spherical pipeline elbow that pneumatic transmission used which characterized in that: comprises a spherical pipeline elbow (1), wherein a feeding pipeline (2) communicated with the spherical pipeline elbow (1) is horizontally arranged and is connected with the left front lower part of the spherical pipeline elbow (1); the discharge pipeline (3) communicated with the spherical pipeline elbow (1) is vertically arranged and is connected with the left rear upper part of the spherical pipeline elbow (1); wherein the inner diameter of the spherical pipe elbow (1) is 240 mm; the inner diameter of the feeding pipeline (2) is consistent with the inner diameter D of the discharging pipeline (3), and the inner diameters D of the feeding pipeline and the discharging pipeline are both less than or equal to 100 mm; the distance from the spherical center of the spherical pipeline elbow (1) to the axis of the discharge pipeline (3) is set as the pipeline eccentricity E, and the pipeline eccentricity E is less than or equal to 75 mm.
2. The asymmetric spherical pipe elbow for pneumatic conveying according to claim 1, wherein: when the spherical pipeline elbow (1) transports particles, the air flow velocity V is more than or equal to 20 m/s; the diameter d of the granules is less than or equal to 6mm, and the density is 600kg/m3A shear modulus of 20MPa and a modulus of elasticityThe modulus of elasticity is 50MPa, the initial velocity is 15m/s, and the mass flow is less than or equal to 1.3 kg/s.
3. The asymmetric spherical pipe elbow for pneumatic conveying according to claim 2, characterized in that: the selection ranges of the inner diameters D of the feeding pipeline (2) and the discharging pipeline (3) are both less than 90 mm; the selection range of the pipeline eccentricity E is less than 52 mm; the selection range of the air flow velocity V is more than 25 m/s; the selection range of the particle diameter d is less than 5 mm;
the parameters are selected through an orthogonal experiment, and the specific selection process is realized by adopting the following steps:
s1: the method for analyzing the particle flow and damage of the spherical pipeline elbow (1) comprises the following steps:
s1.1: analyzing the motion process of the particles in the spherical pipeline elbow (1) by adopting a discrete element method, wherein the control equation of the discrete elements of the particles is as follows:
Figure FDA0003290887330000011
Figure FDA0003290887330000012
wherein m isp、νp、IpAnd ωpMass flow, translational velocity, rotational inertia and angular velocity of the particles respectively; g is the acceleration of gravity; fwp、FppAnd MpThe force of the wall surface to the particles, the acting force among the particles and the moment borne by the particles are respectively; ffIs the force of the fluid on the particles;
s1.2: analyzing the flowing process and the vortex structure of the gas in the spherical pipeline elbow (1) by adopting a computational fluid dynamics method; the hydrodynamic N-S equation is:
Figure FDA0003290887330000021
wherein ρ is a gas phase density; v. ofi、vjIs the gas phase velocity component; x is the number ofjIs a spatial coordinate; p is pressure; tau isijIs the stress tensor; ρ gjIs the gravity component; sDAn additional momentum term for the discrete phase;
s1.3: analyzing the flowing process of gas and particles in the spherical pipeline elbow (1) and the mutual influence of the particles and gas vortex by adopting a method of coupling computational fluid dynamics and discrete elements; wherein, in order to characterize the influence of the particles on the fluid, an additional momentum term S for increasing the influence of the discrete relative momentum of the particles in the fluid mechanics N-S equationD(ii) a To characterize the effect of a fluid on a particle, the force F of the fluid on the particle is increased in the particle discrete element equationf；
S1.4: calculating the erosion rate of the pipe wall of the spherical pipeline elbow (1) under the particle erosion by adopting an empirical formula of an Oka erosion model, wherein the erosion rate formula is as follows:
Figure FDA0003290887330000022
wherein R iseThe wall surface wear rate; n is a radical ofpIs the number of colliding particles; m ispIs the particle mass flow rate; c (d)p) Is a particle attribute correlation function; theta is the impingement angle of the particles on the wall surface; f (θ) is a function of impact angle effect on wear; u is the velocity of the particles relative to the wall; b (v) is a function of relative velocity; a. thefaceIs the area of the wall surface;
s2: selecting the eccentricity E of the pipeline:
setting D to be 90mm, D to be 5mm and V to be 25m/s, and analyzing the flow characteristics of particles in the spherical pipeline elbow (1) when E to be 52mm, 63.5mm and 75mm by using computational fluid dynamics software and discrete element software in a coupling mode, wherein when E to be 75mm, the discharge pipeline (3) is tangent to the inner wall of the spherical pipeline elbow (1);
the analysis results show that: a) when E is 52mm, 63.5mm and 75mm, the maximum erosion rate is 3.76, 5.71 and 16.5 respectively, and the unit of the maximum erosion rate is 10-4kg/(m2s); b) when E is 52mm and 63.5mm, the particles enter the spherical pipeline elbow (1) and collide with the flowing particles in the spherical pipeline elbow (1) for buffering, partial energy is lost, and the speed of the particles at the outlet is reduced; c) when E is 52mm, 63.5mm and 75mm, the average total energy of the particles in the spherical pipe elbow (1) is 53, 54 and 62 respectively, and the unit of the average total energy is 10-5J；
S3: selection of particle diameter d:
setting D to be 90mm, E to be 63.5mm and V to be 25m/s, and analyzing the flow characteristics of particles in the spherical pipeline elbow (1) when D to be 4mm, 5mm and 6mm by using computational fluid dynamics software and discrete element software in a coupling mode;
the analysis results show that: a) when d is 4mm, 5mm and 6mm, the maximum erosion rates are 5.88, 5.71 and 6.82 respectively, and the unit of the maximum erosion rate is 10-4kg/(m2s); b) when d is 4mm, 5mm or 6mm, the larger the particle diameter d is, the smaller the velocity of the particles at the outlet of the spherical pipeline elbow (1) is;
s4: selecting the inner diameters D of the feeding pipeline (2) and the discharging pipeline (3):
setting D to be 5mm, E to be 63.5mm and V to be 25m/s, and analyzing the flow characteristics of particles in the spherical pipeline elbow (1) when D to be 80mm, 90mm and 100mm by utilizing the coupling of computational fluid dynamics software and discrete element software;
the analysis results show that: a) when D is 80mm, 90mm and 100mm, the maximum erosion rates are respectively 5.1, 5.71 and 4.67, and the unit of the maximum erosion rate is 10-4kg/(m2s); b) when D is 80mm, 90mm or 100mm, the larger the inner diameters D of the feeding pipeline (2) and the discharging pipeline (3) are, the smaller the speed of the particles at the outlet of the spherical pipeline elbow (1) is; c) when D is 80mm, 90mm and 100mm, the average total energy of the particles in the spherical pipeline elbow (1) is 52, 54 and 30 respectively, and the unit of the average total energy is 10-5J；
S5: selecting the air flow velocity V:
setting D to be 5mm, E to be 63.5mm and D to be 90mm, and analyzing the flow characteristics of particles in the spherical pipeline elbow (1) when V is 20m/s, 25m/s and 30m/s by utilizing the coupling of computational fluid dynamics software and discrete element software;
the analysis results show that: a) when V is 20m/s, 25m/s and 30m/s, the maximum erosion rates are respectively 5.5, 5.71 and 8.0, and the unit of the maximum erosion rate is 10-4kg/(m2s); b) when V is 20m/s, 25m/s and 30m/s, the larger the air flow velocity V is, the larger the velocity of the particles at the outlet of the spherical pipe elbow (1) is; c) when V is 20m/s, 25m/s and 30m/s, the average total energy of the particles in the spherical pipeline elbow (1) is 52, 54 and 98 respectively, and the unit of the average total energy is 10-5J。
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