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Of the relative end-to-end ratio on the main performance of cyclone dust collector-Botou Kangyue Environmental Protection

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Effect of relative end-to-end ratio on main performance of cyclone dust collector

泊头市康越环保 发布时间: 2017/2/3 14:10:58 Source : Kangyue Environmental Protection , Botou Release time: 2017/2/3 14:10:58
In order to improve the separation efficiency of the cyclone dust collector, a three-dimensional cyclone dust collector model was constructed using the RSM turbulence model, and the influence of the relative end face ratio on the main performance of the cyclone dust collector was studied. Numerical simulation results show that as the relative end-face ratio decreases, the total pressure and tangential velocity decrease, and the residence time of the particles is shortened, thereby improving the separation efficiency and providing a reference for the structural optimization design of the cyclone dust collector.

SM 湍流模型构建三维旋风除尘器模型,研究了相对端面比对旋风除尘器主要性能的影响 Abstract : In order to improve the separation efficiency of the cyclone dust collector , a three-dimensional cyclone dust collector model was constructed using the RS SM turbulence model , and the influence of the relative end face ratio on the main performance of the cyclone dust collector was studied. Numerical simulation results show that as the relative end-face ratio decreases, the total pressure and tangential velocity decrease, and the residence time of the particles is shortened, thereby improving the separation efficiency and providing a reference for the structural optimization design of the cyclone dust collector .

0 Preface:
With the popularization and application of cyclone dust collectors, people's performance has been [1]. Over the past ten years, foreign scholars have begun to study the structure and performance of the flow field from an overall three-dimensional perspective. Karagoz [2] designed the cyclone dust collector by increasing the length of the vortex, and found that [3] the separation efficiency was improved compared with the traditional cyclone dust collector. Liu Xuan et al. Proposed that increasing the insertion depth of the exhaust pipe will increase the [4] passage pressure loss of the cyclone dust collector, and the dust removal efficiency will be improved accordingly. Gao et al. After changing the height and diameter of the central pipe, analyzed the influence of the central pipe on the flow field of the cyclone dust collector, and obtained the optimal central pipe size. In fact, when the dust concentration is low and the fine particles are captured, the dust removal efficiency of the cyclone dust collector is not high. How to effectively improve the performance of the cyclone dust collector has become a difficult point of current innovation and breakthrough.
In this paper, a numerical simulation is performed on the cyclone dust collector with the help of computational fluid software CFD, and a three-dimensional cyclone dust collector model is established by using the RSM turbulence model. The separation law varies with the ratio of the opposite end face.

1. Theoretical model:
1.1 Gas flow field:
SM 型来模拟旋风除尘器的气相流场,其控制方程主要 Because the cyclone dust collector has a strong three-dimensional strong swirl and has anisotropic turbulence characteristics, the RS SM model is selected here to simulate the gas phase flow field of the cyclone dust collector.

5 [ 5 ]

Is the transport equation, which can be written as

- -

ρ u' i u' j ( ρ u ' i u' j )

1 ( 1 )

ij = D ij P ij + ij ε ij + C ij = D ij - P ij + ij - ε ij

t t

ρ 为空气的密度, kg /m 3 ; u' 下注 i j k 表示空 In the formula, ρ is the density of air, kg / m 3 ; u ' bets i , j and k are empty

- -

u' i u' j 为颗粒在 x 方向的速度平均值和脉动值, m /s ; C ij D ij 分别为对流项 湍流扩散项; P ij 为剪应力产生项; ij 为压力应变项; ε ij 为粘性耗散项 U ' i and u' j are the average velocity and pulsation of the particle in the x direction, m / s ; C ij and D ij are the convection and turbulent diffusion terms , respectively ; P ij is the shear stress generation term; ij Is the pressure strain term; ε ij is the viscous dissipation term . 1 . 颗粒动力场与颗粒本身的惯性力相比,颗粒在除尘器流场中运动时所受的浮力、压力梯度力、附加质量力以及重力等在量级上均很小,可忽略不计。 2Compared with the inertia force of the particle itself, the particle's buoyancy, pressure gradient force, additional mass force, and gravity are small in magnitude when they move in the flow field of the dust collector, which can be ignored. Therefore, the equation of motion of particles can be directly derived from Newton's law:

p m p

p du p

C + F D = F C + F D

2 ( 2 )

dt

j

j

m p u p 分别为颗粒质量和运动速度, F C j 为颗粒之间 颗粒与壁面之间碰撞产生的力, F D j 为流 Where m p and u p are the mass and velocity of the particles, respectively, F C j is the force generated by the collision between particles and between the particles and the wall, and F D j is the flow

The drag force of body viscosity on particles can be written as

2 d 2

D F D

=

p πρ p

D u g u p | u g u p | C D ( u g - u p ) | u g - u p |

3 ( 3 )

8

j

C D 为气体 颗粒阻力系数, d p 为颗粒直径, Where C D is the gas - particle resistance coefficient, d p is the particle diameter,

g u p 分别为气体和颗粒的速度 u g and u p are the velocity of the gas and the particles, respectively .

2

Numerical models and calculations

2 1

Geometric model

As shown,

1 The three-dimensional model of the cyclone dust collector used in this paper is shown in Figure 1.

H = 760 mm ,直径 D 0 Dust collector height H = 760 mm , diameter D 0    ,其中矩 = 190 mm where the moment

a = 95 mm ,宽度 The shaped part is the air inlet duct. The height of the air inlet duct is a = 95 mm and the width is

; 大的圆柱部分为主筒体,高度 h = 285 b = 38 mm ; the large cylindrical part is the main cylinder, height h = 285

,下部梯形圆台部分为锥形灰斗,直径 D c = 72 mm , the lower trapezoidal round table part is a conical ash bucket with a diameter D c = 72 . 5

; 上部的小圆柱为出气管道,直径 D mm ; the upper small cylinder is the outlet pipe, diameter D

,其 = 64 mm

e

= 95 mm ,漏在外边的 The height R = 95 mm deep into the inside of the main cylinder , leaking to the outside

L = 55 mm Height L = 55 mm .

Figure 1 Three-dimensional model of cyclone dust collector
figure 1 Three-dimensional model of cyclone dust collector

2 2

Meshing

3 Use hexahedron for meshing, select 3 respectively

Grid

1 μ m To calculate 1 μm

1 Particle separation efficiency, calculation results are shown in Table 1.

As shown . It can be seen that as the number of grids increases, the separation efficiency is relatively

The error gradually decreases . 93 For _ calculation accuracy, this article uses 93

个网格单元数进行模拟计算 The number of 216 grid cells was simulated .

1 Table 1

Grid Independence Verification of Cyclone Dust Collector

Grid number

/% Separation efficiency /%

/% Relative error /%

78 765

59 . 88

-

85 941

62 . 12

3 74

93 216

63 . 54

2 28

2 3

Boundary conditions

其他壁面分别采 The outlet is a mobile outlet, and the solid wall surface and other wall surfaces are separately collected.

Use non-slip wall and reflection boundary, see the table for other boundary conditions

2 .

2 边界条件设置 Table 2 Boundary condition settings

Boundary conditions

Set up

Entrance

Speed entry

Ash outlet

Capture interface

exhaust vent

Escape boundary

3. Calculation results and analysis:
The ratio of the opposite end face is the ratio of the cross-sectional area of the inlet of the cyclone to the cross-sectional area of the cylinder, and it is recorded as K. The height a of the rectangular inlet pipe and the diameter Do of the cylinder are two important factors affecting the dust removal efficiency of the cyclone dust collector. In view of this, this paper examines the effect of different relative end-face ratios on the performance of cyclone dust collectors by varying the inlet height a and the diameter of the barrel Do.
3.1. Reliability verification:
This paper simulates the change of the tangential velocity of the cyclone dust collector structure at the position of z = 150 mm on the x = 0 section along the radial direction (the direction of the cylinder centerline pointing to the cylinder wall), and the experimental data 6 in [] For comparison, the results are shown in Figure 2. It can be seen that the simulation results are in good agreement with the experimental data in the literature [], thus verifying the reliability of the theories and numerical models in this paper.
Fig. 2 Variation curve of tangential velocity in the radial direction
2 Figure 2 Change curve of tangential velocity in radial direction
3.2. The influence of relative end face ratio on dust removal performance:
At different relative end-face ratios, the particle trajectory of the cyclone dust collector is shown in Fig. 3, from left to right, K = 5, K = 7 and K = 9. It can be intuitively seen that with the decrease of the relative end face ratio, the number of rotations of the particles in the dust collector decreases, that is, the time that they stay in the dust collector gradually decreases, which makes the particles enter the ash discharge port earlier and is easier Arrested.
Figure 3 Particle trajectory of cyclone dust collector with different relative end-face ratios
3 不同相对端面比下旋风除尘器颗粒运动轨迹 Figure 3 Particle trajectory of cyclone dust collector with different relative end-face ratios
The cutting speed is the main component speed of the magnitude _, _ in the dust collector, and it is also one of the main factors affecting particle capture. The curve of the internal cutting speed of the cyclone dust collector with different relative end-face ratios along the radial direction is shown in Figure 4. It can be seen from Fig. 4 that the tangent speed increases sharply with the increase of the radius, and then decreases gradually after reaching the peak value. The curve has a symmetrical “hump” distribution. It increases and decreases, while the tangential velocity increases with the increase of the radial radius in the updraft. In addition, as the ratio of the opposite end faces increases, the internal cutting speed of the cyclone dust collector gradually increases.
Fig. 4 Variation curve of internal cutting speed at different relative end-face ratios
4 Figure 4 Change curve of internal cutting speed under different relative end-face ratios
The size and distribution of the pressure field directly affect the dust removal efficiency of the cyclone dust collector, and the total pressure is an important indicator that reflects the pressure field distribution of the cyclone dust collector . 5 给出了不同相对端面比下的总压曲线,分析后不难得知: 旋风除尘器内的总压沿半径方向呈非线性增大趋势,_后逐步趋于平缓,曲线的斜率先增大后减小,这是因为在上旋和下旋气流的交界处压力变化明显的缘故 Figure 5 shows the total pressure curves at different relative end-face ratios. After analysis, it is not difficult to know that the total pressure in the cyclone dust collector increases non-linearly in the radial direction, and then gradually flattens, and the slope of the curve increases first. It decreases because the pressure changes significantly at the interface of the upswing and downswing airflow . In addition, as the ratio of the opposite end faces decreases, the total pressure inside the cyclone dust collector continues to decrease .
Fig. 5 Variation of total pressure along the radial direction at different relative end-face ratios
5 Figure 5 Variation curve of total pressure along radial direction under different relative end face ratios
16 m /s 时,旋风除尘器分离效率随相对端面比的变化曲线如图 6 所示 When the inlet wind speed is 16 m / s , the curve of the separation efficiency of the cyclone dust collector with the relative end face ratio is shown in Figure 6 . K It can be found that with the gradual increase of the ratio of the opposite end faces, the separation efficiency increases first and then decreases.   附近达到_,这是因为相对端面比主要由入口高度及筒体直径两参数共同决定 = _ Is reached near 5 because the relative end face ratio is mainly determined by the two parameters of inlet height and cylinder diameter .
Figure 6 Curve of separation efficiency as a function of relative end-face ratio
6 Figure 6 Curve of separation efficiency with relative end-face ratio
结论: 4. Conclusion:

1 ) 旋风除尘器内部总压沿半径方向逐渐增大,其变化趋势大于沿轴向的变化,随着相对端面比 ( 1 ) The total internal pressure of the cyclone gradually increases in the radial direction, and its change tendency is greater than the change in the axial direction.

 

As the pressure decreases, the total pressure decreases continuously .

 

2 ) 旋风除尘器内部切速度基本呈轴对称分布,且随着相对端面比的增大,切速度逐渐增大 ( 2 ) The cutting speed inside the cyclone is basically distributed symmetrically, and the cutting speed gradually increases with the increase of the ratio of the opposite end surface .

 

3 ) 随着相对端面比逐渐减少,颗粒在旋风除尘器中旋转圈数逐渐减少,逗留时间逐渐减少,颗粒 ( 3 ) As the relative end-face ratio gradually decreases, the number of rotations of the particles in the cyclone gradually decreases, the residence time gradually decreases, and the particles

More vulnerable to capture .

 

4 ) 随着相对端面比的增大,分离效率先急剧增大,而后逐渐减小,在相对端面比为 5 左右时分离效率达到_,这对旋风除尘器的设计制造具有重要的指导意义 ( 4 ) With the increase of the relative end face ratio, the separation efficiency increases sharply, and then gradually decreases. When the relative end face ratio is about 5 , the separation efficiency reaches _, which has important guiding significance for the design and manufacture of cyclone dust collectors . .

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