﻿ 撞击流颗粒包覆过程的流体动力学行为 The Behavior of Fluid Dynamics during Particles Coating in Impinging Stream

International Journal of Fluid Dynamics
Vol.03 No.03(2015), Article ID:16035,9 pages
10.12677/IJFD.2015.33003

The Behavior of Fluid Dynamics during Particles Coating in Impinging Stream

Wei Wei, Fengxia Liu, Xiaofei Xu, Xiaojuan Wang, Yin Wang, Zhiyi Li, Zhijun Liu

Design Institute of Fluid and Powder Engineering Research, Dalian University of Technology, Dalian Liaoning

Received: Aug. 22th, 2015; accepted: Sep. 8th, 2015; published: Sep. 15th, 2015

ABSTRACT

This work establishes the motion model for the particles in the gas-solid impact flow, to study the strengthening mechanism of the flow transfer in the impinging fluid. The particles’ residence time and particles through length are simulated. Three conditions including the condition of single particle from single nozzle (SP), particles group from single nozzle (SPG) and particles group from double nozzles (DPG) are chosen in this study. Also, the pressure and the temperature before expansion as well as the distance between two opposite nozzles exits are defined as the different initial conditions. The changing tendencies for the particles’ residence time and particle through length of the particle are obtained. In addition, the Particle Image Velocimetry is used to describe the characteristic of the supercritical gas-solid impact flow.

Keywords:Impinging Stream, Residence Time, Through Length, Velocity Field Measurement

1. 引言

2. 撞击过程动力学模型

2.1. 模型假设与控制方程

1) 模型为稳态流动；

2) 气–固两相流中微粒粒径均一且为球形，粒径为纳米至微米级[22] [23] ，取其粒径为1 μm；

3) 由于模拟过程中，流场速度较大，颗粒不考虑重力等其它外力的作用；

4) 流场进口处流体处于完全发展状态，气–固两相流体以静压推动。

(1)

(2)

(3)

2.2. 物理模型

2.3. 模型求解

Figure 1. Geometric model

Figure 2. Grid generation

Table 1. The size of geometric model

3. 模拟结果与讨论

3.1. 颗粒的停留时间与渗入距离

Table 2. The initial condition of simulation

Figure 3. Change of host particle residence time with p

Figure 4. Change of host particle through length with p

Figure 5. Change of host particle residence time with T

Figure 6. Change of host particle through length with T

Figure 7. Change of host particle residence time with L

Figure 8. Change of host particle through length with L

3.2. 颗粒的运动状态

4. 流场测试

4.1. 实验装置

4.2. 速度分布

(a) p = 0.6 MPa, T = 363 K, L = 50 mm, SP
(b) p = 0.6 MPa, T = 403 K, L = 50 mm, SP
(c) p = 0.7 MPa, T = 363 K, L = 50 mm, SP
(d) p = 0.3 MPa, T = 363 K, L = 50 mm, SP
(e) p = 0.3 Mpa, T = 363 K, L = 90 mm, SP

Figure 9. Host particle motion trajectories profile

1-CO2气瓶；2-隔膜压缩机；3，4-阀门；5-加热器；6-萃取釜；7-温度传感器；8-压力表；9-加热器；10-对置喷嘴

Figure 10. Flow chart of supercritical coating process

Figure 11. Profile of axial velocity at different flow pattern

5. 结论

1) 颗粒的停留时间与渗入距离随膨胀前压力呈周期性变化，几乎不受膨胀前温度的影响。喷嘴出口间距对颗粒的停留时间与渗入距离有一定的影响，颗粒的停留时间随喷嘴出口间距的增大而增大，渗入距离随喷嘴出口间距的增大而减小。

2) 通过对单喷嘴喷射单一颗粒(SP)、单喷嘴喷射颗粒群(SPG)以及双喷嘴喷射颗粒群(DPG)三种流动状态的对比研究发现，DPG流动状态可以增大颗粒在流场中的停留时间，与SP流动状态相比，颗粒的停留时间增大了55%~67%，与SPG流动状态相比增大了43%~54%。

3) 通过PIV测试得出，超临界流体气–固两相撞击流流场呈对称式分布，DPG流动状态下流场的湍动性比SPG流动状态下的大，最大轴向速度比SPG流动状态下的高27.3%。同时，验证了模拟过程的正确性。

The Behavior of Fluid Dynamics during Particles Coating in Impinging Stream[J]. 流体动力学, 2015, 03(03): 19-27. http://dx.doi.org/10.12677/IJFD.2015.33003

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