沥青搅拌设备蜗壳除尘器流场仿真与试验

Flow Field Simulation and Experimental Study on Volute Separators for Asphalt Mixing Plants

为研究导流板位置对蜗壳除尘器内流场和粉尘粒径的影响,以指导回收粉在沥青搅拌设备中的实际使用,在导流板3种不同位置工况下,对蜗壳除尘器内部气相和气固两相流动状态进行了数值模拟和试验验证。数值模拟基于FLUENT软件,其中气相流场模拟选用雷诺应力模型,气固两相流场模拟选择相间耦合的随机轨道模型模拟粉尘的运动轨迹,分别追踪了16 400个粒径在50~1 000μm的粉尘,计算了除尘效率。在沥青搅拌设备工地分别采集了导流板3种位置工况下的回收粉,结合筛分和电镜扫描试验,分析粉尘粒径分布,并对数值模拟结果的吻合性进行验证。结果表明:导流板处于O位时,除尘器内部气流的径向速度、轴向速度和静压分布轴对称性较W位和M位好,可有效抑制非对称性扰流及夹带涡流,并削弱涡核摆动现象;导流板处于不同位置时,通过与粉尘颗粒的碰撞反弹来改变粉尘的运动轨迹,进而影响除尘器对不同粒径粉尘的除尘效率,且当导流板处于O位时更有利于对粒径大于100μm的粉尘的回收。导流板处于O位时,试验测量的粉尘平均粒径为117.6μm,筛底平均粒径为49.9μm,均大于W位和M位的粒径,且与数值模拟的结论相吻合。沥青搅拌设备在实际生产过程中,应优先选择导流板O位布置,并根据回收粉粒径的需要进行实时调整。

To study the influence of the deflector position on the flow field and particle diameter for volute separators and provide guidance on the practical use of recycled dust in asphalt mixing plants,numerical simulations and verification experiments were conducted for the flow field of gas and gas-solid phases at three deflector positions.By using FLUENT software as the platform,a Reynolds stress model and the coupled interphase discrete particles model were used to simulate the flow fields of the gas and gas-solid phases,respectively.In the gas-solid phase simulation,the trajectories of 16 400 dust particles with diameters of 50 to 1 000μm were tracked,and the removal efficiency of dust was calculated.The recycled dust was collected at three deflector positions in the asphalt mixing plant site.The size distribution of dust particles was evaluated via sieving and electron microscope scanning;the results were used to verify theconclusions of the numerical simulation.The research findings are as follows：when the deflector is at the O position,the axial symmetry for radial velocity,axial velocity,and static pressure are better than those for the W and M positions.Additionally,the asymmetrical turbulence and entrainment swirl can be effectively restrained,and the swinging phenomenon of vortex core can be weakened.Furthermore,collisions and rebounding may cause the trajectory of dust particles to differ according to the position of the deflector.This process can affect the removal efficiency of different sized dust particles.When the deflector is at the O position,the dust with the diameter larger than 100μm can be more effectively collected.In addition,under the O position condition,the average particle diameter of the recycled dust is 117.6μm and that of the dust in the last sieve is 49.9μm.These two diameters are greater than those observed under the W and M position conditions.The experimental results are consistent with those of the numerical simulations.In the actual production process of asphalt mixing plants,the deflector of the volute separators should initially be placed at the O position.Additionally,the deflector position should be adjusted according to the actual requirements related to the size of the recycled dust particles.