超临界机组跨临界区域Fe系沉积动力学过程研究

Study on Dynamics of Fe Sedimentation in Transcritical Region of Supercritical Units

为得到超临界机组锅炉受热面中Fe系颗粒在跨临界区域的沉积分布动力学过程,建立了水平圆管的二维模型,通过改变入口温度、入口流速、壁面加热功率、颗粒受力和颗粒粒径来进行颗粒沉积分布情况研究。结果表明:颗粒粒径是影响颗粒沉积动力学过程的主要因素,对于粒径大于1.0μm的颗粒,对颗粒沉积起抑制作用的力由大到小依次是Saffman升力、热泳力、布朗力,但当颗粒粒径小于1.0μm时,对颗粒沉积起抑制作用的力由大到小依次是热泳力、Saffman升力、布朗力;当颗粒粒径为2.0μm时,其在跨临界区域沉积效果最好,且随着入口流速的增加,颗粒的沉积质量浓度峰值逐渐减小,沉积位置向管道出口处移动;随着壁面加热功率的提高,8.0μm颗粒的沉积总量变化不大。

In order to obtain the dynamics of the deposition distribution of Fe particles in the transcritical region in the heating surface of the boiler of the supercritical unit,a two-dimensional model of the horizontal circular tube was established.The distribution of particle deposition was studied by changing the inlet temperature,inlet flow rate,wall heating power,particle force and particle diameter.Results show that particle size is the main factor affecting the kinetic process of particle deposition.For particles with a particle size greater than 1.0μm,the forces that inhibit particle deposition are Saffman lift force,thermophoresis force and Brownian force.While the particle size is less than 1.0μm,the forces that inhibit the particle deposition are thermophoresis force,Saffman lift force and Brownian force in descending order.When the particle size is 2.0μm,it has the best deposition effect in the transcritical region,and with the increase of inlet flow velocity,the peak concentration of particle deposition gradually decreases,and the deposition position moves to the outlet of the pipe.With the increase of wall heating power,the total amount of 8.0μm particles deposited won't change much.