多翼离心风机叶轮内油性粒子沉积特性的数值研究

Numerical Study on Deposition Characteristics of Soot Particles in Impeller of a Multi-Blade Centrifugal Fan

为了揭示多翼离心风机内部油性粒子沉积分布规律,减少风机内粒子沉积,采用Fluent离散相模型描述粒子运动,同时结合临界速度模型和用户自定义函数(UDF)建模油性粒子在壁面上的沉积,模拟研究了多翼离心风机内油性粒子的运动轨迹和沉积特性,并探究了颗粒直径对沉积分布的影响。结果表明:油性粒子沉积主要分布在叶片压力面,且靠近出口尾缘段尤为严重;由于进气条件不稳定,整机下内部流场更为紊乱,沉积情况也更为严重;大直径粒子受惯性力主导更容易沉积在叶片表面。针对油性粒子沉积分布规律及成因,提出了切割叶片减小叶片出口安装角从而减少叶轮内油性粒子沉积的方法。对于切割后的叶片,叶轮出口处流动分离区域减小,叶片尾缘段涡量减小,通过数值模拟和实验研究发现,叶轮内油性粒子沉积率分别下降了30.75%和30.66%,两者吻合良好,证实了提出的减小叶轮油性粒子沉积方法的有效性。

To reveal the distribution of soot particle deposition in a multi-blade centrifugal fan and mitigate such deposition,numerical simulations are conducted to investigate the trajectories and deposition characteristics of soot particles within a multi-blade centrifugal fan.The study utilizes the Fluent discrete phase model to describe particle motion,while employing the critical velocity model and the user-defined functions(UDF)to model the particle deposition on walls.In addition,the study examines the particle diameter on deposition distribution.Findings indicate that soot particles mainly deposit on the blade pressure surface,with notable accumulation near the trailing edge close to the outlet.When the complete machine is involved,the flow field within the fan becomes more turbulent due to unstable inflow conditions,thereby leading to escalating deposition levels.It is found that particles with larger diameters exhibit a higher tendency to deposit on blade surfaces owing to the dominant inertial forces.In light of deposition distributions and their causal factors,an optimization strategy is proposed to reduce the deposition on blade surfaces by cutting blades and consequently reducing the outlet installation angle.In terms of the modified blades,flow separation near the impeller outlet decreases,leading to decreased vorticity around the trailing edge of blades.Comparing the original and modified blades,numerical simulation results show a 30.75%decrease in deposition rate,while experimental outcomes demonstrate a 30.66%reduction.The close agreement underscores the effectiveness of the proposed method in mitigating the deposition of soot particles.