阻尼网特性数值模拟

依靠经验公式和工程估算等传统方法,无法对阻尼网性能进行精确评估.为确定阻尼网压力损失系数和降湍性能,采用计算流体力学方法,结合适当的边界条件,对阻尼网进行了模拟.使用数值模拟能够得到不同开孔率阻尼网在不同雷诺数、不同入射方向、不同目数的损失系数,与试验结果更为接近,在30°~45°大角度入射时得到的损失系数更为精确;在入射气流与阻尼网平面呈一定夹角时,阻尼网后的气流压力和速度呈现脉动趋势,传播距离大约为100d;在雷诺数小于40时流动保持层流状态,扰动传播距离为50d,此时降湍效果最好,随雷诺数增加,扰动传播距离增加至400d;在流动未失稳时,开孔率越低,降湍效果越明显,开孔率低于0.5时流动容易失稳;开孔率保持不变,随目数增加阻尼网损失系数增加明显,降湍能力提升.因此可以根据数值模拟结果选择阻尼网的最优参数.

Numerical investigation about field characteristics of screen

There is no reasonable path to evaluate screen performance accurately based on conventional method, such as the experiential formula and engineering correlations technology. Computational fluid dynamics (CFD) with proper boundary conditions was used to find screen performance of different parameters including total pressure loss coefficient and control ability of turbulence intensity. Total pressure loss coefficient of the screen was obtained precisely using CFD with different open area ratio, Renault number, incidence angle, wires per inch, etc., especially, incidence angle equal to 30°-45°. Pressure and velocity after screen was pulsant when air flowed into the screen at certain incidence angle, and the disturbance would become weak after about 100d. The flow regime around the screen kept laminar when Re less than 40, the distance of disturbance about 50d, and that turbulence intensity was reduced on a large scale. With the increase of Re, the distance of disturbance increased to about 400d, the reduce factor of turbulence intensity became smaller than laminar regime significantly. Smaller is the open area ratio of screen before flow regime changed to instability state, bigger is reduce factor of turbulence intensity. Based on the details of numerical results, the instability most likely appears when openning to sectional area ratio less than 0.5. Total pressure loss coefficient and reduce factor of turbulence intensity increases at distinct rate with increase of wires per inch when open area ratio keeps constant. It is concluded that the optimal parameters of the screen can be obtained based on numerical results.