滚筒干燥器中杆状颗粒混合特性的三维数值模拟

Three dimensional numerical simulation of mixing characteristics of slender particles in rotary dryer

为研究杆状颗粒在滚筒干燥器中的混合运动,建立了杆状颗粒运动特性的三维数值实验平台.采用离散元法直接跟踪滚筒中的每一个颗粒,对杆状颗粒在滚筒干燥器中碰撞、摩擦的混合运动过程进行数值模拟,并把杆状颗粒和球形颗粒在滚筒中的混合特性进行对比.结果表明:随着转速的增加,颗粒混合均匀的速度加快;滚筒内杆状颗粒和球形颗粒均在近壁区域混合程度好;杆状颗粒混合达到均匀的速度较球形颗粒快;杆状颗粒整体混合均匀程度优于球形颗粒.模拟结果还表明,杆状颗粒的混合特性与球状颗粒的混合特性存在很大区别,在以往数值模拟中将杆状颗粒假设成球形颗粒存在较大误差,对杆状颗粒所建立的模型能更好地符合杆状颗粒的运动规律.

In order to investigate the mixing characteristics of slender particles in a rotary dryer, a three dimensional numerical experiment platform was established for the kinetic characteristics of slender particles. The discrete element model was adopted to track the movement of each slender particle, the whole mixing process of particle collision and friction in the rotary dryer was numerically simulated, and the mixing characteristic of slender particles is compared with spherical particles. The research results show that with the increase of rotating speed, the mixing speed to gain uniformity becomes faster; the uniformity grade is better at outer area than the inner area for both kinds of particles; while the mixing speed of slender particles to gain uniformity is faster than the spherical ones, the whole uniformity grade of slender particles is better than that of spherical particles. The results also indicate that there is big difference of mixing characteristics between slender particles and round particles, previous assumption of taking slender particles as spherical ones may lead to serious errors. The model established for slender particles can suit the motion law well.