立式水力碎浆机内部浆料流场数值模拟及其新型槽体结构的研究(二)

Numerical Simulation of Fiber Slurry Flow Field inside the Vertical Hydraulic Pulper and Research on New Type of Its Tank Structure(Ⅱ)

中文关键词:  鼓槽体螺旋返流板立式水力碎浆机  浆料流场分布  FLUENT  数值模拟

Key Words:drum-shaped vertical hydraulic pulper with spiral baffles  distribution of fiber slurry flow  fluent  numerical simulation

中文摘要:

      基于国内外已有的相关专利和应用的立式水力碎浆机结构，提出了一种高效、节能和运行平衡稳定的新型鼓槽体结构；然后,运用FLUENT软件对新型鼓槽体内部浆浓为5%的浆料流场进行数值模拟,以得到其内部浆料流场的压力、流速和湍流强度的分布情况,并与O形和D形槽体进行分析对比；最后，通过小型碎浆装置碎浆实验验证数值模拟结果。实验结果表明,新型鼓槽体螺旋返流板立式水力碎浆机的结构特征为槽体采用鼓形结构,并且在槽壁上焊有反流向、45°螺旋线、间断排布、带凹槽的梯形截面返流板；椭球弧形收口和返流板的合力作用可将浆料同时向槽体中心和槽底转子区域推送,同时返流板附近湍流强度平均增强100%,有效提高了碎浆效率；倒锥体部壁面处的浆料速度为5 m/s,能够有效降低因径向撞击壁面造成的能量损失；碎浆过程中,鼓槽体的振幅有效值远低于具有不对称结构的D形槽体,保证运行时的安全性和稳定性。

Abstract:

      Based on the various types of the structure of vertical hydraulic pulpers and qualitative and quantitative theoretical analysis of their advantages and disadvantages, a new high-efficient, energy-saving and stable and balanced runnining type of the tank structure was put forward. Then, the 5% concentration of pulp suspension flow fields inside the new-type tank was simulated with FLUENT software, and the distribution of pressure, velocity and turbulence intensity were obtained and analyzed by comparing with the O-shaped and D-shaped tanks. At last, a pulping experiment was carried out using laboratory-sized pulpers to verify the simulation result. The results showed that the new-type tank was drum-shaped and with spiral baffles on the wall, and the baffles were in the opposite direction of pulp flow, 45° spiral, interval and with a trapezoid vertical section and grooves on its top; its ellipsoidal upper structure and baffles push pulp flow to the rotor at the center and bottom of the tank, moreover, the turbulence intensity near the baffles was 100% higher than the areas around it, so pulping efficiency was greatly increased, which was verified in the later pulping experiment; and the velocity of pulp at the wall of the inverted cone was 5 m/s, which indicated that energy consumption of the new-type tank caused by pulp radially hitting the wall could be obviously decreased. The RMS of the drum-shaped tank during pulping activity was much lower than that of the D-shaped tank, which meant the flow field inside the drum-shaped tank was symmetrical and balanced.