数值模拟滤袋长度对除尘器流场及粉尘沉降的影响

利用数值模拟方法，探究袋式除尘器中圆筒滤袋改为褶皱滤袋后，滤袋长度变化对除尘器内部流场及粉尘在灰斗中沉降的影响。结果表明：圆筒滤袋改为褶皱滤袋可显著降低系统阻力，有利于系统节能；下进风式除尘器箱体中，滤袋越短除尘器内部的气流分布越不均匀，气流易在除尘器箱体空间及灰斗中产生涡旋，除尘器内部远离进风口一侧的滤袋会承担更多风量并受到高速气流冲击；在袋长(L)分别为3、4、5、6 m的除尘器内，粉尘在灰斗中沉降率(η) 为η(L=5 m)>η(L=4 m)>η(L=3 m)＞η(L=6 m)。这表明袋底距入口太近不利于粉尘沉降，粉尘直接运动至滤袋，反而会增加滤袋的过滤负担，故滤袋长度L=5 m时粉尘在灰斗中的沉降率最佳。然而，进一步降低滤袋长度不能提高粉尘的沉降率，滤袋渗透率越大，除尘器内部流场速度分布越均匀，粉尘更易沉降至灰斗。本研究结果可为下进风袋式除尘器的袋长设计提供参考。

Numerical simulation of the influence of filter bag length on bag filter flow field and dust settling

Numerical simulation method was used to analyze the influence of changing filter bag length on internal flow field in the bag filter, and dust settling in the ash hopper after the cylindrical filter bag was changed to the pleated filter bag.The results showed that changing cylindrical filter bag into pleated filter bag could significantly reduce the system pressure drop, which was beneficial to the system energy saving. In the case of down inlet bag filter, the shorter the filter bag was, the more uneven the air flow distribution in the bag filter was, and the air flow was easy to vortex in the bag filters space and ash hopper, and the filter bag on the side of the bag filter far from the air inlet would bear more air flow and be impacted by high-speed air flow. In the bag filters with a length (L) of 3,4,5,6 m,the order of dust settling rate（η） in the ash hoppers was η(L = 5 m) > η(L = 4 m) > η(L = 3 m) > η(L = 6 m), which indicated that the bottom of the bag was too close to the entrance, and it was not conducive to dust settling. When the bag length was at L=5 m, the dust settling rate in the ash hopper was the best, but further reducing bag length could not improve the dust settling rate. The greater the filter bag permeability was, the more uniform the velocity distribution of the flow field in the bag filter was, and the dust was more likely to settlle to the ash hopper. The research results can provide guidance for bag length design of down inlet bag filter.