【摘要】 分级机流场特性是影响分级机分级性能的重要因素，其相关研究受到国内外大量学者的关注。以涡轮空气分级机为研究对象，通过在二级进风口上侧增设收缩角，改变分级机流场结构，采用数值模拟技术，分析分级机流场的变化，探究收缩角对分级机分级性能的影响。结果表明：随分级机二级进风口上侧收缩角增大，流场PVC现象有所改善，分级机轴线附近气流切向速度有明显提高，分级机内部颗粒停留时间明显缩短，细粉出口逃逸颗粒的粒径范围呈现先缩小后增大趋势。当收缩角为5°和7°时，相比于其他角度，细粉出口超75%颗粒粒径小于4μm,均对2～3μm颗粒敏感性最高，2～3μm颗粒数占出口总颗粒数的21%,1～4μm颗粒数占出口总颗粒数的58.4%,相比无收缩角分级机，1～4μm颗粒数的占比提高45.5%,对小粒径颗粒分级效果较好。更多还原

【Abstract】 The flow-field characteristics is an important factor that affects the classifier’s classification performance, and the related research attracts the attention of many scholars both at home and abroad. In this article, with the focus on the turbine air classifier, a contraction angle is added on the upper side of the secondary air inlet, in order to change the classifier’s flow-field structure. The technologies of numerical simulation are used to analyze the changes of the classifier’s flow field and explore the influence of the contraction angle on its classification performance. The results show that with the ever-growing contraction angle on the upper side of the secondary air inlet, the flow-field PVC improves; the tangential velocity of the air flow near the axis of the classifier significantly increases; the residence time of the particles in the classifier is significantly shortened; the particle size range of the escaping particles at the fine powder outlet is narrowed and then expanded. When the contraction angle is 5° and 7°, compared with other angles, more than 75% of the particles at the fine powder outlet have the particle size of less than 4 μm, all of which are most sensitive to the 2～3 μm particles. 2～3 μm particles account for 21% of the total number of particles at the outlet, and 1～4 μm particles account for 58.4% of the total number of particles at the outlet. Compared with the classifier without any contraction angle, the number of 1～4 μm particles increases by 45.5%, thus ensuring better classification of small-sized particles.更多还原