旋风分离器有无灰斗对气相流场动态特性的影响

旋风分离器底端的排尘口依据气固分离工艺的要求分别采用有灰斗或无灰斗结构。但灰斗是否存在对旋风分离器内部流场影响的研究尚显不足。为此,采用热线风速仪对排尘口有灰斗和无灰斗的旋风分离器气相流场的切向速度进行了测量。结果表明旋风分离器内旋转流具有较强的不稳定性,表现为瞬时切向的速度低频高幅值波动变化。灰斗的存在进一步导致了排尘口附近瞬时切向速度的强烈波动。通过对瞬时切向速度的频谱分析表明,有灰斗结构的旋风分离器瞬时切向速度有2个主频,分别是存在于整个空间的全空间主频和出现在锥体下端排尘口附近区域的局部主频。无灰斗结构的旋风分离器仅有1个全空间主频。全空间主频是气体旋流中心围绕旋风分离器几何中心摆动造成的,而局部主频是灰斗气体回流造成的。灰斗气体回流主频与全空间旋转流摆动的主频叠加形成了锥体下端排尘口附近区域瞬时切向速度的2个主频。

Effect of ashless separator on dynamic characteristics of gas phase flow field in cyclone separator

The dust exhaust port at the bottom end of the cyclone separator adopts an ash or ashless bucket structure according to the requirements of the gas-solid separation process. The existence of the hopper has an important influence on the flow field inside the cyclone separator, and then the separating performance. But the research of this aspect is few. Therefore, the tangential velocity of gas flow field in the cyclone separator with and without hopper was measured by using hot wire anemometry (HWA). The results show that the swirling flow in the cyclone is highly instability, and the real tangential velocity fluctuates with low frequency and high amplitude. Further, the existence of hopper leads to strong instability of swirling flow field near the dust outlet, which is characterized by intense fluctuation of real tangential velocity. Fast Fourier transform analysis of measured data shows that the real tangential velocity of cyclone separator with hopper has two dominant frequencies, one exists in the whole space and another one presents in the local area near the dust outlet. However there is only one dominant frequency in the whole space of the cyclone without hopper. The dominant frequency of the whole space is caused by the swing of the swirling flow center around the geometric center, while the local dominant frequency is caused by the backflow from the hopper. So, the swing of the swirling flow from the hopper is superimposed on the swing of the swirling flow in the separation space, which forms two dominant frequencies near the dust outlet region.