气液比对压裂返排液旋流除砂器性能的影响

水力旋流器已被应用于压裂返排液除砂,为了提高其分离性能,基于Fluent软件模拟和实验,研究了不同入口气液比(GLR)下水力旋流器的空气柱直径、压力与速度分布及分离效率,总结了入口GLR对水力旋流器分离性能的影响规律,并确定了最佳入口GLR范围。研究结果表明:①物料不含气体时,底流口与溢流口负压区将外界气体吸入内流场形成空气柱,当物料中含有气体时,空气柱中绝大部分气体来自溢流口与底流口,并且最终通过溢流口排出;②随着气液比升高,壁面处压力、底流压差及溢流压差均呈现非线性增长的趋势;③随着气液比升高,切向速度增大,却减小了较小气液比(10%～20%)下的组合涡流场指数;④随着气液比升高,轴向速度不断增大,然而过高的气液比(GLR 40%)却增加了流场的不稳定性;⑤气液比的升高提高了水力旋流器的除砂效率并减小了切割粒径,当GLR 30%时组合涡流场指数较小且分离效率较低,GLR 40%时能量损耗较大,确定出最佳GLR区间介于30%～40%。结论认为,该研究成果可以为水力旋流器的优化设计提供参考。

Effect of gas–liquid ratio on the performance of hydrocyclones for desanding flowback fracturing fluids

Hydrocyclones have been used for desanding flowback fracturing fluids. In order to improve its separation performance, this paper investigated air core diameter, pressure and velocity distribution and separation efficiency of a hydrocyclone at different inlet gas–liquid ratios (GLR) by means of the software Fluent and experiments. Then, the influential laws of inlet GLR on the separation performance of a hydrocyclone were summarized and the range of optimal GLR was determined. And the following research results were obtained. First, when there is no air in the material, the external air is sucked into the internal flow field through the negative pressure zones of underflow port and overflow port to form an air core. When there is some air in the material, the air in the air core is mainly from the underflow port and the overflow port and ultimately flows out through the overflow port. Second, as the GLR increases, the pressure at the wall surface, the underflow pressure difference and the overflow pressure difference present the trend of nonlinear growth. Third, with the increase of GLR, the tangential velocity increases, but the Rankine vortex index declines at lower GLR (10–20%). Fourth, the axial velocity increases continuously with the increase of GLR, but the excessive GLR (GLR>40%) increases the instability of the flow field. Fifth, the increase of GLR increases the desanding efficiency of the hydrocyclone and reduces the cut particle size. When GLR is lower than 30%, the Rankine vortex index is small and the separation efficiency is low, and when GLR is higher than 40%, the energy loss is large, so the range of optimal GLR is determined to be 30–40%. In conclusion, the research results can provide a reference for the optimal design of hydrocyclones.