海水淡化双级真空引射器的射流和混合特性研究

Study on Jet and Mixing Characteristics of a Two-Stage Vacuum Ejector for Desalination

引射器是实现热法海水淡化系统高效节能的重要装置,该文通过三维数值模拟方法研究了双级引射器内部流动和传输特性,分析了引射和工作流体的混合与扩散过程,探讨了降低能耗的方法。研究结果表明,喷射器内速度最大值均在轴线处,流体在喷嘴与混合室内流线均匀,而在吸入室内产生一个或多个涡流。不同引射流体速度下,其混动迹线为不对称分布,随着引射流体速度的增大,引射流体入口处负压先增加后减小,漩涡量减少且漩涡变小。因此,为改善引射器运行效率,可适当提高引射流体速度。随着偏离喷嘴中心距离的增大,湍动耗散率明显增大,而湍动能略微增大,漩涡消散加快。

Ejector is an important device to improve the efficiency of thermal seawater desalination system. In this work, the internal flow and transport characteristics of a two-stage ejector are investigated via a three-dimensional numerical simulation. The mixing and diffusion processes of ejecting and working fluids are also analyzed to identify the factors related to energy consumption. The simulation results showed that,the maximum velocity of the ejector occurs in the axis direction and the streamline distribution in the nozzle and mixing chamber is uniform. However, one or multiple vortices are generated in the suction chamber, which causes the uneven distribution of streamline. The negative pressure at the entrance of the suction chamber increases firstly, and then decreases with the increasing velocity. The amount of vortex decreases with increasing velocity, which helps to improve the efficiency of ejector. Vortex dissipates faster with increased distance from the central line and the turbulent dissipation increases significantly, which results in a rapid dissipation of vortex.