液气射流泵扩散管内部流动试验研究

采用压力传感器对扩散管壁面压力进行了测量,获得不同工作水压力和不同气液体积流量比时的扩散管增压情况.结果表明:在给定试验尺寸的有机玻璃制作的液气射流泵扩散管中,壁面压力上升的增量范围为2~5 kPa,且存在压力下降然后再上升的现象,因此,对于垂直安装的液气射流泵,需要考虑其尺寸高度产生的静压对扩散管内部流动的影响;扩散管内部流动对液气射流泵的射流混合性能影响较大,其中液气两相混合在喉管内的初始断面位置的变化对扩散管角度的设计有较大影响.采用PIV装置对扩散管内部液相流速分布进行了试验测量,获得2种气液比情况下扩散管轴线速度和断面速度分布,结果表明:轴线速度衰减约20%;扩散管的断面速度分布不均匀,在气液比较小时,出现流动偏向一侧的情况.该扩散管内部流动的研究结果可为液气射流泵应用于曝气、气体吸收等领域提供一定的理论基础.

Experimental study on flow in diffuser of liquid-jet gas pump

The liquid-jet gas pump has found its applications in jet aeration system and gas absorption etc. A study on the two-phase flow in diffuser of the pump is essential for the pump design and application. Thus, the pressure on the diffuser wall of a liquid-jet gas pump(LJGP)was measured by means of pressure sensors and the pressure recovery profile in the diffuser was obtained under various water working pressures and liquid-to-gas volumetric flow rate ratios. The LJGP was installed vertically; its diffuser and throat were made of Plexiglas. The results showed that the wall pressure recovery is in the range of about 2-5 kPa, the pressure profile drops initially then rises along the diffuser wall. Therefore, the effect of static pressure caused by the height of a vertical LJGP on flow in its diffuser needs to be taken into account. According to an analysis of flow in the diffuser, it was shown that the flow pattern has a great influence on its jet mixing characteristics; further the change in the location where the liquid-jet starts to mix with the gas can affect diffusing angle of the diffuser significantly. Particle image velocimetry(PIV)was used to map the liquid velocity in the diffuser, and the axial velocity distributions in cross-sections were obtained at two liquid-to-gas volumetric flow rate ratios. The results illustrated that the axial velocity is reduced by about 20%, and it was not uniform in cross-sections; the flow with high velocity has been deflected to one side wall in the diffuser at a low flow rate ratio.