气液两相流在180°弯头上T形管处相分离的实验研究

摘要

利用180°弯头上的T形管考察气液两相流的相分离行为，以加深对两相流在T形管处相分离机理的理解。以空气和水为两相流工作介质，在鼓泡流和环状流条件下，入口主管分别以垂直向上和垂直向下2种方式放置，通过改变气液入口流型和流速，考察了180°弯头上T形管处合力的大小和流型的变化，测定了该处的相分离数据。实验结果表明：入口主管垂直向上时，在鼓泡流条件下，气体主要受液体的浮力作用，液相主要受重力作用，侧支管以气相采出占优，增加气液流速对气相采出不利；而在环状流条件下，液体离心力占主导地位，侧支管以液相采出占优为主，气液两相流速增加对相分离有利；主管垂直向下时，在环状流条件下，以液体向下的离心力和重力占主导地位，侧支管中液相采出占优，增大气体流速或者液体流速，不利于液相在侧支管的采出。利用T形管处的合力大小、入口流型和两相入口动量能有效解释相分离结果的变化规律。%In order to explore the phase split mechanism of two-phase flow at T-junction,a T-junction on a 180°return bend was employed to provide additional forces,such as centrifugal, gravitational and/or buoyant forces when two-phase mixture flows passing through it.The fac-tors,such as the resultant force at the branch direction,inlet momentums of the two phases,and inlet flow patterns at the phase separation were investigated experimentally.Using air and water as two working fluids,the inlet flow patterns for the two-phase flows were set as bubble and annular flows,respectively,and the inlet tube for the bend was placed vertically upward or downward .The phase split data were measured under varying the inlet flow pattern and gas and/or liquid velocities and the flow pattern transition around the bend and at the T-junction was carefully examined.The results show that under the condition of vertically upward inlet tube and the bub-ble flow pattern,the gas is mainly subjected to buoyant force and the liquid to gravitational force.Thus gas takes off preferentially under the condition of the branch.Increasing gas or liquid velocity is harmful to the gas take-off.Whereas at vertically upward inlet tube and annular flow, the liquid is mainly subjected to centrifugal force,and thus the liquid preferentially takes off from the branch.Increasing gas or liquid velocity is beneficial to the liquid take-off.In the case of vertical-ly downward annular flow,liquid is mainly subjected to downward centrifugal and gravitational forces,thus liquid preferentially takes off from the branch.Increasing gas or liquid velocity is harmful to the liquid take-off since the bubbles entrained in the liquid flow in the branch are in-creased and the liquid drops generated by the gas core at the bend are also increased.That which phase preferentially takes off depends mainly upon the resultant force at the branch direction. The phase split phenomena can be explained by analyzing the resultant forces,the flow pattern, and the momentums of the two phases at the T-junction.