Abstract: Using a swirl element mounted upstream of the test section，the asymmetry flow patterns such as stratified flow，annular flow were transformed into annular flow with uniform film thickness．Then a single electrical capacitance probe was
applied to measure the film thickness to obtain the mean void fraction．Extensive experiments were carried out in an air－water two phase flow loop．The results show that the capacitance probe output is the function of liquid film thickness and independent of liquid property and temperature．During the wide experimental range the void fraction measured by the single capacitance probe agreed well with that obtained by quick closing valve method．Since the flow pattern is transformed to symmetry type， the gas and liquid distribution along the probe wire can represent the whole section， the shortcoming of traditional probe
measurement method and tomography method is escaped．

Key words: Void fraction , Gas－liquid two phase flow , Capacitance probe , Flow regime

摘要： 在测量管段上游布置旋流装置，将上游分层流、环状流等结构不对称流型整改成液膜厚度均匀一致的环状流，然后采用单丝电容探针测量液膜厚度，从而实现截面平均含气率的实时在线测量。在气液两相流实验环道上进行了实验，结果表明探针输出值只与液膜厚度有关，不受液体性质和温度影响。将快关阀门测量值与电容探针测量结果进行了对比，在宽广的流型范围内，二者符合良好。该方法克服了传统电容探针测量方法测量平均截面含气率时不能保证测量结果的代表性以及层析方法测量系统复杂，需要重建运算的缺点。

关键词: 截面含气率 , 气液两相流 , 电容探针 , 流型