泡状流中含气率和气泡尺寸分布的超声非接触测量方法

A Method for Ultrasonic Non-contact Measuring the Gas Content and Dimension Distribution of Bubbles in a Bubble Flow

搭建了一套超声法非接触测量装置,用于循环系统中气液两相泡状流含气率和气泡尺寸在线测量。针对截面为20 mm×3 mm垂直矩形窄通道出口,在常压、入口温度313 K的过冷条件,利用UAS(超声衰减谱法)对水流动沸腾引起的垂直上升气液两相泡状流含气率和气泡尺寸分布进行测量,分析了加热功率和质量流量对泡状流含气率和气泡尺寸及其分布的影响。实验结果表明:质量流量一定时,随着加热功率升高,气泡中位径D50增大,尺寸分布增宽,气液两相流含气率增大;在工况大致相当(可通过出口温度T2和出口绝对压力p2判断)的条件下,随着质量流量的增大,气泡中位径D50减小,尺寸分布变窄,含气率减小。将超声法所测含气率与气液分离法所测含气率比较,最大相对偏差为4.5%,说明实验测量结果基本可靠。

Set up was a set of supersonic non-contact measurement device for performing an on-line measurement of the gas content and bubble dimensions of a gas-liquid two-phase bubble flow in a circulation system. For a vertical rectangu-lar narrow channel outlet with a cross section of 20 mm × 3 mm,under the condition of the supercooling state in which the pressure was normal and the inlet temperature was 313 K,the ultrasonic attenuation spectrum method was used to measure the gas content and dimension distribution of bubbles in a vertical rising gas-liquid two-phase bubble flow arisen from the boiling of a water flow and analyze the influence of the heating power and the mass flow rate on the gas content,bubble dimensions and their distribution of a bubble flow. The test results show that when the mass flow rate is constant,with an increase of the heating power,the medium diameter of the bubbles D50 will increase,the distribution of dimensions will broaden and the gas content of the gas-liquid two-phase flow will also increase. Under the condition of the operating conditions being roughly equivalent( which can be judged from the outlet temperature T2 and the outlet absolute pressure P2),with an increase of the mass flow rate,the medium diameter of the bubbles D50 will decrease,the distribution of dimensions will narrow and the gas content will decrease. When the gas content measured by using the ultrasonic method is compared with that measured by using the gas-liquid separation method,the maximal relative deviation reaches 4. 5%,indicating that the measurement results obtained from the test are basically reliable.