Study on ultrasonic attenuation characteristics in air-droplet two-phase flow

Abstract

The wetness of exhaust steam in nuclear power plant steam turbine is an important index to evaluate the safety and economy of nuclear power plant and the ultrasonic attenuation method has the advantages of quick response and non-contact in the steam wetness measurement of nuclear power plant steam turbine. The saturated steam-droplet medium and the air-droplet medium have many similar thermal fluid characteristics, in order to simplify the experiment, the air-droplet two-phase flow is used to simulate the wet steam discharged from steam turbine of nuclear power plant, and the ultrasonic attenuation coefficient in the air-droplet two-phase flow is measured. The correlation between wetness and ultrasonic attenuation coefficient was studied by calibrating the wetness of the air-droplet two-phase flow and measuring the ultrasonic attenuation coefficient under different wetness conditions. Meanwhile, the static characteristics of ultrasonic transducer and the influence of flow velocity on attenuation coefficient are studied experimentally. According to the results of experiment and numerical calculation, the ultrasonic attenuation coefficient is very sensitive to the change of wetness. The ultrasonic attenuation coefficient and wetness has a good linear relationship in the wetness range (0–16%), the ultrasonic attenuation method is appropriate for the wetness measurement of turbine steam exhaust and has high precision when the droplet size is stable.