Experimental study on spray characteristics of pressure-swirl nozzles in pressurizer

Spraying system in the pressurizer of Pressurized Water Reactor (PWR) power plant system is of great importance for system pressure control. An experimental study on the spray characteristics, including mass flow rate, spray flux distribution, spray cone angle and drop size spectrum, was conducted. A testing loop with nine swirling nozzles was established for the study. In order to measure the spray cone angle and drop size spectrum, two original devices including a spray droplet collector and a photographic chamber were designed and employed. The former was used to collect the spray droplet along the cross-section diameter, and the latter was made to isolate and measure the targeted spray droplet. Based on the experimental data, the curves of flow rate and spray cone angle versus nozzle pressure drop were obtained. Several typical spray flux distributions were derived and the results indicated that the flux distribution changes significantly with even small pressure changes. Thus, it was proposed that instability of the spray flux distribution should be considered in the pressurizer. Based on the spray drop pictures recorded by the high speed camera, Probability Density Function (PDF) of the drop size was obtained and compared with four 'standard' empirical distributions. It was found that the Nukiyama-Tanasawa distribution provides a better fit to the experimental PDF of the spray drop size. The present work introduces the experimental methodology and results of spray behaviour of the nozzle in pressurizer. The work is expected to be helpful for the optimization design of spraying systems.