Research on superheated steam discharge: Leakage process with friction and jet impingement process

The leakage and jet impact characteristics of steam play a crucial role in the safety analysis of nuclear power plant accidents. The prediction model of leakage flow is crucial for Leak-before-break (LBB) analysis. Simultaneously, the study of jet impact process is fundamental for preventing damage to surrounding system equipment. In this paper, two cross-sectional shapes passages are utilized: circular with diameters of 6∼8 mm and elliptical with dimensions of 8*5.26 mm, featuring length-to-diameter ratios of 5.2-105. The study focuses on superheated steam ranging from 4.6-7.5 MPa, measuring leakage rates under various inlet and passage conditions, pressure drops along the passage, and the impact force exerted by the jetted superheated steam on a 400 mm square plate. In experiments, it was found that the pressure drop trend in the flow passage of steam is crucial for predicting the leakage flow rate. The isentropic model was revised based on experimental data, resulting in a model that better fits the experimental results than the original isentropic model and a simpler form compared to Yang's one-dimensional friction model. The study also revealed that the length-to-diameter ratio and related friction effect significantly affect the leakage flow rate and steam jet impingement process. The variation pattern of impingement force coefficient was summarized based on experimental data. Due to the visualization of the experiment, some special phenomena during the experimental process were also recorded.