2유체노즐의 미분무 분사 특성이 복사열 감쇠에 미치는 영향에 대한 연구

Abstract

In this study, the effects of spray characteristics for water mist of twin-fluid nozzles on thermal radiation attenuation was investigated numerically and experimentally. For numerical simulations, the effects of spray characteristics (i.e., water flow rate, droplet size, and spray angle) of water mist on peak and average thermal radiation attenuation were examined preliminarily using fire dynamics simulator (FDS). Then, experiments of spray characteristics of twin-fluid nozzles and their thermal radiation attenuation performance were conducted. As the twin-fluid nozzles, the external and internal mixing types were tested. For the spray characteristics, the supply pressure, droplet size, spray angle, spray width, and flow distribution were measured. The supply pressures of water and air were 1.3－59.6 and 29.8－316.1 kPa, respectively. The SMD (Sauter Mean Diameter) and VMD (Volume Median Diameter, Dv0.5) were 19.9－99.4 and 21.1－107.6 μm, respectively. Through the visualization, the spray angle and spray width were measured. The spray width were approximately 200 and 300－320 mm for spray angles of 20° and 70°, respectively. From the flow distribution measurement, it was found that spray patterns of twin-fluid nozzles were full cone. Finally, the thermal radiation attenuation on water mist of twin-fluid nozzles were measured under various water and air flow rate conditions. Under the present experimental conditions, the thermal radiation attenuation of twin-fluid nozzles were measured to be 6.9－52.4%. As the water flow rate and spray angle increased while the droplet size decreased, the thermal radiation attenuation increased. Based on the experimental data, the separate effects of water flow rate and droplet size on thermal radiation attenuation were investigated. In the present experimental range, the thermal radiation attenuation was proportional to water flow rate to the power of 0.32 and to the power of 0.33 under nearly constant SMD and VMD conditions, respectively. In addition, the thermal radiation attenuation was proportional to SMD to the power of -0.59 and VMD to the power of -0.53 for droplet size under nearly constant water flow rate conditions. Based on these results, the droplet size affected more significantly the change in thermal radiation attenuation than the water flow rate.