횡단류 유동에서 오리피스 형상에 따른 액체제트의 분무특성 = Effect of Orifice Geometry on Spray Characteristics of Liquid Jet into Subsonic Crossflows

다국어 초록 (Multilingual Abstract)

Effects of orifice geometry on the spray characteristics of liquid jet ejecting into subsonic crossflow were experimentally studied. Two circular and four elliptical plain orifices with various ratios of the orifice length to the orifice diameter were used. The diameter of circular orifices and the minor axis of elliptical orifices is 0.5 mm. The ratios of the major axis to the minor axis in elliptical orifices are 2 and 3, respectively. The velocity of subsonic crossflows was approximately 50 m/s. By changing injection pressure from 1 bar to 6 bar, liquid column breakup lengths and liquid column trajectories, which were believed to be important for designing injector and combustor, were measured using a high-speed digital camera (Vision Research, Phantom v9.1). The experiments in circular orifices showed similar results with previous research data which had approximately 8 of the breakup length to the orifice diameter. Regardless of both major axis and minor axis, the experiments in elliptical orifices showed that liquid column trajectories in non-cavitation flow and cavitation flows had a nearly similar trend but liquid column trajectories in hydraulic flip flows had different results. It is thought to be that the surface of the liquid jet in hydraulic flip flows was detached form the inner wall of the orifice exit. When cavitation developed inside the sharp-edged orifice, the liquid jet became more unsteady and turbulent so that hydraulic flip flow and cavitation flow caused the breakup lengths to decrease in both circle and elliptical orifices. However, there was no difference between major axis and minor axis breakup lengths in elliptical orifices because the elliptical liquid jet emerging from the orifice exit tended to become circular. Although the liquid jet cross-sectional shape of the elliptical orifice by the direction of major axis or minor axis to the crossflows was different in the vicinity of the orifice exit, the liquid jet downstream of the exit was considered to have been not significantly affected by the direction of the elliptical orifice.