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4공 가솔린 분사기의 2중 분무 사이에서 연료 액적들의 유동특성
김원태,강신재,노병준,Kim, Won-Tae,Kang, Shin-Jae,Rho, Byung-Joon 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.4
This study investigates the flow characteristics of fuel droplets between twin spray for the 4-hole injector used a 4-valve gasoline engine. The injectors for this study were the three types of 4-hole gasoline injector in which orifice diameter was 0.24mm. The spray behavior of twin spray was investigated by means of visualization employed stroboscope. A PDPA system was employed to simultaneously measure the size and velocity of fuel droplets. The 3 dimensional mean velocities. droplet size distributions, SMD and joint probability density function of velocity and droplet size are analyzed at the center of the spray and the center region of twin spray. As a result, the configurations of injector exit such as orifice interval and length of outlet, are very important factors that affect the flow characteristics of fuel droplets at the center region of twin spray.
진동 유동장에서 유동공진에 의한 실린더 후류의 와류 특성 변화
김원태,성재용,유정열,Kim, Won-Tae,Sung, Jae-Yong,Yoo, Jung-Yul 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.11
When vortex shedding is locked-on to a single frequency oscillatory flow, the variations of vortex dynamics are investigated using a time-resolved PIV system. Wake regions of recirculation and vortex formation, dynamic behavior of the shed vortices and the Reynolds stress fields are measured in the wake-transition regime at the Reynolds number 360. In the lock-on state, reduction of the wake region occurs and flow energy distributed downstream moves upstream being concentrated near the cylinder base. To observe the dynamic behavior of the shed vortices, the trajectory of the vortex center extended to the inside of the wake bubble is considered, which describes well the formation and evolution processes. The Reynolds stresses and their contributions to overall force balance on the wake bubble manifest the increase of the drag force by the lock-on.