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RISS 인기검색어
- 검색키워드
- 저자 : ( Hideaki Yokohata ) (검색결과 2 건)
- 무료
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X-Ray Imaging and Measurement of Cavitation Flow in Fuel Injector Nozzles with Various Geometries
( Rubby Prasetya ),( Takumi Kasahara ),( Kazuya Kotani ),( Takashi Miwa ),( Akira Sou ),( Seoksu Moon ),( Yoshitaka Wada ),( Yoshiharu Ueki ),( Hideaki Yokohata ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-
Studies of in-nozzle cavitation are commonly carried out by conducting visualization experiments with optically accessible nozzle and visible spectrum light sources. However, multiple scattering occurs at the interface of in-nozzle cloud cavitation and discharged liquid jet, which prevents image acquisition of clear cavitation profile and liquid jet. In this study, X-Ray Phase Contrast Imaging (XPCI) is utilized to obtain a clear image of cavitation in several two-dimensional nozzles, as well as the discharged liquid jet of each nozzle. The XPCI was conducted at SPring-8 synchrotron light source. The nozzles used in this study have a width of 1 mm, with ratio of length and width LAV = 4. Upstream geometries of the nozzle are varied, with symmetrical and mini-sac upstream geometries. As a result, we can clearly capture the development of cavitation in the nozzle, from the start of nucleation to the formation of cavitation film in the nozzle. While cavitation film on symmetrical nozzle are relatively stable, mini-sac nozzle produces unstable cavitation film which moves laterally relative to the streamwise direction. The XPCI method also makes it possible to visualize individual bubbles in cloud cavitation, which clarified the collapse and rebound process of cavitation bubble. Finally, visualization of discharged jet from the nozzle under different cavitation regimes prove that wavy structure of the jet’s interface also becomes finer in accordance with cavitation growth in the nozzle.
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String Cavitation and 3D PIV in Multi-Hole Injector
( Hiroaki Nakano ),( Rubby Prasetya ),( Shinichiro Deguchi ),( Takashi Miwa ),( Akira Sou ),( Keiya Nishida ),( Akira Nakashima ),( Yoshitaka Wada ),( Yoshiharu Ueki ),( Hideaki Yokohata ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-
It is essential to control fuel spray characteristics in diesel engines for cleaning up exhaust gases and improving combustion efficiency. Turbulent cavitating flow in fuel injectors plays an important role in fuel spray characteristics. String cavitation may occur in a sac and nozzles of multi-hole fuel injectors, which strongly affects fuel spray characteristics. It should be caused by the vortex flow in the sac. However, the occurrence mechanism of string cavitation has not been clarified yet. The purpose of this study is to clarify the mechanism and condition of string cavitation occurrence by conducting a high-speed visualization experiment in a transparent injector of cavitation and a discharged liquid jet at various needle lifts and flow rates. We also measure the three-dimensional flow field in the sac by 3D PIV. The transparent acrylic multi-hole mini-sac nozzle is designed to visualize cavitation. Sodium iodide aqueous solutions or diesel oil with α-methyl naphthalene is used as a working fluid to avoid the refraction at the surface of the acrylic walls and these liquids. As a result, it is found that at low needle lift string cavitation often occurs which is surrounded by a vortical flow in the sac and increases the discharged hollow-cone liquid jet angle, while at high needle lift thin and short string cavitation may occur, which does not strongly influence discharged liquid jet and spray. The probability of the string cavitation appearance under various conditions as well as the transient motion of string cavitation and liquid jet is also clarified.
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