Development of a Transient Hydrogen Jet in a High-Swirl Constant Volume Chamber
When hydrogen is used in large size diesel engines, the direct-injection combustion regime appears most desirable for its low fuel consumption properties. In applying hydrogen as an alternative to diesel fuel, the behavior of hydrogen jets in swirling air needs to be clarified to provide design procedures for engine designers. This paper is intended to investigate the development of transient hydrogen jets in high-swirl flow fields achieved in a constant volume vessel by means of precise measurement of injection amount and imaging of developing jets. The result showed that when the pressure ratio of injection pressure to the back pressure is higher than the critical pressure ratio, the injection amount remained constant due to the flow choking at the nozzle exit, while jet tip penetration varied depending on the pressure ratio. The variation of jet penetration was elucidated qualitatively by the quasi-steady jet theory. The behavior of transient hydrogen jets in swirling air fields was imaged successfully at a swirl speed of 12000 rpm by a newly developed imaging technique denoted as “ Oil mist scattering technique” The result obtained showed that the motion of hydrogen jets is significantly interacted by the swirl flow depending on the swirl intensity and the ambient air density. It was also revealed that the swirl can prohibit hydrogen jets from contacting the chamber walls, which is effective in reducing the heat loss from burning hydrogen jets to the chamber walls.
KeywordsCombustion Vortex Quartz Diesel Mist
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