Cold-flow patterns behind novel rifled bluff-body cones

다국어 초록 (Multilingual Abstract)

Flow momentum behind a conventional nozzle is modulated by four different bluff-body cones — non-rifled, 1-rifled, 2-rifled and 3-rifled cones. This novel rifled-cone swirl generator (RCSG) includes the blockage disc and rifled bluff-body cones. The rifled bluff-bodycone transforms the axial momentum (or the axial velocity) into the angular momentum (or the tangential velocity). The swirling flow isenhanced by increasing the tangential velocity of central jet. In this investigation, the carbon-dioxide (CO2) is utilized as the index gas todetermine the mixing index of RCSGs. Namely, the mixing index between the central CO2-jet and the annular air-jet is increased usingthe RCSGs. The cold-flow patterns behind the rifled bluff-body cones are visualized using the smoke-wire scheme. The cold-flow patternsare categorized as — jet-flow, single-bubble and dual-bubble modes. The jet-flow mode occurs at low ua. Additionally, the jet-flowand single-bubble modes are further classified as — Type-I and type-II sub-modes. The particle-image velocimetry (PIV) measures thecold-flow velocity vectors. The mixing levels of CO2 in the cold-flow modes are detected using a gas concentration analyzer.

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