| Project/Area Number |
10355010
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| Research Category |
Grant-in-Aid for Scientific Research (A).
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Thermal engineering
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KASAGI Nobuhide School of Engineering, The University of Tokyo Professor, 大学院・工学系研究科, 教授 (80107531)
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| Co-Investigator(Kenkyū-buntansha) |
SUZUKI Yuji School of Engineering, The University of Tokyo Associate Professor, 大学院・工学系研究科, 助教授 (80222066)
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| Project Period (FY) |
1998 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥31,800,000 (Direct Cost: ¥31,800,000)
Fiscal Year 2000: ¥5,100,000 (Direct Cost: ¥5,100,000)
Fiscal Year 1999: ¥8,500,000 (Direct Cost: ¥8,500,000)
Fiscal Year 1998: ¥18,200,000 (Direct Cost: ¥18,200,000)
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| Keywords | Jet Flow / Active Control / Axisymmetric Jet / Coaxial Jet / Mixing Control / Flap Actuator / MEMS Technology / 燃焼制御 / 混合制御 / レーザー誘起蛍光法 / レーザードップラー流速計 / 流れの可視化 / 力学モデル / 流体反力 / 分岐噴流 |
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| Research Abstract |
In pursuing a possibility of producing various jet flow modes with a single nozzle, axisymmetric and coaxial jets is perturbed by a row of miniature electromagnetic flap actuators equipped on the nozzle exit lip. The electromagnetic flap actuators are fabricated by photolithography so as to be independently driven by control signals supplied. The spatio-temporal flow structures of the controlled jet at a relatively low Reynolds number are studied through flow visualization using planer laser-induced fluorescence (PLIF) and quantitative velocity measurement.
For axisymmetric free jet, it is demonstrated that various disturbances introduced in the jet shear layer by the flap actuators can modify the process of formation and evolution of large-scale vortical structures. In particular, when each half cluster of the flap actuators are driven 180 degree out of phase, the jet bifurcates clearly into two branches. The most effective Strouhal number of flapping, is nearly constant and 0.25. In this control mode, the vortex rings successively produced turn away from the jet axis by the mutual interaction between alternatively inclined vortices.
For confined coaxial water jet, the roll-up of the shear layer between the outer jet and the ambient fluid is synchronized with the artificial disturbances generated by the flaps, and the evolution of large scale vortical structures are modified significantly. Strong reverse flow is also observed near the jet exit. Almost the same setup is applied to coaxial air jet in order to evaluate the present control scheme in flow mixing and combustion. Mixing between the inner and outer fluid was enhanced most effectively by the axisymmetric flap motion at St=0.9, which is close to the preferred mode frequency. Preliminary attempt was also made for active combustion control. A lifted flame was stabilized by the axisymmetric flap motion at the optimum flapping frequency for mixing.
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