가진된 부착화염에서 거대와동의 거동
Behavior of the Coherent Structure on the Attached Forced Flame
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An experimental study was conducted to investigate the effects of forcing amplitude on the flow structure near the nozzle exit of forced jet diffusion flames. The jet was excited up to the blowout occurrence by a considerable large amplitude with a periodic velocity fluctuation at the tube resonating frequency. In the attached flame regime, we disclosed the very interesting result newly that adding of a moderate forcing amplitude caused the jet flame to become longer in spite of being forced. Particular attention is focused on the turnabout mechanism of vortex roll-up around the elongated flame, which has not been reported previously, and on the inner coherent structure of the forced jet in the attached flame regime. From the velocity and flow visualization results, it was ascertained that the surrounding air due to the occurrence of negative velocity parts was suck into the fuel nozzle. To aid in understanding the rotating phenomenon of coherent structure, we present a schematic diagram of the turnabout mechanism of vortex roll-up. The mechanism of vortex turnabout phenomenon can be easily understood by considering the positive and negative velocity amplitudes about the instantaneous velocity of the forcing flow, as shown in this diagram.
Abstract
An experimental study was conducted to investigate the effects of forcing amplitude on the flow structure near the nozzle exit of forced jet diffusion flames. The jet was excited up to the blowout occurrence by a considerable large amplitude with a periodic velocity fluctuation at the tube resonating frequency. In the attached flame regime, we disclosed the very interesting result newly that adding of a moderate forcing amplitude caused the jet flame to become longer in spite of being forced. Particular attention is focused on the turnabout mechanism of vortex roll-up around the elongated flame, which has not been reported previously, and on the inner coherent structure of the forced jet in the attached flame regime. From the velocity and flow visualization results, it was ascertained that the surrounding air due to the occurrence of negative velocity parts was suck into the fuel nozzle. To aid in understanding the rotating phenomenon of coherent structure, we present a schematic diagram of the turnabout mechanism of vortex roll-up. The mechanism of vortex turnabout phenomenon can be easily understood by considering the positive and negative velocity amplitudes about the instantaneous velocity of the forcing flow, as shown in this diagram.
참고문헌 (7)
- W. S. Anthony, "Visualization of the structure of a pulsed methane-air diffusion flame", Phys. Fluids, 28(8), pp.2317~2330 (1985)
- Y. C. Chao, "Behavior of the lifted flame under acoustic excitation", 24th Sym. on Combustion, pp.333~340 (1994)
- T. K. Kim, "Mixing mechanism near the nozzle exit in a tone excited nonpremixed jet flame", Combustion Science and Technology, 89, pp.83~100 (1993)
- S. K. Oh, "A visualization study on the effect of forcing amplitude of tone excited isothermal jets and jet diffusion flames", Int. J. of Energy and Resource, 22, pp.343~354 (1998)
- K. M. Lee, "A visual investigation of nonpremixed flame behavior under acoustic excitation", ’01 Spring Annual Conference, KSME, pp.871~877 (2001)
- F. Baillot, "Physical mechanisms of a lifted nonpremixed flame stabilized in an acoustic field", Combustion Science and Technology, 174(8), pp.73~98 (2002)
- D. Demare, "Acoustic enhancement of combustion in lifted nonpremixed jet flames", Combustion and Flame, 139, pp.312~328 (2004)