• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.2
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• pp.213-223
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• 1997

Premixed flame is better than diffusion flame to accomplish a high loading combustion. Since the turbulent characteristics of unburned mixture has a great influence on the flame structure, it is general that many researchers realize a high loading combustion with strengthening turbulent intensity of unburned mixture. Because turbulent premixed flame reacts efficiently on the condition of distributed reaction region, we made high turbulent premixed flame in the doubled impingement field. We investigated turbulent characteristics of unburned mixture with increasing shear force and visualized flames with direct and Schlieren photographs. And the combustion characteristics of flame was elucidated by instantaneous temperature measurement with a thermocouple, by ion currents with a micro electrostatic probe, by radical luminescence intensity and local equivalence ratio. Extremely strong turbulent of small scale is generated by impingement of mixture, and turbulent intensity of unburned mixture increased with the mean velocity. As a result of direct photographs, visible region of flame became longer due to increasing central direction flux. But as strengthed turbulent intensity, visible region of flame turned to shorter and reaction occurred efficiently. As strengthened turbulent intensity of mixture with increasing flux of central direction, maximum fluctuating temperature region moved to radial direction and fluctuation of temperature became lower. The reason is influx of central direction which caused flame zone to move toward radial direction, to maintain flame zone stable and to make flame scale smaller.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.3
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• pp.1040-1049
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• 1996

The high loading combustion is accomplished by making the turbulent intensity strong and the scale small in the premixed combustor. The Da-mkoler number, which is decreased by short turbulent characteristic time or by long chemical reaction time, can make the distributed reaction flame. So we developed a doubled jet burner for high loading combustion. The doubled jet burner was designed to make the scale of the flame small by the effect of impingement and increasing shear stress with doubled jet. We investigated the turbulence characteristics of unburned mixture and visualized several flames with the typical schlieren photography. Then we studied the influence of several factors that related the scale of flame. Consequently, the doubled jet burner can make the eddy very small. And we can obtain the detail information of the flame scale through ADSF(the Average Distance between Successive Fringes) in the micro- schlieren photography. The ADSF is not a exact flame scale, but it has qualitative trend with increasing turbulent intensity. The ADSF is diminished remarkably with increasing turbulent intensity. The reason is that strong turbulent intensity makes the flame zone thick and flamelets numerous. We can confirm this fact by the signal analysis of ion currents.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.7
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• pp.2337-2346
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• 1996

One of the most useful method for increasing combustion loading of premixed flame is to strengthen the turbulent intensity of unburned mixture. It produces an important information to a design of efficient combustion equipment that analysing microstructure of strong turbulence premixed flame. The flame structure and characteristics are depend on the turbulence of unburned mixture. Therefore, to strengthen the turbulent intensity of unburned mixture make flame scale small and accomplish efficient combustion. We measured the velocity of local flame front movements, local eddy radius and local reaction zone thickness quantitatively with increasing turbulent intensity of unburned mixture. We researched the microstructure of flame using ion currents that react sensitively in the reaction zone. Consequently, the velocity of local flame front movements is depend on the velocity of unburned mixture and local eddy scale is to be small with increasing turbulent intensity. But there is no change in local reaction zone thickness with turbulence.