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석탄-물 혼합연료(CWM)의 분무 특성(I)
Atomization Characteristics of Coal-Water Mixture Fuel (I)
HWAHAK KONGHAK, February 1996, 34(1), 36-43(8), NONE
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Abstract
레이저 빔의 회절원리를 응용한 분석장치를 사용하여 분무유량이 30-150l/hr이고, 1개의 노즐을 가진 내부혼합식 분무기에서 분산되는 석탄-물 혼합연료(CWM)의 액적 크기를 측정하였고, 노즐에서의 분출 특성을 조사하였다. 2.0kg/cm2이상의 분사압력에서는 임계흐름 현상이 발생하여 공기-물과 공기-CWM의 2상 유체를 분무시킬 경우에 공기의 질량속도와 분사압력 사이에는 직선적인 비례관계가 성립하였고, 공기의 분출계수는 노증의 직경과 CWM의 유량이 증가함에 따라 감소하는 경향을 보였다. 50-120㎛ 범위의 MMD를 갖는 CWM 액적의 크기는 물 액적과 마찬가지로 공기/연료비의 증가에 따라 급격히 감소하다가 어느 수준 이상에서는 공급유량에 관계없이 일정한 값을 유지하였고, SMD는 (1+연료/공기비) 항과 지수적인 비례관계가 성립하였다. 또한 분무기로부터의 축방향 거리에 따라 CWM 액적의 크기는 직선적으로 커지며 obscuration은 감소하였다. CWM 액적의 MMD는 CWM 중에 존재하는 석탄 입자보다 약 20㎛이상 크게 나타나므로 CWM 액적이 한 개의 석탄 입자만이 아닌 여러 개의 석탄 입자들과 물로 구성되어 있음을 확인할 수 있었다.
The atomization and discharge characteristics of coal-water mixture(CWM) fuel at the internal-mixing type atomizer with one exit hole were investigated using Malvern droplet size analyzer which is based upon the laser diffraction method. Test results showed that over the atomizing pressure more than 2.0kgf/cm2, a critical flow phenomenon occurs, and that, consequently, a linearly proportional relationship is established between air mass velocity and absolute pressure in the mixing chamber, and further that the discharge coefficient of air is decreased with the increase of nozzle diameter and CWM mass velocity. The CWM droplet size in the range of 50-120㎛ MMD was sharply decreased with the increase of air/fuel ratio, but was maintained at a fixed value over a certain level, regardles of the CWM feed rate. On the other hand, its SMD was in proportion to the 0.48 power of the term, (1+fuel/air ratio). Also along with the axial distance from the atomizer, CWM droplet size was linearly increased and the obscuration was decreased. Since the MMD of CWM droplets is shown to be larger than that of coal particles in CWM fuel by more than about 20㎛, it was clearly verified that a CWM droplet consists of several coal particles and water, not just one coal particle.
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Meyer P, Chigier N, Atom. Sprays Technol., 2, 261 (1986)
Mullinger PJ, Chigier N, J. Inst. Fuel, 47, 251 (1974)
Graziadio M, Andreussi P, Tognotti L, Zanelli S, Atom. Sprays Technol., 3, 187 (1987)
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Yu TU, Beer JM, Proc.of the 14th Int. Conf. on Coal & Slurry Technology, Clearwater, Fla., April, 191 (1989)
Sato K, Shoji K, Okiura K, Akiyama I, Baba A, Powder Technol., 54, 127 (1988)
Kaneko S, Tokuda K, Noda M, Maruta T, Proc. of the 14th Int. Conf. on Coal & Slurry Technology, Clearwater, Fla., April, 221 (1989)
Meyer PL, Chigier N, Proc. of the 8th Int. Symp. on Coal Slurry Fuels Preparation and Utilization, Orlando, Fla., April, 144 (1986)
Cronin L, Sojka PE, Lefebvre AH, Proc. of the Int. Fuels and Lubricants Meeting and Exposition, Tulsa, Okla, October (1985)
Thambimuthu KV, Whaley H, Lee GK, Proc. of the Int. Symp. on Multi-Phase Flows, Hangzhou, China, August (1987)
Tsai SC, Vu T, Fuel, 66(11), 1596 (1987)
Kang SW, Yu TU, Beer JM, Proc. of the Fossil Fuels Combustion Symp. 1989: 12th Annual Energy-Sources Technology Conference and Exhibition, Houston, Tex., January, 71 (1988)
Smith CF, Sojka PE, Thames JM, Trnas. ASME: J. Eng. for Gas. Turbines and Power, 112, 15 (1990)
Pohl JH, Sepulveda J, Rothfeld LB, Proc. of the 7th Int. Symp. on Coal Slurry Fuels Preparation and utilization, New Orleans, La., May, 357 (1885)
