• Journal of ILASS-Korea
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• v.9 no.4
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• pp.1-8
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• 2004

Breakup characteristics of liquid sheets formed by the impingement of two water jets, such as a breakup length and a breakup wavelength of sheet, were investigated as increasing the injection velocity up to 30m/s and the ambient gas pressure up to 4.0MPa. While round edged orifices formed a laminar sheet which has no waves on the sheet when the injection velocity is low, sharp edged orifices formed a turbulent sheet which has impact waves irrespective of the injection velocity. Thus we compared the differences of breakup characteristics between them. The results showed that the aerodynamic force significantly affects the breakup of laminar sheet when the gas based Weber number is higher than unity, It was also found that the turbulent sheets have three breakup regimes, i.e. expansion regime, wave breakup regime and catastrophic breakup regime according to the gas based Weber number.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.173-179
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• 2004

Breakup characteristics of liquid sheets formed by the impingement of two water jets, such as a breakup length and a breakup wavelength of sheet, were investigated as increasing the injection velocity up to 30m/s and the ambient gas pressure up to 4.0㎫. While round edged orifices formed a laminar sheet which has no waves on the sheet when the injection velocity is low, sharp edged orifices formed a turbulent sheet which has impact waves irrespective of the injection velocity. Thus we compared the differences of breakup characteristics between them. The results showed that the aerodynamic force significantly affects the breakup of laminar sheet when the gas based Weber number is higher than unity. It was also found that the turbulent sheets have three breakup regimes, i.e. expansion regime, wave breakup regime and catastrophic breakup regime according to the gas based Weber number.

• Journal of ILASS-Korea
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• v.11 no.4
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• pp.251-265
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• 2006

To prevent the ozonosphere from being destroyed by Halon, it is an urgent task to find out Halon replacement. As one of the replacements water mist have showed broad applications by its advantages: little pollution to environment (not destroying the ozone layer or bring green house effect), extinguishing fire quickly, consuming a small quantity of water and having little damage to the protected objects. The methods of generating water mist strongly influence fire suppression effectiveness, which determine the cone angle, drop size distribution, flux uniformity, and momentum of the generating spray. The traditional water mist nozzle included pressure jet nozzles, impingement nozzles and twin-fluid nozzles. All of them have more or less disadvantages for fire suppression. Therefore, many research institutes and corporations are taking up with innovations in mist generation. This article provided some recent studies in State Key Laboratory of Fire Science (SKLFS) of University of Science and Technology of China. SKLFS have investigated new methods of generating water mist (i.e. effervescent atomization and ultrasonic atomization). and self developed a series of nozzles and developed advanced DPIVS (Digital Particle Image Velocimetry and Sizing) technique. Characteristics of water mist (the distribution of droplet sizes, flux density, spray dynamics and cone angle) produced by these nozzles were measured under different conditions (work pressure, nozzle geometry, etc.) using LDV/APV and DPTVS systems. A series of experiments were performed to study the fire suppression effectiveness in different fire scenario (different kindsof the fuel, fire size and ventilation conditions). The fire extinguishing mechanisms of water mist was also discussed.