| Within the context of lean premixed prevaporised combustion (LPP) which is considered as most promising technology for the next generation low emission combustors for aero 250 VDI-Berichte Nr. 1888, 2005 engines, combustion instabilities are a major issue. One potential excitation mechanism is the interaction of strong air velocity fluctuations with the airblast atomiser. This phenomenon was investigated experimentally at the Institute of Thermal Turbomachinery (ITS) within a parametric study. A duct with a prefilming surface was set up as an abstraction of a prefilming airblast atomiser. The mean air velocity can be adjusted up to 65 m/s, and periodic oscillations can be superimposed by means of a siren up to 570 Hz, which is the typical frequency range of combustion chamber oscillations. The disintegration process of the liquid was investigated by phase resolved LDV (Laser Doppler Velocimetry) and PTV (Particle Tracking Velocimetry). The mean air velocity, the film load, the kinematic viscosity, the surface tension, the pulsation frequency and amplitude were varied, and their effect on droplet size and droplet rate was studied. The most important results are: Particle diameter and rate respond almost proportional to the air velocity fluctuations at low frequencies. At higher frequencies of the excitation, they stay nearly constant. However, the fluctuations of particle diameter and rate increase strongly if the mean air velocity is increased. |
Zerstäubungsverhalten von Airblastdüsen bei oszillierenden Strömungen
| Author: | Müller,A. Hehle,M. Koch,R. Bauer,H.-J. |
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| Source: | VDI-Bericht 1888, 2005, Seite 249-258 22. Deutscher Flammentag, 2005 |
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