Seedingless measurement of density fluctuations and flow velocity using highspeed holographic interferometry in a swirl-stabilized flame

Environmental protection is today's major issue in the development of turbomachines. Especially, the reduction of pollutant and noise emission of aero engines and ground based gas turbines for power plants is a central task. Therefore, an improved understanding of the occurring complex flow phenomena in such turbomachines is necessary, which requires the investigation of influence and interaction of several process and flow quantities. A simultaneous detection of these quantities is needed in order to analyze the interaction by means of correlation. We present a new approach for simultaneous measurement of density fluctuations and advection velocity inside a turbulent flow without any invasive treatment of the process. Our approach is based on recent developments in the fields of high-speed camera technique and digital processing power, enabling pixel-wise detection of line-of-sight density oscillations and digital signal correlation with a high spatio-temporal resolution of 140μm ² using 79000 pixel at a frame rate of 120kHz, where the velocity measurement is performed by correlation of density vortex movement. A comparison with particle-based velocity detection is made in order to achieve new insights towards the still complicated interpretation of density-based velocity estimation.