Full-field laser vibrometry for combustion diagnostics

Full-field measurements of transient flow behavior in harsh environments are a demanding task in industrial development, e.g. regarding the reduction of pollutant and sound emissions of jet engines by means of lean combustion. This lean combustion behavior is achieved by using swirl-stabilized flames. Such processes can exhibit instabilities based on flame oscillations due to thermo-acoustic fluctuations of pressure and heat release rate, which potentially result in failure of the device. Therefore, the task of this project is the characterization of the combustion by non-invasive measurements of the heat release rate inside the flame and the flow velocity at the combustor outlet.

Simultaneous, seedingless, optical measurements of these quantities can be achieved using multiple laser-vibrometers and signal correlation. The measurement is based on the linear relation between the heat release rate and the change of the refractive index, which can be detected integral along the laser beam. Using multiple laser-vibrometers it is furthermore possible to measure the flow velocity due to the phase delay between two vibrometer signals and the known distance between the measurement positions. However, simultaneous field measurements have to be accomplished in order to detect the transient spatio-temporal flow behavior of the combustion and to enable tomographic reconstruction of the instable process. In order to overcome these limitations, a high-speed camera-based laser-vibrometer (CLIV) is designed for non-invasive seedingless measurements of the flow velocity and heat release rate inside premixed flames. The system offers high data rates up to 2.5 GHz.

Staff: J. Gürtler, R. Kuschmierz

Period: 02/2016 – 01/2019

Partner: TU Graz, Prof. Woisetschläger; TU München, Prof. Sattelmayer

 J. Gürtler, A. Ramos, J. Woisetschläger, R. Kuschmierz, F. Greiffenhagen J. Czarske, “Simultaneous measurements of velocity and density of transient flows using high-speed camera technique”, SPIE Photonics Europe, 22.-26.04.2018, Strasbourg, France

F. Greiffenhagen, J. Woisetschläger, J. Gürtler, H. Scholz, R. Kuschmierz, J. Czarske, „Comparison of flame transfer functions measured with locally resolved full-field-vibrometry and OH*-chemiluminescence”, ASME Turbo Expo 2018: Turbine Technical Conference and Exposition, 11.06.-15.06.2018, Lillestrøm, Norway