Tomographic reconstruction of 2D-OH∗-chemiluminescence distributions in turbulent diffusion flames
A recently developed fast tomographic reconstruction device (Anikin et al. in Appl. Phys. B 100:675, 2010) has been applied to detect 2-D chemiluminescence distributions of OH∗ in reaction zones of a near laminar and a turbulent diffusion flame. A series of single-shot experiments has been carried out in both flames offering cold gas flow velocities of 0.43 m/s and 4 m/s and flame diameters up to 60 mm, respectively.
The emission of OH∗-chemiluminescence originating from the reaction zones of the flame fronts was registered by ten Kepler-telescopes surrounding the object under investigation at different pre-defined angles. The signals emerging from each telescope are collected by a fiber cable consisting of 90 single fibers arranged side by side in a single row, respectively. The signals originating from the ten cables/10×90=900 fibers represent the corresponding Radon transforms. These signals are imaged by a relay-optics onto the photocathode of a single image intensified CCD-camera. The output data of the camera are used for the reconstructions of the 2D-distributions of OH∗-emission using a numerical procedure solving the inverse problem of tomography (Anikin et al. in Appl. Phys. B 100:675, 2010, and references therein). From the experimental results it is shown that the reconstructions obtained at exposure times down to 200 μs reproduce fine structures of the flames with a spatial resolution of ∼1 mm. Therefore, the method is a useful tool for the detailed investigation of turbulent combustion.
The authors gratefully acknowledge Deutsche Forschungsgemeinschaft DFG (Paket-Forschungsantrag: “Chemilumineszenz und Wärmefreisetzung”) for its financial support.
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