Planar imaging techniques in turbomachinery - Current status and future trends

Abstract

While the development and application of planar velocimetry methods are finding an increased range of applications throughout the engineering field involving fluid mechanics, the successful application of these advanced methods remain a challenge in many of the real-world applications. The validation of numerical tools used in turbomachinery in particular requires highly spatially (ideally temporally) resolved data of oftentimes secondary flow phenomena in environments that are representative of real facilities (e.g. combination of high pressure, velocity and temperature with and without reaction). The successful implementation of modern imaging diagnostics in turbomachinery test facilities requires adequate handling of a wide variety of problems, ranging from optical access, choice of proper seeding material, image acqusition strategy, post-processing, etc. Even under seemingly ideal conditions measurements are not always successful and advanced image processing methods such as multigrid PIV algorithms with image-deformation is necessary to extract usable data. The presentation highlights several challenging applications of particle image velocimetry (PIV), Doppler global velocimetry (DGV) and OH-chemiluminescence in large combustor facilities, highly loaded compressors as well as an automotive application. Driven by the frequently high facility operational costs, the future will see the application of several imaging measurement techniques in parallel thus permitting even further insights in the underlying flow physics (e.g. simultaneous measurements of temperature, concentration and flow field).