The development of a Doppler Global Veocimetry (DGV) system is described. An argon ion laser has been modified to suit the requirements of DGV. An etalon with high precision tilting control has been mounted in the laser cavity. The backward mirror of the laser cavity has been mounted on a piezotranslator for controlling the laser cavity length. Two iodine cells have been designed and manufactured: one with a bead of iodine in the cell volume, the other with a limited amount of iodine. The iodine absorption line of both cells has been calibrated with good repeatibility. The laser has been stabilized in frequency, so that operations during a measurement session in the lab are simplified. The capabilities of DGV measurements have been tested in two jets, at low and at high speeds. Velocity fluctuations of the jet could be followed, in spite of the highly noisy signals. The first steps towards three velocity component measurements with a single camera in a difficult environment such as the geometry of a turbomchinery cascade have been made. Imaging two views of a target on the same camera sensor is discussed, along with the spatial and luminosity calibration required.

This study presents the results of an experimental study that investigates the effects of uniform/waveform tip injection along the camberline on the total pressure loss characteristics downstream of a row of Low Pressure Turbine (LPT) blades. The experiments are performed in a low speed cascade facility. This injection technique involves spanwise jets at the tip that are issued from a series of holes along the camber line normal to the freestream flow direction. The injection mass flow rate from each hole is individually controlled using computer driven solenoid valves and therefore the flow injection geometrical pattern at the tip can be adjusted to any desired waveform shape, and can be uniform as well as waveform along the camber. Measurements involve Kiel probe traverses for different injection scenarios 0.5 axial chords downstream of the blades. Results show that, instead of performing uniform mass injection along the camberline, by selecting an appropriate waveform injection pattern one can reduce the total loss levels of the blade, including the tip leakage loss as well as the wake losses.

This thesis presents the results of an experimental study that investigates the effects of steady vortex generator jets (VGJs) integrated to a low pressure turbine blade to control the laminar separation bubble occurring on the suction surface of the blade at low Reynolds numbers. The injection technique involves jets issued from the holes located near the suction peak of the test blade which is in the middle of a five-blade low speed linear cascade facility. Three injection cases are tested with different blowing ratio values ranging from low to high. Surface pressure and particle image velocimetry (PIV) measurements are performed. The results show that steady VGJ is effective in eliminating the laminar separation bubble. Also it is observed that to have fully developed attached boundary layer, blowing ratio should be chosen accordingly since a very thin separation zone still exists at low blowing ratios.

The Aim of this Diploma thesis is the measurement on turbine cascade. The first part is focused on measurement of the flow characteristics of the turbine cascade using a three–hole pressure probe. The second part includes the blade profile pressure measurement. Both measurements are performed both experimentally and by computer simulation in Ansys and the results are compared. Part of the work is also file containining the computer simulation, which was carried out in CFX program.

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The development of a Doppler Global Veocimetry (DGV) system is described. An argon ion laser has been modified to suit the requirements of DGV. An etalon with high precision tilting control has been mounted in the laser cavity. The backward mirror of the laser cavity has been mounted on a piezotranslator for controlling the laser cavity length. Two iodine cells have been designed and manufactured: one with a bead of iodine in the cell volume, the other with a limited amount of iodine. The iodine absorption line of both cells has been calibrated with good repeatibility. The laser has been stabilized in frequency, so that operations during a measurement session in the lab are simplified. The capabilities of DGV measurements have been tested in two jets, at low and at high speeds. Velocity fluctuations of the jet could be followed, in spite of the highly noisy signals. The first steps towards three velocity component measurements with a single camera in a difficult environment such as the geometry of a turbomchinery cascade have been made. Imaging two views of a target on the same camera sensor is discussed, along with the spatial and luminosity calibration required. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished